Hong Kong Med J 2013;19(Suppl 5):S4-7
Physiological fitness of drug-resistant Mycobacterium tuberculosis isolates in Hong Kong
EWC Chan, RCY Chan, MTK Au, RWM Lai
Department of Microbiology, The Chinese University of Hong Kong, The Prince of Wales Hospital
1. Drug target gene mutations in Mycobacterium tuberculosis conferred drug resistance at the expense of physiological fitness of the pathogen, rendering it less capable of multiplying even in a nutrient-rich environment.
2. Isolates containing mutations in gyrA experienced the strongest growth inhibition.
3. The growth fitness cost of resistance-gene mutations may only slow down mycobacterial growth at the initial phase (immediately after inoculation), possibly with little negative effect on the overall ability of this pathogen to cause disease in humans.
4. In addition to the mutation- induced effects, growth and survival fitness of multi-drug- resistant tuberculosis (MDR-TB) is also highly dependent on overall genetic constraints, which are unique to each organism.
5. Such MDR-TB mutants are fully capable of residing in human host-reservoirs and are as effective as their non- resistant counterparts in causing infections in the community.