title: Variation in the Antimicrobial Susceptibility of Actinobacillus pleuropneumoniae Isolates in a Pig, Within a Batch of Pigs, and Among Batches of Pigs from One Farm.
abstract: Antimicrobial resistance in bacterial porcine respiratory pathogens has been shown to exist in many countries. However, little is known about the variability in antimicrobial susceptibility within a population of a single bacterial respiratory pathogen on a pig farm. This study examined the antimicrobial susceptibility of Actinobacillus pleuropneumoniae using multiple isolates within a pig and across the pigs in three different slaughter batches. Initially, the isolates from the three batches were identified, serotyped, and subsample genotyped. All the 367 isolates were identified as A. pleuropneumoniae serovar 1, and only a single genetic profile was detected in the 74 examined isolates. The susceptibility of the 367 isolates of A. pleuropneumoniae to ampicillin, tetracycline and tilmicosin was determined by a disc diffusion technique. For tilmicosin, the three batches were found to consist of a mix of susceptible and resistant isolates. The zone diameters of the three antimicrobials varied considerably among isolates in the second sampling. In addition, the second sampling provided statistically significant evidence of bimodal populations in terms of zone diameters for both tilmicosin and ampicillin. The results support the hypothesis that the antimicrobial susceptibility of one population of a porcine respiratory pathogen can vary within a batch of pigs on a farm.
authors.affiliation: 1 School of Veterinary Science, The University of Queensland , Gatton, Queensland, Australia .
authors.forename: Denise Ann E
authors.initials: DA
authors.lastname: Dayao
authors.affiliation: 2 Portec Veterinary Services , Welshpool, Western Australia , Australia.
authors.forename: Susan
authors.initials: S
authors.lastname: Dawson
authors.affiliation: 3 Department of Agriculture Fisheries and Forestry, EcoSciences Precinct , Dutton Park, Queensland, Australia .|4 School of Agriculture and Food Sciences, The University of Queensland , St. Lucia, Queensland, Australia .
authors.forename: Marco Jean-Paul
authors.initials: MJ
authors.lastname: Kienzle
authors.affiliation: 1 School of Veterinary Science, The University of Queensland , Gatton, Queensland, Australia .
authors.forename: Justine S
authors.initials: JS
authors.lastname: Gibson
authors.affiliation: 5 The University of Queensland , Queensland Alliance for Agriculture and Food Innovation, EcoSciences Precinct, Dutton Park, Queensland, Australia .
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Blackall
authors.affiliation: 5 The University of Queensland , Queensland Alliance for Agriculture and Food Innovation, EcoSciences Precinct, Dutton Park, Queensland, Australia .
authors.forename: Conny
authors.initials: C
authors.lastname: Turni
mesh_terms: D000189:Actinobacillus Infections / Q000382:microbiology* / Q000662:veterinary*; D016977:Actinobacillus pleuropneumoniae / Q000187:drug effects*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D005838:Genotype; D008168:Lung / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D011001:Pleuropneumonia / Q000382:microbiology / Q000662:veterinary; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents