Bacillus Cereus

B cereus has been discovered since 1955 as a cause of food poisoning (Luna etal 2007). 52 cases of food borne diseases connected with B cereus were reported in the interval between 1972 and 1986 and only two cases were reported in 2003 which represent about 2 % of the actual cases due to underreporting and many of the case go undiagnosed(Benenson 1990) . According to the south Carolina department of Health and Environmental control and CDC,close to 25% of state public health laboratory do not carry out B cereus testing routinely (Kramer& Gilbert 1989).

The Centre for Disease Control estimates that 97% of all cases of food poisoning come from improper food handling; 79% of cases result from food prepared in commercial or institutional establishments and 21% of cases result from food prepared at home (Terranova & Blaker 1978). The most common etiologies are as follows: (1) leaving prepared food at temperatures that allow bacterial growth, (2) inadequate cooking or reheating, (3) cross-contamination, and (4) infection in food handlers (Blaker 1978).

Cross-contamination may occur when raw contaminated food comes in contact with other foods, especially cooked foods, through direct contact or indirect contact on food preparation surfaces. Bacteria cause approximately 75% of the outbreaks of food poisoning and for 80% of the cases with a known cause in the United States (Blaker 1978). As many as 1 in 10 Americans has diarrhea due to food-borne infection each year. The 2 syndromes associated with B cereus food poisoning include short incubation or emetic syndrome with I.
C=1-6 hours and the long incubation or Diarrhea syndrome with I. C=6-24 hours (Kramer 1989). Fried rice is the leading cause of emetic syndrome in the US (Bean 1990; Terronova 1978). Heat stable emetic toxin (ETE) is responsible for the short incubation period syndrome while the heat labile enterotoxin is responsible for the long incubation syndrome (Bean etal 1990) Syndrome Types of Bacillus Cereus food poisoning Bacillus cereus food poisoning has two varieties namely the emetic syndrome as well as the diarrhea syndrome types. B.
cereus has some toxins responsible for its pathology and such toxins produces diseases that tally more with intoxication than absolute food poisoning. The emetic type can usually be confused with staphylococcal food poisoning due to its short incubation period (Luna etal 2007). However staph aureus being an important cause of food poisoning produces infection following growth in protein and carbohydrate foods. The enterotoxins of S aureus are super antigens and are heat stable making them resistant to the action of gut enzymes .
As small as 25 microgram of enterotoxin B can produce diarrhea and nausea (Luna etal 2007). The emetic effect of this toxin is believed to be as a result of central nervous effect following the action of the toxins on the gut neural receptors (Ficker etal 2007). Some strains of staph aureus produce enterotoxins during their development in meat, dairy foods and other food products and characteristically, this food usually has been recently prepared but has not been properly refrigerated. Almost 6 distinct types of staph enterotoxins exist.
Following the swallowing of the preformed toxin, it is taken in by the gut mucosa and subsequently stimulates neural receptors and this stimulus is transferred to the vomiting centre in the brain and this projectile form of vomiting usually occur after few hours and it is less frequently associated with diarrhea and staph food poisoning is regarded as the commonest form. The food poisoning due to staphylococcus are usually associated with a smaller incubation period when compared with B cereus (from 1 to 8 hours).
It is also associated with a very violent, copious nausea, diarrhea and vomiting all occurring in the absence of fever(Benenson 1990). It should be noted that with the emetic type where the incubation period is 2-8 hours, the prominent symptom is vomiting whereas in the diarrhea type with incubation period of 8-16 hours the prominent symptom is diarhoea. Other species of bacillus are infrequently associated with human pathologies and difficulty arises in differentiating superficial contamination with B cereus from the authentic disease caused by this same organism .
About 5 species of the Bacillus are aetiologic agents in insects and they include: B larvae, B lentimorbus,B sphericus,B papillae and B thurigiences and some of them have been taken advantage of by their use as insecticides(Fricker etal 2007) . Incorporation of the gene from B thuringiesis into some commercial plants has been recently achieved and this subsequently has generated a lot of controversies among the activists on environmental issues about the safety of these genetically fashioned food and plants products (Guerrant and Bobac 1991).
Food types associated with food poisoning While the emetic type is associated with foods like fried rice and in fact the leading cause in the US (Black low &Greeberg 1991), the diarrhea syndrome is associated with the likes of sauces and meat. The short incubation type is linked with fried rice that is cooked and kept warm for many hours and is also often associated with Chinese foods. A previous outbreak has revealed macaroni and also cheese from milk being the source of the bacterium.
Incubation Period of the two syndromes of B. cereus that causes Food poisoning In the emetic type the diarrhea usually last for about 24 hours and it usually start 1-5 hours after the ingestion of the food substance like rice and it may also follow the ingestion of pasta foods. Food poisoning of the long incubation period i. e. 10 to 24 hours is the diarrhea type and this type may be confused with clostridia food poisoning. Mechanism of action ETE-forms small molecules, channels and holes in membranes.
HBL-stimulates intestinal fluid secretion by various mechanisms including activation of adenylate cyclase and pore formation. Toxin of B-cereus include emetic toxin (ETE), Nhe and EntK. Only 2 of the 3 enterotoxins participate in the causation of food poisoning and they consist of 3 different protein substitute acting together. HBL is a haemolysin while Nhe is not . EntK is a single component protein and not associated with food poisoning (Terranova&Blaker 1978). The 3 enterotoxins of B cereus have cytotoxic effect and they act on cell membranes forming holes and channels in them.
People at risk of developing food poisoning The high risk population for food poisoning includes the older adults and this is due to the fact that as you get older, your immune system may not respond as quickly and as effectively to infectious organisms as when you were younger (Blacklow & Greeberg 1999). The Similar explanation goes for Infants and young children because of the immaturity of their gastrointestinal tract and also their immune systems haven’t been so fully developed.
People with chronic diseases are also at risk of food poisoning because having a chronic condition, such as diabetes or AIDS, or receiving chemotherapy or radiation therapy for cancer reduces your immune response. Clinical features The clinical symptoms produced by the emetic type include abdominal pain, vomiting, nausea and self limiting type of diarrhea. The clinical symptoms of the diarrhea or long term incubation syndrome include fever and vomiting in rare cases but most prominent symptoms are profuse diarrhea and abdominal pain.
The intestinal toxin is usually preformed but it can be produced inside the intestinal tract (Kramer &Gilbert 1989). To make a meaningful diagnosis of this organism, one will require that a load of about 105 of the organism is present in the feaces and just the presence of the organism not up to this maximum concentration is not enough to diagnose. Also importantly, B cereus is an important aetiologic agent of eye diseases such as panopthalmitis, endopthalmitis and infection of the cornea too .
This organism during a traumatic event is usually inoculated into the eye and it usually does this via the foreign body introduced into the eye. Both local and system problems have been reported associated with B cereus and it’s been associated with medical foreign devices such as braces, prosthetic valves, and some invasive procedures like passage of urinary catheter, nasogastric tube and chest tubes. Some of the associated systemic problems caused by the organism include meningitis and encephalitis, pneumonia, osteomylitis, as well as endocarditis.
The use of intravenous drugs also predisposes to infections by B cereus (Bean &Griffith 1990). The organism lives inside the soil and it is a common finding that it contaminates foods like rice (Jones and Blicslayer 2002). The toxins production usually occur when large amount of rice is prepared and then allowed to cool down which subsequently lead to the growth of the spores and the vegetative form now synthesize the toxins and all these occur in the log phase growth period or during the process of sporulation.
Clostridium is the third leading cause of bacteria food borne epidemics following salmonella and staphylococcus aurues The enterotoxin it produces causes a self resolving gastroenteritis and it does this by binding to the brush border membrane receptor and therefore binding to abdominal wall mucosa, interrupting the exchange of ion and the resultant effect is the loss of ions and low molecular weight metabolic products (Benenson 1990). The time of onset of the clinical manifestation is usually between 8 and 16 hours i.
e. earlier than that of B cerues and it follows the ingestion of the organism itself. Although it is also associated with abdominal pain and diarrhea but less commonly with systemic problems. Another species of the clostridium family is clostridium difficile is usually associated with over 25% of antibiotic associated diarrhea and 95% cases of psedomembraneous enterocolitis and the organism produces two enterotoxins (exotoxin A&B). Some of the precipitant antibiotics include clindamicin and ampicillin.
However the diarrhea of B cereus infection does not follow antibiotics use. The clinical picture of C difficile diarrhea includes nausea, vomiting, abdominal pain as well as greenish voluminously large amount of diarrhea (Blacklow and Greeberg 1991). Protoscopy will show pseudo membranes and microabscesses with an erythematous mucosa and the diagnosis is confirmed by demonstrating toxins in the stool and the current treatment of choice includes oral metronidazole (Fricker etal 2007). Other aetiologic agents of food poisoning
Other bacteria organism toxins that have been implicated to cause food poisoning include those of Vibro cholera, Yersina enterolitica, and Aeromonas species. However the exact role of the organism and their toxins in pathogenesis is not well delineated except for V cholerae. C perfirigens is another aetiologic agent responsible for food poisoning (Jones&Blikslaker 2002). Case Study 1 Father, mother and 2 children with respective ages 34, 28, 6 and 4 presented in a hospital because of passage of watery stool and fever all of 6-12 hours duration.
There was history of eating green salad beans, ground meat and tortillas prepared by someone else in an encampment because they are migrant farm worker family. It was also found out later that another 7 month old child in the family had not taken the food and was found to be well. The children started having abdominal discomfort, diarhoa and fever 24 hours later and the symptoms have been continuous since the previous 12 hours and both affected children have been having bloody stool.
The parents also started having similar symptoms 5 and 7 hours ealier excluding visible bloody stool. There was history that some other persons in the encampment had similar symptoms in the past 2 weeks and that the camp’s hygienic state is poor. Both children are warm to touch on examination as well as the parents and have increased heartbeat and the children also appeared to lack fluid . A mount of their stool revealed white cells that fight infections and the faeces of the children were blood stained. Comments and explanation
Generally speaking, vomiting, nausea, fever abdominal pain and diarrhea are the major key symptoms of infection of the gastrointestinal tract and the main symptom will depend on the cause whether it is a toxin or invasive or a combination of the two (Guerrant &Bobak 1991). Usually, nausea and vomiting are often related with preformed toxins in food. For instance, B cereus and staph aureus can generate enterotoxins in food and this usually happen few hours after the ingestion of the food substance (Guerrant &Bobak 1991).
The likes of enterotoxins of enterotoxigenic E coli and Vibrio Cholera usually affect the superior aspect of the bowel to cause watery and massive diarhoea. As in the above scenario, invasive bacteria penetrate the colonic mucosal and cause abdominal pain with blood and mucous associated with fever and dehydration and this constellation of symptoms are regarded to as dysentery and the implicated aetiologic are for dysentery are:Entamoeba histolytica,Clostridium difficile ,enteroinvasive E. coli,salmonella ,campylobacter jejuni.
The above children were admitted in the hospital and treated and parents were also treated as outpatients with fluids and drugs and this is followed by public health sanitary measures in the camp. In conclusion, food poisonings are very common most especially in the developing parts of the world with high morbidity and mortality most especially among infants and children (Kramer &Gilbert 1989). Therefore of value are public health preventive measures by the provision of good water supply as well as sanitary and hygienic water and food supply.
(Guerrant RL, Bobak DA: Bacterial and protozoa gastroenteritis. N Engl J Med 1991; 325:32). Case study 2 A reported incidence of acute gastrointestinal infection occurred in July 21, 1993 among the members of staff as well as the pupils of a co-owned child day care school after a catered lunch. This lunch was served for eating to 82 pupils of the day care centre to children between the age of 6 and less and the children are 82 in number along with 9 staff members. Past dietary history was gotten from 80 individuals and 67 were said to participate in the lunch.
An individual at the day care made a case definition of vomiting. Among those served and who ate at the lunch, 21 %( 14) became sick and 13 did not. The symptoms observed ranged from diarrheal in 14 %,pain in 30% case and nausea in 71% case. 12 out of the 14 instances occurred among the children from ages 2. 5-5 and 2 other members of staff. Stastical analysis reveals that the median incubation period was 2 hours(the range is 1. 5-3. 5 hours). The resolution of symptoms took place over median interval of 4 hours following the onset(range 1. 5-22 hours).
Among the dishes served in the local restaurant, only chicken fried rice was linked with notable illness and the problem occurred among 14(29%) out of the 48 individuals who ate the chicken fried rice in comparison to none of the 16 individuals who did not eat. The implicated rice was prepared the night preceding the incidence on July 20 under room temperature before it was refrigerated. The report also confirms that the rice was heated in oil with the slices of the cooked chicken on the morning of the lunch, then handed over to the daycare centers at around 10:30 am without refrigeration and served at noon without rewarming it.
As a subsequence to the outbreak the advice by the health personnel to the restaurant officials and daycare staff was to stop the custom of cooling of rice or any other food at room temperature henceforth and that food should be kept at appropriate temperature of 5 degree or above 60 degree and that the temperature should be confirmed by a thermometer. Analysis of the case study 2 This short incubation syndrome variety of the disease which featured in this outbreak is overseen by highly stable toxin that can withstand enzymatic effect as well as extremes of temperature and PH.
The diarrhea syndromic type is mediated on the other hand by an acid and heat labile intestinal toxin affected by the effect of the proteolytic enzymes like pepsin, trypsin etc. To make a diagnosis of Food poisoning, it is essential to isolate more than 10 5organisms per gramme from the epidemiologically implicated food substance . The self resolving as well as the lack of severity in most cases account for the reason B cereus is underreported(qtd in Todar 2004). Moreover recent research reveals that close to 20 % public health laboratory do not have the facility for the routine test for B cereus.
In the United States, the leading cause of the emetic syndrome type or the “Short incubation syndrome” type of B. cereus is fried rice. As discussed before that B cereus more often than not is found in uncooked rice where the heat resistant spores also withstand and survive cooking. The survival of the vegetative form is a possibility after cooked rice is placed in an incubator as it generates heat stable toxin substance which can withstand heating(Kramer &Gilbert 1989). In this described scenario, the vegetative form must have proliferated at the food joint and also at the day care centre while the rice was being kept at room temperature.
The problem is the unawareness of the restaurant food workers that certain danger is associated with cooked rice potentially. It’s imperative from the report the need to properly inform food handlers about fundamental rules and customs for hygienic healthy and safe food management and handling (Benenson 1990). Web Review of Todar’s Online Textbook of Bacteriology. “The Good, the Bad, and the Deadly”. (SCIENCE Magazine- June 4, 2004 – Vol 304: p. 1421). Retrieved from www. textbookofbacteriology. net on May20, 2009. Bibliography Bean NH, Griffin PM.
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