The patient described above is experiencing symptoms consistent with a Salmonella typhi infection. The carrier state is mediated by the preferred localization of the bacteria to the gallbladder.
When Salmonella typhi bacteria enter the body, the bacteria are taken up by phagocytes in Peyer's patches where they proliferate intracellularly. From the small intestine, S. typhi is able to spread to other sites in the body and colonize other organs (such as the liver, spleen, and gallbladder). This spreading is associated with the presence of bacteria within the bloodstream (bacteremia) and can cause a febrile state. In certain individuals, S. typhi has been known to localize to the gallbladder and become excreted in the feces thus creating an "asymptomatic carrier", a person who can infect others with S. typhi without being affected him/herself.
Khan et al. describe a case of infective endocarditis caused by Salmonella typhi in which an S. typhi was found in the blood and urine of a patient with documented aortic valve disease and endocarditis. Treatment consisted of 4 weeks of antibiotic after which the patient made a full recovery.
Lo Re and Gluckman state that S. typhi is most commonly found in tropical climates such as Mexico, India, the Philippines, and the Caribbean nations. Symptoms typically include sustained fever, anorexia, malaise, abdominal discomfort as well as Rose spots in 30-50% of patients.
Answer 2: Though the spleen is a site where S. typhi can infect, it does not contribute to the carrier state.
Answer 3: Infection of CD4 T-cells is more consistent with a HIV infection.
Answer 4: Infection of the lungs is not associated with the S. typhi carrier state.
Answer 5: Infection of the sensory ganglia is more consistent with a Herpes virus infection.
Khan GQ, Kadri SM, Hassan G, Shahid IT, Gazanfar A, Kak M, Showkat H. Salmonella typhi endocarditis: a case report. J Clin Pathol. 2003 Oct;56(10):801-2. Review.
PMID:14514792 (Link to Abstract)
Lo Re V 3rd, Gluckman SJ. Fever in the returned traveler. Am Fam Physician. 2003 Oct 1;68(7)
PMID:14567489 (Link to Abstract)