Morcillo Nora S, Imperiale Belén R, Di Giulio Ángela, Zumárraga Martín J, Takiff Howard, Cataldi Ángel A
Reference Laboratory of Tuberculosis Control Program of Buenos Aires Province, Dr. Cetrangolo Hospital, Vicente López, Buenos Aires Province, Argentina.
Mycobacteria Laboratory, Petrona V. de Cordero Hospital, San Fernando, Buenos Aires Province, Argentina.
Tuberculosis (Edinb). 2014 Dec;94(6):672-7. doi: 10.1016/j.tube.2014.08.003. Epub 2014 Aug 15.
There has been an on-going debate on whether the development of drug resistance in Mycobacterium tuberculosis reduces its relative fitness and its ability to cause disease. The aim of this study was to explore this relationship. For this purpose, we evaluated the in vitro growth of clinical isolates and the transmission of the strains within the patients' households. Clinical and epidemiological data from patients in households, drug-susceptibility and genetic patterns of the isolates were collected. BACTEC MGIT 960™ system with the Epicenter™ software was used to perform fitness experiments and calculate the relative fitness (RF) comparing with the H73Rv reference strain. From 39 households, 124 patients and 388 contacts were included. Concerning transmission, 20 Multi drug-resistant (MDR) and 16 drug sensitive (DS) index cases generated 23 and 28 secondary cases, respectively. An average RF drop of 16.7% was found for MDR strains, but only mutations in rpoB codons 531 were associated with reduced fitness. When the strains were transmitted, their RF tended to decrease, and strains with low RF were less frequently transmitted. Within the limitations of this study, the results showed that the decrease in RF was associated to a limited transmission among the households' contacts.
关于结核分枝杆菌耐药性的发展是否会降低其相对适应性及其致病能力，一直存在着持续的争论。本研究的目的是探讨这种关系。为此，我们评估了临床分离株的体外生长情况以及菌株在患者家庭中的传播情况。收集了家庭中患者的临床和流行病学数据、分离株的药敏情况和基因模式。使用带有Epicenter™软件的BACTEC MGIT 960™系统进行适应性实验，并计算与H73Rv参考菌株相比的相对适应性（RF）。纳入了39个家庭的124名患者和388名接触者。关于传播，20例耐多药（MDR）和16例药物敏感（DS）指数病例分别产生了23例和28例继发病例。发现MDR菌株的平均RF下降了16.7%，但只有rpoB密码子531的突变与适应性降低有关。当菌株传播时，其RF往往会降低，而RF低的菌株传播频率较低。在本研究的局限性范围内，结果表明RF的降低与家庭接触者之间有限的传播有关。
