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Antimicrobial Resistance and Resistance Genes in Aerobic Bacteria Isolated from Pork at Slaughter

Li, Lili, Olsen, Rikke Heidemann, Ye, Lei, Yan, He, Nie, Qing, Meng, Hecheng, Shi, Lei
Journal of food protection 2016 v.79 no.4 pp. 589-597
Acinetobacter baumannii, Acinetobacter johnsonii, Aeromonas hydrophila, Escherichia coli, Gram-negative bacteria, Gram-positive bacteria, Klebsiella oxytoca, Lactococcus garvieae, Lactococcus lactis, Macrococcus caseolyticus, Myroides, Raoultella terrigena, Serratia marcescens, Sphingobacterium, Staphylococcus sciuri, Vibrio cincinnatiensis, aerobes, ampicillin, antibiotic resistance, cefotaxime, chloramphenicol, ciprofloxacin, genes, gentamicin, interspersed repetitive sequences, nitrofurantoin, phenotype, plasmids, pork, slaughter, tetracycline, China
The aim of this study was to investigate the phenotypic and genotypic antimicrobial resistance, integrons, and transferability of resistance markers in 243 aerobic bacteria recovered from pork at slaughter in the People's Republic of China. The organisms belonged to 22 genera of gram-negative bacteria (92.2%) and gram-positive bacteria (7.8%). High levels of resistance were detected to tetracycline, trimethoprim-sulfamethoxazole, and ampicillin (36.2 to 54.3%), and lower levels were detected to nitrofurantoin, cefotaxime, gentamicin, ciprofloxacin, and chloramphenicol (7.8 to 29.2%). Across species, genes conferring antimicrobial resistance were observed with the following frequencies: bla TEM, 40.7%; bla CMY-2, 15.2%; bla CTX-M, 11.5%; sul2, 27.2%; sul1, 14.4%; tet(A), 5.4%; tet(L), 5.4%; tet(M), 5.0%; tet(E), 3.7%; tet(C), 3.3%; tet(S), 2.5%; and tet(K), 0.8%. Various antimicrobial resistance genes were found in new carriers: bla TEM in Lactococcus garvieae, Myroides odoratimimus, Aeromonas hydrophila, Staphylococcus sciuri, Raoultella terrigena, Macrococcus caseolyticus, Acinetobacter ursingii, Sphingobacterium sp., and Oceanobacillus sp.; bla CMY-2 in Lactococcus lactis, Klebsiella oxytoca, Serratia marcescens, Acinetobacter baumannii, and Myroides phaeus; tet(L) in M. caseolyticus; sul1 in Vibrio cincinnatiensis; sul2 in Acinetobacter bereziniae, Acinetobacter johnsonii, and V. cincinnatiensis; and the class 1 integron and gene cassette aadA2 in V. cincinnatiensis. Approximately 6.6% of isolates contained class 1 integrons, and one isolate harbored class 2 integrons. Plasmid associated intI1 and androgen receptor– encoding genes were transferred into Escherichia coli J53 and E. coli DH5α by conjugation and transformation experiments, respectively. Our study highlights the importance of aerobic bacteria from pork as reservoirs for antimicrobial resistance genes and mobile genetic elements that can readily be transferred intra- and interspecies.