The WHO have a useful factsheet on food safety and foodborne illness (factsheet).
See Food poisoning micro-organisms for more details on specific organisms.
Food poisoning statistics
The general public perception of food poisoning numbers is that outbreaks and numbers of cases are increasing at an alarming rate. Whereas in fact the numbers of cases due to Salmonella and E. coli O157 has been decreasing in recent years, whilst Campylobacter and viral agents of gastroenteritis have remained relatively constant. [Reference: Anon (1999d) Where have all the gastrointestinal infections gone? Eurosurveillance Weekly] Why? Is there a difference between the two groups?
My personal view point is that possibly the message of cooking food thoroughly is being better implemented, hence the decrease in incidences of food poisoning bacteria associated with improperly cooked foods. In contrast, the message of cross-contamination has not received such an emphasis. Organisms such as Noroviruses do not multiply on food, but are transmitted via food. Campylobacter jejuni is easily killed during cooking and is not a sporeformer. However it has a low infectious dose and is associated with cross-contamination. The infectious dose and probability of infection (Pi) infectivity of major food poisoning organisms are covered on pages 357-60, 365-8, and 403.
If the message of the dangers of cross-contamination is not being properly addressed, then what changes should be made in food handling, both in industry and in the home?
If the message of the dangers of cross-contamination is not being properly addressed, then what changes should be made in food handling, both in industry and in the home? There is an 'International Scientific Forum on Home Hygiene' (IFH) which promotes a better understanding and control of home hygiene.
There is a need for better home hygiene education. The IFH (International Scientific Forum on Home Hygiene) is dedicated to raising the awareness of the role of domestic hygiene in the prevention of infections acquired in the home, and regards this as an important topic which has been largely neglected and under-researched. Their homepage can be found at Home Hygiene.
Accuracy of data around the world
We have already seen the variation in food poisoning statistics collated around the world (Table 1.12, p 30) and contrasted with the sentinent studies of the USA (Table 1.6, p 11-12) and the UK (Table 1.5, p 10). The variation is due to under-reporting (Table 1.8 and Fig. 1.6) and also the variation in approved methods [See chapter 5 for the approved detection methods for the major food poisoning organisms in in UK, USA, Spain, France, Australia, Canada, etc.]. A useful source of outbreak statistics is Foodborne illness education centerand a weekly summary of food safety alerts in Europe is listed here. For an extensive web site resource on all forms of food poisoning (ie. chemical as well as microbial) go to the FAO site for the Pan-European conference in 2002.
The standardisation of methods will greatly assist in obtaining a truer reflection of the incidence and epidemiology of food poisoning in the general population. The European Enter-Net and American FoodNet (and associated Pulse-Net, also recent PulseNet article) are examples of effective surveillance programmes. See Table 1.13 (p33) for examples of Enter-Net identified outbreaks in Europe.
One of the interesting observations on food poisoning statistics is the seasonality, with certain agents of gastroenteritis being more prevalent during the summer. A recent article in Emerging Infectious Diseases investigates this phenomenon.
For the most recent data on European foodborne illness (1993-1998) go to the World Health Organisation, as well as the European WHO food safety page (then go to 'Surveillance'), and here for USA food poisoning statistics 1993-1997.
A criticism of the CDC data collection can be found Center for Science in the Public Interest
The education of children and adults
From Figures 1.1 (p. 5) you will see the significant differences in faecal isolations of gastroenteritis organisms with age. Evidently children have a highly incidence of viral gastroenteritis than adults. See also Table 1.8 for the under-reporting values for viral pathogens. Also from Figure 1.2 (p. 6) it appears that boys (even pre-school age) have higher incidence of organisms causing gastroenteritis in their faeces than girls. Why? Is this associated with toilet training and washing ones hands? See Useful sites for a conference presentation (April 2000, PDF file) on food hygiene education and the general public.
The importance of hand washing is often emphasized as a major barrier to the spread of foodborne infectious diseases. Two articles in [Larson(1) and Pittet,2]Emerging Infectious Disease discuss its merits.A general fact sheet is also available [here].
There are a number of 'emerging' or 're-emerging' pathogens such as prions, Mycobacterium paratuberculum, Cronobacter spp. (Enterobacter sakazakii) and Arcobacter butzleri.. There are a number of reasons for their 'emergence' such as greater awareness and improved detection methods. The Institute of Food Technology has published an expert report on 'Emerging Microbiological Food Safety Issues: Implications for control in the 21st Century' . This 107 page document is an invaluable resource as an overview of current issues in the food industry. Another article on emerging pathogens in the UK can be accessed here, and a WHO factsheet here
Bacteria produce a range of toxins which vary in their specificity and heat stability. Toxins such as those from St. aureus are resistant to denaturation at cooking temperatures. Therefore it is important to avoid to growth of these organisms to levels which produce significant toxins (ie 106 St. aureus/g) prior to cooking.
- Bacterial protein proteins
- Bacterial toxins; Friends or foes?
- E. coli, Salmonella and Shigella protein toxins
- Bacterial endotoxin
- Campylobacter and Guillian-Barre syndrome
This is covered in more detail in chapter 2 (Section 2.3) of 'The Microbiology of Safe Food'.
The increasing concern over antibiotic resistance has continued. A relatively recent issue of Eurosurveillance (6 Number1, January 2001) has a number of articles on this matter. A general overview of the mechanisms causing antibiotic resistance can be read here (Scientific American article). A network focused on reservoirs of antibiotic resistance can be accessed at ROAR Network. The WHO have 2 factsheets on the topics factsheet 1 on human antibiotic usage and factsheet 2 on non-human antibiotic usage.
When an outbreak occurs, it needs to be investigated in a thorough, standardised manner. For a tutorial on this topic visit the CDC web page outbreak toolkit.