Multi-modality detection of SARS-CoV-2 in faecal donor samples for transplantation and in asymptomatic emergency surgical admissions.

Faecal transplantation is an evidence-based treatment for . Patients infected with SARS-CoV-2 have been shown to shed the virus in stool for up to 33 days, well beyond the average clearance time for upper respiratory tract shedding. We carried out an analytical and clinical validation of reverse-transcriptase quantitative (RT-qPCR) as well as LAMP, LamPORE and droplet digital PCR in the detection of SARS-CoV-2 RNA in stool from donated samples for faecal microbiota transplantation (FMT), spiked samples and asymptomatic inpatients in an acute surgical unit.

Distribution of the partitioning protein KorB on the genome of IncP-1 plasmid RK2.

The ParB family partitioning protein, KorB, of plasmid RK2 is central to a regulatory network coordinating replication, maintenance and transfer genes. Previous immunofluorescence microscopy indicated that the majority of KorB is localized in plasmid foci. The 12 identified KorB binding sites on RK2 are differentiated by: position relative to promoters; binding strength; and cooperativity with other repressors and so the distribution of KorB may be sequestered around a sub-set of sites.

Flexibility in repression and cooperativity by KorB of broad host range IncP-1 plasmid RK2.

KorB, encoded by plasmid RK2, belongs to the ParB family of active partitioning proteins. It binds to 12 operators on the RK2 genome and was previously known to repress promoters immediately adjacent to operators O(B)1, O(B)10 and O(B)12 (proximal) or up to 154 bp away (distal) from O(B)2, O(B)9 and O(B)11. To achieve strong repression, KorB requires a cooperative interaction with one of two other plasmid-encoded repressors, KorA or TrbA.

Co-operative interactions control conjugative transfer of broad host-range plasmid RK2: full effect of minor changes in TrbA operator depends on KorB.

A network of circuits, with KorB and TrbA as key regulators, controls genes for conjugative transfer of broad host range plasmid RK2. To assess the importance of the TrbA regulon, mutational analysis was applied to the TrbA operator at the trbB promoter and then to other TrbA-regulated promoters in the tra region. All identified TrbA operators are submaximal; in the case of trbBp, a G to A transition that made the operator core a perfect palindrome increased repression by about 50% compared to the wild type.