Occurrence ofListeriaspecies in ready to eat foods

Abstract

SUMMARYOver 8000 ready to eat foods were examined for the presence of Listeria species.Overall, 5% of foods were found to contain these organisms. Higher occurrence was found in some foods such as chicken (11%) and fish (14%). Most of the Listeria species isolated were L. monocytogenes (49 %) and L. innocua (360%) with lower numbers of other species. No seasonal pattern in the recovery of L. monocytogenes was found. Unsatisfactory or potentially hazardous levels of L. nmonocytoqenes were found in 14 products (< 0-2%), mostly cooked meats.Undercooked chicken products appeared to present the greatest risk for the duration of this survey. The small number of samples which were potentially hazardous suggests that the risk to consumers is not high, and this is confirmed by the absence of clinical cases in the region during the period of study. INTROD)UCTIONListeria have long been recognized as the cause of a range of serious human diseases [1]. Various surveys have shown them to be carried intestinally by 5-70 % [21 and 0 5-92 % of healthy humans [3], and by many animals [4, 5]. Exposure, consumption and carriage often do not lead to development of disease. Immnunocompromised individuals including the immunosuppressed, elderly, pregnant, and those suffering a range of underlying diseases are primarily at risk. The spectrum of disease is broad, ranging from asymptomatic infection and carriage to uncommon cutaneous lesions, flu-like symptoms, various focal infections such as septic arthritis, conjunctivitis, urethritis, endocarditis [3], and the more serious and better recognised conditions of septicaemia, abortion and meningoencephalitis in humans [6]. The virulence [7][8][9][10] and health risks associated with different species and strains have been discussed [11], concluding that Listeria rmonocytogenes is the species of most concern, although the haemolytic species L. seeligeri and L. icanovii are also recognised as potential pathogens [9,12].While L. ntonocytogenes has been found in silage [4], in faeces from both symptomatic and healthy individuals and animals, and at many environmental sites [5,13], the more serious manifestations of infection and invasive disease are thought generally to be the result of eating contaminated food. Elucidation of the epidemiology is nevertheless incomplete [8]. Careful food production, cooking and

Occurrence ofListeriaspecies in prepacked retail sandwiches

“…Six sandwiches contained L. innocua only, 4 contained L. monocytogenes only, and 1 sample contained counts of both species. Six of the 11 sandwiches having raised counts contained chicken, which was found in the other study [9] to be the meat which probably represents the greatest risk to consumers. Potentially hazardous [2] levels ofL.…”

“…Seafood sandwiches had a lower positivity rate than seafoods in the other survey [9]. This is due to most of the seafood used for sandwich filling being canned tuna/salmon, whereas most of that sampled in the other survey was restaurant/takeaway fish.…”

“…bacon, turkey, cheese) means that the percentage positive may be misleading if compared directly with other fillings. This also applies to bacon, cheese, egg and seafood in the earlier study [9] where numbers of these foods sampled were considerably smaller than those of beef, chicken, ham, salad and turkey. L. innocua and L. monocytogenes were the only species isolated in numbers > 100 cfu/g.…”

“…in a number of studies [9,13,14] and this was reflected in sandwiches containing chicken fillings. Three of five sandwiches containing unsatisfactory ( 3 10' cfu/g) or potentially hazardous (3103 cfu/g) numbers of L. monocytogenes also contained chicken as their main filling.…”

“…Generally, sandwiches were found to be positive for Listeria sp. more often than their component foods in another survey [9] conducted simultaneously in the same region. For most sandwiches, the inclusion of salad slightly increased the frequency with which Listeria species were isolated.…”