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Susceptibility of shigellae to mecillinam, nalidixic acid, trimethoprim, and five other antimicrobial agents
Abstract:
A total of 199 strains of shigella (1 Shigella dysenteriae, 15 S. boydii, 47 S. flexneri, and 136 S. sonnei) isolated in Malmö, Sweden, within a 3-year period (1977 through January 1980) were tested with the agar plate dilution method for susceptibility to commonly used and newer antimicrobial agents. Mecillinam, nalidixic acid, and trimethoprim had the best in vitro activity. S. flexneri dominated among strains resistant to three or more antimicrobial agents and were less susceptible to ampicillin, chloramphenicol, and doxycycline than other types studied. Sixty-four percent of the strains were resistant to sulfamethoxazole. In vitro, a synergistic effect with trimethoprim was shown only in strains susceptible to sulfamethoxazole. The amidinopenicillin mecillinam was highly active against shigellae. When resistance occurred, it was linked to ampicillin in 17 of 18 strains. The quinolines, here represented by nalidixic acid, might be the drugs of choice.
Insights
Shigella strains showed varying antimicrobial susceptibility. Mecillinam, nalidixic acid, and trimethoprim demonstrated the best in vitro activity against Shigella infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Shigella species are a leading cause of bacterial dysentery worldwide.
- Antimicrobial resistance in Shigella poses a significant public health challenge.
- Understanding antimicrobial susceptibility patterns is crucial for effective treatment.
Purpose of the Study:
- To evaluate the in vitro antimicrobial susceptibility of Shigella strains isolated in Sweden.
- To identify effective antimicrobial agents for treating Shigella infections.
- To assess resistance patterns among different Shigella species.
Main Methods:
- Agar plate dilution method was used to test 199 Shigella strains.
- Susceptibility testing was performed against commonly used and newer antimicrobial agents.
- Strains were isolated in Malmö, Sweden, between 1977 and 1980.
Main Results:
- Mecillinam, nalidixic acid, and trimethoprim exhibited the highest in vitro activity.
- Shigella flexneri strains were frequently resistant to multiple agents and less susceptible to ampicillin, chloramphenicol, and doxycycline.
- Sixty-four percent of strains were resistant to sulfamethoxazole; synergistic effects with trimethoprim were observed only in susceptible strains.
- Mecillinam showed high activity, with resistance often linked to ampicillin resistance.
Conclusions:
- Mecillinam and nalidixic acid are promising agents for treating Shigella infections.
- Emerging resistance patterns, particularly in S. flexneri, necessitate ongoing surveillance.
- Quinolones, such as nalidixic acid, may be the drugs of choice for Shigella treatment.