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beta-Lactamase-producing strains in the species Prevotella intermedia and Prevotella nigrescens
L A Bernal1, E Guillot, C Paquet
1Groupe de Recherche en Ecologie Buccale, Faculté de Médecine Dentaire, Université Laval, Québec, Canada.
Abstract:
A total of 96 strains were collected that included laboratory strains and clinical isolates classified Prevotella intermedia sensu lato and the type strains of the species P. intermedia sensu stricto and Prevotella nigrescens. Susceptibility to amoxicillin and amoxicillin-clavulanic acid was determined by the Etest. PCR-DNA probe assays were used to speciate each strain as P. intermedia sensu stricto or P. nigrescens. By Etest, 71 strains (74%) were susceptible to both amoxicillin and amoxicillin-clavulanic acid with minimum inhibitory concentrations in the 0.016-0.064 microgram/ml range. In contrast, amoxicillin minimum inhibitory concentrations of 25 strains (26%) were in the range of 1.5-96 micrograms/ml with concomitant amoxicillin-clavulanic acid minimum inhibitory concentrations in the low range 0.016-0.38 microgram/ml, indicating a production of beta-lactamase as confirmed by nitrocefin tests. Of these beta-lactamase-producing strains, 20% (5/25) were identified as P. intermedia sensu stricto by the PCR-DNA probe assay and 72% (18/25) as P. nigrescens. Our results provide support for the major role of P. nigrescens in the failure of therapy using beta-lactam antibiotics.
Insights
Prevotella nigrescens is a key contributor to beta-lactam antibiotic treatment failures. This study found P. nigrescens frequently produces beta-lactamase, an enzyme that inactivates these drugs.
Area of Science:
- Microbiology
- Clinical Microbiology
- Antimicrobial Resistance
Background:
- Prevotella intermedia sensu lato is a complex group of bacteria.
- Understanding the antimicrobial susceptibility profiles of Prevotella species is crucial for effective treatment.
Purpose of the Study:
- To investigate the susceptibility of Prevotella intermedia sensu stricto and Prevotella nigrescens to amoxicillin and amoxicillin-clavulanic acid.
- To determine the prevalence of beta-lactamase production in these species.
- To identify the role of specific Prevotella species in beta-lactam antibiotic treatment failures.
Main Methods:
- Collected 96 bacterial strains, including laboratory and clinical isolates.
- Speciated strains using PCR-DNA probe assays.
- Determined antibiotic susceptibility using Etest and confirmed beta-lactamase production with nitrocefin tests.
Main Results:
- 74% of strains were susceptible to both amoxicillin and amoxicillin-clavulanic acid.
- 26% of strains exhibited resistance to amoxicillin, with low amoxicillin-clavulanic acid susceptibility, indicating beta-lactamase production.
- Beta-lactamase-producing strains were predominantly Prevotella nigrescens (72%).
Conclusions:
- Prevotella nigrescens plays a significant role in the failure of beta-lactam antibiotic therapies.
- Beta-lactamase production by P. nigrescens is a major mechanism of resistance.
- Accurate species identification is essential for predicting treatment outcomes.