Other clostridial infections

N P J KRIEK AND M W ODENDAAL

GENERAL INTRODUCTION: ENDOSPORE-FORMING GRAM-POSITIVE RODS AND COCCI Malignant oedema/gas gangrene group of Clostridium spp.

This chapter deals with a number of clostridia which are infrequently associated with disease. These include Clostridium sordellii, C. carnis, C. difficile and C. fallax. In general, they are associated with wound infections in which the clinical and pathologic features resemble those of malignant oedema or gas gangrene caused by the better-known histotoxic clostridia. In rare instances, as in the case of certain C. sordellii infections, they are also associated with sudden death in lambs or cattle, or with the occurrence of haemorrhagic enteritis in foals, sheep and feedlot cattle.

Clostridium sordellii infections

Introduction

Clostridium sordellii infection is associated sporadically with diarrhoea and haemorrhagic enteritis in cattle in feedlots, ¹ adult sheep² and foals,⁸ a sudden-death syndrome in lambs¹⁵ and feedlot cattle,^{6, 16} and malignant oedema which resembles that caused by C. novyi type A and C. septicum infections in cattle.²⁰

Clostridium sordellii was first described by Sordelli in 1922 as Bacillus oedematiens sporogenes. It is often isolated in association with other bacteria, including the well-known histotoxic clostridia, and may not be of primary importance as a cause of disease.¹⁶

Aetiology

Clostridium sordellii is an anaerobic, Gram-positive, rodshaped bacterium with rounded ends, 2 to 4 μm long and 0,5 to 1 μm wide, and occurs singly or in pairs. The cells are motile by virtue of their peritrichous flagella. Spores often form and are oval, situated centrally or subterminally and swell the cell slightly.¹⁷ Sporulation occurs readily in media such as chopped meat broth incubated for 24 hours or blood agar plates after 48 hours’ incubation. On rabbit blood agar the bacterium is slightly beta-haemolytic, and the surface colonies are 1 to 4mm in diameter, have a circular or irregular outline, are translucent to opaque or grey with a dull-white, shiny surface, and have a granular or mottled internal structure. The margin of the colonies is scalloped, lobate or entire.⁵

The optimum temperature for growth is 30 to 37 °C with only moderate growth taking place at 25 °C and 45 °C. Growth is inhibited by incorporating 6,5 per cent sodium chloride and 20 per cent bile in the medium. Phosholipase C is produced in small amounts in culture and its production is best demonstrated on egg yolk agar. No lipase is produced. Clostridium sordellii has saccharolytic and proteolytic characteristics. Glucose and maltose are fermented, while strains vary in their ability to ferment arabinose, fructose, glycerol, raffinose, ribose, and xylose. Adonitol, amygdalin, cellobiose, cellulose, dulcitol, erythritol, esculin, galactose, glycogen, inositol, sorbose, starch, sucrose and trehalose are not fermented. Fermentation in a peptoneyeast extract broth yields large amounts of acetic, isobutyric and isovaleric acids, as well as smaller amounts of propionic and isocaproic acids.^{5, 14}

Clostridium sordellii produces a variety of biological substances toxic to animals, though non-pathogenic strains do occur. The unnamed, major lethal exotoxin produces a severe, gelatinous oedema and is thermolabile and nonhaemolytic, while the lesser toxins include phospholipase C, an oxygen-labile haemolysin, a fibrinolysin, a collagenase, and those that are dermonecrotizing and haemorrhagic when injected into the skin of rats and guinea pigs.^{3, 17}

Epidemiology

Clostridium sordellii can be isolated from soil, which is its principal habitat, and from the intestinal content of humans and animals. Faecal dissemination assists in the spread of the organism in the environment. Infections occur either by ingestion or by contamination of wounds.¹⁷

The conditions under which the disease syndromes caused by C. sordellii occur in livestock, and their predisposing factors, have not been clearly defined.

Pathogenesis

The pathogenesis of the disease syndromes is essentially unknown. Anaerobic conditions, such as those that exist in necrotic tissues, are required for growth and toxin production by the organism.¹⁷

Clinical signs and pathology

In experimental cases of the sudden death syndrome in cattle, affected animals have a marked increase in their respiratory rate, suddenly go down, and then die quickly—animals may be found dead after having been seen to be healthy as little as three hours earlier.⁶ The lesions in cattle that have died of the sudden death syndrome and of malignant oedema (the two designations probably referring to the same syndrome) are characterized by the infiltration of a haemorrhagic, inflammatory oedema of the peritracheal and peripharyngeal areas, with a particularly foul odour.^{18, 20} This oedema may extend to involve the subcutaneous tissues of the neck, but the muscles in the region are unaffected. It may also occur in the subcutaneous tissues of the hind limbs.¹⁶ Severe haemolysis is also evident in some of the cases, as detected in blood specimens presented for chemical pathology.⁶

A sudden death syndrome¹⁵ has been reported in lambs. Animals that have died of this syndrome reveal generalized congestion, marked ascites and hydropericardium, and a markedly enlarged, degenerated liver at necropsy.

Adult sheep and cattle affected by the enteric syndrome may show diarrhoea for some time before they die as a result of a severe, haemorrhagic enteritis.² A similar enteric syndrome has been encountered in neonatal foals.⁸ Affected animals manifest either diarrhoea—the faeces containing blood and gas — with death occurring soon after the commencement of clinical signs, or severe colic with the foals only passing small amounts of faeces containing blood and gas before they die. At necropsy, affected animals show a segmental haemorrhagic ileitis, a distinct line of demarcation between the unaffected and affected tissue being characteristic.⁸

Diagnosis and differential diagnosis

The syndromes caused by infection with C. sordellii may be confused with those diseases that cause sudden death, particularly the clostridial infections associated with gas gangrene or malignant oedema and with enterotoxaemias, such as those that are caused by C. perfringens types A and C. The diagnosis in live animals and at necropsy should be confirmed by bacterial isolation. Depending to some extent on the suspected syndrome involved, specimens from dead animals for this purpose should include portions of the small intestine (unopened and tied-off at either end), affected tissues, and subcutaneous tissue or muscle collected using sterile techniques, and should be submitted to the laboratory packed in ice.

The specimens are plated on to blood agar and incubated under anaerobic conditions overnight. Single colonies are selected for inoculation into Robertson’s cooked meat broth to provide inocula for the fermentation tests and material for in vivo pathogenicity and toxicity tests in laboratory animals. ¹⁹ Clostridium sordellii must be distinguished from Clostridium bifermentans by its production of urease, its failure to ferment sorbitol, and its toxigenicity. A positive diagnosis is warranted if a pathogenic strain is isolated in virtually pure culture and in profusion from typical lesions. The organism can also be identified by immunofluorescent staining but it does cross-react with Clostridium novyi.¹⁶

Control

Abacterin or toxoid of C. sordellii is contained insomemultivalent vaccines which have been used with success in feedlot cattle in the USA. Animals vaccinated for the first time should receive two injections, four weeks apart.^{4, 6, 12} Similar vaccines containing C. sordellii are commercially available in South Africa under a variety of trade names.

Clostridium carnis infections

Clostridium carnis is an aerotolerant Gram-positive bacillus, with dimensions of 0,5 × 2–4 μm. Under anaerobic growth conditions it grows rapidly and profusely on sheep blood agar to become slightly raised, flattened, grey-yellow colonies, with irregular margins. A narrow zone of haemolysis usually surrounds each colony, although its width may vary from one strain to another. Clostridium carnis actively produces exotoxins but not much is known about their characteristics. It appears that guinea pigs, mice, rabbits, sheep, mink, cats and cattle are susceptible to infection with C. carnis. A disease in cattle ascribed to C. carnis that resembled the clinical and pathological characteristics of blackquarter caused by C. chauvoei has been described.¹⁷

Clostridium difficile infections

Clostridium difficile was first isolated from a new-born infant in 1935 but it was not associated with disease in humans before 1977, when its association with the development of a severe antimicrobial-associated pseudomembranous enterocolitis in adults became apparent. It is also known to cause antibiotic-induced enterocolitis in hamsters, mice, guinea-pigs and rabbits,¹⁰ and, rarely, necrohaemorrhagic enterocolitis in horses and abscessation in goats.^{9, 11}

The possible association of C. difficile with disease in livestock was reported for the first time in 1981,⁹ when the organism was isolated from mandibular abscesses in a goat. It has subsequently been isolated from pigs suffering from salmonellosis,¹⁰ and from the intestinal content of four foals suffering from a haemorrhagic, necrotizing enteritis which rapidly caused the death of the animals within two days of the first clinical signs being observed.¹¹ These foals were one to three days old when they became ill, manifesting colic, severe dehydration, and reduced body temperature, but increased heart and respiratory rates. They appeared to suffer severe pain, as they rolled repeatedly and lay in abnormal postures. Three of the foals developed diarrhoea, with watery, brownish-red, foul-smelling faeces. At necropsy the severity of the lesions differed, but were similar in nature. The small intestine showed the presence of a severe, diffuse, haemorrhagic enteritis with patchy mucosal erosions, while the colon, of which the mucosa was congested and oedematous, contained necrotic material. Histologically a feature of the lesions in the small intestine was coagulative necrosis of the distal twothirds of the intestinal villi. Large numbers of rod-shaped, Gram-positive bacteria were apparent on the surface of the affected villi and free in the lumen of the intestine. Similar but less severe lesions in which only few bacteria were present, occurred in the wall of the colon.¹¹

Most strains of C. difficile produce at least two exotoxins, the major toxins being designated A and B. Toxin A is an enterotoxin and causes the accumulation of haemorrhagic fluid and detachment of epithelial cells in the small intestine of laboratory animals. Toxin B, a cytotoxin, is 1 000 times more potent than toxin A, but only exerts its effect after damage has been induced by toxin A, or if trauma is present in the intestinal epithelium.

Clostridium difficile is easily isolated anaerobically on cycloserine- cefoxitin-fructose agar medium from the intestinal content of foals suffering from the diarrhoea it causes. On other media it is rapidly overgrown by other bacteria. Its involvement in a pathological process should be confirmed by demonstrating the presence of the cytotoxin by in vitro and mouse neutralization tests,¹¹ enzyme-linked immunosorbent analysis (ELISA), or a number of other immunologically based tests.¹³

On culture, C. difficile produces small (2 mm diameter), non-haemolytic, greyish, flat colonies on sheep blood agar after three days’ incubation at 37 °C. The organisms are Gram-positive, form terminal ellipsoid spores, are motile and indole-negative, liquify gelatin, produce hydrogen sulphide and acid but no clot in Crosley milk medium, and ferment glucose but not sucrose or lactose.⁹

Clostridium fallax infection

A single fatal case of malignant oedema caused by C. fallax has been described in a horse. The lesions could not be distinguished from those caused by the other histotoxic clostridia associated with the development of malignant oedema in horses.⁷

References

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