Campylobacter Genotyping to Determine the Source of Human Infection

Autor: Marian MacRae, Iain D Ogden, John F. Dallas, Daniel J. Wilson, Daniel Falush, Norval J. C. Strachan, Noel D. McCarthy, Fraser J. Gormley, Samuel K. Sheppard, Martin C. J. Maiden, Ken J. Forbes
Rok vydání: 2009
Předmět:
Popis: Campylobacteriosis, caused principally by Campylobacter jejuni and Campylobacter coli, is among the main causes of bacterial gastroenteritis worldwide. In developing countries, campylobacteriosis is primarily a disease that occurs during infancy, because of high levels of early exposure and acquired immunity [1], but in industrialized countries, the epidemiology is characterized by sporadic infection throughout the population at all ages [2]. Campylobacter infection accounts for an estimated 2.5 million cases in the United States and >340,000 cases in the United Kingdom each year [3, 4], which is >3 times the number of cases caused by Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes combined [5]. The estimated annual economic burden of Campylobacter infection is £500 million in the United Kingdom [6] and $8 billion in the United States [7], but despite its significance as a public health problem, the relative contributions of different sources of infection to the human disease burden remain uncertain. Many species of wild and farm animals, particularly birds, carry Campylobacter species as part of their gut microbiota, and contamination of human food can occur at any point from the farm to the consumer. Potential sources of human infection include contaminated meat, poultry, water, and milk and contact with animals [8]. Analytical epidemiology methods, including risk assessment and case-control studies, provide some indirect evidence for the origin of disease, but because the majority of human Campylobacter infections are sporadic with very few recognized outbreaks that indicate a common infection source [9, 10], these approaches are incomplete. Because interventions for controlling Campylobacter transmission are costly and implementation requires consideration of cost-effectiveness, the uncertainty regarding the sources of human infection has inhibited effective public health intervention by government agencies and industry. Molecular typing has enhanced many epidemiological studies, including the identification of food-borne outbreaks of infection due to E. coli O157:H7 [11], Salmonella enterica [12], Campylobacter [13], and L. monocytogenes [14]; early identification of an outbreak source enables effective disease containment [14, 15]. Recent advances in bacterial genetic typing and analysis provide the opportunity to determine the origin of Campylobacter isolates obtained from patients on the basis of their genotypes, because there is sufficient genetic variation within the bacterial population to define host or source-associated genotypes [16]. In this study, we used multilocus sequence typing (MLST) [17], which has several advantages over other microbial typing schemes such as serotyping, PFGE, and flaA typing [18-20]. Because it is based on nucleotide sequence, MLST is inherently reproducible, scalable, and portable between laboratories, with data readily shared via the Internet [21]. We addressed the sources of campylobacteriosis in industrialized countries as part of the national Campylobacter MLST Project in Scotland (CaMPS), which included a comprehensive survey of isolates from all confirmed cases of human campylobacteriosis in Scotland during a 15-month period (from mid-July 2005 through mid-October 2006). To attribute isolates to a source, 4 important resources were exploited: (1) a standardized MLST genotyping protocol, (2) a national-scale contemporaneous comparison data set of MLST genotypes from potential disease sources in Scotland, (3) a substantial data archive of MLST genotypes from other sources and locations, and (4) model-based statistical methods that allow quantitative estimation of the genetic attribution of disease to source.
Databáze: OpenAIRE
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