Hye Soo Lee

Species Distribution and Susceptibility to Azole Antifungals of Candida Bloodstream Isolates from Eight University Hospitals in Korea

Purpose The incidence of Candida bloodstream infections (BSI) has increased over the past two decades. The rank order of occurrence and the susceptibility to antifungals of the various Candida species causing BSI are important factors driving the establishment of empirical treatment protocols; however, very limited multi-institutional data are available on Candida bloodstream isolates in Korea. Materials and Methods We investigated the susceptibility to azole antifungals and species distribution of 143 Candida bloodstream isolates recovered from eight university hospitals over a six-month period. Minimal inhibitory concentrations (MICs) of fluconazole, itraconazole, and voriconazole for each isolate were determined by the broth microdilution method of the Clinical and Laboratory Standards Institute (CLSI). Results The Candida species recovered most frequently from the blood cultures was C. albicans (49%), followed by C. parapsilosis (22%), C. tropicalis (14%), and C. glabrata (11%). The MIC ranges for the Candida isolates were 0.125 to 64 µg/mL for fluconazole, 0.03 to 2 µg/mL for itraconazole, and 0.03 to 1 µg/mL for voriconazole. Overall, resistance to fluconazole was found in only 2% of the Candida isolates (3/143), while the dose-dependent susceptibility was found in 6% (8/143). The resistance and dose-dependent susceptibility of itraconazole were found in 4% (6/143) and 14% (20/143) of the isolates, respectively. All bloodstream isolates were susceptible to voriconazole (MIC, ≤ 1 µg/mL). Conclusion Our findings show that C. albicans is the most common cause of Candida-related BSI, followed by C. parapsilosis, and that the rates of resistance to azole antifungals are still low among bloodstream isolates in Korea.

Genetic Diversity among Korean Candida albicans Bloodstream Isolates: Assessment by Multilocus Sequence Typing and Restriction Endonuclease Analysis of Genomic DNA by Use of BssHII

ABSTRACT Multilocus sequence typing (MLST) has been successfully applied to the epidemiology of Candida albicans isolates not only within the hospital setting but also in multiple locations nationwide. We performed MLST to investigate the genetic relatedness among bloodstream infection (BSI) isolates of C. albicans recovered from 10 Korean hospitals over a 12-month period. The 156 isolates yielded 112 unique diploid sequence types (DSTs). While 95 DSTs were each derived from a single isolate, 17 DSTs were shared by 61 isolates (39.1%). Interestingly, 111 (71.1%) isolates clustered within previously known clades, and 29 (18.6%) clustered within a new clade that includes strains of Asian origin previously typed as singletons. This MLST study was complemented by restriction endonuclease analysis of genomic DNA using BssHII (REAG-B) in order to evaluate whether strains with identical DSTs and originating from the same hospital corresponded to nosocomial clusters. Importantly, only those isolates with a strong epidemiological relationship showed ≥95% identical REAG-B types. Our results indicate that REAG-B typing can be complementary to MLST but should be limited to the investigation of isolates of identical DSTs and when interhuman transmission is suspected.

Determination of human angiotensin converting enzyme (ACE) gene polymorphisms in erectile dysfunction : Frequency differences of ACE gene polymorphisms according to the method of analysis

Abstract The D polymorphism of angiotensin converting enzyme (ACE) gene has been found to be associated with various diseases, and ACE may also be involved in the pathogenesis of erectile dysfunction. On the other hand, interpretation of the data on the association of DD genotype with various diseases is controversial, due to methodological and technical variations in detection of the polymorphisms. We investigated a possible association between the DD genotype and erectile dysfunction in a Korean population, and compared the frequency of ACE genotypes using our multiplexed PCR method with those based on the conventional PCR method in a sample of erectile dysfunctional and control subjects. There was significant difference in the distribution of ACE genotypes between the erectile dysfunctional (conventional PCR) and the control subjects (multiplexed PCR) (χ2=7.395, p<0.05), but there was no significant difference in the distribution of the genotypes between both groups (χ2=0.815, p<0.05) when our multiplexed PCR method was used. Therefore our results suggest that especially the conventional PCR method for ACE gene polymorphism may require careful control and may need repeated testing to verify the insertion deletion (ID) heterozygotes, and that a multiplexed PCR method can markedly increase the detection rate of the I allele in ID heterozygotes. No association was found between I/D polymorphism and erectile dysfunctional subjects in the Korean population studied.

The relationship between antifungal usage and antifungal susceptibility in clinical isolates of Candida: a multicenter Korean study

There have been very few multicenter studies of the relationship between the use of antifungals and resistance to them. We investigated the antifungal susceptibility of 1,301 clinical isolates of Candida collected from nine Korean hospitals during a 3-month period in 2006 to explore the existence of this type of relationship. Antifungal usage in the preceding year, defined as the daily dose per 1,000 patient days (DDD/1,000 PD), was calculated for each hospital. Resistance to fluconazole, itraconazole, and amphotericin B was detected in 2, 9, and 0.2% of the isolates, respectively. The MIC(50)/MIC(90) values were 0.03/0.125 mg/L for voriconazole, 0.06/0.25 mg/l for caspofungin, and 0.03/0.125 mg/l for micafungin. The total usage of systemic antifungals varied considerably among the nine hospitals, ranging from 6.1 to 96.2 DDD/1,000 PD. No relationship was found between the use of fluconazole (MIC> or =64 mg/l) or itraconazole (MIC> or =1 mg/l) and resistance in the Candida species (P>0.05). However, significant correlations were found between the percentage of Candida isolates that were non-susceptible to fluconazole (MIC> or =16 mg/l) and fluconazole usage (r=0.733, P=0.025) or total antifungal usage (r=0.767, P=0.016).

Antimicrobial Susceptibility of Stenotrophomonas maltophilia Isolates from Korea, and the Activity of Antimicrobial Combinations against the Isolates

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.

Serotype distribution and antibiotic resistance of Streptococcus pneumoniae isolated from invasive infections after optional use of the 7-valent conjugate vaccine in Korea, 2006-2010

This study examined the serotype distribution and antimicrobial resistance of pneumococcal isolates from invasive infections in children between 2006 and 2010, when the 7-valent pneumococcal conjugate vaccine (PCV7) was offered as an optional vaccine in Korea. Among 140 isolates collected from 8 centers, the common serotypes were 19A (22.9%), 19 F (12.1%), and 6B (8.6%). Between 2006 and 2010, PCV7 serotypes decreased from 62.5% to 21.4% (P = 0.002), whereas three 13-valent pneumococcal conjugate vaccine (PCV13)-specific serotypes (3, 6A, and 19A) increased from 18.8% to 42.9% (P = 0.016). Among 102 multidrug-resistant isolates, the proportion of PCV7 serotypes decreased from 65.2% to 21.7% (P = 0.001), and 3 PCV13-specific serotypes increased from 17.4% to 47.8% (P = 0.008). Optional PCV7 vaccination has influenced the proportion of PCV7 serotypes in Korea, resulting in a decrease, whereas the proportions of 3 PCV13-specific serotypes, particularly 19A, have increased.

Absence of antibody to cyclic citrullinated peptide in sera of non-arthritic patients with chronic hepatitis B virus infection

The objective of this study was to investigate if antibody to cyclic citrullinated peptide (anti-CCP) is detected in sera of patients with chronic hepatitis B virus (HBV) infection. Serum anti-CCP and IgA, IgG, and IgM rheumatoid factor (RF) isotypes were measured by enzyme-linked immunosorbent assay on 176 non-arthritic patients with HBV infection. IgA RF, IgG RF, and IgM RF were detectable in 29.5, 21, and 18.8% of the tested sera, respectively, with a total seropositivity rate of 42.7%. Marginally elevated anti-CCP was detected in one patient (0.6%). By regression analysis, there was no statistically significant association between the serum levels of anti-CCP and serum IgA, IgG, or IgM RF (R2 = 0.033, with respective p values of 0.224, 0.297, and 0.334). In conclusion, anti-CCP was rarely detected in non-arthritic patients with HBV infection in contrast to RF. Thus, testing for anti-CCP may be a useful tool for the diagnosis of rheumatoid arthritis in this population.

Accuracy of Species-Level Identification of Yeast Isolates from Blood Cultures from 10 University Hospitals in South Korea by Use of the Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry-Based Vitek MS System

ABSTRACT We assessed the accuracy of yeast bloodstream isolate identification performed over a 1-year period at 10 South Korean hospitals, using the matrix-assisted laser desorption ionization–time of flight (MALDI-TOF)-based Vitek MS system. The overall phenotypic misidentification rate was 3.4% (18/533), with considerable variation between hospitals (0.0% to 19.0%), compared to 1.1% (6/533) for the Vitek MS system.

IS6110-Restriction Fragment Length Polymorphism and Spoligotyping Analysis of Mycobacterium tuberculosis Clinical Isolates for Investigating Epidemiologic Distribution in Korea

The Beijing family of Mycobacterium tuberculosis has been emerging in the world. However, there are few nationwide data of genotypic distribution in Korea. This study aimed to identify the genotypic diversity of clinical isolates of M. tuberculosis and to demonstrate the population of Beijing family in Korea. We collected 96 clinical M. tuberculosis isolates from 11 university hospitals nationwide in Korea from 2008 to 2009. We observed 24 clusters in IS6110-RFLP analysis and 19 patterns in spoligotyping. Seventy-five isolates were confirmed to be Beijing family. Two isolates of the K strain and 12 isolates of the K family strain were also found. We found that drug resistance phenotypes were more strongly associated with Beijing family than non-Beijing family (P=0.003). This study gives an overview of the distribution of genotypes of M. tuberculosis in Korea. These findings indicate that we have to pay more attention to control of M. tuberculosis strains associated with the Beijing family.

Molecular Identification and Amphotericin B Susceptibility Testing of Clinical Isolates of Aspergillus From 11 Hospitals in Korea

Background We investigated the species distribution and amphotericin B (AMB) susceptibility of Korean clinical Aspergillus isolates by using two Etests and the CLSI broth microdilution method. Methods A total of 136 Aspergillus isolates obtained from 11 university hospitals were identified by sequencing the internal transcribed spacer (ITS) and β-tubulin genomic regions. Minimal inhibitory concentrations (MICs) of AMB were determined in Etests using Mueller-Hinton agar (Etest-MH) and RPMI agar (Etest-RPG), and categorical agreement with the CLSI method was assessed by using epidemiological cutoff values. Results ITS sequencing identified the following six Aspergillus species complexes: Aspergillus fumigatus (42.6% of the isolates), A. niger (23.5%), A. flavus (17.6%), A. terreus (11.0%), A. versicolor (4.4%), and A. ustus (0.7%). Cryptic species identifiable by β-tubulin sequencing accounted for 25.7% (35/136) of the isolates. Of all 136 isolates, 36 (26.5%) had AMB MICs of ≥2 µg/mL by the CLSI method. The categorical agreement of Etest-RPG with the CLSI method was 98% for the A. fumigatus, A. niger, and A. versicolor complexes, 87% for the A. terreus complex, and 37.5% for the A. flavus complex. That of Etest-MH was ≤75% for the A. niger, A. flavus, A. terreus, and A. versicolor complexes but was higher for the A. fumigatus complex (98.3%). Conclusions Aspergillus species other than A. fumigatus constitute about 60% of clinical Aspergillus isolates, and reduced AMB susceptibility is common among clinical isolates of Aspergillus in Korea. Molecular identification and AMB susceptibility testing by Etest-RPG may be useful for characterizing Aspergillus isolates of clinical relevance.