Growth Conditions of and Emetic Toxin Production by Bacillus cereus in a Defined Medium with Amino Acids

Abstract

The growth and emetic toxin (cereulide) production of Bacillus cereus strains in defined culture media were studied. We found that a fully synthetic medium (CADM) allowed the production of emetic toxin and the addition of glucose enhanced it. By subtracting each amino acid from CADM, we found that only three amino acids, valine, leucine and threonine, were essential for growth and toxin production by B. cereus. The addition of high levels (50 mm) of leucine, isoleucine and glutamic acid decreased the toxin production. Other amino acids had no effect at this concentration.

EmeticBacillus cereusAre More Volatile Than Thought: Recent Foodborne Outbreaks and Prevalence Studies in Bavaria (2007–2013)

“…Products classified as being insensitive were dairy based, displayed a low pH value (e.g., cream cheese and unsweetened quark), had a high fat content like chocolate and nut spread, and/or were characterized by low water availability or high osmolarity (e.g., dried fruits and 10% herbal salt solution). Earlier studies showed that growth of B. cereus was suppressed in foods with pH values below 5.0 [34–36], which is in line with our low-risk classification of matrices that had pH values around 4.3 to 4.8, such as the whey drinks. The combination of neutral pH values and medium a w -values with high amounts of fat and cocoa was found to be indicative of the group of products being at medium risk of toxin synthesis (Table 2 and Figure S2).…”

Bacillus cereus, the causative agent of an emetic type of food‐borne illness

“…No cereulide production was found in peptone broth [57]. The presence of glucose tends to support cereulide production while excessive amounts of leucine, isoleucine, and glutamic acid significantly repress cereulide formation [58]. In food systems, the highest rates have been observed in rice and pasta while toxin production in bread and cakes was low [59,60].…”

From soil to gut:Bacillus cereusand its food poisoning toxins

“…Differences in levels of cereulide production between strains have also been observed (Häggblom et al , 2002; Rajkovic et al , 2006) and are possibly due to differences in regulation, because the ces genes themselves show only a low level of heterogeneity (Ehling‐Schulz et al , 2005b). Furthermore, environmental factors such as oxygen, pH, temperature and the presence of specific amino acids have been described to influence the production of cereulide (Agata et al , 1999; Finlay et al , 2000; Ehling‐Schulz et al , 2004b; Jääskeläinen et al , 2004), and it has been shown that stationary incubation of food supports a higher level of cereulide production compared with aerated incubation (Rajkovic et al , 2006; Shaheen et al , 2006). However, the mechanisms regulating cereulide synthesis are still largely unknown.…”