Incidence of Listeria monocytogenes in two milk processing environments, and assessment of Listeria monocytogenes blood agar for isolation. 2004

J Kells, and A Gilmour
Food Microbiology, Department of Food Science, Queen's University Belfast, Newforge Lane, Belfast, Northern Ireland BT9 5PX, UK. jkells@fsai.ie

A year-long survey of two Northern Ireland milk processing plants for Listeria monocytogenes was carried out. Sample sites included the milk processing environment (walls, floors, drains, and steps), processing equipment, raw and pasteurised milk. The FDA listeria-selective enrichment procedure was used to process samples and an additional agar medium, L. monocytogenes Blood Agar (LMBA), was utilized as part of the isolation procedure in order to compare its performance to that of the recommended Oxford and Palcam agars. LMBA proved to be a very useful tool and was able to detect L. monocytogenes from 94.1% of sites compared to the 76.5% and 79.4% detection rate displayed by Oxford and Palcam agars, respectively. The overall incidence of listeria on equipment was 18.8% (6.3% L. monocytogenes), in the environment was 54.7% (40.6% L. monocytogenes) and in raw milk 44.4% (22.2% L. monocytogenes). On one occasion, L. welshimeri was isolated from pasteurised milk, probably demonstrating post-pasteurisation contamination of product. The main environmental sources of L. monocytogenes were considered to be a floor drain and stainless steel steps.

UI MeSH Term Description Entries
D008089 Listeria monocytogenes A species of gram-positive, rod-shaped bacteria widely distributed in nature. It has been isolated from sewage, soil, silage, and from feces of healthy animals and man. Infection with this bacterium leads to encephalitis, meningitis, endocarditis, and abortion.
D008892 Milk The off-white liquid secreted by the mammary glands of humans and other mammals. It contains proteins, sugar, lipids, vitamins, and minerals. Cow Milk,Cow's Milk,Milk, Cow,Milk, Cow's
D004866 Equipment Contamination The presence of an infectious agent on instruments, prostheses, or other inanimate articles. Contamination, Equipment,Contaminations, Equipment,Equipment Contaminations
D005516 Food Microbiology The presence of bacteria, viruses, and fungi in food and food products. This term is not restricted to pathogenic organisms: the presence of various non-pathogenic bacteria and fungi in cheeses and wines, for example, is included in this concept. Microbiology, Food
D005525 Food-Processing Industry The productive enterprises concerned with food processing. Industry, Food-Processing,Food Processing Industry,Food-Processing Industries,Industries, Food-Processing,Industry, Food Processing
D000362 Agar A complex sulfated polymer of galactose units, extracted from Gelidium cartilagineum, Gracilaria confervoides, and related red algae. It is used as a gel in the preparation of solid culture media for microorganisms, as a bulk laxative, in making emulsions, and as a supporting medium for immunodiffusion and immunoelectrophoresis.
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012680 Sensitivity and Specificity Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed) Specificity,Sensitivity,Specificity and Sensitivity
D015169 Colony Count, Microbial Enumeration by direct count of viable, isolated bacterial, archaeal, or fungal CELLS or SPORES capable of growth on solid CULTURE MEDIA. The method is used routinely by environmental microbiologists for quantifying organisms in AIR; FOOD; and WATER; by clinicians for measuring patients' microbial load; and in antimicrobial drug testing. Agar Dilution Count,Colony-Forming Units Assay, Microbial,Fungal Count,Pour Plate Count,Spore Count,Spread Plate Count,Streak Plate Count,Colony Forming Units Assay, Microbial,Colony Forming Units Assays, Microbial,Agar Dilution Counts,Colony Counts, Microbial,Count, Agar Dilution,Count, Fungal,Count, Microbial Colony,Count, Pour Plate,Count, Spore,Count, Spread Plate,Count, Streak Plate,Counts, Agar Dilution,Counts, Fungal,Counts, Microbial Colony,Counts, Pour Plate,Counts, Spore,Counts, Spread Plate,Counts, Streak Plate,Dilution Count, Agar,Dilution Counts, Agar,Fungal Counts,Microbial Colony Count,Microbial Colony Counts,Pour Plate Counts,Spore Counts,Spread Plate Counts,Streak Plate Counts
D015994 Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from PREVALENCE, which refers to all cases in the population at a given time. Attack Rate,Cumulative Incidence,Incidence Proportion,Incidence Rate,Person-time Rate,Secondary Attack Rate,Attack Rate, Secondary,Attack Rates,Cumulative Incidences,Incidence Proportions,Incidence Rates,Incidence, Cumulative,Incidences,Person time Rate,Person-time Rates,Proportion, Incidence,Rate, Attack,Rate, Incidence,Rate, Person-time,Rate, Secondary Attack,Secondary Attack Rates

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