Fatin Naeem Abbas General characteristics Gramve large bacilli

Fatin Naeem Abbas

General characteristics • Gram+ve large bacilli • Obligate anaerobic. The anaerobic conditions can be established by: 1. Culture can be placed in an anaerobic jar. 2. Cultivating the organaism in liquid media such as cooked meat broth and thioglycolate broth.

Microscopical appearance: 1. C. tetani: Cause tetanus slender bacilli, motile, non-capsulated. Spores: spherical, terminal, and projected (drumstick bacillus) , characteristic swarming growth on anaerobic blood agar.

2. C. welchii (perfringenes): cause gas gangrene, Some strains of C. perfringens also cause a common form of food poisoning. Non-motile, capsulated in animal tissue. Spores : oval, subterminal and non-projecting n

3. C. botulinum: cause food-poisoning- n botulism. Large bacilli motile, non-capsulated. Spores: oval, central or subterminal and bulging (projecting)

Culture characteristic When cultured anaerobically on blood agar, C. perfringens grows rapidly, producing colonies with a unique double zone of hemolysis. In food poisoning, the organism can be sought in suspected food and patient's feces C. tetani Strictly an aerobic and rapidly kills by normal atmosphere grows readily in cooked- meat medium with only slight digestion on solid media cultured under anaerobic conditions, colonies are rarely seen since the organism spread as a diaphanous film which might escape brief examination, colonies are characterized by their delicate branching projections. C. botulinum Strictly anaerobic there is much variation colonial morphology but colonies are often irregularly round with a fimbriated edge translucent.

The organism can be cultured and identified by standard anaerobic methods , Toxin is also identifiable in serum, stool, and food. +Ab Nagler’s reaction -Ab n

Methods of anaerobic culture The use of deep media Anaerobic organism can be grown in solid media as deep agar culture addition of 0. 5 -1% glucose to the medium is further helpful because it acts as reducing agent. Anaerobic organisms can be grown in both cultures by first heating the medium to drive off the oxygen, then sterile melted vaseline is poured on the surface of the medium. The tubes are then rapidly cooled and used for the cultivation of clostridia

Removal of oxygen Culture can be grown in jars from which oxygen has been removed by first evacuation of the jar and then removing the remnants of oxygen by using Sodium Hydroxide and pyrogallic acid. e. g. Buchners tube and Bullochs jar (this method not used nowadays) Replacement of oxygen with hydrogen or nitrogen Mc. Intoch & Files jar: Most common method used nowadays for cultivating anaerobic on the surface of plates. The jars may be made of metal or glass. The inoculated plates are placed in the jar, the jar closed evacuated and then filled with hydrogen (sometimes nitrogen).

The use of special anaerobic media Special media are nowadays available which contain a variety of reducing substances such as Sod. Thioglycollate, cystine and vitamin C. in such media the anaerobes can be grown in the air without placing them in special anaerobic jars. Most useful and commonly employed medium for the cultivation of anaerobes. Sterilized muscle tissue contains reducing substances which contain anaerobic conditions particularly near the bottom.