Section 5: Food poisoning microorganisms

**INDEX**
ICMSF	C. jejuni	Salmonella
E. coli	S. aureus	C. perfringens
L. monocytogenes	E. sakazakii	Noroviruses
Other emergent pathogens	Bacterial and fungal toxins
Outbreaks	vCJD news	FDA Bad Bug book

ICMSF

ICMSF The International Commission on Microbiological Specifications for Foods (ICMSF 2002) has revised its previous categorisation of microbiological hazards in foods. These are tabulated below.

The severity of the illness and duration should be compared with the information on p. 142-192 in the book 'The Microbiology of Safe Food'. Additionally a number of these organisms are permitted above the 0 cells in 25 gram testing specification for ready-to-eat food. For details see the PHLS (UK) guidelines in Table 8.20, p.333 for ready-to-eat foods and the various EU and FDA sampling plans in Chapter 8. For more information on microbiological criteria jump to the relevant page microbiological criteria .

ICMSF microbiological hazards categorisation (p144, Table 5.2). For Cases see Table 8.1, p.301
Categorisation of common foodborne pathogens (ICMSF 1986)
Moderate, direct, limited spread, death rarely occurs	B. cereus, C. jejuni, Cl. perfringens, St. aureus, Y. enterocolitica, T. saginata, T. gondii	Cases 7,8,9
Moderate, direct, potentially extensive spread, death or serious sequelae can occur,. Considered severe	Pathogenic E. coli, S. Enteritidis and other salmonellae other than S. Typhi and S. Paratyphi, shigellae other than Sh. dysenteriae, L. monocytogenes	Cases 10,11,12
Severe, direct	Cl. botulinum types A,B,E and F, hepatitis A virus. Sh. dysenteriae, S. Typhi and S. Paratyphi A, B and C, T. spiralis	Cases 13, 14, 15

Up-dated categorisation (ICMSF 2002)
Food poisoning organisms causing moderate, not life-threatening, no sequelae, normally short duration, self-limiting	B. cereus (including emetic toxin), Cl. perfringens type A, Norwalk-like viruses, E. coli (EPEC, ETEC), St. aureus, V. cholerae non-O1 and non-O139, V. parahaemolyticus
Serious hazard, incapacitating but not life-threatening, sequelae rare, moderate duration	C. jejuni, C. coli, S. Enteritidis, S. Typhimurium, shigellae, hepatitis A, L. monocytogenes, Cryptosporidium parvum, pathogenic Y. enterocolitica, Cyclospora cayetanensis
Severe hazard for general population, life-threatening, chronic sequelae, long duration	Brucellosis, botulism, EHEC (HUS), S. Typhi, S. Paratyphi, tuberculosis, Sh. dysenteriae, aflatoxins, V. cholerae O1 and O139.
Severe hazard for restricted populations, life-threatenting, chronic sequelae, long duration	C. jejuni O:19 (GBS), C. perfringens type C, hepatitis A, Cryptosporidium parvum, V. vulnificus, L. monocytogenes, EPEC (infant mortality), infant botulism, Ent. sakazakii.

Campylobacter jejuni sites

Salmonella serovars

Escherichia coli sites

Staphylococcus aureus sites

Clostridium perfringens sites

Listeria monocytogenessites

Noroviruses (formerly Norwalk-like viruses and small round structured viruses), and other enteric viruses

Emergent pathogen - Enterobacter sakazakii

The reader should note that our research group is carrying out extensive research into this emergent organism. Although the primary concern with this bacterium is the association with neonatal infections, it also causes adult infections. The bacterium was previously referred at as a 'yellow-pigmented Enterobacter cloacae' This is unfortunate as recent studies have shown that ~75% of strains are non-pigmented. Hence identification methods based on pigmentation (FDA and ISO) may fail to isolate the bacterium.

See www.foodmicrobe.com and click on 'Publications' for a full up to date list of papers from our research group. These publications include:

General overview : Maternal and Child Nutrition 1:44-50 (2005). Voted UNICEF paper of the month.
A risk profile of E. sakazakii in Trends in Food Science and Technology , 11:443-454, 2003).
Development of a chromogenic agar called 'DFI' which stands for 'Druggan-Forsythe-Iversen agar'. The agar has undergone a European field trial and is being commercialised by Oxoid Ltd (UK), Code CM1055. Int. J. Food Microbiol. 96:133-9 (2004), and an appraisal of enrichment media (Appl. Environ. Microbiol. 2007).
Biofilms, growth range and thermotolerance Lett Appl Microbiol. 38:378-82 (2004)
Survey of ~500 food products for E. sakazakii using the chromogenic agar compared with FDA method (Food Microbiology 21:771-6, 2004).
Phylogenetic, and phenotypic studies: J. Clin. Microbiol. 142:5368-70 (2004), BMC Microbiology (Online) 6:28, and 6:94 (2006).
Virulence: Food Microbiol. 24:67-74 (2007)

Our detection method is two days shorter than the FDA method and is given here: DFI method flowchart

I am also on various consultative panels concerning the organism. One such contribution being the FAO-WHO Geneva meeting 2-5th February (2004),and the second risk assessment meeting in Rome 2006. The reports of both meetings are available at the WHO web site; Enterobacter sakazakii - FAO-WHO consultation.

Other emergent pathogens

Bacterial and fungal toxins

There are a number of web sites which review food poisoning bacteria. One very clear one is from the University of Illinois. For more detailed information go the the FDA Bad Bug Book which is referred to below.

Outbreaks

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. There are three case studies which can be down loaded (classroom based or computer based) from here.

BSE-CJD news

The Department of Health in the United Kingdom has released the latest figures (end of June 2002) on both known cases of CJD and cases of variant Creutzfeldt-Jakob disease (vCJD). By the end of June 2002, a total of 124 cases of variant Creutzfeldt-Jakob disease (vCJD) had been reported in the United Kingdom (DoH). A quarterly analyses is also available on the CJD surveillance unit web site. The overall median age at death was 28 (range 14-74 years). The median number of days from onset to diagnosis was 334 days and from onset to death 411 days. Of the 124 cases, 68 (55%) were male. Although only 11 cases have been diagnosed in the first six months of 2002, it is not yet possible to conclude that the epidemic is reaching or has reached its peak. A continued exponential increase at the current underlying rate will give an estimate of approximately 32 deaths in the next 12 months. Twenty-eight cases of vCJD were reported in 2000, 15 in 1999, 18 in 1998, and 10 in 1997. Analyses shows that the underlying incidence is increasing by an estimated 18% per year based on date of symptom onset, or 20% per year based on date of death. These trends are lower than the 22% and 27% estimated last November, because only 11 cases were diagnosed in the first two quarters of 2002 (Reference: Andrews).

The FDA Bad Bug book

The Food and Drug administration (USA) have a very useful web site called Bad Bug Book which has extensive information on foodborne pathogens and toxins. You will notice that the majority of information in food microbiology is concerned with bacterial pathogens, as opposed to viruses and fungi. This is partially due to the relative ease with which bacteria can be cultivated in the laboratory. The perceived rise in viral causes in food poisoning is partially due to improved detection methods. The food poisoning statistics are dominated by Salmonella serotypes and Campylobacter jejuni. However as reviewed in foodborne illness the causative organism of a considerable number of gastroenteritis cases are not identified every year.

It should also be noted that a food microbiology in industry does not, and would not be expected to examine foods for all the possible pathogens. It would be prohibitively expensive and impractical. An additional reason for restricted microbiological analysis is that unless 100% of the food is examined then one cannot be 100% certain of the absence of pathogens or toxins in the whole batch of food. Taking known numbers of samples from a batch of food can be used to give a statistical evaluation of contamination. Hence the development of microbiological criteria. However it should be remembered that the results from a microbiological laboratory make take several days (at least if an outside accredited laboratory is used). Therefore the sampled batch of food might already have been distributed and a product recall would be expensive and deter customers from purchasing the product in the future.

Therefore the question arises as to how can a food manufacturer produce food that is microbiologically acceptable? The answer is in the proactive approach of Hazard Analysis Critical Control Point (HACCP) . This internationally accepted means of assured safe food manufacture has already been used by large food companies for many years. However the implementation in small food outlets has been problematic due to the perceived burden of documentation. For assistance in industrial-scale HACCP implementation see the author's book Food Hygiene, Microbiology and HACCP.

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