Laboratory-based surveillance of Salmonella serotype Typhi infections in the United States - Antimicrobial resistance on the rise

Context Multidrug-resistant Salmonella serotype Typhi infections have been reported worldwide, but data on the incidence of resistant strains in the U nited States are lacking. Objectives To determine the incidence of antimicrobial-resistant Salmonella Typhi infections and to identify risk factors for infection, Design Cross-sectional laboratory-based surveillance study. Setting and Participants A total of 293 persons with symptomatic typhoid fe ver who had Salmonella Typhi isolates and epidemiological information submi tted to US public health departments and laboratories from June 1, 1996, to May 31, 1997, Main Outcome Measures Proportion of Salmonella Typhi isolates demonstrating resistance to 12 antimicrobial agents; patient epidemiological factors ass ociated with drug-resistant infections. Results Median age was 21 years (range, 3 months to 84 years); 56% were mal e, Two hundred twenty-eight (80%) were hospitalized; 2 died. In the 6 weeks before illness onset, 81% of patients had traveled abroad. Seventy-four Sa lmonella Typhi isolates (25%) were resistant to 1 or more antimicrobial age nt, and 51 (17%) were resistant to 5 or more agents, including ampicillin, chloramphenicol, and trimethoprimsulfamethoxazole (multidrug-resistant Salm onella Typhi [MDRST]). Although no resistance to ciprofloxacin or ceftriaxo ne was observed, 20 isolates (7%) were nalidixic acid-resistant (NARST). Pa tients with MDRST and NARST infections were more likely to report travel ou tside the United States, particularly to the Indian subcontinent (Banglades h, India, and Pakistan) (odds ratio [OR], 29.3; 95% confidence interval [CI ], 6.8-126.7; P<.001 and OR, 35.9; 95% CI, 3.4-377.3; P<.001, respectively) . Conclusions Our data suggest that ciprofloxacin and ceftriaxone are appropr iate empirical therapy for suspected typhoid fever; however, resistance may be anticipated. Continued monitoring of antimicrobial resistance among Sal monella Typhi strains will help determine vaccination and treatment policie s.