Abstract
Listeria spp. isolated from different food products and collected from 12 Brazilian states were sent to the Laboratory of Bacterial Zoonoses (Oswaldo Cruz Institute, Brazil) for identification. The aims of this study were to characterize these isolates, from 1990 to 2012, by using biochemical, morphological, and serotyping tests, and to analyze the distribution of L. monocytogenes serotypes on different food products and geographical locations. Serotyping was performed using polyclonal somatic and flagellar antisera. Of 5953 isolates, 5770 were identified as Listeria spp., from which 3429 (59.4%) were L. innocua, 2248 (38.9%) were L. monocytogenes, and 93 (1.6%) were other Listeria spp. L. innocua was predominantly isolated from 1990 to 2000, while L. monocytogenes was from 2001 to 2012. Regarding the serotype distribution in the foods, serotypes 1/2a and 4b were most common in processed meat and ready-to-eat products, respectively; serotypes 1/2a, 1/2b, and 4b were the most common in nonprocessed meat. The results above confirm the presence of the main serotypes of L. monocytogenes in different parts of the food chain from three regions of the country and emphasize the importance of improving the control measures, as tolerance zero policy and microbiological surveillance in Brazil.
Highlights
The genus Listeria includes pathogenic species as Listeria monocytogenes and Listeria ivanovii, the latter is common in warm-blooded animals, and it is widespread in nature
Among the states with isolated Listeria spp. in dairy products, Sao Paulo and Rio Grande do Sul contributed with more strains
While Sao Paulo had a similar number of Listeria strains from milk and cheese, in Rio Grande do Sul cheese was the major source (OR = 8.8, 95% CI = 5.2–14.9, p < 0.01)
Summary
The genus Listeria includes pathogenic species as Listeria monocytogenes and Listeria ivanovii, the latter is common in warm-blooded animals, and it is widespread in nature. Listeria monocytogenes differs from most bacterial food pathogens due its ability to survive harsh environment conditions, grow over a wide temperature range (1–45∘C), and survive under wide pH range (4.5–9.6), high salt concentration (10 to 15% NaCl), and very low water activity (aw = 0.94). It can grow in different types of food products [2]. Its main impact is in immunocompromised individuals, with a high fatality rate of 20% to 30% [3] As it is a foodborne pathogen, individuals are infected predominantly through contaminated food consumption [4]
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