Antibiotic resistance among species of Salmonella remains an extremely rare phenomenon in Canadian health, but it’s a “growing concern” worth monitoring, according to a new study led by researchers at the Public Health Agency of Canada published in the June 2013 edition of Emerging Infectious Diseases. The resistant strains also do not appear to be coming from food sold in Canada, but are instead brought back with Canadians who travel to Africa.
Between 2003 and 2009, Canadian health agencies collected a total of 76 samples of a Salmonella serotype known as Salmonella Kentucky from people who had fallen ill and sought medical attention. Out of those samples, 23 (or 30 percent) were resistant to ciprofloxacin, a fluoroquinoline antibiotic and the fifth most commonly prescribed antibiotic for humans in the United States.
Those 23 Salmonella Kentucky isolates, as it turned out, made up 66 percent of the 35 ciprofloxacin-resistant strains of Salmonella analyzed during that time period. Worth noting, however, is that health labs performed susceptibility testing on 21,426 nontyphoidal Salmonella isolates during the six-year period, meaning ciprofloxacin resistance was present in 0.16 percent of samples.
On a positive note, no ciprofloxacin-resistant strains have been found in Canadian retail meat samples, and no cases of ciprofloxacin-resistant Salmonella infections have yet been reported in the U.S.
Ciprofloxacin resistance in Salmonella does not touch on the issue of non-therapeutic use of antibiotics in animal feed, either, as veterinary fluoroquinolines are only legally prescribed to treat respiratory infections in cattle and swine. The study’s lead author, Dr. Michael Mulvey, told Food Safety News that his agency has seen no evidence that ciprofloxacins are being used for non-therapeutic purposes in agriculture animals.
So, where are these resistant cases coming from?
Of the 23 cases of resistant Salmonella infection monitored, researchers were able to track down the travel histories of 11 patients. Each patient, as it turned out, had traveled to an African country within a week of developing symptoms.
Similar ciprofloxacin-resistant cases have cropped up across Europe after travel to countries such as Morocco, Egypt and Libya.
The Canadian study did not look into the use of ciprofloxacins in African agriculture.
Many of the ciprofloxacin-resistant strains were also resistant to other classes of antibiotics, further complicating treatment options, Mulvey said.
Though the issue of ciprofloxacin-resistant Salmonella appears to be more of an African problem for the time being, Canada has had experience with antibiotic-resistant Salmonella getting into food in the past.
In 2003, Quebec began seeing a resistance to cephalosporin develop in strains of Salmonella Heidelberg in humans linked to poultry and retail chicken meat. The Quebec broiler industry decided to voluntarily cease use of cephalosporins on chickens in 2005, which led to a “dramatic decrease” in rates of resistance, the study said.
“Once bacteria become resistant, the drugs used to cure the bacterial infection no longer work or are less effective,” Mulvey said. “In addition, the lack of new antibiotics in development is of serious concern.”© Food Safety News