Evaluation of the current trend of nalidixic acid susceptibility in typhoidal Salmonellae; a marker of therapeutic failure for the fluoroquinolones.

Background and Objectives: Typhoid is a major health problem faced by the developing countries like Pakistan. More than 20 million cases are reported annually worldwide. Currently fluoroquinolones are the drugs of choice to treat typhoid fever. In vivo resistance to fluoroquinolones leading to therapeutic failure is developing rapidly and is becoming a major concern for the clinicians. The objective of this study was to determine the sensitivity pattern of Nalidixic acid over the last four years
Material and Methods: A descriptive cross sectional study was carried out at the Microbiology Department of the Army Medical College, National University of Sciences and Technology, Rawalpindi from January 2006 to December 2009. All the isolates were dealt with standard microbiological procedures. The antimicrobial sensitivity of Nalidixic acid and Ciprofloxacin was determined using Kirby-Bauer disc diffusion method as per the guidelines of Clinical and Laboratory Standard Institute (CLSI).
Results: Out of 240 isolates, 111 were Salmonella typhi and 129 were Salmonella paratyphi A. The resistance of the typhoidal Salmonella to Nalidixic acid has reached significant levels and it seems only a matter of time when hundred percent resistance will be encountered. All isolates were sensitive to Ciprofloxacin on disc diffusion method.
Conclusion: Resistance to Nalidixic acid predicting therapeutic failure with fluoroquinolones is on a steady rise.