Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology


Weeks in Review


Weeks to Publication
Indexed in KCI, KoreaMed, Synapse, DOAJ
Open Access, Peer Reviewed
pISSN 2288-0585 eISSN 2288-6850

December, 2020. Vol. 23 No. 4.


Experience at Department of Laboratory Medicine during the COVID-19 Outbreak in Daegu

Sunggyun Park, Do-Hoon Kim, Won-Mok Lee, Jung-Sook Ha, Dong-Seok Jeon, Jae-Hee Lee, Namhee Ryoo

Ann Clin Microbiol 2020 December, 23(4): 225-231. Published on 20 December 2020.

The first case of coronavirus disease 2019 (COVID-19) in Korea was reported in January 2020. As the secondary transmissions accelerated within the country, the government revised the outbreak alert for COVID-19 from attention to caution. Mid-February, when a massive outbreak was reported from a church in Daegu, our institution initiated testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). More than 300 laboratory tests were performed within the first 2 months, before the number of cases began to decline. Here, we describe our experience of 4 months at the department of Laboratory Medicine, Keimyung University Dongsan Hospital, located in Daegu, where a massive COVID-19 outbreak occurred.

[in Korean]

Original article

Cross-Correlation Analysis of the Incidence of Multidrug-Resistant Organisms with Hand Hygiene Compliance and Effectiveness of Alcohol-Gel Hand Hygiene Practice

Eun-Hwa Baek, Se-Eun Kim, Da-Hye Kim, Sunjoo Kim

Ann Clin Microbiol 2020 December, 23(4): 233-239. Published on 20 December 2020.

Background: Multidrug- resistant organisms (MDRO) are a serious concern in healthcare-associated infections. Hand hygiene (HH) is essential to prevent the spread of MDRO in the healthcare institutes. The aim of this study was to investigate the relationship between the incidence of MDRO and hand hygiene compliance and the experimental effectiveness of alcohol-gel hand hygiene practice.

Methods: From March 2016 to September 2018, we analyzed the cross-correlation between the incidence of MDRO and the HH compliance each month at Gyeongsang National University Changwon Hospital. We employed an experiment to observe the effect of alcohol gel hand hygiene practice on the reduction of organisms on the hand surface using the handagar plates.

Results: Among the MDRO, only vancomycin-resistant enterococci (VRE) showed a moderate correlation with the HH rate (r = 0.55). The hand-agar plate experiment showed a significant bacterial reduction for inadequate HH (mean 3.47 CFU) and optimal HH (mean, 0.84 CFU) than before HH (mean, 11.56 CFU) (n = 32, P = 0.006).

Conclusion: The incidence of VRE showed a moderate correlation with HH among MDRO in the longitudinal analysis. HH practice was more effective in preventing the spread of VRE compared with other MDRO in our institute. Optimal alcohol-gel HH practice can effectively remove bacteria on the hand surface.

Original article

The Trend of Clostridioides difficile Infection in Korean Hospitals with the Analysis of Nationwide Sample Cohort

Kang Ju Son, Young Ah Kim, Yoon Soo Park

Ann Clin Microbiol 2020 December, 23(4): 241-249. Published on 20 December 2020.

Background: Clostridioides (Clostridium) difficile is an important pathogen that causes diarrhea in people who take antibiotics. The recent status of C. difficile infection is not wellknown in Korea.

Methods: The long-term trend of C. difficile infection in Korean hospitals was analyzed using a nationwide sample cohort. The data also included sociodemographic characteristics, disease severity, and healthcare facilities. C. difficile infection was defined by the prescription of oral vancomycin or all metronidazole prescriptions under C. difficile infectious disease code (A047).

Results: The rate of C. difficile infection has steadily increased from 0.030% in 2006 to 0.317% in 2015. The increased rate correlated to age (0.033% for <50 years, 0.421% for 70-79 years, and 0.758% for >80 years of age) and the Charlson comorbidity index score (0.048% for zero versus 0.378% for three or more points). It differed by the type of medical institution (0.270 % at referral hospitals versus 0.056 % at general hospitals and mental hospitals).

Conclusion: The rate of C. difficile infection in Korea is significant in patients with advanced age and disease severity. The results show that C. difficile infection trend has been increasing steadily in Korea.

Original article

Causes and Clinical Relevance of Inconclusive SARS-CoV-2 Real-Time Reverse TranscriptionPCR Test Results

Aram Kim, Heerah Lee, Kyu Wha Hur, Heungsup Sung, Mi-Na Kim

Ann Clin Microbiol 2020 December, 23(4): 251-259. Published on 20 December 2020.

Background: Inconclusive SARS-CoV-2 real-time reverse transcription-PCR (rRT-PCR) test results, which are positive for one or more target genes but not all, are problematic in clinical laboratories. In this study, we aimed to investigate the cause and clinical relevance of such inconclusive results.

Methods: rRT-PCR was performed using the Allplex 2019-nCoV assay kit (Seegene Inc., Korea) targeting the following three genes: E, RdRp, and N. For all inconclusive test results reported from March to June 2020, the frequency per kit, lot number, specimen type, cycle threshold (Ct) and peak values of the amplification curves, positive target genes, and results of repeated or consecutive tests were analyzed.

Results: A total of 43,268 tests were conducted, of which 93 (0.21%) were inconclusive—49 from 11 coronavirus disease 2019 (COVID-19) patients and 44 from non-COVID-19 patients. In COVID-19 patients, the results were inconclusive 11.9 ± 4.7 days after diagnosis and were negative 8.8 ± 5.5 days after the inconclusive results were reported. However, in non-COVID-19 patients, they were all negative upon retest and 81.8% of them were identified to have yielded in 2 out of 8 lots. The most frequently positive target genes were N (55.4%) in COVID-19 and RdRp (61.2%) in non-COVID-19 patients, respectively. No difference was observed in the Ct or peak values of the amplification curves for inconclusive samples between COVID-19 and non-COVID-19 cases.

Conclusion: Inconclusive test results should be reported neither positive nor negative. Such results can be reported as inconclusive without retesting in COVID-19 patients; however, they should certainly be confirmed by a retest in non-COVID-19 patients or newly diagnosed cases.

Original article

Evaluating the Use of Distilled Water for Washing Sodium Hydroxide in Mycobacterial Culture

Hae-Gyeong Baek, Hyun-Mi Ko, Myung-Hee Lee

Ann Clin Microbiol 2020 December, 23(4): 261-270. Published on 20 December 2020.

Background: Respiratory specimens subjected to mycobacterial detection were initially pre-treated with N-acetyl-L-cysteine-sodium hydroxide (NALC-NaOH) to remove the mucus and normal flora. Next, they were washed and neutralized with phosphate-buffered solution (PBS). The effectiveness of distilled water (DW) compared to PBS as a washing neutralizer during identification of mycobacteria was evaluated in this study.

Methods: We analyzed the results of mycobacterial test conducted at a general hospital in Gwangju from October 2016 to September 2018. PBS and DW were used as a respiratory sample washing agent for one year each.

Results: The positive culture rate for the culture of mycobacteria was 12.7% (1,843/14,532) and 14.7% (2,095/14,291), when PBS and DW were used, respectively. The recovery rate of the mycobacteria growth indicator tubes (MGIT) and the separation rates of Mycobacterium tuberculosis complex and nontuberculous mycobacteria (NTM) showed no significant change. However, in 2% Ogawa medium, as the NTM culture increased from 47.4% (399/841) to 56.1% (630/1,122), the recovery rate increased from 45.6% (841/1,843) to 53.6% (1,122/2,095). The MGIT contamination rate decreased from 6.5% to 4.1%.

Conclusion: DW as a washing agent for NALC-NaOH increased the recovery rate of Ogawa media and reduced the contamination rate of MGIT. Therefore, use of DW instead of PBS as a washing neutralizer during identification of mycobacteria might be useful.

[in Korean]

Case report

A Case of Prosthetic Valve Endocarditis with Cerebral Hemorrhage Caused by Rothia mucilaginosa

Yeo-Jin Song, Bongyoung Kim, Young-eun Kim, Yangsoon Lee, Hyunjoo Pai

Ann Clin Microbiol 2020 December, 23(4): 271-276. Published on 20 December 2020.

Rothia spp. are aerobic, gram-positive cocci belonging to the family Micrococcaceae, and are a part of the normal microbial flora of the human oropharynx and upper respiratory tract. We present the first case of the prosthetic valve endocarditis with cerebral hemorrhage caused by Rothia mucilaginosa in South Korea. A 65-year-old man with a prosthetic aortic valve visited the outpatient clinic with a complaint of fever. R. mucilaginosa was identified in one among four sets of blood culture bottles obtained on the on day 30 of fever onset. Brain magnetic resonance imaging (MRI) showed multiple micro-hemorrhages suggesting septic emboli in both the hemispheres, corticomedullary junctions, and cerebellum. Rothia spp. should be considered as a possible pathogen in the cases of infective endocarditis with intracranial hemorrhage.