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
Stalactite growth in ghee broth is due to 
Select and explain. 
A. H. influenza, B. C. diphtheria, C. Y -pestis, D. T. pallidium
C: Y -pestis
Answer: C: Y -pestis 
Explanation: Ans. is 'c' i.e., Y. pestis Culture characteristic -Growth occurs over a wide range of temperature (range 2-45degC) and pH (5-9.6 optimum 7.2). The optimum temperature for growth is 27degC (unlike most pathogens). - In ghee broth a characteristic growth occurs which hangs down into broth from the surface resembling stalactites - Stalactite growth. - On blood agar colonies are dark due to the hemin pigment.