Salmonella enterica serovar typhi: molecular analysis of strains with decreased susceptibility and resistant to ciprofloxacin in India from 2001-2003.
Chromosomally-mediated reduced susceptibility to ciprofloxacin narrows the therapeutic options in enteric fever. We made a molecular comparison of clinical isolates of fluoroquinolone-resistant strains of Salmonella enterica serotype Typhi from January 2001 to May 2003; 178 isolates were subjected to antimicrobial susceptibility testing by the Kirby-Bauer method of disk diffusion, and agar dilution was used to determine the minimum inhibitory concentration (MIC) to ciprofloxacin. Nalidixic-acid resistant strains (NARST) were observed in 51% of the isolates, of which 98.9% had decreased susceptibility (MIC> or =0.125-1 microg/mL) to ciprofloxacin. A single strain (4 microg/mL) was resistant to ciprofloxacin and double mutations were found in the gyrA gene (76 Asp->Asn, 44 leu->Ileu). Among seven NARST strains with reduced susceptibility, a single mutation was found in five strains, one of which had 76 Asp->Asn and two each had mutations at 87 Asp->Asn and 72 Phe->Tyr, respectively); no mutations could be detected in two isolates. Routine antimicrobial surveillance, coupled with molecular analysis of fluoroquinolone resistance, is crucial for revision of enteric fever therapeutics.
Capoor
Malini R
MR
Department of Microbiology, Vardhman Mahaveer Medical College and Safdarjung Hospital, New Delhi, India.
Nair
Deepthi
D
Aggarwal
Pushpa
P
Mathys
Vanessa
V
Dehem
Marie
M
Bifani
Pablo Juan
PJ
D000890:Anti-Infective Agents / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics; D006801:Humans; D007194:India; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009268:Nalidixic Acid / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D012485:Salmonella typhi / Q000187:drug effects* / Q000235:genetics
D000890:Anti-Infective Agents; D004269:DNA, Bacterial; D009268:Nalidixic Acid; D002939:Ciprofloxacin