All About Bugs and Food

Our Microbial Overlords are wonderful and some are even tasty. But they can bugger up your food business in a heartbeat. The Foodborne FAQs concentrate on bugs relevant to food so you can get them before the bastards get you. There are also other dubious resources – from food alerts to guidance on legislation – all listed under the ‘Food’ tag.

Disclaimer: I’m a microbiologist, not a clinician. These resources mention stuff bugs can do to you or your customers but for medical advice consult a bloody doctor, not the Internet. Especially not this site.

Chances are I don’t know what I’m talking about anyway and if you have any of the symptoms described here stop twatting about on the Interwebs and see a medic. Refer to the full legal nonsense here, don’t run with scissors, stick your tongue into plug sockets, attempt surgery on yourself etc etc.

Remember more can impact the survival of bugs in food than the variables listed here so the this is a guide only. If you work in food it’s your responsibility to ensure your food is safe, not mine.

Using the Rectofossal Resources

The RectoBugWiki is a resource primarily aimed at people working in food and so has a lot of geeky, technical stuff. If you want a general rant about any particular organism please contact me and I’ll happily write one; our Microbial Overlords are relentlessly fascinating so there’s plenty to write about.

Various bugs associated with (principally) foodborne illness are listed here; the conditions they like (pH, temperature etc) and how to piss them off (with heat, chemicals etc). I also list those that are notifiable to Local Authority Proper Officers in the UK.

Because this is intended to be a resource for people working in food the entries also talk about things like…

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 lost 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. It’s a log scale for those of you with a mathematical bent.

Different organisms have different D-values at different temperatures so you might see D80C = 45s – or that organism is reduced by 90% after exposure to temperatures of 80°C for 45 seconds.

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 but 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 bloodborne ones) and Hep E (turd-to-tongue route and 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.