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This study investigated resistance mechanisms and epidemiology of emerging linezolid-nonsusceptible Enterococcus faecalis (LNSEF) in a tertiary care hospital. LNSEF isolated from clinical samples were collected from November 2017 to June 2019. The isolates were investigated for linezolid resistance and the associated molecular mechanisms, including mutations of 23S rRNA domain V and acquisition of the cfr or optrA resistance gene. We used pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing for the molecular typing of the isolates. Among 4,318 E. faecalis isolates, 10 (0.23%) were linezolid-nonsusceptible. All LNSEF isolates were optrA-positive and cfr-negative. Of these isolates, five were sequence type (ST) 476, two ST585, one ST16, one ST16-like, and one ST480. Six LNSEF isolates obtained in the first year clustered to three types in the PFGE analysis: two ST476 isolates of type A, two ST585 isolates of type B, and two ST16 or ST16-like isolates of type C. Seven cases were of community-onset and three were hospital acquired, but total of eight were healthcare-associated including five community-onset. None of the patients had a history of linezolid treatment, and in one patient, we detected linezolid-susceptible E. faecalis one month before LNSEF detection. In conclusion, heterogenous clones of optrA-positive LNSEF emerged in the hospital mainly via community-onset.

SARS-CoV-2 real-time reverse-transcription PCR (rRT-PCR) is the most effective testing system currently available to counter COVID-19 epidemics when potent treatments and vaccines are unavailable. Therefore, four SARS-CoV-2 rRT-PCR kits have been approved by the emergency-use-authorization (EUA) without clinical validation in Korea until March 15, 2020. This study evaluated the analytical and clinical performance of these kits. Allplex 2019-nCoV Real-time PCR (Seegene, Seoul, Korea), PowerChek 2019-nCoV (KogeneBiotech, Seoul), Real-Q 2019-nCoV Real-Time Detection (BioSewoom, Seoul) and StandardM nCoV Detection (SD BIOSENSOR, Osong, Korea) were evaluated. The limit of detection (LODs) of Allplex, PowerChek, and Real-Q was determined by testing the transcribed RNA of SARS-CoV-2 E and the RNA of SARS-CoV Frankfurt1. A total of 27 consecutive samples comprising 13 sputum, 12 nasopharyngeal swab (NPS), 1 urine and 1 stool sample were collected from 2 COVID-19 patients for sensitivity analysis. Precision was assessed via daily tests of positive and negative controls in each kit for 5 d. Reproducibility was examined by repeating 21 samples and 10 fold dilutions of 14 samples in pairs using Allplex. Specificity was evaluated with 24 other respiratory virus-positive samples. LOD of Allplex, PowerChek, and Real-Q were 153.9, 84.1, and 80.6 copies/mL, respectively. The degrees of association between Cts and log viral concentrations by Allplex and PowerChek was expressed as y = -3.319 log (x) + 42.039 (R = 0.96) and y = -3.392 log(x) + 43.113 (R = 0.98), respectively. One or more of the 4 kits detected twenty out of 27 clinical samples positive. Of the 20 positive samples, the detection rates of positives for Allplex, PowerChek, Real-Q, and StandardM were 90.0%, 82.3%, 75.0% and 100.0%, respectively, but those of PowerChek and Real-Q would be 100% if out-of-cutoff Cts were counted as positives. Precision was 100%. Interpretation of Allplex results was reproducible when Ct of E ≤33. All 4 kits showed no cross-reactivity with other respiratory viruses. Performance of the 4 kits indicated the suitability of these for diagnosis and follow-up testing of COVID-19. Laboratory doctors who initially implement these EUA kits must be able to interpret quality control parameters.

This study investigated resistance mechanisms and epidemiology of emerging linezolid-nonsusceptible Enterococcus faecalis (LNSEF) in a tertiary care hospital. LNSEF isolated from clinical samples were collected from November 2017 to June 2019. The isolates were investigated for linezolid resistance and the associated molecular mechanisms, including mutations of 23S rRNA domain V and acquisition of the cfr or optrA resistance gene. We used pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing for the molecular typing of the isolates. Among 4,318 E. faecalis isolates, 10 (0.23%) were linezolid-nonsusceptible. All LNSEF isolates were optrA-positive and cfr-negative. Of these isolates, five were sequence type (ST) 476, two ST585, one ST16, one ST16-like, and one ST480. Six LNSEF isolates obtained in the first year clustered to three types in the PFGE analysis: two ST476 isolates of type A, two ST585 isolates of type B, and two ST16 or ST16-like isolates of type C. Seven cases were of community-onset and three were hospital acquired, but total of eight were healthcare-associated including five community-onset. None of the patients had a history of linezolid treatment, and in one patient, we detected linezolid-susceptible E. faecalis one month before LNSEF detection. In conclusion, heterogenous clones of optrA-positive LNSEF emerged in the hospital mainly via community-onset.

A 52-year-old woman with relapsed acute lymphoblastic leukemia was diagnosed with Mycobacterium massiliense pneumonia after 4 months of chemotherapy. She developed M. massiliense bacteremia 1 month later. This is the first report of a proven case of M. massiliense bacteremia as a consequence of M. massiliense pneumonia.

The iNtRON vancomycin-resistant enterococci (VRE) vanA/vanB real-time PCR assay was directly applied to stool surveillance (direct-PCR). direct-PCR was compared to 2 culture-based methods using Enterococcosel broth (enrichment-culture) and ChromID VRE media. The positive broth of the enrichment-culture was submitted to phenotypic confirmation of subcultured colonies and genotyping by Seeplex VRE PCR. From September 2011 to May 2012, 208 stool specimens from 188 patients previously positive for VRE were enrolled. Enrichment-culture and direct-PCR detected 178 and 158 positives, respectively. Among 129 specimens cultured with ChromID, direct-PCR and ChromID yielded 105 and 104 positives, respectively. Compared to the enrichment-culture, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of direct-PCR and ChromID were 86.0%, 83.3%, 96.8%, 50.0%, and 89.5%, 86.7%, 98.1%, 52.0%, respectively. Considering the excellent PPV and low NPV, direct-PCR would be useful to monitor VRE-colonized or infected patients on the day, but enrichment-culture is required for direct-PCR-negative specimens.