Characterization of Listeria monocytogenes isolated from retail foods

• Published in: International journal of food microbiology 2007, Vol.113 (1), p.47-53
• Main Authors: Zhang, Yifan, Yeh, Emily, Hall, Grace, Cripe, Jennifer, Bhagwat, Arvind A., Meng, Jianghong
• Format: Article
• Language: English
• Subjects: Animals; Anti-Bacterial Agents - pharmacology; antibiotic resistance; bacterial contamination; Biological and medical sciences; chicken meat; Chickens; ciprofloxacin; Consumer Product Safety; Drug Resistance, Bacterial; Electrophoresis, Gel, Pulsed-Field; food contamination; Food Contamination - analysis; Food industries; Food microbiology; food retailing; Fresh produce; Fundamental and applied biological sciences. Psychology; genes; Genotype; Humans; Listeria monocytogenes; Listeria monocytogenes - classification; Listeria monocytogenes - drug effects; Listeria monocytogenes - isolation & purification; listeriosis; Meat - microbiology; Meat and meat product industries; Meat Products - microbiology; Microbial Sensitivity Tests; Phylogeny; Polymerase Chain Reaction; produce; public health; pulsed-field gel electrophoresis; Raw chickens; raw meat; ready-to-eat foods; Ready-to-eat meats; serotypes; Serotyping; sulfonamides; tetracycline; Vegetables - microbiology
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/j.ijfoodmicro.2006.07.010

Listeria monocytogenes isolates recovered from retail ready-to-eat (RTE) meats, raw chickens and fresh produce were characterized by serogroup identification using PCR, genotyping using pulsed-field gel electrophoresis (PFGE) and antimicrobial susceptibility testing. Five L. monocytogenes serogroups were identified. Of the 167 isolates 68 (41%) belonged to serogroup 1/2b, 3b; 53 (32%) belonged to serogroup 4b, 4d, 4e; 43 (26%) belonged to serogroup 1/2a, 3a; 2 (1.2%) belonged to serogroup 1/2c, 3c; and 1 (0.6%) belonged to serogroup 4a, 4c. PFGE generated 120 patterns which correlated well with PCR serogrouping. Most L. monocytogenes isolates were resistant to sulfonamide (73%) and some were resistant to tetracycline (8.4%) and ciprofloxacin (1.8%). Tetracycline resistance was conjugatively transferable and the tet(M) gene was identified in 14 tetracycline-resistant isolates as well as their transconjugants. These findings indicate that L. monocytogenes present in food were diverse, and that resistance to one or more antibiotics among these isolates was common. In addition, the presence of potential serotype 4b in all food categories is of public health concern, as serotype 4b has been the serotype most frequently associated with human listeriosis.