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The effects of combinations of selected antibiotics on the growth of Corynebacterium equi.
Abstract: The minimal inhibitory concentrations of penicillin G, ampicillin, gentamicin, erythromycin and rifampicin were determined for nine strains of Corynebacterium equi. The effect of combinations of any two of these antibiotics on the killing of these strains was determined at antibiotic concentrations achievable in horses using recommended drug dosages (ampicillin 4.0 microgram/ml, gentamicin 1.0 microgram/ml using recommended drug dosages (ampicillin 4.0 microgram/ml, gentamicin 1.0 microgram/ml and erythromycin 0.25 microgram/ml). Penicillin G was used at 4.0 microgram/ml and rifampicin at 0.063 microgram/ml. The combinations of gentamicin with erythromycin or rifampicin gave antagonistic effects on killing compared to either drug alone. Combinations of erythromycin with rifampicin or penicillin showed synergistic effects, as did penicillin--gentamicin. All other combinations, and a triple combination of penicillin--rifampicin--erythromycin, showed additive effects only.
Publication Date: 1984-03-01 PubMed ID: 6561258DOI: 10.1111/j.1365-2885.1984.tb00880.xGoogle Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research study investigates the influence of combinations of certain antibiotics on the growth of Corynebacterium equi bacteria. It was found that some combinations, like erythromycin with rifampicin or penicillin, showed synergistic effects in slowing down the bacteria growth, while others like gentamicin with erythromycin or rifampicin showed antagonistic effects.
Determining Minimal Inhibitory Concentrations
- The study began with determining the Minimal Inhibitory Concentrations (MICs) – the lowest concentration of a chemical, in this case, an antibiotic, which prevents visible growth of a bacterium – for five antibiotics including penicillin G, ampicillin, gentamicin, erythromycin and rifampicin on Corynebacterium equi bacteria strains.
- The MIC determination process helps in understanding which concentration of these antibiotics was most effective in restricting the growth of Corynebacterium equi.
Testing the Effect of Antibiotic Combinations
- The study further explored the effect of different combinations of these antibiotics in inhibiting the growth of the Corynebacterium equi.
- These combinations were conducted using the antibiotic concentrations that could be practically achieved in horses using recommended drug dosages.
Antagonistic and Synergistic Effects of Antibiotics
- Two types of effects were observed from these combinations. The first was antagonistic, where the effect of two antibiotics together was less than the effect of each antibiotic when used alone.
- Such antagonistic effects were observed when gentamicin was combined with either erythromycin or rifampicin.
- The second type of effect observed was synergistic, where two antibiotics together showed a greater effect than the sum of their individual effects.
- Such synergistic effects were noticed when erythromycin was combined with rifampicin or penicillin, and also for the penicillin-gentamicin combination.
Additive Effects of Antibiotic Combinations
- Apart from the synergistic and antagonistic effects, some combinations showed additive effects. This means that the effect of two antibiotics together was exactly equal to the sum of their individual effects.
- All other combinations, and a triple combination of penicillin, rifampicin, and erythromycin showed these additive effects.
Cite This Article
APA
Prescott JF, Nicholson VM.
(1984).
The effects of combinations of selected antibiotics on the growth of Corynebacterium equi.
J Vet Pharmacol Ther, 7(1), 61-64.
https://doi.org/10.1111/j.1365-2885.1984.tb00880.x Publication
Researcher Affiliations
MeSH Terms
- Ampicillin / pharmacology
- Animals
- Anti-Bacterial Agents / pharmacology
- Bronchopneumonia / veterinary
- Corynebacterium / drug effects
- Drug Combinations
- Drug Interactions
- Erythromycin / pharmacology
- Gentamicins / pharmacology
- Horse Diseases / microbiology
- Horses
- Lung / microbiology
- Penicillin Resistance
- Penicillins / pharmacology
- Rifampin / pharmacology
Citations
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- Gundelly P, Suzuki Y, Ribes JA, Thornton A. Differences in Rhodococcus equi Infections Based on Immune Status and Antibiotic Susceptibility of Clinical Isolates in a Case Series of 12 Patients and Cases in the Literature. Biomed Res Int 2016;2016:2737295.
- Cohen ND, Slovis NM, Giguère S, Baker S, Chaffin MK, Bernstein LR. Gallium maltolate as an alternative to macrolides for treatment of presumed Rhodococcus equi pneumonia in foals. J Vet Intern Med 2015 May-Jun;29(3):932-9.
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- Willsie-Ediger SK, Stanford JF, Salzman GA, Bamberger DM. Spectrum of disease caused by Rhodococcus equi in human immunodeficiency virus infection: Report of a case and review of the literature. Can J Infect Dis 1990 Fall;1(3):101-7.
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