Polysaccharide-Based Conjugate Vaccines for Enteric Bacterial Infections: Typhoid Fever, Nontyphoidal Salmonellosis, and Escherichia coli O157:H7

TYPHOID FEVER Typhoid fever, which is transmitted to susceptible hosts by food and water contaminated with S. typhi, remains a major health problem in developing countries. Since the 1990s, the emergence of antibiotic resistant strains has made the treatment of typhoid fever more difficult (14). Asymptomatic carriers constitute the reservoir of infection (15). With no near-term solution to providing clean water and environment to all populations in developing countries, vaccination is a costeffective way to control and eliminate this disease (16-18).