Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/5/2015
Publication Date: 5/30/2015
Citation: Brunelle, B.W., Bearson, S.M., Bearson, B.L. 2015. The effect of antibiotics on swimming and swarming motility of multidrug-resistant Salmonella enterica serovar Typhimurium [abstract]. 115th General Meeting of the American Society for Microbiology, May 30-June 2, 2015, New Orleans, Louisians. p. 199.
Technical Abstract: Motile bacteria can employ one or more different strategies to move, including swimming, swarming, twitching, gliding, sliding, and darting. Swimming is considered the movement of individual bacteria through a liquid or semi-solid medium, while swarming is the concerted movement of a group of bacteria across a surface. In many pathogenic bacteria, the motility phenotype is considered a virulence factor. Swimming and swarming motility by Salmonella is flagella-dependent, and motility, as well as the flagella itself, is associated with virulence. In Salmonella, motility and a Type III Secretion System required for cellular invasion are co-regulated. Given the clinical relevance of multidrug-resistant (MDR) Salmonella, we tested the effect various antibiotics had on the motility of such isolates. We examined six MDR Salmonella enterica serovar Typhimurium isolates that encoded antibiotic-specific resistance genes to chloramphenicol, kanamycin, streptomycin, and tetracycline. We performed phenotypic assays for swimming and swarming in response to several sub-inhibitory concentrations of each antibiotic. Chloramphenicol and tetracycline decreased both swimming and swarming, but the reduction in swarming was greater than swimming at the corresponding antibiotic concentrations. Conversely, kanamycin and streptomycin reduced bacterial swimming while having comparatively little effect on swarming. In fact, kanamycin was shown to significantly increase the ability of one isolate to swarm. Overall, this work established that the effect antibiotics have on bacterial motility for several MDR S. Typhimurium isolates is dependent on isolate, type of motility, antibiotic, and antibiotic concentration. Further elucidation of the mechanism(s) responsible for the observed differences in motility, especially the kanamycin-enhanced swarming, will assist in understanding how various antibiotics can either positively or negatively regulate and affect this Salmonella virulence factor.