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Listen to this siteThursday 16 February 2006
This research project will use the typing method MLST to compare Scottish campylobacter isolates from human infections with those from food and environmental sources.
Study Duration : June 2005 to November 2007
Contractor : University of Aberdeen
Despite the worldwide importance of campylobacter as an enteric pathogen, much remains to be understood about its epidemiology and associated risk factors. A greater understanding of this area is vital for the development of effective control programmes to reduce human campylobacter infection.
The Advisory Committee on the Microbiological Safety of Food (ACMSF) 2nd Report on campylobacter recommended that the Agency considered MLST in its future investigative programmes to improve the epidemiological study of campylobacter over the next few years.
A greater understanding of the epidemiology and associated risk factors of Campylobacter as an enteric pathogen is vital for the development of effective control programmes to reduce human Campylobacter infection.
In its 2nd Report on Campylobacter, the Advisory Committee on the Microbiological Safety of Food (ACMSF) recommended that the Agency considered using multilocus sequence typing (MLST) in its future investigative programmes to improve the epidemiological study of Campylobacter over the next few years. This project aimed to identify epidemiological links and sources of infection. It also examined the population genetics of Campylobacter.
Clinical Campylobacter isolates obtained from the Scottish NHS diagnostic laboratories over a 15-month period were typed using MLST. These were compared with the MLST profiles from more than 1000 food and environmental isolates collected over the same period throughout Scotland. This represents the world’s largest national-scale contemporaneous comparison to date of Campylobacter strain types from clinical cases and a broad range of environmental and food sources of infection. The resulting MLST profiles were analysed and compared with other published profiles in order to identify epidemiological links and sources of infection.
A highly diverse range of MLST profiles were observed across all of the clinical, food and environmental isolates analysed in the study. Comparisons of the MLST profiles of clinical Campylobacter isolates with those of food and environmental isolates identified retail chicken as the single largest source of Campylobacter infection in Scotland. This is consistent with published findings on the prevalence of Campylobacter in broiler chickens and the significance of chicken consumption as a risk factor in clinical Campylobacter infection. The findings suggested that farm ruminants could also be a source for Campylobacter infection in Scotland, although the routes for infection via these sources are not yet understood. Further analyses were conducted on clinical MLST profiles in order to assess the levels of strain diversity and spatio-temporal clustering of human Campylobacter cases during the 15-month period of the study. The diversity of strain types was spread across Scotland and there was no indication of particular strains being more common in some regions than in others. Isolates from cases that were already known to be linked (outbreaks) were found to be of the same strain type, but more generally only a small proportion of isolates were clustered, with the majority of clinical cases that occurred during the period of the study apparently being sporadic.
This research has served to underline the importance of intervention strategies targeted to the broiler food chain in reducing the rates of infection in the Scottish population. It has also highlighted the need for further work to elucidate the significance of farm ruminants and potential exposure routes via these sources for infection in humans.
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