Evaluation of the impact of antimicrobial use protocols in PRRS virus infected swine on phenotypic antimicrobial resistance patterns

Appl Environ Microbiol. 2021 Oct 13:AEM0097021. doi: 10.1128/AEM.00970-21. Online ahead of print.ABSTRACTA longitudinal study was conducted to assess the impact of different antimicrobial exposures of nursery-phase pigs on patterns of phenotypic antimicrobial resistance in fecal indicator organisms throughout the growing phase. Based on practical approaches used to treat moderate to severe PRRSV-associated secondary bacterial infections, two antimicrobial protocols of differing intensity of exposure [44.1 and 181.5 animal-treatment days per 1000 animal days at risk (ATD)] were compared with a control group with minimal antimicrobial exposure (2.1 ATD). Litter-matched pigs (n = 108) with no prior antimicrobial exposure were assigned randomly to the treatment groups. Pen fecal samples were collected nine times during the wean-to-finish period and cultured for Escherichia coli and Enterococcus spp. Antimicrobial susceptibility testing was conducted using NARMS gram-negative and gram-positive antibiotic panels. Despite up to 65-fold difference in ATD, few and modest differences were observed between groups and over time. Resistant patterns at marketing overall remained similar to those observed at weaning, prior to any antimicrobial exposures. Those differences observed could not readily be reconciled with the patterns of antimicrobial exposure. Resistance of E. coli to streptomycin was higher in the group exposed to 44.1 ATD, but no aminoglycosides were used. In all instances wh...
Source: Applied and Environmental Microbiology - Category: Microbiology Authors: Source Type: research