Typhoidal Salmonella and Emerging Resistance in Outbreak Proportions

Introduction: Typhoidal Salmonella causes an invasive infection resulting in 200 000 deaths among 20 million patients annually. Typhoid remains a public health problem in Southeast Asia, the Indian subcontinent, Africa, and South America. Traveler’s diarrhea caused by Salmonella is common in Asia. Outbreaks of typhoidal Salmonella resistant to ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole in the 1990s pushed therapy to ciprofloxacin which was replaced by ceftriaxone due to fluoroquinolone resistance. Methods: This prospective study characterizes demographical, etiological, and resistance patterns in typhoidal Salmonella at a 1000-bed teaching hospital in New Delhi, India. Two hundred inpatients in pediatrics, obstetrics-gynecology, medicine, intensive care, and OPD in whom Salmonella bacteremia was detected were characterized by routine and automated microbiology techniques. Results: The mean age of patients in this study was 21.4 years. Overall, 71% of patients suffered from Salmonella Typhi followed by 26% from Salmonella Paratyphi A. Four cases of Salmonella resistance to ampicillin, trimethoprim-sulfamethoxazole, and chloramphenicol were encountered. A high degree of partial and complete resistance to fluoroquinolones was seen among Salmonella Typhi, Salmonella Paratyphi A, and Salmonella Paratyphi B cases. Resistance to ciprofloxacin was 48% among Salmonella Typhi and 100% among Salmonella Paratyphi A cases. Only 18% of Salmonella Typhi cases were completely resistant to quinolones, while 79% were partially resistant. A total of 92% of Salmonella Paratyphi A cases were partially resistant to quinolones. Four Salmonella cases were resistant to ceftriaxone. Conclusion: Salmonella Typhi remains the predominant serotype, followed by Salmonella Paratyphi A. The high prevalence of quinolone resistance in Salmonella Typhi and Salmonella Paratyphi A is a serious problem limiting empirical therapy to non-quinolone-based therapy such as ceftriaxone. Multidrug-resistant Salmonella is an emerging problem requiring active surveillance among residents and travelers presenting with tropical fever.