Pigment producing atypical mycobacteria ?
Correct Answer: M. gordonae and M. szulgai
Description: Ans. is 'c' i.e., M. gordonae and M. szulgai Non-tubercular mycobacteria (also called atypical mycobacteria) have been classified into four groups by Runyon based on pigment production and rate of growth. 1) Group I (photochromogens) :- These produce pigmented colonies (yellow-orange) only when exposed to light, but not in dark. Examples of photochromogens are M. asiaticum, M. kansasii, M. marinum, and M. simiae. 2) Group II (scotochromogens) :- These always produce pigmented colonies (yellow-orange-red), i.e. in dark as well as in light. Scotochromogens are M. flovescens, M. gordonae, M. scrofulaceum and M. szulgi. 3) Group HI (Nonchromogens) :- These do not produce pigment. Nonchromogens are M. avium complex (MAC), M. haemophilum, M. gastri, M. ulcerans, M. xenopi and M. nonchromogenicum. 4) Group IV (rapid growers) :- This is heterogeneous group of mycobacteria capable of rapid growth, colonies appearing within 7 days of incubation. Within the group, photochromogenic, scotochromogenic and nonchromogenic species occur. Chromogenic (pigment producing) rapid growers are mostly saprophytic, e.g. M. phlei and M. smegmetis. M. fouitum and M. chelonei do not produce any pigment. Other rapid growers are M. abscessus, M. vaccae, M. genevense, M. confluentis, and M. intermedium.
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