Dataset Information

Association of norB overexpression and fluoroquinolone resistance in clinical isolates of Staphylococcus aureus from Korea.

ABSTRACT: Although the prevalence of fluoroquinolone resistance among methicillin-resistant Staphylococcus aureus (MRSA) is known to be higher than in methicillin-susceptible S. aureus (MSSA), the reasons have never been identified.We randomly selected 115 isolates of S. aureus collected from 10 different hospitals in Korea between June 2009 and May 2011. To investigate the difference in fluoroquinolone resistance mechanisms between MRSA and MSSA, we evaluated gyrA and parC mutations and the relative expression of the multidrug efflux pump genes norA, norB and norC.All 62 ciprofloxacin-resistant S. aureus had either gyrA or parC mutations. The S84L mutation of gyrA (59/62, 95.2%) and the S80F mutation of parC (61/62, 98.4%) were the most common. Fifty-eight (93.6%) strains had both the S84L mutation of gyrA and the S80F mutation of parC. Among the 115 isolates, norB overexpression was the most common, occurring in 49 (42.6%) strains. There were only two (1.7%) strains with norA overexpression and none with norC overexpression. Strains overexpressing norB were more common among ciprofloxacin-resistant S. aureus (33/62, 53.2%) than ciprofloxacin-susceptible S. aureus (16/53, 30.2%) (P = 0.013). When we analysed 62 ciprofloxacin-resistant S. aureus strains, those overexpressing norB were more common in ciprofloxacin-resistant MRSA (28/46, 60.9%) than in ciprofloxacin-resistant MSSA (5/16, 31.3%) (P = 0.041).Increased expression of norB can be a factor that contributes to ciprofloxacin resistance in MRSA strains.

SUBMITTER: Kwak YG

PROVIDER: S-EPMC3820107 | biostudies-literature | 2013 Dec

REPOSITORIES: biostudies-literature

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Association of norB overexpression and fluoroquinolone resistance in clinical isolates of Staphylococcus aureus from Korea.

Kwak Yee Gyung YG Truong-Bolduc Que Chi QC Bin Kim Hong H Song Kyoung-Ho KH Kim Eu Suk ES Hooper David C DC

The Journal of antimicrobial chemotherapy 20130808 12

<h4>Objectives</h4>Although the prevalence of fluoroquinolone resistance among methicillin-resistant Staphylococcus aureus (MRSA) is known to be higher than in methicillin-susceptible S. aureus (MSSA), the reasons have never been identified.<h4>Methods</h4>We randomly selected 115 isolates of S. aureus collected from 10 different hospitals in Korea between June 2009 and May 2011. To investigate the difference in fluoroquinolone resistance mechanisms between MRSA and MSSA, we evaluated gyrA and p ...[more]

PMID: 23928023

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Project description:Biofilm-related infections remain a scourge. In an in vitro model of biofilms using Staphylococcus aureus reference strains, delafloxacin and daptomycin were found to be the most active among the antibiotics from 8 different pharmacological classes (J. Bauer, W. Siala, P. M. Tulkens, and F. Van Bambeke, Antimicrob. Agents Chemother. 57:2726-2737, 2013, doi:10.1128/AAC.00181-13). In this study, we compared delafloxacin to daptomycin and vancomycin using biofilms produced by 7 clinical strains (S. aureus epidemic clones CC5 and CC8) in order to rationalize the differences observed between the antibiotics and strains. The effects of the antibiotics on bacterial viability (resazurin reduction assay) and biomass (crystal violet staining) were measured and correlated with the proportion of polysaccharides in the matrix, the local microenvironmental pH (micro-pH), and the antibiotic penetration in the biofilm. At clinically meaningful concentrations, delafloxacin, daptomycin, and vancomycin caused a ≥25% reduction in viability against the biofilms formed by 5, 4, and 3 strains, respectively. The antibiotic penetration within the biofilms ranged from 0.6 to 52% for delafloxacin, 0.2 to 10% for daptomycin, and 0.2 to 1% for vancomycin; for delafloxacin, this was inversely related to the polysaccharide proportion in the matrix. Six biofilms were acidic, explaining the high potency of delafloxacin (lower MICs at acidic pH). Norspermidine and norspermine (disassembling the biofilm matrix) drastically increased delafloxacin potency and efficacy (50% reduction in viability for 6 biofilms at clinically meaningful concentrations) in direct correlation with its increased penetration within the biofilm, while they only modestly improved daptomycin efficacy (50% reduction in viability for 2 biofilms) and penetration, and they showed marginal effects with vancomycin. Delafloxacin potency and efficacy against biofilms are benefited by its penetration into the matrix and the local acidic micro-pH.

Dataset Information

Association of norB overexpression and fluoroquinolone resistance in clinical isolates of Staphylococcus aureus from Korea.

Publications

Association of norB overexpression and fluoroquinolone resistance in clinical isolates of Staphylococcus aureus from Korea.

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