Effects of sub-minimum inhibitory concentration antibiotic levels and temperature on growth kinetics and outer membrane protein expression in Mannheimia haemolytica and Haemophilus somnus |
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| Authors: | Brenda Y. Reeks Franklin R. Champlin Daniel B. Paulsen Daniel W. Scruggs Mark L. Lawrence |
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| Affiliation: | College of Veterinary Medicine, Mississippi State University, Mississippi 39762, USA. |
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| Abstract: | The objective of this study was to determine the effects of sub-minimum inhibitory concentrations (sub-MICs) of 2 veterinary antibiotic preparations, chlortetracycline (CTC) and chlortetracycline-sulfamethazine (CTC + SMZ), on growth kinetics and outer membrane protein expression in Mannheimia haemolytica and Haemophilus somnus at normal and febrile body temperatures. Sub-minimum inhibitory concentrations of both antibiotics reduced the growth rates of M. haemolytica and H. somnus. Growth of both species was not inhibited when grown at 41 degrees C compared to 37 degrees C. There was no detectable consistent effect of antibiotic or temperature on outer membrane protein expression for either species. Our study indicates that sub-MIC levels of CTC and CTC + SMZ markedly impair growth of clinical M. haemolytica and H. somnus isolates, potentially allowing more effective host clearance during infection. |
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