Risk factors for critical COVID-19 illness during Delta- and Omicron-predominant period in Korea; using K-COV-N cohort in the National health insurance service

BACKGROUND

This study evaluated the clinical characteristics of patients with COVID-19 in Korea, and examined the relationship between severe COVID-19 cases and underlying health conditions during the Delta (September 20, 2021 to December 4, 2021) and the Omicron (February 20, 2022 to March 31, 2022) predominant period.

METHODS

This study assessed the association between critical COVID-19 illness and various risk factors, including a variety of underlying health conditions, using multiple logistic regression models based on the K-COV-N cohort, a nationwide data of confirmed COVID-19 cases linked with COVID-19 vaccination status and the National Health Insurance claim information.

RESULTS

We analyzed 137,532 and 8,294,249 cases of COVID-19 infection during the Delta and the Omicron variant dominant periods, respectively. During the Delta as well as the Omicron period, old age (≥80 years) showed the largest effect size among risk factors for critical COVID-19 illness (aOR = 18.08; 95% confidence interval [CI] = 14.71-22.23 for the Delta; aOR = 24.07; 95% CI = 19.03-30.44 for the Omicron period). We found that patients with solid organ transplant (SOT) recipients, unvaccinated, and interstitial lung disease had more than a two-fold increased risk of critical COVID-19 outcomes between the Delta and Omicron periods. However, risk factors such as urban residence, underweight, and underlying medical conditions, including chronic cardiac diseases, immunodeficiency, and mental disorders, had different effects on the development of critical COVID-19 illness between the Delta and Omicron periods.

CONCLUSION

We found that the severity of COVID-19 infection was much higher for the Delta variant than for the Omicron. Although the Delta and the Omicron variant shared many risk factors for critical illness, several risk factors were found to have different effects on the development of critical COVID-19 illness between those two variants. Close monitoring of a wide range of risk factors for critical illness is warranted as new variants continue to emerge during the pandemic.

Magnitude and Duration of Serum Neutralizing Antibody Titers Induced by a Third mRNA COVID-19 Vaccination against Omicron BA.1 in Older Individuals

BACKGROUND

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant (B.1.1.529) is dominating coronavirus disease 2019 (COVID-19) worldwide. The waning protective effect of available vaccines against the Omicron variant is a critical public health issue. This study aimed to assess the impact of the third COVID-19 vaccination on immunity against the SARS-CoV-2 Omicron BA.1 strain in older individuals.

MATERIALS AND METHODS

Adults aged ≥60 years who had completed two doses of the homologous COVID-19 vaccine with either BNT162b2 (Pfizer/BioNTech, New York, NY, USA, BNT) or ChAdOx1 nCoV (SK bioscience, Andong-si, Gyeongsangbuk-do, Korea, ChAd) were registered to receive the third vaccination. Participants chose either BNT or mRNA-1273 (Moderna, Norwood, MA, USA, m1273) mRNA vaccine for the third dose and were categorized into four groups: ChAd/ChAd/BNT, ChAd/ChAd/m1273, BNT/BNT/BNT, and BNT/BNT/m1273. Four serum specimens were obtained from each participant at 0, 4, 12, and 24 weeks after the third dose (V1, V2, V3, and V4, respectively). Serum-neutralizing antibody (NAb) activity against BetaCoV/Korea/KCDC03/2020 (NCCP43326, ancestral strain) and B.1.1.529 (NCCP43411, Omicron BA.1 variant) was measured using plaque reduction neutralization tests. A 50% neutralizing dilution (ND50) >10 was considered indicative of protective NAb titers.

RESULTS

In total, 186 participants were enrolled between November 24, 2021, and June 30, 2022. The respective groups received the third dose at a median (interquartile range [IQR]) of 132 (125 - 191), 123 (122 - 126), 186 (166 - 193), and 182 (175 - 198) days after the second dose. Overall, ND50 was lower at V1 against Omicron BA.1 than against the ancestral strain. NAb titers against the ancestral strain and Omicron BA.1 variant at V2 were increased at least 30-fold (median [IQR], 1235.35 [1021.45 - 2374.65)] and 129.8 [65.3 - 250.7], respectively). ND50 titers against the ancestral strain and Omicron variant did not differ significantly among the four groups (P = 0.57). NAb titers were significantly lower against the Omicron variant than against the ancestral strain at V3 (median [IQR], 36.4 (17.55 - 75.09) vs. 325.9 [276.07 - 686.97]; P = 0.012). NAb titers against Omicron at V4 were 16 times lower than that at V3. Most sera exhibited a protective level (ND50 >10) at V4 (75.0% [24/32], 73.0% [27/37], 73.3% [22/30], and 70.6% [12/17] in the ChAd/ChAd/BNT, ChAd/ChAd/m1273, BNT/BNT/BNT, and BNT/BNT/m1273 groups, respectively), with no significant differences among groups (P = 0.99).

CONCLUSION

A third COVID-19 mRNA vaccine dose restored waning NAb titers against Omicron BA.1. Our findings support a third-dose vaccination program to prevent the waning of humoral immunity to SARS-CoV-2.

Propensity score matched analysis for the safety and effectiveness of remdesivir in COVID-19 patients with renal impairment

BACKGROUNDS

Remdesivir (RDV) is an antiviral agent approved for the treatment of coronavirus disease 2019 (COVID-19); however, is not recommended for patients with renal impairment. Due to limitations associated with prospective clinical trials, real-world data on the safety and efficacy of RDV in patients with renal impairment are necessary.

METHODS

Propensity score-matched (PSM) retrospective analysis was conducted between March 2020 and September 2022 in COVID-19 patients with an eGFR < 30 mL/min in four Korean hospitals. The RDV treatment group was matched to the untreated control group. The safety and clinical outcomes in patients who received RDV were analyzed.

RESULTS

A total of 564 patients were enrolled; 229 patients received RDV either for treatment or prophylaxis. On day 5, no difference in nephrotoxicity was observed between the two groups, and liver enzyme levels were within the normal range. In multivariate analysis for new dialysis, RDV treatment was not a risk factor for new dialysis. Among the 564 patients, 417 were indicated for a 5-day course of RDV treatment and 211 patients were treated with RDV. After PSM, no differences in the clinical outcomes were observed between the two groups.

CONCLUSION

RDV use in COVID-19 patients with renal impairment did not result in significant nephrotoxicity or hepatotoxicity.

The association between antibody responses and prolonged viable SARS-CoV-2 shedding in immunocompromised patients: a prospective cohort study

Immunocompromised COVID-19 patients were prospectively enrolled from March to November 2022 to understand the association between antibody responses and SARS-CoV-2 shedding. A total of 62 patients were analyzed and the results indicated a faster decline in genomic and subgenomic viral RNA in patients with higher neutralizing and S1-specific IgG antibodies (both P < 0.001). Notably, high neutralizing antibody levels were associated with a significantly faster decrease in viable virus cultures (P = 0.04). Our observations suggest the role of neutralizing antibodies in prolonged virus shedding in immunocompromised patients, highlighting the potential benefits of enhancing their humoral immune response through vaccination or monoclonal antibody treatments.

Virological characteristics and the rapid antigen test as deisolation criteria in immunocompromised patients with COVID-19: A prospective cohort study

There are limited data supporting current Centers for Disease Control and Prevention guidelines for the isolation period in moderate to severely immunocompromised patients with coronavirus disease 2019 (COVID-19). Adult COVID-19 patients who underwent solid organ transplantation (SOT) or received active chemotherapy against hematologic malignancy were enrolled and weekly respiratory samples were collected. Samples with positive genomic real-time polymerase chain reaction results underwent virus culture and rapid antigen testing (RAT). A total of 65 patients (40 with hematologic malignancy and 25 SOT) were enrolled. The median duration of viable virus shedding was 4 weeks (interquartile range: 3-7). Multivariable analysis revealed that B-cell depletion (hazard ratio [HR]: 4.76) was associated with prolonged viral shedding, and COVID-19 vaccination (≥3 doses) was negatively associated with prolonged viral shedding (HR: 0.22). The sensitivity, specificity, positive predictive value, and negative predictive value of RAT for viable virus shedding were 79%, 76%, 74%, and 81%, respectively. The negative predictive value of RAT was only 48% (95% confidence interval [CI]: 33-65) in the samples from those with symptom onset ≤20 days, but it was as high as 92% (95% CI: 85-96) in the samples from those with symptom onset >20 days. About half of immunocompromised COVID-19 patients shed viable virus for ≥4 weeks from the diagnosis, and virus shedding was prolonged especially in unvaccinated patients with B-cell-depleting therapy treatment. RAT beyond 20 days in immunocompromised patients had a relatively high negative predictive value for viable virus shedding.

Real-World Effectiveness of Nirmatrelvir-Ritonavir and Its Acceptability in High-Risk COVID-19 Patients

BACKGROUND

Nirmatrelvir-ritonavir is highly effective in preventing severe coronavirus disease 2019 (COVID-19) in high-risk patients with mild-to-moderate severity. However, real-world performance data are limited, and the drug is not so acceptable to the COVID-19 patients at high risk who need it in Korea.

METHODS

To evaluate the effectiveness of nirmatrelvir-ritonavir, we conducted a propensity score-matched retrospective cohort study on patients with mild-to-moderate COVID-19 at high risk for a severe disease who were hospitalized at four hospitals in South Korea from February 2022 to April 2022. A total of 236 patients in the treatment group (administered nirmatrelvir-ritonavir) and 236 in the matched control group (supportive care only) were analyzed for the primary outcome, i.e., the time to oxygen support-free survival. The secondary outcome was a composite result of disease progression. The reason for not prescribing nirmatrelvir-ritonavir to the indicated patients was also investigated.

RESULTS

The treatment group showed significantly longer oxygen support-free survival than the matched control group (adjusted hazard ratio [aHR], 0.07; 95% confidence interval [CI], 0.01-0.31; P < 0.001). Multivariate Cox regression analysis showed that age (aHR, 1.03; 95% CI, 1.00-1.07), National Early Warning Score-2 at admission (aHR, 1.36; 95% CI, 1.08-1.71), nirmatrelvir-ritonavir treatment, female sex (aHR, 0.37; 95% CI, 0.15-0.88), and time from symptom onset to admission (aHR, 0.67; 95% CI, 0.48-0.95) were significantly associated with oxygen therapy. However, none of the factors were related to the composite outcome. In the unmatched control group, 19.9% of 376 patients had documented explanations for nirmatrelvir-ritonavir non-prescription, and 44.0% of these were due to contraindication criteria. In the treatment group, 10.9% of patients discontinued the medication primarily because of adverse events (71.4%), with gastrointestinal symptoms being the most common (50.0%).

CONCLUSION

Nirmatrelvir-ritonavir treatment significantly reduced oxygen therapy requirements in high-risk patients with COVID-19 during the omicron variant surge in South Korea. Physicians are encouraged to consider the active use of nirmatrelvir-ritonavir and to be watchful for gastrointestinal symptoms during medication.

Short-Term Effectiveness of Oral Nirmatrelvir/Ritonavir Against the SARS-CoV-2 Omicron Variant and Culture-Positive Viral Shedding

BACKGROUND

Information on the effectiveness of nirmatrelvir/ritonavir against the omicron is limited. The clinical response and viral kinetics to therapy in the real world need to be evaluated.

METHODS

Mild to moderate coronavirus disease 2019 (COVID-19) patients with risk factors for severe illness were prospectively enrolled as a treatment group with nirmatrelvir/ritonavir therapy versus a control group with supportive care. Serial viral load and culture from the upper respiratory tract were evaluated for seven days, and clinical responses and adverse reactions were evaluated for 28 days.

RESULTS

A total of 51 patients were analyzed including 40 in the treatment group and 11 in the control group. Faster symptom resolution during hospitalization (P = 0.048) was observed in the treatment group. Only minor adverse reactions were reported in 27.5% of patients. The viral load on Day 7 was lower in the treatment group (P = 0.002). The viral culture showed a positivity of 67.6% (25/37) vs. 100% (6/6) on Day 1, 0% (0/37) vs. 16.7 (1/6) on Day 5, and 0% (0/16) vs. 50.0% (2/4) on Day 7 in the treatment and control groups, respectively.

CONCLUSIONS

Nirmatrelvir/ritonavir against the omicron was safe and resulted in negative viral culture conversion after Day 5 of treatment with better symptomatic resolution.

Kinetics of vaccine-induced neutralizing antibody titers and estimated protective immunity against wild-type SARS-CoV-2 and the Delta variant: A prospective nationwide cohort study comparing three COVID-19 vaccination protocols in South Korea

Introduction

Despite vaccine development, the COVID-19 pandemic is ongoing due to immunity-escaping variants of concern (VOCs). Estimations of vaccine-induced protective immunity against VOCs are essential for setting proper COVID-19 vaccination policy.

Methods

We performed plaque-reduction neutralizing tests (PRNTs) using sera from healthcare workers (HCWs) collected from baseline to six months after COVID-19 vaccination and from convalescent COVID-19 patients. The 20.2% of the mean PRNT titer of convalescent sera was used as 50% protective value, and the percentage of HCWs with protective immunity for each week (percent-week) was compared among vaccination groups. A correlation equation was deduced between a PRNT 50% neutralizing dose (ND50) against wild type (WT) SARS-CoV-2 and that of the Delta variant.

Results

We conducted PRNTs on 1,287 serum samples from 297 HCWs (99 HCWs who received homologous ChAdOx1 vaccination (ChAd), 99 from HCWs who received homologous BNT162b2 (BNT), and 99 from HCWs who received heterologous ChAd followed by BNT (ChAd-BNT)). Using 365 serum samples from 116 convalescent COVID-19 patients, PRNT ND50 of 118.25 was derived as 50% protective value. The 6-month cumulative percentage of HCWs with protective immunity against WT SARS-CoV-2 was highest in the BNT group (2297.0 percent-week), followed by the ChAd-BNT (1576.8) and ChAd (1403.0) groups. In the inter-group comparison, protective percentage of the BNT group (median 96.0%, IQR 91.2–99.2%) was comparable to the ChAd-BNT group (median 85.4%, IQR 15.7–100%; P =0.117) and significantly higher than the ChAd group (median 60.1%, IQR 20.0–87.1%; P &lt;0.001). When Delta PRNT was estimated using the correlation equation, protective immunity at the 6-month waning point was markedly decreased (28.3% for ChAd group, 52.5% for BNT, and 66.7% for ChAd-BNT).

Conclusion

Decreased vaccine-induced protective immunity at the 6-month waning point and lesser response against the Delta variant may explain the Delta-dominated outbreak of late 2021. Follow-up studies for newly-emerging VOCs would also be needed.

Heterologous ChAdOx1 and BNT162b2 vaccination induces strong neutralizing antibody responses against SARS-CoV-2 including delta variant with tolerable reactogenicity

OBJECTIVES

We assessed humoral responses and reactogenicity following the heterologous vaccination compared to the homologous vaccination groups.

METHODS

We enrolled healthcare workers (HCWs) who were either vaccinated with ChAdOx1 followed by BNT162b2 (heterologous group) or two doses of ChAdOx1 (ChAdOx1 group) or BNT162b2 (BNT162b2 group). Immunogenicity was assessed by measuring antibody titers against receptor-binding domain (RBD) of SARS-CoV-2 spike protein in all participants and neutralizing antibody titer in 100 participants per group. Reactogenicity was evaluated by a questionnaire-based survey.

RESULTS

We enrolled 499 HCWs (ChAdOx1, n=199; BNT162b2, n=200; heterologous ChAdOx1/BNT162b2, n=100). The geometric mean titer of anti-RBD antibody at 14 days after the booster dose was significantly higher in the heterologous group (11780.55 BAU/mL [95% CI, 10891.52-12742.14]) than in the ChAdOx1 (1561.51 [1415.03-1723.15]) or BNT162b2 (2895.90 [2664.01-3147.98]) groups (both P value<.001). The neutralizing antibody titer of the heterologous group (geometric mean ND_50, 2367.74 [1970.03-2845.74]) was comparable to that of the BNT162b2 group (2118.63 [1755.88-2556.32], P >.05) but higher than that of the ChAdOx1 group (391.77 [326.16-470.59], P value<.001). Compared with those against wild-type SARS-CoV-2, the geometric mean neutralizing antibody titers against the delta variant at 14 days after the boosting were reduced by 3.0-fold in the heterologous group (geometric mean ND_50. 872.01 [95% CI, 685.33-1109.54]), 4.0-fold in the BNT162b2 group (337.93 [262.78-434.57]), and 3.2-fold in the ChAdOx1 group (206.61 [144.05-296.34]). The local or systemic reactogenicity after the booster dose in the heterologous group was higher than that of the ChAdOx1 group but comparable to that of the BNT162b2 group.

CONCLUSIONS

Heterologous ChAdOx1 followed by BNT162b2 vaccination with a 12-week interval induced a robust humoral immune response against SARS-CoV-2 including the delta variant that was comparable to the homologous BNT162b2 vaccination and stronger than the homologous ChAdOx1 vaccination, with a tolerable reactogenicity profile.

Booster BNT162b2 COVID-19 Vaccination Increases Neutralizing Antibody Titers Against the SARS-CoV-2 Omicron Variant in Both Young and Elderly Adults

Concerns about the effectiveness of current vaccines against the rapidly spreading severe acute respiratory syndrome-coronavirus-2 omicron (B.1.1.529) variant are increasing. This study aimed to assess neutralizing antibody activity against the wild-type (BetaCoV/Korea/KCDC03/2020), delta, and omicron variants after full primary and booster vaccinations with BNT162b2. A plaque reduction neutralization test was employed to determine 50% neutralizing dilution (ND₅₀) titers in serum samples. ND₅₀ titers against the omicron variant (median [interquartile range], 5.3 [< 5.0-12.7]) after full primary vaccination were lower than those against the wild-type (144.8 [44.7-294.0]) and delta (24.3 [14.3-81.1]) variants. Furthermore, 19/30 participants (63.3%) displayed lower ND₅₀ titers than the detection threshold (< 10.0) against omicron after full primary vaccination. However, the booster vaccine significantly increased ND₅₀ titers against BetaCoV/Korea/KCDC03/2020, delta, and omicron, although titers against omicron remained lower than those against the other variants (P < 0.001). Our study suggests that booster vaccination with BNT162b2 significantly increases humoral immunity against the omicron variant.

Clinical Characteristics of 40 Patients Infected With the SARS-CoV-2 Omicron Variant in Korea

Since severe acute respiratory syndrome-coronavirus-2 variant B.1.1.529 (omicron) was first reported to the World Health Organization on November 24, 2021, the cases of the omicron variant have been detected in more than 90 countries over the last month. We investigated the clinical and epidemiological characteristics of the first 40 patients with the omicron variant who had been isolated at the National Medical Center in South Korea during December 4-17, 2021. The median age of the patients was 39.5 years. Twenty-two patients (55%) were women. Seventeen patients (42.5%) were fully vaccinated, and none were reinfected with the omicron. Eighteen (45%) had recent international travel history. Half of the patients (19, 47.5%) were asymptomatic, while the others had mild symptoms. Six patients (15%) showed lung infiltrations on chest image; however, none required supplemental oxygen. These mild clinical features are consistent with recent case reports on the omicron variant from other countries.

Genomic characterization of nine Clostridioides difficile strains isolated from Korean patients with Clostridioides difficile infection

Background

Clostridioides difficile infection (CDI) is an infectious nosocomial disease caused by Clostridioides difficile, an opportunistic pathogen that occurs in the intestine after extensive antibiotic regimens.

Results

Nine C. difficile strains (CBA7201–CBA7209) were isolated from nine patients diagnosed with CDI at the national university hospital in Korea, and the whole genomes of these strains were sequenced to identify their genomic characteristics. Comparative genomic analysis was performed using 51 reference strains and the nine isolated herein. Phylogenetic analysis based on 16S rRNA gene sequences confirmed that all 60 C. difficile strains belong to the genus Clostridioides, while core-genome tree indicated that they were divided into five groups, which was consistent with the results of MLST clade analysis. All strains were confirmed to have a clindamycin antibiotic resistance gene, but the other antibiotic resistance genes differ depending on the MLST clade. Interestingly, the six strains belonging to the sequence type 17 among the nine C. difficile strains isolated here exhibited unique genomic characteristics for PaLoc and CdtLoc, the two toxin gene loci identified in this study, and harbored similar antibiotic resistance genes.

Conclusion

In this study, we identified the specific genomic characteristics of Korean C. difficile strains, which could serve as basic information for CDI prevention and treatment in Korea.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13099-021-00451-3.

Dysfunctional accessory gene regulator (agr) as a prognostic factor in invasive Staphylococcus aureus infection: a systematic review and meta-analysis

The accessory gene regulator (agr) locus of Staphylococcus aureus is a quorum-sensing virulence regulator. Although there are many studies concerning the effect of dysfunctional agr on the outcomes of S. aureus infection, there is no systematic review to date. We systematically searched for clinical studies reporting outcomes of invasive S. aureus infections and the proportion of dysfunctional agr among their causative strains, and we performed a meta-analysis to obtain estimates of the odds of outcomes of invasive S. aureus infection with dysfunctional versus functional agr. Of 289 articles identified by our research strategy, 20 studies were meta-analysed for crude analysis of the impact of dysfunctional agr on outcomes of invasive S. aureus infection. Dysfunctional agr was generally associated with unfavourable outcomes (OR 1.32, 95% CI 1.05–1.66), and the impact of dysfunctional agr on outcome was more prominent in invasive methicillin-resistant S. aureus (MRSA) infections (OR 1.54, CI 1.20–1.97). Nine studies were meta-analysed for the impact of dysfunctional agr on the 30-day mortality of invasive S. aureus infection. Invasive MRSA infection with dysfunctional agr exhibited higher 30-day mortality (OR 1.40, CI 1.03–1.90) than that with functional agr. On the other hand, invasive MSSA infection with dysfunctional agr exhibited lower 30-day mortality (OR 0.51, CI 0.27–0.95). In the post hoc subgroup analysis by the site of MRSA infection, dysfunctional agr was associated with higher 30-day mortality in MRSA pneumonia (OR 2.48, CI 1.17–5.25). The effect of dysfunctional agr on the outcome of invasive S. aureus infection may vary depending on various conditions, such as oxacillin susceptibility and the site of infection. Dysfunctional agr was generally associated with unfavourable clinical outcomes and its effect was prominent in MRSA and pneumonia. Dysfunctional agr may be applicable for outcome prediction in cases of invasive MRSA infection with hardly eradicable foci such as pneumonia.

Prosthetic valve endocarditis by Trichosporon mucoides: A case report and review of literature

NATIONALE

Trichosporon species are widely distributed in nature and are emerging opportunistic human pathogens. Trichosporon infections are associated with superficial cutaneous involvement in immunocompetent individuals to severe systemic disease in immunocompromised patients. Until now, there is no report in infective endocarditis by Trichosporon mucoides confirmed by molecular diagnostics PATIENT CONCERNS:: A 66-year-old man presented with a fever that had occurred for a period of 6 months. He had undergone aortic valve replacement 10 years prior. Transthoracic echocardiography showed vegetations on the prosthetic aortic valve and native mitral valve. T mucoides was detected in the cultures of blood and vegetations.

DIAGNOSIS

DNA sequencing using D/D2 region of rRNA and internal transcribed spacer were performed.

INTERVENTIONS

Infections were successfully controlled with valve replacement and voriconazole plus liposomal amphotericin B therapy.

OUTCOMES

There has been no sign of recurrence for 18-months after treatment completion.

LESSONS

This is the first reported case of infective endocarditis due to T mucoides. Clinicians should consider Trichosporon species as causative agents of endocarditis in patients who have undergone cardiac surgery.

Antimicrobial susceptibility of Staphylococcus species isolated from prosthetic joints with a focus on fluoroquinolone-resistance mechanisms

We investigated susceptibility to antimicrobials of 89 staphylococcal species from PJIs and analyzed fluoroquinolone (FQ)-resistance mechanisms. Staphylococcal isolates showed high resistance to oral antimicrobials, with the exception of TMP-STX and linezolid. The main mechanism of resistance to FQ was mutations in quinolone-resistance-determining-regions. Fifteen percent of Staphylococcus aureus overexpressed efflux-pump genes.

The microbiological characteristics of Staphylococcus aureus isolated from patients with native valve infective endocarditis

The microbiological characteristics of Staphylococcus aureus causing infective endocarditis (IE) have not been investigated thoroughly. We compared the characteristics of S. aureus isolates from patients with and without IE. Cases of S. aureus bacteremia (SAB) were collected from 10 hospitals over 7 years. Cases of native valve IE were matched with non-IE controls according to the following criteria: central-line-associated infection, community-acquired infection, methicillin susceptibility, and if possible, the primary site of infection. Genes coding virulence factors were analyzed using multiplex polymerase chain reactions. Fibrinogen and fibronectin-binding properties were assessed using in vitro binding assays. The fibronectin-binding protein A gene (fnbpA) was sequenced. Of 2,365 cases of SAB, 92 had IE. After matching, 37 pairs of S. aureus isolates from the IE cases and non-IE controls were compared; fnbpA was detected in 91.9% of the IE isolates and 100% of the non-IE isolates (p = 0.24). While the fibrinogen binding ratio was similar (1.07 ± 0.33 vs. 1.08 ± 0.26, p = 0.89), the fibronectin-binding ratio was significantly higher in the IE-group (1.31 ± 0.42 vs. 1.06 ± 0.31, p = 0.01). The proportions of major single-nucleotide polymorphisms in fnbpA were as follows: E652D (2.9% vs. 2.7%), H782Q (65.6% vs. 60.6%), and K786N (65.6% vs. 72.7%). The fibronectin-binding ratio was positively correlated with the number of SNPs present in IE cases (p < 0.001) but not in the non-IE controls (p = 0.124). Fibronectin-binding might play a key role in SAB IE. However, the degree of binding may be mediated by genetic variability between isolates.

Microbial Etiology of Pyogenic Vertebral Osteomyelitis According to Patient Characteristics

Background

It is difficult to select an appropriate empirical antibiotic treatment regimen for patients with culture-negative pyogenic vertebral osteomyelitis (PVO). Having knowledge of the distribution of microorganisms according to patient characteristics can help clinicians make informed choices regarding empirical antibiotics. The aim of this study was to determine the microbial distribution among individuals with PVO according to their demographic and clinical characteristics.

Methods

We reviewed the medical records of patients admitted to our hospital with culture-confirmed PVO between January 2005 and December 2017 and collected data on demographics, underlying diseases, and radiographic and microbiological results. Statistical analysis was performed to identify associations between specific bacteria and specific patient characteristics.

Results

A total of 586 patients were included in the study. The prevalence of Staphylococcus aureus infections was higher in young patients than in old patients, while gram-negative bacterial infections and Enterococcus were more prevalent in older patients. Gram-negative bacterial infections were more common in women than in men (32.1% vs 16.4%; P < .05), in patients with cirrhosis than in those without (32.7% vs 21.1%; P < .05), and in patients with a solid tumor than in those without (31.0% vs 20.7%; P < .05). Methicillin-resistant S. aureus infections were more prevalent in patients with chronic renal disease than in those without (34.4% vs 14.7%; P < .05).

Conclusions

The microbial etiology of PVO varies according to patient characteristics. Patient characteristics should thus be considered when choosing empirical antibiotics in patients with culture-negative PVO.

Viral kinetics of SARS-CoV-2 in asymptomatic carriers and presymptomatic patients

From a total of 71 laboratory-confirmed cases, three presymptomatic patients and 10 patients with entirely asymptomatic infections were identified. In two of the three incubation period patients, the viral titer in the presymptomatic period was very high (Ct value<20). The median number of days to first negative RT-PCR in the asymptomatic carriers was 4.5 (range 2.5-9), and all asymptomatic carriers reached a first RT-PCR Ct>35 within 14 days after diagnosis. Patients who have COVID-19 may already be infectious before there are symptoms, and 14 days of isolation after diagnosis may be sufficient in entirely asymptomatic cases.

Comparison of In Vivo Pharmacokinetics and Pharmacodynamics of Vancomycin Products Available in Korea

PURPOSE

Few studies have been investigated the in vivo efficacy of generic vancomycin products available outside of the United States. In this study, we aimed to compare the in vivo pharmacokinetics (PK) and pharmacodynamics (PD) of five generic vancomycin products available in Korea with those of the innovator.

MATERIALS AND METHODS

The in vitro vancomycin purity of each product was examined using high-pressure liquid chromatography. Single-dose PK analyses were performed using neutropenic mice. The in vivo efficacy of vancomycin products was compared with that of the innovator in dose-effect experiments (25 to 400 mg/kg per day) using a thigh-infection model with neutropenic mice.

RESULTS

Generic products had a lower proportion of vancomycin B (range: 90.3-93.8%) and a higher proportion of impurities (range: 6.2-9.7%) than the innovator (94.5% and 5.5%, respectively). In an in vivo single-dose PK study, the maximum concentration (C_max) values of each generic were lower than that of the innovator, and the geographic mean area under the curve ratios of four generics were significantly lower than that of the innovator (all p<0.1). In the thigh-infection model, the maximum efficacies of generic products reflected in maximal effect (E_max) values were not significantly different from the innovator. However, the PD profile curves of some generic products differed significantly from that of the innovator in mice injected with a high level of Mu3 (all p≤0.05).

CONCLUSION

Some generic vancomycin products available in Korea showed inferior PK and PD profiles, especially in mice infected with hetero-vancomycin-resistant Staphylococcus aureus.

Clinical characteristics and risk factors for complications of candidaemia in adults: Focus on endophthalmitis, endocarditis, and osteoarticular infections

OBJECTIVES

This study evaluated the incidence, risk factors, and clinical characteristics of complications of candidaemia in adults, with a focus on endophthalmitis, endocarditis, and osteoarticular infections.

METHODS

All patients ≥18 years old with candidaemia in two Korean tertiary hospitals from 2007 to 2016 were investigated. Complications of candidaemia were defined as the presence of endophthalmitis, endocarditis, or osteoarticular infections documented in patients with candidaemia. The clinical characteristics and risk factors for candidaemia with complications were analysed in the patients who underwent ophthalmological examinations.

RESULTS

Of 765 adult patients with candidaemia, 34 (4.4%) met the definition of complications, including endophthalmitis in 29 (3.8%), endocarditis in 4 (0.5%), and osteoarticular infections in 3 (0.4%). Of the 225 patients who underwent ophthalmological examinations, 29 (12.9%) had endophthalmitis. Candida albicans was an independent risk factor for complicated candidaemia (OR, 5.12; 95% CI, 2.17-12.09; P < 0.001). Although the mortality rate was no higher in complicated candidaemia, the duration of antifungal therapy was longer (23.1 ± 17.6 vs. 16.4 ± 10.8 days, P = 0.042), and 13 patients (39.3%) underwent additional procedures or surgery.

CONCLUSIONS

Complications of candidaemia occurred in 4.4% of adult patients. C. albicans was an independent risk factor for complicated candidaemia in adults. Complications of candidaemia might need prolonged treatment and additional procedures or surgery. Therefore, careful evaluation and active treatment of candidaemia with complications should be encouraged.

544. Clonal Spread of Two Sequence Types of Carbapenem-Resistant Acinetobacter baumannii Blood Isolates at a Tertiary Care Hospital in South Korea Over 2.5 Years

Background

The dissemination of carbapenem-resistant Acinetobacter baumannii (CRAB) became an urgent public health concern. A specific sequence type (ST) of A. bauamannii has been reported to be associated with severity of disease or mortality. This study aimed to determine the genetic relatedness of CRAB blood isolates cultured from patients at a tertiary care hospital and to investigate clinical characteristics and outcome of CRAB bacteremia.

Methods

CRAB blood isolates were collected between June 2016 and December 2018, and their clinical data were obtained. Multi-locus sequence test (MLST) was performed using the Oxford scheme, and the STs were assigned using the MLST database.

Results

Of the 126 CRAB blood isolates, 123 isolates which could be typed by MLST all belonged to clonal complex (CC) 92. During the entire period, ST369 (42.3%) was the most dominant, followed by ST191 (32.5%), ST784 (13.8%) and ST451 (4.1%). ST369 was firstly introduced in August 2017. ST191 (61.4%) was the most abundant during June 2016 to July 2017, whereas ST369 (65.8%) replaced ST191 (16.5%) since August 2017. The time interval between intensive care unit admission and bacteremia was shorter in ST369 than ST191 in multivariate analysis (day, median (Q1, Q3), ST369 6 (3, 9.8), ST191 9 (6, 17), Odd Ratio 0.87 (95% CI 0.76–0.99) P = 0.048 logistic regression). According to the ST, the 7-day and 30-day mortality rates were as follows; 46% and 65% in ST191, 50% and 62% in ST369, and 10.7% and 46.4% in the other STs. Patients infected by ST191 or 369 had significant higher 7-day mortality rates (ST191/369, 48.3% vs. the other STs 10.7%, P = 0.001 by log-rank test) and 30-day mortality rates (ST191/369, 63.2% vs. the other STs, 46.4%, P = 0.045 by log-rank test).

Conclusion

This study demonstrates the clonal spread of two STs at a tertiary care hospital in South Korea over 2.5 years. After the introduction of ST369, it replaced ST 191 and widely disseminated within a hospital. Two predominant STs were associated with poor outcome. Continuous surveillance are necessary to monitor the dissemination of these strains.

Disclosures

All authors: No reported disclosures.

260. Detection of Aspergillus fumigatus Infection in Mice with 2-Deoxy-2-[18F]fluorosorbitol

Background

Invasive aspergillosis is a major cause of infectious morbidity and mortality in immunocompromised patients.However, definitive diagnosis of invasive Aspergillus infection is still difficult due to the lack of a rapid, sensitive and specific diagnostic methods. In this studies, we investigated 2-deoxy-2-[¹⁸F]fluorosorbitol ([¹⁸F]FDS) which has been reported to be accumulated in Gram-negative bacteria but not in Gram-positive bacteria or healthy mammalian or cancer cells, for the imaging detection of Aspergullus fumigatus infections with PET in vivo.

Methods

[¹⁸F]FDS was synthesized by reduction of 2-deoxy-2-[¹⁸F]fluoro-d-glucose ([¹⁸F]FDG) using NaBH₄. When the reaction was complete, the mixture was adjusted to a pH value to 6.5–7.5. Subsequently, the solution was filtered directly into a sterile product vial through a Sep-Pak Alumina N cartridge with a sterile filter. The probe uptake assay was performed by incubating bacterial cell and fungi with [¹⁸F]FDS (20 µCi) at 37°C for 2 h. Female BALB/c were immunosuppressed with cyclophosphamide and cortisone acetate prior to A. fumigatus intranasal, intramuscular, brain infection. The mircoPET images were obtained at 2 h after i.v. injection of [¹⁸F]FDS in infected mice.

Results

In vitro uptake test revealed significantly higher accumulation of [¹⁸F]FDS at 2 hin A. fumigatus, C. albicans and R. oryzae rather than with bacterial strains (Figure 1). PET imaging of BALB/c mice with pulmonary A. fumigatus infections showed obvious accumulation of [¹⁸F]FDS in the infected lungs compared with control (Figure 2). [¹⁸F]FDS PET imaging also detected A. fumigatus muscle and brain infection in mice. In infected shoulder muscle of mice, [¹⁸F]FDS PET imaging showed high legion-to-background ratio at 2 h. (4.05 ± 1.59, Figure 3).

Conclusion

[¹⁸F]FDS PET study demonstrated stable uptake in infected tissue with A. fumigatus and rapid clearance from the blood and other organs. [¹⁸F]FDS could be a useful imaging probe visualizing the invasive aspergillosis in vivo.

Disclosures

All authors: No reported disclosures.

Dysfunction of Circulating Natural Killer T Cells in Patients With Scrub Typhus

Background

Human natural killer T (NKT) cells are known to serve as regulatory and/or effector cells in infectious diseases. However, little is known about the role of NKT cells in Orientia tsutsugamushi infection. Accordingly, the objective of this study was to examine the level and function of NKT cells in patients with scrub typhus.

Methods

This study included 62 scrub typhus patients and 62 healthy controls (HCs). NKT cell level and function in peripheral blood samples were measured by flow cytometry.

Results

Proliferation of NKT cells and their ability to produce interferon-γ and interleukin-4 (IL-4) were significantly lower in scrub typhus patients compared to those in HCs. However, circulating NKT cell levels were comparable between patients and HCs. Expression levels of CD69, programmed death-1 (PD-1), lymphocyte activation gene-3 (LAG-3), and T-cell immunoglobulin domain and mucin domain-containing molecule-3 (TIM-3) were significantly increased in scrub typhus patients. Elevated expression of CD69, PD-1, LAG-3, and TIM-3, impaired proliferation, and decreased IL-4 production by NKT cells were recovered in the remission phase.

Conclusions

This study demonstrates that circulating NKT cells are numerically preserved but functionally impaired in scrub typhus patients. In addition, NKT cell dysfunction is recovered in the remission phase.

Outcomes of Third-Generation Cephalosporin Plus Ciprofloxacin or Doxycycline Therapy in Patients with Vibrio vulnificus Septicemia: A Propensity Score-Matched Analysis

Background

Combination therapy with a third-generation cephalosporin (TGC) and a tetracycline analogue is recommended for Vibrio vulnificus infection. The combination of a TGC and ciprofloxacin has synergistic in vitro bactericidal activity against V. vulnificus. No clinical study has compared the standard regimen with TGC plus ciprofloxacin therapy for V. vulnificus infection.

Methods

Patients with a confirmed V. vulnificus infection at two medical centers in Korea from 1991 to 2016 were enrolled in this study. The patients were grouped according to the type of antibiotic administered. A retrospective propensity-score-matched case-control study of patients treated with TGC plus doxycycline or TGC plus ciprofloxacin was performed. The clinical characteristics and outcomes of the patients were analyzed.

Results

A total of 218 patients were confirmed to have V. vulnificus septicemia during the study, and the 30-day survival rate was 39% (85/218). The patients were classified into the following six treatment groups: TGC monotherapy (n = 82), TGC plus doxycycline therapy (n = 42), TGC plus ciprofloxacin therapy (n = 39), ciprofloxacin monotherapy (n = 14), other β-lactam monotherapy (n = 10), and other (n = 31). The survival rates of these groups were as follows: TGC monotherapy (35%), TGC plus doxycycline (38%), TGC plus ciprofloxacin (54%), ciprofloxacin monotherapy (29%), other β-lactam (20%), and other (39%). The 30-day survival rate showed no significant difference between the TGC plus doxycycline and TGC plus ciprofloxacin groups (log-rank test, P = 0.18). Among the 81 patients treated with TGC plus doxycycline or TGC plus ciprofloxacin, 12 per treatment group were selected by propensity-score matching. There was no significant difference in the baseline characteristics or the frequency of fasciotomy between the two groups. The 30-day survival rate showed no significant difference between the TGC plus doxycycline (50%) and TGC plus ciprofloxacin (67%) groups (log-rank test, P = 0.46).

Conclusion

Our data suggest that the outcome of TGC plus ciprofloxacin therapy was comparable to that of TGC plus doxycycline therapy in patients with V. vulnificus septicemia.

The combination of a third-generation cephalosporin (TGC) and ciprofloxacin has synergy in vitro bactericidal activity against V. vulnificus. No clinical study has compared the standard regimen with TGC plus ciprofloxacin therapy for V. vulnificus infection. A total of 218 patients were enrolled who are confirmed to have V. vulnificus septicemia in two medical centers in Korea from 1991 to 2016. The 30-day survival rate was 39% (85/218) for all patients, 38% (16/42) for TGC plus doxycycline and 54% (21/39) for TGC plus ciprofloxacin (log rank test, P = 0.18). A propensity score-matched analysis was performed and 12 per treatment groups were selected. The 30-day survival rate showed no significant difference between the TGC plus doxycycline (50%, 6/12) and TGC plus ciprofloxacin (67%, 4/12) groups (log-rank test, P = 0.46). The outcome of TGC plus ciprofloxacin therapy was comparable to that of TGC plus doxycycline therapy in patients with V. vulnificus septicemia.

Immunogenicity and safety of a new live attenuated herpes zoster vaccine (NBP608) compared to Zostavax® in healthy adults aged 50 years and older

A multi-centre, randomised, double-blinded, active-controlled, parallel-group clinical trial was carried out to assess the immunogenicity and safety of NBP608-a newly developed live-attenuated zoster vaccine in Korea-relative to Zostavax® in healthy adults aged 50 years or older. Immune responses to the vaccine were evaluated by glycoprotein enzyme-linked immunosorbent assay (gpELISA) and enzyme-linked immunosorbent spot (ELISPOT) assays using the interferon (IFN)-γ and interleukin (IL)-2 FluoroSpot kit 6 weeks after vaccination. Safety was monitored for 26 weeks based on subjects' diaries, spontaneous reports from subjects, and history taking by the investigators. A total of 845 subjects participated in the screening, and 823 received the vaccination (413 in the NBP608 group and 411 in the comparator group). The gpELISA-determined geometric mean fold rise from baseline to post NBP608 vaccination was 2.75 [95% confidence interval, CI (2.57, 2.94)]. The gpELISA-determined adjusted geometric mean titers (GMTs) of NBP608 and the comparator were 1346.37 [95% CI (1273.99, 1422.87)] and 1674.94 [95% CI (1585.35, 1769.58)], respectively. The adjusted GMT ratio of NBP608 to the comparator was 0.80 [95% CI (0.75, 0.87)]. There was no statistically significant difference between two groups in terms of the geometric mean spot numbers determined by IFN-γ and IL-2 ELISPOT assays at 6 weeks post vaccination (P = 0.7232, 0.3844). The incidence of adverse events (AEs) within 6 weeks post vaccination was 49.82% overall (410/823, 941 cases), 50.73% (209/412, 474 cases) in the NBP608 group, and 48.91% (201/411, 467 cases) in the comparator group. The difference in AE rate between the two groups was not statistically significant (P = 0.6010). Most AEs were mild, with a rate of 83.12% in the NBP608 group and 75.37% in the comparator group. Thus, NBP608 is non-inferior to Zostavax® in terms of inducing the immune response and can be safely administered to adults aged 50 years or older. ClinicalTrials.gov Identifier: NCT03120364.

Comparison of pyogenic postoperative and native vertebral osteomyelitis

BACKGROUND CONTEXT

Postoperative vertebral osteomyelitis (PVO) after spinal surgery is a clinical challenge. However, there is a paucity of evidence regarding the most likely etiologic organisms to guide the choice of empirical antibiotic therapy, and previous reports of treatment outcomes for PVO are scarce.

PURPOSE

To compare the microbiology, clinical characteristics, and outcomes of pyogenic PVO with native vertebral osteomyelitis (NVO).

STUDY DESIGN

Retrospective comparative study.

PATIENT SAMPLE

Patients with microbiologically proven vertebral osteomyelitis from three university-affiliated hospitals in South Korea between January 2005 and December 2015 with follow-up of at least 12 months after completion of antibiotics or until the patient was transferred. Patients who had a spine operation in the same location within 1 year of diagnosis, and all patients with remnant implants at the time of the vertebral osteomyelitis diagnosis, were defined as having PVO. The remainder of the patients was considered to have NVO. Spinal operations included discectomy, laminectomy, arthrodesis, and instrumentation for stabilization of the spine.

OUTCOME MEASURES

Overall mortality, neurologic outcomes, treatment failure, and relapse of infection.

METHODS

Demographic data, comorbidities, presenting symptoms, microbiological data, radiographic characteristics, laboratory data (including white blood cell counts, erythrocyte sedimentation rate, and C-reactive protein), surgical treatment, and neurologic outcomes for each patient were reviewed from electronic medical records and analyzed. Mortality rate, treatment failure, and relapse of infection were calculated for the two groups. Factors associated with treatment outcome were evaluated using univariate and multivariate logistic regression analyses.

RESULTS

The study evaluated 104 patients with PVO and 441 patients with NVO. In PVO, the most common isolate was Staphylococcus aureus (34%, n=35), followed by coagulase-negative staphylococci (31%, n=32). In NVO, the most common isolates were S. aureus (47%, n=206) and streptococci (21%, n=94). Of the staphylococci, the proportion of methicillin-resistant strains was significantly higher in PVO than that in NVO (75% vs. 39%, p<.001). The proportion of patients with gram-negative bacilli was 14% in PVO and 20% in NVO. Pre-existing or synchronous nonspinal infection was observed more frequently in NVO than in PVO (33% vs. 13%, p<.001). Although the duration of antibiotic use was similar in both groups, surgery for infection control was performed more frequently in PVO. The mortality rate was similar in both groups. However, the treatment failure and relapse rates at 12 months were higher in the PVO group (23% vs. 13%, p=.009; 14% vs. 7%, p=.028, respectively). Methicillin-resistant S.aureus was significantly associated with treatment failure or relapse via logistic regression (odds ratio 3.01, 95% confidence interval [1.71-5.32], p<.001; odds ratio 2.78, 95% confidence interval [1.40-5.49], p=.003).

CONCLUSIONS

Coverage of methicillin-resistant staphylococci should be considered when prescribing empirical antibiotics for PVO. Although surgery was performed more often in PVO than NVO, the treatment failure and relapse rates at 12 months were higher in PVO.

Moderate hearing loss is related with social frailty in a community-dwelling older adults: The Korean Frailty and Aging Cohort Study (KFACS)

OBJECTIVES

To determine whether hearing loss is associated with social frailty in older adults.

METHODS

Cross-sectional analysis of cohort study data. Hearing was measured using of Pure-tone audiometry. Hearing loss was determined based on the average of hearing thresholds at 0.5, 1, and 2 kHz in the ear that had better hearing. Social frailty was defined based on the summation of the following 5 social components (1. Neighborhood meeting attendance 2. Talking to friend(s) sometimes 3.Someone gives you love and affection 4. Living alone 5. Meeting someone every day). Participants who had no correspondence to the components were considered non-social frailty; those with 1-2 components were considered social prefrailty; and those having 3 or more components were considered social frailty.

RESULTS

The prevalence of non-social frailty, social prefrailty, social frailty was 27.6%, 60.7% and 11.7% respectively. Of the five questions, two components (Neighborhood meeting attendance and Presence of someone who shows love and affection to the participants) were associated with hearing loss (p < 0.001). Compared to non-social frailty, the odds ratio of social frailty for hearing loss was 2.24 (95% CI 1.48-3.38) after adjusting for age, residential area, economic status, smoking, depressive disorder and MMSE, and 2.17 (95% CI 1.43-3.30) after further adjustments with physical frailty.

CONCLUSION

Hearing loss was associated with social frailty even after controlling confounding factors even including physical frailty.

Severe fever with thrombocytopenia syndrome: comparison with scrub typhus and clinical diagnostic prediction

Background

Severe fever with thrombocytopenia syndrome (SFTS) is emerging in Asian 3 countries, China, Japan and Korea, which are scrub typhus endemic areas, and its incidence is increasing. As the two infections overlap epidemiologically and clinically and the accessibility or sensitivity of diagnostic tests is limited, early clinical prediction may be useful for diagnostic and therapeutic purposes.

Methods

Patients aged ≥16 years who were clinically suspected and laboratory-confirmed to be infected with Orientia tsutsugamushi or the SFTS virus in South Korea were enrolled. Clinical and laboratory parameters were compared. Scrub typhus was further subclassified according to the status of eschar and skin rash. An SFTS prediction scoring tool was generated based on a logistic regression analysis of SFTS compared with scrub typhus.

Results

The analysis was performed on 255 patients with scrub typhus and 107 patients with SFTS. At initial presentation, subjective symptoms except for gastrointestinal symptoms, were more prominent in scrub typhus patients. In addition to the characteristic eschar and skin rash, headache was significantly more prominent in scrub typhus, while laboratory abnormalities were more prominent in SFTS. Leukopenia (white blood cell count < 4000/mm³; odds ratio [OR] 30.13), thrombocytopenia (platelet count < 80,000 /mm³; OR 19.73) and low C-reactive protein (< 1 mg/dL; OR 67.46) were consistent risk factors for SFTS (all P < 0.001). A prediction score was generated using these 3 variables, and a score ≥ 2 had a sensitivity of 93.1% (95% confidence interval [CI], 87.9–96.4%) and a specificity of 96.1% (95% CI, 93.8–97.6%) for SFTS.

Conclusion

This prediction scoring tool may be useful for differentiating SFTS from eschar- or skin rash-negative scrub typhus. It is a simple and readily applicable tool with potential for use in primary care settings.

294. Spondylodiscitis After Spine Surgery: Microbiology, Clinical Findings, Outcome and Comparison With Spontaneous Spondylodiscitis

Background

Although postoperative spondylodiscitis has become a major problem, consensus on empirical antibiotics therapy is still controversial. To find out appropriate management of postoperative spondyodiscitis, this study investigated the microbiology, clinical characteristics, and outcome of postoperative pyogenic spondylodiscitis (P-PS) and compared with spontaneous pyogenic spondylodiscitis (S-PS).

Methods

This retrospective cohort study evaluated patients with microbiologically proven spondylodiscitis from three university-affiliated hospitals in South Korea between January 2005 and December 2015, with a follow-up of at least 12 months after completion of antibiotics or until the patient was transferred. Patients with prosthesis at the time of diagnosis of spondylodiscitis or who had a spine operation within 1 year of the diagnosis of spondylodiscitis were defined as having postoperative spondylodiscitis. The spine operations included discectomy, laminectomy, arthrodesis, and instrumentation for stabilization of the spine.

Results

The study evaluated 104 patients with P-PS and 441 patients with S-PS. In P-PS, the most common isolate was S. aureus (34%), followed by coagulase-negative staphylococci (31%), and the proportion of methicillin-resistant strains was 75%. In S-PS, the most common isolates were S. aureus (47%) and streptococci (21%). Of the staphylococci, 39% were methicillin resistant in S-PS. The proportion of patients with Gram-negative bacilli was 14% in P-PS and 20% in S-PS. Pre-existing or synchronous nonspinal infection (13% vs. 33%, P < 0.001) was observed more frequently in S-PS. Although the duration of antibiotic use was similar in both groups, surgical procedures were done more frequently in P-PS. The mortality rate was similar in both groups. However, the treatment failure and relapse rates at 12 months were higher in the P-PS group (23% vs. 13%, P = 0.009; 14% vs. 7%, P = 0.028, respectively). Methicillin-resistant S. aureus was associated with treatment failure or relapse.

Conclusion

Gram-positive organisms, mainly methicillin-resistant staphylococci, should be considered when prescribing empirical antibiotics in P-PS. Although surgical drainage was applied more often in P-PS than in S-PS, the treatment failure and relapse rates at the 12-month follow-up were higher in P-PS.

Disclosures

All authors: No reported disclosures.

1053. Biofilm Production and Clinical Characteristics of S. maltophilia Causing Persistent or Relapsing Bacteremia

Background

This study aimed to identify clinical or microbiological factors related to persistence or recurrence of Stenotrophomonas maltophilia bacteremia in adult patients.

Methods

S. maltophilia isolated from blood in two tertiary hospitals between 2011 and 2017 were investigated. Persistent bacteremia was defined as the consecutive blood culture positive for ≥5 days after initiation of appropriate antibiotics therapy. Relapse was defined as isolation of S. maltophilia from blood after completion of antibiotics treatment for the first episode of bacteremia. Biofilm formation was assessed in 96-well polystyrene plate with Trypticase Soy Broth using 0.5% crystal violet staining. The presence of smf-1 gene was detected by polymerase chain reaction.

Results

Of total 100 patients with S. maltophilia bacteremia, 10 of persistent, 8 of relapsing, and 46 of nonpersistent, nonrelapsing cases were investigated. The presence of indwelling urinary catheter (P = 0.011), nasogastric tube (P = 0.003), mechanical ventilator treatment (P = 0.001), and previous colonization of S. maltophilia (P = 0.016) were more frequently observed in patients with persistent bacteremia compared with nonpersistent, nonrelapsing bacteremia cases. In patients with relapsing bacteremia, hematologic malignancy (P = 0.022), neutropenia (P = 0.001), and concomitant isolation of S. maltophilia in clinical samples other than blood (P = 0.041) were more common than nonpersistent, nonrelapsing bacteremia patients. Catheter-related infection (37.0%) followed by pneumonia (28.3%) was the most common primary focus of nonpersistent, nonrelapsing bacteremia whereas pneumonia was the most frequent cause of bacteremia in both of persistent and relapsing cases (40.0% and 50.0%). Most of isolates (63 of 64) were susceptible to cotrimoxazole. The resistance to levofloxacin were comparable among isolates from persistent, relapsing and nonpersistent, nonrelapsing cases (10.0% vs. 12.5% vs. 15.2%, P = 0.988). Biofilm formation ability was not significantly different between three groups (optical density at 595, mean ± SD, 0.69 ± 0.34 vs. 0.78 ± 0.33 vs. 0.70 ± 0.33, P = 0.529). The smf-1 gene was found in all isolates.

Conclusion

More careful treatment approaches to patients with risk factors for S.maltophilia treatment failure should be warranted.

Disclosures

All authors: No reported disclosures.

Case report: dual primary AIDS-defining cancers in an HIV-infected patient receiving antiretroviral therapy: Burkitt's lymphoma and Kaposi's sarcoma

BACKGROUND

The incidence of AIDS-defining cancers (ADCs) has decreased markedly in the era of highly active antiretroviral therapy (HAART). The occurrence of two ADCs is rare in people living with HIV or AIDS (PWHA) who are severely immunosuppressed or have incomplete virologic suppression.

CASE PRESENTATION

We report a case of dual primary ADCs, especially NHL followed by KS, in a 70-year-old HIV-infected man who was on antiretroviral therapy and had successful virologic suppression. During HAART, he presented with generalized myalgia and abdominal pain. Multiple liver masses were detected and a biopsy revealed Burkitt's lymphoma. After three cycles of anticancer chemotherapy with a favorable response, he was diagnosed with cytomegalovirus retinitis and the anti-cancer chemotherapy was discontinued. Despite successful virologic suppression with HAART, human herpes virus-8 associated Kaposi's sarcoma was diagnosed in his right thigh. He underwent radiation therapy.

CONCLUSION

These findings suggest that multiple ADCs can occur in PWHA who are receiving HAART and have successful virologic suppression. Healthcare providers caring for PWHA should maintain vigilance for the development of a broad spectrum of cancers.

Inoculum effect of methicillin-susceptible Staphylococcus aureus against broad-spectrum beta-lactam antibiotics

Scarce information concerning the inoculum effect (InE) of methicillin-susceptible Staphylococcus aureus (MSSA) against broad-spectrum β-lactam antibiotics is available. We investigated the InE of MSSA against ceftriaxone, cefepime, meropenem, ampicillin/sulbactam and piperacillin/tazobactam. The bacteraemic MSSA isolates were collected at ten Korean general hospitals from Sep 2013 to Mar 2015. The InE was defined if MICs of antibiotics at high inoculum (HI, ~5 × 10⁷ CFU/ml) increased beyond the susceptible range compared to those at standard inoculum (SI, ~5 × 10⁵ CFU/ml). All isolates were sequenced for blaZ gene typing. Among 302 MSSA isolates, 254 (84.1%) were positive for blaZ; types A, B, C and D were 13.6%, 26.8%, 43.4% and 0.3%, respectively. Mean HI MICs of all tested antibiotics were significantly increased and increases in HI MIC of piperacillin/tazobactam (HI, 48.14 ± 4.08 vs. SI, 2.04 ± 0.08 mg/L, p < 0.001) and ampicillin/sulbactam (HI, 24.15 ± 1.27 vs. SI, 2.79 ± 0.11 mg/L, p < 0.001) were most prominent. No MSSA isolates exhibited meropenem InE, and few isolates exhibited cefepime (0.3%) and ceftriaxone (2.3%) InE, whereas 43.0% and 65.9% of MSSA isolates exhibited piperacillin/tazobactam and ampicillin/sulbactam InE, respectively. About 93% of type C blaZ versus 45% of non-type C exhibited ampicillin/sulbactam InE (p < 0.001) and 88% of type C blaZ versus 9% of non-type C exhibited piperacillin/tazobactam InE (p < 0.001). A large proportion of MSSA clinical isolates, especially those positive for type C blaZ, showed marked ampicillin/sulbactam InE and piperacillin/tazobactam.

Factors affecting the clinical relevance of Corynebacterium striatum isolated from blood cultures

This study aimed to identify clinical or microbiological factors affecting the clinical relevance of Corynebacterium striatum isolated from blood cultures. A total of 64 isolates from 51 patients identified as C. striatum by matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and 16S rRNA gene sequencing were assessed. More than two blood cultures were positive in 25 (48.1%) patients. Diabetes, solid tumor, and a history of previous exposure to antibiotics were more common in patients with multiple positive blood cultures. Charlson comorbidity scores were also higher, and more isolates were recovered after 48 hours of hospital stay in patients with multiple positive blood cultures. Strains recovered from patients with multiple positive blood cultures produced significantly more biofilm. Based on multilocus sequence typing (MLST), sequence type (ST) 20 (31.3%) was the most dominant, followed by ST2 (20.3%) and ST23 (10.9%). There was no relationship between the number of positive blood culture sets and sequence typing. In multivariate analyses, Carlson comorbidity score (odds ratio [OR], 1.91; 95% confidence interval [CI], 1.09–3.36; P = 0.03) and biofilm formation were associated with multiple positive blood cultures (OR, 17.43; 95% CI, 3.71–81.91; P = 0.03). This study provides evidence that the biofilm phenotype could contribute to determining the clinical significance of C. striatum in patients with severe underlying conditions. The predominance of certain STs suggests the relatedness of C. striatum infection and the nosocomial environment.

Case report: detection of the identical virus in a patient presenting with severe fever with thrombocytopenia syndrome encephalopathy and the tick that bit her

Background

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne disease. Haemophysalis longicornis ticks have been considered the vector of severe fever with thrombocytopenia syndrome virus (SFTSV). However, clear data on the transmission of SFTS from ticks to humans are limited.

Case presentation

We report an 84-year-old woman who presented with fever and altered mentality, which was confirmed as SFTS with encephalopathy by reverse-transcription polymerase chain reaction in blood and cerebrospinal fluid. The SFTSV was also identified in the tick that bit her, H. longicornis. Phylogenetic analyses indicated that the SFTSV from the patient and the tick was identical. The patient gradually recovered with treatments of corticosteroids and immunoglobulin.

Conclusion

These findings provide further evidence of SFTS viral transmission from H. longicornis to human.

A Risk-Scoring System for Predicting Methicillin Resistance in Community-Onset Staphylococcus aureus Bacteremia in Korea

AIMS

We aimed to develop a simple scoring system to predict risk for methicillin resistance in community-onset Staphylococcus aureus bacteremia (CO-SAB) by identifying the clinical and epidemiological risk factors for community-onset methicillin-resistant S. aureus (MRSA).

METHODS

We retrospectively analyzed data from three multicenter cohort studies in Korea in which patient information was prospectively collected and risk factors for methicillin resistance in CO-SAB were identified. We then developed and validated a risk-scoring system.

RESULTS

To analyze the 1,802 cases of CO-SAB, we included the four most powerful predictors of methicillin resistance that we identified in the scoring system: underlying hematologic disease (-1 point), endovascular infection as the primary site of infection (-1 point), history of hospitalization or surgery in ≤1 year (+0.5 points), and previous isolation of MRSA in ≤6 months (+1.5 points). With this scoring system, cases were classified into low (less than -0.5), intermediate (-0.5-1.5), and high (≥1.5) risk groups. The proportions of MRSA cases in each group were 24.7% (22/89), 39.0% (607/1,557), and 78.8% (123/156), respectively, and 16.7% (1/6), 33.8% (112/331), and 76.9% (10/13) in a validation set.

CONCLUSIONS

This risk-scoring system for methicillin resistance in CO-SAB may help physicians select appropriate empirical antibiotics more quickly.

EuroQol Visual Analogue Scale (EQ-VAS) as a Predicting Tool for Frailty in Older Korean Adults: The Korean Frailty an Aging Cohort Study (KFACS)

OBJECTIVES

This study was conducted to determine the cutoff value and efficacy of the EuroQol Visual Analogue Scale (EQ-VAS) for predicting frailty.

DESIGN

The EQ-VAS medians (Interquartile Range) were compared and analyzed against the FFI.

PARTICIPANTS

The subjects were 1471 older adults aged 70 to 84 years who had completed both EQ-VAS and Fried Frailty index (FFI) in the first baseline year (2016) of the Korean Frailty and Aging Cohort Study.

RESULTS

Of the 1471 subjects,600 were classified as robust, 716 as pre-frail, and 155 as frail. The median EQ-VAS scores were 80.00 (20.00) for robust, 75.00 (25.00) for pre-frail, and 60.00 (25.00) for frail subjects.The medians of all five components of the FFI, weight loss (70.00 vs. 80.00), grip strength (70.00 vs. 80.00), exhaustion (70.00 vs. 80.00), walking velocity (70.00 vs. 80.00), and physical activity (70.00 vs. 80.00), were lower in the abnormal groups. We tested the efficacy of EQ-VAS as a diagnostic tool to predict frailty, and the area under the curve of EQ-VAS was 0.71 withthe optimal cut-off value of 72.

CONCLUSION

EQ-VAS presented negative correlation with FFI, and the optimal cut off value for frailty was 72. These results suggest that EQ-VAS is a valuable tool for assessing frailty andmay be a good predictor of frailty in Korean elderly population.

Incidence and risk factors of postoperative pneumonia following cancer surgery in adult patients with selected solid cancer: results of "Cancer POP" study

The aim of this study was to investigate the incidence and risk factors of postoperative pneumonia (POP) within 1 year after cancer surgery in patients with the five most common cancers (gastric, colorectal, lung, breast cancer, and hepatocellular carcinoma [HCC]) in South Korea. This was a multicenter and retrospective cohort study performed at five nationwide cancer centers. The number of cancer patients in each center was allocated by the proportion of cancer surgery. Adult patients were randomly selected according to the allocated number, among those who underwent cancer surgery from January to December 2014 within 6 months after diagnosis of cancer. One‐year cumulative incidence of POP was estimated using Kaplan–Meier analysis. An univariable Cox's proportional hazard regression analysis was performed to identify risk factors for POP development. As a multivariable analysis, confounders were adjusted using multiple Cox's PH regression model. Among the total 2000 patients, the numbers of patients with gastric cancer, colorectal cancer, lung cancer, breast cancer, and HCC were 497 (25%), 525 (26%), 277 (14%), 552 (28%), and 149 (7%), respectively. Overall, the 1‐year cumulative incidence of POP was 2.0% (95% CI, 1.4–2.6). The 1‐year cumulative incidences in each cancer were as follows: lung 8.0%, gastric 1.8%, colorectal 1.0%, HCC 0.7%, and breast 0.4%. In multivariable analysis, older age, higher Charlson comorbidity index (CCI) score, ulcer disease, history of pneumonia, and smoking were related with POP development. In conclusions, the 1‐year cumulative incidence of POP in the five most common cancers was 2%. Older age, higher CCI scores, smoker, ulcer disease, and previous pneumonia history increased the risk of POP development in cancer patients.

Emergence of Daptomycin-Nonsusceptible Methicillin-Resistant Staphylococcus aureus Clinical Isolates Among Daptomycin-Naive Patients in Korea

This study was conducted to assess emergence of daptomycin-nonsusceptible (DAP-NS) phenotype in DAP-naive patients with invasive Staphylococcus aureus (ISA) infections in Korea. A total of 208 S. aureus clinical isolates were selected from a previous prospective study on ISA infections and evaluated for DAP-NS. Although DAP has never been introduced in Korea, five DAP-NS S. aureus strains (2.4%) were identified among 208 S. aureus strains collected from ISA infections. The DAP-NS phenotype was observed only in methicillin-resistant S. aureus (MRSA) strains, but not in methicillin-susceptible S. aureus strains. One DAP-NS MRSA strain belonged to sequence type 72 (ST72) and four were ST5 MRSA strains, three of which were heteroresistant vancomycin (VAN)-intermediate S. aureus. All these five DAP-NS MRSA strains were from healthcare-associated infections without prior exposure to VAN within 30 days. While the ST72 MRSA strain exhibited DAP-NS phenotype via charge repulsion mechanism, four ST5 DAP-NS S. aureus strains had charge-independent DAP-NS mechanism. None of the five DAP-NS strains displayed significant increase in cell wall thickness, indicating that altered cell wall thickness was not associated with the observed DAP-NS phenotype.

In Vivo Efficacy of Tigecycline-based Therapy Against Vibrio vulnificus Sepsis: Comparison with pre-Existing Regimens

Background

The mortality of Vibrio vulnificus sepsis is still high, despite the application of various antibiotic regimens. In-vivo efficacy of tigecycline against V. vulnificus has not been examined.

Methods

Time-kill assay was performed to evaluate the presence of in-vitro antibiotic synergism. The cytotoxicity of V. vulnificus was measured by using the lactate dehydrogenase assay, and rtxA1 toxin gene transcription was measured by β-galactosidase assay. Subcutaneous injection of V. vulnificus was performed with 1 × 10⁸ CFU on iron-overloaded female BALB/c mouse, then intraperitoneal antibiotic therapy was initiated 2 hours after bacterial inoculation.

Results

In vitro time-kill assay reveals synergism between tigecycline and ciprofloxacin. Inhibitory effects of tigecycline on rtx A1 transcription (66%) and cytotoxicity (59%) were comparable to those of ciprofloxacin (64% and 53%), but superior to those of minocycline (76% and 69%) or cefotaxime (86% and 83%; P < 0.05, each). Survival of tigecycline-treated mice were significantly higher than those of mice treated by current regimens (P < 0.05, each; Table). At Vibrio vulnificus sepsis mice inoculating 1 × 10⁹ CFU, survival rate for tigecycline-plus-ciprofloxacin was significantly higher than that of tigecycline (0%; 0/19) or tigecycline-plus-cefotaxime (0%; 0/19) (P < 0.05, each; Table).

Conclusion

Tigecycline-plus-ciprofloxacin showed superior in-vivo efficacy to pre-existing regimens.

Disclosures

All authors: No reported disclosures.

Active surveillance for carbapenem-resistant Acinetobacter baumannii in a medical intensive care unit: Can it predict and reduce subsequent infections and the use of colistin?

BACKGROUND

Infection caused by carbapenem-resistant Acinetobacter baumannii (CRAB) has become a major problem in intensive care units (ICUs), with high incidence and mortality. This prospective study investigated the diagnostic value and influence of active surveillance, followed by isolation and enhanced contact precaution (IECP), on the subsequent CRAB infection and colistin use.

METHODS

The study prospectively enrolled 1,115 patients who were admitted to the medical ICU of Chonnam National University Hwasun Hospital between April 2011 and November 2014. Active surveillance cultures were obtained from the throat or trachea, skin, and urine. IECP was performed beginning April 2013.

RESULTS

Active surveillance detected CRAB in 168 (15%) patients and CRAB infection developed in 70 (6%) patients. Endotracheal tube was independently associated with both CRAB colonization and infection, whereas IECP was inversely associated with both CRAB colonization and infection in multivariate analysis (all P values <.001). The sensitivity, specificity, and positive and negative predictive values of active surveillance for subsequent CRAB infection were 84%, 90%, 47%, and 98%, respectively. The rate of CRAB acquisition, CRAB infection, and the use of colistin were significantly lower during the IECP period compared with the control period (6.5 vs 34.1, 2.6 vs 14.7, and 19.9 vs 65.5 per 1,000 patient-days, respectively; all P <.001).

CONCLUSIONS

Active surveillance has good specificity and negative predictive value for subsequent CRAB infection. Active surveillance followed by IECP was inversely associated with the acquisition of CRAB and subsequent CRAB infection, and was associated with a reduction in colistin use in ICU patients.

Severe Fever with Thrombocytopenia Syndrome in South Korea, 2013-2015

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease that was recently identified in China, South Korea and Japan. The objective of the study was to evaluate the epidemiologic and clinical characteristics of SFTS in South Korea.

METHODS/PRINCIPAL FINDINGS

SFTS is a reportable disease in South Korea. We included all SFTS cases reported to the Korea Centers for Disease Control and Prevention (KCDC) from January 2013 to December 2015. Clinical information was gathered by reviewing medical records, and epidemiologic characteristics were analyzed using both KCDC surveillance data and patient medical records. Risk factors for mortality in patients with SFTS were assessed. A total of 172 SFTS cases were reported during the study period. SFTS occurred throughout the country, except in urban areas. Hilly areas in the eastern and southeastern regions and Jeju island (incidence, 1.26 cases /105 person-years) were the main endemic areas. The yearly incidence increased from 36 cases in 2013 to 81 cases in 2015. Most cases occurred from May to October. The overall case fatality ratio was 32.6%. The clinical progression was similar to the 3 phases reported in China: fever, multi-organ dysfunction, and convalescence. Confusion, elevated C-reactive protein, and prolonged activated partial thromboplastin times were associated with mortality in patients with SFTS. Two outbreaks of nosocomial SFTS transmission were observed.

CONCLUSIONS

SFTS is an endemic disease in South Korea, with a nationwide distribution and a high case-fatality ratio. Confusion, elevated levels of C-reactive protein, and prolonged activated partial thromboplastin times were associated with mortality in patients with SFTS.

Surveillance of the Middle East respiratory syndrome (MERS) coronavirus (CoV) infection in healthcare workers after contact with confirmed MERS patients: incidence and risk factors of MERS-CoV seropositivity

Given the mode of transmission of Middle East respiratory syndrome (MERS), healthcare workers (HCWs) in contact with MERS patients are expected to be at risk of MERS infections. We evaluated the prevalence of MERS coronavirus (CoV) immunoglobulin (Ig) G in HCWs exposed to MERS patients and calculated the incidence of MERS-affected cases in HCWs. We enrolled HCWs from hospitals where confirmed MERS patients had visited. Serum was collected 4 to 6 weeks after the last contact with a confirmed MERS patient. We performed an enzyme-linked immunosorbent assay (ELISA) to screen for the presence of MERS-CoV IgG and an indirect immunofluorescence test (IIFT) to confirm MERS-CoV IgG. We used a questionnaire to collect information regarding the exposure. We calculated the incidence of MERS-affected cases by dividing the sum of PCR-confirmed and serology-confirmed cases by the number of exposed HCWs in participating hospitals. In total, 1169 HCWs in 31 hospitals had contact with 114 MERS patients, and among the HCWs, 15 were PCR-confirmed MERS cases in study hospitals. Serologic analysis was performed for 737 participants. ELISA was positive in five participants and borderline for seven. IIFT was positive for two (0.3%) of these 12 participants. Among the participants who did not use appropriate personal protective equipment (PPE), seropositivity was 0.7% (2/294) compared to 0% (0/443) in cases with appropriate PPE use. The incidence of MERS infection in HCWs was 1.5% (17/1169). The seroprevalence of MERS-CoV IgG among HCWs was higher among participants who did not use appropriate PPE.