title: Identification of β-lactamases in human and bovine isolates of Staphylococcus aureus strains having borderline resistance to penicillinase-resistant penicillins (PRPs) with proteomic methods.
abstract: Methicillin and oxacillin-hydrolyzing enzymes of 6 borderline methicillin-resistant and 1 methicillin-resistant Staphylococcus aureus strains isolated from human clinical samples and 4 borderline methicillin-resistant S. aureus strains isolated from bovine mastitis were investigated. As previous studies suggested the involvement of an additional enzyme besides the penicillinase BlaZ in the determination of borderline resistance, we analyzed the expressed extracellular and membrane-bound β-lactamases with 2-D gel electrophoresis and mass spectrometry. Our analysis showed that the penicillin-hydrolyzing BlaZ alone was responsible for the hydrolysis of both methicillin and oxacillin. All supernatant and membrane fractions contained the same enzyme with slight sequence variations. The size and pI of the proteins were also variable, probably due to spontaneous hydrolysis and/or posttranslational modifications. Interestingly, we found also cytotoxins and other virulence factors in some nitrocefin-hydrolyzing dots, suggesting that those proteins might have a role in the reduction of local antibiotic concentration.
authors.affiliation: Department of Human Genetics, University of Debrecen, Debrecen, Hungary. kevia@freemail.hu
authors.forename: Judit Szilvia
authors.initials: JS
authors.lastname: Keseru
authors.forename: István
authors.initials: I
authors.lastname: Szabó
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Gál
authors.forename: Orietta
authors.initials: O
authors.lastname: Massidda
authors.forename: Marina
authors.initials: M
authors.lastname: Mingoia
authors.forename: Eva
authors.initials: E
authors.lastname: Kaszanyitzky
authors.forename: Szilárd
authors.initials: S
authors.lastname: Jánosi
authors.forename: Julianna
authors.initials: J
authors.lastname: Hulvely
authors.forename: Attila
authors.initials: A
authors.lastname: Csorba
authors.forename: Krisztina
authors.initials: K
authors.lastname: Buzás
authors.forename: Eva
authors.initials: E
authors.lastname: Hunyadi-Gulyás
authors.forename: Katalin F
authors.initials: KF
authors.lastname: Medzihradszky
authors.forename: Sándor
authors.initials: S
authors.lastname: Biró
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002417:Cattle; D002511:Cephalosporins / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D005260:Female; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D055624:Methicillin-Resistant Staphylococcus aureus / Q000201:enzymology / Q000302:isolation & purification; D010405:Penicillinase / Q000378:metabolism; D010406:Penicillins / Q000494:pharmacology*; D040901:Proteomics; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects / Q000201:enzymology* / Q000302:isolation & purification*; D001618:beta-Lactamases / Q000302:isolation & purification* / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D008565:Membrane Proteins; D010406:Penicillins; D010405:Penicillinase; D001618:beta-Lactamases; C021720:nitrocefin