ABSTRACT
Enterococcus spp., including E. faecalis and E. faecium, pose risks to dairy farms as opportunistic pathogens. The study evaluates antimicrobial resistance (AMR) and virulence characteristics of Enterococcus spp. isolated from bovine milk. Bile esculin agar was used to assess 1471 milk samples, followed by colony identification, gram staining, catalase tests, and 45 °C incubation. PCR analysis targeted E. faecalis and E. faecium in characteristic Enterococcus spp. colonies, with MALDI-TOF used for negative samples. Multiple tests, including disk diffusion, chromogenic VRE agar for vancomycin resistance, Vancomycin Etest® for MIC determination, and PCR for virulence factors (cylA, esp, efaA, ace, asa1, gelE, and hyl genes), were performed. Out of 100 identified strains, E. durans (30.66%), E. faecium (26.28%), and E. faecalis (18.25%) were predominant. AMR in Enterococcus spp. varied, with the highest rates against rifampicin (27%), tetracycline (20%), and erythromycin (18%). Linezolid (5%), vancomycin, ciprofloxacin, and teicoplanin (3% each) had lower prevalence. E. faecium and E. faecalis showed high AMR to rifampicin, erythromycin, and tetracycline. Thirty-two strains (18.98%) grew on VRE Chromoselect agar, while 4 (2 E. faecalis and 2 E. faecium) showed vancomycin resistance by MIC values. E. faecalis carried gelE (45.5%) and asa1 (36%), and E. gallinarum had 9.1% with the asa1 gene. Detecting resistant Enterococcus in bovine milk supports control strategies for enterococci on dairy farms, highlighting AMR concerns in the food chain.
ABSTRACT
Foodborne infections caused by Salmonella have been linked to a variety of poultry products. The aim of this study was to compare the molecular profile of virulence genes considering different serotypes of Salmonella, isolates were from chicken breast sampled during the last two decades (1999 to 2010 and 2011 to 2018). The resistance to antimicrobials was also evaluated, establishing a comparative epidemiological parameter on the pathogenic potential on this bacterium over time. We tested 238 Salmonella isolates, and 18 different serotypes were observed. These being S. Enteritidis (42.3%, 58/137) and S. Ohio (28.3%, 36/137), the most frequent in the first decade; and S. Heidelberg (25.7%, 26/101) and S. Typhimurium (21.8%, 22/101), in the second. We found four (1.68%) multidrug resistant isolates from the first decade and 28 (11.76%) in the second. All extended spectrum beta-lactamase (ESBL) positive isolates belonged to the S. Heidelberg serotype, and were also detected in the second decade. Considering the nine different antimicrobial classes tested, an increase in the number of resistant isolates was observed over time: from five classes with resistant isolates in the first decade to eight classes in the second, with cefotaxime being the antimicrobial with the highest number of resistant isolates in both decades. All isolates (100%) presented the invA, sitC and tolC genes. In sequence, the most frequent genes were flgL (99.6%), sopB (98.3%), flgK (97.9%), fljB (96.6%), sipA (94.9%), sipB (88.6%), sifA (86.4%), sipD (66.1%), ssaR (51.3%), sopD (37.3%) and spvB (34.3%) was the least frequent; and 13 isolates showing all 14 virulence genes investigated. The ability of these isolates to resist certain antimicrobials, and to express genes encoding virulence factors, reinforce their marked pathogenic potential; while the possibility to trigger diseases in humans through the food chain is a serious public health threat through.
