INVESTIGATION OF A STAPHYLOCOCCAL FOOD POISONING OUTBREAK IN A CENTRALIZED SCHOOL LUNCH PROGRAM

The trend in many communities toward centralized school lunch preparat ion potentially increases the risk of foodborne illness. Foods often a re prepared long before serving and may be distributed to satellite sc hools by persons with little formal training in safe techniques of foo d preparation or food service. In May 1990, an outbreak of staphylococ cal food poisoning occurred in elementary schools in a Rhode Island co mmunity participating in such a program. In the investigation of the o utbreak, students in schools that reported cases were interviewed. Foo d preparation, handling, and distribution were reviewed. At School E, 662 lunches were prepared and distributed to 4 additional schools (sch ools A-D). Schools A and B accounted for nearly all cases of the food poisoning, with rates of 47 percent and 18 percent. Eating ham increas ed the risk of illness (62 percent of those consuming ham and 3 percen t of those who did not, relative risk = 18.0, 95 percent confidence in terval = 4.0, 313.4). Large amounts of Staphylococcus aureus were cult ured, and preformed enterotoxin A was identified in leftover ham. A fo od handler, who tested positive for the implicated enterotoxic strain S. aureus, reported having removed the casings from two of nine warm h am rolls 48 hours prior to service. Because of improper refrigeration, prolonged handling, and inadequate reheating, the ham was held at tem peratures estimated at 10-49 degrees Celsius (50-120 degrees Fahrenhei t) for a minimum of 15 hours. The potential for larger outbreaks promp ted a statewide training program in safe food preparation for school l unch personnel, which may have applications for other communities.