title: Ecology of antibiotic resistance genes: characterization of enterococci from houseflies collected in food settings.
abstract: In this project, enterococci from the digestive tracts of 260 houseflies (Musca domestica L.) collected from five restaurants were characterized. Houseflies frequently (97% of the flies were positive) carried enterococci (mean, 3.1 x 10(3) CFU/fly). Using multiplex PCR, 205 of 355 randomly selected enterococcal isolates were identified and characterized. The majority of these isolates were Enterococcus faecalis (88.2%); in addition, 6.8% were E. faecium, and 4.9% were E. casseliflavus. E. faecalis isolates were phenotypically resistant to tetracycline (66.3%), erythromycin (23.8%), streptomycin (11.6%), ciprofloxacin (9.9%), and kanamycin (8.3%). Tetracycline resistance in E. faecalis was encoded by tet(M) (65.8%), tet(O) (1.7%), and tet(W) (0.8%). The majority (78.3%) of the erythromycin-resistant E. faecalis isolates carried erm(B). The conjugative transposon Tn916 and members of the Tn916/Tn1545 family were detected in 30.2% and 34.6% of the identified isolates, respectively. E. faecalis carried virulence genes, including a gelatinase gene (gelE; 70.7%), an aggregation substance gene (asa1; 33.2%), an enterococcus surface protein gene (esp; 8.8%), and a cytolysin gene (cylA; 8.8%). Phenotypic assays showed that 91.4% of the isolates with the gelE gene were gelatinolytic and that 46.7% of the isolates with the asa1 gene aggregated. All isolates with the cylA gene were hemolytic on human blood. This study showed that houseflies in food-handling and -serving facilities carry antibiotic-resistant and potentially virulent enterococci that have the capacity for horizontal transfer of antibiotic resistance genes to other bacteria.
authors.affiliation: Department of Entomology, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: Lilia
authors.initials: L
authors.lastname: Macovei
authors.forename: Ludek
authors.initials: L
authors.lastname: Zurek
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001483:Base Sequence; D017931:DNA Primers; D024881:Drug Resistance, Bacterial; D016983:Enterococcus / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification*; D013293:Enterococcus faecalis / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D005516:Food Microbiology; D006793:Houseflies / Q000382:microbiology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D011110:Polymorphism, Genetic
chemical_list: D000900:Anti-Bacterial Agents; D017931:DNA Primers