title: Simulated antibiotic exposures in an in vitro hollow-fiber infection model influence toxin gene expression and production in community-associated methicillin-resistant Staphylococcus aureus strain MW2.
abstract: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strain MW2 harbors a plethora of toxins to mediate its virulence. However, toxin expression and regulation with simulated clinical antimicrobial exposures are unclear. This study evaluated these relationships using an in vitro pharmacodynamic hollow-fiber infection model. Clinical doses of clindamycin, linezolid, minocycline, trimethoprim-sulfamethoxazole (SXT), and vancomycin were simulated over 72 h against MW2 in the hollow fiber model. Expression levels of lukSF-PV and enterotoxin genes sec4, sek, seq, and sel2 were quantified by real-time PCR. Panton-Valentine leukocidin (PVL) was quantified by enzyme-linked immunosorbent assay (ELISA), and cytotoxicity was determined on polymorphonuclear cells (PMNs). Vancomycin produced the maximum MW2 killing (2.53 log(10) CFU/ml) after the first dose, but the greatest sustained killing over 72 h occurred with linezolid and clindamycin. Vancomycin and minocycline induced gene upregulation from 0 to 8 h, followed by downregulation for the remaining simulation period. Clindamycin decreased gene expression in the first 24 h, followed by moderate increases (2.5-fold) thereafter. Linezolid increased gene expression 11.4- to 200.4-fold but inhibited PVL production (0.6 ± 0.3 versus 5.9 ± 0.2 μg/ml, linezolid versus control at 72 h; P < 0.05). Similar effects on PVL production occurred with clindamycin and minocycline. SXT increased PVL production at 48 h (2.8-fold) and 72 h (4.9-fold) of treatment (P < 0.05), resulting in increased PVL cytotoxicity on PMNs. Linezolid, clindamycin, and minocycline were the most effective agents on decreasing the virulence potential in CA-MRSA, notably after 8 h of treatment. SXT had minimal effects on toxin gene regulation, but it increased production and cytotoxicity of PVL toxin in the model and may enhance virulence when it is used to treat severe infections.
authors: Pharmacy Practice Division, School of Pharmacy, University of Wisconsin, Madison, Wisconsin, USA.
authors: Solen
authors: S
authors: Pichereau
authors: Madhulatha
authors: M
authors: Pantrangi
authors: William
authors: W
authors: Couet
authors: Cedric
authors: C
authors: Badiou
authors: Gerard
authors: G
authors: Lina
authors: Sanjay K
authors: SK
authors: Shukla
authors: Warren E
authors: WE
authors: Rose
mesh_terms: D000081:Acetamides / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D001427:Bacterial Toxins / Q000096:biosynthesis* / Q000235:genetics; D018929:Cell Culture Techniques; D002981:Clindamycin / Q000494:pharmacology; D017714:Community-Acquired Infections / Q000188:drug therapy / Q000382:microbiology; D004797:Enzyme-Linked Immunosorbent Assay; D005098:Exotoxins / Q000096:biosynthesis* / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007956:Leukocidins / Q000096:biosynthesis* / Q000235:genetics; D007963:Leukocytes, Mononuclear / Q000187:drug effects; D000069349:Linezolid; D016106:Methicillin Resistance; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D008911:Minocycline / Q000494:pharmacology; D008954:Models, Biological; D023303:Oxazolidinones / Q000494:pharmacology; D060888:Real-Time Polymerase Chain Reaction; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000382:microbiology; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology; D014640:Vancomycin / Q000494:pharmacology; D037521:Virulence Factors / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D000081:Acetamides; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D005098:Exotoxins; D007956:Leukocidins; D023303:Oxazolidinones; C078284:Panton-Valentine leukocidin; D037521:Virulence Factors; D002981:Clindamycin; D014640:Vancomycin; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D008911:Minocycline; D000069349:Linezolid