As part of an international study, researchers at the Institut Pasteur, the INRA and the French Institute for Public Health Surveillance have tracked the emergence of a Salmonella strain that has developed resistance to almost every possible antibiotic treatment.
The study has retraced the evolution of the bacteria throughout the last 50 years. It has determined the chronology for the appearance of different resistances, decrypted the bacteria’s mechanisms and identified poultry to be the main vector of the strain.
Epidemiological data collected for the study has enabled researchers to track the explosion of the bacteria in real time starting from 2006. Between 2002 and 2008, 500 cases overall were recorded in France, the UK and Denmark. For France alone, between 2009 and 2010, 270 cases were confirmed. Furthermore, the contamination zone, initially limited to East and Northeast Africa, has progressively spread to North and West Africa, as well as to the Middle East.
The researchers’ observations seem to indicate that Egypt may be the geographical birthplace of the three steps of emergence of antibiotic resistance. It is there that all of the genetic modifications at the source of these resistances were identified for the first time.
Researchers consider that Salmonella Kentucky probably acquired the DNA fragment responsible for the first resistances via aquaculture systems. The widespread use of antibiotics in farming in Egypt since the early 1990s appears to have favored the natural selection of bacteria strains with this antibiotic resistance. The recent explosion of cases would then be linked to the spread of the bacteria in Africa within the poultry industry, a major consumer of flouroquinolones. The accumulation of all these resistances on the same strain of Salmonella Kentucky would therefore appear to be the source of the current epidemic.
The results of the study underline the importance of microbiological monitoring on both national and international levels, the researchers say, in particular in southern countries. They are a reminder of the public health risks on non-regulated use of antibiotics in farming that promotes the appearance and spread of resistant genes in bacteria responsible for food borne infections.