Laboratory-Based Surveillance of Salmonella Serotype Typhi Infections in the United States

Abstract

Multidrug-resistant Salmonella serotype Typhi infections have been reported worldwide, but data on the incidence of resistant strains in the United States are lacking. To determine the incidence of antimicrobial-resistant Salmonella Typhi infections and to identify risk factors for infection. Cross-sectional laboratory-based surveillance study. A total of 293 persons with symptomatic typhoid fever who had Salmonella Typhi isolates and epidemiological information submitted to US public health departments and laboratories from June 1, 1996, to May 31, 1997. Proportion of Salmonella Typhi isolates demonstrating resistance to 12 antimicrobial agents; patient epidemiological factors associated with drug-resistant infections. Median age was 21 years (range, 3 months to 84 years); 56% were male. Two hundred twenty-eight (80%) were hospitalized; 2 died. In the 6 weeks before illness onset, 81% of patients had traveled abroad. Seventy-four Salmonella Typhi isolates (25%) were resistant to 1 or more antimicrobial agent, and 51 (17%) were resistant to 5 or more agents, including ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole (multidrug-resistant Salmonella Typhi [MDRST]). Although no resistance to ciprofloxacin or ceftriaxone was observed, 20 isolates (7%) were nalidixic acid-resistant (NARST). Patients with MDRST and NARST infections were more likely to report travel outside the United States, particularly to the Indian subcontinent (Bangladesh, 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). Our data suggest that ciprofloxacin and ceftriaxone are appropriate empirical therapy for suspected typhoid fever; however, resistance may be anticipated. Continued monitoring of antimicrobial resistance among Salmonella Typhi strains will help determine vaccination and treatment policies. JAMA. 2000;283:2668-2673.