Molecular detection of Salmonella species and assessment of drug combination against enteric bacteria

Abstract

The prolonged systemic illness typhoid continues to be a huge burden on low to middle income countries like Asia and Africa, with global estimate of 16-22 million incidences annually. The disease is predominantly affecting millions of people worldwide, most of them living under impoverished condition. Inadequate diagnostic systems, lack of sanitation and safe potable drinking water in endemic areas remain major problems. Moreover, the emerging threat of multidrug resistance (MDR) in bacterial strains further aggravates the disease especially in urban areas. The clinical diagnosis of typhoid is often difficult because of the overlapping sign and symptoms observed with other febrile illnesses such as malaria, dengue fever and rickettsioses. Current mode of diagnosis depends upon the isolation of pathogen from blood or either the high titer of agglutinating antibody against somatic (O) or flagellar (H) antigen of Salmonella Typhi. The conventional blood culture methods have several limitations including requirement of large volume of blood (1 to 15 ml) due to low level of circulating bacteria (0.5-22 bacteria per milliliter of blood), prior antimicrobial uses, and limited laboratory expertise. Several efforts have been made to enhance the yield of blood culture including broth pre-enrichment, incubation period (and#8805; 48h), and cell lytic media to release intracellular Salmonella Typhi. Further, the likelihood of a positive blood culture and serological diagnosis significantly decreases with delayed presentation or prior use of antibiotic. Serological assay, primarily Widal agglutination has certain pitfalls in terms of sensitivity, specificity and confusing result interpretation in endemic areas where the disease is highly prevalent. Even though of its low utility, the Widal test is still widely used in developing countries. Moreover, the other diagnostic test such as dipstick, tubex and typhidot have shown conflicting results in developing countries (Vietnam and Bangladesh) with low sensitivity(78%, 86%, 83.4% ) and sp