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The clonal transmission of fluconazole-resistant Candida glabrata isolates within hospitals has seldom been analyzed by whole-genome sequencing (WGS). We performed WGS on 79 C . glabrata isolates, comprising 31 isolates from three premature infants with persistent C. glabrata bloodstream infection despite antifungal treatment in the same neonatal intensive care unit (NICU) in 2022 and 48 (27 fluconazole-resistant and 21 fluconazole-susceptible dose-dependent) bloodstream isolates from 48 patients in 15 South Korean hospitals from 2010 to 2022. Phylogenetic analysis based on WGS single-nucleotide polymorphisms (SNPs) distinguished the 79 isolates according to multilocus sequence typing (MLST) (17 sequence type [ST]3, 13 ST7, two ST22, 41 ST26, four ST55, and two ST59 isolates) and unveiled two possible clusters of nosocomial transmission among ST26 isolates. One cluster from two premature infants with overlapping NICU hospitalizations in 2022 encompassed 15 fluconazole-resistant isolates harboring pleiotropic drug-resistance transcription factor (Pdr1p) P258L (13 isolates) or N1086I (two isolates), together with 10 fluconazole-susceptible dose-dependent isolates lacking Pdr1p SNPs. The other cluster indicated unforeseen clonal transmission of fluconazole-resistant bloodstream isolates among five patients (four post-lung transplantation and one with diffuse interstitial lung disease) in the same hospital over 8 months. Among these five isolates, four obtained after exposure to azole antifungals harbored distinct Pdr1p SNPs (N1091D, E388Q, K365E, and R376Q). The findings reveal the transmission patterns of clonal bloodstream isolates of C. glabrata among patients undergoing antifungal treatment, exhibiting different levels of fluconazole susceptibility or distinct Pdr1p SNP profiles., Importance: The prevalence of fluconazole-resistant bloodstream infections caused by Candida glabrata is increasing globally, but the transmission of these resistant strains within hospitals has rarely been documented. Through whole-genome sequencing and epidemiological analyses, this study identified two potential clusters of C. glabrata bloodstream infections within the same hospital, revealing the transmission of clonal C. glabrata strains with different levels of fluconazole susceptibility or distinct transcription factor pleiotropic drug resistance protein 1 (Pdr1p) single-nucleotide polymorphism profiles among patients receiving antifungal therapy., Competing Interests: The authors declare no conflict of interest.

Background: Although sonication is a valuable diagnostic tool for periprosthetic joint infections (PJI), it is not commonly utilized. We analyzed sonicate and intraoperative tissue culture results obtained from three hospitals to define the microbial etiology of PJIs in Korea. Furthermore, we investigated necessity of conducting regular fungal and mycobacterial cultures., Methods: We retrospectively analyzed data for patients with suspected orthopedic-related infections between 2017 and 2022, who had undergone prostheses removal surgery. We included 193 patients with suspected PJIs, and bacterial (n = 193), fungal (n = 193), and mycobacterial (n = 186) cultures were conducted on both sonicate and intraoperative tissue samples. The diagnosis of PJI was based on the European Bone and Joint Infection Society (EBJIS) criteria., Results: Out of 193 patients, 121 (62.7%) had positive sonicate cultures, while 112 (58.0%) had positive periprosthetic tissue cultures. According to EBJIS criteria, a total of 181 patients were diagnosed with PJI, and 141 patients received microbiological confirmation through sonicate fluid culture or tissue culture. Of the 181 patients, 28 were classified with acute PJI (within 3 months of implantation) and 153 with chronic PJI. Among 141 patients, staphylococci were the most common organisms, accounting for 51.8% of cases, followed by Gram-negative organisms (15.6%), fungus (8.5%), and mycobacteria (3.5%). Nearly 91.7% of fungal isolates were Candida species, which also grew in bacterial cultures. In total, 11 cases cultured positive only in tissue culture, whereas 20 cases cultured positive only in sonicate culture. The antibiotic treatment plans were adjusted according to culture results., Conclusions: Utilizing sonicate culture has greatly assisted in identifying pathogens responsible for chronic indolent PJIs, allowing suitable antimicrobial treatment. Based on few cases involving non-Candida and mycobacterial infections, it appears that routine fungal and mycobacterial cultures may not be necessary., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Lee et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Introduction: The rapid spread of COVID-19 worldwide within 2 months demonstrated the vulnerability of the world's population to infectious diseases. In 2015, the Global Antimicrobial Resistance and Use Surveillance System (GLASS) was launched to combat antimicrobial resistance (AMR). However, there has been no comprehensive assessment of the decade-long global battle against AMR based on GLASS data., Methods: South Korea established Kor-GLASS (Korean-GLASS) to proactively monitor data quality and enable international collaborations. A unique feature of Kor-GLASS is the quality control center (QCC), which uses network hubs and ensures standardized, high-quality data through interlaboratory proficiency testing (IPT) and external quality assessment (EQA). In addition, the QCC multifaceted endeavors for integrated data quality management., Results: Since 2020, high-quality AMR data have indicated fluctuating antibiotic resistance rates in South Korea. This trend does not align with the decrease in antibiotic usage seen in humans but coincides with non-human antibiotic sales, indicating a need for greater monitoring of non-human antibiotic resistance. Comprehensive and robust management taking account of the intricate interplay among humans, animals, and the environment is essential. Kor-GLASS has been expanded into a "One Health" multiagency collaborative initiative., Discussion: Although a standardized solution is not suitable for all countries, it must align with the local context and international standards. A centralized top-down management structure such as that of the QCC is essential to ensure continuous data quality coordination. Sustained efforts and surveillance systems are crucial for monitoring and managing AMR and safeguarding human health., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Kim, Park, Kim, Kim, Shin, Kim, Uh, Kim, Shin, Jeong and Park.)

Background: This study analyzed the genetic traits and fitness costs of vancomycin-resistant Enterococcus faecium (VREfm) blood isolates carrying Tn1546-type transposons harboring the vanA operon., Methods: All E. faecium blood isolates were collected from eight general hospitals in South Korea during one-year study period. Antimicrobial susceptibility testing and vanA and vanB PCR were performed. Growth rates of E. faecium isolates were determined. The vanA-positive isolates were subjected to whole genome sequencing and conjugation experiments., Results: Among 308 E. faecium isolates, 132 (42.9%) were positive for vanA. All Tn1546-type transposons harboring the vanA operon located on the plasmids, but on the chromosome in seven isolates. The plasmids harboring the vanA operon were grouped into four types; two types of circular, nonconjugative plasmids (Type A, n = 50; Type B, n = 46), and two types of putative linear, conjugative plasmids (Type C, n = 16; Type D, n = 5). Growth rates of vanA-positive E. faecium isolates were significantly lower than those of vanA-negative isolates (P < 0.001), and reduction in growth rate under vancomycin pressure was significantly larger in isolates harboring putative linear plasmids than in those harboring circular plasmids (P = 0.020)., Conclusions: The possession of vanA operon was costly to bacterial hosts in antimicrobial-free environment, which provide evidence for the importance of reducing vancomycin pressure for prevention of VREfm dissemination. Fitness burden to bacterial hosts was varied by type and size of the vanA operon-harboring plasmid., (© 2024. The Author(s).)

Acquired fluconazole resistance (FR) in bloodstream infection (BSI) isolates of Candida albicans is rare. We investigated the FR mechanisms and clinical features of 14 fluconazole non-susceptible (FNS; FR and fluconazole-susceptible dose-dependent) BSI isolates of C. albicans recovered from Korean multicenter surveillance studies during 2006-2021. Mutations causing amino acid substitutions (AASs) in the drug-target gene ERG11 and the FR-associated transcription factor genes TAC1 , MRR1 , and UPC2 of the 14 FNS isolates were compared with those of 12 fluconazole-susceptible isolates. Of the 14 FNS isolates, eight and seven had Erg11p (K143R, F145L, or G464S) and Tac1p (T225A, R673L, A736T, or A736V) AASs, respectively, which were previously described in FR isolates. Novel Erg11p, Tac1p, and Mrr1p AASs were observed in two, four, and one FNS isolates, respectively. Combined Erg11p and Tac1p AASs were observed in seven FNS isolates. None of the FR-associated Upc2p AASs were detected. Of the 14 patients, only one had previous azole exposure, and the 30-day mortality rate was 57.1% (8/14). Our data show that Erg11p and Tac1p AASs are likely to contribute to FR in C. albicans BSI isolates in Korea and that most FNS C. albicans BSIs develop without azole exposure.

We newly detected two (sinking and floating) phenotypes of Candida parapsilosis among bloodstream infection (BSI) isolates from Korean hospitals and assessed their microbiological and clinical characteristics. During the performance of a Clinical and Laboratory Standards Institute (CLSI) broth microdilution antifungal susceptibility testing, the sinking phenotype had a characteristic smaller button-like appearance because all yeast cells sank to the bottoms of the CLSI U-shaped round-bottom wells, whereas the floating phenotype comprised dispersed cells. Phenotypic analysis, antifungal susceptibility testing, ERG11 sequencing, microsatellite genotyping, and clinical analysis were performed on C. parapsilosis isolates from 197 patients with BSI at a university hospital during 2006 to 2018. The sinking phenotype was detected in 86.7% (65/75) of the fluconazole-nonsusceptible (FNS) isolates, 92.9% (65/70) of the isolates harboring the Y132F ERG11 gene substitution, and 49.7% (98/197) of all isolates. Clonality was more frequently observed for the Y132F-sinking isolates (84.6% [55/65]) than for all other isolates (26.5% [35/132]; P <  0.0001). Annual incidence of Y132F-sinking isolates increased 4.5-fold after 2014, and two dominant genotypes, persistently recovered for 6 and 10 years, accounted for 69.2% of all Y132F-sinking isolates. Azole breakthrough fungemia (odds ratio [OR], 6.540), admission to the intensive care unit (OR, 5.044), and urinary catheter placement (OR, 6.918) were independent risk factors for BSIs with Y132F-sinking isolates. The Y132F-sinking isolates exhibited fewer pseudohyphae, a higher chitin content, and lower virulence in the Galleria mellonella model than the floating isolates. These long-term results illustrate the increasing BSIs caused by clonal transmission of the Y132F-sinking isolates of C. parapsilosis. IMPORTANCE We believe that this is the first study describe the microbiological and molecular characteristics of bloodstream isolates of C. parapsilosis in Korea exhibiting two phenotypes (sinking and floating). An important aspect of our findings is that the sinking phenotype was observed predominantly in isolates harboring a Y132F substitution in the ERG11 gene (92.9%), fluconazole-nonsusceptible (FNS) isolates (86.7%), and clonal BSI isolates (74.4%) of C. parapsilosis. Although the increase in the prevalence of FNS C. parapsilosis isolates has been a major threat in developing countries, in which the vast majority of candidemia cases are treated with fluconazole, our long-term results show increasing numbers of BSIs caused by clonal transmission of Y132F-sinking isolates of C. parapsilosis in the period with an increased echinocandin use for candidemia treatment in Korea, which suggests that C. parapsilosis isolates with the sinking phenotype continue to be a nosocomial threat in the era of echinocandin therapy., Competing Interests: The authors declare no conflict of interest.

This study compared the accuracy of a new MALDI-TOF mass spectrometry system, ASTA MicroIDSys system, with that of MALDI Biotyper system for the identification of reference and clinical bacterial and yeast strains. The identification accuracy of the 2 systems was compared using a total of 406 strains comprising 142 aerobic and 180 anaerobic bacterial strains and 84 yeast strains. The genus and species identification rates were 98.0% and 89.4% using MicroIDSys and 96.1% and 89.4% using Biotyper, respectively. The species identification rates of MicroIDSys and Biotyper for aerobic bacteria were 93.0% and 97.2%, respectively, and those for anaerobic bacteria were 85.6% and 81.7%, respectively. The accuracy of yeast identification at the species level was 91.7% using MicroIDSys and 92.9% using Biotyper. These findings indicate that MicroIDSys could be useful for the accurate identification of bacteria and yeast in clinical microbiology laboratories., (Copyright © 2022. Published by Elsevier Inc.)

Salmonella is one of the major causes of food-borne infections. We investigated the serotype distribution and antimicrobial resistance of Salmonella isolates collected in Korea between January 2016 and December 2017. In total, 669 Salmonella isolates were collected from clinical specimens at 19 university hospitals. Serotyping was performed according to the Kauffmann-White scheme, and antimicrobial susceptibility was tested using Sensititre EUVSEC plates or disk diffusion. Among the strains, C (39.8%) and B (36.6%) were the most prevalent serogroups. In total, 51 serotypes were identified, and common serotypes were S . enterica serovar I 4,[5],12:i:- (16.7%), S . Enteritidis (16.1%), S . Bareilly (14.6%), S . Typhimurium (9.9%), and S . Infantis (6.9%). The resistance rates to ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole were 32.6%, 12.1%, and 8.4%, respectively. The resistance rates to cefotaxime and ciprofloxacin were 8.1% and 3.0%, respectively, while 5.4% were multidrug-resistant. S. enterica serovar I 4,[5],12:i:- and S . Enteritidis were highly prevalent, and there was an increase in rare serotypes. Multidrug resistance and ciprofloxacin resistance were highly prevalent. Periodic investigations of Salmonella serotypes and antimicrobial resistance are needed.

Background: The prevalence of extended-spectrum β-lactamase-producing Escherichia coli (ESBL-EC) in the community has increased worldwide due to multifactorial reasons. ESBL-EC bloodstream infection (BSI) complicates the decision for proper antimicrobial administration. In this multicenter study, we investigated the prevalence, risk factors, and molecular background of community-onset (CO) ESBL-EC BSI., Methods: We included data for all episodes of ESBL-EC BSI of community origin from May 2016 to April 2017 obtained from the Korean national antimicrobial resistance surveillance system, which comprises six sentinel hospitals. Data, including previous history of admission and use of antimicrobials and medical devices before BSI, were collected, along with microbiological analysis results., Results: Among 1,189 patients with CO BSI caused by E. coli , 316 (27%) were identified as ESBL producers. History of admission, especially to a long-term care hospital (LTCH), and previous use of β-lactams/β-lactamase inhibitors, carbapenem, lincosamide, aminoglycoside, and extended-spectrum cephalosporin were independent risk factors for CO ESBL-EC BSI; admission to an LTCH showed the highest odds ratio (3.8, 95% confidence interval 2.3-6.1). The most common genotype was CTX-M-15 (N=131, 41%), followed by CTX-M-14 (N=86, 27%). ST131 was the most common sequence type among ESBL-EC groups (57%)., Conclusions: In Korea, 27% of CO E. coli BSI were caused by ESBL producers. From perspectives of empirical treatment and infection control, history of admission to an LTCH and antimicrobial use should be noted.

The correct identification of filamentous fungi is challenging. We evaluated the performance of the VITEK MS v3.0 system (bioMérieux, Marcy-l'Étoile, France) for the identification of a wide spectrum of clinically relevant filamentous fungi using a Korean collection. Strains that were added to the upgraded v3.2 database were additionally identified by the VITEK MS v3.2 system. Of the 105 tested isolates, including 37 Aspergillus (nine species), 41 dermatophytes (seven species), and 27 other molds (17 species), 43 (41.0%) showed "no identification" or "multiple species identification" results at the initial VITEK MS testing; these isolates were retested using the same method. Compared with sequence-based identification, the correct identification rate using VITEK MS for Aspergillus , dermatophytes, other molds, and total mold isolates was 67.6%, 56.1%, 48.1%, and 58.1% at the initial testing and 94.6%, 78.0%, 55.6%, and 78.1% with retesting, respectively. Following retesting, 19 (18.1%) and two (1.9%) isolates showed "no identification" and "misidentification" results, respectively. VITEK MS reliably identified various filamentous fungi recovered in Korea, with a very low rate of misidentification.

Stool examination is the gold standard for the detection of intestinal parasites. We assessed the performance of a newly developed AVE-562 analyzer (AVE Science & Technology Co., Hunan, China) for the vision-based detection of eggs of Clonorchis sinensis -the most common intestinal parasite in Korea-in stool samples. In total, 30 stool samples with a high or low egg count or without eggs (as negative control samples) (N=10 each) were prepared and analyzed. The performance of the AVE-562 analyzer was compared with that of the formalin-ether concentration (FEC) method. The overall correct identification rate of the AVE-562 analyzer based on FEC results was 66.6%. The sensitivity, specificity, positive predictive value, and negative predictive value of the AVE-562 analyzer for detecting C. sinensis eggs were 36.4%, 100.0%, 100.0%, and 73.1%, respectively. The average time required to run five tests simultaneously was 27 min using the AVE-562 analyzer and 58 min using the FEC method. Although the AVE-562 analyzer enables rapid and convenient stool examination, its sensitivity needs to be improved, particularly considering the prevalence of low-burden C. sinensis infection in Korea.

This study was performed to evaluate the impacts of vanA positivity of Enterococcus faecium exhibiting diverse susceptibility phenotypes to glycopeptides on clinical outcomes in patients with a bloodstream infection (BSI) through a prospective, multicenter, observational study. A total of 509 patients with E. faecium BSI from eight sentinel hospitals in South Korea during a 2-year period were enrolled in this study. Risk factors of the hosts and causative E. faecium isolates were assessed to determine associations with the 30-day mortality of E. faecium BSI patients via multivariable logistic regression analyses. The vanA gene was detected in 35.2% (179/509) of E. faecium isolates; 131 E. faecium isolates exhibited typical VanA phenotypes (group vanA -VanA), while the remaining 48 E. faecium isolates exhibited atypical phenotypes (group vanA -atypical), which included VanD ( n  = 43) and vancomycin-variable phenotypes ( n  = 5). A multivariable logistic regression indicated that vanA positivity of causative pathogens was independently associated with the increased 30-day mortality rate in the patients with E. faecium BSI; however, there was no significant difference in survival rates between the patients of the vanA -VanA and vanA -atypical groups (log rank test, P =  0.904). A high 30-day mortality rate was observed in patients with vanA -positive E. faecium BSIs, and vanA positivity of causative E. faecium isolates was an independent risk factor for early mortality irrespective of the susceptibility phenotypes to glycopeptides; thus, intensified antimicrobial stewardship is needed to improve the clinical outcomes of patients with vanA -positive E. faecium BSI., (Copyright © 2020 American Society for Microbiology.)

Blastocystis has recently been recognized as the most common eukaryotic microbe of the human gut. We investigated the prevalence of Blastocystis and their subtypes in diarrheal and non-diarrheal groups and the associated clinical parameters. A total of 324 stool samples were obtained from 196 diarrheal and 128 non-diarrheal subjects. Blastocystis subtypes were determined by sequencing the small subunit ribosomal DNA (SSU rRNA) gene. Demographic, clinical and laboratory data were collected and analyzed by diarrhea and Blastocystis status. The overall rate of Blastocystis positivity was 9.0% (29/324) but was significantly higher in the non-diarrheal group (18.0% vs. 3.1%, P&lt;0.0001). Of the 6 Blastocystis-positive diarrheal patients, 3 (50.0%), none (0.0%), 2 (33.3%), and 1 (16.7%) were infected with subtypes ST1, ST2, ST3, and multiple subtypes, respectively. Of the 23 Blastocystis-positive non-diarrheal patients, 4 (17.4%), 1 (4.3%), and 18 (78.3%) were infected with subtypes ST1, ST2, and ST3, respectively. Blastocystis was less common in the diarrheal than the non-diarrheal group (odds ratio, 0.144; 95% confidence interval, 0.057-0.365, P&lt;0.001). Of the 3 subtypes, ST3 was more frequently observed in the non-diarrheal than diarrheal group (78.3% vs. 33.3%, P=0.0341). Collectively, Blastocystis was found in both the diarrheal and non-diarrheal groups and ST3 was the most common subtype in Korea.

Competing Interests: No potential conflicts of interest relevant to this article were reported.

The molecular epidemiology and antimicrobial resistance of Clostridioides difficile were studied in South Korea in 2017 as part of a National Surveillance System. From February to May 2017, all non-duplicate isolates of C. difficile were recovered from patients who were suspected to have C. difficile infection and collected from 6 referral hospitals representing the 6 regions in South Korea. We performed PCRs for the toxin gene, PCR ribotyping, multilocus sequence typing (MLST), antimicrobial susceptibility testing by agar dilution according to the recommendations of the CLSI and detection of antimicrobial resistance genes such as ermB, catD, tetM, vanZ and nimR by PCR. Of 331 C. difficile isolates, 257 (77.6%) were toxigenic and the prevalence of strains producing binary toxin (CDT) was 5.1% (13/257). A total of 52 different ribotype (RT) patterns were found. RT018 was the most common (25.1% of all isolates), and RT014/020, RT002 and RT012 were also common. RT010 was most common non-toxigenic strain. MLST analysis of randomly selected 72 C. difficile isolates identified 46 sequence types (STs), of which three were new and not in the PubMLST library. There was a good correlation between MLST and RT as following: ST1 (RT027), ST8 (RT002), ST11 (RT078), ST17 (RT018), ST35 (RT046), ST37 (RT017), ST42 (RT106), ST53 (RT103), ST81 (RT369), and ST99 (RT070). All toxigenic isolates were susceptible to metronidazole and vancomycin (MIC ≤ 2 mg/L). For rifaximin, 24% of toxigenic isolates were resistant. Of randomly selected 106 toxigenic isolates, resistance rates for ampicillin, cefotetan, clindamycin, imipenem, chloramphenicol, tetracycline, and moxifloxacin were 48%, 46%, 64%, 54%, 0%, 6% and 52% respectively and frequencies of various resistance genes were 62.3% for ermB, 0.9% catD and 10.4% tetM. RTs018, 002, 017 and 369 showed high MICs to various antimicrobial agents and multi-drug resistance was common also., (Copyright © 2019. Published by Elsevier Ltd.)

Background: Although it is essential to know the particular causes of antibiotic-resistant infections in the community, there is lack of evidence regarding risk factors for community-onset extended-spectrum β-lactamase-producing Klebsiella pneumoniae (ESBL-KP) bacteraemia in South Korea. As such, this study aimed to identify risk factors for community-onset ESBL-KP bacteraemia., Methods: From May 2016 to April 2017, patients with community-onset KP bloodstream infection (BSI) (n = 408) from six sentinel hospitals participating in the Global Antimicrobial Surveillance System in South Korea were included in this study. Risk factors of ESBL-KP BSI were assessed. Polymerase chain reaction and sequencing to identify genes encoding ESBLs and multi-locus sequence typing were performed., Results: Of the 408 patients with community-onset KP BSI, 70 (17%) had ESBL-KP BSI. Admission to a long-term-care hospital within the previous 3 months [odds ratio (OR) 5.7, 95% confidence interval (CI) 2.1-15.6; P = 0.001], previous use of trimethoprim/sulfamethoxazole (TMP/SMT; OR 11.5, 95% CI 2.7-48.6; P = 0.001) or extended-spectrum cephalosporin (OR 2.2, 95% CI 1.2-3.9; P = 0.01), and previous use of a urinary catheter (OR 2.3, 95% CI 1.1-4.5; P = 0.02) were independent risk factors for community-onset ESBL-KP BSI. ESBL-KP isolates most frequently carried the CTX-M-1 group ESBL (74%, n = 52). The most prevalent sequence type (ST) among the ESBL-KP isolates was ST48 (14%, n = 10). Among non-ESBL-KP isolates, ST23 was most prevalent (21%, n = 70)., Conclusion: Previous admission to a long-term-care hospital, use of a urinary catheter and use of TMP/SMT or extended-spectrum cephalosporin within the previous 3 months were identified as risk factors for community-onset ESBL-KP BSI. Strict antibiotic stewardship and infection control measures are needed for long-term-care hospitals., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

At the end of 2015, a global action plan on antimicrobial resistance (AMR) was proposed by the World Health Organization, and the Global AMR Surveillance System (GLASS) was subsequently initiated. The Centers for Disease Control and Prevention of South Korea established a customized AMR surveillance system for South Korea, called Kor-GLASS, in early 2016. A pilot phase of Kor-GLASS was operated from May to December 2016 with six sentinel hospitals, and phase I of Kor-GLASS started in January 2017 with eight sentinel hospitals. Previous surveillance data for overestimated AMR due to duplicate isolation of drug-resistant pathogens were corrected and error-free AMR data were compared with those from other countries. One-half (53.2%, 377/708) of Staphylococcus aureus blood strains exhibited resistance to cefoxitin, indicating methicillin-resistant S. aureus. Resistance to ampicillin in Enterococcus faecalis blood strains was rare (0.6%, 1/175), while the resistance rate to penicillin was 26.3% (46/175). Resistance to vancomycin (34.0%, 98/288) and teicoplanin (18.8%, 98/288) was frequently observed in Enterococcus faecium strains. The resistance rate of Escherichia coli strains to cefotaxime was 32.4% (574/1772), and that of Klebsiella pneumoniae strains was 26.1% (181/693). The resistance rates of Pseudomonas aeruginosa strains to imipenem and meropenem were 19.5% (29/149) and 18.1% (27/149), respectively. And 92.1% (187/203) of Acinetobacter baumannii strains were resistant to both imipenem and meropenem. The high incidence of bacteremia caused by major AMR pathogens among hospitalized patients especially in intensive care units emphasized the importance of hospital infection control and the need to improve the crowded hospitalization system in South Korea. The isolation rate of the Salmonella spp. is decreasing, reflecting the current socio-economic status of South Korea. The proportions of bacterial species in the blood strains were similar to those in other Asian countries with similar lifestyles., (Copyright © 2019 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

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., Competing Interests: No potential conflicts of interest relevant to this article were reported., (© The Korean Society for Laboratory Medicine.)

In recent years, the taeniasis has been rarely reported in the Republic of Korea (Korea). But in this study, we intend to report 4 taeniasis cases caused by Taenia saginata during a 5-month period (February to June 2018) at a unversity hospital in Gwangju, Korea. Worm samples (proglottids) discharged from all cases were identified by phenotypic and molecular diagnostics. Mitochondrial cytochrome c oxidase subunit I sequences showed 99.4-99.9% identity with T. saginata but, differed by 4% from T. asiatica and by 7% from T. multiceps, respectively. We found that tapeworms in 2 cases (Cases 2 and 3) yielded exactly the same sequences between them, which differed from those in Cases 1 and 4, suggesting intra-species variation in tapeworms. These taeniasis cases by T. saginata infection in this study, which occurred within a limited time period and region, suggest the possibility of a mini-outbreak. This study highlights the need for further epidemiological investigation of potentially overlooked cases of T. saginata infection in Korea.

Candida auris is an emerging worldwide fungal pathogen. Over the past 20 years, 61 patient isolates of C. auris (4 blood and 57 ear) have been obtained from 13 hospitals in Korea. Here, we reanalyzed those molecularly identified isolates using two matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) systems, including Biotyper and Vitek MS, followed by antifungal susceptibility testing, sequencing of the ERG11 gene, and genotyping. With a research-use-only (RUO) library, 83.6% and 93.4% of the isolates were correctly identified by Biotyper and Vitek MS, respectively. Using an in vitro diagnostic (IVD) library of Vitek MS, 96.7% of the isolates were correctly identified. Fluconazole-resistant isolates made up 62.3% of the isolates, while echinocandin- or multidrug-resistant isolates were not found. Excellent essential (within two dilutions, 96.7%) and categorical agreements (93.4%) between the Clinical and Laboratory Standards Institute (CLSI) and Vitek 2 (AST-YS07 card) methods were observed for fluconazole. Sequencing ERG11 for all 61 isolates revealed that only 3 fluconazole-resistant isolates showed the Erg11p amino acid substitution K143R. All 61 isolates showed identical multilocus sequence typing (MLST). Pulsed-field gel electrophoresis (PFGE) analyses revealed that both blood and ear isolates had the same or similar patterns. These results show that MALDI-TOF MS and Vitek 2 antifungal susceptibility systems can be reliable diagnostic tools for testing C. auris isolates from Korean hospitals. The Erg11p mutation was seldom found among Korean isolates of C. auris , and multidrug resistance was not found. Both MLST and PFGE analyses suggest that these isolates are genetically similar., (Copyright © 2019 American Society for Microbiology.)

Rationale: Use of Xpert MTB/RIF assay as a substitute for smear microscopy in routine clinical practice remains unexplored in an intermediate-tuberculosis-burden setting., Objectives: To compare the diagnostic performance of Xpert and smear microscopy, based on sampling time and location, correlation of Xpert semiquantitative category with smear grade and time to culture positivity, and compliance of reporting time with defined standard time., Methods: Consecutive sputum samples collected from 2,952 suspected pulmonary tuberculosis patients over a 3-year period were tested by Xpert, smear microscopy, and liquid culture as part of routine diagnostics in South Korea., Measurements and Main Results: Based on the analysis of a single sputum specimen per patient, of 2,952 samples, 263 (8.9%) were culture-confirmed tuberculosis and 265 (9.0%) were nontuberculous mycobacteria. The overall sensitivity and specificity were 74.1% and 97.5% for Xpert versus 38.8% and 96.7% for smear microscopy, respectively (P < 0.0001; P > 0.05). Of 82 smear-positive nontuberculous mycobacteria, 81 (98.8%) were accurately excluded by Xpert. Sampling time and location significantly affected the performance of smear microscopy but not that of Xpert. Xpert semiquantitative category strongly correlated with smear grade (γ Goodman-Kruskal  = 0.982; P < 0.0001) and time to culture positivity (γ Goodman-Kruskal  = -0.962; P < 0.0001). Median reporting time and its compliance rate within 24 hours were 3.1 hours and 96.3% for Xpert versus 19.1 hours and 88.7% for smear microscopy, respectively (P < 0.0001; P < 0.05)., Conclusions: Xpert provides faster, more stable, and superior results compared with smear microscopy, in addition to its strong correlation with smear grade. Xpert might replace smear microscopy as the first-line diagnostic test for pulmonary tuberculosis in routine clinical practice in an intermediate-burden setting.

Background: Clonorchiasis is the common parasitic infection in the general population of the Republic of Korea, however, taeniasis is scarcely reported recently. Here, we describe a case of co-infection with the cestode T. saginata in a patient with subclinical clonorchiasis diagnosed by a combination of diagnostic tools in Korea., Case Presentation: A 56-year-old man visited the hospital having passed proglottids in his stool for the past two months and brought a stool sample with segments to our hospital. He had no abdominal symptoms, such as nausea, vomiting, abdominal pain, diarrhea, or constipation. He used to consume raw beef and fish frequently. We could not find evidence of gravid proglottids which contain fully developed uteri filled with ova or branched uterine structures, within the submitted sample. To identify the tapeworm species, we carried out molecular analyses on the proglottids. The cox1 and ef1a sequences had a 100% match with those of T. saginata and differed from the sequences of the other Taenia species. Upon examination of stool samples fixed by formalin-ether concentration method, no Taenia species ova were observed in 10 slides. Instead, C. sinensis ova were observed, despite the level of IgG specific to C. sinensis being within the normal range. The patient was treated with praziquantel (25 mg/kg, three times a day) for 3 days, and subsequently C. sinensis ova were not found in his stool., Conclusion: Our case indicates that a combination of morphological, serological, and molecular diagnostic tools should be used for the accurate diagnosis of subclinical parasitic infections.

A recent surveillance study in South Korea revealed that 14% (7/50) of Aspergillus flavus clinical isolates had a voriconazole minimum inhibitory concentration of ≥4 μg/ml. Of seven non-wild-type (non-WT) isolates, six ear isolates from four hospitals shared the same microsatellite genotype. None of the non-WT isolates showed cyp51 mutations associated with azole resistance. However, the mean expression levels of efflux pump ( MDR2 , atrF , and mfs1 ) and target ( cyp51A ) genes exhibited significant differences between non-WT and other isolates., (Copyright © 2019 American Society for Microbiology.)

Surveillance plays a pivotal role in overcoming antimicrobial resistance (AMR) in bacterial pathogens, and a variety of surveillance systems have been set up and employed in many countries. In 2015, the World Health Organization launched the Global Antimicrobial Resistance Surveillance System (GLASS) as a part of the global action plan to enhance national and global surveillance and research. The aims of GLASS are to foster development of national surveillance systems and to enable collection, analysis and sharing of standardised, comparable and validated data on AMR between different countries. The South Korean AMR surveillance system, Kor-GLASS, is compatible with the GLASS platform and was established in 2016 and based on the principles of representativeness, specialisation, harmonisation and localisation. In this report, we summarise principles and processes in order to share our experiences with other countries planning to establish a national AMR surveillance system. The pilot operation of Kor-GLASS allowed us to understand the national burden of specific infectious diseases and the status of bacterial AMR. Issues pertaining to high costs and labour-intensive operation were raised during the pilot, and improvements are being made.

The Korean government established an antimicrobial resistance (AMR) surveillance system, compatible with the Global AMR Surveillance System (GLASS): Kor-GLASS. We describe results from the first year of operation of the Kor-GLASS from May 2016 to April 2017, comprising all non-duplicated clinical isolates of major pathogens from blood , urine , faeces and urethral and cervical swabs from six sentinel hospitals. Antimicrobial susceptibility tests were carried out by disk diffusion, Etest, broth microdilution and agar dilution methods. Among 67,803 blood cultures, 3,523 target pathogens were recovered. The predominant bacterial species were Escherichia coli (n = 1,536), Klebsiella pneumoniae (n = 597) and Staphylococcus aureus (n = 584). From 57,477 urine cultures, 6,394 E. coli and 1,097 K. pneumoniae were recovered. Bloodstream infections in inpatients per 10,000 patient-days (10TPD) were highest for cefotaxime-resistant E. coli with 2.1, followed by 1.6 for meticillin-resistant Sta. aureus , 1.1 for imipenem-resistant Acinetobacter baumannii , 0.8 for cefotaxime-resistant K. pneumoniae and 0.4 for vancomycin-resistant Enterococcus faecium . Urinary tract infections in inpatients were 7.7 and 2.1 per 10TPD for cefotaxime-resistant E. coli and K. pneumoniae , respectively. Kor-GLASS generated well-curated surveillance data devoid of collection bias or isolate duplication. A bacterial bank and a database for the collections are under development.

A total of 281 nonduplicated Staphylococcus aureus blood isolates were collected from January to May 2017 from eight hospitals in South Korea to investigate the epidemiological traits of ceftaroline resistance in methicillin-resistant S. aureus (MRSA). Cefoxitin-disk diffusion tests and the mecA gene PCR revealed that 56.6% (159/281) of the S. aureus isolates were MRSA, and most belonged to ST5 (50.3%, 80/281) and ST72 (41.5%, 66/281). Of the MRSA isolates, 44.0% (70/159) were nonsusceptible to ceftaroline (MIC ≥ 2 mg/liter), whereas all of the methicillin-susceptible S. aureus isolates were susceptible to the drug. Eight amino acid substitutions in penicillin-binding protein 2a (PBP2a), including four (L357I, E447K, I563T, and S649A) in the penicillin-binding domain (PBD) and four (N104K, V117I, N146K, and A228V) in the non-PBD (nPBD) of PBP2a, were associated with ceftaroline resistance. The accumulation of substitutions in PBP2a resulted in the elevation of ceftaroline MICs: one substitution at 1 to 2 mg/liter, two or three substitutions at 2 to 4 mg/liter, and five substitutions at 4 or 16 mg/liter. Ceftaroline resistance in MRSA might be the result of clone-specific PBP2a polymorphism, along with substitutions both in PBD and nPBD, and the elevated ceftaroline MICs were associated with the substitution sites and accumulation of substitutions., (Copyright © 2018 American Society for Microbiology.)

We investigated the in vitro antifungal susceptibilities of cryptic Aspergillus species from nine Korean hospitals. Based on the CLSI epidemiological cutoff values, resistance rates to amphotericin B, itraconazole, voriconazole, posaconazole and caspofungin were as follows: A. awamori (34 isolates; all 0%), A. tubingensis (22; 0%, 4.5%, 0%, 0%, and 0%, respectively), A. sydowii (16; 0%, 6.3%, 0%, 0%, and 6.3%), A. lentulus (2; 50%, 0%, 100%, 50%, and 0%), and A. tamarii (2; all 0%). A. calidoustus (one isolate) showed resistance to multiple drugs. Thus, cryptic species identification can be mandatory for clinically important Aspergillus isolates, with their susceptibility data.

We investigated the azole resistance mechanisms and clinical features of fluconazole-nonsusceptible (FNS) isolates of Candida tropicalis recovered from Korean surveillance cultures in comparison with fluconazole-less-susceptible (FLS) isolates. Thirty-five clinical isolates of C. tropicalis, comprising 9 FNS (fluconazole MIC, 4 to 64 μg/ml), 12 FLS (MIC, 1 to 2 μg/ml), and 14 control (MIC, 0.125 to 0.5 μg/ml) isolates, were assessed. CDR1, MDR1, and ERG11 expression was quantified, and the ERG11 and UPC2 genes were sequenced. Clinical features of 16 patients with FNS or FLS bloodstream isolates were analyzed. Both FNS and FLS isolates had >10-fold higher mean expression levels of CDR1, MDR1, and ERG11 genes than control isolates (P values of <0.02 for all). When FNS and FLS isolates were compared, FNS isolates had 3.4-fold higher mean ERG11 expression levels than FLS isolates (P = 0.004), but there were no differences in those of CDR1 or MDR1 Of all 35 isolates, 4 (2 FNS and 2 FLS) and 28 (8 FNS, 11 FLS, and 9 control) isolates exhibited amino acid substitutions in Erg11p and Upc2p, respectively. Both FNS and FLS bloodstream isolates were associated with azole therapeutic failure (3/4 versus 4/7) or uncleared fungemia (4/6 versus 4/10), but FNS isolates were identified more frequently from patients with previous azole exposure (6/6 versus 3/10; P = 0.011) and immunosuppression (6/6 versus 3/10; P = 0.011). These results reveal that the majority of FNS C. tropicalis isolates show overexpression of CDR1, MDR1, and ERG11 genes, and fungemia develops after azole exposure in patients with immunosuppression., (Copyright © 2016, American Society for Microbiology. All Rights Reserved.)

We applied the new clinical breakpoints (CBPs) of the Clinical and Laboratory Standards Institute (CLSI) to a multicenter study to determine the antifungal susceptibility of bloodstream infection (BSI) isolates of Candida species in Korea, and determined the relationship between the frequency of antifungal-resistant Candida BSI isolates and antifungal use at hospitals. Four hundred and fifty BSI isolates of Candida species were collected over a 1-year period in 2011 from nine hospitals. The susceptibilities of the isolates to four antifungal agents were determined using the CLSI M27 broth microdilution method. By applying the species-specific CBPs, non-susceptibility to fluconazole was found in 16.4% (70/428) of isolates, comprising 2.6% resistant and 13.8% susceptible-dose dependent isolates. However, non-susceptibility to voriconazole, caspofungin, or micafungin was found in 0% (0/370), 0% (0/437), or 0.5% (2/437) of the Candida BSI isolates, respectively. Of the 450 isolates, 72 (16.0%) showed decreased susceptibility to fluconazole [minimum inhibitory concentration (MIC) ≥4 μg/ml]. The total usage of systemic antifungals varied considerably among the hospitals, ranging from 190.0 to 7.7 defined daily dose per 1,000 patient days, and fluconazole was the most commonly prescribed agent (46.3%). By Spearman's correlation analysis, fluconazole usage did not show a significant correlation with the percentage of fluconazole resistant isolates at hospitals. However, fluconazole usage was significantly correlated with the percentage of fluconazole non-susceptible isolates (r = 0.733; P = 0.025) or the percentage of isolates with decreased susceptibility to fluconazole (MIC ≥4 μg/ml) (r = 0.700; P = 0.036) at hospitals. Our work represents the first South Korean multicenter study demonstrating an association between antifungal use and antifungal resistance among BSI isolates of Candida at hospitals using the new CBPs of the CLSI.

Carbapenem-resistant Acinetobacter spp. have been increasingly reported worldwide with the production of OXA-type carbapenemases as the main mechanism of carbapenem resistance. The prevalent bla(OXA) genes are known to vary significantly depending on time and place of isolation. We investigated the prevalence of bla(OXA) genes by PCR in Acinetobacter spp. isolated in Korea. Among a total of 336 isolates collected from Hospital A from 2002 to 2011, the overall proportion of bla(OXA)-23-like, ISAba1-associated bla(OXA-51)-like, and bla(OXA-182) genes were 44.0%, 49.7%, and 5.1%, respectively. The bla(OXA-58)-like gene was detected in only 1 isolate. A drastic increase in Acinetobacter isolates with bla(OXA-23)-like genes and a decrease in isolates harboring ISAba1-associated bla(OXA-51)-like genes have been observed since the mid-2000s. The bla(OXA-23)-like genes were detected in all carbapenem-nonsusceptible isolates collected in 2011 from 9 hospitals. The OXA-182, which belongs to the fifth group of OXA-type carbapenemase, was detected in Acinetobacter baumannii isolates recovered as early as 2002. It is worrisome results that bla(OXA-182)-carrying Acinetobacter nosocomialis has emerged and caused outbreaks of infection., (© 2013.)

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.

We evaluated three commercial colistin susceptibility testing methods using 213 bloodstream Acinetobacter isolates identified by gene sequencing. Compared to the agar dilution reference method, excellent categorical agreements (both 99.1%) were observed using Vitek 2 and Etest, compared to 87.3% (95.7% for Acinetobacter baumannii and 80.7% for non-baumannii Acinetobacter isolates) using MicroScan.

Background: At present, the clinical breakpoints (CBPs) of both fluconazole and voriconazole are available only for 3 common Candida species in the Clinical and Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) methods. Epidemiological cutoff values (ECVs) were recently applied to both methods to detect the emergence of acquired resistance (i.e., non-wild-type isolates) among 5 common Candida species., Methods: We performed a nationwide study to determine the fluconazole and voriconazole susceptibility of Candida bloodstream isolates (BSIs) using both the CLSI and EUCAST methods. A total of 423 BSIs of 5 Candida species were collected from 8 hospitals. The azole susceptibilities were assessed on the basis of the species-specific CBPs and ECVs., Results: Of the 341 BSIs of 3 common Candida species (i.e., C. albicans, C. tropicalis, and C. parapsilosis), 0.3% and 0.9%, 0.0% and 1.5% of isolates were categorized as fluconazole and voriconazole resistant according to the CLSI and EUCAST CBPs, respectively. Of 423 total BSIs, 1.4% and 2.6% had fluconazole minimum inhibitory concentrations (MICs) exceeding the ECVs according to the CLSI and EUCAST, respectively; 1.0% and 2.1% had voriconazole MICs exceeding the ECVs according to the CLSI and EUCAST, respectively. Categorical agreement between the methods using ECVs was 98.3% for fluconazole and 98.3% for voriconazole., Conclusions: The EUCAST and CLSI methods using ECVs provide highly concordant results. Moreover, non-wild-type isolates with possibly acquired azole resistance were rare among the BSIs of 5 common Candida species in Korea.

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.

The study aimed to investigate the prevalence of various serotypes and extended-spectrum β-lactamase-producing features of Salmonella strains and to determine the antimicrobial susceptibility of 256 Salmonella strains other than Salmonella serotype Typhi, which were isolated at 12 university hospitals in Korea. We identified 46 serotypes of Salmonella spp. Serogroup D was the most common (39.5%), followed by B (32.4%), C (22.7%), E (2.7%), A (2.3%), and G (0.4%). The three most common Salmonella serotypes were Enteritidis (36.3%), Typhimurium (16.8%), and Infantis (7.8%). Six strains that belonged to serotype Paratyphi A and nine that belonged to serotype Paratyphi B were also detected. The 256 Salmonella strains had a 38.7% rate of resistance to ampicillin, 23.0% to chloramphenicol, 8.2% to cefotaxime, 8.6% to ceftriaxone, and 6.3% to trimethoprim-sulfamethoxazole. The antimicrobial resistance rates of Salmonella serogroups B and D were higher than those of the other serogroups. Seven isolates carried blaCTX-M: four CTX-M-15, two CTX-M-14, and one CTX-M-3.

The in vitro antifungal susceptibility of 636 Candida bloodstream isolates collected from 15 tertiary hospitals in Korea was determined using the Vitek-2 yeast susceptibility system (bioMérieux, France). Overall susceptibility rates were 98.1%, 95.9%, 99.1%, and 97.3% for amphotericin B, fluconazole, voriconazole, and flucytosine, respectively. The results show that the rates of resistance to 4 antifungal drugs remain low among Candida bloodstream isolates in Korea.

Natural killer T (NKT) cells have been reported to play crucial roles in a variety of diseases, including infectious diseases, autoimmunity, and cancers. Previous studies have reported wide age- and/or sex-related variations in circulating NKT cell levels in healthy subjects, but reported results are discrepant. In this study, the authors examined NKT cell levels in the peripheral blood of healthy Korean subjects and investigated potential relationships between clinical parameters and NKT cells and their subset levels. One hundred and thirty-eight age- and sex-matched healthy subjects were enrolled in this study. NKT cell and NKT subset levels were measured by flow cytometry. Circulating NKT cell levels were found to vary widely (0.01-5.15%) in the study subjects and to be lower in men than in women (P<0.05). Notably, gender-related differences in NKT cell levels were more prominent in elderly subjects (P<0.05). Furthermore, alterations in NKT subset compositions were found in elderly men, in whom the proportion of CD4+ NKT cells was elevated and that of double-negative NKT cells was reduced. Our data suggest that circulating NKT cells and NKT subset levels are affected by age and gender in the Korean population., (Copyright © 2012 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.)

Background: The aim of this study was to investigate the prevalence of plasmid-mediated quinolone resistance (PMQR) and mutations in quinolone resistance-determining regions (QRDRs) of Salmonella and their association with fluoroquinolone susceptibility in Korea., Methods: A total of 284 nonduplicated clinical isolates of Salmonella were collected from various clinical specimens at 12 tertiary-care hospitals in Korea. The qnrA, qnrB, and qnrS genes were detected by multiplex polymerase chain reaction (PCR). The qepA and aac(6')-Ib-cr genes were amplified by PCR. The QRDRs of gyrA, gyrB, parC, and parE were amplified by PCR from the DNA of selected nalidixic acid-resistant and qnr-positive isolates., Results: We detected six qnr-positive Salmonella (four qnrS1 and two qnrB19) and one aac(6')-Ib-cr-positive strain. A mutation in the QRDR of gyrA only (N=46) was the most common, followed by gyrA+parC (N=9), parC (N=7), gyrA+parE (N=3), parC+parE (N=3), gyrA+gyrB (N=2), and parE (N=1). There were seven novel mutations in the QRDR regions of gyrB, parC, and parE. Six of seven PMQR-positive isolates had high-level resistance to nalidixic acid, and all six strains had reduced susceptibility to ciprofloxacin. One qnrS1-positive isolate was resistant to ciprofloxacin, norfloxacin, and nalidixic acid. The resistant rates to nalidixic acid, ciprofloxacin, norfloxacin, and levofloxacin were 49.3%, 1.1%, 0.7%, and 0.4%, respectively., Conclusion: We report the first detection of PMQR in Salmonella isolates from Korea. It is essential to continue surveillance and to watch for the spread of PMQR in Salmonella for public health control.

Purpose: The increasing prevalence of antimicrobial resistant bacteria has become a serious worldwide problem. The aim of this study was to analyze antimicrobial resistance data generated in 2009 by hospitals and commercial laboratories participating in the Korean Nationwide Surveillance of Antimicrobial Resistance program., Materials and Methods: Susceptibility data were collected from 24 hospitals and two commercial laboratories. In the analysis, resistance did not include intermediate susceptibility. Duplicate isolates were excluded from the analysis of hospital isolates, but not from the commercial laboratory isolates., Results: Among the hospital isolates, methicillin-resistant Staphylococcus aureus, penicillin G-nonsusceptible Streptococcus pneumoniae based on meningitis breakpoint, and ampicillin- resistant Enterococcus faecium remained highly prevalent. The proportion of vancomycin-resistant E. faecium gradually increased to 29%. Ceftazidime-resistant Escherichia coli and Klebsiella pneumoniae increased to 17% and 33%, respectively, and fluoroquinolone-resistant K. pneumoniae, Acinetobacter spp. and Pseudomonas aeruginosa increased to 33%, 67% and 39%, respectively. Amikacin-resistant Acinetobacter spp. increased to 48%. Imipenem-resistant Acinetobacter spp. and P. aeruginosa increased to 51% and 26%, respectively. Higher resistance rates were observed in intensive care unit (ICU) isolates than in non-ICU isolates among the isolates from hospitals. Resistance rates were higher in hospital isolates than in clinic isolates among the isolates from commercial laboratories., Conclusion: Among the hospital isolates, ceftazidime-resistant K. pneumoniae and fluoroquinolone- resistant K. pneumoniae, Acinetobacter spp., and P. aeruginosa further increased. The increase in imipenem resistance was slight in P. aeruginosa, but drastic in Acinetobacter spp. The problematic antimicrobial-organism combinations were much more prevalent among ICU isolates.

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.

Emergence of Candida haemulonii and closely related species at five Korean hospitals has been recently described. We examined biofilm formation by these isolates and assessed their genotypic relatedness by pulsed-field gel electrophoresis (PFGE). This study is the first to show that all bloodstream isolates of Candida pseudohaemulonii can form significant biofilms in glucose-containing medium. PFGE of NotI-digested genomic DNA revealed that C. pseudohaemulonii isolates recovered from seven patients in two hospitals shared five patterns, and that 15 isolates of a proposed new species (Candida auris) obtained from patients at three hospitals shared seven patterns, suggesting that some of these isolates may be related to clonal transmission.

Background: The aim of this study was to determine the yearly prevalence and genotype distribution of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae collected over a 3-yr period in Gwangju, Korea., Methods: Clinical isolates of E. coli and K. pneumoniae collected at Chosun University Hospital from September 15, 2005 to September 14, 2008 were evaluated. Antimicrobial susceptibility testing was performed using the Vitek II system (bioMérieux, USA) and agar dilution methods. Screening for ESBL and AmpC β-lactamase genes was performed using PCR amplification of plasmid DNA followed by direct sequencing of the PCR products., Results: The percentage of ESBL-producing isolates was 12.6% (196/1,550) for E. coli and 26.2% (294/1,121) for K. pneumoniae. The ESBL gene sequencing results showed that the most prevalent ESBL types were CTX-M (93.5%) and SHV (12.9%) in E. coli, and SHV (73.2%) and CTX-M (46.3%) in K. pneumoniae. The most common ESBL in E. coli was CTX-M-15-like, followed by CTX-M-14-like, SHV-2a-like, and SHV-12-like. The most prevalent ESBL type in K. pneumoniae was SHV-12, followed by CTX-M-14-like and CTX-M-15-like. Fifty-one percent (21/41) of ESBL-producing K. pneumoniae with ESBL types verified by sequencing also had DHA-1-like AmpC β-lactamases. However, none of the ESBL-producing E. coli was positive in the AmpC β-lactamase PCR analysis., Conclusions: In this study, the most common types of class A ESBLs identified were CTX-M-15-like in E. coli and SHV-12-like in K. pneumoniae.

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.

PCR fingerprinting and multilocus sequence typing were applied to determine the major molecular types of the Cryptococcus neoformans/Cryptococcus gattii species complex in the Republic of Korea. Of the 78 strains isolated from patients diagnosed with cryptococcosis between 1990 and 2008, 96% were C. neoformans serotype A, mating type MATalpha and molecular type VNI. The remaining 4% were C. gattii, serotype B, mating type MATalpha and either molecular type VGIIb or VGIII. Of the 62 strains with known HIV status, only 14 (22.6%) were isolated from HIV-positive patients and belonged to molecular type VNI. Remarkably, 93% of the C. neoformans isolates had identical PCR fingerprint profiles with the VNIc genotype that has been identified recently as the major genotype among C. neoformans strains in China. Most strains (81.8%) of the VNIc genotype were associated with non-HIV patients compared with strains of the non-VNIc genotype (20%) (P=0.009). Unlike the Chinese strains, a majority (60%) of the non-HIV patients infected with strains of the VNIc genotype in the Republic of Korea had serious underlying conditions, with cancer and liver disease being the most common. This study affirms VNIc to be the most prevalent genotype of C. neoformans isolated from non-HIV patients with cryptococcosis.

Multicenter data on in vitro susceptibility of Candida bloodstream isolates to echinocandin antifungal agents is still lacking in South Korea. We performed a prospective multicenter study to determine the species distribution of Candida bloodstream isolates and their susceptibility to five antifungal agents, including caspofungin and micafungin. A total of 639 isolates were collected from 20 tertiary hospitals between September 2006 and August 2007. Antifungal susceptibilities were determined through the use of the CLSI broth microdilution method M27-A3. The overall species distribution was as follows; Candida albicans (38%), Candida parapsilosis (26%), Candia tropicalis (20%), Candida glabrata (11%), and miscellaneous Candida species (5%). Although C. parapsilosis and miscellaneous Candida species were less susceptible to both echinocandins, all 639 isolates were susceptible to both caspofungin and micafungin (MIC,