Antimicrobial resistance, biofilm synthesis and virulence genes in Salmonella isolated from pigs bred on intensive farms

Abstract

Salmonella is the second cause of food-borne infection in humans in the USA and Europe. Pigs represent the second most important reservoir for the pathogen and the consumption of pork meat is a major risk factor for human salmonellosis. Here, we evaluated the virulence patterns of eleven Salmonella isolated from pigs (carcasses and faces) bred in intensive farms in the north of Italy. The two serotypes identified were S. Typhimurium and its monophasic variant 1,4,5,12:i:-. None of the isolates was an ESBL producer, as confirmed also by PCR. However, the presence of a multi-drug resistant pattern was evident, with all the isolates being resistant to at least to five antimicrobial agents belonging to various classes. Moreover, six out of eleven isolates showed important resistance profiles, such as resistance against colistin and ciprofloxacin, with nine to twelve recorded resistances. The isolates were negative for the biofilm synthesis test, while four different virulotypes were characterized. All the isolates showed the presence of invA, hilA, stn, ssrA, sipC. One sample also harbored ssaR and spvC genes. One strain was positive for all the virulence genes tested and was resistant to 12 antimicrobial agents. The present study contributes new data to the surveillance program for antibiotic resistance. Furthermore, the presence of eleven highly virulent isolates poses concern for human health in relation to their diffusion in the environment.

Characterization of Salmonella spp. Isolated From Poultry Giblets, Calves and Human Beings in Menoufiya Governorate

“…InvA is a putative inner membrane component of SPI-1, essential for entry into epithelial cells, and it is a specific target gene for confirmation of Salmonella spp. , while hilA is a transcriptional activator essential for the regulation of the invasion process , All the Salmonella tested were positive for both invA and hilA genes, show the virulence potential of the strains in relation to their ability to be invasive after the attachment to the intestinal epithelium (Barrilli et al, 2018) and this coincides with the result in this study as invA was detected as 100% while hilA was 90.9% as in (table3) (fig.,1) and (fig.,4). This was as similar as all the isolates were positive for at least five virulence-related-genes (invA, hilA, stn, ssrA, sipC).…”

“…This was as similar as all the isolates were positive for at least five virulence-related-genes (invA, hilA, stn, ssrA, sipC). The same phenomenon has been highlighted in S. typhimurium isolated in swine, where all the strains analysed were positive for sipA, sipD, flgK, flgL,fljB, invA, sopB and sopE2 genes (Barrilli et al, 2018).…”

“…Several reports confirmed the successful detection of 100% of Salmonella species isolates from poultry using specific primers for the invA gene with no false positive or negatives (Oliveira et al, 2003;Moussa et al, 2010 andAmmar et al, 2016). While, for the intracellular survival of Salmonella is regulated by the (mgtC) genes (Zou et al, 2012), while hilA is a transcriptional activator essential for the regulation of the invasion process, all the Salmonella tested were positive for both invA and hilA genes, show the virulence potential of the strains in relation to their ability to be invasive after the attachment to the intestinal epithelium (Barrilli et al, 2018). Therefore, the objectives of this study were to investigate the potential zoonotic spread of Salmonella species isolated from animal products and calves fecal matter and in-contact human being, identify them by serotyping, in addition, using PCR to confirm the results.…”

Pathogenicity and Competitive Fitness of Salmonella enterica Serovar 4,[5],12:i:- Compared to Salmonella Typhimurium and Salmonella Derby in Swine

“…It is plausible that differences in the determinates of the ability to adhere within the gastrointestinal tract might help explain some of the differences observed in pathogenicity within the swine host. However, several genes known to be involved in virulence, including sipC which is involved in cell adhesion and invasion, sopB which promotes the influx of inflammatory cells and fluid secretion involved in diarrhea, and hilA which activates the invasion process (37), were found to be present in all isolates sequenced including S. Derby.…”

“…Additionally, a study of 133 monophasic isolates showed that the majority possessed the ability to form biofilms (35); this could enhance the in vivo survivability while reducing the effects of antimicrobials on the bacteria (35,36). Salmonella 4, [5],12:i:-also commonly possesses multiple virulence genes that may contribute to its survival within the host and environment; these genes include but are not limited to sipC which is involved in cell adhesion and invasion, sopB which promotes the influx of inflammatory cells and fluid secretion involved in diarrhea, and hilA which activates the invasion process (37). The combination of biofilm formation, presence of virulence genes involved in pathogenesis, resistance to antimicrobials, and resistance to heavy metals may all function together to provide a selective and competitive advantage to S. 4, [5],12:i:-in swine production.…”