Sources of Listeria spp. in domestic food processing environment

Abstract

The presence of Listeria spp. in food processing environment including food handlers was investigated in 19 food processing units (the unit represents a part of big dairy plant) in addition to two other plants that produce frozen and non-frozen foods. Listeria spp. was detected in all investigated food processing units/ plants. No one environmental area was more linked with the presence of the pathogen than the other. Listeria spp. were isolated from direct sources such as drains, floors, standing/condensed water, process equipment, miscellanous and residues. Listeria innocua and L. monocytogenes were the only two species detected in the internal food processing environment, however Listeria innocua was the most prevalent. Indirect sources for Listeria in food processing plants were soil and effluents. Listeria innocua and L. monocytogenes were isolated from soil samples taken from both outdoor and indoor of food plants, whereas L. innocua, L. monocytogenes and L. welshimeri were recovered from their effluents. The supplied tap water samples of the factories were free from the bacterium. Examination of 42 persons working in these food plants revealed that listerias were present in 14 persons of which eight were carriers for L. innocua, five were carriers for L. monocytogenes and one person was carrier for both L. innocua and L. monocytogenes in the same time. The pathogen was most frequently isolated from nose/nasal secretions of 11 persons, hands of seven persons and faces of two persons. The study indicates that Listeria spp. are common in the food industrial environment including food handlers. Perhaps correct disinfection and hygiene will prevent or at least diminish cross-contamination of the food product.

Ultrasensitive Detection of Salmonella and Listeria monocytogenes by Small‐Molecule Chemiluminescence Probes

“…Both E. coli and C. freundii served as negative controls,asthey do not possess aC 8-esterase.M oreover,t hese bacteria may be present in stool samples tested for Salmonella,a st hey occur in the intestinal tracts of animals and humans. [40][41][42] Both probes were also added to sterile saline,a nd the luminescence amounted was used to normalize the measured signal obtained for each bacterial strain. [41] For L. monocytogenes detection, CLLP was added to cultures of the following bacterial strains: E. coli ATCC 25922, Listeria innocua (6a) ATCC 33090, L. monocytogenes (4b) ATCC 19115 (L. monocytogenes 1) and Listeria monocytogenes ATCC 7644 (L. monocytogenes 2).…”

“…[16,42] MUCAP and MUMIP are mostly used in chromogenic nutrient agar plates for confirmatory testing. [16,42] MUCAP and MUMIP are mostly used in chromogenic nutrient agar plates for confirmatory testing.…”

Ultrasensitive Detection of Salmonella and Listeria monocytogenes by Small‐Molecule Chemiluminescence Probes

“…Moreover, they may be present in food samples tested for L. monocytogenes , as L. innocua occurs in food sources, and some serotypes of E. coli may as well. Additionally, as mentioned above, E. coli may also be present in stool samples …”

“…With chemiluminescence probes CLSP and CLLP in hand, we next sought to compare their ability to detect Salmonella and L. monocytogenes with that of currently existing fluorescence methods. 4‐Methylumbelliferyl caprylate ( MUCAP ) and 4‐methylumbelliferyl myo‐inositol 1‐phosphate ( MUMIP ) are two commercially available fluorogenic probes for the detection of Salmonella and L. monocytogenes , respectively . MUCAP and MUMIP are mostly used in chromogenic nutrient agar plates for confirmatory testing .…”

Ocorrência e caracterização sorológica e genotípica de Listeria monocytogenes em indústrias de queijo do Estado de São Paulo.

“…As imagens dos géis foram normalizadas com o marcador de peso molecular MURAOKA et al, 2003;VAN KESSEL et al, 2004). (KABUKI et al, 2004;KELLS;GILMOUR, 2004) e ralos (CHARLTON, KINDE, JENSEN, 1990;WALKER et al, 1991;EL SHENAWY, 1998;FIGUEIREDO, 2000;KABUKI, 2004) encontraram prevalência de 2,7% de L. monocytogenes em amostras coletadas de indústria de laticínios de leite de ovelha, inferior à encontrada neste trabalho (7,12% -Tabela 6).…”