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Infect Chemother

Clinical Usefulness of Arbekacin.

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Clinical Usefulness of Arbekacin.
Infect Chemother. 2016 Mar;48(1):1-11
Authors: Lee JH, Lee CS
Abstract
Arbekacin is a broad-spectrum aminoglycoside used to treat methicillin-resist…

Detection of Carbapenemases in Clinical Enterobacteriaceae Isolates Using the VITEK AST-N202 Card.

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Detection of Carbapenemases in Clinical Enterobacteriaceae Isolates Using the VITEK AST-N202 Card.

Infect Chemother. 2015 Sep;47(3):167-74

Authors: Bae IK, Kang HK, Jang IH, Lee W, Kim K, Kim JO, Jeong SH, Lee K

Abstract
BACKGROUND: The rapid and accurate detection of carbapenemase-producing Enterobacteriaceae (CPE) in clinical microbiology laboratories is essential for the treatment and control of infections caused by these microorganisms. This study was performed to evaluate the ability of the VITEK AST-N202 card to detect CPE isolates.
MATERIALS AND METHODS: A total of 43 (Klebsiella pneumoniae, n = 37; Escherichia coli, n = 3; and Enterobacter cloacae, n = 3) CPE isolates and 79 carbapenemase-non-producing Enterobacteriaceae (CNE) isolates were included in this study. The CPE isolates harbored KPC-2 (n = 11), KPC-3 (n = 20), GES-5 (n = 5), VIM-2 (n = 2), IMP-1 (n = 1), NDM-1 (n = 2), or OXA-232 (n = 2). Of the 79 CNE isolates, eight K. pneumoniae isolates were resistant to ertapenem, imipenem, and meropenem, while the remaining 71 isolates were susceptible to the carbapenems. Antimicrobial susceptibilities were tested using the VITEK AST-N202 card, and the results were interpreted as positive when the isolates showed resistant or intermediate results. Modified-Hodge tests (MHTs) were performed using ertapenem or meropenem disks for the screening of carbapenemase production. Polymerase chain reaction (PCR) and direct sequencing were used to identify β-lactamase genes.
RESULTS: Sensitivity of MHT with ertapenem and meropenem disks for the detection of carbapenemase was 81.4% (35/43) and 81.4% (35/43), respectively, and a combination with both antibiotic disks increased the sensitivity to 88.4% (38/43). Specificity of the MHT was 100% (79/79) for the CNE isolates. Sensitivity of ertapenem, imipenem, and meropenem as assessed by the VITEK AST-N202 card was 100% (43/43), 93% (40/43), and 95.3% (41/43), respectively. Specificity (89.8%, 71/79) of the test with each carbapenem was improved to 100% (71/71) when eight carbapenem-resistant CNE isolates were excluded from the testing.
CONCLUSION: The VITEK AST-N202 card showed high sensitivity for the detection of carbapenemases in Enterobacteriaceae strains. PCR and sequencing experiments for the detection of carbapenemases are recommended when clinical Enterobacteriaceae isolates show non-susceptibility to carbapenems.

PMID: 26483990 [PubMed]

Interpretation of Epithelial Lining Fluid Concentrations of Antibiotics against Methicillin Resistant Staphylococcus aureus.

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Interpretation of Epithelial Lining Fluid Concentrations of Antibiotics against Methicillin Resistant Staphylococcus aureus.

Infect Chemother. 2014 Dec;46(4):219-25

Authors: Kiem S, Schentag JJ

Abstract
Although antibiotics whose epithelial lining fluid (ELF) concentrations are reported high tend to be preferred in treatment of pneumonia, measurement of ELF concentrations of antibiotics could be misled by contamination from lysis of ELF cells and technical errors of bronchoalveolar lavage (BAL). In this review, ELF concentrations of anti-methicillin resistant Staphylococcus aureus (MRSA) antibiotics were interpreted considering above confounding factors. An equation used to explain antibiotic diffusion into CSF (cerebrospinal fluid) was adopted: ELF/free serum concentration ratio = 0.96 + 0.091 × ln (partition coefficient / molecular weight(1/2)). Seven anti-MRSA antibiotics with reported ELF concentrations were fitted to this equation to see if their ELF concentrations were explainable by the penetration capacity only. Then, outliers were modeled under the assumption of varying contamination from lysed ELF cells (test range 0-10% of ELF volume). ELF concentrations of oritavancin, telavancin, tigecycline, and vancomycin were well described by the diffusion equation, with or without additional impact from cell lysis. For modestly high ELF/free serum concentration ratio of linezolid, technical errors of BAL should be excluded. Although teicoplanin and iclaprim showed high ELF/free serum ratios also, their protein binding levels need to be cleared for proper interpretation. At the moment, it appears very premature to use ELF concentrations of anti-MRSA antibiotics as a relevant guide for treatment of lung infections by MRSA.

PMID: 25566401 [PubMed]

In vitro Comparison of Anti-Biofilm Effects against Carbapenem-Resistant Acinetobacter baumannii: Imipenem, Colistin, Tigecycline, Rifampicin and Combinations.

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In vitro Comparison of Anti-Biofilm Effects against Carbapenem-Resistant Acinetobacter baumannii: Imipenem, Colistin, Tigecycline, Rifampicin and Combinations.

Infect Chemother. 2015 Mar;47(1):27-32

Authors: Song JY, Cheong HJ, Noh JY, Kim WJ

Abstract
BACKGROUND: Multi-drug resistant (MDR) Acinetobacter baumannii has emerged as one of the most important nosocomial pathogens. In addition to the diverse resistance mechanisms, some A. baumannii strains are known to have biofilm-producing capacity, thereby decreasing antibiotic effectiveness.
MATERIALS AND METHODS: This study was designed to assess biofilm-producing capacity of three different MDR A. baumannii strains with diverse resistance mechanisms (OXA-51, IMP-1 and VIM-2 type β-lactamases), and intended to compare the effect of each antibiotic regimen (rifampicin, colistin, imipenem, tigecycline, rifampicin-imipenem and rifampicin-colistin) on mature A. baumannii biofilms using in vitro polystyrene plate biofilm assay.
RESULTS: Among three MDR A. baumannii strains, only VIM-2 strain produced strong biofilm compared to the controls (optical density, 8.04 ± 2.16 vs. 0.49 ± 0.26). Regarding VIM-2 strains, none of imipenem, colistin and rifampicin reduced biofilm formation alone at MIC of each antibiotic agent (inhibition of biofilm synthesis, less than 30%). In comparison, tigecyclin (0.76 ± 0.23), imipenem-rifampicin (1.07 ± 0.31) and colistin-rifampicin (1.47 ± 0.54) showed a significant inhibition of biofilm synthesis compared to the positive controls at 48 hours after incubation (P<0.01). Tigecycline inhibited biofilm formation even at the one fourth level of MIC (1.17 ± 0.21). Likewise, both imipenem and colistin were also effective even with the reduced concentrations when those were combined with rifampicin. Such biofilm-inhibiting effects with those antibiotic regimens sustained up to 96 hours after incubation.
CONCLUSION: Tigecycline, imipenem-rifampicin and colistin-rifampicin would be effective for the prevention or reduction of biofilm formation caused by A. baumannii strains.

PMID: 25844260 [PubMed]