BACKGROUND: Daptomycin is a novel cyclic lipopeptide antibiotic that exhibits in vitro bactericidal activity against gram-positive pathogens including methicillin-resistant staphylococci and vancomycin-resistant enterococci. The aim of this study is to determine the in vitro activities of daptomycin against recent clinical isolates of methicillin-resistant staphylococci and vancomycin-resistant enterococci in Korea. MATERIALS AND METHODS: A total of 117 clinical strains of methicillin-resistant staphylococci and vancomycin-resistant enterococci were isolated at a tertiary-care hospital in Korea in 2004. Susceptibility to daptomycin was tested by the CLSI broth microdilution method using Mueller-Hinton broth (MHB) which was adjusted to contain a final concentration of 50 microgram/mL of ionized calcium (Ca2+). Susceptibilities to ampicillin, oxacillin, levofloxacin, vancomycin, and linezolid were tested by the CLSI agar dilution method. RESULTS: All isolates of methicillin-resistant S. aureus and coagulase-negative staphylococci were inhibited by 1 microgram/mL of daptomycin, and MIC90s were 1 microgram/mL, which were similar to those of vancomycin and linezolid. MIC90s of daptomycin for vancomycin-resistant E. faecalis and E. faecium were 0.5 microgram/mL and 2 microgram/mL, respectively, and all isolates were susceptible to daptomycin. MIC90s of linezolid and levofloxacin for vancomycin-resistant enterococci were 1-2 microgram/mL and 64 microgram/mL, respectively. Resistance rates of vancomycin-resistant E. faecalis and E. faecium to levofloxacin were 100% and 96%, respectively. Daptomycin MICs in MHB supplemented to 20-25 microgram/ml of Ca2+ were 2-8 fold higher than those in MHB supplemented to 50 microgram/mL of Ca2+. CONCLUSION: Daptomycin is very active in vitro against methicillin-resistant staphylococci and vancomycin-resistant enterococci isolated in Korea, and it is important to test in vitro activity of daptomycin using MHB containing 50 microgram/mL of Ca2+.
Agar ; Ampicillin ; Calcium ; Daptomycin* ; Korea* ; Levofloxacin ; Linezolid ; Methicillin Resistance* ; Methicillin-Resistant Staphylococcus aureus ; Oxacillin ; Vancomycin

BACKGROUND: Daptomycin is a novel cyclic lipopeptide antibiotic that exhibits in vitro bactericidal activity against gram-positive pathogens including methicillin-resistant staphylococci and vancomycin-resistant enterococci. The aim of this study is to determine the in vitro activities of daptomycin against recent clinical isolates of methicillin-resistant staphylococci and vancomycin-resistant enterococci in Korea. MATERIALS AND METHODS: A total of 117 clinical strains of methicillin-resistant staphylococci and vancomycin-resistant enterococci were isolated at a tertiary-care hospital in Korea in 2004. Susceptibility to daptomycin was tested by the CLSI broth microdilution method using Mueller-Hinton broth (MHB) which was adjusted to contain a final concentration of 50 microgram/mL of ionized calcium (Ca2+). Susceptibilities to ampicillin, oxacillin, levofloxacin, vancomycin, and linezolid were tested by the CLSI agar dilution method. RESULTS: All isolates of methicillin-resistant S. aureus and coagulase-negative staphylococci were inhibited by 1 microgram/mL of daptomycin, and MIC90s were 1 microgram/mL, which were similar to those of vancomycin and linezolid. MIC90s of daptomycin for vancomycin-resistant E. faecalis and E. faecium were 0.5 microgram/mL and 2 microgram/mL, respectively, and all isolates were susceptible to daptomycin. MIC90s of linezolid and levofloxacin for vancomycin-resistant enterococci were 1-2 microgram/mL and 64 microgram/mL, respectively. Resistance rates of vancomycin-resistant E. faecalis and E. faecium to levofloxacin were 100% and 96%, respectively. Daptomycin MICs in MHB supplemented to 20-25 microgram/ml of Ca2+ were 2-8 fold higher than those in MHB supplemented to 50 microgram/mL of Ca2+. CONCLUSION: Daptomycin is very active in vitro against methicillin-resistant staphylococci and vancomycin-resistant enterococci isolated in Korea, and it is important to test in vitro activity of daptomycin using MHB containing 50 microgram/mL of Ca2+.
Agar ; Ampicillin ; Calcium ; Daptomycin* ; Korea* ; Levofloxacin ; Linezolid ; Methicillin Resistance* ; Methicillin-Resistant Staphylococcus aureus ; Oxacillin ; Vancomycin

Antimicrobial resistance surveillance is necessary to determine the size of the problem and to guide empirical selection of antimicrobial agents for treating infected patients. The aim of this study was to analyze the results of susceptibility tests performed by hospitals participating in the Korean Nationwide Surveillance of Antimicrobial Resistance (KONSAR) program. The rates of oxacillin-resistant staphylococci, penicillin-nonsusceptible pneumococci, and ampicillin-resistant E. faecium were over 70%. Ampicillin-resistant H. influenzae increased to 68%. Expanded-spectrum cephalosporin-resistant K. pneumoniae, fluoroquinolone-resistant E. coli, and imipenem-resistant P. aeruginosa remained at 16% through 27%, depending on the species. The proportions of vancomycin-resistant E. faecium and imipenem-resistant P. aeruginosa were 18 - 24% and 19-21%, respectively, indicating the seriousness of antimicrobial resistance. In conclusion, the increasing prevalence of resistant bacteria indicates that more concerted effort is required to conserve the usefulness of precious new antimicrobial agents.
Anti-Bacterial Agents/*pharmacology ; Cephalosporins/*pharmacology ; *Drug Resistance, Microbial ; Enterococcus/*drug effects ; Gram-Negative Bacteria/*drug effects ; Human ; Imipenem/*pharmacology ; Korea ; *Vancomycin Resistance

BACKGROUND: Derepressed AmpC beta-lactamase producing Enterobacter cloacae, Citrobacter f reundii, and Serratia marcescens are important nosocomial pathogens and the infections are difficult to treat, because they are multi-drug resistant. The aim of this study was to determine the isolation rate and trend, and antimicrobial susceptibility of derepressed strains isolated from clinical specimens. METHODS: E. cloacae, S. marcescens, and C. f reundii isolated from 1996 through 2000 were enrolled in the study. Antimicrobial susceptibility was tested by NCCLS disk diffusion method. Derepressed strain was defined as strain non-susceptible to third generation cephalosporin. The isolation patterns of important gram-negative bacilli with the derepressed strains were analyzed with respect to years, patient's locations and specimens. RESULTS: Among the clinical isolates, the derepressed strains of E. cloacae, S. marcescens, and C. f reundii were 65%, 70%, and 56%. The proportion of the derepressed strains : E. cloacae increased from 68% in 1996 to 71% in 1998, however, decreased to 59% in 2000, S. marcescens increased from 68% in 1996 to 73% in 2000, C. f reundii decreased from 69% in 1996 to 41% in 2000. The proportion of the derepressed strains were high among the isolates from blood and respiratory specimens of inpatient and intensive care patient. The resistance rates of the depressed strains were 47~62% to third generation cephalosporin and aztreonam, 15~85% to aminoglycoside, 68% to cotrimoxazole, and 31% to levofloxacin. CONCLUSION: Among the clinical isolates of E. cloacae, S. marcescens, and C. f reundii, the derepressed strains were as high as 56~70%, and they were commonly isolated from blood and sputum specimens of inpatient and intensive care patient, and showed high resistance rates to the most antimicrobial agents.
Anti-Infective Agents ; Aztreonam ; beta-Lactamases* ; Citrobacter freundii ; Citrobacter* ; Cloaca ; Diffusion ; Enterobacter cloacae ; Enterobacter* ; Humans ; Inpatients ; Critical Care ; Levofloxacin ; Serratia marcescens ; Serratia* ; Sputum ; Trimethoprim, Sulfamethoxazole Drug Combination

BACKGROUND: Carrying antimicrobial resistance genes is a burden to bacteria. Therefore, in the absence of antimicrobial selective pressure, susceptible bacteria are expected to replace resistant ones. The cost was reported to decrease with time, but the effect of different species of susceptible bacteria on extended-spectrum -lactamase (ESBL)-, AmpC beta-lactamase-, and VIM-2 metallo-beta-lactamase-producing gram-negative bacilli are not known. The aim of this study was to determine the effect in vitro. METHODS: Antimicrobial-susceptible and -resistant strains of Escherichia coli, Enterobacter aerogenes, Klebsiella p neumoniae, and Acinetobacter baumannii were subcultured daily in glucose limited minimal salt medium at 30degrees C and 37degrees C, and the numbers of cells (CFU/mL) were determined by culturing on Mueller-Hinton agar and MacConkey agar plates. RESULTS: Continued incubation without subculture of both individual and mixed cultures at 37degrees C showed higher counts of a ESBL-producing K. p neumoniae than a susceptible E. coli. Daily subcultures of two strains in a tube showed the counts were : ESBL-producing K. pneumoniae >susceptible E. coli; susceptible E. aerogenes >ESBL-producing K. p neumoniae; susceptible E. aerogenes >VIM-2-beta-lactamase-producing Acinetobacter baumannii. The counts were similar for susceptible K. p neumoniae and AmpC beta-lactamasehyperproducing E. aerogenes. Initial low count of a susceptible E. coli and an ESBL-producing K. p neumoniae at 30degrees C gradually increased with continued subculture. CONCLUSION: Growth of not all resistant bacteria are slower and the growth improves with continued subculture. Coexistence of a susceptible bacteria with resistant bacteria in GLMS medium both at 30degrees C and 37degrees C does not reduce the number of resistant bacteria.
Acinetobacter baumannii ; Agar ; Anti-Infective Agents* ; Bacteria ; Enterobacter aerogenes ; Escherichia coli ; Glucose ; Klebsiella ; Pneumonia

The trend of antimicrobial resistance of bacteria isolated from patients in 30 Korean hospitals in 1999 was analyzed with a particular attention to cefotaxime- or fluoroquinolone-resistant gram-negative bacilli, imipenem-resistant Pseudomonas aeruginosa, and vancomycin-resistant enterococci. Adequacy of susceptibility testing, and any change in the frequencies of isolated species were also analyzed. The results showed that only 20% and 30% of hospitals tested the piperacillin-tazobactam and cefoxitin susceptibility of Enterobacteriaceae, respectively, only 24% of hospitals the piperacillin-tazobactam susceptibility of P. aeruginosa, and 17% of hospitals the fusidic acid susceptibility of staphylococci. Among the isolates 26.3% were glucose-nonfermenting gram-negative bacilli, and 34.7% of Enterococcus were Enterococcus faecium. Slight decline of cefotaxime-resistance rate to 20% was noted in Klebsiella pneumoniae, while fluoroquinolone-resistantce rate was 68% in Acinetobacter baumannii. The ceftazidime- and imipenem-resistance rates were 17% and 18%, respectively in P. aeruginosa. The vancomycin-resistance rate of E. faecium rose significantly to 15.1%, but the rates varied significantly depending on hospitals suggesting presence of different degree of selective pressure or nosocomial spread. In conclusion, the prevalence of imipenem-resistant P. aeruginosa and the increase of vancomycin-resistant E. faecium were the particularly worrisome phenomena observed in this study.
Anti-Infective Agents, Fluoroquinolone/*pharmacology ; Antibiotics/*pharmacology ; Cephalosporins/*pharmacology ; Drug Resistance, Microbial ; Enterobacteriaceae/drug effects ; Enterococcus/*drug effects ; Gram-Negative Bacteria/*drug effects ; Human ; Imipenem/*pharmacology ; Korea ; Microbial Sensitivity Tests ; Pseudomonas aeruginosa/drug effects ; *Vancomycin Resistance

BACKGROUND: The aim of the study was to determine prevalence of potential heterogeneous vancomycin-resistant Staphylococcus aureus (h-VRSA) among methicillin-resistant S. aureus (MRSA) isolated in Korea by using Mu-3 agar and to determine the effect of in vitro vancomycin exposure on the resistance. METHODS: MRSAs isolated in 1980-1999 were screened for the presence of VISA or h-VRSA using Mu-3 agar. MIC of vancomycin was tested by NCCLS agar dilution and broth microdilution tests. Suspected h-VRSA were selected by vancomycin-containing media and change of resistance was determined by population analysis. A strain with Mu50 type growth was serially exposed to 8 pg/ml of vancomycin containing media and change of the vancomycin resistance was determined. RESULTS: Among the 455 MRSA isolates, 18 (3.9 %) grew on selective brain heart infusion agar (BHIA), and 354 (77,8%) on Mu-3 agar, 66 (14.5%) with Mu3 type growth and 78 (17.1%) with Mu50 type growth. MIC of vancomycin was 11 pg/ml for some of the isolates when inocula were approximately 10' CFU, but VISA was not present when tested by NCCLS broth microdilution test. Exposure of the isolates to van-cornycin raised the MIC. Serial exposure once to 8 pg/ml of vancomycin resulted in significant decrease of cells susceptible to 8-12 pg/ml of vancomycin. CONCLUSION: VISA was not present among the test isolates, but 34.2% were suspected to be potential h-VRSAs, suggesting possible emergence of VISA if vancomycin was administered prolonged period. It is considered that suitable screening media are vancomycin containing BHIA for VISA and Mu-3 agar for h-VRSA. The isolates showing Mu50 type growth on Mu-3 agar are not always VISA, but rather h-VRSA.
Agar* ; Brain ; Heart ; Korea ; Mass Screening ; Methicillin Resistance ; Methicillin-Resistant Staphylococcus aureus ; Prevalence ; Staphylococcus aureus* ; Staphylococcus* ; Vancomycin Resistance ; Vancomycin*

No Abstract Available.
Korea*

No Abstract Available.
Korea*

Rapid identification of Mycobacterium spp. isolated from patients is important with increased isolation of mycobacteria other than tubercle bacilli (MOTT). DNA-DNA hybridization with streptavidin-peroxidase and tetramethylbenzidine (TMB) color reaction method was recognized as a useful tool for identification of various species of mycobacteria. In this study, optimum condition of the test was determined. The optimal concentrations of tetramethylbenzidine dihydrochloride and hydrogen peroxide for streptavidin-horseradish peroxidase were 0.3-0.6 ug/ ml and 0.16 mM, respectively. The TMB stock solution was stable when prepared in methanol and the dilution of TBM stock solution in 10 mM sodium citrate-10 mM EDTA solution (pH 5.0) gave highest peroxidase-TMB activity. The suitable composition of hybridization solution consisted of 2 x SSC, 10% dextran sulfate, 50 ug/ml salmon DNA, 5 x Denhardt's solution, and 50% formamide. The 5-minute heating at 100C of test DNA prior to photobiotin labeling significantly increased the reaction. In conclusion, DNA-DNA hybridization method with streptavidin-peroxidase and TMB color reaction method may be useful for rapid identification of Mycobacterium spp. isolated from patients.
Dextran Sulfate ; DNA ; Edetic Acid ; Heating ; Hot Temperature ; Humans ; Hydrogen Peroxide ; Methanol ; Mycobacterium* ; Peroxidase ; Salmon ; Sodium