A regional genomic surveillance program is implemented to monitor the occurrence and emergence of SARS-CoV-2 variants in Yubei District, China.

BACKGROUND: In December 2022, Chongqing experienced a significant surge in coronavirus disease 2019 (COVID-19) epidemic after adjusting control measures in China. Given the widespread immunization of the population with the BA.5 variant, it is crucial to actively monitor severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant evolution in Chongqing's Yubei district. METHODS: In this retrospective study based on whole genome sequencing, we collected oropharyngeal and nasal swab of native COVID-19 cases from Yubei district between January to May 2023, along with imported cases from January 2022 to January 2023. Through second-generation sequencing, we generated a total of 578 genomes. RESULTS: Phylogenetic analyses revealed these genomes belong to 47 SARS-CoV-2 Pango lineages. BA.5.2.48 was dominant from January to April 2023, rapidly replaced by XBB* variants from April to May 2023. Bayesian Skyline Plot reconstructions indicated a higher evolutionary rate (6.973 × 10-4 subs/site/year) for the XBB.1.5* lineage compared to others. The mean time to the most recent common ancestor (tMRCA) of BA.5.2.48* closely matched BA.2.75* (May 27, 2022). Using multinomial logistic regression, we estimated growth advantages, with XBB.1.9.1 showing the highest growth advantage (1.2, 95% HPI:1.1-1.2), followed by lineage FR.1 (1.1, 95% HPI:1.1-1.2). CONCLUSIONS: Our monitoring reveals the rapid replacement of the previously prevalent BA.5.2.48 variant by XBB and its sub-variants, underscoring the ineffectiveness of herd immunity and breakthrough BA.5 infections against XBB variants. Given the ongoing evolutionary pressure, sustaining a SARS-CoV-2 genomic surveillance program is imperative.

[Studies of the factors linked to the bacteriostatic ability of Lactobacillus in human vagina].

OBJECTIVE: To study the factors linked to the bacteriostatic ability of Lactobacillus in human vagina, and the relationship between the Lactobacillus and the Candida albicans. METHODS: The content of H2O2, in the upper culture mediums of Lactobacilli were detected at different incubation time. Selecting the strains with vary bacteriostatic ability by Oxford cup test, detecting pH of these strains cultured after different time. After co-cultivation of the Lactobacillus, which has the strongest bacteriostatic ability, Candida albicans and Staphylococci for different incubation time, quantities of these mixed cultures were investigated. RESULTS: The date of pH and the size of the bacteriostatic ring are negative correlation. There is not obvious relationship between the ability of producing H2O2 and the bacteriostatic ability of Lactobacillus. The study of the relationship between bacteria shows that the quantity of Staphylococci is as this: Staphylococci alone > Staphylococci + Lactobacillus > Staphylococci + Lactobacillus + Candida albicans. CONCLUSION: The bacteriostatic ability of Lactobacillus is positivly related to its acid producing ability, and is not obvious to H2O2 content. After 36 hours cultivation time, Candida albicans can boost up the bacteriostatic ability of Lactobacillus.