Clostridium botulinum and Cl. perfringens, the two members of the group have been implicated in food-borne illnesses. C. botulinum causes classical food-borne botulism due to ingestion of preformed toxin in food.
Epidemiology: Clostridia grow anaerobically in rewarmed food dishes produce toxin. These are gram-positive, anaerobic sporulating, catalase negative rod shaped organisms.
Clinical features: In case of poisoning due to Cl. botulinum, incubation period var ies from 24-9 6 ho urs. Toxin absorbe d fro m gut blo cks acetylcho line at neuromuscular junction. Diplopia, dysphagia, dysphonia and respiratory involvement occur. Mortality rate is high.Incubation period in case of Cl. perfringens ranges from 8-16 hours. Enterotoxin produced during sporulation in gut causes hyper secretion. Sudden onset of profuse diarrhoea occurs that may occasionally be accompanied with vomiting. Recovery takes in 1- 4 days.
Diagnosis: Robertson cooked meat medium is used for enrichment, however, other specific enrichment media are also available. The horse blood agar and anaerobic egg yolk agar are the recommended plating media for isolation of Cl. botulinum. The colonies are raised or flat, smooth or rough and commonly show some spreading with irregular edge. The selective media for isolation of Cl. Perfringens are tryptose sulphate cycloserine (TCS) agar, sulphate-polymyxin-sulphadiazine (SPS) agar, Shahid Ferguson perfringens (SFP) agar and neomycin blood agar, etc. PCR based detection of Cl. perfringens targeting alpha gene or epsilon toxin has been used.