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Increase in minimum inhibitory concentration to quinolones and ceftriaxone in salmonellae causing enteric fever

Uma Sekar1, Padma Srikanth, Anupma Jyoti Kindo

  • 1Department of Microbiology, Sri Raniachandra Medical College & Research Institute Porur, Chennai.

The Journal of Communicable Diseases
|March 31, 2005
PubMed

Insights

Multidrug resistance in Salmonella typhi is increasing. This study found rising minimum inhibitory concentrations (MICs) for ciprofloxacin, ofloxacin, and ceftriaxone in Salmonella typhi and S. paratyphi A, potentially explaining treatment failures.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Antimicrobial Resistance

Background:

  • Multidrug resistance in Salmonella typhi is a significant global health concern.
  • Treatment failures in enteric fever have been reported with ciprofloxacin, necessitating updated susceptibility data.

Purpose of the Study:

  • To determine the antibiotic susceptibility patterns of Salmonella typhi and Salmonella paratyphi A isolated from typhoid bacteremia cases.
  • To evaluate the minimum inhibitory concentrations (MICs) of key antibiotics against these pathogens.

Main Methods:

  • Disc diffusion and broth dilution methods were employed to test 50 isolates (48 S. typhi, 2 S. paratyphi A).
  • Antibiotics tested included ampicillin, chloramphenicol, cotrimoxazole, tetracycline, ciprofloxacin, ofloxacin, cefuroxime, and ceftriaxone.

Main Results:

  • 68% of isolates exhibited resistance to ampicillin, chloramphenicol, cotrimoxazole, and tetracycline (ACCOT).
  • All strains remained susceptible to fluoroquinolones, cephalosporins, and aminoglycosides via disc diffusion.
  • Elevated MICs were observed for ciprofloxacin (28%), ofloxacin (50%), and ceftriaxone (40%), with some strains showing significantly high values.

Conclusions:

  • Emergence of high MIC levels for ciprofloxacin, ofloxacin, and ceftriaxone in S. typhi and S. paratyphi A is documented.
  • Rising MICs may correlate with treatment failures in enteric fever.
  • Continuous monitoring of MIC levels for ofloxacin and ceftriaxone, alongside ciprofloxacin, is recommended for treatment failure cases.

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