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Antimicrobial susceptibilities of shigellae isolated in Houston, Texas, in 1974
Abstract:
One hundred seventy-three strains of shigellae (113 Shigella sonnei, 56 S. flexneri, and four others) isolated in Houston during 1974 were tested for susceptibility to commonly used and newer antimicrobial agents. Forty-five percent of S. sonnei strains were susceptible to ampicillin, whereas 93% of S. flexneri strains were susceptible to that agent. S. sonnei and S. flexneri strains were equally susceptible to tetracycline (35 and 33%, respectively). All 173 strains were uniformly susceptible to quinoline drugs (cinoxacin, oxolinic acid, and nalidixic acid) and to trimethoprim-sulfamethoxazole. This study supports recent suggestions that the initial therapy of bacillary dysentery no longer should be ampicillin or tetracycline. It remains for field testing to determine whether quinoline agents or trimethoprim-sulfamethoxazole will be the treatment of choice.
Insights
Shigella sonnei and Shigella flexneri strains show decreased susceptibility to ampicillin and tetracycline. However, all strains were susceptible to quinoline drugs and trimethoprim-sulfamethoxazole, suggesting new treatment options for bacillary dysentery.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Shigellosis, a common cause of bacterial dysentery, is often treated with ampicillin or tetracycline.
- Antimicrobial resistance in Shigella strains can complicate treatment efficacy.
- Understanding current antimicrobial susceptibility patterns is crucial for effective patient management.
Purpose of the Study:
- To evaluate the antimicrobial susceptibility of Shigella strains isolated in Houston in 1974.
- To compare the efficacy of commonly used antibiotics versus newer agents against Shigella.
- To inform treatment guidelines for bacillary dysentery.
Main Methods:
- Antimicrobial susceptibility testing was performed on 173 Shigella strains (113 Shigella sonnei, 56 S. flexneri).
- Strains were tested against ampicillin, tetracycline, quinoline drugs (cinoxacin, oxolinic acid, nalidixic acid), and trimethoprim-sulfamethoxazole.
- Susceptibility percentages were calculated for each antibiotic and strain type.
Main Results:
- Only 45% of Shigella sonnei strains were susceptible to ampicillin, compared to 93% of Shigella flexneri strains.
- Susceptibility to tetracycline was low and similar for both S. sonnei (35%) and S. flexneri (33%).
- All 173 strains demonstrated uniform susceptibility to quinoline drugs and trimethoprim-sulfamethoxazole.
Conclusions:
- Ampicillin and tetracycline are becoming less effective for treating Shigella infections.
- Quinoline drugs and trimethoprim-sulfamethoxazole represent promising alternatives for bacillary dysentery treatment.
- Further clinical studies are needed to establish the preferred first-line therapy.