Browsing by Author "Ermertcan, S"

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    Investigation of glycopeptid resistance in methicillin resistant staphylococcal isolates
    Hosgor-Limoncu, M; Ermertcan, S; Tasli, H; Kurutepe, S
    The emergence of Staphylococcus aureus strains with intermediate resistance (VISA) and heterogen resistance (hVISA) to vancomycin leads to the occurence of severe therapeutic problems. The aim of this study was to investigate the vancomycin resistance in methicillin resistant S.aureus (MRSA) and coagulase-negative staphylococci (MRCoNS) isolated from clinical samples in Bacteriology Laboratory of Microbiology and Clinical Microbiology Department of Celal Bayar University Faculty of Medicine, Manisa (located in western Anatolia, Turkey). A total of 120 staphyloccoccal strains (92 MRSA and 28 MRCoNS) isolated from different clinical specimens (tracheal aspirate, blood, abscess, wound swabs, sputum, catheter tips, etc) between the period of June 2005 to December 2006 were included to the study. Vancomycin resistance were determined by agar screening method using brain hearth infusion agar plates containing 6 mu g/mL vancomycin. Standard E-test and macro E-test methods were performed for 17 (14%) staphylococcal strains (10 MRSA and 7 MRCoNS) which had grown in agar screening plates. Vancomycin and teicoplanin minimal inhibitory concentration (MIC) ranges of those strains were found as 1.5-4 mu g/mL and 2-4 mu g/mL, respectively, by standard E-test method. In our study, no VISA and hVISA isolates were detected when MIC value of >= 8 mu g/mL for vancomycin and teicoplanin, or >= 22 mu g/mL for teicoplanin only were accepted as the criteria for hVISA determination. Agar screening method which is preferably used in routine laboratories for practical and economical reasons, lower sensitivity and specificity than E-test. It can be concluded that, since agar screening method is not reliable for the detection of vancomycin resistance, further multi-center studies with the use of standard methods are needed in order to clarify the vancomycin resistance patterns of staphylococci in our country.
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    In vitro effects of antibiofilm agents and antibiotics on coagulase-negative staphylococci
    Öztürk, I; Tekintas, Y; Temel, A; Ermertcan, S; Kurutepe, S; Hosgor Limoncu, M
    Coagulase negative staphylococci (CoNS) are important nosocomial pathogens that cause biofilm infections. Biofilm provides advantages for microorganisms to resist antibiotics and host immune systems. Considering the increased antibiotic resistance, alternative treatments are needed to combat biofilm infections. In the present study, the effects of antibiotics including gentamicin (GEN), ciprofloxacin, doxycycline (DOX), rifampicin (RIF) and antibiofilm agents including N-acetylcysteine (NAC), ethylenediaminetetraaceticacid (EDTA), nisin (NIS), farnesol (FAR) on clinical CoNSbiofilm and IS256, icaA gene expression levels were evaluated. Forty-five CoNS strains were isolated from patients' catheters, at Manisa Celal Bayar University Hospital. The minimum inhibitory concentrations (MICs) of agents were detected by broth microdilution method with European Committee for Antimicrobial Susceptibility Testing (EUCAST) criteria. The combined effects of agents were investigated by checkerboard method. The antibiofilm effects of combinations were investigated by spectrophotometric microplate method. The effects of combinations on IS256 and icaA gene expressions were evaluated by real-time quantitative reverse-transcriptase PCR. Twenty-four isolates (53.3%) were detected as strong biofilm producer. Biofilm production was inhibited in seven isolates in the presence of EDTA+RIF and NIS+DOX while NIS+GEN combination and RIF inhibited biofilm in six isolates. Nine combinations were found to have synergistic effect against isolate #6 which are resistant to four different antibiotics. The expressions of icaA and IS256 were downregulated in the presence of EDTA, NAC+CIP, NAC+GEN, NIS+GEN, FAR+GEN. Antibiofilm agent/antimicrobial combinations could have promising effects for preventing catheter colonization. The further studies on antibiofilm treatment strategies would be beneficial for decreasing morbidity-mortality rates and healthcare costs caused by biofilms.
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    Investigation of synergism of meropenem and ciprofloxacin against Pseudomonas aeruginosa and acinetobacter strains isolated from intensive care unit infections
    Ermertcan, S; Hosgör, M; Tünger, Ö; Cosar, G
    The aim of this study was to determine synergistic effects of meropenem and ciprofloxacin against Pseudomonas aeruginosa and Acinetobacter strains isolated from intensive care unit (ICU) infections. A total of 18 P. aeruginosa and 17 Acinetobacter strains were tested. MICs were determined using the broth microdilution method. The synergy of meropenem and ciprofloxacin was investigated in glass tubes using time-kill methodology. The synergistic effect of meropenem and ciprofloxacin in combination was found to be 22% at 0.5 x the MIC and 61% at 1 x the MIC in P. aeruginosa strains. Two strains (11%) showed synergy at both 0.5 and 1 x the MIC. Of the 18 P. acruginosa strains, 1 strain (6%) did not show a synergistic effect at either 0.5 or I x the MIC. In Acinetobacter strains, the synergistic effect of meropenem and ciprofloxacin in combination was found to be 29% at 0.5 x the MIC and 18% at 1 x the MIC. One strain (6%) showed synergy at both 0.5 and 1 x the MIC. Of the 17 Acinetobacter strains, 8 strains (47%) did not show a synergistic effect at either 0.5 or 1 X the MIC. According to the results of this study, the combination of meropenem and ciprofloxacin is more effective than either antibiotic alone in ICU infections due to P. acruginosa strains.
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    Emergence of phenotypic resistance to ciprofloxacin and levofloxacin in methicillin-resistant and methicillin-sensitive Staphylococcus aureus strains
    Limoncu, MH; Ermertcan, S; Çetin, CB; Cosar, G; Dinç, G
    The emergence of phenotypic resistance to ciprofloxacin and levofloxacin in methicillin-sensitive and methicillin-resistant Staphylococcus aureus (MRSA) strains was studied. Twenty MRSA and 77 methicillin-sensitive S.aureus (MSSA) strains susceptible to both quinolones were investigated for resistance after single step or serial passages. No growth of 20 MRSA strains was observed at 4 x MIC of levofloxacin after 48 h incubation, but 4 of 77 (5%) MSSA strains grew at the same concentration. At 4 x MIC concentration of ciprofloxacin, 10 MSSA (13%) and five MRSA (25%) strains were grown. In the serial passages of MRSA strains, resistance to ciprofloxacin was 75 and 5% for levofloxacin by the third passage. In the seventh passage this resistance was 100 and 15%, respectively. In MSSA strains, resistance to ciprofloxacin was 75 and 19% to levofloxacin at the third passage and at the seventh passage, 100 and 61%, respectively. Emergence of ciprofloxacin resistance was more common and developed more rapidly than resistance to levofloxacin in both MRSA and MSSA strains. (C) 2003 Elsevier Science B.V. and the International Society of Chemotherapy. All rights reserved.