Our Research
For many years we have been working on various detection methods for common and emergent foodborne pathogens such as Campylobacter, Salmonella, Listeria, Yersinia enterocolitica and more recently Cronobacter spp. (Enterobacter sakazakii), ranging from chromogenic agars, immunomagnetic separation and also hygiene assessment via ATP swab techniques. Our studies range from food hygiene and HACCP implementation in industry, through detection methods, to genetic manipulation of common pathogens, and virulence studies with mammalian cells cultures. Mirobial diversity is addressed through various techniques; 16S rDNA, 7 loci MLST, microarray and more recently whole genome sequence analysis. Please look at the 'Publications' page to see some of the outputs from our work.
Methods Development
The gold standard for so many detection methods remains the agar plate. Our work has helped develop a number of agars and broths for use within industry. Our emphasis has been on chromogenic agars (ie. DFI) because of their potential for discriminating target organisms within a mixed flora on an agar surface. We also helped develop and validate the immunomagnetic separation techniques for Salmonella and Listeria, as well as improvements for the ATP swabs which overcome the problems of detergent residues. Genotyping including 16S rDNA sequence analysis is used to ensure a diverse range of well characterized strains is used in all method developments.
Cronobacter spp. (Enterobacter sakazakii)
This is an emergent pathogen that is primarily associated with infant infections including necrotising enterocolitis, bacteraemia and even meningitis. However infections occur in all age groups. The organism is ubiquitous and has been isolated from foods, environment and clinical sources. Many, but not all infant cases have been linked to the ingestion of rehydrated infant breast milk substitutes; commonly referred to as powdered infant formulas, PIF. Our latest work for the UK Food Standards Agency was released on their web site (FSA) in December 2009. Our most recent (2010) publication is in collaboration with Mike McClelland and Sandy Clifton on the genome sequence of C. sakazakii and its comparison with other Cronobacter species. (PLoS ONE)
It should be noted that not all strains of Cronobacter produce a yellow pigment, nor grow well at 45C and therefore could be missed when using some detection methods. Through the support of Oxoid we developed a chromogenic agar (Int. J. Food Microbiol. 2004) that was subsequently marketed as Druggan-Forsythe-Iversen (DFI) agar (Oxoid product code CM1055). We are also working on the virulence of the organism, improved isolation methods and phylogenetic relationships. Early studies using 16S & hsp60 sequencing showed that isolates identified by commonly used biochemical kits as 'E. sakazakii' were probably more than one species (see paper in J Clin. Microbiol. 2004).
The team has twenty-seven papers published on the subject, including a risk profile in Trends in Food Science and Technology (2003). The article in Maternal and Child Nutrition (2005) was voted paper of the month by Unicef. Plus, more recently the genome sequence of C. sakazakii BAA-894 and microarray analysis of the genus was published in PLoS ONE (2010). We have also published a detailed account of a neonatal intensive care unit outbreak J. Clin.Microbiol. 2007, and recently on the bacterial colonisation of nasogastric enteral feeding tubes in neonatal intensive care units (BMC Inf. Dis. 2009). Additionally, we have recently published a 7 loci multilocus sequencing typing scheme (MLST) for C. sakazkaii and C. malonaticus using strains from a range of sources in BMC Microbiology 2009 which revealed a strong clonal nature. The MLST scheme is openly available at http://PubMLST.org/cronobacter.
Prof Steve Forsythe was participant in all three FAO-WHO risk assessment workshops; February 2004 (Geneva), January 2006 (Rome) and July 2008 (Washington).
See 'Publications' for a full listing of papers, and conference presentations.
Campylobacter and related organisms
Campylobacter jejuni is recognised as the major cause of foodborne bacterial gastroenteritis. Yet its virulence mechanisms are still poorly understood. Dr Gina Manning is working on the genetics of hyperinvasion strains.
Arcobacter butzleri and related species are emergent pathogens. A. butzleri is a recognised veterinary pathogen, and is found in the food chain. There have been a few human cases of gastroenteritis due to this organism, but clear epidemiological evidence is still sparse. Regretfully this is partly due to the lack of general awareness and use of appropriate selective media. We are working in conjunction with University of Northampton, on the virulence and persistence of the organism.
Yersinia enterocolitica
Yersinia enterocolitica is another understudied bacterial pathogen. Based on US data from FoodNet, Y. enterocolitica is a relatively infrequent cause of diarrhoea and abdominal pain; approximately 1 case per 100,000. However this is probably an underestimate of its occurence. Infection is most often caused by the ingestion of contaminated food, especially raw or undercooked pork products. Dr Alan McNally studies this organism with respect to the evolution of bacterial virulence in conjunction with the Sanger Centre.
Food Surveys
The presence of foodborne pathogens in the food chain is very important in microbial risk assessment. We have undertaken a number of surveys for particular pathogens which serve the dual purpose of assessing the organisms' presence in foods, and also determining the efficacy of novel detection methods being developed. Linked to this are the studies into food hygiene and HACCP implementation in the food industry, particularly small companies. These have largely been published in refereed journals, though further work has been undertaken on consultancy basis.
Other work
We have used bacteriophage as indicators of possible enteroviruses and there removal during water purification. Overall they are potentially very indicative of the possible presence of Noroviruses (formerly small round structured viruses, or Norwalk-like viruses) which cannot be grown using current tissue culture methods.
