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Synergistic antibacterial activity of ampicillin-cloxacillin mixtures against Proteus morganii
Abstract:
Synergistic antibacterial effects of mixtures of ampicillin and cloxacillin and induced penicillinases were investigated in 48 strains of Proteus. The serial tube dilution method was used to determine the minimal inhibitory concentration of ampicillin, cloxacillin, and 2:1 and 1:1 mixtures of ampicillin and cloxacillin. Production of penicillinases was determined by the cellulose acetate membrane method, with ampicillin, cloxacillin, mixtures of ampicillin and cloxacillin, penicillin G, and cephalothin as inducing agents and as substrates for penicillinase. Synergism occurred against P. morganii, but against no other species. The 1:1 ampicillin-cloxacillin combination was synergistic against 13 of 17 P. morganii strains; the 2:1 combination was synergistic against only 9 strains. Penicillinases, demonstrated in all species except P. mirabilis, hydrolyzed penicillin G and cephalothin. Although only P. vulgaris hydrolyzed ampicillin, no species of Proteus hydrolyzed cloxacillin or the ampicillin-cloxacillin mixtures. Penicillinases were, however, induced by ampicillin, cloxacillin, and the mixtures. There was no relationship between production of penicillinase and synergism with mixtures of ampicillin and cloxacillin.
Insights
Antibiotic combinations of ampicillin and cloxacillin showed synergistic effects against Proteus morganii strains. Penicillinase production was induced by these antibiotics but did not correlate with observed synergism.
Area of Science:
- Microbiology
- Pharmacology
- Bacterial Resistance
Background:
- Antibiotic resistance is a growing global health concern.
- Proteus species are opportunistic pathogens often associated with healthcare-associated infections.
- Understanding the efficacy of antibiotic combinations is crucial for effective treatment strategies.
Purpose of the Study:
- To investigate the synergistic antibacterial effects of ampicillin and cloxacillin mixtures against various Proteus strains.
- To examine the role of induced penicillinases in the activity of these antibiotic combinations.
- To determine the susceptibility patterns of Proteus species to ampicillin, cloxacillin, and their mixtures.
Main Methods:
- Minimal inhibitory concentrations (MICs) were determined using the serial tube dilution method.
- Penicillinase production was assessed via the cellulose acetate membrane method.
- Antibiotics used as inducers and substrates included ampicillin, cloxacillin, penicillin G, and cephalothin.
Main Results:
- Synergistic effects were observed exclusively against Proteus morganii strains.
- The 1:1 ampicillin-cloxacillin mixture demonstrated synergism against 13 of 17 P. morganii strains.
- Penicillinases were detected in most Proteus species, hydrolyzing penicillin G and cephalothin, but not ampicillin, cloxacillin, or their mixtures.
Conclusions:
- Ampicillin and cloxacillin combinations exhibit species-specific synergistic activity, primarily against Proteus morganii.
- While penicillinase production is inducible by these antibiotics, it does not directly predict synergistic outcomes.
- Further research into the mechanisms of synergism and resistance in Proteus is warranted.