Salmonella chronic carriage: epidemiology, diagnosis, and gallbladder persistence

Abstract

Typhoid (enteric fever) remains a major cause of morbidity and mortality worldwide, causing over 21 million new infections annually, with the majority of deaths occurring in young children. Because typhoid fever-causing Salmonella have no known environmental reservoir, the chronic, asymptomatic carrier state is thought to be a key feature of continued maintenance of the bacterium within human populations. Despite the importance of this disease to public health, our understanding of the molecular mechanisms that catalyze carriage, as well as our ability to reliably identify and treat the Salmonella carrier state, have only recently begun to advance.

Keywords: Salmonella; chronic carrier; diagnostics; epidemiology; typhoid fever.

Figure 1

Biofilm formation on gallstones of typhoid carriers. Gallstones from Nepalese patients without (A) and with (B) S. Typhi chronic infections were imaged by scanning electron microscopy (SEM). After removal from the patient, the gallstones were air dried in a laminar flow hood for 24 hrs. They were then fixed in 2.5% glutaraldehyde (0.1M Phosphate buffer, 0.1M sucrose, pH 7.4) for 24 hrs., washed 3 times with water and air dried prior to SEM. Note the extensive biofilm of bacteria in image B with a visible extracellular matrix that encases and protects the bacteria.