Nontypical Bacillus cereus Outbreak in a Child Care Center.

On October 29, 1998, The Garland Health Department in Texas investigated seven illnesses at a church day school. The six children and one adult had handled hydrated, orange-colored rice before consuming a meal, B, cereus organisms were found in the rice at an estimated concentration of 5.6 X 10 [5] per gram. As far as the authors can determine, this outbreak is the first one documented to have occurred from indirect ingestion of B. cereus by way of contaminated hands, as opposed to ingestion of the toxin in the food product in which the organisms grew.

Introduction

Bacillus cereus belongs to a genus of rod-shaped, Gram-positive bacteria that are widely found in soil, dust, and air. They are facultatively aerobic and produce heat-stable endospores when environmental conditions are not favorable to growth. B. cereus organisms also produce extracellular enterotoxins as they develop. Vegetative cell growth occurs between 41[degrees]F (5[degrees]C) and 122[degrees]F (50[degrees]C) and in a pH range of 4.5 to 9.3. The highly stable spores can survive temperatures up to 250[degrees]F (121[degrees]C) for 90 minutes.

B. cereus can cause disease in animals, and all humans are believed to be susceptible. Among foodborne illnesses, however, B. cereus accounts for only about two percent of reported outbreaks with confirmed etiology (Bean, 1990). This organism was first recognized as a possible cause of foodborne gastroenteritis in the early 20th century and was linked to an outbreak for the first time in the 1950s. All reported cases have been from ingested food sources.

Bacillus cereus produces two distinct clinical syndromes: diarrheal and emetic (Table 1). The diarrheal illness is caused by a large-molecular-weight, heat-and-acid-labile protein, and the emetic illness is caused by a low-molecular-weight, heat-and-acid-stable peptide. The diarrheal syndrome is associated with abdominal pain, cramps, and watery diarrhea. Fever and vomiting are not present. Onset of symptoms occurs six to 24 hours after ingestion of the organisms. The illness resolves in 24 hours or less. The diarrheal syndrome is often misdiagnosed as Clostridium perfringens food poisoning.

The emetic syndrome is associated with acute vomiting and nausea. Fever is not present. Onset of symptoms occurs from 30 minutes to six hours after ingestion of the toxin. Like the diarrheal type, the emetic syndrome resolves in 24 hours or less. The emetic symptoms and the quick onset closely mimic Staphylococcus aureus intoxication.

B. cereus food poisoning of both clinical types is self-limiting, with the diarrhea or vomiting eliminating the toxin from the digestive system. Antibiotics are not indicated; oral hydration is usually all that is required for full recovery. The illness is not transmissible from person to person, and because the organism is ubiquitous, it can even be isolated in small numbers from stools of healthy persons. Diagnosis of B. cereus food poisoning usually is confirmed by the isolation of greater than or equal to 1 X 10 [5] organisms per gram of epidemiologically implicated food (Chin, 2000).

Illness following the diarrheal syndrome has been associated with a wide variety of foods, including meats, sauces, gravies, and casseroles. The emetic syndrome is more selective and has almost exclusively been associated with fried or boiled rice. In the United Kingdom, one study found that 108 of 110 B. cereus intoxication cases were linked to fried rice or other prepared rice (Eley, 1992).

The presence of B. cereus in raw dried grains is so common that the only accepted methods of preventing foodborne B, cereus illnesses are proper cooking, holding, and chilling (Tartakow, 1981). Snyder has revealed that 100 percent of the uncooked-rice samples in the United States were confirmed to contain Bacillus cereus spores (Snyder, 1991).

The history presented below describes a nontypical B. cereus outbreak in a child care setting. Suggestions on illness prevention techniques also are presented.

Investigation Methods

On October 29, 1998, the Garland Health Department in Texas received several calls from concerned parents about a group of ill children and an ill teacher at a church day school. The total enrollment at the day school was 35 children, and there were 13 adult staff members.

Phone interviews were conducted with the day school director and the ill teacher, as well as with the parents of the ill children. The six children, all four years old, had experienced vomiting; one male child also had mild diarrhea. Onset of symptoms in all six children occurred six to 11 hours after they ate lunch on October 28. The adult female teacher experienced vomiting 20 hours after ingesting the same lunch. No one reported fever. The duration of symptoms was short, with all children and the adult making a complete recovery in less than 12 hours. Because of the symptomology, the investigation began with the idea of a biological or chemical food intoxication as the causative agent.

The lunch on October 28 had been purchased at a nearby national fast food establishment and brought to the church. All 35 children and 13 staff members had eaten small hamburgers and french fries prepared at the restaurant. Lunch was served within one hour of preparation. A Garland Health Department environmental health specialist inspected the fast-food restaurant and the church day school on October 29.

Investigation Results

The hamburgers were prepared from a frozen state and cooked to an internal temperature of 168[degrees]F (76[degrees]C). They were held at 156[degrees]F (69[degrees]C). The critical control points at the restaurant were handled safely, except that the chlorine sanitizer was found to be too weak at the three-compartment sink used for utensil washing. Before this investigation, the restaurant had been routinely inspected three times in 1998, with time/temperature controls and food protection found to be adequate each time. The store management had received no additional case reports.

Water samples from the church water fountains were tested with a portable chemical test kit. Unusual copper levels were not detected. No signs of improper plumbing connections or potential cross-connection were observed. At the time the day school was inspected, all chemicals were stored in an inaccessible closet. A pest control application had occurred on October 18 to control an indoor ant infestation in the lunchroom. The treatment had used a pyrethrum product that was labeled to have a relatively quick degradation in an open environment.

The six children and the adult who fell ill had been in the same classroom, the "four-year-old class." This class consisted of 12 students and two teachers. The investigation now concentrated on what the sick children and adult had done that the 29 healthy individuals did not do. Cupcakes were served to the four-year-old class on the morning of October 28; however, the teacher and two of the sick children did not consume the cupcakes. Most of the class period prior to lunch had been dedicated to Halloween activities: cutouts, drawings, and song. The four-year-old class also made jack-o-lanterns out of orange-colored rice glued to paper plates.

The next day the school was in session, the environmental health specialist returned to visit with the teachers in the four-year-old class. An orange-rice-covered jack-o-lantern was examined and collected (see photo). It had been made by one of the ill children.

The interviews revealed that the teacher who did not become ill had soaked the rice in water and orange food coloring the night before the jack-o-lantern activity. She assumed the rice was hydrated for approximately 12 to 14 hours at room temperature. The rice was blotted dry and given to the children to glue onto the paper plates. The six ill children were all in one work group, led by the teacher who became ill, and the other teacher instructed the children who did not become ill.

The jack-o-lantern activity took place just before the hamburger meals were served and consumed. The ill teacher did not have her six children wash their hands prior to consuming their meals. The other teacher did.

Health department staff scraped the colored rice from the paper plate and had it tested by an independent laboratory. B. cereus organisms were estimated to be at 5.6 X [10.sup.5] per gram of colored rice.

Discussion

It is assumed that the hydration of the rice with the food coloring allowed the Bacillus cereus spores to germinate, giving the organisms enough time, at conducive temperatures, to produce toxins as they grew and sporulated. The toxin then contaminated the children's hands as the rice was glued to the paper plates during the jack-a-lantern exercise. The six children and the teacher who failed to wash their hands thoroughly prior to eating ingested enough B. cereus toxin to produce the mild illness. As far as the authors can determine, this outbreak is the first one documented to have occurred from indirect ingestion of B. cereus by way of contaminated hands, as opposed to ingestion of the toxin in the food product in which the organisms grew.

Two very simple practices can prevent an outbreak of this type from occurring again. First, any hydration of rice with food coloring should take place immediately prior to use--or the soaking rice should be placed in a refrigerator. Eliminating the time the rice sits at room temperature will inhibit bacterial germination and the production of the enterotoxin. Second, hands should always be washed with soap and warm water before consumption of food or drink.

Handwashing before eating is something parents teach their children early in life, but it is also mandated in the child care setting. According to the Day Care Center Minimum Standards & Guidelines set out by the state of Texas, "Children must wash their hands with soap and running water after toileting and before eating." For both staff and children, the American Public Health Association recommends 10-second hand-washing with soap and warm running water on the following occasions: after toileting or changing of diapers, before food is prepared or served, before a table is set, before and after meals or snacks are eaten, and after pets or other animals are handled (Maternal & Child Health Bureau, 1992).

Studies have shown that a reduction in diarrheal-disease rates can be achieved simply by washing hands and monitoring children's handwashing (Briley et al., 1994; Osterholm et al., 1987). Daycare staff should be reminded that children learn good practices by watching and emulating the adult staff member. It is the adult caregiver's responsibility to ensure that hands are washed and that the children are shown the correct methods for cleaning their hands.

Conclusion

In the case reported here, Garland Health Department staff followed the epidemiological paradigm and started by inspecting the fast food restaurant. Recent research has debunked the investigation patterns followed by most health departments. A University of Arkansas study on Salmonella patients younger than four years of age (Schutze et al., 1999) has found environmental sources to be the overwhelming vehicle of transmission: Food or food preparation was isolated in only 13 percent of the researched cases. Thirty-six percent of the cases were linked to other family members. Thirty percent were linked to soil or dirt surrounding the front door or elsewhere inside the house. Sixteen percent were linked to animals in or around the home. This description oversimplifies the University of Arkansas research, but the point is that the case reported here shatters the assumptions on which the methods of most epidemiological investigations are based. Health department staff and the parents of the children assumed that t he source of the illness had to be the restaurant. That may not always be the case. Environmental health specialists and other disease investigators must evaluate all potential environmental sources, not just the foodborne route.

REFERENCES

Bean, N.H., & Griffin, P.M. (1990). Foodborne disease outbreaks in the United States, 1973-1987: Pathogens, vehicles, and trends. Journal of Food Protection, 53, 804-817.

Briley, R.T., Fowler, J.P., & Teel, J.H. (1994). Investigation and control of a Shigella sonnei outbreak in a day care center. Journal of Environmental Health, 56(6), 23-25.

Chin, J. (Ed.). (2000). Control of communicable diseases in man. Washington, DC: American Public Health Association.

Eley, A.R. (Ed.). (1992). Microbial food poisoning (1st ed.). London: Chapman & Hall.

Maternal & Child Health Bureau. (1992). National health & safety performance standards--Guidelines for out-of-home child care programs. Arlington, VA: National Center for Education in Maternal and Child Health.

Osterholm, M.T., Aronson, S.S., Klein, J.O., & Pickering, L.K. (Eds.). (1987). Infectious diseases in child day care. Chicago: The University of Chicago Press.

Schutze, G.E., Cave, M.D., Sikes, J.D., & Stefanova, R. (1999). The home environment and salmonellosis in children. Pediatric, 103(1), el. http://www.pediatrics.org/cgi/content/full/103/l/el (16 Feb. 1999).

Snyder, Jr., O.P. (1991). Hazard control in foodservice operations. QA Report, 1(9), 1-5.

Tartakow, J.J., & Vorperian, J. (1981). Foodborne & waterborne diseases: Their epidemiologic characteristics. Westport, CT: AVI Publishing Company.

                     Two Clinical Syndromes Associated
                           with Bacillus cereus
Characteristic        Emetic Sundroms
    Onset               0.5-6 hours
    Mimics        S. aureus intoxication
   Symptoms         vomiting and nausea
    Fever                no fever
    Abates      in [less than or equal to]
                   24 hours (6-24 hours)
    Cause      heat-and-acid-stable peptide
    Source             usually rice
Characteristic          Diarrhea Syndrome
    Onset                   6-24 hours
    Mimics         C. perfringens intoxication
   Symptoms    watery diarrhea (3-10 movements/day)
    Fever                    no fever
    Abates          in [less than or equal to]
                      24 hours (12-24 hours)
    Cause          heat-and-acid-labile protein
    Source          meats, gravies, casseroles