A new salmonella strain highly resistant to the ciprofloxacin, the main antibiotic used to treat infections with the bacteria, is increasing in prevalence, researchers warn.

In some cases isolates of the bacteria Salmonella enterica serotype Kentucky, have been resistant to multiple antibiotics, including amoxicillin, streptomycin, spectinomycin, gentamicin, sulfamethoxazole and tetracycline – leading researchers to call these strains CIPR.

Nearly 500 cases of S. enterica Kentucky CIPR have been identified in Europe between 2002 and 2008, according to François-Xavier Weill, MD, of the Pasteur Institute in Paris, and colleagues. Health officials in Canada have also reported several cases, and contaminated imported food products have been identified in the United States, suggesting that the bacteria have spread to North America, they added.

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In 2008, 139 S. enterica Kentucky isolates were reported in France compared with just 24 to 54 annually between 2000 and 2006. Among these isolates 71.3% were CIPR.

During the same time frame, Denmark, England and Wales also reported increases in the bacteria, with CIPR accounting for 50% or more of all S. enterica Kentucky isolates identified in these countries by 2008.

Other findings are as following:

  •  A total of 489 cases of S. enterica Kentucky involving CIPR isolates were identified, increasing from just three cases reported in 2002 to 174 in 2008
  • In France, 497 S. enterica Kentucky isolates were reported, 200 of which were CIPR
  • In England and Wales, 698 S. enterica Kentucky isolates were recorded, 244 of which were CIPR
  • In Denmark,114 S. enterica Kentucky isolates were identified, 45 of which were CIPR
  • In the U.S., 679 S. enterica Kentucky isolates were reported to the CDC, but none appear to be CIPR

The researchers traced the first cases of S. enterica Kentucky to international travelers visiting Egypt between 2002 and 2005, but since 2006 travelers have also acquired the infection in various parts of Africa and the Middle East.

In about 10% of cases, international travel was not a factor, according to the researchers. In these instances, they suggested that S. enterica Kentucky infections may have resulted from consuming imported food or through some other route of secondary contamination. CIPR strains have been isolated from chicken and turkey in Ethiopia, Morocco and Nigeria, the researchers noted, implying that poultry may play an important role in the spread of S. enterica Kentucky.

“The common use of fluoroquinolones, including ciprofloxacin, enrofloxacin and ofloaxacin in chicken and turkey production in Nigeria and Morocco may have contributed to its rapid spread,” the researchers wrote. “Another potential food vehicle in Europe and the U.S. may be spices or raw vegetables imported from areas of endemicity.”

In an accompanying editorial, Craig Heberg, PhD, of the University of Minnesota School of Public Health in Minneapolis, called for improved surveillance systems, noting that variations in the way different countries report data make it difficult to monitor the outbreak accurately.

Hedberg pointed out that the percentage of Salmonella isolates submitted from clinical laboratories to national health reference laboratories ranged from 65% in France to 99% in Denmark.

“Given the medical costs and public health impact associated with the spread of multidrug resistant organisms, the potential benefits of such a system should far outweigh the costs,” Hedberg wrote.

The report and commentary, published online this week in the Journal of Infectious Diseases, comes in the midst of a U.S. salmonellosis outbreak involving contaminated ground turkey meat. The U.S. outbreak involves a different Salmonella strain, S. enterica serotype Heidlberg, and has sickened 76 and killed at least one.

Le Hello S et al. J Infect Dis. 2011; doi:10.1093/infdis/jir409.

Hedberg CW. J Infect Dis. 2011; doi:10.1093/infdis/jir392.