Emergence of Extensively Drug-resistant Shigella sonnei in Bangladesh

The objective of the study was to investigate current species distribution and growing antimicrobial resistance (AMR) of Shigella isolates for proper treatment. Shigellae, isolated from faecal samples in International Centre for Diarrhoeal Disease research, Bangladesh, Dhaka hospital in 2015, were tested for antimicrobial susceptibility by disc diffusion method to ampicillin, co-trimoxazole, ciprofloxacin, azithromycin, mecillinam, ceftriaxone/cefixime and meropenem. Extensively drug-resistant (XDR, resistant to 5 or 6 of 7 useful anti-Shigella drugs tested) Shigella isolates resistant to 6 drugs were analyzed for ESBL and AmpC phenotypes, plasmid profiles, R-plasmids transfer, bla SHV , bla TEM , bla CTX-M , bla OXA ; and mphA, mphB, ermA, ermB, ermC, ereA, ereB, mefA and msrA genes by PCR; and clonality of S. sonnei by PFGE. Of 134 isolates cultured from 3722 (3.6%) diarrhoeal faecal samples, 46% were S. sonnei, 37% S. flexneri, 4% S. boydii, 5% S. dysenteriae and 7% non-typeable. Multidrug-resistant (MDR, resistant simultaneously to ≥3 drugs) S. sonnei were 95% compared to 66% (P TEM and bla CTX-M ; 1 S. boydii had bla SHV , bla TEM and bla CTX-M ; 1 S. sonnei had bla TEM β-lactamase. All but one S. flexneri had only mphA gene on 62-MDa conjugative-R-plasmid coding azithromycin resistance. PFGE identified MDR-S. sonnei Global III clade. Thus, MDR-S. sonnei replaced S. flexneri as predominant isolate in Dhaka, Bangladesh; many emerged as XDR strains requiring treatment by meropenem. The findings demand judicial use of antibiotics to contain emergence and spread of resistance locally and globally. Physicians should be informed about MDR and XDR Shigella for judicious prescribing of antimicrobial therapy.