In the United States, there has been an increase in cases of typhoid fever resistant to the drugs most commonly used against the illness, federal health officials reported Tuesday.

U.S. cases of typhoid fever are closely linked with foreign travel, most often to the Indian subcontinent (India, Pakistan, and Bangladesh), Dr. Michael F. Lynch and colleagues from the Centers for Disease Control and Prevention (CDC), Atlanta report in the Journal of the American Medical Association.

Typhoid fever is a potentially life-threatening bacterial infection that is usually acquired by eating contaminated food or drinking contaminated water. The illness is characterized by high fever, abdominal pain, fatigue, loss of appetite and rose-colored spots on the skin.

In the US and other industrialized nations, typhoid has been nearly eliminated. In developing countries, typhoid remains a serious health threat.

Lynch and colleagues reviewed data from 1999 to 2006 for 1,902 cases of typhoid fever reported to the CDC. Most of these cases involved relatively young adults who had to be hospitalized. Three patients died.

Foreign travel within 30 days of illness - mostly to India, Pakistan, and Bangladesh - was reported by 79 percent of those with typhoid fever. Together, these three destinations accounted for more than two-thirds of all travel-associated cases of typhoid fever.

Only 58 travelers, or 5 percent, who came down with typhoid fever had received typhoid vaccine, the CDC team found.

In last two decades, drug-resistant strains of the organism have emerged, which is generating growing “concern,” Lynch and colleagues note.

Among 2,016 “Typhi” samples sent to the CDC by U.S. public health laboratories for testing, 13 percent were resistant to the antibiotics ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole.

Thirty-eight percent of samples tested were resistant to an older antibiotic called nalidixic acid and the vast majority of these samples were not very susceptible to the killing power of the antibiotic ciprofloxacin.

The proportion of nalidixic acid-resistant typhoid samples seen in the U.S. increased from 19 percent in 1999 to 54 percent in 2006, the researchers report.

“Although this older antibacterial is rarely used for treatment, resistance to nalidixic acid can be a marker for decreased susceptibility to fluoroquinolones,” the most commonly used antibiotics in North America and Europe, they point out.

“Reducing the burden of typhoid fever in the United States,” Lynch and colleagues conclude, “will require increased attention to prevention measures by travelers, including improved vaccination coverage among travelers to typhoid-endemic areas,” particularly among travelers visiting friends or family in India or its neighbors.

“Further reductions in typhoid fever among travelers,” they add, “will depend on increased availability of safe drinking water as well as improve sanitation and food hygiene in typhoid endemic areas, measures that would go a long way toward reducing the global burden of typhoid fever.”

SOURCE: Journal of the American Medical Association, August 26, 2009.