Biology subjects

Clifford, R.

Publications and source records attributed to Clifford, R..

4 recordsLinked to original sources

bioRxiv2022

Characterisation of neonatal Staphylococcus capitis NRCS-A isolates compared with non NRCS-A Staphylococcus capitis from neonates and adults.

Staphylococcus capitis is a frequent cause of Late-Onset Sepsis (LOS) in neonates admitted to Neonatal Intensive Care Units (NICU). The NRCS-A clone of S. capitis has been isolated from NICUs globally although the reasons for the global success of this clone are not understood. We analysed a collection of S. capitis colonising babies admitted to two NICUs, one in the UK and one in Germany as well as corresponding pathological clinical isolates. Genome analysis identified 3 groups; non-NRCS-A isolates, NRCS-A isolates, and a group of proto NRCS-A - isolates closely related to NRCS-A but not associated with neonatal infection. All bloodstream isolates belonged to the NRCS-A group and were indistinguishable from strains carried on the skin or in the gut. NRCS-A isolates showed increased tolerance to chlorhexidine and antibiotics relative to the other S. capitis as well as enhanced ability to grow at higher pH values. Analysis of 138 pangenomes of the clades identified characteristic nsr and tarJ genes in the NRCS-A and proto groups with a CRISPR-cas system only seen in NRCS-A isolates which also showed enrichment of genes for metal acquisition and transport. We found evidence for transmission of S. capitis NRCS-A within NICU, with related isolates shared between babies and multiple acquisitions by some babies. Our data show NRCS-A strains commonly colonise uninfected babies in NICU representing a potential reservoir for potential infection. This work provides more evidence that adaptation to survive in the gut and on skin facilitates spread of NRCS-A, and that metal acquisition and tolerance may be important to the biology of NRCS-A. Understanding how NRCS-A survives in NICUs can help develop infection control procedures against this clone.

genomics↗

bioRxiv2022

Complex genotype-phenotype relationships shape the response to treatment of Down Syndrome Childhood Acute Lymphoblastic Leukaemia

Extensive genetic and epigenetic variegation has been demonstrated in many malignancies. Importantly, their interplay has the potential to contribute to disease progression and treatment resistance. To shed light on the complex relationships between these different sources of intra-tumour heterogeneity, we explored their relative contributions to the evolutionary dynamics of Acute Lymphoblastic Leukemia (ALL) in children with Down syndrome, which has particularly poor prognosis. We quantified the tumour propagating potential of genetically distinct sub-clones using serial transplantation assays and SNP-arrays. While most leukaemias were characterized by a single dominant subclone, others were highly heterogeneous. Importantly, we provide clear and direct evidence that genotypes and phenotypes with functional relevance to leukemic progression and treatment resistance can co-segregate within the disease. Hence, individual genetic lesions can be restricted to well-defined cell immunophenotypes, corresponding to different stages of the leukemic differentiation hierarchy and varied proliferation potentials. As a result of this difference in fitness, which can be accurately quantified via competitive transplantation assays, matching diagnostic, post-treatment, and relapse leukemias can be dominated by different genotypes, including pre-leukemic clones persisting throughout the disease progression and treatment. Intriguingly, plasticity also appears to be a temporally defined property that can segregate with genotype. These results suggest that Down Syndrome ALL should be viewed as a complex matrix of cells exhibiting genetic and epigenetic heterogeneity that foster extensive clonal evolution and competition. Therapeutic intervention reshapes this eco-system and may provide the right conditions for the preferential expansion of selected compartments and subsequently relapse.

cancer biology↗

bioRxiv2021

Known mechanisms account for less than half of antimicrobial resistance in a diverse collection of non-aureus staphylococci.

IntroductionNon-aureus staphylococci (NAS) are implicated in many healthcare-acquired infections and an understanding of the genetics of antimicrobial resistance in NAS is important in relation to both clinical intervention and the role of NAS as a reservoir of resistance genes. Gap statementThe burden of antimicrobial resistance in NAS, particularly to clinically relevant antimicrobials, is under recognised. MethodologyWe sourced 394 NAS isolates from clinical samples, healthy human volunteers, animals and type cultures and subjected them to agar dilution susceptibility testing against eight antimicrobials. Cefoxitin was used to screen for methicillin resistance in S. aureus, as it stimulates expression of mecA. We performed whole genome sequencing on 366 isolates and analysed these genotypically for the presence of genetic mechanisms responsible for the phenotypic levels of reduced antimicrobial susceptibility. ResultsWe observed 175 sequenced isolates with a minimum inhibitory concentration (MIC) of at least 4 g/ml to cefoxitin, of which 50% (87/175) did not harbour a known mec homologue. Eight clinical NAS isolates displayed high daptomycin MICs (>4 g/ml), with no known mechanism identified. Differences in MICs against erythromycin were attributable to the presence of different resistance genes (msrA and ermC). In total, 49% (193 /394) of isolates displayed reduced susceptibility to three or more of the antimicrobials tested. ConclusionsThe widespread presence of reduced antimicrobial susceptibility in NAS is a concern, with an increased likelihood of (1) harder to treat infections caused directly by NAS, and (2) resistance genes being passed on to other bacteria via horizontal gene transfer, both of which have clinical implications for treatment and management of patients.

microbiology↗

bioRxiv2019

The diagnostic chronic lymphocytic leukaemia genome by nanopore sequencing

Chronic lymphocytic leukaemia (CLL) is characterised by considerable clinical and biological heterogeneity, with specific recurrent genomic alterations, including TP53 mutations, deletions of chromosome 17p, and IgHV mutational status, impacting on response to chemo-immunotherapy and targeted agents. Consequently, diagnostic screening for these predictive biomarkers is recommended in both national and international clinical guidelines. Current conventional methods, including fluorescent in-situ hybridisation and Sanger sequencing, exhibit shortcomings in terms of cost, speed and sensitivity, and even second-generation sequencing methods encounter technical limitations imposed by short-read lengths and bio-informatics analysis. The MinION platform from Oxford Nanopore Technologies generates exceptionally long (1-100kbp) read lengths in a short period of time and at low cost, making it a good candidate for diagnostic testing. In this paper, we present a nanopore-based CLL-specific screening assay, to simultaneously screen for both TP53 mutations and del17p13.1, as well as determining the IgHV mutation status for a single patient in one sequencing run. We sequenced 11 CLL patients and were able to generate a full diagnostic dataset for all. We identified somatic SNVs and indels in the coding region of TP53, and demonstrate that, following error correction of the data, we could accurately define the somatically hypermutated IgHV region in all patients. We also demonstrated the ability of the MinION platform to detect large-scale genomic deletions through low-coverage whole-genome sequencing. We conclude that nanopore sequencing has the potential to provide accurate, low-cost and rapid diagnostic information, which could be applied to other cancer types.

cancer biology↗