Virulence genes of Escherichia coli isolates from milk and vaginal swabs of sows associated with post-partum dysgalactia syndrome

Abstract

The aim of this study was to identify the presence of virulence genes of Escherichia coli (E. coli) isolates from vaginal and milk samples associated with post-partum dysgalactia syndrome (PDS) in farmed sows. Two hundred and two sows from five commercial pig farms were clinically inspected for PDS 12–24 h after farrowing. Sows were defined as PDS-affected (PDSA) if they showed pathological vulvar discharge or mastitis followed by one or more clinical signs such as fever, anorexia and altered piglet behaviour. Milk samples and vaginal swabs for bacteriological testing were taken from PDSA (n = 47) and PDS-unaffected (PDSU, n = 155). In total, 96 isolates of E. coli were tested by multiplex polymerase chain reaction (mPCR) for the presence of virulence genes related to specific pathogen strains. Virulence genes associated with extraintestinal pathogenic E. coli (ExPEC) were the most prevalent among all tested E. coli isolates (92.6%). The most dominant among all E. coli isolates was Type 1 fimbrial (fimC) gene (90.6%), with the prevalence of 92.38% in PDSA and 94.4% in PDSU sows. There was no significance in the prevalence of virulence genes in milk samples between sows. The increased serum survival (iss) gene was significantly more prevalent (p < 0.05) in vaginal swabs of PDSA sows compared to PDSU sows. The multivariable logistic regression model showed that lower parity sows and the presence of iss and heat-stable cytotoxin associated with enteroaggregative E. coli (astA) genes were correlated (p < 0.001) with the occurrence of PDS. Lower parity sows vaginaly infected with E. coli associated with certain ExPEC strains are at higher risk of developing PDS. Sows with positive vaginal swabs for E. coli and iss gene early after parturition were associated with PDS.