Background: Neutralization testing to confirm hepatitis B surface antigen (HBsAg) positivity is strongly recommended to avoid false-positive results but was not reimbursed in Korea at that time of the study. This study aimed to investigate the status of neutralization testing for the confirmation of an HBsAg test result in Korea. Methods: The manufacturers of HBsAg qualitative reagents were listed based on the proficiency test report of the Korean Association of External Quality Assessment Service. The supply status of neutralization reagents and their user laboratories were investigated. The laboratories using neutralization reagents were surveyed to determine the number of specimens utilized for HBsAg qualitative testing and subsequent neutralization testing. Their results were categorized according to the HBsAg levels measured in 2022. Results: Seventeen laboratories performed HBsAg neutralization testing using Roche (14 sites) and Abbott (3 sites) reagents. Each laboratory applied a neutralizing agent to some HBsAg-positive samples using different cutoff points based on the instrument’s measurement values. In 14 laboratories using Roche neutralization reagents, 53.6% of the specimens were positive for HBsAg on neutralization test, of which 94.1% had a cutoff index of <10. Conclusions HBsAg neutralization testing is crucial for preventing falsepositive results of HBsAg qualitative tests, especially for specimens with lower measurement values.

Background: This study aimed to evaluate the efficacy of three medical detergents against bacteria and yeast-derived biofilms. Methods: The biofilm removal efficacy of Empower TM (Metrex, USA), Cidezyme TM (Johnson and Johnson Medical Inc, USA), and Matrix mint TM (Whiteley Medical, Australia) were compared to that of chlorine bleach. Biofilms were produced using Staphylococcus aureusRN9120, Escherichia coli ATCC35218, Pseudomonas aeruginosa ATCC27853, Candida albicans ATCC14053, and clinical isolates of Enterococcus faecalis, E. coli, Klebsiella pneumoniae, Candida auris, and Trichosporon asahii. The organisms were suspended in tryptic soy broth (TSB) in 96-well microplates and cultured for 72 hours. They were treated with the detergents, and the residual biofilm mass was quantified using crystal violet staining followed by optical density measurements at 620 nm (OD 620 ). Results: Empower TM and Cidezyme TM significantly reduced the biofilm mass derived from all species by > 50% of OD 620 at 37ºC except those from E. faecalis, T. asahii, and C. auris. Matrix mint TM had no effect on the biofilms under any condition. Conclusion The culture conditions and the species of the biofilm-producing organism influenced the effectiveness of the detergent. Biofilms produced by E. faecalis, C. auris, and T.asahii were resistant to all detergent treatments under all conditions.

Background: The concurrent detection of human cytomegalovirus (CMV) with UL97 and UL54 mutations is crucial for prescribing adequate antiviral treatment when drug-resistant CMV infection is suspected. We investigated the frequency of resistance-conferring mutations among patients with persistent or recurrent CMV infection and further reviewed the subgroup with UL54 mutations without UL97 mutations. Methods: Patients with persistent or recurrent CMV infection after 4 weeks of treatment with ganciclovir or foscarnet were consecutively enrolled between November 2012 and May 2019.The direct sequencing of UL97 and UL54 was performed to detect resistance mutations in CMV. Results: A total of 101 sequencing datasets were obtained from 65 enrolled patients.CMV UL97 and UL54 mutations were detected in 15.4% (10/65) and 9% (6/65) of patients, respectively. The CMV retrieved from two patients (3%) had mutations in both genes. Four patients with CMV UL54 mutations alone had a history of haploidentical peripheral blood stem cell transplantation, and foscarnet was administered for over 4 weeks to these patients; 21.5% of patients had suspected resistant CMV infection with either UL97 or UL54 mutations. Conclusion In this study, CMV UL54 mutations but not UL97 mutations were found in patients subjected to prolonged foscarnet administration for CMV disease.

This study investigated resistance mechanisms and epidemiology of emerging linezolid-nonsusceptible Enterococcus faecalis (LNSEF) in a tertiary care hospital. LNSEF isolated from clinical samples were collected from November 2017 to June 2019. The isolates were investigated for linezolid resistance and the associated molecular mechanisms, including mutations of 23S rRNA domain V and acquisition of the cfr or optrA resistance gene. We used pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing for the molecular typing of the isolates. Among 4,318 E. faecalis isolates, 10 (0.23%) were linezolid-nonsusceptible. All LNSEF isolates were optrA-positive and cfr-negative. Of these isolates, five were sequence type (ST) 476, two ST585, one ST16, one ST16-like, and one ST480. Six LNSEF isolates obtained in the first year clustered to three types in the PFGE analysis: two ST476 isolates of type A, two ST585 isolates of type B, and two ST16 or ST16-like isolates of type C. Seven cases were of community-onset and three were hospital acquired, but total of eight were healthcare-associated including five community-onset. None of the patients had a history of linezolid treatment, and in one patient, we detected linezolid-susceptible E. faecalis one month before LNSEF detection. In conclusion, heterogenous clones of optrA-positive LNSEF emerged in the hospital mainly via community-onset.

A 30-year-old Korean man with myelodysplastic syndrome admitted hospital due to undifferentiated fever and recurrent skin lesions. He received combination therapy with high doses of meropenem, tigecycline and amikacin, yielding carbapenem resistant Klebsiella pneumoniae (CRKP) harboring K. pneumoniae carbapenemase (KPC)-2 from blood cultures on hospital day (HD) 23. Ceftazidime/avibactam was started at HD 37 and CRKP was eradicated from blood cultures after 5 days. However, ceftazidime/avibactam-resistant CRKP carrying KPC-44 emerged after 26 days of ceftazidime/avibactam treatment and then ceftazidime/ avibactam-resistant, carbapenem-susceptible K. pneumoniae carrying KPC-135 was isolated on HD 65. The 3-D homology of KPC protein showed that hot spot changes in the omega loop could be attributed to ceftazidime/avibactam resistance and loss of carbapenem resistance.Whole genome sequencing of serial isolates supported that phenotypic variation was due to clonal evolution than clonal replacement. The treatment regimen was changed from CAZ/AVI to meropenem-based therapy (meropenem 1 g iv q 8 hours and amikacin 600 mg iv per day) starting with HD 72. CAZ/AVI-susceptible CRKP was presented again from blood cultures on HD 84, and the patient expired on HD 85. This is the first Korean report on the acquisition of ceftazidime/avibactam resistance through the emergence of blaKPC variants.

Strongyloides stercoralis is an intestinal nematode that often causes chronic diarrhea and may develop severe complicated form of hyperinfection or disseminated infection in immunocompromised patients. Here, we report a case of recurrent strongyloidiasis presenting with pulmonary and meningeal involvement. A 55-year-old male diagnosed with pancreatic cancer 4 months ago was admitted due to chronic diarrhea, abdominal pain, and weight loss for 2–3 months. He had been treated with albendazole for chronic recurrent strongyloidiasis 13 years ago and again 2 years ago. He developed sepsis of Klebsiella pneumoniae and Escherichia coli on Days 3 and 7, respectively, and then meningitis of E. coli on Day 42. Strongyloidiasis was diagnosed by detection of abundant filariform larvae in sputum specimens on Day 15. He was treated for disseminated strongyloidiasis with albendazole and ivermectin for five weeks until clearance of larvae was confirmed in sputum and stool specimens. Laboratory diagnosis is important to guide appropriate treatment and to prevent chronic and recurrent strongyloidiasis.
Abdominal Pain ; Albendazole ; Clinical Laboratory Techniques ; Diarrhea ; Escherichia coli ; Humans ; Immunocompromised Host ; Ivermectin ; Klebsiella pneumoniae ; Larva ; Male ; Meningitis ; Middle Aged ; Pancreatic Neoplasms ; Sepsis ; Sputum ; Strongyloides stercoralis ; Strongyloidiasis ; Weight Loss