According to the Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report, a large outbreak of extensively drug-resistant (XDR) typhoid fever in Pakistan during 2016 through 2018 resulted in 5 travel-related cases in the United States.
The Pakistani outbreak was caused by Salmonella enterica serotype Typhi, which was resistant to treatment with chloramphenicol, ampicillin, trimethoprim-sulfamethoxazole, fluoroquinolones, and third-generation cephalosporins, and involved 5372 cases. Therefore, the report warned that travelers to Pakistan may be at significant risk for XDR S Typhi infection and that those affected may have few treatment options. It also cautioned that the outbreak may spread to neighboring countries, such as India.
Providers caring for patients with suspected typhoid fever should inquire about travel history and plan for blood and stool cultures and antimicrobial susceptibility testing. Serologic tests do not yield a bacterial isolate that can be used for antimicrobial susceptibility testing and should not be used. Any confirmed cases should be reported to the local health department, and health departments should then notify the CDC. All S Typhi isolates should be sent to The National Antimicrobial Resistance Monitoring System for antimicrobial susceptibility testing. Further, most typhoid fever infections in the United States are not susceptible to treatment with fluoroquinolone, therefore healthcare providers should not use fluoroquinolones as empiric therapy. In fact, the XDR strain of S Typhi was found to be susceptible only to azithromycin and carbapenems.
The report noted that surveillance data from National Typhoid and Paratyphoid Fever Surveillance and The National Antimicrobial Resistance Monitoring System identify only culture-confirmed infections, which represents only a fraction of the total number of infections. Also, travel history and resistance data were not available for all of those with confirmed cases of typhoid fever.
The CDC recommended that vaccination for S typhi and safe food and water practices while traveling are the best ways to protect from typhoid infection and that travelers who do become ill while abroad or on returning to the United States should seek medical care.
Chatham-Stephens K, Medalla F, Hughes M, et al. Emergence of extensively drug-resistant Salmonella Typhi infections among travelers to or from Pakistan – United States, 2016-2018. MMWR Morb Mortal Wkly Rep. 2019;68:11-13.