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Effects of antibiotics on the growth and morphology of Pasteurella multocida
1Groupe de Recherche sur les Maladies Infectieuses du Porc, Faculté de Médecine Vétérinaire, Université de Montréal, Québec, Canada.
Abstract:
The effects of subminimal inhibitory concentrations (subMICs) of certain antibiotics, namely penicillin G, tetracycline and trimethoprim/sulphamethoxazole, on the growth and morphology of Pasteurella multocida were evaluated. SubMICs of penicillin markedly reduced the growth of P. multocida. Tetracycline and trimethoprim/sulphamethoxazole had no effect on its growth. SubMICs of penicillin greatly affected the morphology of P. multocida. At the highest concentrations tested (1/2 and 1/4 MIC) cells were acapsulate, and long filamentous cells (4-6 microns) were observed with some isolates. There was no correlation between the observed differences in the penicillin-binding proteins of the P. multocida isolates, and the extent of cell filamentation induced by penicillin G. SubMICs of tetracycline and trimethoprim/sulphamethoxazole did not seem to affect capsule production although filamentation was observed. Our results indicate that subMICs of penicillin can reduce growth of P. multocida. Furthermore, results also indicate that subMICs of antibiotics can affect the production of capsular material and the morphology of P. multocida.
Insights
Sub-inhibitory concentrations of penicillin G significantly inhibited Pasteurella multocida growth and altered cell morphology, causing filamentation and acapsular forms. Other tested antibiotics had minimal effects on growth or morphology.
Area of Science:
- Microbiology
- Bacteriology
- Antibiotic Resistance
Background:
- Sub-inhibitory concentrations of antibiotics can influence bacterial behavior.
- Pasteurella multocida is a significant veterinary pathogen.
- Understanding sub-inhibitory antibiotic effects is crucial for managing bacterial infections.
Purpose of the Study:
- To investigate the impact of sub-inhibitory concentrations (subMICs) of penicillin G, tetracycline, and trimethoprim/sulphamethoxazole on Pasteurella multocida growth and morphology.
- To determine if subMICs affect capsule production and cell shape in P. multocida.
Main Methods:
- Exposure of P. multocida isolates to subMICs of penicillin G, tetracycline, and trimethoprim/sulphamethoxazole.
- Evaluation of bacterial growth rates and morphological changes (filamentation, acapsular forms) using microscopy.
- Analysis of penicillin-binding proteins (PBPs) in relation to observed filamentation.
Main Results:
- SubMICs of penicillin G markedly reduced P. multocida growth.
- Penicillin G subMICs significantly altered cell morphology, inducing filamentation and acapsular cells at higher concentrations.
- Tetracycline and trimethoprim/sulphamethoxazole had no significant effect on P. multocida growth.
- Filamentation was observed with tetracycline and trimethoprim/sulphamethoxazole, but capsule production was not notably affected.
Conclusions:
- Sub-inhibitory concentrations of penicillin G can inhibit Pasteurella multocida growth.
- SubMICs of antibiotics, particularly penicillin G, can induce significant morphological changes in P. multocida, including filamentation and loss of capsule.
- These findings highlight the complex interactions between sub-inhibitory antibiotic levels and bacterial physiology, with implications for treatment and resistance development.