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beta-lactamases in Shigella
1Department of Hospital Infections and Antibiotics, Statens Seruminstitut, Copenhagen, Denmark.
Abstract:
The occurrence of resistance and production of beta-lactamases was investigated in 60 Shigella strains. Ampicillin resistance was found in 28 (47%) of the isolates, the resistance being more frequent in Sh. flexneri than in Sh. sonnei. All strains were susceptible to cefotaxime, mecillinam, and ciprofloxacin. The beta-lactamases produced by Shigella were similar to TEM-1, OXA-1, or the low-level chromosomally mediated cephalosporinase produced by Escherichia coli. The beta-lactamases produced by Sh. flexneri were most often the OXA-1-like enzymes.
Insights
This study found ampicillin resistance in nearly half of Shigella strains, particularly Sh. flexneri. However, all strains remained susceptible to newer antibiotics like cefotaxime, indicating potential treatment options.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Shigella species are significant causes of bacterial dysentery worldwide.
- Antimicrobial resistance in Shigella poses a growing public health threat.
- Beta-lactamase production is a primary mechanism of resistance to beta-lactam antibiotics.
Purpose of the Study:
- To investigate the prevalence of ampicillin resistance in Shigella isolates.
- To characterize the types of beta-lactamases produced by these strains.
- To assess susceptibility to newer antimicrobial agents.
Main Methods:
- Sixty Shigella strains were collected and tested for antimicrobial susceptibility.
- Phenotypic methods were used to detect beta-lactamase production.
- Molecular characterization of beta-lactamases was performed.
Main Results:
- Ampicillin resistance was observed in 47% of Shigella isolates, with higher rates in Sh. flexneri compared to Sh. sonnei.
- Beta-lactamases identified included TEM-1, OXA-1, and a chromosomally mediated cephalosporinase.
- Sh. flexneri strains predominantly produced OXA-1-like beta-lactamases.
- All tested strains remained susceptible to cefotaxime, mecillinam, and ciprofloxacin.
Conclusions:
- Ampicillin resistance is prevalent in Shigella, necessitating careful antibiotic selection.
- The identified beta-lactamases are common resistance mechanisms.
- Susceptibility to third-generation cephalosporins and fluoroquinolones offers viable treatment alternatives for Shigella infections.