Drug-resistant strains most common among visitors to Indian subcontinent, CDC reports
TUESDAY, Aug. 25 (HealthDay News) -- International travel is the most common cause of infection with an antimicrobial-resistant strain of typhoid fever among patients in the United States, a new study finds.
About 300 cases of typhoid fever are reported in the United States each year, and the majority of these cases are associated with foreign travel, especially to India, Pakistan and Bangladesh. Over the last 20 years, the emergence of Salmonella serotype Typhi strains resistant to antimicrobial drugs has complicated the treatment of patients in the United States, according to researchers at the U.S. Centers for Disease Control and Prevention.
The CDC team studied data on 1,902 people, median age 22, treated for typhoid fever in the United States between 1999 and 2006, and examined the test results of 2,016 Salmonella Typhi samples submitted to the CDC for analysis.
The researchers found that 1,295 (73 percent) of the patients were hospitalized and three (0.2 percent) died. They also found that 1,439 (79 percent) of the patients had traveled overseas within 30 days before they became ill, and only 58 of the travelers (5 percent) had received typhoid vaccine.
Three countries accounted for more than two-thirds of all travel-associated cases of typhoid fever -- India (47 percent), Pakistan (10 percent) and Bangladesh (10 percent).
The study appears in the Aug. 26 issue of the Journal of the American Medical Association.
The researchers also found that "272 [13 percent] of 2,016 isolates tested were resistant to ampicillin, chloramphenicol and trimethoprim-sulfamethoxazole [multidrug-resistant S. Typhi]; 758 [38 percent] were resistant to nalidixic acid [nalidixic acid-resistant S. Typhi [NARST]], and 734 NARST isolates [97 percent] had decreased susceptibility to ciprofloxacin. The proportion of NARST increased from 19 percent in 1999 to 54 percent in 2006," Dr. Michael F. Lynch, of the CDC, and colleagues wrote in a news release from the journal.
Resistant infections were most likely to occur in patients who had traveled to the Indian subcontinent. These patients accounted for 85 percent of multidrug-resistant S. Typhi infections, 94 percent of nalidixic acid-resistant infections and 44 percent of susceptible infections, the researchers noted.
"Since most typhoid fever among patients treated in the United States is acquired abroad, ongoing surveillance may also help track global patterns of antimicrobial resistance of S. Typhi. Reducing the burden of typhoid fever in the United States will require increased attention to prevention measures by travelers, including improved vaccination coverage among travelers to typhoid-endemic areas," the authors concluded. "Further reductions in typhoid fever among travelers will depend on increased availability of safe drinking water as well as improved sanitation and food hygiene in typhoid endemic areas, measures that would go a long way toward reducing the global burden of typhoid fever."
The CDC has more about typhoid fever.
-- Robert Preidt
SOURCE: Journal of the American Medical Association, news release, Aug. 25, 2009
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