국내 분리 Acinetobacter 균종의 carbapenem과 colistin 내성 양상, 기전 및 분자역학적 특성

Dept. of Medicine/박사Recent increasing carbapenem resistance in Acinetobacter species is very worrisome, resulting in a very limited antimicrobial treatment option. Colistin is the only potent therapeutic options available for treatment of nosocomial infections caused by multi-drug resistant Acinetobacter species. However, colistin-resistant Acinetobacter species of clinical isolates were reported. In present study, it was investigated that resistance patterns and mechanisms to carbapenems and colistin in Acinetobacter species isolated from clinical specimens from 19 hospitals in six provinces in Korea in 2008, and the epidemiological traits of carbapenem-non-susceptible Acinetobacter baumannii (CNSAB), as well as the usefulness of phylogenic grouping based on partial rpoB gene sequencing in defining the epidemiological traits of CNSAB.A total of 547 non-duplicate clinical isolates of Acinetobacter species were collected from 19 hospitals. Reduced susceptibility rates to imipenem or meropenem were 70% (272/388) for A. baumannii, 5% (4/82) for A. nosocomialis, 13% (8/62) for A. pitti, and 0% (0/13) for A. bereziniae. Colistin-resistant clinical isolates were one A. baumannii, one A. bereziniae and two Acinetobacter genomospecies 14 TU. Molecular characterization of the 272 CNSAB isolates using multilocus sequencing typing identified five sequence types (STs): ST92, ST75, ST137, ST138 and ST69. Those STs were clustered into clonal complex 92, sharing alleles at five to six of seven housekeeping gene loci. ST92 was the predominant ST and was associated with European clone II disseminated worldwide. CNSAB of CC92 carried the blaOXA-23 gene (n = 169), the blaOXA-51-like gene preceded by ISAba1 (n = 89) or both (n = 14). Sequence -based analysis of the rpoB gene showed single-nucleotide substitutions in zone 2 of the rpoB gene, resulting in division into five groups (A to E groups). Notably, all CNSAB isolates belonged to subgroup B-0 with a G428T substitution in zone 2. All of the other isolates belonging to group C, D and E were susceptible to carbapenems.In conclusion, carbapenem resistance rates of A. baumannii are very high, over 70%, whereas colistin resistance rate of Acinetobacter species is very low until now. CNSAB isolates of CC92 with the G428T substitution in zone 2 of the rpoB gene are disseminated nationwide in our country. A. baumannii with the G428T substitution in zone 2 may be more likely to acquire carbapenem resistance than are other isolates.ope

Reduction of the Platelet Transfusion Dose and Its Effects

BACKGROUND: In Korea, a platelet transfusion dose (TD) of 8 units of platelet concentrates (PC) is usually used. To minimize the shortage of blood products and transfusion-related adverse reactions, the TD has been changed from 8 to 6 units in 2006 in our hospital. Here, we analyzed the dose reduction effect on patients' platelet counts and transfusion frequency. METHODS: We compared the amount of issued PC, platelet counts before and after transfusion, post-transfusion platelet increments, and transfusion frequencies in patients who were transfused with 8 PC in 2006 and 6 PC in 2008. RESULTS: Despite an increase in the number of admitted patients by 20% in 2008 with a disease distribution similar to that in 2006, the number of issued PC in 2008 was decreased by 26.6% compared to that in 2006. In 2008, post-transfusion platelet counts, pre-transfusion platelet counts in patients transfused with 320 mL whole blood-derived PC, and platelet increments in patients transfused with 400 mL whole blood-derived PC were significantly decreased. However, the mean transfusion frequency per one month was not significantly different, 4.3 times in 2006 and 4.7 in 2008. CONCLUSIONS: By implementing a policy of platelet TD restriction, the amount of total issued PC was markedly decreased. Although post-transfusion platelet counts were decreased, the transfusion frequency in a month was not significantly increased. The restriction of platelet TD was helpful for increasing physicians' recognition of blood shortage while achieving similar transfusion effects. We conclude that 6 units of PC would be a better guideline for the platelet TDope

Recent Trends in Antimicrobial Resistance in Intensive Care Units in Korea

Background: In general, higher resistance rates are observed among intensive care unit (ICU) isolates than non-ICU isolates. In this study, resistance rates of isolates from ICUs and non-ICUs were compared using the data generated from 20 hospitals in Korea. Methods: Susceptibility data were collected from 20 hospitals participating in the Korean Nationwide Surveillance of Antimicrobial Resistance (KONSAR) program. Duplicate isolates were excluded from the analysis. The resistance rates did not include intermediate susceptibility. Results: The most prevalent bacteria in the ICUs were Staphylococcus aureus (21%) and Acinetobacter spp. (19%), and those in non-ICU were Escherichia coli (27%) and S. aureus (14%). The resistance rates were higher in ICUs than in non-ICUs at 84% and 58% for methicillin-resistant S. aureus, 86% and 70% for methicillin-resistant coagulase-negative Staphylcoccus (CNS), 34% and 19% for vancomycin-resistant Enterococcus faecium, 38% and 19% for cefotaxime-resistant E. coli, 45% and 25% for cefotaxime-resistant Klebsiella pneumoniae, 42% and 24% for ceftazidime-resistant Enterobacter cloacae, 29% and 11% for ceftazidime-resistant Serattia marcescens, 83% and 44% for imipenem-resistant Acinetobacter spp., and 32% and 17% for imipenem-resistant Pseudomonas aeruginosa, respectively. Conclusion: The most prevalent bacteria in ICUs were S. aureus, CNS, and Acinetobacter spp., and high multi-drug resistance rates were observed in the Acinetobacter isolates. Therefore, infection control should be practiced in ICUs to prevent infections caused by multi-drug resistant bacteria.ope

Evaluation of Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry for Identification of Aerobic Bacteria in a Clinical Microbiology Laboratory

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First Isolation of Streptococcus gallolyticus subsp. pasteurianus from a Korean Patient with Severe Septic Shock.

A 60-year-old man presented with a 1-day history of fever, vomiting, and diarrhea. He was diagnosed with severe septic shock on the basis of a body temperature of 38.9degrees C, heart rate of 92/min, respiratory rate of 25/min, WBC count of 22,970/microL, C-reactive protein (CRP) level of 136 mg/L, blood urea nitrogen (BUN) of 34.0 mg/dL, and creatinine of 2.98 mg/dL. On blood culture, Gram-positive cocci were detected in all 6 bottles. Small grayish non-hemolytic colonies were found on blood agar plates after incubation at 37degrees C for 2 days. The isolates were negative for catalase and L-pyrrolidonyl-beta-naphthylamide hydrolysis, and positive for bile-esculin and leucine aminopeptidase activity. The strain was identified as Streptococcus gallolyticus subsp. pasteurianus using Vitek 2 GP II systems. We performed 16S rRNA gene sequencing and detected 100% identity with S. gallolyticus subsp. pasteurianus strain CIP 107122T (1,345/1,345-bp). The patient recovered after receiving ampicillin-sulbactam. This is the first report of phenotypic and genetic identification of S. gallolyticus subsp. pasteurianus causing severe septic shock in a Korean patient.ope

Antimicrobial Resistance and Molecular Epidemiologic Characteristics of Neisseria gonorrhoeae Isolated from Korea in 2013

Background : Antimicrobial resistance of Neisseria gonorrhoeae has become a serious problem worldwide, and ceftriaxone non-susceptible isolates have been recently reported from Japan and Europe. In this study, we evaluated the antimicrobial susceptibilities and molecular epidemiological characteristics of isolates from Korea in 2013. Methods : Sixty strains of N. gonorrhoeae were collected from Korean patients and prostitutes. Antimicrobial susceptibility was tested by the agar dilution and disk diffusion methods. N. gonorrhoeae multi-antigen sequence typing (NG-MAST) was performed in order to determine the molecular epidemiologic relatedness. Results : All of isolates were non-susceptible to penicillin G and tetracycline, and the rate of ciprofloxacinresistant isolates was 95% in 2013. The MICs of ceftriaxone were within the susceptible range for all isolates, but one isolate non-susceptible to cefixime (MIC=0.5 µg/mL) was encountered. The isolates with decreased susceptibility (MIC≤0.12 µg/mL) to cefixime or ceftriaxone accounted for 10% and 14% of the isolates tested, respectively. In NG-MAST analysis, 40 different STs were encountered among the 59 isolates. Isolates that belonged to tbpB110 showed higher cefixime and ceftriaxone MICs (0.12-0.5 µg/mL) as well as cefixime resistance. Conclusion : Most of the N. gonorrhoeae isolates showed susceptibility to spectinomycin and cephalosporins. Due to the emergence of isolates that are non-susceptible to cefixime and the prevalence of isolates with the tbpB110 allele belonging to ST1407, which cause cefixime and ceftriaxone treatment failure in successful global clones of N. gonorrhoeae, a continuous nationwide antimicrobial surveillance program is required to monitor the emergence of cephalosporin resistance in N. gonorrhoeaeope

Carbapenem-non-susceptible Acinetobacter baumannii of sequence type 92 or its single-locus variants with a G428T substitution in zone 2 of the rpoB gene

OBJECTIVES: to investigate the epidemiological traits of carbapenem-non-susceptible Acinetobacter baumannii (CNSAB) and the usefulness of phylogenetic grouping based on partial rpoB gene sequencing in defining the epidemiological traits of CNSAB. METHODS: a total of 547 non-duplicate clinical isolates of Acinetobacter spp. were collected from 19 hospitals in Korea in 2008. Detection of genes encoding OXA carbapenemases and metallo-β-lactamases was performed by PCR. The epidemiological relationships of the isolates were investigated by multilocus sequence typing and repetitive-sequence-based PCR. The 450 bp sequence (zone 2) of the rpoB gene was amplified and sequenced. RESULTS: molecular characterization of the 272 CNSAB isolates identified five sequence types (STs): ST92, ST75, ST137, ST138 and ST69. The first four of these STs were clustered into clonal complex (CC) 92, sharing alleles at six of seven housekeeping gene loci; ST69 shared alleles at five of seven loci. CNSAB of CC92 carried the bla(OXA-23) gene (n = 169), the bla(OXA-51)-like gene preceded by ISAba1 (n = 89) or both (n = 14). Notably, all CNSAB isolates carried a G428T substitution in zone 2 of the rpoB gene. CONCLUSIONS: CNSAB isolates of CC92 with the G428T substitution in zone 2 of the rpoB gene are disseminated nationwide in Korea. A. baumannii with the single nucleotide substitution may be more likely to acquire carbapenem resistance than are other isolates.ope

Trends in Isolation and Antimicrobial Susceptibility of Enteropathogenic Bacteria in 2001-2010 at a Korean Tertiary Care Hospital

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.ope

Recognition of a Pseudo-Outbreak of Cladosporium Species by Continuous Monitoring of Culture Results

BACKGROUND: Cladosporium spp. are dematiaceous fungi that are commonly isolated from indoor and outdoor environments, including hospital air. This fungus is rarely pathogenic to humans, but has been reported to cause infections of the skin and toenails, as well as sinusitis and pulmonary infections. The monitoring of culture results was conducted to identify the outbreak of an unknown black fungal infection between January and March 2006 in a University hospital, and infection control activity was performed to identify the cause of the outbreak. METHODS: An epidemiological investigation of 22 patients with infections caused by an unknown black fungus was conducted. Microscopic examination and molecular analysis on the internal transcript spacer (ITS) region was performed to identify the black fungus. To detect the source of contamination, a culture of environmental specimens was performed, and then, disinfection of the laboratory was implemented. RESULTS: The patients with black fungi belonged to various departments and wards. No symptoms of fungal infection were recognized on the basis of the survey. The black fungus was identified as Cladosporium spp. on the basis of morphological features and ITS region sequencing. Culturing of environmental specimens was performed in the laboratory. Black fungi were isolated from a specimen from a rack and had the same morphological features with Cladosporium spp. from clinical specimens. After the rack was autoclaved, Cladosporium spp. from clinical specimens was no longer isolated. CONCLUSION: Epidemiological investigation, microscopic examination, and molecular analysis revealed that the sudden increase in the isolation rate of Cladosporium spp. from clinical specimens was the result of a pseudo-outbreak caused by the contamination of a rack. To our knowledge, this is the first report of a pseudo-outbreak of Cladosporium spp. Continuous monitoring of culture results is important to avoid unnecessary labor for nosocomial infection controlope

Chromosomal cephalosporinase in Enterobacter hormaechei as an ancestor of ACT-1 plasmid-mediated AmpC β-lactamase

In this study of the diversity of AmpC β-lactamase in clinical isolates of Enterobacter spp., a strain was found carrying the plasmid-mediated AmpC β-lactamase ACT-1 gene on its chromosome. The strain was identified as Enterobacter hormaechei using phylogenetic analysis of 16S rRNA and hsp60 genes. In addition, the species was confirmed by DNA-DNA hybridization. The genetic environment of the bla(ACT-1) gene was characterized, including the ampR and ampG genes, using a two-step PCR. The amino acid sequences of AmpR at serine 35, arginine 86, glycine 102, aspartic acid 135 and tyrosine 264 were conserved. Measurement of the transcription level of the bla(ACT-1) gene using real-time quantitative PCR showed that it increased 1.98-fold following cefoxitin induction. These results suggest that the plasmid-mediated bla(ACT-1) gene originated from the chromosome of E. hormaechei.ope