Five people infected with one of four strains of Listeria monocytogenes identified by pulsed field gel electrophoresis (PFGE) were reported from Kansas.
The three women and two men were hospitalized at the same place for unrelated problems before developing invasive listeriosis.
Isolates from four of these patients are highly related by whole genome sequencing (WGS).
Patients’ illnesses
Patients became ill between January 2014 and January 2015 after eating Blue Bell Creameries ice cream in hospital.
Although some illnesses were more than a year ago, the cluster was identified this month after health officials noted that two patients who had been in the same hospital were infected with Listeria monocytogenes bacteria that were indistinguishable by PFGE, said the US Centers for Disease Control and Prevention (CDC).
The US Food and Drug Administration (FDA) provided a list of affected products.
Four of them had milkshakes made with a single-serving Blue Bell brand ice cream product called “Scoops” while they were in the hospital.
Invoices by the hospital to the Kansas Department of Health and Environment show the Blue Bell brand ice cream Scoops came from Blue Bell Creamery’s facility in Texas.
In an unrelated investigation, the South Carolina Department of Health and Environmental Control isolated Listeria monocytogenes from Chocolate Chip Country Cookie Sandwiches and Great Divide Bars from a distribution center in 2015.
The Texas Department of State Health Services then collected product samples from the Blue Bell Creameries production facility in Brenham, Texas.
These samples yielded Listeria monocytogenes from the same two products tested by South Carolina and also from the ice cream Scoops, which is made on the same production line.
It is not confirmed that the hospital receives ice cream only from the Brenham facility, said FDA.
Blue Bell response
Blue Bell Creameries has removed the Scoops ice cream product and other products made on the same production line and shut down the line.
The firm said it was its first recall in 108 years.
“One of our machines produced a limited amount of frozen snacks with a potential listeria problem,” it said in a statement.
“When this was detected all products produced by this machine were withdrawn. Our Blue Bell team members recovered all involved products in stores and storage.
“This withdrawal in no way includes our half gallons, quarts, pints, cups, three gallon ice cream or the majority of take-home frozen snack novelties.”
Three strains of Listeria monocytogenes isolated from the ice cream samples had PFGE patterns indistinguishable from those of Listeria bacteria from samples from four patients.
Listeria isolates with four other PFGE patterns were also isolated from the ice cream samples.
WGS of the Listeria monocytogenes isolates obtained from the ice cream is in progress, said the CDC.
One patient’s Listeria monocytogenes strain has a PFGE pattern that does not match any identified in an ice cream sample but epidemiologic evidence suggests it could be related.
Contaminated ice cream products may still be in the freezers as products can have a shelf life of up to two years.