Antimicrobial resistant Shigella in North India since the turn of the 21st century

Abstract

PurposeThe ubiquitous presence and rampant spread of antibiotic resistant strains of Shigella spp is a major public health concern. Therefore, monitoring the trends of antimicrobial resistance in them is essential. MethodsA total of 15440 stool samples were inoculated on MacConkey agar, lysine deoxycholate agar and Selenite F enrichment broth from 2001 to 2015.Out of 491 shigellae isolated, 250 isolates were recovered from our culture collection. Antimicrobial susceptibility was performed by Kirby Bauer disc diffusion method, E-test and phenotypic resistance screening for ESBL and AmpC production was performed. For the detection of beta-lactamase genes, PCR for blaTEM, blaSHV, blaOXA, blaCTX-M-15, CMY-2 and mphA PCR in isolates with decreased susceptibility to azithromycin(DSA) was performed. ResultsS. flexneri (n ​= ​173) was most common, followed by S.dysenteriae (n ​= ​24), S.sonnei (n ​= ​23), S.boydii (n ​= ​10) and Non agglutinating Shigella (NAG, n ​= ​20). A see-saw pattern in the prevalence of S. flexneri and S. dysenteriae and rising prevalence of S. sonnei and NAG was seen. Majority (77%) of the isolates had MICs >4 ​mg/L for ciprofloxacin and >50% had high MIC90 (12 ​mg/L) for ceftriaxone and cefepime (8 ​mg/L). Nearly 20% of S.flexneri were resistant to third generation cephalosporin by disc diffusion and 33.7% had MIC ≥1 ​μg/mL. Among the ceftriaxone resistant isolates (n ​= ​29) the blaTEM beta-lactamase resistance gene was seen in all, blaCTX-M-15 in 37%, blaCMY-2 in 45.6% and blaOXA in 52%. The first report of DSA at our institute was in 2001 (n ​= ​1, 2.5%) which increased to 35.1% (n ​= ​40) in 2011–15. The isolates with DSA included S. flexneri (n ​= ​40), S. boydii (n ​= ​4) and S. sonnei (n ​= ​1) and plasmid mediated resistance to azithromycin by mphA gene was detected in 19 out of 40 isolates of S. flexneri. ConclusionGlobal emergence of resistance Shigella is a matter of concern and calls for systematic monitoring and periodic updates of countrywide and local antibiogram.