BACKGROUND:Pasteurella multocida is an important zoonotic pathogen that causes soft-tissue infections in humans; however, recent antimicrobial susceptibility data in Korea remain limited. MATERIALS AND METHODS:A total of 70 clinical P. multocida isolates collected at a nationwide commercial laboratory in Korea between November 2022 and July 2025 were analyzed. Antimicrobial susceptibility testing was performed using the disk diffusion method on Mueller-Hinton agar supplemented with 5% sheep blood. Five clinically relevant antimicrobial agents were tested: penicillin, amoxicillin-clavulanic acid (AMC), levofloxacin, tetracycline, and trimethoprim-sulfamethoxazole (TMP-SMX). For isolates classified as penicillin non-susceptible by disk diffusion, minimum inhibitory concentration (MIC) testing was performed using E-test and β-lactamase production was assessed using a phenotypic method. RESULTS:All tested isolates were susceptible to tetracycline and TMP-SMX by disk diffusion. Susceptibility rates by disk diffusion were 97.1% for AMC, 91.4% for levofloxacin, and 85.7% for penicillin. All 10 isolates initially classified as penicillin non-susceptible by disk diffusion were confirmed to be susceptible to penicillin by MIC testing and were β-lactamase negative. The 2 isolates classified as non-susceptible to AMC by disk diffusion were also β-lactamase negative and susceptible to penicillin by MIC testing. CONCLUSION:No β-lactam resistance was identified among the 70 clinical P. multocida isolates analyzed. These findings support current recommendations that β-lactams and other first-line agents remain active against P. multocida isolates in Korea.

Azithromycin-resistant Neisseria gonorrhoeae poses a threat to the efficacy of gonorrhea treatment. We report the whole-genome characterization of two azithromycin-resistant N. gonorrhoeae ST1600 isolates collected in Busan, South Korea, in 2018 and 2019. Both isolates showed moderate azithromycin resistance (minimum inhibitory concentration 32 µg/mL) mediated by the 23S rRNA C2611T mutation in all four alleles and the -35A deletion in the mtrR promoter, while harboring distinct non-mosaic penA alleles without reduced susceptibility to extended-spectrum cephalosporins. Multilocus sequence typing classified both isolates as ST1600, which is related to ST7363. N. gonorrhoeae multi-antigen sequence typing assigned the 2018 isolate to ST16190, whereas the 2019 isolate represented a novel NG-MAST type closely related to ST16190 (differing by a single SNP in porB). Taken together, these data suggest a limited local transmission cluster with short-term persistence and microevolution, rather than widespread sustained clonal dissemination. Continued phenotypic and genomic surveillance is needed to monitor azithromycin resistance in N. gonorrhoeae and inform national treatment strategies.

Background: Bacteroides fragilis is the most clinically important anaerobic bacterium and has shown increasing carbapenem resistance mediated by the cfiA metallo-β-lactamase. Although insertion sequence (IS)-mediated activation of cfiA is a well-recognized mechanism, the contribution of IS-independent genomic mechanisms remains incompletely characterized. This study investigated the phenotypic and genomic mechanisms of cfiA-associated carbapenem resistance in clinical B. fragilis isolates from Korea. Methods: Twenty-six non-duplicate carbapenem-nonsusceptible B. fragilis isolates were collected from three Korean institutions between 2022 and 2023. Antimicrobial susceptibility was tested by disk diffusion and agar dilution methods, and carbapenemase activity was assessed using the anaerobic carbapenem inactivation method (Ana-CIM) and the meropenem double-ended Etest. Whole-genome sequencing was performed to identify resistance determinants, insertion sequences, promoter structures, and multilocus sequence types. Results: Among 26 isolates, 12 (46.2%) were cfiA-positive and 14 (53.8%) were cfiA-negative. High-level resistance (imipenem MIC ≥ 32 mg/L; meropenem MIC ≥ 128 mg/L) was observed in four cfiA-positive isolates carrying activating IS elements (IS1187 or IS942) upstream of cfiA. Notably, three additional highly resistant cfiA-positive isolates lacked upstream IS elements and showed distinct genomic features, including tandem duplication of cfiA2 (SEV23_101), duplicated promoter architecture upstream of cfiA14 (SEV23_15), and high-level resistance associated with cfiA18 (SCL22_40). Ana-CIM yielded positive results only among isolates with meropenem MIC ≥ 128 mg/L, whereas the meropenem double-ended Etest failed to discriminate cfiA-associated carbapenemase activity. Conclusions: These findings indicate that high-level carbapenem resistance in B. fragilis may be associated with several genomic features, including IS-mediated activation, increased cfiA gene dosage, and promoter amplification. Molecular characterization is therefore essential for accurate interpretation of carbapenem resistance in B. fragilis.

Background:The spread of antimicrobial-resistant bacteria has close relationships among humans, animals, and the environment, necessitating the implementation of the "One Health" approach. In previous study, the prevalence and molecular epidemiology of extended-spectrum β-lactamase-producing Escherichia coli (ESBL-EC) were investigated across multiple pig industry sectors in Korea. In this study, animal developmental stages and antimicrobial usage policies on farms were also considered. Methods:A total of 6,288 non-duplicated samples were collected from pig farms, slaughterhouses, and their personnel from three provinces in Korea between 2020 and 2022. Antimicrobial susceptibility and ESBL gene characterization were performed on the samples. Results:Overall, 1,084 ESBL-EC isolates were collected, with positivity detection rates of 24.7%, 23.3%, 12.7%, 3.9%, 17.2% in pigs, workers, the environment, meat, and total samples, respectively. Common ESBL types were blaCTX-M-55 (N=628), blaCTX-M-15 (N=204), and blaCTX-M-14 (N=127). Pig-derived E. coli isolates had antimicrobial resistance (AMR) rates of 80.4%, 47.2%, 32.6%, 36.7%, 43.4%, 62.4%, and 72.1% to ampicillin, piperacillin, cefazoline, ciprofloxacin, cotrimoxazole, chloramphenicol, and tetracycline, respectively. AMR rates were lower in the finishing stage pigs than in the lactating stage pigs and tended to decrease during animal development for most antimicrobials. AMR rates were higher in pig farms with a customary antimicrobial use policy than in those with a low-level antimicrobial use policy. Conclusions:The findings highlight the significance of elucidating AMR networks among humans, animals, and the environment. Prudent antimicrobial usage and continuous AMR monitoring in the pig industry are crucial to safeguard food safety.

Introduction: Klebsiella variicola, a member of Klebsiella pneumoniae complex, has emerged as an opportunistic pathogen for human infection; however, antimicrobial resistance and hypervirulent characteristics of K. variicola have rarely been investigated in South Korea. Methods: We analyzed 76 clinical K. variicola isolates collected from 12 hospitals between September 2022 and October 2023. Bacterial identification was performed by MALDI-TOF MS. Antimicrobial susceptibility was tested by disk diffusion tests. Resistance determinants and virulence traits were investigated, and whole-genome sequencing was performed for hypermucoviscous or carbapenem-resistant K. variicola isolates. Results: Most (89.5%, 68/76) were susceptible to all 18 antimicrobials tested in this study, and 3 isolates harbored blaCTX-M-15. One isolate carried blaKPC-2 on its IncX3 plasmid, which is closely related to carbapenem-resistant K. pneumoniae plasmids. Capsular typing revealed 51 wzi allelic types. Ten isolates showed mucoid phenotype, mainly with KL60 and KL61. Conclusions: This study reveals relatively low resistance rates in K. variicola strains but the presence of multidrug-resistant and hypermucoviscous K. variicola strains. In addition, the evidence of interspecies dissemination of blaKPC-2 highlights the need for continuous genomic surveillance.

Background:An increase of group B Streptococcus (GBS) colonization in pregnant women with a parallel rise in neonatal and infant infections, were observed in Korea. We characterized antimicrobial resistance (AMR) and molecular features of GBS isolates from reproductive-aged women between 1994-2000 and 2017-2022. Methods:We collected 246 GBS isolates, 37 during 1994-2000 and 209 during 2017-2022, from cervical and/or anorectal swabs at three institutions. Antimicrobial susceptibility was tested using the MicroScan MicroSTREP Plus Panel (Beckman Coulter, Brea, CA, USA). Sequence types (STs), clonal complexes (CCs), cps genotypes by serotypes, and AMR genes were identified using whole-genome sequencing on the NovaSeq 6000 system (Illumina, San Diego, CA, USA). Results:During 1994-2000, CC19 was predominant (35.1%, 13/37), whereas during 2017-2022, CC1 became the most common (35.4%, 74/209). cps genotype VIII, previously limited to one ST1 isolate, appeared in 32 ST2 isolates (P =0.037). All isolates remained susceptible to β-lactams and vancomycin. Tetracycline resistance decreased from 97.3% to 60.8% (P <0.001), with tetM prevalence decreasing from 91.7% to 72.4% (P <0.001) and tetO prevalence increasing from 2.8% to 29.9% (P =0.017). Levofloxacin resistance increased from 0% to 23.4% (P =0.001), with 98.0% of resistant isolates carrying both gyrA and parC. The number of resistance profiles increased from six to 16, including 11 newly identified patterns, covering 81.8% of levofloxacin resistant isolates. Conclusions:The acquisition of diverse resistance genes has expanded AMR profiles in colonized GBS, emphasizing the need for sustained nationwide surveillance.

Novel antimicrobial agents are continually developed to address the global threat of multidrug-resistant Neisseria gonorrhoeae. Promising candidates include zoliflodacin and, possibly, solithromycin. We evaluated their in-vitro activities against gonococcal isolates collected in Korea. In total, 250 N. gonorrhoeae isolates obtained across Korea between 2016 and 2018 were used to determine the minimum inhibitory concentrations (MICs) of 10 therapeutic agents using the CLSI agar dilution method. Most isolates (94.8%, 237/250) demonstrated non-susceptibility to penicillin G, tetracycline, and ciprofloxacin, and susceptibility to ceftriaxone and spectinomycin was substantially high. The half-maximal IC (MIC50) and 90% IC (MIC90) values for zoliflodacin were 0.03 and 0.06 μg/mL, respectively; 0.06 and 0.12 μg/mL, respectively, for solithromycin; and 0.03 and 0.12 μg/mL, respectively, for ceftriaxone. Notably, no cross-resistance was observed between zoliflodacin and ciprofloxacin, despite both targeting DNA topoisomerase II enzymes. Zoliflodacin and solithromycin demonstrated significant in-vitro activity against multidrug-resistant N. gonorrhoeae isolates, and zoliflodacin has shown non-inferiority to ceftriaxone/azithromycin dual therapy in a clinical phase 3 trial. Collectively, our findings highlight the potential of zoliflodacin as a novel therapeutic agent for gonococcal infections, particularly in the context of rising multidrug resistance, and highlight the need for continued surveillance and development of alternative antimicrobial strategies.

Bacteroides fragilis is the most common opportunistic anaerobic pathogen. In the absence of appropriate antimicrobial therapy, mortality rates associated with B. fragilis group infections can reach as high as 50%. Therefore, we aimed to elucidate the clinical characteristics and outcomes of B. fragilis infections and the molecular genetic characteristics of B. fragilis isolates. Forty B. fragilis clinical isolates were collected at Hanyang University Hospital between January 2022 and December 2023. Antimicrobial susceptibility was tested using the agar dilution method. Whole-genome sequencing was conducted using the Illumina platform (Illumina, San Diego, CA, USA). Various multilocus sequence types of B. fragilis were identified, including ST149 (N=4), ST11 (N=4), ST1 (N=3), ST21 (N=2), and ST157 (N=1). The insertion sequence (IS) IS1187, located upstream of cfiA, was associated with high-level carbapenem resistance in the ST157 isolate. B. fragilis toxin genes (bft ) were identified in 30% of isolates. The most common comorbidities were diabetes mellitus (26.5%) and non-metastatic cancer (23.5%). Five patients (14.7%) died within 30 days, and two (5.9%) deaths were directly attributable to B. fragilis infection. The emergence of high-level MIC carbapenem-resistant B. fragilis ST157 has led to caution in the presence of B. fragilis infections.

Background:Bacteroides fragilis group (BFG) isolates are the most frequently isolated gram-negative anaerobic bacteria and exhibit higher levels of antimicrobial resistance than other anaerobic bacteria. Reliable susceptibility testing is needed because of reports of resistance to the most active antibiotics. Recently, the European Committee on Antimicrobial Susceptibility Testing (EUCAST) introduced disk zone diameter breakpoints. We evaluated the disk diffusion test (DDT) for susceptibility testing of BFG isolates compared with the agar dilution method. Methods:In total, 150 BFG isolates were collected from three institutes in Korea. The agar dilution method was conducted according to the CLSI guidelines. DDT was performed following the EUCAST guideline. Fastidious anaerobe agar supplemented with 5% defibrinated horse blood was used as the culture medium. Nine antimicrobials were evaluated: penicillin, cefoxitin, cefotetan, imipenem, meropenem, piperacillin-tazobactam, clindamycin, moxifloxacin, and metronidazole. Results:The categorical agreement (CA) between the two methods was >90.0% for imipenem, meropenem, clindamycin, and metronidazole. However, the CA for piperacillintazobactam was low, at 83.2%. Major errors were found: 5.4% for imipenem, 7.4% for meropenem, and 12.8% for piperacillin-tazobactam. All minor errors were <10%. We propose using the area of technical uncertainty (ATU) zone-overlapping area for susceptible and resistant strains to reduce errors in the DDT. Outside the ATU, the CAs of cefoxitin, cefotetan, and piperacillin-tazobactam were >90.0%, whereas that of moxifloxacin was increased to 88.5%. Conclusions:The DDT can be a useful alternative antimicrobial susceptibility test for BFG isolates when using the ATU zone to reduce errors.

Fusobacterium nucleatum (Fn) is increasingly recognized as a cancer-associated bacterium, yet reliable quantification in human specimens is challenging due to low bacterial burden and abundant host DNA. We analyzed 145 Fusobacterium genomes to design primers targeting conserved regions of the fadA adhesin gene and developed a duplex quantitative real-time PCR (qPCR) assay for simultaneous detection of fadA and a human PGT as an internal control. Analytical sensitivity, specificity, precision, and reproducibility were evaluated using serially diluted Fn DNA, spike-in experiments with human DNA, and cross-platform/operator validation. Clinical performance was assessed in colorectal cancer patient tissues, including fresh tissue (n = 24) and formalin-fixed paraffin-embedded (FFPE) samples (n = 22), using 16S rRNA-based methods as references. The assay successfully detected all four major Fn subspecies (nucleatum, animalis, polymorphum, and vincentii). The limit of detection was ≤0.1 pg, with no interference between duplex targets. Spike-in experiments demonstrated consistent target detection in human-DNA-rich samples, with strong linearity (R2 = 0.998) across dilutions. High precision (coefficient of variations < 5%) was observed across intra-day, inter-day, inter-instrument, and inter-operator evaluations. In fresh tissues, the assay yielded 86% sensitivity, 94% specificity, and 92% accuracy. Using the FFPE samples, the assay achieved 91% sensitivity and 100% specificity, confirming robust classification in both clinical samples. This duplex qPCR assay enables broad detection of Fn with high analytical performance in both fresh and FFPE tissues. Its simplicity, reproducibility, and compatibility with pathology workflows support deployment in multi-center studies and downstream applications in diagnostic studies and prognostic modeling.

BACKGROUND/AIM:Although photobiomodulation therapy (PBMt) is available to alleviate post-operative side effects of malignant diseases, its application is still controversial due to some potential of cancer recurrence and occurrence of a secondary malignancy. We investigated effect of PBMt on mitochondrial function in HT29 colon cancer cells. METHODS:HT29 cell proliferation was determined with MTT assay after PBMt. Immunofluorescent staining was performed to determine mitochondrial biogenesis and reactive oxygen species (ROS). Mitochondrial membrane potential was measured with Mitotracker. Western blotting was executed to determine expression of fission, fusion, UCP2, and cyclin B1 and D1 proteins. In vivo study was performed by subcutaneously inoculating cancer cells into nude mice and immunohistochemistry was done to determine expression of FIS1, MFN2, UCP2, and p-AKT. RESULTS:The proliferation and migration of HT29 cells reached maximum with PBMt (670 nm, light emitting diode, LED) at 2.0 J/cm2 compared to control (P < 0.05) with more expression of cyclin B1 and cyclin D1 (P < 0.05). Immunofluorescent staining showed that ROS and mitochondrial membrane potential were enhanced after PBMt compared to control. ATP synthesis of mitochondria was also higher in the PBMt group than in the control (P < 0.05). Expression levels of fission and fusion proteins were significantly increased in the PBMt group than in the control (P < 0.05). Electron microscopy revealed that the percentage of mitochondria showing fission was not significantly different between the two groups. Oncometabolites including D-2-hydoxyglutamate in the supernatant of cell culture were higher in the PBMt group than in the control with increased UCP2 expression (P < 0.05). Both tumor size and weight of xenograft in nude mice model were bigger and heavier in the PBMt group than in the control (P < 0.05). Immunohistologically, mitochondrial biogenesis proteins UCP2 and p-AKT in xenograft of nude mice were expressed more in the PBMt group than in the control (P < 0.05). CONCLUSIONS:Treatment with PBM using red light LED may induce proliferation and progression of HT29 cancer cells by increasing mitochondrial activity and fission.

Background: Pharyngeal infection is more difficult to diagnose and treat than genital or rectal infection and can act as a reservoir for gonococcal infection. We determined the prevalence of pharyngeal gonorrhea in Korean men with urethritis and analyzed the molecular characteristics and antimicrobial susceptibility of the isolates. Methods: Seventy-two male patients with symptoms of urethritis who visited a urology clinic in Wonju, Korea, between September 2016 and March 2018 were included. Urethral and pharyngeal gonococcal cultures, antimicrobial susceptibility testing, Neisseria gonorrhoeae multi-antigen sequence typing (NG-MAST), and multiplex real-time PCR (mRT-PCR) were performed. Results: Among the 72 patients, 59 tested positive for gonococcus by mRT-PCR. Of these 59 patients, 18 (30.5%) tested positive in both the pharynx and urethra, whereas 41 tested positive only in the urethra. NG-MAST was feasible in 16 out of 18 patients and revealed that 14 patients had the same sequence types in both urethral and pharyngeal specimens, whereas two patients exhibited different sequence types between the urethra and pharynx. Of the 72 patients, 33 tested culture-positive. All patients tested positive only in urethral specimens, except for one patient who tested positive in both. All culture-positive specimens also tested positive by mRT-PCR. All isolates were susceptible to azithromycin and spectinomycin, but resistance rates to ceftriaxone and cefixime were 2.9% and Conclusions: The prevalence of pharyngeal gonorrhea in Korean men with gonococcal urethritis is as high as 30.5%, highlighting the need for pharyngeal screening in high-risk groups. Ceftriaxone is the recommended treatment for pharyngeal gonorrhea.

ABSTRACT Urinary tract infections (UTIs) are pervasive and prevalent in both community and hospital settings. Recent trends in the changes of the causative microorganisms in these infections could affect the effectiveness of urinalysis (UA). We aimed to evaluate the predictive performance of UA for urinary culture test results according to the causative microorganisms. In addition, UA results were integrated with artificial intelligence (AI) methods to improve the predictive power. A total of 360,376 suspected UTI patients were enrolled from two university hospitals and one commercial laboratory. To ensure broad model applicability, only a limited range of clinical data available from commercial laboratories was used in the analyses. Overall, 53,408 (14.8%) patients were identified as having a positive urine culture. Among the UA tests, the combination of leukocyte esterase and nitrite tests showed the highest area under the curve (AUROC, 0.766; 95% CI, 0.764–0.768) for predicting urine culture positivity but performed poorly for Gram-positive bacteriuria (0.642; 0.637–0.647). The application of an AI model improved the predictive power of the model for urine culture results to an AUROC of 0.872 (0.870–0.875), and the model showed superior performance metrics not only for Gram-negative bacteriuria (0.901; 0.899–0.902) but also for Gram-positive bacteriuria (0.745; 0.740–0.749) and funguria (0.872; 0.865–0.879). As the prevalence of non- Escherichia coli -caused UTIs increases, the performance of UA in predicting UTIs could be compromised. The addition of AI technologies has shown potential for improving the predictive performance of UA for urine culture results. IMPORTANCE UA had good performance in predicting urine culture results caused by Gram-negative bacteria, especially for Escherichia coli and Pseudomonas aeruginosa bacteriuria, but had limitations in predicting urine culture results caused by Gram-positive bacteria, including Streptococcus agalactiae and Enterococcus faecalis . We developed and externally validated an AI model incorporating minimal demographic information of patients (age and sex) and laboratory data for UA, complete blood count, and serum creatinine concentrations. The AI model exhibited improved performance in predicting urine culture results across all the causative microorganisms, including Gram-positive bacteria, Gram-negative bacteria, and fungi.

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Background: Numerous studies have examined the prevalence of Helicobacter pylori infection and clarithromycin (CLA) resistance rate of H. pylori. However, in South Korea, there is a lack of research analyzing specimens from local clinics and hospitals using molecular methods. This study aimed to assess the prevalence of H. pylori infection and CLA resistance across sex and age groups, as well as to explore regional variations in CLA resistance and its characteristics. Methods: Data from a laboratory information system from 2015 to 2018 were retrospectively analyzed to determine the prevalence of H. pylori infection and CLA resistance rate. The 23S ribosomal RNA genes of H. pylori were analyzed using a dual priming oligonucleotide-based multiplex polymerase chain reaction method. Results: The overall prevalence of H. pylori infection was 50.5%(12,000/23,773), with a significantly higher prevalence among males (53.5%) than females (47.0%). The CLA resistance rate was 28.3%, with a significantly higher rate among females (34.9%) than males (23.8%). Age group analysis revealed that the highest prevalence of H. pylori infection was among individuals in their 40s, whereas the highest CLA resistance rate was observed among those in their 60s. The CLA resistance rate exhibited an upward trend and varied among patients based on their place of residence, and A2143G mutation was the most prevalent across all regions. Conclusion: The prevalence of H. pylori infection and CLA resistance rate in Korea remain high and vary according to sex, age, and region. To effectively eradicate H. pylori, it is crucial to periodically monitor regional CLA resistance patterns and conduct CLA susceptibility testing before prescription.

Wastewater-based epidemiology has been used in pathogen surveillance for microorganisms at the community level. This study was conducted to determine the occurrence and trends of infectious pathogens in sewage from Yongin city and the relationships between these pathogens and the incidence of infectious diseases in the community. From December 2022 to November 2023, we collected inflow water from six wastewater treatment plants in Yongin city twice a month. The analyzed microorganisms included 15 respiratory viruses, 7 pneumonia-causing bacteria, 19 acute diarrhea-causing pathogens, SARS-CoV-2, Zika virus, hepatitis A virus, poliovirus, Mpox, and measles. They were detected through real-time PCR and conventional PCR. The concentrations of 9 pathogens among them were additionally analyzed using quantitative real time PCR. The correlation was confirmed through statistical analysis with the rate of detection for pathogens reported by the Korea Disease Control and Prevention Agency. Influenza A virus, human adenovirus, and human rhinovirus were moderately correlated (rho values of 0.45 to 0.58). Campylobacter spp. and sapovirus were strong correlated (rho values of 0.62, 0.63). Enteropathogenic E. coli, human coronavirus, and norovirus GII were very strong correlated (rho values of 0.86 to 0.92). We were able to identify the prevalence of respiratory viral infections, pneumonia, and acute diarrhea-causing pathogens in the community through wastewater-based epidemiology data. This study will be helpful in establishing a system for future surveillance of infectious diseases present in sewage.

Pasteurella spp. can cause fatal zoonotic infections in humans. We performed a multicenter study to investigate the prevalence and clinical features of Pasteurella infections in South Korea during 2018-2022. We also conducted a collaborative systematic review and meta- analysis of the global burden of Pasteurella bacteremia. The study included 283 cases and found an increasing trend in Pasteurella infections. Blood cultures were positive in 8/35 (22.9%) cases sampled, for an overall bacteremia-associated rate of 2.8% (8/283). Aging was a significant risk factor for bacteremia (odds ratio 1.05 [95% CI1.01-1.10]), according to multivariate analyses. For the meta-analysis, we included a total of 2,012 cases from 10 studies. The pooled prevalence of bacteremia was 12.4% (95% CI 7.3%-18.6%) and of mortality 8.4% (95% CI 2.7%-16.5%). Our findings reflect the need for greater understanding of the increase in Pasteurella infections and the global burden of Pasteurella bacteremia to determine appropriate case management.

Background: The incidence of early-and late-onset sepsis and meningitis in neonates due to maternal rectovaginal group B Streptococcus (GBS) colonization may differ with serotype distribution and clonal complex (CC).CC17 strains are associated with hypervirulence and poor disease outcomes.GBS serotypes are distinguished based on the polysaccharide capsule, the most important virulence factor.We determined the sequence type distribution of GBS isolates from pregnant women in Korea and validated whole-genome sequencing (WGS)-based prediction of antimicrobial susceptibility and capsular serotypes in GBS isolates.Methods: Seventy-five GBS isolates collected from pregnant Korean women visiting Wonju Severance Christian Hospital, Wonju, Korea between 2017 and 2019 were subjected to WGS using the NovaSeq 6000 system (Illumina, San Diego, CA, USA).Multilocus sequence types, serotypes, antimicrobial resistance genes, and hemolysin operon mutations were determined by WGS, and the latter three were compared with the results of conventional phenotypic methods. Results:The predominant lineage was CC1 (37.3%), followed by CC19 (32.0%),CC12 (17.3%), and CC17 (4.0%).All isolates were cps typeable (100%, (75/75), and 89.3% of cps genotypes (67/75) were concordant with serotypes obtained using latex agglutination.The cps genotypes of the 75 isolates were serotypes III (24.0%),V (22.7%), and VIII (17.3%).All isolates harboring intact ermB and tet were non-susceptible to erythromycin and tetracycline, respectively.Three non-hemolytic strains had 1-bp frameshift insertions in cylE. Conclusions:The low prevalence of CC17 GBS colonization may explain the low frequency of neonatal GBS infections.WGS is a useful tool for simultaneous genotyping and antimicrobial resistance determination.