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* In unfermented wort, ''E. coli O157:H7'' and ''Salmonella Typhimurium'' were shown to grow at a pH of 4.3, but stopped growing at a pH of 4.0 <ref name="Menz1"></ref>. However, some of these food poisoning bacteria can survive the low pH of the stomach (~2.0) long enough to cause illness, so relying on a low pH alone is not adequate. Bryan Heit recommends a pH of 4.5 or less, the use of well sanitized equipment, and monitoring the starter for the rapid onset of fermentation without putrid smells. Some oxidative yeasts that are the first "barriers" to bacterial growth may be inhibited at 4.0 pH <ref name="BryanMTF"></ref>.
* The risk of botulism toxin is extremely low, but not non-zero. Generally, ''C. botulism'' is not able to grow and produce toxin in low protein (non-meats) substances at a pH lower than 4.6 <ref>[http://www.ingentaconnect.com/content/iafp/jfp/1982/00000045/00000003/art00005 Toxin Production by Clostridium Botulinum in Media at pH Lower Than 4.6. Nobumasa, Tanaka. Journal of Food Protection®, Number 3, February 1982, pp. 214-284, pp. 234-237(4)]</ref><ref>[http://edis.ifas.ufl.edu/fs104 Preventing Foodborne Illness: Clostridium botulinum. University of Florida IFAS Extension. Retrieved 7/5/2015.]</ref>. However, proteins in the wort may allow growth at a lower pH than 4.6 (studies have not been done on wort, only on meats) <ref name="BryanMTF"></ref>. The presence of more than 5% oxygen in the wort will also reduce the risk <ref>[http://www.ncbi.nlm.nih.gov/pubmed/15895734 Growth and toxin production by Clostridium botulinum in steamed rice aseptically packed under modified atmosphere. Kasai Y, Kimura B, Kawasaki S, Fukaya T, Sakuma K, Fujii T. May 2005.]</ref>.
* To our knowledge, there have been no documented cases of food poisoning from beer <ref name="Bryan"></ref>. However: ''"It is well established that at least a dozen human pathogens can survive in fully fermented beer; moreover, sour-brewing (and home brewing in general) offers an additional opportunity for pathogens to gain a foothold or produce toxins which persist into the final product. Reality is that the source of most food poisonings is never established. A few industries (milk, meat, canning, etc) are under close scrutiny, and as such we have firm numbers for rates of food-borne illnesses from those industries. Neither commercial nor homebrewing is subject to that monitoring, so any cases of disease arising from contaminated products from either source would likely go unidentified.''" - Bryan Heit on MTF <ref name="BryanMTF"></ref>. For more information on the potential for pathogens surviving in beer, see [http://suigenerisbrewing.blogspot.com/2014/02/fact-or-fiction-can-pathogens-survive.html Bryan Heit's Blog article.].
* In the words of Bryan Heit from [http://suigenerisbrewing.blogspot.ca/2014/02/fact-or-fiction-can-pathogens-survive.html Sui Generis Blog]: "''If you have an immunodeficiency or are immunosuppressed: Obviously, don't take medical advice off the internet. Talk to your MD to see if you are at risk of infection - especially if you're condition/treatment increases your risk of fungal infections. If so, or if you are concerned, stick to beers that are fermented using commercial strains of Saccharomyces yeast.''" <ref name="Bryan"></ref>