Identifying the sources of human campylobacteriosis in Nigeria.

Campylobacter spp. have been shown to be the most common cause of bacterial gastroenteritis worldwide. Cases of human campylobacteriosis are usually reported as sporadic and not part of an outbreak which makes the identification of the source of infection difficult. A study of the relationships within isolate populations in Nigeria and source attribution analysis of Nigerian human Campylobacter spp. to other animal isolates was carried out to determine the possible sources for human Campylobacter infection in Nigeria. The results showed nine sequence types (STs) common to both humans and livestock isolated from abattoirs, farms and live bird markets with similar STs clustering together on a phylogenetic tree, confirming a degree of genetic similarity. Source attribution analysis suggests wild birds as the most important reservoir (38%) for human Campylobacter spp. infection in Nigeria followed by chicken (23%), pig (19%), cattle (11%) and sheep (8%). This might be an indication of the importance of this infection source to humans in Nigeria and probably other low-income countries due to farming practices and human habits.

Evidence for phenotypic plasticity among multihost Campylobacter jejuni and C. coli lineages, obtained using ribosomal multilocus sequence typing and Raman spectroscopy.

Closely related bacterial isolates can display divergent phenotypes. This can limit the usefulness of phylogenetic studies for understanding bacterial ecology and evolution. Here, we compare phenotyping based on Raman spectrometric analysis of cellular composition to phylogenetic classification by ribosomal multilocus sequence typing (rMLST) in 108 isolates of the zoonotic pathogens Campylobacter jejuni and C. coli. Automatic relevance determination (ARD) was used to identify informative peaks in the Raman spectra that could be used to distinguish strains in taxonomic and host source groups (species, clade, clonal complex, and isolate source/host). Phenotypic characterization based on Raman spectra showed a degree of agreement with genotypic classification using rMLST, with segregation accuracy between species (83.95%), clade (in C. coli, 98.41%), and, to some extent, clonal complex (86.89% C. jejuni ST-21 and ST-45 complexes) being achieved. This confirmed the utility of Raman spectroscopy for lineage classification and the correlation between genotypic and phenotypic classification. In parallel analysis, relatively distantly related isolates (different clonal complexes) were assigned the correct host origin irrespective of the clonal origin (74.07 to 96.97% accuracy) based upon different Raman peaks. This suggests that the phenotypic characteristics, from which the phenotypic signal is derived, are not fixed by clonal descent but are influenced by the host environment and change as strains move between hosts.