Research Projects

PFGE- a genotypic typing technique with high typeability, reproducibility and discriminatory power was standardized to type the Indian S. Typhi isolates. The PFGE technique was evaluated to depict molecular heterogeneity amongst the S. Typhi isolates. Six hundred and sixty four S.Typhi isolates from North, Central and South Zones of India were typed by PFGE. Eighty-nine different PFGE profiles were delineated which were grouped into 16 groups. The PFGE profile X15 was found to be the commonest PFGE profile with 4.36% strains belonging to this category. Majority of them belonged to E1 PT(phage type) with biotype I. The typeability and discriminatory index of PFGE was found to be 100% and 0.9, respectively in contrast to phage typing which had typeabiliy and discriminatory index of 76.4% and 0.25, respectively. The study evinced strong correlation between MDR S.Typhi isolates and the multiple PFGE profiles highlighting the co-existence of multiple MDR clones in the Indian subcontinent. Increased isolation of S. Typhi strains with intermediate susceptibility to Ciprofloxacin (?90%) occurred during 2008-10 possibly responsible for the reduced efficacy to the quinolone group in the enteric fever treatment. To summarize, PFGE was standardized effectively to delineate 89 PFGE profiles amongst the S. Typhi clones co-existing in the Indian subcontinent, the technique being more discriminatory than phage typing, can be complimented with the latte.