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Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The Spike protein that mediates coronavirus entry into host cells is a major target for COVID-19 vaccines and antibody therapeutics. However, multiple variants of SARS-CoV-2 have emerged, which may potentially compromise vaccine effectiveness. Using a pseudovirus-based assay, we evaluated SARS-CoV-2 cell entry mediated by the viral Spike B.1.617 and B.1.1.7 variants. We also compared the neutralization ability of monoclonal antibodies from convalescent sera and neutralizing antibodies (NAbs) elicited by CoronaVac (inactivated vaccine) and ZF2001 (RBD-subunit vaccine) against B.1.617 and B.1.1.7 variants. Our results showed that, compared to D614G and B.1.1.7 variants, B.1.617 shows enhanced viral entry and membrane fusion, as well as more resistant to antibody neutralization. These findings have important implications for understanding viral infectivity and for immunization policy against SARS-CoV-2 variants.

This paper focuses on biofilms of Lactobacillus spp. - a type of normal flora isolated from healthy human vaginas of women of childbearing age; thereupon, it broadens the research scope of investigation of vaginal normal flora. The static slide culture method was adopted to foster biofilms, marked by specific fluorescence staining. Laser scanning confocal and scanning electron microscopy were used to observe the microstructure of the biofilms. Photographs taken from the microstructure were analysed to calculate the density of the biofilms. The body of Lactobacillus spp., though red, turned yellow when interacting with the green extracellular polysaccharides. The structure of the biofilm and aquaporin within the biofilm were imaged. Lactobacillus density increases over time. This study provides convincing evidence that Lactobacillus can form biofilms and grow over time in vitro. This finding establishes an important and necessary condition for selecting proper strains for the pharmaceutics of vaginal ecology.

The qacA/B genes are found in Staphylococcus aureus and confer resistance to various antiseptics and disinfectants. Herein, the prevalence of the qacA/B genes in methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) was investigated. Molecular typing systems were used to analyse the relatedness of these qacA/B-positive strains. 176 six strains of clinically isolated S. aureus were collected between July, 2008 and June, 2010. The strains carrying the qacA/B genes were characterised by pulse-field gel electrophoresis (PFGE) typing, Staphylococcus protein A (spa) typing, Panton-Valentine leucocidin (pvl) polymerase chain reaction (PCR) detection, staphylococcal chromosomal cassette (SCC) mec typing, and antimicrobial resistance profiles. Strains carrying the qacA/B genes composed 9.1% of the strains isolated, but the incidence of qacA/B genes in MRSA strains was significantly higher than that in MSSA strains (14.6 versus 4.3%, p < 0.05). Additionally, two predominant PFGE (B and A) and spa types (t037 and t042) were identified along with two major antimicrobial resistance profiles. All of these qacA/B-positive strains strains were pvl-negative by PCR. The qacA/B-positive MRSA strains all contained the group III SCCmec element. These strains were obtained mainly from patients in surgical wards; therefore, the neurosurgical ward and ICU may be considered as a source of MRSA strains carrying the qacA/B genes. Finally, the strain identified as spa type t037 is likely to be an epidemiological clone. The presence of the antiseptic resistance genes qacA/B by MRSA could potentially lead to MRSA strain prevalence. Thus, the optimal usage of antiseptics and disinfectants is warranted. A policy of molecular typing needs to be implemented to track the possible dissemination of these resistance genes. Key words : Staphylococcus aureus, mecA, qacA/B and pvl genes, methicillin-resistant, Staphylococcus aureus (MRSA), methicillin-sensitive Staphylococcus aureus (MSSA).