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Fluoroquinolone resistance in Salmonella typhi and S. paratyphi A in Bangalore, India

S Joshi1, S K Amarnath

  • 1Department of Microbiology, Manipal Hospital, 98 Rustom Bagh, Airport Road, Bangalore 560017, India. sangeeta.joshi@manipalhospital.org

Transactions of the Royal Society of Tropical Medicine and Hygiene
|September 5, 2006
PubMed

Insights

Fluoroquinolone resistance is rising in Salmonella typhi and Salmonella paratyphi A. This study found higher fluoroquinolone minimum inhibitory concentrations (MICs) in resistant strains, indicating a need to reassess enteric fever treatment strategies.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Antimicrobial Resistance

Background:

  • Increasing reports of fluoroquinolone resistance in Salmonella typhi and Salmonella paratyphi A.
  • Fluoroquinolones are critical for treating enteric fever.

Purpose of the Study:

  • To compare the minimum inhibitory concentrations (MICs) of various fluoroquinolones against Salmonella typhi and Salmonella paratyphi A.
  • To assess the prevalence of fluoroquinolone resistance in these pathogens.

Main Methods:

  • Agar dilution method to determine MICs of ciprofloxacin, ofloxacin, levofloxacin, and gatifloxacin.
  • Disc diffusion method for susceptibility testing against multiple antibiotics.
  • Analysis of 50 blood culture isolates (25 Salmonella typhi, 25 Salmonella paratyphi A).

Main Results:

  • Nalidixic acid resistance was observed in a significant proportion of both Salmonella typhi (17/25) and Salmonella paratyphi A (21/25) isolates.
  • Resistant isolates exhibited higher MICs to fluoroquinolones.
  • Complete resistance to ciprofloxacin (MIC >2 µg/L) was found in 5 Salmonella typhi and 6 Salmonella paratyphi A isolates.
  • No multidrug resistance was detected in Salmonella typhi.

Conclusions:

  • The emergence of fluoroquinolone resistance in Salmonella typhi and Salmonella paratyphi A is a significant concern.
  • The presence of fluoroquinolone resistance, even without multidrug resistance in Salmonella typhi, necessitates a review of current therapeutic guidelines for enteric fever.

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