Biology subjects

Tsui, C. K. M.

Publications and source records attributed to Tsui, C. K. M..

2 recordsLinked to original sources

bioRxiv2022

Genomic epidemiology revealed the emergence and worldwide dissemination of ST383 carbapenem-resistant hypervirulent Klebsiella pneumoniae and hospital acquired infections of ST196 Klebsiella quasipneumoniae in Qatar

The emergence of carbapenem-resistant (CR) hypervirulent Klebsiella pneumoniae (hvKp) is a new threat to healthcare. In this study, we studied the molecular epidemiology of CR Klebsiella isolates in Qatar using whole genome sequence data. We also characterised the prevalence and genetic basis of hypervirulent phenotypes, and established the virulence potential using a Galleria mellonella model. One hundred CR Klebsiella isolates were recovered, and NDM and OXA-48 were the most common carbapenemases. Phylogenetic analysis indicated the presence of diverse sequence types and clonal lineages; one of them belonged to K. quaisipneumoniae ST196 that may be disseminated among several health care centres. Ten K. pneumoniae isolates carrying rmpA and/or rmpA2, and 2 isolates belonged to KL2, indicating the prevalence of classical hypervirulent (hv) isolates was not high. Isolates carrying CR and hv genes were confined mainly to ST231 and ST383 isolates. One ST383 isolate was further investigated by MinION sequencing, and the assembled genome indicated the blaNDM was located on an IncHI1B type plasmid (pFQ61_ST383_NDM-5), which also harbored several virulence factors, including the regulator of the mucoid phenotype (rmpA), the regulator of mucoid phenotype 2 (rmpA2), and aerobactin (iucABCD and iutA), likely resulting from inversion and recombination events. In contrast, blaOXA-48 was located in an IncL-type plasmid. Comparative genomes indicated the recent evolution and emergence of CR-hv Kp ST383 via the acquisition of hybrid plasmids with both carbapenemase and virulence genes. CR-hv K. pneumoniae ST383 pose an emerging threat to global health due to their simultaneous hypervirulence and multidrug resistance.

microbiology↗

bioRxiv2022

The largest haplotype-phased and chromosome-scale genome assembly of the fungal pathogen, Puccinia polysora, by HiFi reads and Hi-C data

Rust fungi are characterized by large genomes with high repeat content and have two haploid nuclei in most life stages, which makes achieving high-quality genome assemblies challenging. Here, we described a pipeline using HiFi reads and Hi-C data to assemble a gigabase-sized fungal pathogen, Puccinia polysora f.sp. zeae, to haplotype-phased and chromosome-scale. The final assembled genome is 1.71 Gbp, with ~850 Mbp and 18 chromosomes in each haplotype, being currently one of the two giga-scale fungi assembled to chromosome level. Transcript-based annotation identified 47,512 genes for dikaryotic genome with a similar number for each haplotype. A high level of interhaplotype variation was found with 10% haplotype-specific BUSCO genes, 5.8 SNPs/kbp and structural variation accounting for 3% of the genome size. The P. polysora genome displayed over 85% repeat contents, with genome-size expansion and copy number increasing of species-specific orthogroups. Interestingly, these features did not affect overall synteny with other Puccinia species having smaller genomes. Fine-time-point transcriptomics revealed seven clusters of co-expressed secreted proteins that are conserved between two haplotypes. The fact that candidate effectors interspersed with all genes indicated the absence of a "two-speed genome" evolution in P. polysora. Genome resequencing of 79 additional isolates revealed a clonal population structure of P. polysora in China with low geographic differentiation. Nevertheless, a minor population differentiated from the major population by having mutations on secreted proteins including AvrRppC, indicating the ongoing virulence to evade recognition by RppC, a major resistance gene in Chinese corn cultivars. The high-quality assembly provides valuable genomic resources for future studies on disease management and the evolution of P. polysora.

genomics↗