Prevalence of qnrS-positive Escherichia coli from chicken in Thailand and possible co-selection of isolates with plasmids carrying qnrS and trimethoprim-resistance genes under farm use of trimethoprim

Abstract

One hundred and twenty chicken samples from feces (n = 80), the carcass surface at slaughter at 2 meat chicken farms (n = 20), and retail chicken meat from 5 markets (n = 20) collected during 2018 and 2019 were examined for the prevalence of plasmid-mediated quinolone resistance ( PMQR ) in Escherichia coli . We detected qnrS -positive E. coli in a total of 74 samples from feces (n = 59), the carcass surface (n = 7), and retail meat (n = 8). These 74 qnrS -positive isolates were tested for antimicrobial susceptibility to determine the minimum inhibitory concentrations ( MICs ) of certain antimicrobials and genetically characterized. Ampicillin-resistance accounted for 71 of the 74 isolates (96%), followed by resistance to oxytetracycline (57/74; 77%), enrofloxacin ( ERFX ) (56/74; 76%), sulfisoxazole ( SUL ) (56/74; 76%), trimethoprim ( TMP ) (49/74; 66%), and dihydrostreptomycin (48/74; 65%). All farm-borne SUL- and TMP-resistant isolates except one were obtained from samples from farm A where a combination of sulfadiazine and TMP was administered to the chickens. Concentrations of ERFX at which 50 and 90% of isolates were inhibited were 2 μg/mL and 32 μg/mL, respectively. Diverse pulsed-field gel electrophoresis ( PFGE ) patterns of Xba I-digested genomic DNA were observed in the qnrS -positive isolates from fecal samples. Several isolates from feces and the carcass surface had identical Xba I-digested PFGE patterns. S1-nuclease PFGE and Southern blot analysis demonstrated that 7 of 11 dfrA13 -positive fecal isolates carried both the qnrS and dfrA13 genes on the same plasmid, and 2 of 3 dfrA1 -positive isolates similarly carried both qnrS and dfrA1 on the same plasmid, although the PFGE patterns of Xba I-digested genomic DNA of the isolates were different. These results suggest that the qnrS gene is prevalent in chicken farms via horizontal transfer of plasmids and may partly be co-selected under the use of TMP.

Transferable mechanisms of quinolone resistance are more frequent among enterotoxigenic Escherichia coli isolates displaying low-level quinolone resistance

“…Regarding present isolates, quinolones are not used in the treatment of children infections, thereby ETEC have a limited exposure to quinolones, and the presence of mechanisms leading to low-levels of quinolone resistance with a low impact on bacterial fitness might be a good evolutive strategy. Furthermore, the use of other antimicrobial agents might favour the co-selection of genetic structures (Vien et al, 2012;Murase et al, 2022).…”

Phenotypic and Genotypic Characterization of Multidrug-Resistant Enterobacter hormaechei Carrying qnrS Gene Isolated from Chicken Feed in China

“…They suggested that fecal excretion is one of the reasons for the prevalence of MDR bacteria. The PMQR gene qnrS is prevalent in chicken feces ( 22 , 37 , 38 ). The qnrS gene was also found in the chicken feed ( 22 ).…”

Occurrence of ciprofloxacin resistance, plasmid-mediated quinolone resistance genes and virulence factors in Salmonella enterica serovar Enteritidis isolated from broilers in Thailand isolated from broilers in Thailand

“…The final volume of each reaction mixture was at 25 μL containing 12.5 μL of 2× GoTaq ® Green Master Mix (Promega, USA), 0.2 μM of each primer for each gene, and 2 μL of extracted DNA. No template DNA was included as a negative control and DNA of Escherichia coli containing PMQR genes was included as a positive control (Murase et al, 2022). PCR products were separated by electrophoresis with 1.5% agarose gel in 1×TBE buffer and were visualized under UV light using a gel documentation system (Bio-Rad, USA).…”