Analysis of botulism outbreak calls for awareness of risk
The analysis describes the first US outbreak of botulism linked to pesto in 2014, which involved two people.
Pesto was produced without proper registration and licensure and sold commercially in jars at a farm stand and online.
Authority action
After being notified of the possible botulism cases, Cincinnati Health Department epidemiologists interviewed the two patients and families.
The patients ate a meal of baked chicken breasts, boiled pasta, steamed vegetables, and Pine Nut Basil Pesto from VR Green Farms on July 13.
On July 28, investigators collected leftovers from the meal and two unopened jars of pesto and sent them for testing. The pesto jar from the July 13 shared meal had been discarded.
Botulinum toxin type B was detected in leftovers of pasta and pesto by ELISA. A culture of these food samples yielded Clostridium spp. that produced botulinum toxin type B, and PCR detected DNA encoding for type B toxin.
Pesto came from a family member who had purchased several jars in May 2014 at a farm stand in San Clemente, California.
Health officials in California analyzed an unopened jar of the pesto from this family member’s house.
It was found to have a pH of 5.3 and water activity of 0.965 (parameters insufficient to prevent growth of C. botulinum).
Several jars had been sent to family members in Colorado; one jar was collected and tested negative for botulinum toxin–producing Clostridium spp. and botulinum toxin at Ohio Department of Health Laboratory (ODHL).
Seven people in Colorado ate the pesto on May 29 but no illnesses were reported.
Investigation findings
On July 29, CDPH discovered multiple jarred food items, including the Pine Nut Basil Pesto, available on the company’s website and farm stand. The firm and the pesto manufacturer did not have permits or registrations allowing them to legally manufacture or sell canned food, including food in jars, in California.
CDPH investigators identified a lack of knowledge of safety issues involved with jarring foods and inadequate acidification and pressurization practices. There were no records indicating that critical factors (e.g., pH, time, and temperature) were monitored during production.
Invoices showed at least 39 jars of pesto were produced in 2014. After discussing the link between the cases in Ohio and pesto, the firm recalled all jarred food products.
In the outbreak described, both patients sought medical care multiple times before receiving a diagnosis of botulism, and one patient was hospitalized for nearly two weeks before a clinician made the epidemiologic link between the two patients when they were hospitalized in the same health care facility. If not for this clinician, the diagnoses might never have been made.
Clinical specimens from the two patients were sent to the ODHL for Clostridium botulinum testing by culture and mouse bioassay. They were collected ≥12 days after the shared meal, and tests were negative.
Consumer demand for fresh, farm-to-table foods has increased substantially during the past 15 years, said the researchers.
“Consumers at farm stands and markets should be aware of the risk from improperly canned foods, including those in jars, produced without licensure and oversight from regulatory bodies.
“Producers of canned foods for commercial use should ensure that they adhere to food safety regulations.”
Source: Morbidity and Mortality Weekly Report (MMWR)
“Outbreak of Foodborne Botulism Associated with Improperly Jarred Pesto - Ohio and California, 2014”
Authors: Burke P, Needham M, Jackson BR, Bokanyi R, St. Germain E, Englender SJ.
