title: Expression of multidrug resistance efflux pump genes in clinical and environmental isolates of Staphylococcus aureus.
abstract: Increased expression of multidrug resistance efflux pump (MDR-EP) genes in clinical isolates of Staphylococcus aureus occurs frequently, but its temporal and geographic variability is unknown. Such strains may contaminate the hospital environment, posing an infection control problem. Nearly 700 clinical isolates from different geographic locales as well as 91 environmental isolates recovered from two Detroit hospitals were studied. Ethidium bromide (EtBr) minimum inhibitory concentration (MIC), quantitative expression of all characterised chromosomal MDR-EP genes, and the presence of qacA/B and smr were determined for all strains. In addition, for norA- and/or mepA-overexpressing strains, the spa type was established. MDR-EP gene overexpression varied temporally and geographically, and overexpressing strains were present in the hospital environment. Increased expression of norA was associated with meticillin resistance and spa type t002, a rare type among control strains, consistent with widespread dissemination of a norA-overexpressing, meticillin-resistant S. aureus (MRSA) clone. Clonal spread also played a role for spa type t008, mepA-overexpressing, meticillin-susceptible strains. An EtBr MIC of ≤12.5 μg/mL was highly specific (>90%) in identifying strains lacking MDR-EP gene overexpression.
authors: Department of Medicine, Division of Infectious Diseases, Wayne State University School of Medicine, Detroit, MI 48201, USA.
authors: Christos
authors: C
authors: Kosmidis
authors: Bryan D
authors: BD
authors: Schindler
authors: Pauline L
authors: PL
authors: Jacinto
authors: Diixa
authors: D
authors: Patel
authors: Karanpreet
authors: K
authors: Bains
authors: Susan M
authors: SM
authors: Seo
authors: Glenn W
authors: GW
authors: Kaatz
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D001693:Biological Transport, Active; D002170:Canada; D016000:Cluster Analysis; D024901:Drug Resistance, Multiple, Bacterial; D004783:Environmental Microbiology; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005838:Genotype; D006761:Hospitals; D006801:Humans; D026901:Membrane Transport Proteins / Q000096:biosynthesis* / Q000235:genetics; D008826:Microbial Sensitivity Tests; D060888:Real-Time Polymerase Chain Reaction; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins