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Resistance of shigella to nalidixic acid & fluorinated quinolones
M A Thirunarayanan1, M V Jesudason, T J John
1Department of Microbiology, Christian Medical College & Hospital, Vellore.
Abstract:
It is known that nalidixic acid resistance is a relatively rare phenomenon among shigellae. Between June 1989 and May 1990, six strains of shigellae resistant to nalidixic acid were isolated. These strains also exhibited resistance to three newer fluoroquinolones, viz., ciprofloxacin, pefloxacin and enoxacin. In repeated experiments, nalidixic acid resistance did not transfer to a suitable recipient.
Insights
Nalidixic acid resistance in shigellae is rare. Six resistant strains were identified, also showing resistance to newer fluoroquinolones like ciprofloxacin, with resistance not transferring between bacteria.
Area of Science:
- Microbiology
- Bacterial genetics
- Antimicrobial resistance
Background:
- Nalidixic acid resistance is infrequently observed in Shigella species.
- Emerging antimicrobial resistance poses a significant public health threat.
Purpose of the Study:
- To investigate the prevalence and characteristics of nalidixic acid-resistant Shigella strains.
- To determine the co-resistance patterns of these strains with newer fluoroquinolones.
Main Methods:
- Isolation and identification of Shigella strains from clinical samples.
- Antimicrobial susceptibility testing against nalidixic acid and selected fluoroquinolones (ciprofloxacin, pefloxacin, enoxacin).
- Bacterial conjugation experiments to assess the transferability of resistance.
Main Results:
- Six Shigella strains exhibiting resistance to nalidixic acid were isolated between June 1989 and May 1990.
- These resistant strains demonstrated co-resistance to ciprofloxacin, pefloxacin, and enoxacin.
- Experiments confirmed that nalidixic acid resistance did not transfer to a recipient strain via conjugation.
Conclusions:
- The emergence of nalidixic acid-resistant Shigella strains with co-resistance to newer fluoroquinolones is a concern.
- The non-transferable nature of this resistance suggests chromosomal or other non-plasmid-mediated mechanisms.
- Continued surveillance of antimicrobial resistance in Shigella is crucial for effective treatment strategies.