Extended-spectrum cephalosporin resistance and PMQR in Salmonella Heidelberg isolated from poultry farms in argentina

DOMINGUEZ JOHANA; CHACANA PABLO; HERRERA MARIANA; GUTKIND GABRIEL; MERCADO ELSA; DI CONZA JOSÉ

Boston

Congreso; ASM MICROBE 2016; 2016

American Society for Microbiology

Background: Salmonella infections are important zoonoses worldwide. Historically, S. Typhimurium and S. Enteritidis have been the most prevalent serovars in both humans and poultry but in the last years, in Argentina S. Heildelberg (SH) has been found to be the more common serovar isolated from broilers and thus more studies are needed in order to evaluate implications that this emerging serovar. Resistance to third generation cephalosporins (TGC) and fluoroquinolone has been described in SH isolates but very little is known about the prevalent mechanisms. The aim of this study was to characterize these mechanisms, especially those encoded in plasmids, in SH isolated from broiler farms, in Argentina, between years 2010 and 2012. Methods: Susceptibility profile was analyzed in a selected group of 42 strains of SH by disk diffusion method according to CLSI recommendations. Screening for extended spectrum β-lactamases (ESBL) or plasmid AmpC β-lactamases (AmpCp) were conducted by double disk synergy tests. ESBL and PMQR determinants were characterized by PCR using specific primers followed by sequencing. Results: Twenty-five isolates (59.5%) were found to be resistant to TGC and 13/25 of these strains were also resistant to FEP but remained susceptible to FOX. Furthermore, ESBL confirmatory test was positive for all of them. The ESBLs were characterized as members of CTX-M-14 (n = 8) and CTX-M-2 (n= 5). The remaining strains (12/25) were resistant to FOX but susceptible to FEP. Synergy was observed between PBA and both CAZ and CTX disks, thus suggesting the presence of an AmpCp. Finally, CMY-2 was identified in these 12 isolates. The most prevalent PMQR determinant detected among ESBL producers was qnrB (22/42), no association between the presence PMQR and CTX-M enzyme was found. Twelve isolates (28.5%) harbored qnrB genes, but all were sensitive to TGC. Conclusions: This is the first report of the presence of both CTX-M-14, CTX-M-2 and qnrB isolates of S. Heidelberg isolates from broiler farms in Argentina. Active monitoring programs of ATM resistance in SH strains should be considered in order to minimize the impact in both poultry and Public Health.