title: Effects of sub-minimum inhibitory concentration antibiotic levels and temperature on growth kinetics and outer membrane protein expression in Mannheimia haemolytica and Haemophilus somnus.
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.
authors.affiliation: College of Veterinary Medicine, Mississippi State University, Mississippi 39762, USA.
authors.forename: Brenda Y
authors.initials: BY
authors.lastname: Reeks
authors.forename: Franklin R
authors.initials: FR
authors.lastname: Champlin
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Paulsen
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Scruggs
authors.forename: Mark L
authors.initials: ML
authors.lastname: Lawrence
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000187:drug effects* / Q000378:metabolism; D002751:Chlortetracycline / Q000494:pharmacology*; D004359:Drug Therapy, Combination; D004591:Electrophoresis, Polyacrylamide Gel / Q000662:veterinary; D015964:Gene Expression Regulation, Bacterial; D044138:Haemophilus somnus / Q000187:drug effects* / Q000254:growth & development; D007700:Kinetics; D016978:Mannheimia haemolytica / Q000187:drug effects* / Q000254:growth & development; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D013418:Sulfamethazine / Q000494:pharmacology*; D013696:Temperature
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D013418:Sulfamethazine; D002751:Chlortetracycline
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