Improved diagnostics are crucial in the fight against typhoid fever. Current methods are inadequate. Blood culture tests are considered the gold standard, yet often misidentify typhoid fever as other enteric diseases, such as paratyphoid. Moreover, blood culture tests can be costly and difficult to administer in clinics operating with few resources. Other approaches, such as nucleic acid and antigen-detection tests, have been met with similar problems.
Without effective diagnostic methods, it is difficult to identify patients, determine treatment, and track the spread of disease. Typhoid and paratyphoid are almost indistinguishable in terms of symptoms, but are caused by distinct strains of Salmonella enterica. Salmonella Typhi and Paratyphi have different epidemiologies, geographic distribution, clinical manifestations, and tendencies to develop anti-microbial resistance. Thus, being able to distinguish between the two is crucial for determining proper treatment and tracking disease dispersal.
A new study, using a technique called metabolomics, may have taken a crucial first step towards developing the next generation of typhoid diagnostics. Metabolomics rests on the idea that infection induces metabolic changes in the host, which can be detected by measuring various metabolites in the blood. This study compared the metabolite profiles from healthy patients to profiles of patients with typhoid and paratyphoid infections. Similar studies have used metabolomics to identify diagnostic markers of malaria and dengue fever.
The researchers used a combination of mass spectrophotometry and gas chromatography to determine the metabolite profiles of 75 patients from the same healthcare facility. Statistical analysis revealed that cases of enteric fever could be easily distinguished from controls. In addition, typhoid cases could be distinguished from paratyphoid cases, though not as easily. The researchers identified 6 key metabolites that can be used to distinguish between typhoid cases, paratyphoid cases, and controls. While most of the distinguishing metabolites were unknown, there were several that offered plausible explanations.
Though these findings are promising, much more research must be conducted before this methodology could be applied in clinical settings. It is unclear whether the 6 metabolites identified by the researchers could be used as diagnostic markers across all populations. In addition, this technology must be made more portable and affordable if it is to be used in high-risk, underdeveloped communities.