Study: Salmonella increases resistance to two key antibiotics

Resistance to two key antibiotics used to treat severe infections with Salmonella is becoming more common in the United States, according to a new study from the Centers for Disease Control and Prevention.

Between 1996 and 2009, the proportion of tested Salmonella isolates nonsusceptible to ciprofloxacin increased from 0.4 percent to 2.4 percent and the percentage of isolates resistant to ceftriaxone rose from 0.2 percent to 3.4 percent. In positive news, the researchers determined that the ratio of Salmonella isolates resistant to three or more antibiotics dropped from 17 percent to 9.6 percent during the same period, mostly because of a decline in resistance in the Typhimurium serotype, CIDRAP News reports.

Fluoroquinolone antibiotics like ciprofloxacin are typically used as first-line treatment for adults with severe salmonellosis and ceftriaxone is used for children with similar cases.

The CDC conducted the tests as part of the National Antimicrobial Resistance Monitoring System, which is a collaborative effort of the CDC, state health departments, the U.S. Department of Agriculture and the Food and Drug Administration.

"(Drug resistance in Salmonella) is predominantly a consequence of antimicrobial use in food animals," the researchers said, according to CIDRAP News. "(Reducing the nontherapeutic use of antimicrobials in farm animals) and other approaches are needed to prevent the emergence and spread of resistant Salmonella in food animals and transmission to humans."

The CDC estimates that nontyphoidal Salmonella affects 1.2 million people in the U.S. each year, causing 23,000 hospitalizations and 450 deaths, CIDRAP News reports.