Clostridium septicum infections

M W ODENDAAL AND N P J KRIEK

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

Introduction

Several disease syndromes are associated with Clostridium septicum infection in livestock: malignant oedema and gas gangrene in ruminants, pigs and horses, gangrenous abomasitis known as braxy or bradsot in sheep, gangrenous abomasitis in lambs and calves following infection of abomasal ulcers, and post-parturient gas gangrene of the perineum, vulva and genital tract particularly of ewes and does, but also of cows (in South Africa this is often referred to as ‘baarmoeder sponssiekte’, [literally ‘uterine gas gangrene’]).

Malignant oedema develops as a consequence of wound infections and is an acute, febrile, highly fatal condition characterized by the presence of an oedematous and gangrenous inflammation of the affected parts, as well as toxaemia. ^{>1, 10, 12, 13, 15, 18, 19, 22, 30} Clostridium septicum may be a secondary invader, and often occurs in conjunction with other clostridia. It is considered to be the primary cause of malignant oedema in up to 30 per cent of cattle suffering from the disease.²⁷ Other histotoxic clostridia associated with gas gangrene in animals are C. perfringens type A or C, C. novyi, C. chauvoei and C. sordellii.

Braxy is a highly fatal disease which has, for a very long time, been known to occur in north-western Europe, principally in Norway, Denmark, North Germany, Iceland and the Faroe Islands, where it is known as ‘bradsot’ (‘quick plague’). It is also well known in parts of the UK and Ireland, North America and Australia. Braxy is characterized by severe oedema and gangrenous inflammation of the mucous membrane of the abomasum and severe toxaemia. Some cases of braxy may be due to C. novyi and are indistinguishable from the condition caused by C. septicum.

Clostridium septicum is a normal inhabitant of the intestinal contents of animals and is a frequent and rapid postmortal tissue invader and common contaminant; the longer the interim period between death and collection of tissue specimens, the better the chances of isolating C. septicum from animal tissues.

In southern Africa, losses of livestock, particularly cattle and sheep, as a result of malignant oedema, post-parturient gas gangrene and gangrenous abomasitis are encountered sporadically but braxy has not been reported in the region.

Aetiology

Clostridium septicum is usually a straight or slightly curved, Gram-positive bacillus 3 to 6 μm long and 0,4 to 1,2μm wide. Filaments up to 35 μm long are formed on the peritoneal surface of organs (particularly the diaphragmatic surface of the liver) of infected animals. It often stains unevenly with Gram’s stain. The bacterial cells usually occur singly or in pairs, are motile due to the presence of peritrichous flagella and exhibit pleomorphism and citrons, spindles and barred rods under certain conditions. Spores which are oval, subterminal and distend the cell are formed abundantly.^{5, 25}

Clostridium septicum is easily cultured on blood agar, and after two days’ incubation colonies are 1 to 8 mm in diameter, slightly raised, circular, semitranslucent, grey and glossy, with markedly irregular to rhizoid margins. A zone of complete haemolysis surrounds each colony. Due to the motility of the organisms, the colonies have a tendency to swarm on solid media which can be prevented by shortening the incubation period, increasing the agar content to 4 to 6 per cent, or by spreading specific antiserum over the surface of the agar plate.

Clostridium septicum is anaerobic. Optimum growth is attained at temperatures of between 37 and 40 °C, while most strains will also grow at 44 °C. Growth ceases at 46 °C. The presence of fermentable carbohydrate or serum in the culture medium stimulates its growth. Essential factors to sustain growth of the bacterium on artificial media include biotin, nicotinic acid, pyridoxine, thiamin, cysteine, tryptophan, adenine, arginine, aspartic acid, histidine, isoleucine, phenylalanine, serine, threonine, tyrosine and valine.²⁵

Clostridium septicum has saccharolytic and nonproteolytic properties and does not produce lipase or lecithinase. Cellobiose, fructose, galactose, lactose, maltose,mannose and trehalose are fermented and esculin is hydrolysed by 90 to 100 per cent of strains. Arabinose, amygdalin, glycogen, inositol, inulin, mannitol, melezitose, melibiose, raffinose, rhamnose, sorbitol, starch, sucrose and xylose are not fermented by 90 to 100 per cent of strains.^{7, 20}

Six different serological groups of C. septicum have been identified, based on combinations of two somatic (O) antigens and five types of flagellar (H) antigens that may be present. Serological typing is useful in epidemiological investigations of strains isolated from different sources.^{23, 25} Clostridium septicum and C. chauvoei share a common spore antigen which is responsible for cross-agglutination between them.

Clostridium septicum produces four different exotoxins. The alpha toxin is haemolytic, lethal and necrotizing, the beta toxin is a deoxyribonuclease, the gamma toxin is a hyaluronidase and the delta toxin is a thiol-activated cytolysin (an oxygen-labile haemolysin) which in the case of C. septicum is named septicolysin. The delta toxin is haemolytic, and considered lethal and cardiotoxic.²⁶ The production of toxins in a...