Detection of Extended Spectrum Beta-Lactamases Among Enterobacteriaceae strains isolated from pigs

Brazil has emerged as a leading global exporter of pork, occupying the fourth position. In this regard, the high amount of antimicrobial agents used in intensive systems of animal production has been pointed as a factor of selection and persistence of resistant bacteria. Thus, the aim of this study was evaluated the presence of Extended-Spectrum Beta-lactamases-producing (ESBL) gram-negative bacteria in swine Brazilian farms.

In 2012, 400 fecal swabs collected from nursing (40 days) and finisher (90 days) pigs, male and female, from 33 farms located in seven Brazilian states were screened for ceftiofur-resistant enterobacterial strains. Firstly, the swabs were plated in MacConkey agar supplemented with ceftiofur 2 µg/mL. Next, the isolates were identified by MALDI-TOF MS and the resistance profile was determined by agar and/or microdilution method. The presence of ESBL genes was examined by PCR. Finally, the clonal relatedness was evaluated by ERIC-PCR.

A total of 400 healthy animals were evaluated regarding the presence of bacterial producers of ESBL, being isolated 66 ESBL-positive strains. Escherichia coli grouped 51 isolates carrying bla_ESBL genes (CTX-M-2, CTX-M-15 and CTX-M-8), followed by four CTX-M-15 producing Klebsiella pneumoniae isolates. The remaining ESBL producers were Salmonella enterica (2), Pseudomonas aeruginosa (3), Morganella morganii (1), Proteus mirabilis (4) and Enterobacter cloacae (1). All strains isolated showed high MICs to ceftiofur (MIC≥256 mg/L), cefotaxima (MIC≥128 mg/L) and ceftriaxona (MIC≥256 mg/L). ERIC-PCR revealed the multiclonal dissemination of ESBL producers, suggesting the spread of bla_CTX-M-type-carrying plasmids. The overall prevalence of ESBL producers were 16.5% (66/400), but the Minas Gerais state showed concentered 54% of CTX-M+ strains, suggesting a local challenge in production practices. In fact, ESBL production has been widely reported in our country among community and hospital settings. Of great interest, we report the emergence of CTX-M-like encoding genes in food-producing swine and for the first time, the presence of CTX-M-15+ Klebsiella pneumoniae in Brazilian animal production.

The surveillance of antimicrobial resistant phenotypes in food-producing animals must be continuous in order to adopt measures to prevent their dissemination in the farms and their release into human population, such as the rational use of antimicrobials, administration of narrow spectrum drugs always is possible, strict sanitary measures and disinfection of farms with detected presence of ESBL producers.

Disclosure of Interest: None Declared.