The Centers for Disease Control and Prevention reported Thursday that it is investigating a multistate outbreak of Salmonella Typhimurium infections. A preliminary analysis indicates the outbreak may be the result of exposure in clinical and teaching microbiology laboratories.

As of April 20, the CDC said 73 individuals infected with the outbreak strain of Salmonella Typhimurium have been reported from 35 states.  There has been one death and at least 10 people have been hospitalized. Several of those sickened are children who live with someone who works or studies in a microbiology lab.

The CDC said that during an epidemiologic study in February and March, 32 people were quizzed about possible exposures in the week before they became ill. Investigators compared their answers to a control group of 64 individuals of similar age previously reported to state health departments with other illnesses.

The investigators found that the ill persons (60%) were significantly more likely than the control persons (2%) to report a connection to a microbiology laboratory.

Many of those infected were either students in microbiology teaching laboratories or employees in clinical microbiology laboratories.  Several said they worked specifically with Salmonella bacteria in microbiology laboratories.

The New Mexico Department of Health found that the outbreak strain was indistinguishable from a commercially available Salmonella Typhimurium strain used in several of the laboratories, according to the CDC.

“These data suggest this strain is the source of some of these illnesses,” the CDC said, adding that “several children who live in households with a person who works or studies in a microbiology laboratory have become ill with the outbreak strain.”

Illness onset dates have generally ranged form Aug. 20, 2010 to March 8, 2011.  The number of new cases has declined substantially during the past several weeks, the agency said.

The CDC advised people who work with Salmonella bacteria in microbiology laboratories to watch for symptoms of Salmonella infection, such as diarrhea, fever and abdominal cramps. They should contact a health care provider if they or family members have any of these symptoms.

The agency also recommended that non-pathogenic (attenuated) bacteria strains should be used when possible, especially in teaching laboratories, to help reduce the risk of students or their family members becoming ill.

All students and employees using laboratories should be trained in biosafety practices, the agency emphasized, such as proper handwashing, not allowing lab coats to leave the lab, and not allow food, drinks or personal items like car keys or cell phones to be used while working in the laboratory or placed on laboratory work surfaces.