Whole genome sequences of the Listeria monocytogenes strains isolated from recalled quesito casero cheese produced by Oasis Brands were found to be highly related to sequences of Listeria strains isolated from one person ill in September 2013 and two people ill in June and August 2014.
The Centers for Disease Control and Prevention (CDC) said although limited information is available about the specific cheese products eaten by ill people, whole genome sequencing findings, with cheese consumption history of the patients suggests that illnesses could have been related to products from Oasis Brands.
Illness link
The two persons who were able to answer questions about specific varieties of Hispanic-style soft cheeses reported consuming quesito casero, though neither could remember the brand, said CDC.
The three ill persons were reported from New York, Tennessee, and Texas and all were hospitalized.
One death was reported in Tennessee and one illness was related to a pregnancy and was diagnosed in a newborn.
Several recalls of products by Oasis Brands have been announced by US Food and Drug Administration (FDA).
Investigation process
Virginia’s Division of Consolidated Laboratory Services (DCLS) identified Listeria monocytogenes in quesito casero, a type of unaged soft cheese, during routine sampling in July.
Oasis Brands recalled quesito casero (fresh curd) in August due to possible contamination after the pathogen was isolated from the product.
In August the FDA began inspections at the firm's processing facility in Miami, Florida and collected environmental samples which found the pathogen.
Cuajada en hoja (fresh curd) was involved on October 6 after the FDA isolated the pathogen and various other cheese and dairy products sold under the Lacteos Santa Martha brand were recalled on October 16.
The company ceased production and distribution of the products as it and the FDA continue investigating what caused the problem.
FDA and Virginia DCLS performed pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS) on isolates from cheese (quesito casero) and environmental samples.
Compared with PFGE, WGS provides a clearer distinction of genetic differences between bacteria strains so those that are highly related by WGS are more likely to be from a common source.