Antimicrobial resistance profiles of Listeria monocytogenes isolated from chicken meat in Fukuoka, Japan

Abstract

In this study, the antimicrobial resistance profiles of L. monocytogenes isolated from chicken meat in Fukuoka in 2017 were compared with the isolates of 2012. A total of 85 and 50 chicken meat samples, including different body parts, were collected from different supermarkets in Fukuoka in 2012 and 2017, respectively. Detection, isolation, identification, and characterization of L. monocytogenes were performed according to the conventional methods. Forty-five among 85 samples (53%) were positive for L. monocytogenes in 2012, while 12 among 50 samples in 2017 (24%) tested positive. One hundred fifty-three and 29 L. monocytogenes strains were isolated in 2012 and 2017, respectively. The serotypes of isolates in 2012 were 1/2a (21.5%), 1/2b (73.9%), 1/2c (1.5%), and 4b/4e (3.1%). In contrast, the 2017 isolates showed 1/2a (48.3%) and 1/2b (51.7%) serotypes. While all isolates in 2012 were positive for hlyA (listeriolysin O) in the PCR assay with hlyA primer set 7, only 17 hlyA positive isolates were seen in 2017. Moreover, 75 isolates with different ribotypes in 2012 and 29 isolates in 2017, respectively, were tested for antimicrobial susceptibility by broth microdilution for 18 different antimicrobial agents. Most of the 2012 and 2017 isolates displayed antimicrobial susceptibility. However, among the 2012 and 2017 isolates, 98.7% and 100% of the isolates were resistant to cefoxitin, 57.3% and 95.7% to fosfomycin, 72.0% and 82.6% to oxacillin, 8.0% and 17.4% to clindamycin, respectively. In addition, 2.7% of the isolates in 2012 were resistant to flomoxef and 4.3% of the isolates in 2017 to linezolid. Multidrug resistance (MDR) to 3 or more antimicrobials was observed in 35/75 (46.7%) isolates of 2012 and 19/23 (82.6%) in 2017. Detection of antimicrobial resistance (AMR) genes by PCR showed that the resistant isolates of 2012 were positive for mecA (96.3%) and ermC (83.3%), whereas the resistant isolates in 2017 screened positive for mecA (94.7%) and mefA (25.0%). Other cfxA, ermA, ermB, fosA, fosB, and fosC genes were absent in the PCR assay for any of the isolates. This study investigated for the first time the change in the L. monocytogenes contamination of chicken meat and antibiotic resistance of the isolated L. monocytogenes strains in Fukuoka, Japan, in the course of 5 years. Although the contamination rate of L. monocytogenes in 2017 was found to be lower than that in 2012, AMR of the isolates in 2017 was higher.