title: Characterization of Listeria monocytogenes isolated from retail foods.
abstract: 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.
authors.affiliation: Department of Nutrition and Food Science, University of Maryland, College Park, MD 20742, USA.
authors.forename: Yifan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Emily
authors.initials: E
authors.lastname: Yeh
authors.forename: Grace
authors.initials: G
authors.lastname: Hall
authors.forename: Jennifer
authors.initials: J
authors.lastname: Cripe
authors.forename: Arvind A
authors.initials: AA
authors.lastname: Bhagwat
authors.forename: Jianghong
authors.initials: J
authors.lastname: Meng
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002645:Chickens; D003257:Consumer Product Safety; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005506:Food Contamination / Q000032:analysis*; D005838:Genotype; D006801:Humans; D008089:Listeria monocytogenes / Q000145:classification* / Q000187:drug effects / Q000302:isolation & purification*; D008460:Meat / Q000382:microbiology; D008461:Meat Products / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012703:Serotyping; D014675:Vegetables / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents