The new strain, called S. Kentucky, has spread internationally with almost 500 cases found in France, Denmark, England and Wales in the period between 2002 and 2008, according to the study published in the Journal of Infectious Diseases.
This comes as the U.S. Centers for Disease Control (CDC) continues to investigate the outbreak of Salmonella poisoning that spread across 26 states linked to ground turkey, and now a new strain of salmonella highly resistant to the antibiotic Ciprofloxacin surfaces, scientists say.
The U.S. Department of Agriculture is also alerting consumers, although no recall has been issued.
Salmonella infection is a major public health problem worldwide, the French researchers who led the study noted. There are an estimated 1.7 million infections in North America each year and more than 1.6 million cases were reported between 1999 and 2008 in 27 European countries.
The CDC reported that the highest number of cases have been found in Michigan, Ohio, Texas, Illinois, California and Pennsylvania. The agency reported that cases have also been found in Alabama, Arizona, Georgia, Iowa, Indiana, Kentucky, Louisiana, Massachusetts, Minnesota, Missouri, Mississippi, North Carolina, Nebraska, Nevada, Oklahoma, Oregon, South Dakota, Tennessee and Wisconsin.
Researchers examined the cases in North America and said reports of infection in Canada and contamination of imported foods in the United States suggest the new strain - called S. Kentucky - has also reached there.
On Tuesday, the Associated Press reported that the CDC and the U.S. Department of Agriculture said both agencies are "vigorously working to identify the specific contaminated product or products that are causing illnesses and will update the public on the progress of this investigation as information becomes available."
Of the cases counted by the CDC, there are 58 confirmed cases; the oldest person affected was 88 and the youngest was under one year old, with the median age of 23. On July 29, USDA-FSIS released a public health alert for frozen or fresh ground turkey products, according to the agency.
Among the 51 ill persons with available information, 25 of those, or 49 percent, reported consuming ground turkey. Cultures of four ground turkey samples purchased from four retail locations between March 7 and June 27, 2011 yielded Salmonella Heidelberg with the outbreak strain, CDC officials add.
For more details on the 77 cases, see the CDC's Salmonella Outbreak Investigations: Timeline for Reporting Cases.