Seungjun Lee

We analyzed the accuracy and time efficiency of the FilmArray blood culture identification (FA-BCID) panel in identifying the pathogens in positive blood cultures. Two-hundred and seventy-two individuals were randomly assigned as the control (n = 212) and FA-BCID (n = 60) groups participating in this study. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to assess the control group. Meanwhile, the FA-BCID group was evaluated using both FA-BCID and MALDI-TOF, and the results were compared. The identification results from 73% (44/60) of the blood samples demonstrated agreement between FA-BCID and MALDI-TOF. The FA-BCID panel detected mecA genes in seven Staphylococcus species; six cases were confirmed using antimicrobial susceptibility testing. In addition, KPC genes were detected in one Escherichia coli and one Klebsiella pneumoniae, although only the latter corresponded with the result from antimicrobial susceptibility testing. The turnaround time (TAT) for identification through FA-BCID was shorter, with a median of 3.6 [2.4–4.6] hours (p < 0.05). No significant differences in the clinical and microbial outcomes following the ASP were observed between FA-BCID and MALDI-TOF. These results suggest that the FA-BCID panel provides an identification result that is as reliable as that provided by the routine identification procedure but with shorter TAT; thus, the FA-BCID method is considered an effective and beneficial method for therapeutic decision making and the improvement of the ASP for patients with bloodstream infection.

Objective: We aimed to compare the adaptive immune response in individuals with or without prior SARS-CoV-2 infections following the administration of mRNA-based COVID-19 vaccines. Methods: A total of 54 participants with ages ranging from 37 to 56 years old, consisting of 23 individuals without a history of SARS-CoV-2 infection (uninfected group) and 31 individuals with prior infection of SARS-CoV-2 (infected group) who have received two doses of mRNA SARS-CoV-2 vaccines were enrolled in this study. We measured the IFN-γ level upon administration of BNT162b2 (PF) or mRNA-1273 (MO) by QuantiFERON SARS-CoV-2. The production of neutralizing antibodies was evaluated by a surrogate virus neutralization assay, and the neutralizing capacity was assessed by a plaque reduction neutralization test (PRNT₅₀). The immune response was compared between the two groups. Results: A significantly higher level of IFN-γ (p < 0.001) and neutralization antibodies (p < 0.001) were observed in the infected group than those in the uninfected group following the first administration of vaccines. The infected group demonstrated a significantly higher PRNT₅₀ titer than the uninfected group against the Wuhan strain (p < 0.0001). Still, the two groups were not significantly different against Delta (p = 0.07) and Omicron (p = 0.14) variants. Following the second vaccine dose, T- and B-cell levels were not significantly increased in the infected group. Conclusion: A single dose of mRNA-based COVID-19 vaccines would boost immune responses in individuals who had previously contracted SARS-CoV-2.

Hyoshim Shin, M.D., Takashi Takahashi, M.D., Ph.D., Seungjun Lee, M.D., Eun Hwa Choi, M.D., Ph.D., Takahiro Maeda, B.P., Yasuto Fukushima, B.P., and Sunjoo Kim, M.D., Ph.D.. Ann Lab Med 2022;42:438-46. https://doi.org/10.3343/alm.2022.42.4.438

Background: Surveillance and control of SARS‐CoV‐2 outbreak through gold standard detection, that is, real‐time polymerase chain reaction (RT‐PCR), become a great obstacle, especially in overwhelming outbreaks. In this study, we aimed to analyze the performance of rapid antigen home test (RAHT) as an alternative detection method compared with RT‐PCR.Methods: In total, 79 COVID‐19‐positive and 217 COVID‐19‐negative patients confirmed by RT‐PCR were enrolled in this study. A duration from symptom onset to COVID‐19 confirmation of 25 (p‐value = 0.01).Conclusion: The RAHT showed an excellent sensitivity for COVID‐19‐confirmed cases, especially for those with symptoms. There was a decrease in sensitivity when the Ct value is over 25, indicating that RAHT screening may be useful during the early phase of symptom onset, when the viral numbers are higher and it is more transmissible.

The rapid diagnosis of SARS-CoV-2 is an essential aspect in the detection and control of the spread of COVID-19. We evaluated the accuracy of the rapid antigen test (RAT) using samples from the nasal cavity and nasopharynx based on sample collection timing and viral load. We enrolled 175 patients, of which 71 patients and 104 patients had tested positive and negative, respectively, based on real time-PCR. Nasal cavity and nasopharyngeal swab samples were tested using STANDARD Q COVID-19 Ag tests (Q Ag, SD Biosensor, Korea). The sensitivity of the Q Ag test was 77.5% (95% confidence interval [CI], 67.8–87.2%) for the nasal cavity and 81.7% (95% [CI, 72.7–90.7%) for the nasopharyngeal specimens. The RAT results showed a substantial agreement between the nasal cavity and nasopharyngeal specimens (Cohen’s kappa index = 0.78). The sensitivity of the RAT for nasal cavity specimens exceeded 89% for E and RdRp < 25. The Q Ag test performed fairly well, especially in the early DSO when a high viral load was present, and the nasal cavity swab can be considered an alternative site for the rapid diagnosis of COVID-19.

Background: Group A streptococcus (GAS) is the most common cause of bacterial pharyngitis. This study aimed to characterize the molecular epidemiology of GAS infection using an emmtyping and emm-clustering approach. Methods: A total of 372 patients from Changwon who showed pharyngitis symptoms were recruited during the sampling period of 2018–2019 and throat cultures were obtained from them. emm typing was performed using polymerase chain reaction (PCR) and direct sequencing. emm genotypes and GAS clusters were classified based on a web-based database. Results: Of the 372 throat swab specimens, 101 (27.2%) were positive for GAS. emm typing analysis was performed on 59 GAS isolates. The most prevalent emm type was emm89 (20.3%), followed by emm12 (16.9%). Seven emm clusters were identified: E4 (emm89/ emm28, 32.2%), A-C4 (emm12, 16.9%), E1 (emm4, 13.6%), A-C5 (emm3, 10.2%), E6 (emm75, 8.5%), M6 (emm6, 8.5%), and A-C3 (emm1, 6.8%). Conclusion: Diverse and temporal changes were observed in the distribution of emm types and clusters of GAS. Continuous surveillance based on emm genotyping is needed to monitor the epidemiological characteristics of GAS pharyngitis.

Background: Blood culture is essential for diagnosis of sepsis. However, usually the available blood volume is not sufficient to meet the guidelines. Thus, periodic monitoring and feedback are essential to improve the quality of blood cultures. Methods: We analyzed blood cultures requested between November 2018 and June 2019, and provided educational intervention and coaching for phlebotomists at the end of February 2019. Then, we evaluated the impact of education on blood cultures in a secondary‑care hospital. Blood volume, positive rate, contamination rate, and time to detection (TTD) were compared between the pre‑ (November 2018 to February, 2019) and post‑intervention periods (March to June, 2019). Results: The average blood volume increased significantly from 5.4 mL to 7.1 mL (P < 0.0001) (35.2%) after intervention. Accordingly, the proportion of optimal blood volume (8–12 mL) increased from 9.1% to 37.8% (P < 0.0001). Before the intervention, the positivity rate was 9.6% and the contamination rate was 0.5%, whereas after the intervention, the positivity rate decreased to 9.1% and the contamination rate increased to 1.1%. TTD improved from 14.7 hours to 13.1 hours (P = 0.0420). Conclusion: The educational intervention of the phlebotomy team improved the quality of blood cultures, especially blood volumes and TTD. However, the positivity rate did not increase, suggesting that it is affected not only by the blood volumes but also by the severity of the underlying illnesses of the patient in a secondary‑care hospital.

Background: Pharyngitis is one of the most common conditions encountered in primary health care facilities. Accurate differentiation of group A streptococcus (GAS) infection from viral infection is difficult. The STANDARD F Strep A Ag FIA (SD BIOSENSOR, Korea) is a rapid antigen detection test (RADT) that has been recently developed for diagnosing GAS pharyngitis. In this study, we evaluated the diagnostic performance of the STANDARD F Strep A Ag FIA and compared the results between the RADT and conventional throat culture. Methods: Throat swab samples were obtained from a total of 372 children presenting pharyngitis symptoms in five pediatric clinics in Changwon, Korea from July 2018 to October 2019. A comparative study between STANDARD F Strep A Ag FIA and Sofia Strep A FIA (Quidel, USA) was performed. Two throat swabs were taken simultaneously from each patient for RADT. The third throat swab was stored in a transport tube containing Stuart’s transport medium for culture. Performance and kappa index of STANDARD F Strep A Ag FIA were evaluated. Results: GAS infection was detected in 29.3% (109/372) patients, using the STANDARD F Strep A Ag FIA. The sensitivity, specificity, positive predictive value, and negative predictive value were 95.0%, 95.2%, 88.1%, and 98.1%, respectively. The STANDARD F Strep A Ag FIA showed an excellent concordance rate of 96.5% and a kappa value of 0.89 compared to Sofia Strep A FIA. Conclusion: The STANDARD F Strep A Ag FIA demonstrated an excellent performance along with Sofia Strep A FIA for the diagnosis of GAS pharyngitis.

Takashi Takahashi, M.D., Ph.D., Takahiro Maeda, B.P., Seungjun Lee, M.D., Dong-Hyun Lee, M.D., and Sunjoo Kim, M.D., Ph.D.. Ann Lab Med 2020;40:370-81. https://doi.org/10.3343/alm.2020.40.5.370