Listeria outbreak from Bidart Bros. apples over - CDC

By Joseph James Whitworth contact

- Last updated on GMT

Caramel apples. Photo: therealbridgetpalmer/flickr
Caramel apples. Photo: therealbridgetpalmer/flickr

Related tags: Apple, Listeria

An outbreak of Listeria monocytogenes in apples linked to the deaths of at least three people appears to be over, according to the US Centers for Disease Control and Prevention (CDC).

A total of 35 people infected were reported from 12 states, 34 were hospitalized and listeriosis contributed to at least three of the seven deaths reported.

Bidart Bros. of Bakersfield, California recalled Granny Smith and Gala apples because environmental testing revealed contamination with Listeria monocytogenes at its apple-packing facility last month.

On January 6 the firm recalled all Gala and Granny Smith apples shipped from its Shafter-based packing facility in 2014.

PFGE and WGS use

Pulsed-field gel electrophoresis (PFGE) analysis confirmed that PFGE patterns matched the outbreak strains isolated from people affected.

FDA laboratory analyses using whole genome sequencing (WGS) showed these Listeria isolates were highly related to the outbreak strains.

Illness onset dates ranged from October 17 to January 6.

Eleven illnesses were associated with a pregnancy (occurred in a pregnant woman or her newborn infant). One fetal loss was reported.

Among people whose illnesses were not associated with a pregnancy, ages ranged from 7 to 92 years, with a median age of 62 and 33% were female.

Three invasive illnesses (meningitis) occurred in otherwise healthy children aged 5–15 years.

Interviews to find source

The CDC reported 28 of the 31 ill people interviewed reported eating commercially-produced, prepackaged whole caramel apples.

The three ill people who did not eat caramel apples did report eating whole or sliced green apples not covered in caramel.

Brands named in interviews include Happy Apple, Carnival and Merb’s Candies.

Two outbreak clusters were identified by the PFGE technique.

When WGS was used, two Listeria isolates (one within each cluster) were found to be highly related but distinct between the two clusters.

CDC investigated these together because one person was infected with both Listeria strains simultaneously and illnesses occurred during a similar time period and in similar regions.

The Public Health Agency of Canada (PHAC) identified two cases of listeriosis with the same PFGE patterns as those seen in the US outbreak. 

More detailed testing using WGS showed the isolate from only one of the two cases was genetically related.

Related topics: Food Safety & Quality

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