Determination of drug susceptibility patterns and genotypes of Mycobacterium tuberculosis isolates from Kanpur district, North India.
OBJECTIVE
Molecular typing of Mycobacterium tuberculosis isolates has greatly facilitated the understanding of tuberculosis epidemiology. This study was done to characterize prevalent M. tuberculosis genotypes in a defined area of Kanpur district, North India by spoligotyping and IS6110-Restriction Fragment Length Polymorphism (RFLP) and to correlate the genotypes identified with their drug susceptibility patterns.


METHODS
Ninety-eight patients had clinical features suggestive of pulmonary tuberculosis (PTB) and out of them, 22 were new smear positive PTB (CAT I DOTS), 48 smear positive re-treatment, defaulters and CAT I failure PTB (CAT II DOTS) and 28 new smear negative PTB (CAT III). Out of them, sputum culture was positive for M. tuberculosis in 74 cases. DNA was extracted from growth on Lowenstein-Jensen slants and subjected to spoligotyping. Clusters were subsequently analyzed with IS6110 RFLP. Drug susceptibility testing was done for rifampicin, isoniazid, ethambutol, ofloxacin, streptomycin and kanamycin.


RESULTS
Thirty-seven spoligo patterns were observed. Predominant spoligotypes belonged to Central Asian Delhi family (33.78%), Beijing family (10.8%), East African-Indian family (5.4%), T1 family (5.4%) and U family (4.1%). RFLP analysis revealed 66% isolates had more than 10 IS6110 copies while 17% isolates each had low (1-5) and intermediate (6-9) copy numbers. All the isolates clustered by spoligotyping were identified unique by RFLP. Resistance to at least one drug was present in 35 (47.3%), out of which 8 patients belonged to CAT I and 27 to CAT II. Eleven (14.86%) were multi drug-resistant (MDR) and out of them, 6 (54.5%) isolates were of ST1/Beijing family. MDR-TB was significantly higher in Beijing strain than others (p<0.0001), however, most (83%) were from previously treated cases and thus can not be linked with recent transmission.


CONCLUSIONS
This approach of molecular typing appears promising and merits further evaluation to study dynamics of TB transmission specially in India.
Department of Tuberculosis and Respiratory Diseases, Ganesh Shankar Vidyarthi Memorial Medical College, Kanpur, India. sankalpgsvm@rediffmail.com
Sankalp
S
Purwar
Sudhir
S
Chaudhari
V M
VM
Katoch
Arun
A
Sampath
Pragya
P
Sharma
Prashant
P
Upadhyay
Devendra Singh
DS
Chauhan
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000995:Antitubercular Agents / Q000494:pharmacology*; D015373:Bacterial Typing Techniques; D016172:DNA Fingerprinting; D024881:Drug Resistance, Bacterial; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D007194:India / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D058889:Molecular Typing; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D013183:Sputum / Q000382:microbiology; D018088:Tuberculosis, Multidrug-Resistant / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology* / Q000635:transmission; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology* / Q000635:transmission
D000995:Antitubercular Agents