Isolates, Antimicrobial Susceptibility Profiles and Multidrug Resistance of Bacteria Cultured from Pig Submissions in New Zealand

Data on the scope of bacterial pathogens present and the frequency of antimicrobial resistance (AMR) in New Zealand’s pigs are limited. This study describes bacterial isolates, antimicrobial susceptibility data, and multidrug resistance (MDR; resistance to ≥3 antimicrobial classes) from New Zealand pig submissions. Porcine test data from June 2003 to February 2016 were obtained from commercial veterinary pathology laboratory records. In total, 470/477 unique submissions resulted in bacterial growth, yielding 779 isolates. Sample type was recorded for 360/477 (75.5%); lung (79/360; 21.9%), faecal (61/360; 16.9%) and intestinal (45/360; 12.5%) were most common. The most common isolates were <i>Escherichia coli</i> (186/779, 23.9%), <i>Actinobacillus pleuropneumoniae</i> (43/779; 5.5%), <i>Streptococcus suis</i> (43/779; 5.5%), unidentified <i>Campylobacter</i> spp. (38/779; 4.9%), alpha haemolytic <i>Streptococci</i> (32/779; 4.1%), coagulase negative <i>Staphylococcus</i> spp. (26/779; 3.3%), and <i>Pasteurella multocida</i> (25/779; 3.2%). Susceptibility results were available for 141/779 (18.1%) isolates from 62/470 (13.2%) submissions. Most were susceptible to trimethoprim-sulphonamide (75/81; 92.6%), but fewer were susceptible to penicillin (37/77; 48.1%), tilmicosin (18/43; 41.9%), or tetracyclines (41/114; 36.0%). No susceptibility data were available for <i>Salmonella</i> spp., <i>Campylobacter</i> spp., or <i>Yersinia</i> spp. isolates. MDR was present in 60/141 (42.6%) isolates. More data on sample submission drivers, antimicrobial drug use, and susceptibilities of important porcine bacterial isolates are required to inform guidelines for prudent antimicrobial use, to reduce their prevalence, human transmission, and to minimise AMR and MDR.