Lineages, Virulence Gene Associated and Integrons among Extended Spectrum β-Lactamase (ESBL) and CMY-2 Producing Enterobacteriaceae from Bovine Mastitis, in Tunisia.

Extended Spectrum Beta-Lactamase (ESBL) Enterobacteriaceae are becoming widespread enzymes in food-producing animals worldwide. Escherichia coli and Klebseilla pneumoniae are two of the most significant pathogens causing mastitis. Our study focused on the characterization of the genetic support of ESBL/pAmpC and antibiotic resistance mechanisms in cefotaxime-resistant (CTX R ) and susceptible (CTX S ) Enterobacteriaceae isolates, recovered from bovine mastitis in Tunisia, as well as the analyses of their clonal lineage and virulence-associated genes. The study was carried out on 17 ESBL/pAmpC E. coli and K. pneumoniae and 50 CTX S   E. coli . Detection of resistance genes and clonal diversity was performed by PCR amplification and sequencing. The following β-lactamase genes were detected: bla CTX-M-15 ( n = 6), bla CTX-M-15 + bla OXA-1 (2), bla CTX-M-15 + bla OXA-1 + bla TEM-1b (2), bla CTX-M-15 + bla TEM-1b (4), bla CMY-2 (3). The MLST showed the following STs: ST405 ( n = 4 strains); ST58 ( n = 3); ST155 ( n = 3); ST471 ( n = 2); and ST101 ( n = 2). ST399 ( n = 1) and ST617 ( n = 1) were identified in p(AmpC) E. coli producer strains. The phylogroups A and B1 were the most detected ones, followed by the pathogenic phylogroup B2 that harbored the shigatoxin genes stx1 / stx2 , associated with the cnf , fimA , and aer virulence factors. The qnrA / qnrB , aac(6')-Ib-cr genes and integrons class 1 with different gene cassettes were detected amongst these CTX R / S isolated strains. The presence of different genetic lineages, associated with resistance and virulence genes in pathogenic bacteria in dairy farms, may complicate antibiotic therapies and pose a potential risk to public health.