This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'Vine leaf colonies are seen in: \nSelect and explain. \nA. Clostridium perfringens, B. Escherichia coli, C. Pseudomonas aeruginosa, D. Enterobacter cloacae', 'role': 'user'}, {'content': 'Answer: A \nExplanation: CULTURAL CHARACTERISTICS OF Clostridium perfringens: Rabbit sheep & human blood agar are used and on fuher incubation show TARGET HEMOLYSIS . This occurs due to the following toxins: Theta toxin - narrow zone - complete hemolysis Alpha toxin - wider zone - in complete hemolysis Double zone fades on prolonged incubation. Surface colonies are large, smooth, regular, convex, slightly opaque discs. Other types of colonies include one with a raised opaque centre and a flat radially striate transparent border. Rough flat colonies with an irregular edge-"VINE LEAF". A variant occasionally produces very mucoid broth cultures and tenacious colonies on blood agar. Ref: Koneman\'s Color Atlas & Textbook of Diagnostic Microbiology, 6th edition', 'role': 'assistant'}]