Evidence of antimicrobial and disinfectant resistance in a remote, isolated wild pig population.

The spread of antimicrobial resistant E. coli within the environment is a global concern. Wildlife such as feral pigs have been identified as a possible reservoir of antimicrobial resistant bacteria. A cross-sectional survey of free-ranging, feral pigs within the Kimberley region of northwestern Australia was conducted to estimate the prevalence of antimicrobial and disinfectant resistant E. coli in this population. Of the 493 faecal samples collected, 115 E. coli isolates were randomly selected and their identity confirmed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). Isolates were screened for susceptibility to 14 veterinary antimicrobials (including antimicrobials not permitted for use in Australia) using MIC broth microdilution using Sensititre™ (BOPO6F) and breakpoints according to CLSI and EUCAST guidelines. Isolates also underwent disinfectant susceptibility testing to six disinfectants at their recommended concentration for use as well as at a twofold dilution, based on methods adapted from the CLSI agar plate dilution method. A moderate prevalence of resistance was observed to sulfadimethoxine (50.4%; 58/115) and florfenicol (27.0%; 31/115). A low prevalence of resistance was estimated to chlortetracycline (5.2%; 6/115) and multi-drug resistance was only identified in 1.7% (2/115) of E.coli isolates tested. Isolates were susceptible to five of the six disinfectants screened. Feral pigs could potentially act as a reservoir of antimicrobial resistance in the environment with possible implications for domestic livestock. The role that feral pigs might play in transmission of antimicrobial resistance requires further investigation, and the occurrence of resistance in such isolated populations needs to be considered when attempting to infer source attribution of antimicrobial resistance in livestock and human populations.

Bayesian Network analysis of piglet scours.

Diarrhoeal disease (scours) in piglets, often associated with enterotoxigenic Escherichia coli (ETEC), is a substantial financial burden to the pig industry worldwide. Previous research has not explicitly examined the relationships between farm, pen and microbiological factors. Here we present a state of the art analysis to reveal empirical indirect - as well as direct - associations between management factors as putative risks for scours in pre- and post-weaned piglets. A Bayesian Network is constructed to identify the optimal structural model describing the relationships between risk factors. An additive model is then built to estimate more epidemiologically familiar odds ratios. Farm-level variance dominates the model, making many pen-level associations null. However, there is evidence that pre-weaning scours are less likely on farms with <400 sows (0.14, 0.03-0.50). Our results strongly suggest that smaller production units (piglets/pen) could reduce the incidence of scours in piglets. There is also some evidence that ownership of other livestock is a potential risk factor for pre-weaning scours, although this was observed only at one farm. Future research should be directed at better understanding the role of herd size and investigating the relationship between managing other livestock and the occurrence of scours in pig herds.

Pre- and post-weaning scours in southeastern Australia: A survey of 22 commercial pig herds and characterisation of Escherichia coli isolates.

Diarrhoeal diseases in piglets caused by Escherichia coli are responsible for substantial losses each year in the Australian pig industry. A cross-sectional survey was conducted (September 2013-May 2014) across 22 commercial pig herds located in southeastern Australia: NSW (n = 9); VIC (n = 10); and SA (n = 3), to estimate the prevalence of E. coli associated diarrhoea in pre- and post-weaned piglets and to identify key risk factors associated with E. coli disease. A questionnaire on management and husbandry practices was included. Faecal samples (n = 50 from each herd) were tested for the presence of ß-haemolytic E. coli. Species level identification was confirmed by matrix-assisted laser desorption / ionisation time-of-flight mass spectrometry (MALDI-TOF/MS). ETEC virulence and enterotoxin genes (F4, F5, F6, F18, F41, STa, STb and LT) were screened for by multiplex PCR. This study assessed 60 potential risk factors for E. coli disease in post-weaned piglets, with 2 key factors-recent disease events and the presence of bedding, statistically associated with the presence of post-weaning scours. The prevalence of diarrhea in pre-weaned pens was 17% (16/93), compared with 24% (24/102) in post-weaned pens. The most prevalent ß-haemolytic ETEC genes were F18 (32%) and STb (32%) but isolates were more likely to contain F4:STb (11 of 22 herds, 23%), than F18:STb (5 of 22 herds, 6%). These findings indicate that recent disease events that have occurred within the last 12 months, and by the use of bedding or not maintaining fresh bedding can have significant impacts on piglet diarrhoea.