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health & nutrition
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the following request went to Vegetarian Society members in February 2000, the initial report is below.
Volunteers needed for study: faecal spread of antibiotic resistant bacteria Jon Caplin of the Environment & Public Health Research Unit at the University of Brighton has asked us to help him find volunteers for his study of the spread of antibotic-resistant bacteria. They wish to test the hypothesis that these bacteria can spread to the human gastro-intestinal tract from meat products. To do this, they need to examine the stools of meat-eaters, vegetarians and vegans to test for the presence or absence of these bacteria. Volunteers would need to provide one sample of fresh faeces, anonymously. The only information required from volunteers is their age, sex, length of time vegetarian/vegan and whether they ever handle any meat products (eg for non vegetarian family members or as part of their job). Sampling pots, instructions and postage boxes will be provided. If you are interested in taking part in this study, please contact Jon Caplin on 01273 642675, fax: 01273 642285, email: j.l.caplin@bton.ac.uk
Epidemiology and ecology of antibiotic resistant enterococci in the food chainBackground Enterococci are bacteria that are ubiquitous in the intestinal tract of humans and animals, and are released into the environment from faecal materials and via fertilisers of animal and human origin. They have been isolated in high numbers from plants, soil and water. One important characteristic of this genus of bacteria is their resistance towards chemical and physical stress, and, in contrast to other faecal bacteria that are released into the environment e.g. Escherichia coli enterococci can survive for long periods outside their natural intestinal hosts. There are approximately twenty enterococcal species, the most clinically relevant being E.faecalis and E.faecium, which often exhibit high levels of antibiotic resistance. The enterococci are frequently associated with nosocomial infections (i.e. acquired in the hospital setting) and have been described as "the nosocomial pathogen of the nineties". Enterococci are often resistant towards most antibiotics in clinical practice, except for the glycopeptide antibiotic vancomycin that has been regarded as the ultimate treatment of enterococcal infections. Recently, strains of enterococci resistant to vancomycin (VRE) have been isolated and, have become increasingly common in European and American hospitals. Recent studies have shown that healthy humans may carry highly vancomycin-resistant enterococci and VRE have also been isolated from farm animals, uncooked meats and poultry, sewage, and, dogs and cats. Typing of such isolates have shown them to be heterogeneous, belonging to several clones but they all carried the same resistance gene complex, named vanA. It has been shown that humans and animals often carry their own strains of enterococci, leading to a high diversity beyond the species level. The source of VRE is as yet unknown. Several reports have suggested that the high occurrence of vanA enterococci could be associated with the use of the vancomycin-related glycopeptide avoparcin in animal husbandry as a growth promoter. It has been postulated that avoparcin might have selected for enterococci with high level glycopeptide-resistance, and might thus have increased the reservoir of resistance genes in the environment. However, the spread of VRE from the hospital environment to the food chain has also been suggested to be the origin of these resistance strains. Evidence that's supports the former view is that vancomycin-resistance has not been observed in countries where avoparcin has not been used for many years. Enterococci also have the ability to exchange genes in vivo, not only with other enterococci, but also with other bacteria, such as Listeria spp., Campylobacter spp. and E.coli. Even though enterococci are not considered as highly pathogenic organisms, the possibility that they may transmit their resistance genes to other, more pathogenic bacteria is worrying. One of the worst scenarios now anticipated is the transfer of the vanA gene to the multi-resistant Staphylococcus aureus (MRSA), for which vancomycin is regarded as the ultimate treatment - this has already been shown to occur in laboratory experiments. More knowledge about the epidemiology and ecology of enterococci is required. Within the EU, avoparcin use was recently suspended until further evidence about its possible role in selecting for VRE is gained. However there is still concern that the numbers of VRE will increase. The fear of the dissemination of VRE through the use of fertilisers or composts of animal and human origin could lead to a backlash against modern recycling policies, therefore we need to know more about the fate of enterococci that are spread in the environment through sewage or natural fertilisers such as animal faecal-slurry. Some of the questions as yet unanswered include: can enterococci and VRE be transmitted to humans by the ingestion of vegetables and, by the handling and undercooking of raw meats?; do VRE belong to a few clonal groups or can resistance be transmitted by any enterococcus strain?; do some strains colonise both humans and animals?; can VRE from animals colonise humans? Programme of Work Within the framework of the project we will, through a careful typing and resistance determination of a large number of enterococci from different sources, and from different countries within the EU, try to answer the following questions:
Preliminary Results
Conclusions So far, the project has generated preliminary data on 1527 samples, collected in different geographical regions and from different links of the food chain, as well as a carefully characterised strain collection. The project has also resulted in a co-operatively produced protocol for sampling and analysis of enterococci in the environment and in animals, as well as a culture collection consisting of well characterised isolates from different origins. These isolates represent both normal enterococcal floras in the samples, and the vancomycin resistant floras, and will be a valuable reference material for future investigations. During the second project year, the main tasks in the project have been sampling and preliminary phenotyping of enterococci (PhP typing), using protocol that was created in during the first project year. The common culture collection of enterococcal strains is in the process of being built up and is maintained at Brighton. Some analysis on the saved isolates have also been imitated (species identification, MIC determination [degree of antibiotic resistance], PFGE typing [genetic fingerprinting]). Finally the project has so far resulted in the development or adaptation of methods for identification and typing of enterococci, for resistance gene characterisation, and a protocol for MIC determination of enterococci. The project is now more than half-ways through, and a majority of the cumbersome sampling part has been done and a large amount of data has been generated. The work during the third project year will be concentrated on analysis isolates that have been stored in our culture collections (species identification, PFGE typing, MIC determination, characterisation of resistance genes) and on writing up manuscripts and reports.
Jon Caplin More information will be available soon on: |