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Nalidixic acid surrogate test for susceptibility to ciprofloxacin in Salmonella. Revisiting the question

José Luis Guzmán-Martín1, José María Navarro-Marí2, Manuela Expósito-Ruiz3

  • 1Departamento de Microbiología-Instituto de Investigación Biosanitaria de Granada, Universidad de Granada, Granada, Spain.

Journal of Medical Microbiology
|May 17, 2018
PubMed

Insights

Nalidixic acid (NA) susceptibility reliably predicts ciprofloxacin susceptibility in Salmonella, but varies by serogroup. NA is a good marker for serogroup D Salmonella, but not for serogroups B or C.

Area of Science:

  • Microbiology
  • Antimicrobial Resistance
  • Clinical Diagnostics

Background:

  • Fluoroquinolones, like ciprofloxacin, are crucial for treating Salmonella infections.
  • Accurate susceptibility testing is vital for guiding antibiotic therapy and monitoring resistance.
  • Nalidixic acid (NA) susceptibility has been proposed as a surrogate marker for ciprofloxacin susceptibility.

Purpose of the Study:

  • To evaluate the reliability of nalidixic acid (NA) susceptibility testing as a marker for ciprofloxacin susceptibility in Salmonella isolates.
  • To determine if NA can be used as a cost-effective and efficient method for predicting ciprofloxacin resistance in clinical settings.

Main Methods:

  • Analysis of 302 stool isolates of Salmonella.
  • Nalidixic acid (NA) susceptibility testing using the MicroScan NC53 system.
  • Ciprofloxacin susceptibility testing using the E-test method.

Main Results:

  • Overall, NA susceptibility demonstrated high accuracy in predicting ciprofloxacin susceptibility (81.5% sensitivity, 97.6% specificity).
  • Significant variations in predictive accuracy were observed among different Salmonella serogroups (P<0.001 for sensitivity).
  • NA reliably predicted ciprofloxacin susceptibility in serogroup D isolates but not in serogroups B or C.

Conclusions:

  • Nalidixic acid (NA) susceptibility testing is a reliable marker for ciprofloxacin susceptibility in certain Salmonella serogroups, particularly serogroup D.
  • The utility of NA as a surrogate marker for ciprofloxacin resistance is serogroup-dependent.
  • MicroScan-based NA susceptibility testing can be considered for predicting ciprofloxacin resistance in specific Salmonella serogroups within the study setting.
Keywords:
Salmonellaciprofloxacinenteritisnalidixic acidstools

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