Shigella and the fluorinated quinolones

Area of Science:

• Microbiology
• Infectious Diseases

Background:

• Acute diarrhea, dysentery, and colitis are significant public health concerns.
• Shigella species are common causative agents of bacterial dysentery worldwide.

Purpose of the Study:

• To investigate the prevalence of Shigella in patients with acute gastrointestinal infections.
• To determine the antimicrobial susceptibility patterns of isolated Shigella strains, particularly to nalidixic acid and fluoroquinolones.

Main Methods:

• Analysis of 531 stool samples from patients admitted to Kasturba Medical College Hospital, Manipal, between July 1996 and June 1997.
• Isolation and identification of Shigella species using standard microbiological techniques.
• Antimicrobial susceptibility testing, including resistance to nalidixic acid and fluoroquinolones (Ciprofloxacin, Norfloxacin, Ofloxacin).
• In vitro 'R' factor transfer studies to assess the transmissibility of resistance.

Main Results:

• Shigella was isolated from 29 samples (5.46%).
• Shigella flexneri was the predominant species (55.17%), followed by Shigella boydii (27.58%), Shigella dysentriae (10.34%), and Shigella sonnei (6.89%).
• Six strains (five Shigella flexneri, one Shigella dysentriae) showed resistance to nalidixic acid and fluoroquinolones.
• In vitro studies indicated that the observed antimicrobial resistance was not transferable.

Conclusions:

• Shigella is an important cause of acute diarrheal diseases in the region studied.
• Emergence of resistance to nalidixic acid and fluoroquinolones in Shigella strains is a concern.
• The non-transferable nature of this resistance suggests chromosomal rather than plasmid-mediated mechanisms.