Other Flashcards
Buruli ulcer: transmission pathway unknown
caused by bacteria mycobacterium ulcerans.
nodule -> swelling -> ulcer -> necrotized skin.
Ignored early, nodules could be thought of as a simple bite.
Treated by skin excision and/ or long antibiotic treatment.
Difficult to culture pathogen from site.
reductive evolution -> reduction in genome indicative of environmental to in vivo and specialisation in this niche. Very limited genetic difference between strains.
Transmission pathway unknown - environmental reservoir?
- rarely person to person
- associated with wetlands and manmade changes to environment (deforestation, digging, dam)
- vector or cuts? lesion patterns with mosquitoes or places kids fall not same. Mixed mode of transmission.
- ulcerans serological assays positive for kids only after 5yrs. They collect water more then? Out the house more?
Australia - possum vector? They develop lesions in response to infection. Grasscutters linked in Africa?
Phylogenetic comparison of strains from 2 regions in cameroon did not suggest a far travelling reservoir. Strains from one site clustered distinctly from strains from the other site.
Not free-floating in river.
Strains found upriver from weija lake are not found in the mouth.
Leprosy: Importance of markers
Mycobacterium leprae, bacteria.
Potential animal host (armadillo, squirrels). Zoonosis. One form contagious between people.
Diagnosis difficult. Can’t culture in vitro. Detect in skin biopsies. Long treatments.
Decrease in prevalence (current infection) over time but sustain of incidence (sustained new cases) could indicate animal reservoir.
little diversity between strains.
VNTR typing (variable locus tandem repeats) Build up a barcode to differentiate strains.
If you don’t do whole genome sequencing, you can’t infer which way round the transmission happened? Armadillo to humans or other way round? Mol epi should allow us to infer direction with enough genomic information.
Paper exemplifies power of different markers in increasing discriminatory power.
Initial exploration: 3 US patients (never left US), 1 US armadillo. WGS sequences identical.
Widening level of marker (Brazil and Asia) and comparing to previous US strains, gave 51 SNPs and 11bp indel.
With this info, genotyped these loci and 10 VNTR regions of 33 US armadillos, US patients, venezuelan patients and a few other foreign strains. With a series of “if” statements (SNP at site xyz is G, 4 repeats at site abc) then it must be strain X. A lot of the armadillos and patients in armadillo areas shared a genotype not seen in other places.
