Kambli Priti, Ajbani Kanchan, Nikam Chaitali, Sadani Meeta, Shetty Anjali, Udwadia Zarir, Georghiou Sophia B, Rodwell Timothy C, Catanzaro Antonino, Rodrigues Camilla
Microbiology Section, Department of Laboratory Medicine, P. D. Hinduja Hospital & Medical Research Centre, Mumbai, India.
Pulmonology Section, Department of Medicine, P. D. Hinduja Hospital & Medical Research Centre, Mumbai, India.
Int J Mycobacteriol. 2016 Mar;5(1):1-6. doi: 10.1016/j.ijmyco.2015.09.001. Epub 2015 Oct 1.
OBJECTIVE/BACKGROUND: The in vitro drug-susceptibility testing of Mycobacterium tuberculosis reports isolates as resistant or susceptible on the basis of single critical concentrations. It is evident that drug resistance in M. tuberculosis is quite heterogeneous, and involves low level, moderate level, and high level of drug-resistant phenotypes. Thus, the aim of our study was to correlate rrs (X52917) and eis (AF144099) promoter mutations, found in M. tuberculosis isolates, with corresponding minimum inhibitory concentrations of amikacin, kanamycin, and capreomycin.
Ninety M. tuberculosis clinical isolates were analyzed in this study. The minimum inhibitory concentrations were determined by MGIT 960 for 59 isolates with resistance-associated mutations in the rrs and eis promoter gene regions, and 31 isolates with wild-type sequences, as determined by the GenoType MTBDRsl (version 1) assay.
The rrs A1401G mutation was identified in 48 isolates resistant to the second-line injectables. The eis promoter mutations C-14T (n=3), G-10C (n=3), G-10A (n=3), and C-12T (n=2) were found within 11 isolates with various resistance profiles to the second-line injectables. Thirty-one isolates had wild-type sequences for the rrs and eis promoter gene regions of interest, one of which was amikacin, kanamycin, and capreomycin resistant. The isolates with the rrs A1401G mutation had amikacin, kanamycin, and capreomycin minimum inhibitory concentrations of >40mg/L, >20mg/L, and 5-15mg/L, respectively. The isolates with eis promoter mutations had amikacin, kanamycin, and capreomycin minimum inhibitory concentrations of 0.25-1.0mg/L, 0.625-10mg/L, and 0.625-2.5mg/L, respectively.
This study provides a preliminary basis for the prediction of phenotypic-resistance levels to the second-line injectables based upon the presence of genetic mutations associated with amikacin, kanamycin, and capreomycin resistance. The results suggest that isolates with eis promoter mutations have consistently lower resistance levels to amikacin, kanamycin, and capreomycin than isolates with the rrs A1401G mutation.
目的/背景：结核分枝杆菌的体外药敏试验根据单一临界浓度报告分离株为耐药或敏感。显然，结核分枝杆菌的耐药性具有很大的异质性，涉及低水平、中等水平和高水平的耐药表型。因此，我们研究的目的是将结核分枝杆菌分离株中发现的rrs（X52917）和eis（AF144099）启动子突变与阿米卡星、卡那霉素和卷曲霉素的相应最低抑菌浓度相关联。
本研究分析了90株结核分枝杆菌临床分离株。通过MGIT 960测定了59株在rrs和eis启动子基因区域有耐药相关突变的分离株以及31株经GenoType MTBDRsl（第1版）检测为野生型序列的分离株的最低抑菌浓度。
在48株对二线注射剂耐药的分离株中鉴定出rrs A1401G突变。在11株对二线注射剂有不同耐药谱的分离株中发现了eis启动子突变C-14T（n = 3）、G-10C（n = 3）、G-10A（n = 3）和C-12T（n = 2）。31株分离株在感兴趣的rrs和eis启动子基因区域具有野生型序列，其中一株对阿米卡星、卡那霉素和卷曲霉素耐药。具有rrs A1401G突变的分离株的阿米卡星、卡那霉素和卷曲霉素最低抑菌浓度分别>40mg/L、>20mg/L和5 - 15mg/L。具有eis启动子突变的分离株的阿米卡星、卡那霉素和卷曲霉素最低抑菌浓度分别为0.25 - 1.0mg/L、0.625 - 10mg/L和0.625 - 2.5mg/L。
本研究为基于与阿米卡星、卡那霉素和卷曲霉素耐药相关的基因突变预测对二线注射剂的表型耐药水平提供了初步依据。结果表明，与具有rrs A1401G突变的分离株相比，具有eis启动子突变的分离株对阿米卡星、卡那霉素和卷曲霉素的耐药水平始终较低。
