Antimicrobial susceptibility pattern and sequence analysis of DNA gyrase and DNA topoisomerase IV in Salmonella enterica serovars Typhi and Paratyphi A isolates with decreased susceptibility to ciprofloxacin.
We describe the antimicrobial susceptibility pattern of 100 typhoidal Salmonella isolates recovered from blood cultures and also investigate the association of decreased ciprofloxacin susceptibility with mutations in the genes coding for DNA gyrase and topoisomerase IV in 55 isolates.



The study was conducted between January 2013 and December 2015 at a tertiary care centre in north India. Antimicrobial susceptibility testing was performed by Kirby-Bauer disc diffusion and E-test. Genotypic characterization included the screening of mutations in the quinolone resistance-determining region of gyrA, gyrB, parC, and parE by PCR. DNA sequence analysis was done for 55 isolates.



Out of 100 isolates recovered 80 were S. Typhi, 18 were Paratyphi A and two were Paratyphi B. Eighty two percent (66/80) of S. Typhi and 15/18 S. Paratyphi A showed decreased ciprofloxacin susceptibility. The most common mutation in gyrA led to a change at codon 83 of serine to phenylalanine (n=37) or tyrosine (n=12). Five S. Typhi isolates that were resistant to ciprofloxacin (MICs of 12, 16, 24 and 32 μg/ml) had a second mutation at codon 87 in the gyrA gene changing aspartate to asparagine.



There is a need to urgently review the use of fluoroquinolones for the management of enteric fever in endemic areas.
Department of Microbiology, Division Bacteriology, Sanjay Gandhi Post-Graduate Institute of Medical Sciences, Lucknow-226014, India drricha1976@gmail.com.
Richa
R
Misra
Division of Microbiology, Central Drug Research Institute, Lucknow-226031, India.
Ritesh
R
Thakare
Department of Microbiology, Division Bacteriology, Sanjay Gandhi Post-Graduate Institute of Medical Sciences, Lucknow-226014, India.
N
N
Amrin
Department of Microbiology, Division Bacteriology, Sanjay Gandhi Post-Graduate Institute of Medical Sciences, Lucknow-226014, India.
Kashi Nath
KN
Prasad
Division of Microbiology, Central Drug Research Institute, Lucknow-226031, India.
Sidharth
S
Chopra
Department of Microbiology, Division Bacteriology, Sanjay Gandhi Post-Graduate Institute of Medical Sciences, Lucknow-226014, India.
Tapan Nirodhechand
TN
Dhole
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D002939:Ciprofloxacin / Q000494:pharmacology*; D027081:DNA Gyrase / Q000235:genetics*; D027101:DNA Topoisomerase IV / Q000235:genetics*; D052978:Disk Diffusion Antimicrobial Tests; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D024841:Fluoroquinolones; D005838:Genotype; D006801:Humans; D007194:India; D008826:Microbial Sensitivity Tests; D009154:Mutation; D016133:Polymerase Chain Reaction; D019779:Salmonella enterica / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D012482:Salmonella paratyphi A / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D012484:Salmonella paratyphi B / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D012485:Salmonella typhi / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D065288:Serogroup; D062606:Tertiary Care Centers; D014435:Typhoid Fever / Q000188:drug therapy / Q000382:microbiology*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D024841:Fluoroquinolones; D002939:Ciprofloxacin; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase
DNA gyrase; Decreased ciprofloxacin susceptibility; Paratyphi; Salmonella enterica; Topoisomerase IV; Typhi