Prevalence of Listeria species and Listeria monocytogenes on Raw Produce Arriving at Frozen Food Manufacturing Facilities

Ubiquity of Listeria monocytogenes in the environment impacts the food industry and presents concerns for frozen food facilities. This study determined the prevalence and numbers of Listeria species and L. monocytogenes on raw produce arriving at frozen food facilities. Raw produce was collected using multi-level blinding protocols to ensure anonymity of participants and avoid traceback. Five raw vegetables were selected: corn, carrots, green beans, peas, and spinach. Raw products were collected after arrival at the facilities but before any cleaning or other pre-processing steps that are typically performed inside the facility. The FDA BAM method for detection of Listeria spp. and L. monocytogenes was followed, with PCR screening followed by selective plating methods. Listeria numbers were estimated from positive samples using MPN methodology. A total of 290 samples were collected, with 96 and 17 samples positive for Listeria spp. (33.1%) and L. monocytogenes (5.9%), respectively. Enumeration data for the 96 Listeria spp. samples indicated 82 samples had greater than 100 MPN Listeria spp./g and 14 samples less than 100 MPN Listeria spp./g. The prevalence of Listeria spp. varied by commodity: spinach (66.7%), peas (50%), corn (32.2%), green beans (22.2%), and carrots (13%). L. monocytogenes prevalence was determined in corn (13.6%), peas (6.3%), and green beans (4.2%) arriving at processing facilities. Such data was previously unavailable to frozen vegetable processors and is valuable in implementing process control standards. The prevalence and pathogen concentration data from raw commodities found in this study can provide the industry information to conduct more accurate quantitative risk assessments and provide a baseline to model and target appropriate pathogen reduction steps during processing.

Dogs as reservoirs ofEscherichia colistrains causing urinary tract infection in their owners

ABSTRACTIt is known that humans and pets living together can share the sameEscherichia colistrain. In this study we assessed the role played by household pets as reservoirs ofE. colistrains causing urinary tract infection (UTI) in their owners. Fecal swabs from 15 dogs and six cats living with 19 patients with community-acquiredE. coliUTI were screened by antimicrobial selective plating to detectE. colidisplaying the same susceptibility profile of the UTI-causing strain. Pet/patient pairs sharing strains with indistinguishable susceptibility and pulsed-field gel electrophoresis (PFGE) profiles were quantitatively screened for fecal carriage of the UTI-causing strain approximately 10 months later using bacterial counts on selective agar supplemented with the relevant antibiotics. Isolates from both time points were characterized by whole-genome single nucleotide polymorphism (SNP) analysis. PFGE revealed indistinguishableE. coliwithin two (11%) pet/patient pairs. In pair A, the UTI-causing strain was detected 10 months later in both the patient (108CFU/g) and her dog (104CFU/g). In pair B, only the dog was colonized with the UTI-causing strain upon re-sampling (105CFU/g), indicating dog-to-man transmission. For both pairs, less than 70 SNPs distinguished any isolate from the first and second sampling. The study shows regular co-carriership of UTI-causingE. colistrains between humans and their pets, and indicates that dogs can be a source of human infection. Although final evidence for transmission is lacking, hygiene precautions should be considered by people fraternizing pets. This may be particularly relevant for persons with a compromised immune system.