Bug Guide

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Bacteria, Viruses and Spores

Bacteria, viruses and spores are everywhere. In the environment. On every surface. And you have 10-100 times more bacterial cells on and in you than there are cells of you. Most are completely harmless – unless they get into the wrong place at the wrong time – but there are a few that can make us sick. This section concentrates on those relevant to food production and healthcare. Naturally we have some excellent products that stop pathogens in their tracks and the training and support to back them up. Remember more can impact the survival of bugs in food than the variables listed here so this is a guide only. If you work in food it’s your responsibility to ensure the food you serve is safe. And if you work in healthcare it doesn’t matter how well you clean a surface, if you’re not exercising proper hand hygiene you will pass on infections no matter how clean the environment is.

Nothing on this site should be construed as medical advice. It isn’t. If symptoms of a particular foodborne illness, for example, are listed this is for information only and is in no way diagnostic advice. If you think you have a bacterial or viral infection see your doctor, don’t rely on a website for a diagnosis.
Microbiology Resources

The Big Bad Bug Bible

Your guide to foodborne, healthcare-associated and other bacteria, viruses and more… Note that different bugs have different entry styles: for example foodborne bugs have hurdles and Critical Control Points (for HACCP) listed – these aren’t relevant for bugs that aren’t foodborne. Enjoy!

Bacteria, Spores, Viruses - what's the difference?
All are single-celled organisms and we associate them with making us sick (even though most don’t) – but each is very different. For example a key distinction is that viruses can only reproduce in a host cell – so influenza virus sneezed onto a chicken carcass cannot multiply, whereas the bacteria Listeria or Salmonella would.
Bacteria Viruses Spores Others
Bacteria are very simple, single-celled organisms that nonetheless exhibit all the ‘life attributes’ that we do. They respire. They feed. They move. They produce waste. They reproduce all by themselves -as do all other animals, plants, birds, fish… We tend to associate them with illness and disease but bacteria are not all harmful – far from it. Most aren’t just harmless, they’re beneficial – they eat our rubbish, we couldn’t digest our food without them, they make vitamins for us and maintain our atmosphere. They are diverse and fascinating creatures. And each of us has between 10-100 times more bacterial cells on and in us than there are cells of us. We are each a rainforest of diverse organisms – or a sentient social care system for our Microbial Overlords, depending on your perspective!
All organisms respire, feed, excrete, reproduce… Viruses, however, cannot do any of these things independently. Viruses are – essentially – inert, harmful, packets of biochemicals. They contain rogue sequences of DNA (genes) – the code that tells living cells what to do. Viruses can only reproduce by invading host cells and ‘hijacking’ them by injecting their rogue DNA – which then  instructs the host to make more viruses rather than doing what it should be doing. This is why viruses do not grow on foodstuffs and cause spoilage in the same way bacteria or fungi might – they can only reproduce in a host cell, not by themselves. Think of DNA as being the computer program that tells all living things what to do every second of every day at a sub-cellular level. Nearly 10% of our own DNA is viral DNA that inserted itself into our genome since the dawn of time but couldn’t find its way out again.
Spores are to bacteria what seeds are to plants; two genera of bacteria – the clostridia and the bacilli – have developed the same trick many plants use to survive hard times; they form a seed. A very tough, microscopic seed called a spore that can exist without nutrition and that develops very tough protection against the outside world – which can survive cooking. After food is cooked, the spores can turn into full‐fledged bacteria as the food cools – and here’s the most important part: these bacteria multiply much faster than do most other kinds of bacteria. That means that if you cook meats (one of the higher‐risk foods for these bugs) or other foods, then leave them at room temperature, this bacterium can multiply to levels that can make you sick a lot faster than other bacteria can. Spores are very resistant to heat, chemicals and other means that would make short work of bacteria.
Other simple organisms are mentioned in these pages; parasites such as protozoa, there are some moulds and fungi but all are, by and large, single celled organisms.
Using the Guide
This is a resource primarily aimed at people working in food and so has a lot of geeky, technical stuff. Various bugs associated with (principally) foodborne illness are listed here; the conditions they like (pH, temperature etc) and how to get rid of them (with heat, chemicals etc). The guide also lists those that are notifiable to Local Authority Proper Officers in the UK.
Water Activity (aw)

Water Activity is (basically) the energy state of water in a system. Microbial growth is dependent on Water Activity, not water content and higher aw substances tend to get more bugs growing on them. Bacteria usually require at least 0.9 and fungi at least 0.7. It’s useful in food safety as a critical control point both for HACCP programs and in food design because water migrates from areas of high aw to areas of low aw so if honey (aw ≈ 0.6) is exposed to humid air (aw ≈ 0.7), the honey will absorb water from the air. If smoked salmon (aw ≈ 0.965) is exposed to dry air (aw ≈ 0.5), it will dry out. Especially at weddings. This is important when designing foods for a long shelf life – mixing ingredients with markedly different aw is usually avoided. You can find lots of aw values here.

This relates to how good something is at killing bugs. It is the time taken to kill 90% of a given bug by a certain means, so if a population is reduced by 1 D, 10% of the original organisms remain, 2D 1% remain, 3D 0.1% remain. Different organisms have different D-values at different temperatures so you might see 80°C = 45s – or that organism is reduced by 90% after exposure to temperatures of 80°C for 45 seconds.
Hazard Groups and Notifiable Diseases
Notifiable to Local Authority

Some diseases are notifiable (to Local Authority Proper Officers – EHOs) under the Health Protection (Notification) Regulations 2010 due to the danger they present to public health. Note that various syndromes are also notifiable as well as organisms – for example, E. coli O157 is notifiable in its own right and Salmonella isn’t – but ‘food poisoning’ is, as is infectious bloody diarrhoea. (Incidentally, bloody diarrhoea is never a good look – always see a doctor). The full list is: Acute encephalitis │ Acute infectious hepatitis │ Acute meningitis │ Acute poliomyelitis │ Anthrax │ Botulism│ Brucellosis │ Cholera │ Diphtheria │ Enteric fever (typhoid or paratyphoid fever) │ Food poisoning │ Haemolytic Uraemic Syndrome (HUS – from some E. coli) │ Infectious bloody diarrhoea │ Invasive group A streptococcal disease │ Legionnaires’ disease │ Leprosy │ Malaria │ Measles │ Meningococcal septicaemia │ Mumps │ Plague │ Rabies │ Rubella │ SARS │ Scarlet fever │ Smallpox.
Hazard Groups

Organisms are classified by the WHO and HSE into four Hazard Groups. Some foodborne bugs are in Group 2, in Group 3 we have Salmonella typhi, SARS, VTEC E. coli, Hep B, C and D (the blood borne ones) and Hep E (turd-to-tongue route and found in 10% of sausages). Group 4 is principally stuff like viral haemorrhagic fevers where you bleed to death via every orfice you can think of as well as a few you can’t. Don’t start any long books.

Hazard Group 1

Unlikely to cause human disease.

Hazard Group 2

Can cause human disease and may be a hazard to employees; it is unlikely to spread to the community and there is usually effective prophylaxis or treatment available.

Hazard Group 3

Can cause severe human disease and may be a serious hazard to employees; it may spread to the community, but there is usually effective prophylaxis or treatment available.

Hazard Group 4

Causes severe human disease and is a serious hazard to employees; it is likely to spread to the community and there is usually no effective prophylaxis or treatment available.

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