Swine enteric colibacillosis: diagnosis, therapy and antimicrobial resistance

Abstract

Intestinal infection with enterotoxigenic Escherichia coli (ETEC) is an important disease in swine resulting in significant economic losses. Knowledge about the epidemiology, the diagnostic approach and methods of control are of fundamental importance to tackle the disease. The ETEC causing neonatal colibacillosis mostly carry the fimbriae F4 (k88), F5 (k99), F6 (987P) or F41, while the ETEC of post-weaning diarrhoea carry the fimbriae F4 (k88) and F18. These fimbriae adhere to specific receptors on porcine intestinal brush border epithelial cells (enterocytes), starting the process of enteric infection. After this colonization, the bacteria produce one or more enterotoxins inducing diarrhoea, such as the heat stable toxin a (STa), the heat stable toxin b (STb), and the heat labile toxin (LT). A role in the pathogenesis of the disease was demonstrated for these toxins. The diagnosis of enteric colibacillosis is based on the isolation and quantification of the pathogenic E.coli coupled with the demonstration by PCR of the genes encoding for virulence factors (fimbriae and toxins). The diagnostic approach to enteric colibacillosis must consider the differential diagnosis and the potential different causes that can be involved in the outbreak.Among the different methods of control of colibacillosis, the use of antimicrobials is widely practiced and antibiotics are used in two main ways: as prophylactic or metaphylactic treatment to prevent disease and for therapeutic purposes to treat diseased pigs.An accurate diagnosis of enteric colibacillosis needs an appropriate sampling for the isolation and quantification of the ETEC responsible for the outbreak by using semi-quantitative bacteriology. Definitive diagnosis is based on the presence of characteristic lesions and results of bacteriology along with confirmation of appropriate virulence factors to identify the isolated E.coli. It is important to confirm the diagnosis and to perform antimicrobial sensitivity tests because antimicrobial sensitivity varies greatly among E. coli isolates. Growing concern on the increase of antimicrobial resistance force a more rational use of antibiotics and this can be achieved through a correct understanding of the issues related to antibiotic therapy and to the use of antibiotics by both practitioners and farmers.

Phenotypic antimicrobial resistance in Escherichia coli strains isolated from swine husbandries in North Western Germany – temporal patterns in samples from laboratory practice from 2006 to 2017

“…Due to high standardisation of the routine susceptibility testing of isolates throughout the years, an information bias can be ignored in this study. Although E. coli strains analysed in this study were considered to be responsible for the disease picture, a clear microbiological differentiation between commensal and pathogenic E. coli strains is not possible [31,32]. In this study, assessing analysed E. coli strains as pathogenic was based on clinical and pathological observations as well as quantification of growth and phenotype of cultured E. coli strains.…”

Prevalence and characterization of virulence genes in Escherichia coli isolated from piglets suffering post‐weaning diarrhoea in Shandong Province, China

“…The frequency of different virotypes (with different adhesins) is mainly mediated by the different specific receptors on porcine intestinal brush border epithelial cells (enterocytes). These receptors change from pigs depending on the age (Luppi, ) and infection with ETEC carrying the F5, F6 or F41 fimbriae, occurs in pigs less than 2 weeks of age (Nagy & Fekete, ). Another possible explanation is that in Shandong Province of China, inactivated vaccines for sows have been used widely, and these vaccines contain E. coli whole cells with F4 and F18 (Chen & He, ), which may have decreased the frequency of F4 and F18 and caused the emergence of new adhesin antigens such as F5, F6 and F41 (Do et al, , ).…”

“…It has been reported that AIDA‐I is related with ETEC strains isolated from weaned pigs with PWD, but its role in colibacillosis in pigs is needed to be elucidated (Luppi, ). Both AIDA‐I (33/166, 19.9％) and paa (27/166, 16.3％) were commonly observed in this study.…”

Profiles of virulence genes in enterotoxigenic Escherichia coli isolates from suckling piglets in Serbia

“…The same toxin has previously been identified within enteroaggregative E. coli strains responsible for diarrhoea in humans (22). Enterotoxins stimulate the intestinal epithelium cells to secrete water and electrolytes into the intestinal lumen, thus reducing absorption, which results in diarrhoea (14,16).…”

“…Important factors leading to diarrhoea in piglets are the presence of enterotoxigenic E. coli strains in the small intestine and the absence of antibodies against E. coli adhesins in the colostrum of sows. E. coli from the environment colonize newborn piglets by the oral route, thus transferring pathogens to naive animals (14,17). The presence of neonatal colibacillosis is quite common in Serbia.…”