Biology subjects

Anscombe, C.

Publications and source records attributed to Anscombe, C..

4 recordsLinked to original sources

bioRxiv2024

An exploration of unusual antimicrobial resistance phenotypes in Salmonella Typhi from Blantyre, Malawi reveals the ongoing role of IncHI1 plasmids

Typhoid fever is a significant public health problem endemic in Southeast Asia and Sub- Saharan Africa. Antimicrobial treatment of typhoid is however threatened by the increasing prevalence of antimicrobial resistant (AMR) S. Typhi, especially in the globally successful lineage (4.3.1) which has rapidly spread in East and Southern Africa. AMR elements can be found either on plasmids or in one of the three chromosomal integration sites, and there is variability of this across the lineage. Several previous studies with Malawian isolates indicated a clonal, locally spreading lineage with chromosomally integrated resistance genes. In a recent study however we noted three isolates with unusual predicted resistance profiles, and we here present the resolved genomes of these isolates using long- and short-read sequencing. Our work shows that these isolates are potentially imported cases, most closely related to the recently described sub-lineage 4.3.1.EA1, and encode IncHI1 plasmids with reduced resistance profiles compared to the major reference sequence of these plasmids spreading in East Africa. Similar reduced resistance plasmids were reported in a recent large-scale study in five isolates from Tanzania, highlighting the urgency for better coverage of the African continent in genome studies to better understand the dynamics of these potentially co-circulating plasmids.

genomics↗

bioRxiv2022

Distribution and origins of Mycobacterium tuberculosis L4 in Southeast Asia

Molecular and genomic studies have revealed that Mycobacterium tuberculosis Lineage 4 (L4, Euro-American lineage) emerged in Europe before becoming distributed around the globe by trade routes, colonial migration, and other historical connections. Although L4 accounts for tens or hundreds of thousands of TB cases in multiple Southeast Asian countries, phylogeographic studies have either focussed on a single country or just included Southeast Asia as part of a global analysis. Therefore, we interrogated public genomic data to investigate the historical patterns underlying the distribution of L4 in Southeast Asia and surrounding countries. We downloaded 6037 genomes associated with 23 published studies, focusing on global analyses of L4 and Asian studies of M. tuberculosis. We identified 2256 L4 genomes including 968 from Asia. We show that 81% of L4 in Thailand, 51% of L4 in Vietnam and 9% of L4 in Indonesia belong to sub-clades of L4 that are rarely seen outside East and Southeast Asia. These sub-clades have been transmitted between East and Southeast Asian countries, with no recent European ancestor. Although there is considerable uncertainty about the exact direction and order of intra-Asian transmissions, due to differing sampling frames between countries, our analysis suggests that China may be the intermediate between Europe and Southeast Asia for two of the three predominantly East and Southeast Asian L4 sub-lineages. This new perspective on L4 in Southeast Asia raises the possibility of investigating host population specific evolution and highlights the need for more structured sampling from Southeast Asian countries to provide more certainty of the historical and current routes of transmission.

microbiology↗

bioRxiv2018

Genomics of Cryptococcus neoformans

C. neoformans var. grubii (C. neoformans) is an environmentally acquired pathogen causing 181 000 HIV-associated deaths each year. We used whole genome sequencing (WGS) to characterise 699 isolates, primarily C. neoformans from HIV-infected patients, from 5 countries in Asia and Africa. We found that 91% of our clinical isolates belonged to one of three highly clonal sub-clades of VNIa, which we have termed VNIa-4, VNIa-5 and VNIa-93. Parsimony analysis revealed frequent, long distance transmissions of C. neoformans; international transmissions took place on 13% of VNIa-4 branches, and intercontinental transmissions on 7% of VNIa-93 branches. The median length of within sub-clade internal branches was 3-6 SNPs, while terminal branches were 44.5-77.5 SNPs. The short median internal branches were partly driven by the large number (12-15% of internal branches) of polytomies in the within-sub-clade trees. To simultaneously explain our observation of no apparent molecular clock, short internal branches and frequent polytomies we hypothesise that C. neoformans VNIa spends much of its time in the environment in a quiescent state, while, when it is sampled, it has almost always undergone an extended period of growth. Infections with VNIa-93 were associated with a significantly reduced risk of death by 10 weeks compared with infections with VNIa-4 (Hazard Ratio = 0.45, p = 0.003). We detected a recombination in the mitochondrial sequence of VNIa-5, suggesting that mitochondria could be involved in the propensity of this sub-clade to infect HIV-uninfected patients. These data highlight the insight into the biology and epidemiology of pathogenic fungi which can be gained from WGS data.

microbiology↗

bioRxiv2017

Rapid whole genome amplification and sequencing of low cell numbers in a bacteraemia model

Whilst next generation sequencing is frequently used to whole genome sequence bacteria from cultures, its rarely applied directly to clinical samples. Therefore, this study addresses the issue of applying NGS microbial diagnostics directly to blood samples. To demonstrate the potential of direct from blood sequencing a bacteria spiked blood model was developed. Horse blood was spiked with clinical samples of E. coli and S. aureus, and a process developed to isolate bacterial cells whilst removing the majority of host DNA. One sample of each isolate was then amplified using {phi}29 multiple displacement amplification (MDA) and sequenced. The total processing time, from sample to amplified DNA ready for sequencing was 3.5 hours, significantly faster than the 18-hour overnight culture step which is typically required. Both bacteria showed 100% survival through the processing. The direct from sample sequencing resulted in greater than 92% genome coverage of the pathogens whilst limiting the sequencing of host genome (less than 7% of all reads). Analysis of de novo assembled reads allowed accurate genotypic antibiotic resistance prediction. The sample processing is easily applicable to multiple sequencing platforms. Overall this model demonstrates potential to rapidly generate whole genome bacterial data directly from blood.

microbiology↗