Impact of linkage level on inferences from big data analyses in health and medical research: an empirical study.

BACKGROUND: Linkage errors that occur according to linkage levels can adversely affect the accuracy and reliability of analysis results. This study aimed to identify the differences in results according to personally identifiable information linkage level, sample size, and analysis methods through empirical analysis. METHODS: The difference between the results of linkage in directly identifiable information (DII) and indirectly identifiable information (III) linkage levels was set as III linkage based on name, date of birth, and sex and DII linkage based on resident registration number. The datasets linked at each level were named as databaseIII (DBIII) and databaseDII (DBDII), respectively. Considering the analysis results of the DII-linked dataset as the gold standard, descriptive statistics, group comparison, incidence estimation, treatment effect, and moderation effect analysis results were assessed. RESULTS: The linkage rates for DBDII and DBIII were 71.1% and 99.7%, respectively. Regarding descriptive statistics and group comparison analysis, the difference in effect in most cases was "none" to "very little." With respect to cervical cancer that had a relatively small sample size, analysis of DBIII resulted in an underestimation of the incidence in the control group and an overestimation of the incidence in the treatment group (hazard ratio [HR] = 2.62 [95% confidence interval (CI): 1.63-4.23] in DBIII vs. 1.80 [95% CI: 1.18-2.73] in DBDII). Regarding prostate cancer, there was a conflicting tendency with the treatment effect being over or underestimated according to the surveillance, epidemiology, and end results summary staging (HR = 2.27 [95% CI: 1.91-2.70] in DBIII vs. 1.92 [95% CI: 1.70-2.17] in DBDII for the localized stage; HR = 1.80 [95% CI: 1.37-2.36] in DBIII vs. 2.05 [95% CI: 1.67-2.52] in DBDII for the regional stage). CONCLUSIONS: To prevent distortion of the analyses results in health and medical research, it is important to check that the patient population and sample size by each factor of interest (FOI) are sufficient when different data are linked using DBDII. In cases involving a rare disease or with a small sample size for FOI, there is a high likelihood that a DII linkage is unavoidable.

Evolution of blaKPC Under the Pressure of Carbapenems and Ceftazidime/Avibactam in a Patient With Persistent Bacteremia Caused by Klebsiella pneumoniae.

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.

Clinical and microbiological characteristics of persistent Staphylococcus aureus bacteremia, risk factors for mortality, and the role of CD4+ T cells.

This study evaluated the determinants of mortality and the T cell immune response in patients with persistent Staphylococcus aureus bacteremia (SAB). This was a prospective cohort study and patients with confirmed SAB were enrolled from 2008 to 2020. We compared clinical, microbiological, and genotypic features between surviving and deceased patients with persistent SAB. The concentrations of cytokines and the proportions of IFN-γ secreting CD4+ T cells were measured serially during the bacteremia period. Of the 1760 patients, 242 had persistent bacteremia (PB), and 49 PB patients died within 30 days. In the multivariate analysis, the APACHE II score and female sex were independently associated with 30 days mortality. The level of IL-10 was significantly increased in the plasma of patients with a high Pitt bacteremia score and those who died within 12 weeks from the index day. The proportion of IFN-γ-secreting CD4+ T cells were the highest just before the positive-to-negative conversion of blood cultures in patients with a low Pitt bacteremia score and those who survived for 12 weeks. The level of IL-10 is correlated with clinical outcomes in PB patients. IFN-γ secreting CD4+ T cells might play a pivotal role in SAB PB.

Effectiveness of ceiling-mounted ultraviolet-C lamps: an experimental study in a biocontainment unit of a tertiary care hospital.

BACKGROUND: The mounted UV-C lamp requires no separate space or labor for transport, but data on its effectiveness for surface disinfection are scarce. We aimed to evaluate the performance of ceiling-mounted UV-C lamps. METHODS: This study was conducted in an empty room with UV-C lamps in the biocontainment unit of a tertiary care hospital in South Korea. UV-C lamps were installed on the ceiling of the patient room, anteroom, and toilet. Each pathogen (Staphylococcus aureus, Escherichia coli, Candida krusei, Bacillus cereus, and Mycobacterium peregrinum) was inoculated on blood agar plates and placed in 20 selected places from the UV-C lamp, and irradiation was applied for 15 min. As a control group, the bacterial solution was diluted 10,000 times and UV was not applied. RESULTS: A mean ± SD of 5.95 ± 0.91 log reduction was observed with UV irradiation compared with the control. The log reduction was greatest for S. aureus [median, 7.05 (IQR, 6.49-7.26)] and least for M. peregrinum [median, 4.88 (IQR, 4.58-5.24)]. The degree of log reduction was inversely proportional to the square of the distance from the UV-C lamp (R2 = -0.12, p < 0.001). CONCLUSIONS: In this study, ceiling-mounted UV-C demonstrated effective disinfection of at least 4-log reduction of the test organisms within a 4-m distance. Mounted UV-C lighting is a considerable option for improving surface disinfection.

Risk factors for vancomycin treatment failure in heterogeneous vancomycin-intermediate Staphylococcus aureus bacteremia.

The incidence of heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) infection is increasing and is associated with vancomycin treatment failures. However, studies investigating the risk factors for treatment failure in hVISA infection are limited. Patients with hVISA bacteremia treated with vancomycin over 7 days between August 2008 and June 2020 were enrolled in this study. Clinical and microbiological characteristics were compared between vancomycin treatment failure and success groups to identify the risk factors for vancomycin treatment failure. Among the 180 patients with hVISA bacteremia, 102 patients treated with vancomycin over 7 days were included. Vancomycin treatment failed in 80 (78%) patients. Patients in the vancomycin treatment failure group were older (P < 0.001) and more frequently had solid cancer (P = 0.04) than those in the vancomycin treatment success group. Solid organ transplantation (SOT) was more frequent (P < 0.001) in the vancomycin treatment success group. The Charlson comorbidity index (P = 0.01) and Acute Physiology and Chronic Health Evaluation II scores (P < 0.001) were higher in the vancomycin treatment failure group. In multivariate analysis, independent risk factors for vancomycin treatment failure were old age and severity of bacteremia. SOT and vancomycin minimal inhibitory concentration (MIC) ≤ 1.0 mg/L using the broth microdilution (BMD) method were associated with successful vancomycin treatment. Old age and infection severity were independent risk factors for vancomycin treatment failure. Vancomycin MIC using the BMD method is an important risk factor for vancomycin treatment failure, and its use should be considered in hVISA bacteremia.IMPORTANCEIn this study, we assessed the clinical and microbiological characteristics of heterogeneous vancomycin-intermediated Staphylococcus aureus (hVISA) bacteremia and identified risk factors for vancomycin treatment failure. We found that advanced age and severity of infection were independent risk factors for vancomycin treatment failure. On the other hand, solid organ transplantation and a low vancomycin minimal inhibitory concentration were associated with successful vancomycin treatment. This study highlights the importance of vancomycin minimal inhibitory concentration in hVISA bacteremia.

Persistent differences in the immunogenicity of the two COVID-19 primary vaccines series, modulated by booster mRNA vaccination and breakthrough infection.

INTRODUCTION: The long-term impact of initial immunogenicity induced by different primary COVID-19 vaccine series remains unclear. METHODS: A prospective cohort study was conducted at 10 tertiary hospitals in Korea from March 2021 to September 2022. Immunogenicity assessments included anti-spike protein antibody (Sab), SARS-CoV-2-specific interferon-gamma releasing assay (IGRA), and multiplex cytokine assays for spike protein-stimulated plasma. Spike proteins derived from wild-type SARS-CoV-2 and alpha variant (Spike1) and beta and gamma variant (Spike2) were utilized. RESULTS: A total of 235 healthcare workers who had received a two-dose primary vaccine series of either ChAdOx1 or BNT162b2, followed by a third booster dose of BNT162b2 (166 in the ChAdOx1/ChAdOx1/BNT162b2 (CCB) group and 69 in the BNT162b2/BNT162b2/BNT162b2 (BBB) group, based on the vaccine series) were included. Following the primary vaccine series, the BBB group exhibited significantly higher increases in Sab levels, IGRA responses, and multiple cytokines (CCL2/MCP-1, CCL3/MIP-1α, CCL4/MIP-1ß, interleukin (IL)-1ra, IFN-γ, IL-2, IL-4, and IL-10) compared to the CCB group (all P < 0.05). One month after the third BNT162b2 booster, the CCB group showed Sab levels comparable to those of the BBB group, and both groups exhibited lower levels after six months without breakthrough infections (BIs). However, among those who experienced BA.1/2 BIs after the third booster, Sab levels increased significantly more in the BBB group than in the CCB group (P < 0.001). IGRA responses to both Spike1 and Spike2 proteins were significantly stronger in the BBB group than the CCB group after the third booster, while only the Spike2 response were higher after BIs (P = 0.007). The BBB group exhibited stronger enhancement of T-cell cytokines (IL-2, IL-4, and IL-17A) after BIs than in the CCB group (P < 0.05). CONCLUSION: Differences in immunogenicity induced by the two primary vaccine series persisted, modulated by subsequent booster vaccinations and BIs.

Severe Human Parainfluenza Virus Community- and Healthcare-Acquired Pneumonia in Adults at Tertiary Hospital, Seoul, South Korea, 2010-2019.

The characteristics of severe human parainfluenza virus (HPIV)-associated pneumonia in adults have not been well evaluated. We investigated epidemiologic and clinical characteristics of 143 patients with severe HPIV-associated pneumonia during 2010-2019. HPIV was the most common cause (25.2%) of severe virus-associated hospital-acquired pneumonia and the third most common cause (15.7%) of severe virus-associated community-acquired pneumonia. Hematologic malignancy (35.0%), diabetes mellitus (23.8%), and structural lung disease (21.0%) were common underlying conditions. Co-infections occurred in 54.5% of patients admitted to an intensive care unit. The 90-day mortality rate for HPIV-associated pneumonia was comparable to that for severe influenza virus-associated pneumonia (55.2% vs. 48.4%; p = 0.22). Ribavirin treatment was not associated with lower mortality rates. Fungal co-infections were associated with 82.4% of deaths. Clinicians should consider the possibility of pathogenic co-infections in patients with HPIV-associated pneumonia. Contact precautions and environmental cleaning are crucial to prevent HPIV transmission in hospital settings.

Quantitative interferon-gamma releasing assay in predicting tuberculosis in South Korean military: a retrospective cohort study.

OBJECTIVE: The interferon-gamma releasing assay (IGRA) has been widely used to diagnose latent tuberculosis infection (TBI). However, there are limited data on the association between performance in the IGRA and risk of tuberculosis disease (TBD), as well as on the appropriate IGRA threshold for initiating TBI treatment. METHODS: The analysis was performed using the IGRA results in the Korean Military Manpower Administration database (January 2017 to December 2021), and TBD cases reported to the Korean Military Medical Command (January 2017 to June 2023). All Korean candidates for 18-month military service underwent the IGRA in the pre-enlistment examination, and enlistees who tested positive (≥0.35 IU/mL) were advised to receive TBI treatment before enlistment. RESULTS: From 2017 to 2021, 1 647 941 individuals were screened, with 29 574 testing positive for IGRA. Excluding nonenlistees namely individuals with TBD before enlistment, 19 387 individuals were IGRA positive and 1 356 324 IGRA negative. Of the positives, 4351 were excluded due to discontinued or ongoing TBI treatment at or after enlistment. During follow-up of 9219 untreated and 5818 treated positive individuals and 1 356 324 negatives, TBD occurred in 22 of the IGRA-positive individuals (97.5/100 000 person-years [95% CI, 61.1-147.7]), predominantly in the untreated group (18 cases, 130.1/100 000 person-years [95% CI, 77.1-205.7]) compared to the treated group (4 cases, 45.9/100 000 person-years [95% CI 12.5 - 117.4]), whereas 57 cases occurred in the IGRA-negative group (2.8/100 000 person-years [95% CI, 2.2-3.6]). Elevating the cutoff of IGRA from 0.35 IU/mL to 1.33 IU/mL increased positive predictive value (0.2% vs. 0.4%, p 0.03), with insignificant loss of sensitivity (24% vs. 20%, p 0.69) and decreased numbers needing treatment from 790.5 to 415.3. DISCUSSION: Elevated IGRA levels before enlistment are associated with risk of TBD during military service. It is worth considering raising the IGRA threshold for treatment of TBI in cohorts of healthy, young military individuals.

Comparison of the Clinical Outcomes Between Early and Delayed Transplantation After SARS-CoV-2 Infection.

Our study analyzed 95 solid organ transplant (SOT) and 78 hematopoietic stem cell transplant (HSCT) recipients with prior coronavirus disease 2019 (COVID-19). Patients who underwent transplantation within 30 days of COVID-19 infection comprised the early group, and those who underwent transplantation post-30 days of COVID-19 infection comprised the delayed group. In the early transplantation group, no patient, whether undergoing SOT and HSCT, experienced COVID-19-associated complications. In the delayed transplantation group, one patient each from SOT and HSCT experienced COVID-19-associated complications. Additionally, among early SOT and HSCT recipients, two and six patients underwent transplantation within seven days of COVID-19 diagnosis, respectively. However, no significant differences were observed in the clinical outcomes of these patients compared to those in other patients. Early transplantation following severe acute respiratory syndrome coronavirus 2 infection can be performed without increased risk of COVID-19-associated complications. Therefore, transplantation needs not be delayed by COVID-19 infection.

PPIB/Cyclophilin B expression associates with tumor progression and unfavorable survival in patients with pulmonary adenocarcinoma.

Cyclophilin B (CypB), encoded by peptidylprolyl isomerase B (PPIB), is involved in cellular transcriptional regulation, immune responses, chemotaxis, and proliferation. Recent studies have shown that PPIB/CypB is associated with tumor progression and chemoresistance in various cancers. However, the clinicopathologic significance and mechanism of action of PPIB/CypB in non-small cell lung cancer (NSCLC) remain unclear. In this study, we used RNA in situ hybridization to examine PPIB expression in 431 NSCLC tissue microarrays consisting of 295 adenocarcinomas (ADCs) and 136 squamous cell carcinomas (SCCs). Additionally, Ki-67 expression was evaluated using immunohistochemistry. The role of PPIB/CypB was assessed in five human NSCLC cell lines. There was a significant correlation between PPIB/CypB expression and Ki-67 expression in ADC (Spearman correlation r=0.374, P<0.001) and a weak correlation in SCC (r=0.229, P=0.007). In ADCs, high PPIB expression (PPIBhigh) was associated with lymph node metastasis (P=0.023), advanced disease stage (P=0.014), disease recurrence (P=0.013), and patient mortality (P=0.015). Meanwhile, high Ki-67 expression (Ki-67high) was correlated with male sex, smoking history, high pT stage, lymph node metastasis, advanced stage, disease recurrence, and patient mortality in ADC (all P<0.001). However, there was no association between either marker or clinicopathological factors, except for old age and PPIBhigh (P=0.038) in SCC. Survival analyses revealed that the combined expression of PPIBhigh/Ki-67high was an independent prognosis factor for poor disease-free survival (HR 1.424, 95% CI 1.177-1.723, P<0.001) and overall survival (HR 1.266, 95% CI 1.036-1.548, P=0.021) in ADC, but not in SCC. Furthermore, PPIB/CypB promoted the proliferation, colony formation, and migration of NSCLC cells. We also observed the oncogenic properties of PPIB/CypB expression in human bronchial epithelial cells. In conclusion, PPIB/CypB contributes to tumor growth in NSCLC, and elevated PPIB/Ki-67 levels are linked to unfavorable survival, especially in ADC.

Multiomics profiling of urothelial carcinoma in situ reveals CIS-specific gene signature and immune characteristics.

Urothelial carcinoma in situ (CIS) is an aggressive phenotype of non-muscle-invasive bladder cancer. Molecular features unique to CIS compared to high-grade papillary tumors are underexplored. RNA sequencing of CIS, papillary tumors, and normal urothelium showed lower immune marker expression in CIS compared to papillary tumors. We identified a 46-gene expression signature in CIS samples including selectively upregulated known druggable targets MTOR, TYK2, AXIN1, CPT1B, GAK, and PIEZO1 and selectively downregulated BRD2 and NDUFB2. High expression of selected genes was significantly associated with CIS in an independent dataset. Mutation analysis of matched CIS and papillary tumors revealed shared mutations between samples across time points and mutational heterogeneity. CCDC138 was the most frequently mutated gene in CIS. The immunological landscape showed higher levels of PD-1-positive cells in CIS lesions compared to papillary tumors. We identified CIS lesions to have distinct characteristics compared to papillary tumors potentially contributing to the aggressive phenotype.

Biporous silica nanostructure-induced nanovortex in microfluidics for nucleic acid enrichment, isolation, and PCR-free detection.

Efficient pathogen enrichment and nucleic acid isolation are critical for accurate and sensitive diagnosis of infectious diseases, especially those with low pathogen levels. Our study introduces a biporous silica nanofilms-embedded sample preparation chip for pathogen and nucleic acid enrichment/isolation. This chip features unique biporous nanostructures comprising large and small pore layers. Computational simulations confirm that these nanostructures enhance the surface area and promote the formation of nanovortex, resulting in improved capture efficiency. Notably, the chip demonstrates a 100-fold lower limit of detection compared to conventional methods used for nucleic acid detection. Clinical validations using patient samples corroborate the superior sensitivity of the chip when combined with the luminescence resonance energy transfer assay. The enhanced sample preparation efficiency of the chip, along with the facile and straightforward synthesis of the biporous nanostructures, offers a promising solution for polymer chain reaction-free detection of nucleic acids.

Safety and outcome of treatment of latent tuberculosis infection in liver transplant recipients.

PURPOSE: Liver transplant (LT) recipients have an increased risk of tuberculosis (TB), which is associated with higher mortality rates. This retrospective cohort study assessed the outcome and tolerability of screening and treatment of latent tuberculosis infection (LTBI) in LT recipients. METHODS: Between March 2020 and February 2022, all adult LT candidates at our institution were screened for LTBI. The candidates who tested positive for interferon-γ-releasing assay or met epidemiological or clinical-radiological criteria for LTBI were treated and monitored. RESULTS: Among the 857 LT recipients, 199 (23.2%) were diagnosed with LTBI, of which 171 (85.9%) initiated LTBI treatment. The median duration of follow-up was 677 days. Adequate LTBI treatment occurred in 141/171 (82.5%) patients and was discontinued prematurely in 30/171 (17.5%) patients. The most common reason for discontinuation was liver enzyme elevation (11/30, 36.7%), although only five discontinued treatment due to suspicion of isoniazid-associated hepatotoxicity. None of the LTBI-treated patients developed active TB during the follow-up period, while 3.6% (1/28) of untreated LTBI patients and 0.6% (4/658) of patients without LTBI developed TB. CONCLUSION: These findings demonstrate that LTBI screening and treatment is a safe and effective strategy to prevent TB in LT recipients. However, monitoring for adverse events and liver enzyme elevation is recommended.

Validation of a new risk stratification system-based management for methicillin-resistant Staphylococcus aureus bacteraemia: analysis of a multicentre prospective study.

PURPOSE: Distinguishing between complicated and uncomplicated Staphylococcus aureus bacteraemia (SAB) is therapeutically essential. However, this distinction has limitations in reflecting the heterogeneity of SAB and encouraging targeted diagnostics. Recently, a new risk stratification system for SAB metastatic infection, involving stepwise approaches to diagnosis and treatment, has been suggested. We assessed its applicability in methicillin-resistant SAB (MRSAB) patients. METHODS: We retrospectively analysed data of a 3-year multicentre, prospective cohort of hospitalised patients with MRSAB. We classified the patients into three risk groups: low, indeterminate, and high, based on the new system and compared between-group management and outcomes. RESULTS: Of 380 patients with MRSAB, 6.3% were classified as low-, 7.6% as indeterminate-, and 86.1% as high-risk for metastatic infection. No metastatic infection occurred in the low-, 6.9% in the indeterminate-, and 19.6% in the high-risk groups (P < 0.001). After an in-depth diagnostic work-up, patients were finally diagnosed as 'without metastatic infection (6.3%)', 'with metastatic infection (17.4%)', and 'uncertain for metastatic infection (76.3%)'. 30-day mortality increased as the severity of diagnosis shifted from 'without metastatic infection' to 'uncertain for metastatic infection' and 'with metastatic infection' (P = 0.09). In multivariable analysis, independent factors associated with metastatic complications were suspicion of endocarditis in transthoracic echocardiography, clinical signs of metastatic infection, Pitt bacteraemia score ≥ 4, and persistent bacteraemia. CONCLUSIONS: The new risk stratification system shows promise in predicting metastatic complications and guiding work-up and management of MRSAB. However, reducing the number of cases labelled as 'high-risk' and 'uncertain for metastatic infection' remains an area for improvement.

Retrospective Multicenter Analysis of Prognostic Risk Factors for One Year Recurrence in Patient With Renal Cell Carcinoma After Partial or Radical Nephrectomy: Results of Korean Renal Cancer Study Group (KRoCS) Database.

BACKGROUND: We sought to identify prognostic risk factors for one year recurrence in patient with renal cell carcinoma (RCC) after partial or radical nephrectomy. METHODS: We performed a retrospective study of 1,269 patients with RCC after partial or radical nephrectomy and diagnosed recurrence using Korean Renal Cancer Study Group (KRoCS) database between January 1991 and March 2017. Recurrence-free survival (RFS), and overall survival (OS) were calculated using the Kaplan-Meier method and multivariate Cox regression analysis were performed to evaluate independent prognostic factors for recurrence. RESULTS: The median patient age was 56 years and median follow-up period was 67 months. Multivariable analysis demonstrated BMI greater than or equal to 23 and less than 30 (vs. BMI less than 23, hazard ratio [HR]: 0.707, P = 0.020) reduced recurrence one year postoperatively. Eastern Cooperative Oncology Group performance status (ECOG PS) greater than or equal to 1 (vs. ECOG PS 0, HR: 1.548, P = 0.007), high pathological T stage (pT2 vs. pT1, HR: 2.622, P < 0.001; pT3 vs. pT1, HR: 4.256, P < 0.001; pT4 vs. pT1, HR: 4.558, P < 0.001), and tumor necrosis (vs. no tumor necrosis, HR: 2.822, P < 0.001) were independent predictive factors for early recurrence within one year in patients with RCC. Statistically significant differences on RFS and OS were found among pathological T stages (pT2 vs. pT1; pT3 vs. pT1; pT4 vs. pT1, all P < 0.001). CONCLUSION: This large multicenter study demonstrated ECOG PS greater than or equal to 1, high pathological T stage, tumor necrosis and BMI less than 23 were significant prognostic risk factors of early recurrence within one year in patients with RCC who underwent nephrectomy.

The origin of sequence type 72 community-associated methicillin-resistant Staphylococcus aureus (MRSA) and fusidic acid (FA) resistant sequence type 5 MRSA: Analysis of FA resistance and spa type in a single center in South Korea.

INTRODUCTION: We investigated the prevalence of fusidic acid (FA) resistance in MSSA and MRSA stratified by sequence (ST) and spa types, and determined the prevalence of FA resistance mechanisms. METHODS: From August 2014 to April 2020, S. aureus blood isolates were collected in Asan Medical Center, Seoul, South Korea. Antimicrobial susceptibility tests were performed using broth microdilution and interpreted according to EUCAST's FA criteria. We performed spa typing for fusA mutation presence and acquired FA resistance determinants (fusB, fusC, and fusD) by PCR. RESULTS: Of the 590 MRSA isolates, 372 were FA resistant, and among 425 MSSA isolates, 136 were resistant. Of the 380 ST5-MRSA isolates, 350 were FA resistant, whereas only 1 of 14 ST5-MSSA isolates was FA resistant. Conversely, of the 163 ST72-MRSA isolates, only 8 were resistant, whereas 37 of 42 ST72-MSSA were resistant. The fusA mutation (80%) was the most common determinant. The one FA resistant ST5-MSSA isolate belonged to the t2460 spa type, the most common spa type (24 of 35 isolates) of FA resistant ST5-MRSA. In addition, t324 and t148, which are minor spa types of ST72-MSSA, were susceptible to FA, in contrast to other ST72-MSSA spa types, and the major spa type of ST72-MRSA (110 of 163 isolates). CONCLUSIONS: FA resistance was common in ST5-MRSA and ST72-MSSA, and rare in ST5-MSSA and ST72-MRSA. Our findings suggest that minor clones of ST5-MSSA isolates, with the fusA mutation and minor clones of ST72-MSSA susceptible to FA, may have evolved to harbor the mecA gene.