Clostridial Diseases of Animals E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 605

Veröffentlichungsjahr: 2016

Beschreibung

Clostridial Diseases of Animals is the first book to focus on clostridial diseases in domestic and wild animals, offering a comprehensive reference on these common diseases.

• Provides a single resource for all aspects of clostridial diseases
• Presents current, comprehensive information with a focus on clinical relevance
• Covers each disease in depth, including etiology, epidemiology, clinics, gross pathology, histopathology, diagnostics, diagnostic criteria, prophylaxis, control, and treatment
• Written by the world-leading experts in the field of clostridial diseases in animals
• Offers photographs and summary tables to support the concepts discussed in the text and aid in recognition

Leseprobe

Table of Contents

Cover

Title Page

List of Contributors

Preface

SECTION 1: The Pathogenic Clostridia

1 Taxonomic Relationships among the Clostridia

Bibliography

2 General Physiological and Virulence Properties of the Pathogenic Clostridia

Introduction

Anaerobic metabolism

Major clostridial diseases

The onset of clostridial infections

The key role of protein toxins in clostridial disease

The key role of spores in the epidemiology of clostridial disease

Conclusions

Bibliography

3 Brief Description of Animal Pathogenic Clostridia

Bibliography

SECTION 2: Toxins Produced by the Pathogenic Clostridia

4 Toxins of Histotoxic Clostridia:

Clostridium chauvoei, Clostridium septicum, Clostridium novyi

, and 

Clostridium sordellii

Introduction

A – Intracellularly active toxins from histotoxic clostridia

B – Membrane-damaging toxins from histotoxic clostridia

Phospholipases

Bibliography

5 Toxins of 

Clostridium perfringens

Introduction

A – Major toxins

B – Other toxins

Bibliography

6 Toxins of

Clostridium difficile

Introduction

Toxins A and B

C. difficile

ADP-ribosylating toxin (CDT)

Hypervirulence of 

C. difficile

and its potential mechanisms

Immunotherapy of

C. difficile

infections

Conclusion

Bibliography

7

Clostridium botulinum

and

Clostridium tetani

neurotoxins

Introduction

Clostridia

producing botulinum neurotoxins

Clostridium tetani

Susceptibility of animal species to clostridial neurotoxins

Structure of clostridial neurotoxins

Mode of action of clostridial neurotoxins

Concluding remarks

Bibliography

SECTION 3: Clostridial Infections of the Gastrointestinal System

8 Diseases produced by

Clostridium perfringens

type A in mammalian species

Introduction

Yellow lamb disease

Other enteric diseases produced by

Clostridium perfringens

type A in mammals

Clostridium perfringens

beta 2 toxin-associated gastrointestinal disease

Bibliography

9 NetF-associated necrotizing enteritis of foals and canine hemorrhagic gastroenteritis

Introduction

Etiology

Epidemiology and clinical findings

Gross changes

Microscopic changes

Diagnosis

Bibliography

10 Necrotic enteritis of poultry

Introduction

Epidemiology

Etiology and pathogenesis

Host response

Predisposing factors

Clinical signs

Gross changes

Microscopic changes

Prophylaxis

Diagnosis

Bibliography

11 Infections by

Clostridium perfringens

type B

Introduction

Etiology

Clinical signs

Gross changes

Microscopic changes

Diagnosis

Prevention and treatment

Bibliography

12 Diseases produced by

Clostridium perfringens

type C

Diseases of mammalian species

Necrotic enteritis of poultry

Bibliography

13 Diseases Produced by

Clostridium perfringens

type D

Introduction

Etiology

Epidemiology and pathogenesis

Clinical signs

Gross changes

Microscopic changes

Diagnosis

Prophylaxis and treatment

Bibliography

14 Infections by

Clostridium perfringens

type E

Introduction

Etiology

Pathogenesis

Animal disease

Diagnosis

Bibliography

15 Diseases produced by

Clostridium difficile

Introduction

Etiology

General epidemiology and pathogenesis of

Clostridium difficile

infection

Animal diseases produced by

Clostridium difficile

Bibliography

16 Disease caused by

Clostridium colinum

: Ulcerative enteritis of poultry and other Avian species

Introduction

Etiology

Epidemiology

Clinical signs

Gross changes

Microscopic changes

Diagnosis

Bibliography

17 Clostridial Abomasitis

Introduction

Braxy (

Clostridium septicum

)

Other agents of clostridial abomasitis

Bibliography

18 Diseases produced by

Clostridium spiroforme

Introduction

Etiology

Pathogenesis

Epidemiology

Clinical signs

Gross changes

Microscopic changes

Diagnosis

Treatment and prophylaxis

Bibliography

SECTION 4: Clostridial Histotoxic Infections

19 Blackleg

Introduction

Etiology

Epidemiology

Pathogenesis

Clinical signs

Gross changes

Microscopic changes

Diagnosis

Prevention and treatment

Bibliography

20 Gas Gangrene (Malignant Edema)

Introduction

Etiology

Epidemiology

Pathogenesis

Clinical signs

Gross changes

Microscopic changes

Diagnosis

Treatment, control, and prophylaxis

Bibliography

21 Gangrenous Dermatitis in Poultry

Introduction

Etiology

Epidemiology

Pathogenesis

Clinical signs

Gross changes

Microscopic changes

Diagnosis

Control, treatment, and prophylaxis

Bibliography

22 Bacillary Hemoglobinuria

Introduction

Etiology

Epidemiology

Pathogenesis

Clinical signs

Gross changes

Microscopic changes

Diagnosis

Treatment and control

Bibliography

23 Infectious Necrotic Hepatitis

Introduction

Etiology

Pathogenesis

Epidemiology

Clinical signs

Gross changes

Microscopic changes

Diagnosis

Treatment and control

Bibliography

24 Tyzzer’s Disease

Introduction

Etiology

Epidemiology

Pathogenesis

Clinical signs

Clinico-pathologic findings

Gross changes

Microscopic changes

Diagnosis

Treatment

Prevention and control

Bibliography

SECTION 5: Clostridial Neurotoxic Infections

25 Tetanus

Introduction

Epidemiology

Clinical signs

Gross and microscopic changes

Diagnosis

Prophylaxis, treatment, and control

Bibliography

26 Botulism

Introduction

Etiology

Pathogenesis

Occurrence and prevalence of animal botulism

Epidemiology

Clinical signs

Gross and microscopic changes

Prophylaxis and control

Treatment

Diagnosis

Conclusion

Bibliography

27 Diseases Caused by Other Clostridia Producing Neurotoxins

Introduction

Neurologic disease associated with

Clostridium perfringens

type D

Botulism caused by

Clostridium baratii

and 

Clostridium butyricum

Bibliography

Index

End User License Agreement

List of Tables

Chapter 03

Table 3.1 Summary of the main characteristics of the major clostridial pathogens of animals

Chapter 04

Table 4.1 Main toxins and other virulence factors of histotoxic clostridia

Table 4.2 Toxins of

Clostridium novyi

and

Clostridium haemolyticum

Table 4.3 Substrate specificity of

Clostridium sordellii

and

Clostridium novyi

large toxins (Genth

et al

., 2014)

Chapter 05

Table 5.1 Toxin typing of

Clostridium perfringens

Table 5.2 Summary of major

C. perfringens

toxin properties

Chapter 07

Table 7.1 Groups and main properties of botulinum neurotoxin producing Clostridia,

botulinum

neurotoxin types and subtypes according to (Peck 2006, Peck 2009, Peck

et al

. 2011, Mazuet

et al

. 2012, Raphael

et al

. 2012, Hill and Smith 2013, Diao

et al

. 2014, Raphael

et al

. 2014, Weedmark

et al

. 2014, Kull

et al

. 2015, Mazuet

et al

. 2015)

Table 7.2 Genomic localization of botulinum loci in

botulinum

neurotoxin-producing Clostridia according to (Sakaguchi

et al

. 2005, Hill

et al

. 2009, Skarin

et al

. 2011, Hill and Smith 2013) (Franciosa

et al

. 2009, Brüggemann

et al

. 2011, Dover

et al

. 2013, Zhang

et al

. 2013, Hosomi

et al

. 2014, Raphael et al. 2014)

Table 7.3 Toxicity of botulinum toxin types according to the animal species and injected intraperitoneally or as indicated. The toxicity titers are expressed as intra-peritoneal mouse lethal doses (MLD) per kg of body weight, according to (Smith 1977) and

a

from (Wright 1955)

Table 7.4 Susceptibility to crude preparations of BoNT types according to intraperitoneal or intravenous administration versus oral administration. The BoNT toxic activity is expressed as intra-peritoneal mouse lethal doses per kg of body weight (Smith 1977)

Table 7.5 Lethal amounts of tetanus neurotoxin

Chapter 12

Table 12.1 Most common spontaneous and experimental diseases associated with

C. perfringens

type C

Chapter 17

Table 17.1 Factors that may predispose to abomasal bloat and abomasitis in young calves, lambs, and goat kids, and that may need to be investigated and corrected in order to control disease. Predisposing factors may be multiple and additive

Chapter 25

Table 25.1 Sensitivity of animal species to tetanus toxin. Relative minimum lethal doses compared to guinea pig lethal dose for various animal species

Chapter 26

Table 26.1 Occurrence of BoNT types in animal botulism

List of Illustrations

Chapter 01

Figure 1.1 Phylogenetic tree displaying the relationship between

Clostridium

species.

Escherichia coli

from the

Enterobacteriaceae

family was used as an out group. The phylogenetic tree was constructed using the “One Click” mode with default settings in the Phylogeny.fr platform (http://phylogeny.lirmm.fr/phylo_cgi/index.cgi). The numbers above the branches are tree support values generated by PhyML using the aLRT statistical test.

Chapter 04

Figure 4.1 Domain organization and structure of the catalytic domain of large clostridial glucosylating toxins (LCGTs). TcsL is shown as a representative member of this toxin family. LCGTs contain C-terminal repeats involved in the recognition of the cell surface receptor and a central hydrophobic domain mediating the translocation of the N-terminal catalytic domain into the cytosol through the endosome membrane. The catalytic domain is cleaved from the rest of the molecule by an autocleavage process involving the cysteine protease domain which contains the active site DHC. The catalytic domain structure shows a compact core of β-sheet surrounded by numerous α-helices with central catalytic motif (DxD) and an extension of four N-terminal helices.

Figure 4.2 General model of β-pore-forming toxin (β-PFT) mechanism of action. The secreted soluble monomers recognize specific cell-surface receptor(s), assemble, oligomerize, unfold amphipathic β-hairpin(s), which form a pre-pore and then insert into the membrane. Reprinted with permission from Popoff (2014)

Anaerobe

,

30:

220–238.

Figure 4.3 Structure of representative clostridial pore-forming toxins:

C. perfringens

perfringolysin (PFO),

C. perfringens

epsilon toxin (ETX),

C. septicum

alpha toxin (ATX, structure modeling based on sequence relatedness with epsilon toxin), and

C. perfringens

NetB. Note that PFO contains two transmembrane hairpins (TMH) shown in their helical conformation, and that ETX, ATX, and NetB contain only one TMH. Domains in green are the receptor-binding domains.

Figure 4.4 Main steps in the pathogenesis of clostridial gangrenes. Reprinted (slightly modified) with permission from Popoff (2014)

Anaerobe

,

30:

220–238.

Figure 4.5 Aerolysin monomer and schematic representation of the pore formation according to Degiacomi

et al

. (2013). Binding receptor sites are localized in domains 1 and 2. The transmembrane hairpin in domain D3 is in red. Upon binding to their receptor, monomers heptamerize and form a pre-pore showing an inverted mushroom shape, of which domains 1 and 2 constitute the cap. Then the stalk, which is comprised of domains 3 and 4, rotates and completely collapses, and the β-barrel extends in the opposite orientation to that of the stalk in the pre-pore conformation. Two monomers (red and blue) are shown in the heptameric structure. Clostridial β-PFTs including

C. perfringens

epsilon toxin and

C. septicum

alpha toxin are supposed to use a similar mechanism of pore formation. Reprinted (slightly modified) with permission from Popoff (2014)

Anaerobe

,

30:

220–238.

Chapter 05

Figure 5.1 Activities of various

Clostridium perfringens

toxins on host cells. See text for a detailed explanation of their specific mechanism of action.

Chapter 06

Figure 6.1 Genetic organization of the PALoc toxin region of

C. difficile

showing the

tcdA

and

tcdB

genes, and accessory

tcd

genes.

tcdC

and

tcdR

are genes involved in regulating toxin production, and

tcdE

encodes a holin protein involved in toxin secretion. Sequence differences in the

tcdA

and

tcdB

genes are used in PCR-based “toxinotyping”, of which over 30 types are recognized. These differences can have profound effects on toxin production and potency.

Figure 6.2 Schematic of the functional domain structure of TcdA and TcdB. The four major domains have N-terminal glucosyltransferase activity (GT), autocatalytic cysteine protease activity (CPD), central translocation (TMD), and C-terminal receptor binding (C) (see text).

Chapter 08

Figure 8.1 Sheep with yellow lamb disease showing severe, diffuse icterus.

Figure 8.2 Liver of a lamb with yellow lamb disease showing centrilobular necrosis. HE, 100x.

Figure 8.3 Kidney of a lamb with yellow lamb disease showing tubular degeneration and multiple protein (hemoglobin) droplets in the cytoplasm of tubular epithelial cells. HE, 400x. Courtesy of F. Giannitti.

Figure 8.4 Kidney of a lamb with yellow lamb disease stained with Okajima stain to demonstrate hemoglobin (stained bright orange) in the cytoplasm of tubular epithelial cells. Okajima, 600x. Courtesy of F. Giannitti.

Chapter 09

Figure 9.1 Phylogenetic analysis of representative members of the leukocidin/hemolysin superfamily. The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. Toxins that were used include: alpha-hemolysin of

C. botulinum

, hemolysin II of

B. cereus

, alpha-hemolysin of

S. aureus

, putative CctA of

C. chauvoei,

and beta toxin of

C. perfringens

.

Figure 9.2 Jejunum of a 7-day-old foal showing thickening of the wall and serosal congestion associated with

netF

-positive type A

C. perfringens

. Courtesy of M. Spinato.

Figure 9.3 Jejunum of a 7-day-old foal showing diffuse necrotizing enteritis associated with

netF

-positive type A

C. perfringens

. Courtesy of M. Spinato.

Chapter 10

Figure 10.1 Serosal view of the intestinal tract of a chicken with acute necrotic enteritis, which demonstrates the predilection of the disease to develop in the small intestine, particularly the jejunum.

Figure 10.2 Mucosal view of the jejunum in a chicken with acute necrotic enteritis, which shows the thin intestinal wall, hyperemia, and diffuse mucosal necrosis typical of severe cases.

Figure 10.3 Mucosal view of the jejunum in a chicken with chronic necrotic enteritis, which shows multifocal ulceration.

Figure 10.4 Microscopic view of the jejunum in a chicken with acute necrotic enteritis, showing the sharp line of demarcation between viable and necrotic tissue characterized by large numbers of inflammatory cells at the edge of the viable tissue (arrows). HE, 200x.

Chapter 11

Figure 11.1 Diffuse hemorrhagic enteritis in a calf with

Clostridium perfringens

type B enterotoxemia.

Chapter 12

Figure 12.1

Clostridium perfringens

type C necrotic enteritis in a piglet; observe perianal hemorrhage.

Figure 12.2

Clostridium perfringens

type C necrotic enteritis in a piglet; observe dark red (hemorrhagic) and emphysematous small intestinal loops.

Figure 12.3

Clostridium perfringens

type C necrotic enteritis in a foal. Transmural lesions extending through the jejunal wall are observed as patches of hemorrhage in the intestinal serosa.

Figure 12.4

Clostridium perfringens

type C necrotic enteritis in a foal. An affected portion of ileum (top) is diffusely dark red and contains frankly hemorrhagic fluid, whereas the unaffected duodenum (bottom) contains light brown, normal fluid.

Figure 12.5 Experimental

Clostridium perfringens

type C necrotic enteritis in a goat. The lumen of the jejunum contains a small amount of hemorrhagic fluid and yellow, fibrinous exudate admixed with necrotic debris (pseudomembrane).

Figure 12.6

Clostridium perfringens

type C necrotic enteritis in a foal. The mucosa of the small intestine is dull, orange/green and multifocally ulcerated.

Figure 12.7

Clostridium perfringens

type C necrotic enteritis in a foal. The mucosa of the small intestine is diffusely necrotic, and the submucosa is expanded by hemorrhage and emphysema; the hemorrhage extends into the muscular and serosal layers. HE, 200x.

Figure 12.8

Clostridium perfringens

type C necrotic enteritis in a calf. There is necrosis of the epithelium at the tip of the small intestinal villi and the mucosal surface is overlaid by a thin pseudomembrane containing abundant bacteria. Observe diffuse hemorrhage within the lamina propria. HE, 100x.

Figure 12.9

Clostridium perfringens

type C necrotic enteritis in a foal. Abundant Gram-positive bacilli morphologically compatible with

Clostridium

spp. on the mucosal surface of the small intestine. Gram, 400x.

Chapter 13

Figure 13.1 Pulmonary edema in a sheep with type D enterotoxemia. The interlobar and interlobular septae are diffusely expanded and filled by a clear fluid (edema). Reprinted with permission from Uzal

et al

. (2008)

20

: 253–265.

Figure 13.2 Pulmonary edema in a sheep with type D enterotoxemia. A large amount of stable froth is oozing mainly from the airways.

Figure 13.3 Hydropericardium in a sheep with type D enterotoxemia. There is abundant, clotted yellowish fluid in the pericardial sac.

Figure 13.4 Herniation of the cerebellar vermis through the foramen magnum (“cerebellar coning”) in a sheep with type D enterotoxemia.

Figure 13.5 Focal symmetrical encephalomalacia in a sheep with type D enterotoxemia; both corpus striatum are affected.

Figure 13.6 Focal symmetrical encephalomalacia affecting cerebellar peduncles of a sheep with type D enterotoxemia.

Figure 13.7 Colitis in a goat with type D enterotoxemia. The colonic serosa shows diffuse hyperemia, congestion, and edema.

Figure 13.8 Colitis in a goat with type D enterotoxemia. The colonic mucosa shows focally extensive hemorrhage and an incipient pseudomembrane.

Figure 13.9 Perivascular proteinaceous edema (microangiopathy) in the brain of a sheep with type D enterotoxemia. Small arteries and capillaries are surrounded by abundant eosinophilic fluid in the Virchow–Robins space. HE, 200x.

Figure 13.10 Sub-gross view of white matter (internal capsule) of a sheep with type D enterotoxemia showing multifocal necrosis, characterized by rarefaction of the neuropil. HE, 40x.

Figure 13.11 Higher magnification of Figure 13.10. The white matter shows severe dilation of myelin sheaths, neuronal death, gliosis, swollen axons (spheroids), and the presence of vacuolated macrophages (gitter cells). HE, 200x.

Figure 13.12 Transmission electron micrograph of the cerebellar granular layer of a sheep with type D enterotoxemia. The capillary endothelium exposed to ETX is markedly attenuated and electron dense, with nuclear pyknosis. Perivascular astrocytic foot processes are severely swollen. A normal capillary is shown in the inset. Uranyl acetate and lead citrate stain, 3750x.

Figure 13.13 Colitis in a goat with type D enterotoxemia. The superficial colonic mucosa shows diffuse necrosis and suppurative effusion. HE, 100x.

Chapter 15

Figure 15.1

Clostridium difficile

-associated disease; adult horse. The large colon and cecum show diffuse gray to bluish discoloration of the serosal surface due to mucosal and submucosal congestion and/or hemorrhage.

Figure 15.2

Clostridium difficile

-associated disease; foal. Abundant red (hemorrhagic) fluid in the small colon.

Figure 15.3

Clostridium difficile

-associated disease; adult horse. Abundant green fluid in the colon.

Figure 15.4

Clostridium difficile

-associated disease; adult horse. The wall of the colon shows marked thickening by clear, gelatinous, submucosal edema.

Figure 15.5

Clostridium difficile

-associated disease; adult horse. Markedly edematous colon with dull, opaque, brownish to greenish discoloration of the mucosa.

Figure 15.6

Clostridium difficile

-associated disease; foal. Affected segment of small intestine shows multifocal to coalescing mucosal ulcers and a tan to light orange pseudomembrane.

Figure 15.7

Clostridium difficile

-associated disease; adult horse. Histology of the large colon shows diffuse necrosis of the mucosa, with total loss of the epithelial lining, marked submucosal edema and congestion. HE, 20x.

Figure 15.8

Clostridium difficile

-associated disease; adult horse. Histology of the colon depicting a “volcano lesion” characterized by mucosal ulceration at the tip of the crypts from which fibrin and neutrophils exude. HE, 200x.

Figure 15.9

Clostridium difficile

-associated disease; piglet. Marked mesocolonic edema, segmental dilation and yellow discoloration of the spiral colon.

Figure 15.10

Clostridium difficile

-associated disease; piglet. Histology of the spiral colon shows marked mesocolonic edema, congestion of mesocolonic vasculature, and multifocal mucosal necrosis with pseudomembrane formation. HE, 20x.

Figure 15.11 The comparative distribution of

C. difficile

-associated lesions in the intestinal tract of different animal species.

Figure 15.12

Clostridium difficile

-associated disease; rabbit. Diffuse, severe, hemorrhagic ileitis with transmural necrotizing lesions.

Figure 15.13

Clostridium difficile

-associated disease; hamster. Diffuse, severe, necrotizing typhlitis is a characteristic lesion of CDAD in hamsters.

Chapter 16

Figure 16.1 Jejunum of a quail with ulcerative enteritis. Numerous multifocal hemorrhagic ulcers are present. In the left side of the picture, the less hemorrhagic ulcers have a characteristic pale yellow halo around the necrotic ulcerated tissue.

Figure 16.2 Jejunum of a quail with ulcerative enteritis. Multifocal transmural necrosis is typical of the more chronic disease.

Figure 16.3 Liver of a quail with ulcerative enteritis. Multifocal areas of variably sized pale necrosis are visible on the liver surface. As the disease progresses, large, colorfully yellow areas of necrosis can be found throughout the parenchyma.

Figure 16.4 Jejunum of a quail with ulcerative enteritis. Extensive ulceration of the mucosa, which has sloughed its necrotic surface, forming a pseudomembrane. HE, 100x.

Figure 16.5 Jejunum of a quail with ulcerative enteritis. A large focal area of inflammation and necrosis is present in the mucosa and extends into the submucosa and muscularis; this lesion will develop into the transmural necrosis shown in Figure 16.2. HE, 100x.

Figure 16.6 Jejunum of a quail with ulcerative enteritis showing many large colonies of bacteria. HE, 200x.

Figure 16.7 Liver of a quail with ulcerative enteritis. Hepatic lesion showing a large area of coagulative necrosis, with minimal inflammatory response. HE, 200x.

Chapter 17

Figure 17.1 Abomasum of a sheep with braxy. The abomasum shows generalized edema and patches of marked congestion. Large gas bubbles are visible under the mucosa. Several multifocal ulcers are also present.

Figure 17.2 Abomasum of a lamb with braxy. There is marked mucosal necrosis, edema, emphysema, and congestion of the mucosa and submucosa. A rim of heavy neutrophilic infiltration surrounds necrotic areas. HE, 40x.

Figure 17.3 Venn diagram of current understanding of the microbiological complexities of abomasal bloat and abomasitis in young calves, lambs, and goat kids. It helps to see the circles as dynamic and changing, depending in part on the environmental and host predisposing factors. The figure also indicates our current inadequate understanding of the pathogenesis (and control) of the problem(s).

Figure 17.4 Serosal view of the abomasum of a calf with abomasitis showing marked gaseous distension, congestion, and hemorrhage.

Figure 17.5 Mucosa of the abomasum of a calf with abomasitis showing edematous, hemorrhagic, and emphysematous folds. The abomasal content was foul smelling.

Figure 17.6 Serosal view of the abomasum of a lamb with abomasitis showing severe bloat, congestion, and hemorrhage.

Figure 17.7 Abomasal mucosa of a lamb with abomasitis showing markedly edematous and congested folds, with multifocal hemorrhage and ulceration.

Figure 17.8 Abomasum of a calf with abomasitis. There is marked mucosal necrosis, mucosal and submucosal hemorrhage, edema, and emphysema. HE, 40x.

Figure 17.9 Higher magnification of Figure 17.8, showing large clusters of Gram-positive rods with typical

C. perfringens

morphology in the mucosa and submucosa of the abomasum. HE, 400x.

Figure 17.10 Abomasum of a lamb with abomasal bloat, showing bacterial clusters typical of

Sarcina

spp. on the mucosal surface. HE, 400x.

Chapter 18

Figure 18.1 Gram stain of a cecal smear of a rabbit with

Clostridium spiroforme

infection

,

showing the typical spiral chains of cells.

Figure 18.2 Cecum of a rabbit with presumptive

Clostridium spiroforme

infection showing severe serosal edema, congestion, and hemorrhage.

Figure 18.3 Cecum of a rabbit with presumptive

Clostridium spiroforme

infection showing hemorrhagic content.

Chapter 19

Figure 19.1 Skeletal muscle of a steer with blackleg. The tissue shows multifocal hemorrhage, necrosis, and many small cavities due to the presence of gas bubbles.

Figure 19.2 Heart of a steer with blackleg. The myocardium shows several dark areas of hemorrhage and necrosis.

Figure 19.3 Heart of a steer with blackleg showing fibrinous pericarditis. The pericardial sac has been opened and the epicardium is visible.

Figure 19.4 Skeletal muscle of a cow with blackleg. The muscular fibers are hypereosinophilic and show loss of cross striations; hypercontraction bands, vacuolation, and fragmentation are also seen. HE, 250x.

Figure 19.5 Skeletal muscle of a cow with blackleg showing thrombosis. The interstitium surrounding affected blood vessels shows neutrophilic infiltration and edema. HE, 250x.

Figure 19.6 Skeletal muscle of a steer with blackleg. A large number of Gram-positive rods are present in the interstitium. Gram, 600x.

Figure 19.7 Skeletal muscle of a steer with blackleg showing diffuse hemorrhage and multifocal vacuoles caused by accumulation of gas in the tissues. HE, 40x.

Figure 19.8 Skeletal muscle of a steer with blackleg showing large numbers of rods positively stained for

Clostridium chauvoei

. Streptavidine peroxidase, 600x.

Chapter 20

Figure 20.1 Gas gangrene produced by

Clostridium novyi

in a 2-month-old calf following castration. Note the severe subcutaneous edema, emphysema, and hemorrhage.

Figure 20.2 Gas gangrene caused by

Clostridium septicum

in a 10-month-old male Rottweiler dog. Note edema, hemorrhage, and dark red discoloration of affected muscle.

Figure 20.3 Gas gangrene caused by

Clostridium septicum

in a steer after intramuscular injection with a contaminated needle. Note the dark red discoloration of affected muscles indicating hemorrhage and necrosis.

Figure 20.4 Omphalophlebitis caused by

Clostridium septicum

in a newborn lamb. Note the internal umbilical remnant showing edema, swelling, and hemorrhage.

Figure 20.5 Gangrenous mastitis in a ewe due to

Clostridium novyi

. Note the clear line of demarcation between the skin overlying the gangrenous mammary gland and the surrounding normal-looking skin.

Staphylococcus aureus

was also isolated from the mammary gland in this case.

Figure 20.6 Gangrenous mastitis in a ewe due to

Clostridium novyi

(same animal as in Figure 20.5). Note severe subcutaneous edema, which is also affecting the adjacent mammary gland.

Figure 20.7 Chronic gas gangrene caused by

Clostridium septicum, Clostridium chauvoei

, and

Clostridium sordellii

in a pig. The port of entry in this case was not determined.

Figure 20.8 Subcutaneous tissue of a cow with malignant edema by

Clostridium septicum

. There is severe edema distending the connective tissue, and large clusters of intralesional bacilli.

Figure 20.9 Direct fluorescent antibody test for

Clostridium septicum

on a smear of muscle from a calf with malignant edema. 400x.

Figure 20.10 Direct fluorescent antibody test for

Clostridium septicum

on formalin-fixed, paraffin-embedded, subcutaneous tissue of a cow with malignant edema. 200x.

Figure 20.11 Immunohistochemistry (streptavidin-biotin peroxidase) for

Clostridium septicum

in the fascia of a sheep with malignant edema. 400x.

Chapter 21

Figure 21.1 Gangrenous dermatitis in a 14-day-old turkey showing wet and dark skin.

Figure 21.2 Gangrenous dermatitis in a 38-day-old broiler chicken showing subcutaneous accumulation of serosanguinous fluid with gas bubbles (emphysema).

Figure 21.3 Dark discoloration due to hemorrhage in the muscle of a turkey with gangrenous dermatitis.

Figure 21.4 Serofibrinous exudate and emphysema in the subcutis of a broiler chicken with gangrenous dermatitis. HE, 40x.

Figure 21.5 Large numbers of Gram-positive rods in the subcutaneous serofibrinous exudate of a broiler chicken with gangrenous dermatitis. HE, 400x.

Figure 21.6 Skeletal muscle of a chicken with gangrenous dermatitis, showing degeneration, necrosis, and mild inflammatory infiltrate. HE, 200x.

Figure 21.7 Gangrenous dermatitis produced by

Clostridium septicum

, but complicated with

Staphylococcus aureus

infection in a chicken. There is necrosis of the epidermis with ulceration, and inflammatory infiltrate in the dermis and subcutis. HE, 100x.

Figure 21.8 Immunohistochemistry (streptavidin-biotin peroxidase) for

Clostridium septicum

in the subcutaneous tissue of a broiler chicken with gangrenous dermatitis.

Chapter 22

Figure 22.1 External surface of the liver of a cow with bacillary hemoglobinuria. A large, single focus of necrosis surrounded by a hyperemic rim is affecting the liver. A layer of fibrin is present over the area of necrosis.

Figure 22.2 Section of the liver of a cow with bacillary hemoglobinuria. A well-delimited, roughly conical, and pale focus of necrosis is observed.

Figure 22.3 Kidney of a cow with bacillary hemoglobinuria. The renal cortex and medulla are diffusely dark, suggesting hemoglobinuric nephrosis. Jaundice in adipose tissue is also evident.

Figure 22.4 Liver of a cow with bacillary hemoglobinuria. An area of coagulative necrosis (right) is delimited by a narrow band of dense, leukocytic infiltrate, mainly composed of degenerated neutrophils. A more normal-looking area of liver parenchyma is observed on the left. HE, 40x.

Figure 22.5 Liver of a cow with bacillary hemoglobinuria. Large numbers of rods are observed in the sinusoids between necrotic hepatocytes, at the periphery of the area of necrosis, and close to the band of leukocytic infiltrate. HE, 400x.

Figure 22.6 Liver of a cow with bacillary hemoglobinuria. Portal area showing bile duct hyperplasia, fibrosis, and mixed inflammatory infiltrate consistent with

Fasciola hepatica

infestation. HE, 200x.

Figure 22.7 Kidney of a cow with bacillary hemoglobinuria. The glomerular space and tubular lumen are distended by an eosinophilic substance consistent with hemoglobin. Small globules of the same substance are also present in the lumen of the tubular epithelium, which shows evidence of degeneration and occasionally necrosis. HE, 200x.

Chapter 23

Figure 23.1 Liver of a sheep with infectious necrotic hepatitis. Multiple well-delimited and pale foci of necrosis are evident.

Chapter 24

Figure 24.1 Liver of a foal with Tyzzer’s disease. The liver is markedly enlarged, with multifocal to coalescing white foci.

Figure 24.2 Cross-section of the liver of a foal with Tyzzer’s disease. Multiple pale foci of necrosis are dispersed throughout the parenchyma.

Figure 24.3 Foal with Tyzzer’s disease showing diffuse icterus.

Figure 24.4 Liver of a foal with Tyzzer’s disease. Multiple random foci of necrosis are observed. HE, 40x.

Figure 24.5 Higher magnification of Figure 24.4. A focus of coagulative necrosis with a large number of viable and degenerated neutrophils admixed with eosinophilic cell debris is observed. HE, 100x.

Figure 24.6 Liver of a foal with Tyzzer’s disease. Multiple filamentous bacteria are seen in the cytoplasm of a hepatocyte. HE, 400x.

Figure 24.7 Liver of a rabbit with multiple intracytoplasmic filamentous bacteria. Steiner stain, 400x.

Figure 24.8 Colon from a cat with Tyzzer’s disease. The lamina propria is expanded by numerous mononuclear cells, and the crypts are dilated with necrotic debris. HE, 600x.

Figure 24.9 Small intestine of a rabbit with Tyzzer’s disease. Numerous filamentous bacilli are seen in the cytoplasm of enterocytes. Cross-sections of those bacilli are also seen. HE, 100x.

Figure 24.10 Transmission electron micrograph of the colon of a cat with Tyzzer’s disease. A crypt enterocyte contains numerous transverse, longitudinal, and oblique sections of both vegetative cells and spores. Uranyl acetate and lead citrate stain, 6000x.

Chapter 25

Figure 25.1 Scrotum of a lamb that developed tetanus approximately two weeks after castration with a rubber ring.

Figure 25.2 Tetanus in a steer that developed a few weeks after castration. Observe generalized rigidity of the body.

Figure 25.3 Third eyelid prolapse in a steer with tetanus.

Figure 25.4 Lamb with tetanus. The animal is in lateral recumbency and shows stiffness of the limbs.

Figure 25.5

Clostridium tetani

. Terminal spores are observed in several rods, giving the typical drumstick appearance to the organism. Unstained phase contrast microscopy, 600x.

Chapter 26

Figure 26.1 Turkey with typical signs of botulism: paralysis of legs, wings, and neck.

Figure 26.2 Cow suffering from botulism with signs of constipation. .

Figure 26.3 Tongue paralysis in a cow with botulism. .

Figure 26.4 General botulism diagnostic workflow. Based on suspicion of botulism symptoms, diagnosis confirmation is achieved by detecting the botulism toxins with

in vivo

or

in vitro

assays prior to or following an enrichment step. A positive result for botulism toxins directly from suspected samples confirms the diagnosis. Detection of the neurotoxin or of a toxin-producing clostridium after an enrichment step strongly emphasizes the botulism diagnosis but should be interpreted within the epidemiological context, as it indicates that the organism might be naturally present in the environment.

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Clostridial Diseases of Animals

Francisco A. Uzal DVM, FRVC, MSc, PhD, Dipl. ACVP

Professor of Veterinary Diagnostic PathologyCalifornia Animal Health and Food Safety LaboratorySan Bernardino BranchSchool of Veterinary MedicineUniversity of California DavisSan Bernardino, California, USA

J. Glenn Songer MA, PhD, Fellow AAM, Dipl. ACVM

Professor (Emeritus) of Veterinary Science and MicrobiologyCollege of AgricultureThe University of Arizona in TucsonTucson, Arizona, USA

John F. Prescott MA, VetMB, PhD, FCAHS

University Professor EmeritusDepartment of PathobiologyUniversity of GuelphGuelph, Ontario, Canada

Michel R. Popoff DVM, PhD

Anaerobic Bacteria and ToxinsPasteur InstituteParis, France

This edition first published 2016 © 2016 by John Wiley & Sons, Inc

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Library of Congress Cataloging-in-Publication Data

Names: Uzal, Francisco Alejandro, 1958– , editor. | Prescott, John F. (John Francis), 1949– , editor. |  Songer, J. Glenn (Joseph Glenn), 1950– , editor. | Popoff, Michel R., editor.Title: Clostridial diseases of animals / [edited by] Francisco Alejandro Uzal, John Francis Prescott,  J. Glenn Songer, Michel Robert Popoff.Description: Ames, Iowa : John Wiley & Sons, Inc., 2016. | Includes bibliographical references and index.Identifiers: LCCN 2015047741 | ISBN 9781118728406 (cloth)Subjects: LCSH: Clostridium diseases in animals. | Clostridium. | MESH: Clostridium Infections–veterinary |  Clostridium–pathogenicityClassification: LCC SF809.C6 C56 2016 | NLM SF 809.C6 | DDC 636.089/6931–dc23 LC record available at http://lccn.loc.gov/2015047741

A catalogue record for this book is available from the British Library.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.

Cover image: © Lower left courtesy of A. de Lahunta, middle left courtesy of T. Van Dreumel and upper left courtesy of E. Paredes.

For Sock, Rosy, and Ariel, with love.

—Francisco Uzal

For Cathy Prescott, with love.

—John Prescott

For Pam, Ashley, and Alistair, with love.

—Glenn Songer

For Fabienne, Vincent, Sébastien, and Benjamin, with love.

—Michel Popoff

List of Contributors

Camila C. Abreu, DVM, MScVeterinary Pathology LaboratoryFederal University of Lavras,Lavras, Minas Gerais, BrazilFrancisco R. Carvallo Chaigneau, DVM, DSc, Dipl. ACVPCalifornia Animal Health and Food Safety LaboratorySan Bernardino BranchSchool of Veterinary MedicineUniversity of California, DavisSan Bernardino, CA, USAKerry K. Cooper, PhDDepartment of BiologyCalifornia State University, NorthridgeNorthridge, CA, USASantiago S. Diab, DVM, Dipl. ACVPCalifornia Animal Health and Food Safety LaboratoryDavis BranchSchool of Veterinary MedicineUniversity of California, DavisDavis, CA, USAFernando Dutra Quintela, DVM, MSc, MSc, FRVCSDILAVE "Miguel C Rubino"Eastern Regional LaboratoryTreinta y Tres, UruguayPatrick Fach, PhDANSESFood Safety Laboratory, IdentyPath PlatformMaisons-Alfort, Cedex, FranceJohn W. Finnie, BVSc, MSc, PhD, FRCVSSouth Australia Pathology Hanson Institute Center for Neurologic Diseases and School of Veterinary ScienceUniversity of AdelaideAdelaide, South Australia, AustraliaRussell S. Fraser, DVM, MScDepartment of PathobiologyUniversity of GuelphGuelph, Ontario, CanadaKarina C. Fresneda, DVMCalifornia Animal Health and Food Safety LaboratorySan Bernardino BranchSchool of Veterinary MedicineUniversity of California, DavisSan Bernardino, CA, USAJorge P. García, DVMDepartment of Large Animal Surgical and Medical ClinicsVeterinary SchoolNational University of the Center of Buenos Aires ProvinceTandil, Buenos Aires, ArgentinaFederico Giannitti, DVMVeterinary Diagnostic LaboratoryCollege of Veterinary MedicineUniversity of MinnesotaSaint Paul, MN, USAandNational Institute of Agricultural Research La EstanzuelaColonia, UruguayIman Mehdizadeh Gohari, DVM, MScDepartment of PathobiologyUniversity of GuelphGuelph, Ontario, CanadaAshley E. HarmonHarmon CreativeSeattle, WA, USAM. Kevin Keel, DVM, PhD Dipl. ACVPDepartment of Pathology, Microbiology and ImmunologySchool of Veterinary MedicineUniversity of California, DavisDavis, CA, USACaroline Le Maréchal, PhDANSESPloufragan-Plouzané LaboratoryHygiene and Quality of Avian and Pig Products UnitPloufragan, FranceFrancisco C. F. Lobato, DVM, MSc, PhDVeterinary SchoolFederal University of MinasBelo Horizonte, BrazilJanet I. MacInnes, BSc, PhDDepartment of PathobiologyUniversity of GuelphGuelphOntario, CanadaBruce A. McClane, BSc, PhDDepartment of Microbiology and Molecular GeneticsUniversity of Pittsburgh School of MedicinePittsburgh, PA, USAPaula I. Menzies, DVM, MPVM, Dipl. ECSRHMDepartment of Population MedicineOntario Veterinary CollegeUniversity of GuelphGuelph, Ontario, CanadaMauricio Navarro, DVM, MScDepartment of Pathology, Microbiology and ImmunologySchool of Veterinary MedicineUniversity of California, DavisDavis, CA, USACarlos A. Oliveira Jr., DMV, MScVeterinary SchoolFederal University of MinasBelo Horizonte, BrazilValeria R. Parreira, BSc, MSc, PhDDepartment of PathobiologyUniversity of GuelphGuelph, Ontario, CanadaMichel R. Popoff, DVM, PhDAnaerobic Bacteria and ToxinsPasteur InstituteParis, FranceJohn F. Prescott, MA, Vet MB, PhD, FCAHSDepartment of PathobiologyOntario Veterinary CollegeUniversity of GuelphGuelph, Ontario, CanadaJulian I. Rood BSc(Hons), PhD, FASM, FAAMInfection and Immunity Program, Biomedicine Discovery InstituteandDepartment of MicrobiologyMonash UniversityClayton, Victoria, AustraliaH. L. Shivaprasad, BVSc, MS, PhD, Dipl. ACPVCalifornia Animal Health and Food Safety LaboratoryTulare BranchSchool of Veterinary MedicineUniversity of California, DavisTulare, CA, USARodrigo O. S. Silva, DVM, MSc, PhDVeterinary SchoolFederal University of Minas GeraisBelo Horizonte, BrazilJ. Glenn Songer, MA, PhD, Fellow AAM, Dipl. ACVMProfessor (Emeritus) of Veterinary Science and MicrobiologyCollege of AgricultureThe University of Arizona in TucsonTucson, Arizona, USAJames R. Theoret, PhDDepartment of Biological SciencesCollege of Southern NevadaLas Vegas, NV, USAFrancisco A. Uzal, DVM, FRVC, MSc, PhD, Dipl. ACVPCalifornia Animal Health and Food Safety LaboratorySan Bernardino BranchSchool of Veterinary MedicineUniversity of California, DavisSan Bernardino, CA, USACédric Woudstra, MScANSESFood Safety LaboratoryMaisons-Alfort, Cedex, FranceAnson K.K. Wu, BSc, MScDepartment of PathobiologyUniversity of GuelphGuelph, Ontario, Canada

Preface

Over the past 20 years or so there has been an explosion of research on clostridia. A significant part of this interest in the field is a response to the Clostridium difficile human pandemic and several other human diseases, including enterotoxigenic Clostridium perfringens food poisoning. However, there have also been important advances in all fields of clostridia, including those associated with animal diseases.

Advances in the animal field are many, and it is not our intention to mention them all in this preface, since they are the subject of this book. Amongst the most significant achievements of the past few years is the discovery of new toxins and other virulence factors, including NetB, NetF, and several others, and the fulfillment of molecular Koch postulates for several of these toxins. For instance, we know now beyond any reasonable doubt that C. perfringens epsilon toxin is responsible for type D enterotoxemia of ruminants, while the beta toxin of this microorganism is responsible for necrotizing enteritis of neonates of several animal species. The synergism between CPE and CPB of C. perfringens type C has also been demonstrated and it is possible that such interactions exist for other C. perfringens toxins and/or for toxins of other clostridial species.

No English-language textbook on clostridial diseases of animals has been published since Max Sterne and Irene Batty’s classic Pathogenic Clostridia, last edited in 1975. Because understanding of clostridia and clostridial diseases has progressed so much since then, this book provides a much-needed, up-to-date reference on clostridial diseases of animals. The book was written mostly with the veterinary community in mind, including clinicians, diagnosticians, pathologists, microbiologists, and, in sum, everybody that has to deal with clostridial diseases of animals. However, we hope that all professionals and scientists working with clostridia will find something of value in these pages. An effort was made to include good-quality photographs of gross and microscopic images, which we hope will be helpful in terms of the recognition of disease patterns.

There are many things we still do not know about clostridia and clostridial diseases. In veterinary medicine the frequent lack of agreement on diagnostic criteria for several of the major clostridial diseases is particularly worrisome. For instance, what is the diagnostic value of isolating a particular clostridial species from the intestine of an animal in which this microorganism is normally found? How can we reliably define the diagnostic value of highly sensitive real-time PCR done on fecal or intestinal material and not, through this technique, over-diagnose particular diseases? The discovery of new virulence factors, such as the recently discovered NetF, which may be found in clostridia isolated from sick, but not healthy, animals, may help to resolve at least part of this dilemma. A subject we hope will receive more attention in the future is diagnostic tests for clostridial diseases, including rapid tests.

We will be pleased to receive readers’ comments as well as suggestions for improvement in any future editions of this book.

Francisco A. UzalJ. Glenn SongerJohn F. PrescottMichel R. Popoff

SECTION 1The Pathogenic Clostridia

1Taxonomic Relationships among the Clostridia

John F. Prescott, Janet I. MacInnes, and Anson K. K. Wu

Clostridia are prokaryotic bacteria belonging to the phylum Firmicutes, the Gram-positive (mostly), low G + C bacteria that currently contains three classes, “Bacilli”, “Clostridia”, and “Erysipelotrichia”. The class “Clostridia” contains the order Clostridiales, within which the family Clostridiaceae contains 13 genera distributed among three paraphyletic clusters and a fourth clade represented by a single genus. The first clostridial cluster contains the genus Clostridium and four other genera. The genus Clostridium has been extensively restructured, with many species moved to other genera, but it remains phylogenetically heterogenous. The genus currently contains 204 validly described species (http://www.bacterio.net), of which approximately half are genuinely Clostridium.

The main pathogenic clostridial species, Clostridium botulinum, Clostridium chauvoei, Clostridium haemolyticum, Clostridium novyi, Clostridium perfringens, Clostridium septicum, and Clostridium tetani, clearly belong to the genus Clostridium because they share common ancestry with the type species Clostridium butyricum. These species belong to the phylogenetic group described by Collins et al. (1994) as “cluster I”, and are Clostridium sensu stricto. The taxonomy of C. botulinum is unique since it is currently defined as C. botulinum only by the ability to produce one or more botulinum toxins; however, strains that can do this belong to at least four Clostridium species. This situation is complex and taxonomically confusing, since strains of other species, such as C. butyricum which may produce botulinum toxin and cause human botulism, have been given their own species designation (that is, not C. botulinum). To compound the inconsistency around species designation in the taxonomy of Clostridium, C. novyi type A and Clostridium haemolyticum belong to the same genospecies as C. botulinum group III (the agents of animal botulism). Many Clostridium species which do not belong to this genus sensu stricto, as defined by the type species C. butyricum, are distributed among the genera of Clostridiaceae but are described as “incertae sedis”. These fall into different phylogenetic clusters throughout the low G +C Gram-positive phylum, and belong to distinct 16S rRNA gene-sequence-based clusters that represent different genera and different families. For example, Clostridium difficile and Clostridium sordellii fall into cluster XIa (“Peptostreptococcaceae”), Clostridium colinum falls into cluster XIVb (“Lachnospiraceae”), and Clostridium spiroforme falls into cluster XVIII, a new family. Figure 1.1 shows these relationships based on 16S rRNA sequences.

Figure 1.1 Phylogenetic tree displaying the relationship between Clostridium species. Escherichia coli from the Enterobacteriaceae family was used as an out group. The phylogenetic tree was constructed using the “One Click” mode with default settings in the Phylogeny.fr platform (http://phylogeny.lirmm.fr/phylo_cgi/index.cgi). The numbers above the branches are tree support values generated by PhyML using the aLRT statistical test.

Interestingly, the genus Sarcina falls within the genus Clostridium sensu stricto, and indeed should have taxonomic preference as the genus name. This taxonomic precedence, as well as the genus attribution of the non-Clostridium sensu stricto animal and human pathogens currently assigned the genus name Clostridium, seems unlikely to change in the near future because of the chaos and the potential hazard that such otherwise justified genus name changes would engender. Future taxonomic classification based on whole-genome sequencing may help to resolve some of the complexity of clostridial classification.

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2General Physiological and Virulence Properties of the Pathogenic Clostridia

Julian I. Rood

Introduction

The key features that delineate members of the genus Clostridium are that they are Gram-positive rods that are anaerobic and form heat-resistant endospores. By and large these features define the genus, although there are some clostridia that stain Gram-negative and some clostridia that can grow in the presence of oxygen. Most members of this genus are commensal or soil bacteria that do not cause disease, but we tend to focus our attention on the pathogenic clostridia. The genus is extremely diverse and, by normal taxonomic criteria, should be divided into several different genera (Chapter 1). However, the established role of several clostridial species in some of the major diseases of humans and animals, including tetanus, botulism, gas gangrene, and various enteric and enterotoxemic syndromes, has precluded what would otherwise be a sensible and scientifically sound reclassification (Chapter 1). Recently, the movement of pathogens such as Clostridium difficile and Clostridium sordellii into the genera Peptoclostridium and Paeniclostridium, respectively, has been suggested, but these proposals are yet to be adopted formally.

Anaerobic metabolism

Bacterial metabolism is the process by which bacteria obtain nutrients and energy from the environment or their host, enabling them to grow and multiply. It is beyond the scope of this chapter to describe this process in detail, since entire books can and have been written on the topic. The key issue that will be discussed here is what, in general terms, distinguishes the metabolism of anaerobic bacteria from that of aerobic and facultative anaerobic bacteria. Aerobes are defined as bacteria that are unable to grow in the absence of oxygen. Facultative anaerobes can grow in the presence or absence of oxygen, usually growing more rapidly under aerobic conditions. Anaerobic bacteria are unable to grow in the presence of oxygen, but grow very well under anaerobic conditions. Anaerobic bacteria can be divided further into two major groups: strict anaerobes, which are killed by exposure to oxygen, and aerotolerant anaerobes, which can only grow anaerobically but are not killed by exposure to oxygen.

Aerobic bacteria obtain most of their energy, in the form of ATP, in a highly efficient manner by the passage of electrons through the membrane-bound electron-transport chain, culminating in the use of oxygen as a terminal electron acceptor. This process is known as aerobic respiration. In an aerobic environment, facultative anaerobes such as Escherichia coli or Salmonella spp. use the electron-transport chain to produce ATP. In the absence of oxygen, they are reliant on the far less efficient substrate-level phosphorylation process or the use of an alternative electron acceptor.

Anaerobic bacteria may still be able to obtain their energy from the electron-transport chain by use of an alternative terminal electron acceptor, usually an inorganic compound such as a nitrate or sulfate. This process is known as anaerobic respiration. Alternatively, they may carry out anaerobic fermentation and obtain all of their ATP from substrate-level phosphorylation, with oxidized NAD regenerated by the reduction of intermediates in the glycolytic pathway to ionized carboxylic acids such as acetate, lactate, or butyrate. Such organisms may significantly increase the throughput of sugars through the glycolytic pathway and therefore do not necessarily grow at a slower rate than aerobic bacteria, even though the output from aerobic respiration (38 moles of ATP per mole of glucose catabolized to CO2) is far greater than that from fermentation (2 moles of ATP per mole of glucose partially catabolized to a mixture of alcohols and/or organic acids).

Like many other bacteria, the clostridia are not restricted to metabolizing sugars to obtain their energy. They can ferment other compounds such as amino acids to obtain both their carbon and energy. For example, C. difficile uses the Stickland reaction in which pairs of amino acids are fermented in a coupled reaction, with one amino acid acting as an electron donor and the other amino acid acting as an electron acceptor.

Major clostridial diseases

Clostridial diseases and infections can be divided into three major types: neurotoxic diseases, histotoxic diseases, and enteric diseases. Although the focus of this book is clostridial diseases of animals, the clostridia are also important human pathogens. The major clostridial diseases of humans are botulism, tetanus, gas gangrene, food poisoning, pseudomembranous colitis, and antibiotic-associated diarrhea. The major clostridial diseases of animals are outlined in Chapter 3 (Table 3.1) and described in subsequent chapters.

In both humans and animals, botulism and tetanus are caused by Clostridium botulinum and Clostridium tetani, respectively. Traumatic gas gangrene or clostridial myonecrosis in humans is primarily mediated by Clostridium perfringens and non-traumatic gas gangrene by Clostridium septicum, although other clostridia such as Clostridium novyi and C. sordellii can cause severe histotoxic infections in humans and animals. Enterotoxin (CPE)-producing strains of C. perfringens are now the second major cause of human food poisoning in the U.S.A., and can also cause non-food-borne gastrointestinal disease. The major cause of human antibiotic-associated diarrhea and a broader range of enteric infections, including pseudomembranous colitis and toxic megacolon, is the major nosocomial pathogen, C. difficile.

The onset of clostridial infections

Although the pathogenesis of clostridial diseases invariably involves the production of potent protein toxins, it is important to note that, with one exception, they are true infectious diseases. The infectious bacterium needs to establish itself in the host and overcome the host’s innate and acquired immune defenses so that the pathogen can grow, multiply, and elaborate its toxins. The extent of bacterial growth that occurs may be fairly limited, for example the minimal growth of C. tetani in the deep wounds that lead to tetanus, or very extensive, for example the rapid growth of C. perfringens or C. septicum in histotoxic infections. The exception is botulism, which is often a true toxemia, with humans or animals consuming preformed botulinum toxin in their food.

Clostridial infections invariably require predisposing conditions, either the breaking of the skin or intestinal barriers by a deep or traumatic wound, or an alteration to the gastrointestinal microbiota caused by a change in the type of feed or by treatment with antimicrobial agents. For example, C. perfringens-mediated avian necrotic enteritis generally involves a change to a protein-rich feed that is often coupled with a predisposing coccidial infection, which leads to overgrowth of toxigenic C. perfringens strains and damage to the gastrointestinal mucosa. Similarly, human C. difficile infections usually follow changes to the intestinal microbiota brought about by treatment of patients with antimicrobial agents.

In most enteric infections caused by other bacterial genera, we know that there is a need for the invading bacteria to adhere to the gastrointestinal epithelium if they are to cause disease. Otherwise they will be washed out of the gastrointestinal tract by the normal one-way peristaltic flow of material. In these bacteria, a considerable amount is known about the role of different fimbriae or other types of surface adhesins that mediate this process. By contrast, little is known about the adhesion process utilized by clostridial enteric pathogens, primarily because research on these pathogens has traditionally focused on their toxins. The exception is human C. difficile infections, where several putative cell-surface adhesins have been identified, including a lipoprotein, two sortase-anchored proteins, S-layer proteins, flagellar proteins, a fibronectin-binding protein, and a putative collagen-binding protein. Therefore, there is considerable scope to investigate and understand the numerous roles of virulence determinants other than protein toxins in the pathogenesis of clostridial diseases.

The key role of protein toxins in clostridial disease

The primary feature of clostridial infections is that cell and tissue damage are mediated by potent protein toxins that are either secreted from the cell or released upon cell lysis. These toxins fall into three major classes: enzymes that act at the cell surface, pore-forming toxins, and toxins that are taken up by their target cells and exert their effects upon release into the cytoplasm.

Alpha toxin (CPA) is an essential virulence factor in C. perfringens