No abstract available.
Gram-Positive Cocci* ; Imipenem* ; Ofloxacin*

Minimal inhibitory concentrations (MICs) against piperacillin/tazobactam were determined on a total of 50 clinical isolates of imipenem resistant Pseudomonas aeruginosa (IRPA). MIC50 and MIC90 were 32microgram/mL and 512microgram/mL, respectively. The susceptibility of IRPA against piperacillin/tazobactam was 59%. Of the 50 IRPA strains, only two were PCR positive for blaVIM and none for blaIMP.
Imipenem ; Polymerase Chain Reaction ; Pseudomonas aeruginosa* ; Pseudomonas*

No abstract available.
Acinetobacter baumannii* ; Acinetobacter* ; Hospitals, General* ; Imipenem* ; Korea*

BACKGROUND: In our hospital, an abrupt increase in the resistant rate of A. baumannii to imipenem was observed. We evaluated the imipenem minimal inhibitory concentration (MIC) of an automated system that our laboratory is using, by comparing with those of other methods. METHODS: During the period from February 2002 to February 2003, the imipenem MICs of the agar dilution method, Etest(R), and the disk diffusion method, were compared for imipenem-resistant A. baumannii tested by an automated system in 46 samples at Chung-Ang University Phil-Dong Hospital. We tested for susceptibility to imipenem with the Vitek system by using the GNI card, the disk diffusion method by using the imipenem disk (BBL(TM)), and the agar dilution method. PCR testing of the isolates for carbapenemase genes (IMP-1 and VIM-2) detected in other hospitals was done using published primers and conditions. RESULTS: By the agar dilution method, 23 (50.0%) isolates were susceptible to imipenem, 14 (30.4%) isolates were intermediate, and 9 (19.6%) isolates were resistant. However, by the Etest, 8 (17.4%) were susceptible to imipenem, and 28 (60.9%) isolates were resistant. By the disk diffusion method, the susceptible isolates were 14 (30.4%) and the resistant isolates were 17 (37.0%). Quantitative agreement between the agar dilution method and the disk diffusion test gave an inverse linear correlation coefficient (r=-0.564). The results of the 13 isolates, whose results of the MIC were below 2 or above 16 in the agar dilution method, corresponded with the Etest and the disk diffusion test. The IMP-1 gene was detected in one isolate. CONCLUSIONS: It is recommended that when a gram-negative bacilli isolate including A. baumannii is characterized as resistant to imipenem by the Vitek system, an additional simple test, such as the disk diffusion assay, might be used.
Acinetobacter baumannii* ; Agar ; Diffusion ; Imipenem* ; Polymerase Chain Reaction

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 beta-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.
Acinetobacter baumannii* ; Anti-Bacterial Agents ; Biofilms ; Colistin* ; Imipenem* ; Polystyrenes ; Rifampin*

BACKGROUND: Catheter-related bacteremia is a frequent complication among hemodialysis patients using a tunneled cuffed catheter. The standard therapy of catheter-related bacteremia involves both systemic antibiotics and catheter replacement. This study was performed to evaluate the effect of antibiotic lock therapy in conjugation with systemic antibiotics without catheter removal on catheter-related bacteremia. METHODS: Thirty six chronic hemodialysis patients with tunneled cuffed catheter were monitored for infection between July 2001 and July 2005. We analyzed the efficacy of antibiotic lock protocol compared with systemic antibiotics alone. RESULTS: Twenty-nine episodes of catheter-related bacteremia occurred in 27 patients during the study periods. The incidence of catheter-related bacteremia was 1.5 episodes/1000 catheter-days. A single gram-positive coccus grew in the 16 cases (55.2 %), and gram-negative organisms grew in the 69 cases (31.0%). Sixteen of 18 patients (88.9%) treated with antibiotic lock protocol had successful catheter salvage versus only 6 of the 11 patients (54.5%) treated with systemic antibiotics alone (p=0.05). Three patients with Burkholderia pickettii and a patient with Acinetobactor calcoaceticus-baumannii complex were treated with antibiotic lock protocol with systemic ciprofloxacin and imipenem, respectively. CONCLUSION: This study suggests that antibiotic lock protocol in eradicating catheter-related bacteremia is effective treatment without requiring catheter replacement.
Anti-Bacterial Agents ; Bacteremia* ; Burkholderia ; Catheters ; Ciprofloxacin ; Humans ; Imipenem ; Incidence ; Renal Dialysis

BACKGROUND: Multi-drug resistant (MDR) Acinetobacter baumannii has emerged as a significant infectious agent in hospitals worldwide. The purpose of this study was to determine the molecular characterization of MDR A. baumannii clinical isolates. METHODS: Two hundred eighty-five strains of non-duplicated A. baumannii collected from March to November 2011 from a university hospital laboratory located in the Wonju area of the Gangwon province of Korea were analyzed for MDR genes. RESULTS: All of the 285 imipenem-resistant A. baumannii isolates were encoded by a blaOXA-23-like gene, and all isolates with the blaOXA-23-like gene had the upstream element ISAba1. The 16S rRNA methylase gene armA was detected in 153 (50.2%) clinical isolates, but rmtA, rmtB, rmtC, rmtD and npmA were not detected in any isolates in the present study. The gene encoding aac(6')-Ib was the most prevalent aminoglycoside-modifying enzyme. The sequencing data for the quinolone resistance-determining region of gyrA and parC revealed the presence of Ser (TCA) 83 to Leu (TTA) and Ser (TCG) 80 to Leu (TTG) substitutions. All but one of the 285 A. baumannii isolates showed similar band patterns on repetitive extragenic palindromic-PCR profiles. CONCLUSION: The molecular characteristics of the resistance genes of MDR A. baumannii isolates obtained from the Wonju area of Gangwon province were similar to those of other areas in Korea.
Acinetobacter ; Acinetobacter baumannii ; beta-Lactamases ; Genes, MDR ; Imipenem ; Korea ; Laboratories, Hospital ; Methyltransferases

BACKGROUND: The incidence of infections with imipenem- resistant Acinetobacter baumannii (IRAB) and Pseudomonas aeruginosa (IRPA) is increasing worldwide, and recent molecular studies indicate that the prevalence of carbapenemases is increasing in various parts of the world. However, few long-term longitudinal studies have assessed the prevalence of IRAB- and IRPA-derived carbapenemases and integrases in a hospital setting in Korea. METHODS: The carbapenemase genes (blaOXA-23, blaOXA-24, blaOXA-58, blaIMP-1, blaVIM-2, blaSIM-1, blaSPM-1) and integrase genes (intI1, intI2, intI3) produced by 46 IRAB strains and 51 IRPA strains collected at Chosun University Hospital between 2003 and 2006 were determined by PCR. RESULTS: The IRAB strains produced class 1 integrases more often than did the IRPA strains. However, the incidence increased steadily in both strains, reaching 100% in 2006. Carbapenemases of blaIMP-1 and blaVIM-2 types were found in 57% and 64% of the IRAB strains, respectively, in 2003. However, only one strain with blaVIM-2 was found in 2004 and another one with blaIMP-1 in 2005. The prevalence of carbapenemases was very low in the IRPA strains, just one strain with blaVIM-2 in 2005 and another one with blaoxa-23 in 2006. No other types of carbapenemase genes were detected in both strains. Rep-PCR of IRAB strains in 2003 showed different patterns. CONCLUSION: The incidence of carbapenemase varied by year but was generally low, except in 2003. The prevalence of class 1 integrases was consistently high and increased every year. The reason for the high prevalence of carbapenemases in 2003 is still unknown, but we assumed that it was not from the spread of a clone containing either blaIMP-1 or blaVIM-2 because the strains exhibited different rep-PCR patterns.
Acinetobacter baumannii* ; Acinetobacter* ; Clone Cells ; Imipenem ; Incidence ; Integrases* ; Korea ; Polymerase Chain Reaction ; Prevalence* ; Pseudomonas aeruginosa* ; Pseudomonas*

Carbapenemase production has been reported worldwide in gram-negative bacteria, including Acinetobacter species. We detected carbapenemase-producing Acinetobacter pittii in clinical isolates in Daejeon, Korea. Twenty-one ertapenem-resistant A. pittii isolates screened with a disk diffusion method were characterized by using the Epsilon test, four multiplex PCR assays, and a multilocus sequence typing (MLST) scheme. A total of 21 A. pittii isolates harbored the metallo-beta-lactamase (MBL) gene bla(IMP-1) or bla(NDM-1). Nineteen isolates containing bla(IMP-1) were resistant to imipenem and meropenem, but two isolates harboring bla(NDM-1) were susceptible to them. The sequence types (STs) of the two New Delhi MBL (NDM-1)-producing A. pittii isolates were ST70 and ST207, which differed from the STs (ST63, ST119, ST396, and a novel ST) of the IMP-1-producing A. pittii. This is the first report on NDM-1-producing A. pittii isolates in Korea. Our results emphasize that the study of NDM-1-producing gram-negative bacteria should involve carbapenem-susceptible as well as carbapenem-resistant isolates.
Acinetobacter* ; Diffusion ; Gram-Negative Bacteria ; Imipenem ; Korea ; Multilocus Sequence Typing ; Multiplex Polymerase Chain Reaction

BACKGROUND: Periodic monitoring of regional or institutional resistance trends of clinically important anaerobic bacteria is recommended, because the resistance of anaerobic pathogens to antimicrobial drugs and inappropriate therapy are associated with poor clinical outcomes. There has been no multicenter study of clinical anaerobic isolates in Korea. We aimed to determine the antimicrobial resistance patterns of clinically important anaerobes at multiple centers in Korea. METHODS: A total of 268 non-duplicated clinical isolates of anaerobic bacteria were collected from four large medical centers in Korea in 2012. Antimicrobial susceptibility was tested by the agar dilution method according to the CLSI guidelines. The following antimicrobials were tested: piperacillin, piperacillin-tazobactam, cefoxitin, cefotetan, imipenem, meropenem, clindamycin, moxifloxacin, chloramphenicol, metronidazole, and tigecycline. RESULTS: Organisms of the Bacteroides fragilis group were highly susceptible to piperacillin-tazobactam, imipenem, and meropenem, as their resistance rates to these three antimicrobials were lower than 6%. For B. fragilis group isolates and anaerobic gram-positive cocci, the resistance rates to moxifloxacin were 12-25% and 11-13%, respectively. Among B. fragilis group organisms, the resistance rates to tigecycline were 16-17%. Two isolates of Finegoldia magna were non-susceptible to chloramphenicol (minimum inhibitory concentrations of 16-32 mg/L). Resistance patterns were different among the different hospitals. CONCLUSIONS: Piperacillin-tazobactam, cefoxitin, and carbapemems are highly active beta-lactam agents against most of the anaerobes. The resistance rates to moxifloxacin and tigecycline are slightly higher than those in the previous study.
Agar ; Bacteria, Anaerobic* ; Bacteroides fragilis ; Cefotetan ; Cefoxitin ; Chloramphenicol ; Clindamycin ; Gram-Positive Cocci ; Imipenem ; Korea ; Metronidazole ; Piperacillin