Assessment of the Synergistic Effect of Seven Antimicrobial Combinations on Extensively DrugResistant Acinetobacter baumannii Strains / 대한임상미생물학회지

Background@#To solve the difficulty in determining the appropriate treatment regimen for patients infected with extensively drug-resistant Acinetobacter baumannii (XDRAB), it is necessary to develop various strategies to increase the therapeutic effect of antimicrobial agents. The purpose of this study was to select the treatment combination showing the greatest antimicrobial effect among seven candidate antimicrobial substances. @*Methods@#Seven strains of XDRAB were used in this study. The composition of the treatment consisted of colistin as the base and one of the seven antimicrobial substances, doripenem, minocycline, tigecycline, linezolid, fusidic acid, vancomycin, or alyteserin E4K peptide. The interaction between the drugs in each combination was evaluated by measuring the synergy rates using time-kill analysis. @*Results@#The synergy rates of the seven combinations tested in the time-kill assay in this study were as follows, in descending order from the combination with the highest synergy rate: colistin + minocycline (57.1%), colistin + alyteserin E4K (50.0%), colistin + tigecycline (42.9%), colistin + vancomycin (28.6%), colistin + doripenem (14.3%), colistin + fusidic acid (14.3%), and colistin + linzolid (0%). None of the combinations showed antagonism. The three combinations showing bactericidal activity and the rates of their bactericidal activity were colistin + alyteserin E4K combination (33.3%), colistin + minocycline (14.3%), and colistin + vancomycin (14.3%). @*Conclusion@#The colistin + minocycline and colistin + alyteserin E4K treatment combinations, which showed high synergy rates, can be considered as promising candidates for future in vivo experiments evaluating combination therapies.

Evaluation of Synergistic Effect of Combined Treatment with Linalool and Colistin on Multidrug-Resistant Acinetobacter baumannii to Expand Candidate for Therapeutic Option / 대한임상미생물학회지

BACKGROUND: Acinetobacter baumannii infection is a significant health problem worldwide due to increased drug resistance. The limited antimicrobial alternatives for the treatment of severe infections by multidrug-resistant A. baumannii (MDRAB) make the search for other therapeutic options more urgent. Linalool, the major oil compound in Coriandrum sativum, was recently found to have high antibacterial activity against A. baumannii. The purpose of this study was to investigate the synergistic effect of linalool and colistin combinations against MDRAB and extensively drug-resistant A. baumannii (XDRAB).METHODS: A total of 51 strains of A. baumannii clinical isolates, consisting of 10 MDRAB and 41 XDRAB were tested. We determined the minimum inhibitory concentration (MIC) of linalool for the test strains using the broth microdilution method and searched for interactions using the time-kill assay.RESULTS: The time-kill assay showed that the linalool and colistin combination displayed a high rate of synergy (92.1%) (by synergy criteria 2), low rate of indifference (7.8%), and a high rate of bactericidal activity (74.5%) in the 51 clinical isolates of A. baumannii. The synergy rates for the linalool and colistin combination against MDRAB and XDRAB were 96% and 92.1%, respectively. No antagonism was observed for the linalool and colistin combination.CONCLUSION: The combination of linalool and colistin showed a high synergy rate, which may be beneficial for controlling MDRAB infections. Therefore, this combination is a good candidate for in vivo studies to assess its efficacy in the treatment of MDRAB infections.

Role of Efflux Pump Gene adeIJK to Multidrug Resistance in Acinetobacter baumannii Clinical Isolates / 대한임상미생물학회지

BACKGROUND: The emergence of multidrug-resistant Acinetobacter baumannii as a nosocomial pathogen is one of the major public health problems. The aim of this study was to evaluate the role of an efflux pump gene adeJ for the multidrug resistance of A. baumannii clinical isolates.METHODS: Two groups (MDRAB and SAB) of A. baumannii clinical isolates were studied. The SAB group consisted of strains that did not meet the criteria of MDRAB and were susceptible to more categories of antibiotics than MDRAB. Antimicrobial susceptibility results obtained by VITEKII system were used in data analysis and bacterial group allocation. We performed real-time reverse transcription PCR to determine relative expression of adeJ. We compared relative expression of adeJ in comparison groups by considering two viewpoints: i) MDRAB and SAB groups and ii) susceptible and non-susceptible groups for each antibiotic used in this study.RESULTS: The mean value of relative expression of adeJ of MDRAB and SAB groups was 1.4 and 0.92, respectively, and showed significant difference (P=0.002). The mean values of relative expression of adeJ of susceptible and non-susceptible groups to the antibiotics cefepime, ceftazidime, ciprofloxacin, imipenem, meropenem, tigecycline, piperacillin/tazobactam, ticarcillin/clavulanic acid, trimethoprim/sulfamethoxazole, piperacillin, and gentamicin showed statistically significant differences.CONCLUSION: The overexpression of adeIJK might contribute to the multi-drug resistance in A. baumannii clinical isolates. Further, the overexpression of adeIJK might be one of the factors contributing to the resistance to numerous antibiotics.

Serotype Distribution and Antimicrobial Resistance of Invasive and Noninvasive Streptococcus pneumoniae Isolates in Korea between 2014 and 2016

BACKGROUND: Several factors contribute to differences in Streptococcus pneumoniae serotype distribution. We investigated the serotype distribution and antimicrobial resistance of S. pneumoniae isolated between 2014 and 2016 in Korea. METHODS: We collected a total of 1,855 S. pneumoniae isolates from 44 hospitals between May 2014 and May 2016, and analyzed the serotypes by sequential multiplex PCR. We investigated the distribution of each serotype by patient age, source of the clinical specimen, and antimicrobial resistance pattern. RESULTS: The most common serotypes were 11A (10.1%), followed by 19A (8.8%), 3 (8.5%), 34 (8.1%), 23A (7.3%), and 35B (6.2%). The major invasive serotypes were 3 (12.6%), 19A (7.8%), 34 (7.8%), 10A (6.8%), and 11A (6.8%). Serotypes 10A, 15B, 19A, and 12F were more common in patients ≤5 years old, while serotype 3 was more common in patients ≥65 years old compared with the other age groups. The coverage rates of pneumococcal conjugate vaccine (PCV)7, PCV10, PCV13, and pneumococcal polysaccharide vaccine 23 were 11.8%, 12.12%, 33.3%, and 53.6%, respectively. Of the 1,855 isolates, 857 (46.2%) were multi-drug resistant (MDR), with serotypes 11A and 19A predominant among the MDR strains. The resistance rates against penicillin, cefotaxime, and levofloxacin were 22.8%, 12.5%, and 9.4%, respectively. CONCLUSIONS: There were significant changes in the major S. pneumoniae serotypes in the community. Non-PCV13 serotypes increased in patients ≤5 years old following the introduction of national immunization programs with the 10- and 13-polyvalent vaccines.

Serotyping and Antimicrobial Susceptibility of Salmonella Isolated in Korea in 2015 / 대한임상미생물학회지

BACKGROUND: Salmonella is an important pathogen that causes gastroenteritis and sepsis in humans. Recently, changes in serotype prevalence and an increase in antimicrobial resistance have been reported. This study investigated the distribution of Salmonella serotypes and determined the antimicrobial susceptibility of various strains. METHODS: We collected 113 Salmonella isolates other than Salmonella serotype Typhi from 18 university hospitals in 2015. The serotypes were identified by Salmonella antisera O and H according to the Kauffman White scheme. Antimicrobial susceptibility tests for 12 antibiotics were performed using the disk diffusion method or E-test. RESULTS: We identified 22 serotypes. Serotype group B (44.2%) was the most common, followed by groups C (34.5%) and D (21.2%). Salmonella I 4,[5],12:i:- (23.0%), S. Enteritidis (16.8%), and S. Typhimurium (12.4%) were the most common species. Resistance rates for ampicillin, chloramphenicol, ceftriaxone, and trimethoprim/sulfamethoxazole were 46.9%, 18.5%, 8.8%, and 5.3%, respectively. The intermediate resistance rate to ciprofloxacin was 29.2%. Six isolates were extended-spectrum β-lactamase (ESBL) producers, including 5 bla(CTX-M-15) and 1 bla(CTX-M-55). CONCLUSION: There have been changes in the serotype prevalence and antimicrobial resistance of Salmonella in Korea, with a high prevalence of CTX-M 15-positive strains. Continuous monitoring of Salmonella serotypes and antimicrobial resistance is warranted.

Distribution of adeG, adeB, adeE, adeY, abeM, and adeJ Efflux Pump Genes in Clinical Isolates of Acinetobacter Species from Korea

BACKGROUND: The aim of the present study was to determine the frequency of six efflux pump genes in Acinetobacter clinical isolates collected from South Korean hospitals. METHODS: In this study, we used a total of 339 Acinetobacter strains, comprising 279 Acinetobacter calcoaceticus–Acinetobacter baumannii (ACB) complex and 60 non-ACB complex strains. We performed specific PCR assays to detect adeG, adeB, adeE, adeY, abeM, and adeJ, transporter genes of the multidrug efflux pumps AdeFGH, AdeABC, AdeDE, AdeXYZ, AbeM, and AdeIJK, respectively. RESULTS: Frequencies of six efflux pump genes varied according to the species of Acinetobacter. Frequencies of adeE, abeM, and adeJ between A. baumannii group and A. nosocomialis group were found to be significantly different. Significant differences were found in the frequencies of adeB, adeE, adeY, and adeJ among the susceptible A. baumannii (SAB), multidrug-resistant A. baumannii (MDRAB), and extensively drug-resistant A. baumannii (XDRAB) groups within the 154 strains of A. baumannii. The frequencies of efflux pump genes in imipenem-susceptible and imipenem-nonsusceptible groups were significantly different for adeB, adeY, and adeJ. The frequencies of efflux pump genes in ciprofloxacin-susceptible and ciprofloxacin-nonsusceptible groups were significantly different for adeB and adeY. No significant difference was found in the frequency of efflux pump genes among groups sampled from different regions of Korea, across 86 strains of A. baumannii collected in 2012. CONCLUSIONS: The frequencies of six efflux pump genes obtained in this study demonstrate the fundamental epidemiological feature of efflux pump genes in Korean Acinetobacter clinical isolates.

Primary Myelofibrosis with MPL S505N Mutation: The First Case Reported in Korea

MPL mutation is an important molecular marker in myeloproliferative neoplasms (MPN). Although MPL W515 is a hot spot for missense mutations in MPN, MPL S505 mutations have been reported in both familial and non-familial MPN. A 72-year-old male visited the hospital, complaining mainly of dizziness and epistaxis. Leukocytosis, anemia, thrombocytopenia, tear drop cells, nucleated RBCs, and myeloblasts were observed in both complete blood cell counts and peripheral blood smears. Bone marrow aspiration failed due to dilution with peripheral blood. BM biopsy indicated hypercellular marrow, megakaryocytic proliferation with atypia, and grade 3 reticulin fibrosis. Conventional cytogenetics results were as follows: 46,XY,del(13)(q12q22)[19]/46,XY[1]. Molecular studies did not detect JAK2 V617F, BCR/ABL translocation, JAK2 exon 12, and CALR exon 9 mutations. The MPL S505N mutation was verified by colony PCR and Sanger sequencing following gene cloning. Based on the above findings, a diagnosis of overt primary myelofibrosis (PMF) was indicated. Mutation studies of buccal and T cells were not conducted. Further, family members were not subjected to mutation studies. Therefore, we were unable to determine whether this mutation was familial or non-familial. Six months after the first visit to the hospital, the patient died due to pneumonia and sepsis. Thrombotic symptoms or major bleeding events did not develop during the survival period following diagnosis of PMF. To the best of our knowledge, this may be the first reported case of PMF with the MPL S505N mutation in Korea.

Comparison of the Utility of dnaJ and 16S rDNA Sequences for Identification of Clinical Isolates of Vibrio Species

BACKGROUND: Among the many Vibrio species that can cause infections in humans, several species can cause a fatal outcome. Therefore, accurate identification of Vibrio species is very important. Since some species show atypical phenotypic features, selecting an appropriate molecular method is necessary to avoid misdiagnosis. METHODS: Vibrio clinical isolates (N=53) and reference strains (N=8) were used in this study. We analyzed the following sequences for identification: dnaJ gene, 16S rDNA, gyrase B (gyrB) V. vulnificus-specific sequence, gyrB V. navarrensis-specific sequence, and V. vulnificus hemolysin gene PCR (Vvh PCR). We performed phylogenetic analysis of the 16S rDNA, dnaJ, and gyrB sequences. Final identification was based on the combined results of all tests described above. Concordance of the 16S rDNA and dnaJ sequence analysis was measured using the Chi-square test. RESULTS: The 61 Vibrio strains were identified as follows, in descending order: V. vulnificus (78.69%), V. parahaemolyticus (6.56%), V. navarrensis (4.92%), V. mimicus (1.64%), V. cholera (1.64%), V. furnissii (1.64%), V. alginolyticus (1.64%), and Grimontia hollisae (1.64%). The accuracy rates of the dnaJ gene and 16S rDNA sequence for identification were 91.80% and 86.89%, respectively. The 16S rDNA and dnaJ sequences showed a concordance rate of 0.45, which indicates moderate agreement. CONCLUSIONS: Our results suggest that analysis of the dnaJ sequence may be a useful method for the identification of clinical isolates of Vibrio species, especially for distinguishing between closely related Vibrio species.

Assessment of Efflux Activity Using H33342 Accumulation in Tigecycline-Resistant Acinetobacter baumannii Clinical Isolates / 대한임상미생물학회지

BACKGROUND: Tigecycline resistance has emerged recently and has shown diverse mechanisms. The aim of this study was to assess the role of efflux activity in tigecycline resistance in 120 clinical isolates of A. baumannii using two methods: the H33342 accumulation assay and adeB real-time reverse transcriptase polymerase chain reaction. In addition, we analyzed the correlation between the expression level of adeB and H33342 accumulation level. METHODS: A. baumannii clinical isolates was divided into tigecycline-resistant (49 strains), intermediate (40 strains), and susceptible (31 strains) groups. The H33342 accumulation was measured in the absence or presence of the efflux pump inhibitor carbonyl cyanide 3-chlorophenylhydrazone (CCCP). Real-time RT-PCR was performed to determine the relative expression of the adeB gene in A. baumannii clinical isolates. RESULTS: The level of H33342 accumulation in the resistant group was relatively lower than those in the other groups. The addition of CCCP caused a significantly increased fold change in H33342 accumulation in the tigecycline-resistant group. Significant difference in the fold change level in H33342 accumulation was found between tigecycline-susceptible and resistant isolates. Those findings support the role of efflux pumps of which substrates are H33342 in the resistance of tigecycline. Significant differences in the relative expression levels of adeB were shown between tigecycline-susceptible and resistant groups also. CONCLUSION: The results showed that several efflux pumps of which substrates were H33342 can contribute to tigecycline resistance. The adeB overexpression can also contribute to tigecycline resistance. It is possible that efflux pumps other than adeB efflux pumps contribute to tigecycline resistance because there was no correlation between fold change level in H33342 accumulation and adeB expression level.

Increasing Resistance to Extended-Spectrum Cephalosporins, Fluoroquinolone, and Carbapenem in Gram-Negative Bacilli and the Emergence of Carbapenem Non-Susceptibility in Klebsiella pneumoniae: Analysis of Korean Antimicrobial Resistance Monitoring System

BACKGROUND: National surveillance of antimicrobial resistance becomes more important for the control of antimicrobial resistance and determination of treatment guidelines. We analyzed Korean Antimicrobial Resistance Monitoring System (KARMS) data collected from 2013 to 2015. METHODS: Of the KARMS participants, 16 secondary or tertiary hospitals consecutively reported antimicrobial resistance rates from 2013 to 2015. Data from duplicate isolates and institutions with fewer than 20 isolates were excluded. To determine the long-term trends, previous KARMS data from 2004 to 2012 were also considered. RESULTS: The prevalence of methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium from 2013 to 2015 was 66–72% and 29–31%, respectively. The resistance rates of Escherichia coli to cefotaxime and cefepime gradually increased to 35% and 31%, respectively, and fluoroquinolone resistance reached 48% in 2015. The resistance rates of Klebsiella pneumoniae to cefotaxime, cefepime, and carbapenem were 38–41%, 33–41%, and <0.1–2%, respectively, from 2013 to 2015. The carbapenem susceptibility rates of E. coli and K. pneumoniae decreased from 100% and 99.3% in 2011 to 99.0% and 97.0% in 2015, respectively. The resistance rate of Pseudomonas aeruginosa to carbapenem increased to 35% and the prevalence of carbapenem-resistant Acinetobacter baumannii increased from 77% in 2013 to 85% in 2015. CONCLUSIONS: Between 2013 and 2015, the resistance rates of E. coli to third- and fourth-generation cephalosporins increased continuously, while carbapenem-susceptibility gradually decreased, particularly in K. pneumoniae. The prevalence of carbapenem-resistant P. aeruginosa and A. baumannii increased significantly; therefore, few treatment options remain for these resistant strains.

In Vitro Interactions of Antibiotic Combinations of Colistin, Tigecycline, and Doripenem Against Extensively Drug-Resistant and Multidrug-Resistant Acinetobacter baumannii

BACKGROUND: Acinetobacter baumannii infections are difficult to treat owing to the emergence of various antibiotic resistant isolates. Because treatment options are limited for multidrug-resistant (MDR) A. baumannii infection, the discovery of new therapies, including combination therapy, is required. We evaluated the synergistic activity of colistin, doripenem, and tigecycline combinations against extensively drug-resistant (XDR) A. baumannii and MDR A. baumannii. METHODS: Time-kill assays were performed for 41 XDR and 28 MDR clinical isolates of A. baumannii by using colistin, doripenem, and tigecycline combinations. Concentrations representative of clinically achievable levels (colistin 2 microg/mL, doripenem 8 microg/mL) and achievable tissue levels (tigecycline 2 microg/mL) for each antibiotic were used in this study. RESULTS: The colistin-doripenem combination displayed the highest rate of synergy (53.6%) and bactericidal activity (75.4%) in 69 clinical isolates of A. baumannii. Among them, thedoripenem-tigecycline combination showed the lowest rate of synergy (14.5%) and bacteri-cidal activity (24.6%). The doripenem-tigecycline combination showed a higher antagonistic interaction (5.8%) compared with the colistin-tigecycline (1.4%) combination. No antagonism was observed for the colistin-doripenem combination. CONCLUSIONS: The colistin-doripenem combination is supported in vitro by the high rate of synergy and bactericidal activity and lack of antagonistic reaction in XDR and MDR A. baumannii. It seems to be necessary to perform synergy tests to determine the appropri-ate combination therapy considering the antagonistic reaction found in several isolates against the doripenem-tigecycline and colistin-tigecycline combinations. These findings should be further examined in clinical studies.

Two Concurrent Chromosomal Aberrations Involving Three-way t(3;21;8)(p21;q22;q22) and Two-way t(2;11)(q31;p15) Translocations in a Case of de novo Acute Myeloid Leukemia

One of the most frequent structural chromosomal anomaly is t(8;21)(q22;q22) that occurs in approximately 5-15% of all acute myeloid leukemia (AML). However, t(3;21)(p21;q22) and t(2;11)(q31;p15) translocations are rarely reported in AML. Here, we report a unique case of AML with two translocations, t(3;21;8)(p21;q22;q22) and t(2;11)(q31;p15). Using multiplex reverse transcription polymerase chain reaction, we identified a RUNX1-RUNX1T1 fusion gene. Following a second relapse, the patient did not respond to therapy and died 55 months following the first diagnosis. We believe that this is the first case describing concurrent chromosomal aberrations involving three-way t(3;21;8) and two-way t(2;11) translocations in de novo acute myeloid leukemia.

Mycobacterium marinum Infection on the Face Diagnosed by Polymerase Chain Reaction Amplification and Direct Sequencing

No abstract available.

A Novel Four-Way Translocation t(5;9;22;18)(q31;q34;q11.2;q21) in a Patient with Chronic Myelogenous Leukemia

Chronic myelogenous leukemia (CML) is characterized by the presence of the Philadelphia chromosome, which is generated by a reciprocal t(9;22)(q34;q11) translocation. Variant Philadelphia chromosomes, found in 5-10% of CML cases, are a result of translocations involving other chromosomes, in addition to 9 and 22. These four-way Philadelphia chromosome translocations are very rare; only about 60 patients with such chromosomes have been described. Here, we report a CML case with a novel four-way variant Philadelphia chromosome. A conventional chromosome analysis of bone marrow cells revealed a 46,XY,t(5;9;22;18)(q31;q34;q11.2;q21) karyotype, which was confirmed by multicolor fluorescence in situ hybridization. The major BCR-ABL1 fusion gene was detected by reverse transcription-nested PCR. The patient was treated with imatinib. Twelve months after treatment, he demonstrated a complete hematologic response and chromosome analysis showed that he had a normal karyotype.

A Novel Four-Way Translocation t(5;9;22;18)(q31;q34;q11.2;q21) in a Patient with Chronic Myelogenous Leukemia

Chronic myelogenous leukemia (CML) is characterized by the presence of the Philadelphia chromosome, which is generated by a reciprocal t(9;22)(q34;q11) translocation. Variant Philadelphia chromosomes, found in 5-10% of CML cases, are a result of translocations involving other chromosomes, in addition to 9 and 22. These four-way Philadelphia chromosome translocations are very rare; only about 60 patients with such chromosomes have been described. Here, we report a CML case with a novel four-way variant Philadelphia chromosome. A conventional chromosome analysis of bone marrow cells revealed a 46,XY,t(5;9;22;18)(q31;q34;q11.2;q21) karyotype, which was confirmed by multicolor fluorescence in situ hybridization. The major BCR-ABL1 fusion gene was detected by reverse transcription-nested PCR. The patient was treated with imatinib. Twelve months after treatment, he demonstrated a complete hematologic response and chromosome analysis showed that he had a normal karyotype.

Comparison of the Vitek 2, API 20A, and 16s rRNA Gene Sequencing for the Identification of Anaerobic Bacteria / 대한임상미생물학회지

BACKGROUND: Recently, genotypic identification of anaerobes is emerging as an alternative to the phenotypic method. In this study, we evaluated the performance of Vitek 2, API 20A and 16s rRNA gene sequencing for the identification of anaerobic bacteria. METHODS: A total of 35 anaerobe reference strains were identified using Vitek 2, API 20A and 16s rRNA gene sequencing. We evaluated the performance of three methods on the basis of the accurate identification rates. RESULTS: The Vitek 2, API 20A and 16s rRNA gene sequencing identified 54.3, 15.4, and 94.3% of test strains correctly at the species level and identified 77.1, 42.3, and 100% at the genus level, respectively. Results of the McNemar's test showed that there was a significant difference between each of the three identification methods in species level identification (P value<0.05). CONCLUSION: 16s rRNA gene sequencing showed better performance than Vitek 2 or API 20A for anaerobic bacteria. Considering its excellent performance, 16s rRNA gene sequencing may be useful for accurate identification of anaerobic bacteria that cannot be correctly identified by phenotypic methods.

Recent Trends in Antimicrobial Resistance in Intensive Care Units in Korea / 병원감염관리

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.

Nasal Colonization and Molecular Characterization of Methicillin-Resistant Staphylococcus aureus among Hemodialysis Patients in 7 Korean Hospitals / 병원감염관리

BACKGROUND: Staphylococcus aureus is a major bacteremia-causing pathogen in hemodialysis patients, frequently colonizing patient skin and mucosa. Active infection control is necessary to prevent methicillin-resistant S. aureus (MRSA) infection in hospitals; however, the spread of community-associated MRSA has recently become a concern for MRSA infection control. We evaluated the nasal colonization of MRSA among hemodialysis patients and the molecular characterization of the MRSA isolates. METHODS: Nasal swabs were obtained from 482 hemodialysis patients in 7 nationwide hospitals in November 2009, and cultured for MRSA colonization. Swabs were inoculated and cultured in 6.5% NaCl tryptic soy broth, then subcultured on MRSASelect medium (Bio-Rad, Hercules, CA) for 20-24 h. Multiplex PCR was performed to analyze staphylococcal cassette chromosome mec (SCCmec) types of MRSA isolates. RESULTS: Of 482 hemodialysis patients, 57 (11.8%) carried MRSA, ranging from 6.7% to 19.0%. Among the 57 MRSA isolates, we identified 3 (5.3%) SCCmec II, 1 (1.8%) SCCmec IIA, 30 (52.6%) SCCmec IIB, 1 (1.8%) SCCmec III, 6 (10.5%) SCCmec IV, and 16 (28.1%) SCCmec IVA subtypes. CONCLUSION: The MRSA carriage rate (11.8%) of hemodialysis patients in this study was high. The SCCmec IIB subtype, a healthcare-associated strain, was the predominant strain, although SCCmec IV isolates, typically found in community-associated MRSA infections, were also frequently observed. To prevent healthcare-associated MRSA infections in hemodialysis patients, standardized infection control measures should be performed, and efforts to reduce MRSA carriage rates should be considered.

Basic Concepts of Bacterial Taxonomy / 대한임상미생물학회지

The three components of taxonomy are classification, nomenclature and identification. Traditionally, bacterial classification and identification were performed based on the morphology and the biochemical data of the bacteria. In newer theories, or so-called natural concepts, the relationships between bacteria are based on the overall similarities of both the phenotypic and genotypic characteristics. The polyphasic taxonomy, or current taxonomy, describes the integration of all of the available genotypic, phenotypic, and phylogenetic information into a consensus type of general-purpose classification. When routine identification methods that are based on the biochemical tests fail, alternative procedures such as complete 16s rRNA gene sequence analysis are required. Although the results of 16s rRNA gene sequence analysis have not been fully discriminatory to differentiate closely related species, they may guide the additional analyses that are required for species identification.

Comparison of MicroScan and Phoenix Automated Systems for Detection of Extended-Spectrum beta-Lactamase-Producing Escherichia coli and Klebsiella pneumoniae

The aim of this study was to evaluate the performances of MicroScan (Siemens Healthcare, USA) and Phoenix (Becton Dickinson Diagnostic Systems, USA) automated systems for the detection of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae. ESBL-producers were detected from 18 E. coli strains and 26 K. pneumoniae strains using MicroScan, Phoenix, and double-disk synergy test (DDST). The ESBL types were determined by PCR direct sequencing. ESBL genes were detected in 38 (86.4%) of the 44 test strains. The sensitivities of MicroScan, Phoenix, and DDST were 94.6%, 79%, and 89.5%, respectively. Both MicroScan and Phoenix provided acceptable results for the examination of clinical isolates.