Search bioRxiv⌕ Search

Biology subjects

Kyany'a, C.

Publications and source records attributed to Kyany'a, C..

3 recordsLinked to original sources

Multi-scale modeling of human tissues from spatial transcriptomics with TERRA

Spatial transcriptomics maps gene expression at cellular resolution, revealing how cells organize into multicellular niches. Yet computational analyses remain dataset-specific, without a transferable representation of tissue organization that generalizes across datasets, tasks and tissues or predicts how tissues behave under perturbation. We present TERRA, a foundation model pretrained on 112 million human cells profiled by spatial transcriptomics. From a single pretrained backbone, TERRA yields embeddings at the scale of cells, the genes they express and the neighborhoods in which they reside, and supports spatial in silico perturbation, all applied zero-shot to unseen tissues. At the cell level, in newly generated spatial data for developing pancreas, TERRA identified an islet-associated capillary state which we posit represents a developmental precursor of the mature islet microvasculature. At the gene level, in untreated kidney sections, in silico knockout of immune-checkpoint targets predicted a gene program of immune-checkpoint-blockade-associated nephrotoxicity, which we validated in treatment-exposed tissue and recovered in blood. At the neighborhood level, TERRA mapped macrophages across tissues to identify recurring cross-organ niches, which we term archetypes, including a tumor-boundary niche associated with poor prognosis in kidney cancer. Together, TERRA captures the spatial and multicellular logic of human tissue and predicts, in silico, its response to perturbation, providing a multi-scale framework for tissue biology, therapeutic development and clinical application.

genomics↗

Antimicrobial resistance and virulence characteristics of Klebsiella pneumoniae isolates in Kenya

Klebsiella pneumoniae is a globally significant opportunistic pathogen causing healthcare-associated and community-acquired infections. This study examined the epidemiology and the distribution of resistance and virulence genes in clinical K. pneumoniae strains in Kenya. Eighty-nine K. pneumoniae isolates were collected over six years from five counties in Kenya and were analyzed using whole genome sequencing and bioinformatics. These isolates were obtained from community-acquired (62/89) and healthcare-associated infections (21/89), and the hospital environment (6/89). Genetic analysis revealed the presence of blaNDM-1 and blaOXA-181 carbapenemase genes and the armA and rmtF genes known to confer pan-aminoglycoside resistance. The most abundant extended-spectrum beta-lactamase genes identified were blaCTX-M-15 (36/89), blaTEM (35/89), and blaOXA (18/89). In addition, one isolate had a mobile colistin resistance gene (mcr-8). Fluoroquinolone resistance-conferring mutations in gyrA and parC genes were also observed. The most notable virulence factors were those associated with hyper-virulence (rmpA/A2 and magA), yersiniabactin (ybt), salmochelin (iro), and aerobactin (iuc and iutA). Thirty-eight distinct sequence types were identified, including known global lineages ST14, ST15, ST147, and ST307, and a regional clone ST17 implicated in regional outbreaks. In addition, this study genetically characterized two potential hypervirulent isolates and two community-acquired ST147 high-risk clones that contained carbapenemase genes, yersiniabactin, and other multidrug resistance genes. These results demonstrate that the resistome and virulome of Kenyan clinical and hospital environmental K. pneumoniae isolates are diverse. The reservoir of high risk-clones capable of spreading resistance and virulence factors have the potential to cause unmanageable infection outbreaks with high morbidity and mortality. AUTHOR SUMMARYKlebsiella pneumoniae is one of the human-disease-causing bacteria that easily acquires and spreads antibiotic resistance genes and is thus a serious threat to human health. We studied both the antibiotic resistance genes and the genes it uses to cause disease (virulence). Forty-two percent of our isolates were multidrug resistant (MDR). They carried several resistance and virulence genes bound in mobile circular DNA molecules called plasmids which easily migrate and spread the genes between bacteria. We identified 38 distinct K. pneumoniae strains (STs) distributed within the study sites. Fifteen isolates were classified under the groups of K. pneumoniae strains known to cause global infection outbreaks such as ST14, ST15 and ST147 collected from Nairobi and Kisumu, hotspot areas for spread of resistance. In particular, two ST147 isolates were resistant to carbapenems and one isolate to colistin, which are last line antibiotics. We also identified two isolates with the potential to cause high levels of disease. We concluded that the presence of highly resistant and virulent strains in the hospital and community demonstrates a need for the continuous monitoring and management of MDR K. pneumoniae infections to prevent disease outbreaks that are difficult to control and that lead to high death rate.

microbiology↗

A 7-member SNP Assay on the iPlex MassARRAY Platform Provides a Rapid and Affordable Alternative to Typing Major African Staphylococcus aureus Types

BackgroundData on the clonal distribution of Staphylococcus aureus in Africa is scanty, partly due to high costs and long turnaround times imposed by conventional genotyping methods such as spa and multilocus sequence typing (MLST) warranting the need for alternative typing approaches. This study applied and evaluated the accuracy, cost and time of using iPlex massARRAY genotyping method on Kenyan staphylococcal isolates.\n\nMethodsFifty four clinical S. aureus isolates from three counties were characterized using iPlex massARRAY, spa and MLST typing methods. Ten Single Nucleotide Polymorphisms (SNPs) from the S. aureus MLST database were assessed by iPlex massARRAY.\n\nResultsThe iPlex massARRAY assay grouped the isolates into 14 SNP genotypes with 9/10 SNPs interrogated showing high detection rates (average 89%). spa and MLST typing revealed 22 spa types and 21 STs that displayed unique regional distribution. spa type t355 (ST152) was the dominant type and t2029 and t037 (ST 241) were observed among MRSA strains. MassARRAY showed 83% and 82% accuracy against spa and MLST typing respectively in isolate classification. Moreover, massARRAY identified all MRSA strains and a novel spa type. MassARRAY had reduced turnaround time (<12 hrs) compared to spa (3 days) and MLST (20 days) typing. The iPlex massARRAY cost approximately 18 USD compared to spa (30 USD) and MLST (126 USD) typing based on consumable costs/isolate.\n\nConclusionUpon validation with a larger collection of isolates, iPlex massARRAY could provide a faster, more affordable and fairly accurate method of resolving African S.aureus isolates especially in large surveillance studies.

microbiology↗