Salmonella enterica serovar enterica serotype Typhi (Salmonella Typhi) are Gram negative bacterium which preferentially infects humans causing a devastating disease called enteric fever or typhoid fever (TF) (1). The disease causes loss of many lives mostly in the low and medium income countries (LMICs) due to the fact that these countries have poor sanitary systems, diagnostic facilities and proper surveillance systems (2). Due to lack of specialised diagnostics the treatment of most cases is empirically done. Wang et al. (3) estimated that typhoid fever incidences were about 10 million causing almost 120,000 deaths in the year 2017.
TF is transmitted through the faeco-oral route when an individual ingests food or water contaminated with Salmonella Typhi (4). However recently it has been reported that individuals can be indirectly infected through contact with faecal contamination in their immediate environment. The disease has high prevalence in the LMICs due to the fact that people living in these countries always face lack access to clean and safe water. Evidently TF diagnosis in LMICs relies on Widal test, which is a point of care test that requires confirmation by stool or blood culture of the suspected patient, which is unlikely to be done.
The morbidity of TF in the LIMCs is an interaction of events in the specific host and environmental or with other microbiomes (5). Furthermore it may entail the understanding of the bacterial mechanisms that enable it to survive in the environment and infected hosts before either infect or re-infecting another human. Currently, studies on Salmonella Typhi have shown that the bacterium cannot thrive well in the non-human hosts, while its survival in free-living organisms is shorter or is unclearly stated compared to other minute organisms.
Douesnard-Malo and Daigle (6) carried out a study to establish how long can Salmonella Typhi survive in living organisms. The authors showed that, the bacterial survival in free living amoeba (Acanthamoeba castellanii) is not more than three weeks, a finding which cannot substantiate the rampancy of the disease incidences. S. Typhi is unlike the other species of Salmonella which co-exist with other free living organisms. Besides, TF incidences are reported in both rainy seasons and dry seasons, signifying that typhoid persistence in LMICs is associated with factors which cause long-term survival of the aetiology either in the environment or in unidentified microbiomes.
The occurrence of TF in both seasons calls for the need to carry out studies to determine the role of the environment on the survival of the aetiology. Studies have shown that fish, live animals and their wastes could impact significant microbiotic interaction on the survival of enteric bacteria infecting human. The findings by Douesnard-Malo and Daigle (6) which showed that S. Typhi infected free living amoeba were based on laboratory settings involving co-cultures of the bacterium with the protozoa in which temperature, pH and nutrient availability were controlled. It is therefore imperative to undertake studies which establish the occurrence of S. Typhi in its wild environment such as sewage systems in LMICs. The need to change the mind-set of carrying out research basing on the study of S. Typhi comes on the concern that where does the escalation of antibiotic resistance in this pathogens. Is it possible that environmental factors contribute to the development of antibiotic resistance and transmissibility of associated genes among Salmonella spp?
The project intends to carry out research on existing challenges which remain untold regarding TF and its aetiology. The project will investigate the impact of various ecological niches on the survival of the bacteria within and without the specific host. That is for how long does S. Typhi survive in its hostile environment (soil, water, animal wastes) compared to the specific hosts (human). In the patients who have either recovered or diseased, what are the immunological complexes which facilitate the existence of the bacteria within cells without being dealt with the immune system? In the environment what are the factors that facilitate its survival and generate baseline data on the influence of these factors to the exposure and development of antibiotic resistance profiles (8). Furthermore genome sequencing and analysis will be done to classify the phylogenetic and genotypic relation of S. Typhi isolated from different sources and geographical location so as to associate the source of isolation, location and infection.
Besides geospatial data will be collected so that to match the source of isolation (sample), geographical location and genomic analysis for mapping TF hotspots. Furthermore spatial modelling will be done to justify TF morbidity, hotspots, typographical and whether surface water accumulation is inclined to the spatial and temporal patterns of TF. The open data and geospatial analysis will further be used to describe the mitigation of monitoring, controlling and elimination of Typhoid fever.