Emerging Multi-Drug Resistant Salmonella

| October 20, 2011 | 0 Comments

The threat of salmonella infections has existed for more than a century as they are some of the most widely spread food-borne diseases. For several countries Salmonella has been a significant health burden—infecting millions and killing thousands worldwide. One of the most prevalent strains is Salmonella enterica, which is the cause of major foodborne illness that is responsible for acute gastroenterisis. Though this illness in general has been on the decline, several serotypes of S. enterica are emerging. The recent emergence of S. enterica serotype Kentucky (S. Kentucky) garners attention because of its distinctive multi-drug resistant characteristics and its international spread.

Salmonella cells isolated from macrophages. Image courtesy of EMSL, a U.S. Department of Energy national scientific user facility (www.emsl.pnl.gov).

S. Kentucky was first reported in Egypt in the 1990s, but has greatly expanded in the last few years.  As of 2006, research led by Drs. Francois-Xavier Weill and Simon LeHello has indicated that S. Kentucky has spread into countries throughout Africa and the Middle East, and even into parts of Europe. Moreover, S. Kentucky cases continue to escalate in these regions; three cases in 2006 have increased to174 cases in 2008 in France, England, Wales, and Denmark.[1] Research also indicates that the primary agent is poultry, raising concerns about food production. As Craig W. Hedberg notes, “contaminated food ingredients could result in contamination of animal feed as well as human food.”[2]

S. Kentucky’s high resistance to several common antibiotics, including ciproflaxin—a major antibiotic in Salmonella treatment—is a strong indication of the unregulated use of antibiotics. As Dr. Weill states in the journal Infectious Disease News, “use of fluoroquinolones for the empirical treatment of severe human nontyphoidal salmonella infections should be carefully weighed and eventually guided by the antimicrobial susceptibly testing.”[3] Because different strains of Salmonella have different susceptibilities, careful attention to monitoring antibiotics is necessary.[4] To reduce the excessive use of antibiotics, it is critical to take measures such as more frequent, controlled inspections and better hygiene in the production and processing of poultry.[2] Consumers must also minimize their risks by thoroughly cooking poultry products.[5] Awareness and education on all levels in identification and handling of food are necessary. Collaboratively, all stages within the food production and processing industry should combine efforts to monitor antibiotics and bacteria in order to prevent contamination and drug-resistant bacteria.

Not only nationally, but internationally, countries must cooperate to prevent the relative spread of Salmonella to both neighboring and distant countries. According to Hedberg, “timeliness of public health surveillance is the key to implementing effective control measures.”[2] Countries must maintain regular public health surveillance by testing isolates for antimicrobial sensitivity and phage typing. By sharing data from national public health surveillance and risk assessment, the contamination of Salmonella enterica can be recognized earlier and farmers and producers will be better prepared to respond.[2] Consistent with the notion of public health surveillance, the World Health Organization has implemented a program, the Global Salm-Surve programme, which enables countries to “develop capacities to detect antibiotic-resistant pathogens, including salmonella…”.[5]

Although relative to other infectious diseases, Salmonella enterica has few cases, the emergence of a drug-resistant bacteria and its rapid international spread over a couple of years have raised a sense of urgency to prevent a more threatening drug-resistant bacteria from emerging and unleashing a pandemic.


[1] Le Hello, Simon, Rene S. Hendriksen, Benoît Doublet, Ian Fisher, Eva Møller Nielsen, Jean M. Whichard, Brahim Bouchrif, Kayode Fashae, Sophie A. Granier, Nathalie Jourdan-Da Silva, Axel Cloeckaert, E. John Threlfall, Frederick J. Angulo, Frank M. Aarestrup, John Wain, and Franxcois-Xavier Weill. “International Spread of an Epidemic Population of Salmonella enterica Serotype Kentucky ST198 Resistant to Ciprofloxacin.” Journal of Infectious Diseases, 204 (2011): 675-684.

[2] Hedberg, Craig W. “Challenges and Opportunities to Identifying and Controlling the International Spread of Salmonella.” Journal of Infectious Diseases,  204 (2011): 665-666.

[3] DeNyse, Ashley. “Multidrug-resistant Salmonella strain spread internationally.” Infectious Disease News. 1 Sep 2011.

[4] Tauxe, Robert V. “Emerging Foodborne Diseases: An Evolving Public Health Challenge.” Emerging Infectious Diseases Vol. 3, No. 4, (1997): 425-434.

[5] World Health Organization. Department of Food Safety. “Drug-resistant Salmonella.” 2005.

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