Sunjoo Kim
Ann Clin Microbiol 2023 December, 26(4):89-97. Published on 20 December 2023.
Group A streptococci (GAS) cause diverse diseases ranging from mild to severe illnesses, and the global burden of GAS infections is enormous. Serological typing has been replaced by emm genotyping for the epidemiological study of GAS. Acute bacterial pharyngitis is a common illness, which requires either throat culture or rapid Ag test for diagnosis. Moreover, molecular point-of-care tests have been introduced owing to their higher sensitivity. Optimal diagnosis of bacterial pharyngitis is necessary for the adequate use of antibiotics. Although antimicrobial resistance (AMR) to erythromycin or clindamycin does not seem serious in Korea, it is very high in China, being reported at over 90%. Antibiotic surveillance and relevant education are necessary for primary clinical physicians and pediatricians. It is necessary to monitor AMR and develop a system for reporting the appearance of highly virulent diseases, such as necrotizing fasciitis or streptococcal toxic-shock syndrome, to the government authority.
Soo-Kyung Kim
Ann Clin Microbiol 2023 December, 26(4):99-102. Published on 20 December 2023.
On October 4, 2023, the Nobel Prize in Chemistry was awarded to Moungi Bawendi, Louis Brus, and Aleksey Yekimov for the discovery and synthesis of quantum dots (QDs). The Nobel Foundation credited QDs as being the “seeds of nanoscience”. As suggested by its name, QDs are extremely small matter resembling a dot. A QD is a photoluminescent nanoparticle composed of semiconductor materials with diameters ranging between 2 and 10 nm. It often consists of only a few thousand atoms and are smaller than human cells and viruses.
Sang Shin Pyo, Dae Wui Yoon, Hyunjung Kim, Hiun Suk Chae, Hae Kyung Lee
Ann Clin Microbiol 2023 December, 26(4):103-115. Published on 20 December 2023.
Background: Early prediction of bacteremia is important because sepsis may develop if bacteremia is not treated in time. We aimed to determine whether blood tests are clinically useful in predicting gram-negative versus gram-positive bacteremia.
Methods: We retrospectively analyzed the medical records of 16,569 patients who underwent blood culture testing among those who visited St. Mary’s Hospital of Uijeongbu, Catholic University from January 1, 2018 to December 31, 2018. After excluding 15,580 patients with insufficient data for analysis, the total study population was 989.
Results: In the multivariable logistic regression analysis for gram-negative bacteremia, after adjusting for major variables, procalcitonin (odds ratio [OR] 1.02, P < 0.001), high-sensitivity C-reactive protein (OR 1.03, P = 0.010), and albumin (OR 0.55, P = 0.010) were significant. In the same model, lactic acid (OR 1.08, P = 0.010), blood urea nitrogen (BUN) (OR 1.02, P = 0.010), and albumin (OR 0.50, P = 0.005) were significant for gram-positive bacteremia. We constructed blood indicators by combining blood tests that were significant in multivariable logistic regression analysis. Comparing the area under the curve (AUC) of the receiver operating characteristic curve, the AUC of the procalcitonin/albumin ratio in gramnegative bacteremia was significantly higher than that of procalcitonin (0.846 vs. 0.837, P = 0.005), and the AUC of the BUN/albumin ratio in gram-positive bacteremia was significantly higher than that of BUN (0.709 vs. 0.679, P = 0.007).
Conclusion: The procalcitonin/albumin ratio is expected to be helpful in the early prediction of gram-negative bacteremia, whereas the BUN/albumin ratio in the early prediction of gram-positive bacteremia.
Kuenyoul Park, Mi-Na Kim, Heungsup Sung
Ann Clin Microbiol 2023 December, 26(4):117-124. Published on 20 December 2023.
Background: This study aimed to evaluate the efficacy of three medical detergents against bacteria and yeast-derived biofilms.
Methods: The biofilm removal efficacy of EmpowerTM (Metrex, USA), CidezymeTM (Johnson and Johnson Medical Inc, USA), and Matrix mintTM (Whiteley Medical, Australia) were compared to that of chlorine bleach. Biofilms were produced using Staphylococcus aureus RN9120, Escherichia coli ATCC35218, Pseudomonas aeruginosa ATCC27853, Candida albicans ATCC14053, and clinical isolates of Enterococcus faecalis, E. coli, Klebsiella pneumoniae, Candida auris, and Trichosporon asahii. The organisms were suspended in tryptic soy broth (TSB) in 96-well microplates and cultured for 72 hours. They were treated with the detergents, and the residual biofilm mass was quantified using crystal violet staining followed by optical density measurements at 620 nm (OD620).
Results: EmpowerTM and CidezymeTM significantly reduced the biofilm mass derived from all species by > 50% of OD620 at 37ºC except those from E. faecalis, T. asahii, and C. auris. Matrix mintTM had no effect on the biofilms under any condition.
Conclusion: The culture conditions and the species of the biofilm-producing organism influenced the effectiveness of the detergent. Biofilms produced by E. faecalis, C. auris, and T. asahii were resistant to all detergent treatments under all conditions.
Jiyeon Kim, Heungsup Sung, Mi-Na Kim
Ann Clin Microbiol 2023 December, 26(4):125-137. Published on 20 December 2023.
Background: Blood culture (BC) systems have evolved to increase sensitivity and reduce turnaround times. This study compared the performance of a 4-day versus a 5-day BC incubation period using the BD BACTEC™ FX (Becton, Dickinson and Company, USA).
Methods: A total of 37,379 consecutive sets of BC were evaluated over a 3-month period in a 2,700-bed tertiary care hospital. Positive BC results were reviewed to assess time-to-positivity (TTP) and species identification of the isolates. The BCs were performed in pairs of vials, utilizing either BD BACTEC Plus Aerobic/F or Peds Plus/F with BD BACTEC Lytic Anaerobic media.
Results: A total of 14,899 episodes, averaging 2.51 sets per episode, were analyzed. Of these, 1,398 (9.38%) were positive, yielding 1,465 isolates. TTP (hours) were < 12 in 48.87%, 12-24 in 31.40%, 24-48 in 13.38%, 48-72 in 3.28%, 72-96 in 1.43%, and >96 in 1.64%. The two most prevalent organisms, Escherichia coli and Klebsiella spp. were detected within 12 hours in 88.75% and 78.90%, respectively. The respective median TTP (T50) values for E. coli, Klebsiella spp., Enterococcus faecalis/E. faecium, and Staphylococcus aureus were 9.24, 9.60, 13.75, and 14.20. T50 values for these species were significantly shorter in anaerobic bottles than in aerobic bottles. Of 24 BCs with TTP > 96, only 4 containing anaerobic bacteria or molds were f irst detected after 96 hours.
Conclusion: A 4-day incubation has demonstrated excellent sensitivity. However, a 5-day incubation may be beneficial for hospitals caring for patients at high risk for infections with slow-growing fungi or fastidious bacteria.
Chang-Ki Kim, Hee Jae Huh, Jeong Su Park, Taesoung Kim, Jae Han Sohn
Ann Clin Microbiol 2023 December, 26(4):139-145. Published on 20 December 2023.
Background: Rifampin plays an important role in tuberculosis treatment. In recent years, the introduction of molecular testing techniques has enabled the rapid detection of rifampin resistance, leading to discrepancies with conventional methods. The World Health Organization (WHO) has analyzed mutations in the rpoB gene that induce rifampin resistance and identified certain mutations causing borderline resistance, which are often undetected using conventional tests. Consequently, the WHO has lowered the rifampin resistance criterion concentration from 1.0 to 0.5 μg/mL in 7H10 and MGIT 960. The present study aimed to evaluate the impact of this change in critical concentration on the detection of borderline rifampin resistance in Mycobacterium tuberculosis.
Methods: Tuberculosis strains submitted for antituberculosis drug susceptibility testing from May 2021–2022 were analyzed. Three institutions participated; the Seoul Clinical Laboratories used the agar proportion method, whereas the Samsung Medical Center and Seoul National University Bundang Hospital utilized the MGIT 960 system to test both the original and revised concentrations. Mutations were confirmed through rpoB gene sequencing for strains showing discrepancies.
Results: A total of 1,596 valid susceptibility tests were conducted during the study period. Rifampin resistance was detected in 35 cases (2.19%) at 1.0 μg/mL and in 38 cases (2.38%) at 0.5 μg/mL, whereas isoniazid resistance was observed in 158 cases (9.90%). Among the three rifampin discrepancy strains, one harbored an H445L mutation, whereas the remaining two exhibited an L452P mutation. These mutations were classified as borderline resistant.
Conclusion: Applying the new rifampin critical concentration resulted in a 0.19% increase in resistance rate and an 8.57% increase in detection cases. Additionally, despite testing with large number of rifampin-susceptible strains, no false resistance results were obtained. Therefore, the application of the new critical concentration is considered beneficial for the management of rifampin-resistant tuberculosis.
Yiel Hea Seo, Daewon Kim, Hwan Tae Lee, Ja Young Seo, Jeong Yeal Ahn, Pil Whan Park
Ann Clin Microbiol 2023 December, 26(4):147-157. Published on 20 December 2023.
Background: The distribution of bacteria isolated from bloodstream infections and cumulative antimicrobial susceptibility data are the basis for empirical decisions regarding antibiotics as an initial treatment. Therefore, it is important to consistently collect blood culture results of individual patients and analyze them correctly.
Methods: The blood culture results of patients at Gachon University Gil Medical Center from 2016 to 2020 were analyzed retrospectively to determine the bacterial distributions and antibiotic resistance patterns. Duplicates were eliminated by including only the first isolate of each species per patient.
Results: Escherichia coli (27.1%) was the most commonly isolated bacterium from blood cultures, followed by Klebsiella pneumoniae (10.1%) and Staphylococcus aureus (8.6%). The methicillin resistance rate of S. aureus was 49.2%, and the vancomycin resistance rate of Enterococcus faecium was 39.5%; with no significant changes over the study period. The cefotaxime, ciprofloxacin, and ertapenem resistance rates of E. coli were 35.0%, 46.8%, and 0.7%, respectively. Seventeen carbapenem-resistant E. coli strains were isolated, of which 11 produced carbapenemase. The cefotaxime, ciprofloxacin, and ertapenem resistance rates of K. pneumoniae were 29.5%, 31.7%, and 5.4%, respectively. Forty-eight carbapenem-resistant K. pneumoniae strains were isolated, of which 37 produced carbapenemase. The imipenem resistance rates of Acinetobacter baumannii and Pseudomonas aeruginosa were 72.3% and 23.4%, respectively.
Conclusion: In the blood culture results from 2016 to 2020, the isolation frequency of E. coli, K. pneumoniae, and E. faecium showed an increasing trend, whereas that of S. aureus was stable. Over the 5 year study period, the ciprofloxacin resistance rate of E. coli and P. aeruginosa and ampicillin/sulbactam resistance rate of A. baumannii significantly increased.
[in Korean]
Hae-Sun Chung
Ann Clin Microbiol 2023 December, 26(4):159-163. Published on 20 December 2023.
We conducted environmental cultures for carbapenemase-producing Enterobacterales (CPE) to evaluate the environmental contamination around patients with CPE. CPE was detected in the environmental cultures of four of the nine intensive care unit (ICU) inpatients with CPE. All four isolates were collected from sink surfaces in isolation rooms within the ICU. CPE isolates from the environment differed from those isolated from patients and had different carbapenemases. Even though CPE isolates from the environment of the ICU were not associated with CPE isolates from patients, the repeated isolation of CPE from sinks over several months is alarming.
Eun Jeong Won , Min Jae Kim, Jina Lee, Hyery Kim, Heungsup Sung, Mi-Na Kim
Ann Clin Microbiol 2023 December, 26(4):165-169. Published on 20 December 2023.
Human taeniasis is presumed to have almost disappeared from Korea. Recently, we incidentally detected a Taenia saginata infection in an 8-year-old boy undergoing lymphoma diagnosis. The patient had been suffering for 4 months from intensifying snoring and obstructive sleep apnea. A neck computed tomography scan revealed a nasopharyngeal mass, and malignant B-cell lymphoma was supported by punch biopsy. On day 6 of the lymphoma workup period, the patient experienced anal itching, and two proglottids were detected in his stool. The patient had experienced four or five similar episodes within the past 2 years. He self-reported a history of raw beef and fish consumption and no history of traveling abroad. Laboratory findings revealed mild eosinophilia (eosinophil count: 791/μL). Two proglottids exhibited movement and possessed more than 15 branched uterine structures. Long segments approximately 84 cm in length were expelled after praziquantel treatment. Sequencing of the cytochrome oxidase 1 gene confirmed T. saginata, ruling out related Taenia species. After treatment, no proglottids or ova were detected in his stool, and the patient finally started chemotherapy for lymphoma. This case highlights the importance of timely diagnosis of hidden taeniasis in low-frequency endemic regions.
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