The trends and types of carbapenemase-producing Gram-negative bacilli were analyzed from clinical specimens collected between 2005 and 2012 at a Korean teaching hospital. The proportions of carbapenem-resistant Acinetobacter spp. increased markedly to 66%. Metallo-beta-lactamase producers significantly decreased and the majority shifted from the bla(VIM-2) type to the bla(IMP-1) type.
Acinetobacter/classification/drug effects/*enzymology ; Acinetobacter Infections/drug therapy ; Anti-Bacterial Agents/*pharmacology ; Bacterial Proteins ; Carbapenems/*pharmacology ; Drug Resistance, Microbial ; Gram-Negative Bacteria/*drug effects/enzymology/isolation & purification ; Humans ; Incidence ; Microbial Sensitivity Tests/trends ; Population Surveillance ; Pseudomonas/classification/drug effects/enzymology ; Republic of Korea/epidemiology ; beta-Lactamases/biosynthesis/*drug effects

Emerging resistance to trimethoprim/sulfamethoxazole (SXT) poses a serious threat to the treatment of Stenotrophomonas maltophilia infections. We determined the prevalence and molecular characteristics of acquired SXT resistance in recent clinical S. maltophilia isolates obtained from Korea. A total of 252 clinical isolates of S. maltophilia were collected from 10 university hospitals in Korea between 2009 and 2010. Antimicrobial susceptibility was determined by using the CLSI agar dilution method. The sul1, sul2, and sul3 genes, integrons, insertion sequence common region (ISCR) elements, and dfrA genes were detected using PCR. The presence of the sul1 gene and integrons was confirmed through sequence analysis. Among the 32 SXT-resistant isolates, sul1 was detected in 23 isolates (72%), all of which demonstrated high-level resistance (> or =64 mg/L) to SXT. The sul1 gene (varying in size and structure) was linked to class 1 integrons in 15 of the 23 isolates (65%) harboring this gene. None of the SXT-susceptible isolates or the SXT-resistant isolates with a minimum inhibitory concentration of 4 and 8 mg/L were positive for sul1. Moreover, the sul2, sul3, and dfrA genes or the ISCR elements were not detected. The sul1 gene may play an important role in the high-level SXT resistance observed in S. maltophilia.
Anti-Bacterial Agents/pharmacology ; Bacterial Proteins/*genetics ; Drug Resistance, Bacterial/genetics ; Gram-Negative Bacterial Infections/microbiology/pathology ; Humans ; Integrons/*genetics ; Microbial Sensitivity Tests ; Stenotrophomonas maltophilia/*drug effects/genetics/isolation & purification ; Trimethoprim, Sulfamethoxazole Drug Combination/*pharmacology

BACKGROUND: Acinetobacter spp. is an important nosocomial pathogen for which increasing resistance to multiple antimicrobial agents has been observed. Prevalence of multidrug-resistant (MDR) Acinetobacter spp. in the intensive care unit (ICU) at a teaching hospital in Korea started to increase in 2008. The aim of this study was to determine the source of pathogen spread and to characterize the emerging strains at an early stage of outbreak. METHODS: Samples from respiratory instruments and fomites in the ICUs, as well as from the healthcare workers, were cultured to identify the sources of MDR Acinetobacter spp. Antimicrobial susceptibility was determined by the CLSI disk diffusion method. Pulsed field gel electrophoresis (PFGE) was performed for clinical and environmental isolates in order to determine clonality. Carbapenemase genes were detected by multiplex PCR. Infection control measures including peer-monitoring of hand washing, environmental cleaning and standard precautions were enforced. RESULTS: Among the samples from the ICU tools (105) and healthcare worker's hands (44), 31 (30%) and 2 (5%) respective samples yielded MDR Acinetobacter spp. Among the environmental samples, 90% were from respiratory-related equipment. The majority of clinical and environmental MDR Acinetobacter spp. (44/55) belonged to the pulsotype A. baumannii and carried both bla(OXA-51)-like and bla(OXA-23)-like genes. Even though infection-control measures were enforced, prevalence of MDR Acinetobacter spp. continues to increase. CONCLUSION: An outbreak of MDR Acinetobacter spp. in a Korean hospital was caused by A. baumannii carrying the bla(OXA-23)-gene and was correlated with contaminated respiratory-related instruments in the ICUs. More intensive measures for nosocomial infection control are needed for successful prevention of Acinetobacter spread in hospitals.
Acinetobacter* ; Anti-Infective Agents ; Cross Infection ; Delivery of Health Care ; Diffusion ; Disease Outbreaks ; Electrophoresis, Gel, Pulsed-Field ; Fomites ; Hand ; Hand Disinfection ; Hospitals, Teaching* ; Infection Control ; Intensive Care Units* ; Korea ; Multiplex Polymerase Chain Reaction ; Prevalence

We report a case of CTX-M-55-type extended-spectrum beta-lactamase (ESBL)-producing Shigella sonnei infection in a 27-year-old Korean woman who had traveled to China. The patient was admitted to the hospital due to abdominal pain, watery diarrhea, and fever (39.3degrees C). S. sonnei was isolated from her stool specimens, and the pathogen was found to be resistant to cefotaxime due to CTX-M-55-type ESBL. Insertion sequence (IS)Ecp1 was found upstream of the blaCTX-M-55 gene. The blaCTX-M-55 gene was transferred from the S. sonnei isolate to an Escherichia coli J53 recipient by conjugation. Pulsed-field gel electrophoresis and Southern blotting revealed that the blaCTX-M-55 gene was located on a plasmid of approximately 130 kb.
Adult ; Anti-Bacterial Agents/pharmacology ; Asian Continental Ancestry Group ; Cefotaxime/pharmacology ; China ; Drug Resistance, Bacterial/drug effects ; Dysentery, Bacillary/diagnosis/*microbiology ; Electrophoresis, Gel, Pulsed-Field ; Escherichia coli/metabolism ; Feces/microbiology ; Female ; Humans ; Plasmids/chemistry/genetics ; Republic of Korea ; Shigella sonnei/enzymology/*isolation & purification ; Travel ; beta-Lactamases/genetics/*metabolism

BACKGROUND: Trends in the isolation of enteropathogenic bacteria may differ depending on environmental sanitation. The aims of this study were to determine trends in the isolation and antimicrobial resistance patterns of enteropathogenic bacteria over the last 10 years. METHODS: We analyzed stool cultures of Salmonella spp., Shigella spp., Plesiomonas shigelloides, Yersinia spp., Vibrio spp., and Campylobacter spp. collected at Severance Hospital between 2001 and 2010. Antimicrobial susceptibility testing was performed using the disk diffusion method for nontyphoidal Salmonella (NTS) and Campylobacter. RESULTS: The number of specimens for stool culture significantly increased from 13,412 during 1969-1978 to 60,714 over the past 10 years, whereas the ratio of positive specimens significantly decreased from 12.9% (1,732) to 1.1% (648). The proportion of Salmonella Typhi decreased from 97.2% in 1969-1978 to 0.8% in 2001-2010, whereas the proportion of NTS increased from 2.8% to 99.2%. The proportion of Shigella among all enteric pathogens was over 50% from 1969 to 1983, while only seven strains were isolated from 2001 to 2010, with the exception of one outbreak. Campylobacter is the second most prevalent organism. The rates of susceptibility to ampicillin and cotrimoxazole were 61% and 92%, respectively, for NTS isolated from 2006 to 2010. The ciprofloxacin susceptibility rate was 79.5% for Campylobacter between 2006 and 2010. CONCLUSION: The number of isolates of Salmonella Typhi and Shigella significantly decreased, while the proportion of NTS and Campylobacter increased. Continuous monitoring of ciprofloxacin-resistant Campylobacter isolates is necessary.
Ampicillin ; Bacteria ; Campylobacter ; Ciprofloxacin ; Diffusion ; Plesiomonas ; Salmonella ; Salmonella typhi ; Sanitation ; Shigella ; Tertiary Healthcare ; Trimethoprim, Sulfamethoxazole Drug Combination ; Vibrio ; Yersinia

The aim of this study was to determine antimicrobial susceptibility of recent clinical Stenotrophomonas maltophilia isolates from Korea, and to compare the activity levels of several combinations of antimicrobials. A total of 206 non-duplicate clinical isolates of S. maltophilia was collected in 2010 from 11 university hospitals. Antimicrobial susceptibility testing was performed using the Clinical Laboratory Standards Institute agar dilution method. In vitro activity of antimicrobial combinations was tested using the checkerboard method. The susceptibility rates to trimethoprim-sulfamethoxazole and minocycline were 96% and 99%, respectively. The susceptibility rate to levofloxacin was 64%. All of four antimicrobial combinations showed synergy against many S. maltophilia isolates. A combination of trimethoprim-sulfamethoxazole plus ticarcillin-clavulanate was most synergistic among the combinations. None of the combinations showed antagonistic activity. Therefore, some of the combinations may be more useful than individual drugs in the treatment of S. maltophilia infection. Further clinical studies are warranted to validate our in vitro test results.
Anti-Infective Agents/*pharmacology ; Gram-Negative Bacterial Infections/microbiology ; Hospitals, University ; Humans ; Microbial Sensitivity Tests ; Minocycline/pharmacology ; Ofloxacin/pharmacology ; Republic of Korea ; Stenotrophomonas maltophilia/*drug effects/isolation & purification ; Trimethoprim-Sulfamethoxazole Combination/pharmacology

BACKGROUND: Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been used for the identification of bacteria worldwide. To our knowledge, the evaluation of MALDI-TOF MS for the identification of bacteria in Korea has not been studied. In this paper we compared the identification results of aerobic bacteria using MALDI-TOF MS to those results using conventional biochemical methods. METHODS: We evaluated the performance of a MALDI-TOF MS system (Bruker Daltonics, Leipzig, Germany) on consecutive aerobic isolates collected from January to February of 2011 which were identified using conventional methods (biochemical testing and commercial identification kits). Either directly smearing onto the target plate or protein extraction methods were additionally used if no reliable or discordant results were obtained. RESULTS: Among 523 isolates tested, 506 (97%) isolates had valid scores (> or =2.0), 11 (2%) isolates gave intermediate scores (1.7< or = score <2.0), and 6 (1%) isolates yielded no reliable identification (score <1.7). Of the 506 valid results (score > or =2.0) by MALDI-TOF MS, the identification matched at the species level in 486 (96%) isloates, matched at the genus level in 17 (3%) isloates, and was discordant at the genus and species levels in 3 (1%) isloates. CONCLUSION: The overall matching rate at the species level of MALDI-TOF MS was very high. When MALDI-TOF MS did not yield reliable results by direct smear, additional direct smears or protein extraction methods could be used to obtain better results. Our results showed that MALDI-TOF MS is a very useful method for the identification of aerobic bacteria isolated in clinical microbiology laboratories.
Bacteria ; Bacteria, Aerobic ; Korea ; Mass Spectrometry

BACKGROUND: The emergence of non-typhoidal Salmonella (NTS) with decreased susceptibilities to fluoroquinolone, ampicillin, or ceftriaxone has been reported worldwide. However, current surveillance studies of resistance among NTS in Korea are limited. Thus, the antimicrobial susceptibilities; resistance mechanisms such as extended-spectrum beta-lactamase (ESBL), plasmid-mediated AmpC beta-lactamase (PABL), and plasmid-mediated quinolone resistance (PMQR); and molecular epidemiologic characteristics were investigated in the present study. METHODS: National Institute of Health and National Veterinary Research and Quarantine Service collected NTS strains from 219 clinical and 293 non-clinical specimens from 2006 to 2008. The antimicrobial susceptibilities were determined using the Clinical and Laboratory Standards Institute disk diffusion test. ESBL, PABL, and qnr genotyping were performed using PCR and nucleotide sequencing. Pulsed-field gel electrophoresis was used for the molecular epidemiologic study. RESULTS: The resistance to ampicillin in clinical and non-clinical NTS was 49% and 18 to 47%, respectively. The resistance rates to trimethoprim-sulfamethoxazole in clinical and non-clinical NTS were 8% and 0 to 41%, respectively. The rates to extended-spectrum cephalosporin were 0 to 1%. One CTX-M-15-producing isolate and four CMY-2-producing isolates were detected. Notably, PFGE analysis showed four isolates carrying bla CMY-2, including one non-clinical strain had high clonality. Although the rate of ciprofloxacin resistance was very low, two qnrS1-carrying NTS strains were detected in non-clinical specimens. CONCLUSION: The resistance rates to ampicillin in both clinical and non-clinical NTS were high, while those to trimethoprim-sulfamethoxazole varied depending on the specimen. NTS strains harboring CTX-M-15-type ESBL or CMY-2-type PABL were detected even though the resistance rates to cephalosporins were very low. Four NTS strains carrying the blaCMY-2-gene implied zoonotic infection. Continuous effort to minimize transfer of resistance genes in NTS is necessary.
Ampicillin ; Animals ; Bacterial Proteins ; beta-Lactamases ; Ceftriaxone ; Cephalosporins ; Ciprofloxacin ; Diffusion ; Electrophoresis, Gel, Pulsed-Field ; Humans ; Korea ; Lifting ; Polymerase Chain Reaction ; Quarantine ; Salmonella ; Sprains and Strains ; Trimethoprim, Sulfamethoxazole Drug Combination

We determined the antimicrobial susceptibility of 90 clinical isolates of Stenotrophomonas maltophilia collected in 2009 at a tertiary care hospital in Korea. Trimethoprim-sulfamethoxazole, minocycline, and levofloxacin were active against most of the isolates tested. Moxifloxacin and tigecycline were also active and hold promise as therapeutic options for S. maltophilia infections.
Anti-Infective Agents/*pharmacology ; Hospitals ; Korea ; Microbial Sensitivity Tests ; Minocycline/pharmacology ; Ofloxacin/pharmacology ; Stenotrophomonas maltophilia/*drug effects ; Trimethoprim-Sulfamethoxazole Combination/pharmacology

BACKGROUND: In most clinical microbiology laboratories, inoculation of specimens on plates is performed manually and is a time-consuming process. The efficiency of this process can be improved by using an automated instrument. Currently, several automated instruments have been introduced for inoculation of samples. In this study, we have evaluated an automated instrument, PREVI Isola(R) (Biomerieux, France), used for inoculation of body fluids and urine specimens. METHODS: Both manual and automated instrument methods were used to inoculate 74 body fluid and 204 urine samples. Precision was evaluated by testing 3 types of urine samples (A, 6x10(3) colony-forming units (CFU)/mL; B, 3x10(4) CFU/mL; and C, >10(6) CFU/mL) in replicates of 20. Results of the 2 methods were compared by counting the isolated colonies on agar plates after incubation. The time required for both methods was also compared. RESULTS: The coefficient of variation (CV) of samples A, B, and C examined using the automated instrument method was 176.1%, 18.1%, and 12.6%, respectively. The sensitivity and specificity of testing body fluid samples were 77% and 100%, respectively, and those of urine samples were 87% each. The time required for testing 15 body fluid specimens and that for inoculation of each specimen was 9.7 min shorter using PREVI Isola(R) than using the manual method. CONCLUSIONS: The results of body fluid and urine culture by inoculation using the automated instrument, PREVI Isola(R), showed relative good agreement with those obtained using the manual method. The use of PREVI Isola(R) would be expected to reduce the time and labor involved in inoculating various kinds of specimens.
Agar ; Automation, Laboratory ; Body Fluids ; Microbiological Techniques ; Sensitivity and Specificity ; Stem Cells