Kumar Sujeet, Bose Mridula, Isa Mohammad
Department of Microbiology, V. P. Chest Institute, University of Delhi, Delhi, India.
Indian J Med Res. 2006 Feb;123(2):139-44.
BACKGROUND & OBJECTIVE: Mycobacterium avium has emerged as a major opportunistic pathogen, infecting nearly 50 per cent of HIV/AIDS patients in the western world. There is no report from India regarding the typing profile of M. avium, a potential pathogen, the present study was undertaken to assess the genotypic diversity of Indian M. avium isolates of human origin.
A total of 65 biochemically identified M. avium isolates from sputum samples of patients with chronic pulmonary illness were subjected to IS1245 based restriction fragment length polymorphism (RFLP) and polymerase chain reaction (PCR) typing.
IS1245 insertion sequence based RFLP demonstrated polymorphism in 84.6 per cent isolates, while 15.4 per cent isolates did not hybridize on Southern blot and therefore were RFLP negative. Among the 55 RFLP positive isolates, 8 showed 1-3 bands, 19 had bands ranging between 4-9, and 28 isolates had >10 bands each. Although the isolates could be clubbed on the basis of number of bands, the banding profile was highly polymorphic. Among the 55 isolates typeable by RFLP, four clusters and 40 unique types of polymorphism were observed. Application of IS1245 based PCR typing on the same isolates showed that 87.7 per cent isolates were typeable. Interestingly the 10 isolates that were not typeable by IS1245 RFLP were typeable by IS1245 based PCR typing. Among the 57 PCR typed isolates a cluster of 14 isolates with identical 3-banded pattern was observed. Notably, 5 of the ten IS1245 RFLP negative isolates were within this cluster.
INTERPRETATION & CONCLUSION: Our results demonstrated that M. avium isolates from India were highly polymorphic with remarkable genetic diversity and heterogeneous RFLP profile. We observed that 47 per cent (n=27) isolates had RFLP profile suggestive of bird and animal origin indicating a strong association with the environment. By applying two typing methods based on IS1245 on the isolates 100 per cent typeability could be achieved.
鸟分枝杆菌已成为一种主要的机会性病原菌，在西方世界，近50%的艾滋病毒/艾滋病患者受到感染。印度尚无关于作为潜在病原菌的鸟分枝杆菌分型情况的报告，因此开展本研究以评估源自人类的印度鸟分枝杆菌分离株的基因多样性。
对从慢性肺部疾病患者痰液样本中经生化鉴定的65株鸟分枝杆菌分离株进行基于IS1245的限制性片段长度多态性分析（RFLP）和聚合酶链反应（PCR）分型。
基于IS1245插入序列的RFLP分析显示，84.6%的分离株存在多态性，而15.4%的分离株在Southern杂交中未出现杂交信号，因此为RFLP阴性。在55株RFLP阳性分离株中，8株显示1 - 3条带，19株有4 - 9条带，28株各有>10条带。尽管分离株可根据条带数量进行归类，但条带图谱具有高度多态性。在55株可通过RFLP分型的分离株中，观察到4个簇和40种独特的多态性类型。对相同分离株应用基于IS1245的PCR分型显示，87.7%的分离株可分型。有趣的是，10株不能通过IS1245 RFLP分型的分离株可通过基于IS1245的PCR分型。在57株经PCR分型的分离株中，观察到一组14株具有相同3条带模式的分离株。值得注意的是，10株IS1245 RFLP阴性分离株中有5株在该簇内。
我们的结果表明，来自印度的鸟分枝杆菌分离株具有高度多态性，具有显著的基因多样性和异质性RFLP图谱。我们观察到47%（n = 27）的分离株具有提示鸟类和动物来源的RFLP图谱，表明与环境有很强的关联。通过对分离株应用基于IS1245的两种分型方法，可实现100%的分型率。
