Early detection of community acquired of SARS-CoV-2 lineage B.1.351 in Hong Kong.

Background: Prior to this report, variants of concern for SARS-CoV-2 were only detected from imported cases in Hong Kong. Objective: Multiple cases of SARS-CoV-2 lineage B.1.351 have been identified in local community. We reported the phylogenetic relationship of these cases. Study design: SARS-CoV-2 cases were screened for the key non-synonymous substitutions in spike protein by different assays. Preliminary positive cases were further tested by whole genome sequencing. Results: From Dec 2020 to May 2021, 55 SARS-CoV-2 cases belonged to lineage B.1.351. Among them, eight genomes were clustered together, all of them were local cases with epidemiological link. Conclusions: To track variants of SARS-CoV-2 and to allow early implementation of control measures, SARS-CoV-2 genomic surveillance must be consistently performed.

Genetic and phenotypic characterization of drug-resistant Mycobacterium tuberculosis isolates in Hong Kong.

OBJECTIVES: To characterize 250 drug-resistant Mycobacterium tuberculosis (MTB) isolates in Hong Kong with respect to their drug susceptibility phenotypes to five common anti-tuberculosis drugs (ofloxacin, rifampicin, ethambutol, isoniazid and pyrazinamide) and the relationship between such phenotypes and the patterns of genetic mutations in the corresponding resistance genes (gyrA, rpoB, embB, katG, inhA, ahpC and pncA). METHODS: The MIC values of the aforementioned anti-tuberculosis drugs were determined for each of the 250 drug-resistant MTB clinical isolates by the absolute concentration method. Genetic mutations in the corresponding resistance genes in these MTB isolates were identified by PCR-single-stranded conformation polymorphism/multiplex PCR amplimer conformation analysis (SSCP/MPAC), followed by DNA sequencing of the purified PCR products. RESULTS: Resistance to four or five drugs was commonly observed in these MTB isolates; such phenotypes accounted for over 34% of the 250 isolates. The most frequently observed phenotypes were those involving both rifampicin and isoniazid, with or without additional resistance to the other drugs. A total of 102 novel mutations, which accounted for 80% of all mutation types detected in the 7 resistance genes, were recovered. Correlation between phenotypic and mutational data showed that genetic changes in the gyrA, rpoB and katG genes were more consistently associated with a significant resistance phenotype. Despite this, however, a considerable proportion of resistant MTB isolates were found to harbour no detectable mutations in the corresponding gene loci. CONCLUSIONS: These findings expand the spectrum of potential resistance-related mutations in MTB clinical isolates and help consolidate the framework for the development of molecular methods for delineating the drug susceptibility profiles of MTB isolates in clinical laboratories.

Routine use of a simple low-cost genotypic assay for the identification of mycobacteria in a high throughput laboratory.

A novel polymerase chain reaction (PCR)-restriction fragment length polymorphism analysis (PRA) of the hsp65 gene was used for the routine identification of mycobacteria in a high throughput clinical laboratory. A total of 2036 clinical isolates were tested by PRA in conjunction with other methods. The PRA identification of M. tuberculosis complex was 100% sensitive and specific, and 74.5% of nontuberculous mycobacteria (NTM) were correctly identified. It gave highly consistent results for Mycobacterium avium complex (MAC) species and for most isolates of M. fortuitum, M. chelonae, and M. kansasii. It had proven to be highly robust and stable despite usage on such a large-scale and is thus particularly suitable for use in high throughput laboratories in areas with a high incidence of tuberculosis.