Optimized bacterial absolute quantification method by qPCR using an exogenous bacterial culture as a normalization strategy in triple-species BV-like biofilms.

Quantitative Polymerase Chain Reaction (qPCR) is a widely used method in molecular biology to quantify target DNA sequences. Despite its accuracy, there are important experimental controls that should be considered to avoid biased results. One of them is gDNA loss during extraction, which is higher among samples with lower bacterial concentrations. Improvement in qPCR quantification procedures is mandatory to obtain reproducible and accurate results. Herein, we report an improved qPCR method for bacterial quantification of Gardnerella vaginalis, Prevotella bivia, and Fannyhessea vaginae, three key-bacterial vaginosis (BV)-associated bacteria (BVAB) thought to play important roles in the pathogenesis of this common vaginal infection. The formation of a mature biofilm on vaginal epithelial cells is an unique feature of BV and, despite over 60 years of research, the exact etiology of BV remains unknown. Here, we optimized a qPCR method that accurately quantified triple-species biofilms containing these key BVAB, after the addition of an exogenous bacterial control containing a fixed concentration of Escherichia coli, prior to gDNA extraction. This improved method minimized and normalized the inherent losses associated with bacterial centrifugation, which allows better sensitivity at lower bacterial concentrations.

COVID-19-associated arthritis: an emerging new entity?

The current COVID-19 pandemic raises several clinical challenges. Cases of COVID-19-associated arthritis have been reported, and inconsistently described as either COVID-19 viral arthritis or COVID-19 reactive arthritis. We aimed to review all the reported cases of 'COVID-19-associated arthritis', which we propose, is a better term to define the entire spectrum of new-onset arthritis believed to be associated with SARS-CoV-2 infection. We performed a systematic literature review using MEDLINE, EMBASE and the Cochrane Database of Systematic Reviews to search for articles published up to 13 December 2021. We included cohort studies, case series and case reports describing patients diagnosed with COVID-19 reactive or viral arthritis by a physician, irrespective of fulfilment of classification criteria. To identify relevant studies, medical subject headings and keywords related to 'COVID-19/SARS-CoV-2 infection' and 'reactive arthritis' were used. Our search retrieved 419 articles, of which 31 were included in the review. A total of 33 cases were reported in these 31 articles, the majority being adults (28/33=85%) with peripheral joint involvement (26/33=79%). Most of the patients responded well to treatment and the disease was self-limiting. These 33 case reports describe a possible causal relationship between exposure to SARS-CoV-2 and the onset of arthritis. However, since these cases were reported during a pandemic, other aetiologies cannot be fully excluded. The exact mechanism through which SARS-CoV-2 might trigger arthritis is not fully understood and robust epidemiological data to support a causal relationship are still lacking.