Epidemiological connectivity between humans and animals across an urban landscape.

Urbanization is predicted to be a key driver of disease emergence through human exposure to novel, animal-borne pathogens. However, while we suspect that urban landscapes are primed to expose people to novel animal-borne diseases, evidence for the mechanisms by which this occurs is lacking. To address this, we studied how bacterial genes are shared between wild animals, livestock, and humans (n = 1,428) across Nairobi, Kenya-one of the world's most rapidly developing cities. Applying a multilayer network framework, we show that low biodiversity (of both natural habitat and vertebrate wildlife communities), coupled with livestock management practices and more densely populated urban environments, promotes sharing of Escherichia coli-borne bacterial mobile genetic elements between animals and humans. These results provide empirical support for hypotheses linking resource provision, the biological simplification of urban landscapes, and human and livestock demography to urban dynamics of cross-species pathogen transmission at a landscape scale. Urban areas where high densities of people and livestock live in close association with synanthropes (species such as rodents that are more competent reservoirs for zoonotic pathogens) should be prioritized for disease surveillance and control.

Genomic epidemiology of Escherichia coli: antimicrobial resistance through a One Health lens in sympatric humans, livestock and peri-domestic wildlife in Nairobi, Kenya.

BACKGROUND: Livestock systems have been proposed as a reservoir for antimicrobial-resistant (AMR) bacteria and AMR genetic determinants that may infect or colonise humans, yet quantitative evidence regarding their epidemiological role remains lacking. Here, we used a combination of genomics, epidemiology and ecology to investigate patterns of AMR gene carriage in Escherichia coli, regarded as a sentinel organism. METHODS: We conducted a structured epidemiological survey of 99 households across Nairobi, Kenya, and whole genome sequenced E. coli isolates from 311 human, 606 livestock and 399 wildlife faecal samples. We used statistical models to investigate the prevalence of AMR carriage and characterise AMR gene diversity and structure of AMR genes in different host populations across the city. We also investigated household-level risk factors for the exchange of AMR genes between sympatric humans and livestock. RESULTS: We detected 56 unique acquired genes along with 13 point mutations present in variable proportions in human and animal isolates, known to confer resistance to nine antibiotic classes. We find that AMR gene community composition is not associated with host species, but AMR genes were frequently co-located, potentially enabling the acquisition and dispersal of multi-drug resistance in a single step. We find that whilst keeping livestock had no influence on human AMR gene carriage, the potential for AMR transmission across human-livestock interfaces is greatest when manure is poorly disposed of and in larger households. CONCLUSIONS: Findings of widespread carriage of AMR bacteria in human and animal populations, including in long-distance wildlife species, in community settings highlight the value of evidence-based surveillance to address antimicrobial resistance on a global scale. Our genomic analysis provided an in-depth understanding of AMR determinants at the interfaces of One Health sectors that will inform AMR prevention and control.

Serological evidence of chronic pulmonary Aspergillosis in tuberculosis patients in Kenya.

BACKGROUND: Pulmonary tuberculosis (PTB) is a significant risk factor for fungal infection. The cavitary lesions post PTB serves as a good reservoir for fungal colonization and subsequent infection. Furthermore, the severe immunosuppression associated with HIV and TB co-infection is another predisposition. The inadequate capacity to investigate and manage fungal infection in PTB patients increases their morbidity and mortality. The study aimed to provide serological evidence of chronic pulmonary aspergillosis (CPA) among PTB patients in Kenya. Towards this, we analysed 234 serum samples from patients presenting with persistent clinical features of PTB infections despite TB treatment in four referral hospitals. METHODS: This was a cross sectional laboratory based study and patients were recruited following an informed consent. Serological detection of Aspergillus fumigatus IgG was done using enzyme-linked immunosorbent assay (Bordier Affinity Products SA). Sputum samples were subjected to microscopy and standard fungal culture. The isolated fungi were subjected to macro and micro morphological identifications and confirmed by sequence analysis of calmadulin, betatubilin and ITS genes. RESULTS: Serological evidence of CPA or fungal sensitization was 46(19.7%) and equivocal or borderline was 14(6.0%). Mycological investigations of sputum resulted in 88(38%) positive for fungal culture. Aspergillus spp. accounted for 25(28%) of which A. fumigatus was 13(14.8%), A. niger 8(9.1%), A. terreus, A. flavus, A. candidus and A. clavatus 1 (1.1%) each. This was followed by Penicillium spp. 10 (11.4%), Scedosporium spp. 5 (5.7%) and Rhizopus spp. 3 (3.4%). Among the yeasts; Candida albicans accounted for 18(20.5%) followed by C. glabrata 5(5.7%). Cryptococcus spp. was isolated from 3(3.4%) of the samples while 13(14.8%) were other yeasts. CONCLUSION: Chronic pulmonary aspergillosis is a significant co-morbidity in PTB patients in Kenya that could be misdiagnosed as relapse or treatment failures in the absence of reliable diagnostic and clinical management algorithm. It could be the cause of persistent clinical symptoms despite TB treatment often misdiagnosed as TB smear/GeneXpert MTB/RIF® negative or relapse. We recommend that all patients with persistent clinical symptoms despite TB treatment should be subjected to fungal investigations before retreatment.

Draft Genome Sequence of an Enterotoxigenic Escherichia coli Strain Carrying Genes for Colonization Surface Antigen 13 and a Heat-Labile Toxin.

Here, we report the draft genome of ESEI_597, an enterotoxigenic Escherichia coli (ETEC) strain harboring genes encoding colonization surface antigen 13 (CS13) and a heat-labile toxin. The ESEI_597 strain was isolated from an 8-month-old child living in Korogocho, Kenya, in 2013.

Population genomics of Escherichia coli in livestock-keeping households across a rapidly developing urban landscape.

Quantitative evidence for the risk of zoonoses and the spread of antimicrobial resistance remains lacking. Here, as part of the UrbanZoo project, we sampled Escherichia coli from humans, livestock and peri-domestic wildlife in 99 households across Nairobi, Kenya, to investigate its distribution among host species in this rapidly developing urban landscape. We performed whole-genome sequencing of 1,338 E. coli isolates and found that the diversity and sharing patterns of E. coli were heavily structured by household and strongly shaped by host type. We also found evidence for inter-household and inter-host sharing and, importantly, between humans and animals, although this occurs much less frequently. Resistome similarity was differently distributed across host and household, consistent with being driven by shared exposure to antimicrobials. Our results indicate that a large, epidemiologically structured sampling framework combined with WGS is needed to uncover strain-sharing events among different host populations in complex environments and the major contributing pathways that could ultimately drive the emergence of zoonoses and the spread of antimicrobial resistance.

A putative, novel coli surface antigen 8B (CS8B) of enterotoxigenic Escherichia coli.

Enterotoxigenic Escherichia coli (ETEC) strains harbor multiple fimbriae and pili to mediate host colonization, including the type IVb pilus, colonization factor antigen III (CFA/III). Not all colonization factors are well characterized or known in toxin positive ETEC isolates, which may have an impact identifying ETEC isolates based on molecular screening of these biomarkers. We describe a novel coli surface antigen (CS) 8 subtype B (CS8B), a family of CFA/III pilus, in a toxin producing ETEC isolate from a Kenyan collection. In highlighting the existence of this putative CS, we provide the sequence and specific primers, which can be used alongside other ETEC primers previously described.