PHYLOGENOMIC COMPARISONS BETWEEN Listeria monocytogenes STRAINS ISOLATED FROM DIFFERENT SOURCES AND GEOGRAPHIC REGIONS.

Listeria monocytogenes is the causative agent of listeriosis which may cause a range of diseases from gastroenteritis, meningitis and death. In fact, disease outcome can be related to strain serotype/lineage thus molecular analyses has demonstrated that L. monocytogenes is a highly diverse species which can be grouped into three lineages. Whole-genome microarray can be employed to study phylogenetic relationships among Listeria strains either species or serotype level, in addition to demonstrate differences on their virulence potential and/or environmental adaptation. The aim of this study was the whole genome comparison of L. monocytogenes strains from different origins. Ninety-nine L. monocytogenes strains from different geographical origins (Brazil, Denmark, Austria, Ireland, USA and unknown), including clinical strains (humans and animals), food and food industries strains were analysed. DNA from all strains were competitively hybridized on to a L. monocytogenes DNA microarray based on the whole-genome sequence L. monocytogenes EGD-e. DNA labeling and hybridization protocol were followed according to Dorrell et al., (2001). Data acquisition, processing and comparative phylogenomics were performed as previously described by Stabler et al. (2006). Comparative phylogenomics clustered the L. monocytogenes strains into two central clades which is representative of the two main lineages of this species. In addition each of these clades were divided into two further subclades. Clade formation was independent of the geographical origin of strains with the exception of the clade containing persistent strains (strains that persist in food-processing environment), where none of the Brazilian strains were present. It was found 18 specific genes for lineage I strains (1/2a and 1/2c serotypes). These genes are related to carbohydrate metabolism, two component regulatory system, ABC transporter complex and bvrB and bvrC genes. Significantly all persistent strains clustered together in the same lineage I clade. We achieved a set of unique genes belonging exclusively to L. monocytogenes persistent strains pointing to be responsible for its adaptation profile. The genes are involved in stress resistance and are related to carbohydrate transport and metabolism, environmental information processing, signal transduction mechanisms, cell surface protein, amino acid transport and metabolism, nucleotide transport and metabolism, translation, cell wall biogenesis, replication, recombination and repair, transport of small molecules similar to ABC transporter, metabolism of lipids and unknown function. Interestingly from 14 virulence listed genes most of them were present in all studied L. monocytogenes strains with exception of inlE and inlG genes. These findings indicate that genetic variability of L. monocytogenes strains point to niche adaptation instead virulence differentiation despite of different origins. Persistent strains clustered suggesting genetic origin to survival in this environment.Listeria monocytogenes é o agente causador da listeriose, uma infecção severa que pode cursar com sintomas que variam desde gastroenterites, meningites e até mesmo a morte. De fato, o desenvolvimento da doença pode ser relacionado a determinados sorotipos/linhagens das cepas de Listeria. Análises moleculares dos diferentes sorotipos/linhagens de L. monocytogenes, demonstraram que esta espécie é amplamente diversa, a qual pode ser agrupada em três linhagens. O estudo completo de genomas, baseado na técnica de microarray, pode ser empregado para estudar a relação filogenética entre cepas de Listeria tanto em nível de espécie, quanto em nível de sorotipo. Não obstante, a técnica de microarray visa evidenciar as diferenças no potencial patogênico e/ou adaptativo das cepas. O objetivo deste estudo foi a comparação filogenética entre cepas de L. monocytogenes isoladas de diferentes fontes. Foram analisadas 99 cepas de L. monocytogenes de diferentes origens geográficas (Brasil, Dinamarca, Áustria, Irlanda, Estados Unidos da América e fontes desconhecidas), incluindo cepas clínicas (humanas e animais), de alimentos e de indústrias alimentícias. O DNA das cepas teste foi hibridizado em DNA microarrays de L. monocytogenes baseado em seqüências do genoma de L. monocytogenes EGD-e. Os protocolos para marcação e hibridização do DNA seguiram as recomendações de Dorrell et al., (2001). A aquisição de dados, o processamento e as comparações filogenômicas foram realizadas conforme previamente descrito por Stabler et al. (2006). Comparações filogenômicas agruparam as cepas de L. monocytogenes em dois clades centrais, os quais são representativos das duas principais linhagens desta espécie. Além disso, cada um destes clades foram subdivididos em mais dois sub-clades. A formação dos clades foi independente da origem geográfica das cepas, com exceção do clade contendo cepas persistentes (cepas que persistem no ambiente de processamento de alimentos), onde nenhuma cepa Brasileira esteve presente. Foram identificados 18 genes específicos para as cepas da linhagem I (sorotipos 1/2a e 1/2c). Esses genes são relacionados ao metabolismo de carboidratos, sistema regulatório two component, complexo de transporte ABC e aos genes bvrB e bvrC. A grande maioria das cepas persistentes se agrupou no mesmo clade pertencente à linhagem I. Foi obtido um conjunto de genes únicos pertencentes exclusivamente às cepas persistentes de L. monocytogenes, os quais sugerem serem os responsáveis pelo perfil adaptativo destas cepas. Os genes são envolvidos em resistência ao estresse e são relacionados ao transporte e metabolismo de carboidratos, processamento de informação ambiental, mecanismos de transdução de sinais, proteína de superfície celular, transporte e metabolismo de aminoácidos, transporte e metabolismo de nucleotídeos, tradução, biogênese de parede celular, replicação, recombinação e reparo, transporte de pequenas moléculas similar ao transportador ABC, metabolismo de lipídios e de função desconhecida. Dos 14 genes de virulência listados a maioria deles esteve presente em todas as cepas de L. monocytogenes estudadas, com exceção dos genes inlE e inlG. Estes dados sugerem que, apesar das distintas origens de isolamento, a variabilidade genética das cepas de L. monocytogenes é direcionada para adaptação ambiental, ao invés da diferenciação visando virulência

Listeria monocytogenes: monitoramento desse perigo biológico na cadeia produtiva de frangos do sul do Rio Grande do Sul

Listeria monocytogenes é uma bactéria patogênica que se tornou um grande desafio para as indústrias de alimentos, entre elas a de frangos, assim como para os órgãos de vigilância sanitária. Apesar da produção de frangos estar em expansão na região sul do Rio Grande do Sul, não há relatos sobre esse patógeno, dessa forma, objetivou-se avaliar a prevalência de L. monocytogenes e de seus sorotipos nos diversos segmentos dessa cadeia produtiva. Nos aviários isolou-se L. monocytogenes em 2,9% (1/35) das amostras de swabs cloacais, não se isolando o microrganismo em amostras provenientes das camas de aviários. No abatedouro, 11,7% (15/128) das amostras apresentaram contaminação por L. monocytogenes e nos frangos resfriados procedentes do comércio, a prevalência foi de 33,3% (15/45).Observou-se que 51,6% (16/31) das cepas de L. monocytogenes pertenciam ao sorotipo 1/2b; 22,5% (7/31) ao sorotipo 4e; 16,1% (5/31) ao sorotipo 1/2a; 6,4% (2/31) ao sorotipo 4b; e 3,2% (1/31) ao sorotipo 1/2c. Há disseminação de L. monocytogenes na cadeia produtiva de frangos da região sul do Rio Grande do Sul e a presença de sorotipos prevalentes em casos/surtos de listeriose traz preocupação à saúde pública

Carcass characteristics and meat quality of Aberdeen Angus steers finished on different pastures

The present study was conducted to assess carcass features, physicochemical and sensory parameters of meat from steers finished on three types of pastures: natural pasture; natural pasture improved, fertilized and oversown with winter species; and annual summer grassland. The experiment was conducted from December 14, 2009 to November 30, 2010, with treatments distributed in a completely randomized design with a different number of replicates. Animals were used as experimental units. Experimental animals were Aberdeen Angus steers with twenty months of initial age and 354±27.4 kg of live weight, on average. The highest average daily gains were obtained for the annual summer grassland. There was no effect of treatments on carcass conformation. The highest carcass yield was obtained on the improved natural pasture. Forequarter yield, side cut yield and longissimus muscle area were similar between the pastures. Moisture and total lipids were not affected by the pasture. Thawing and cooking losses were higher in improved natural pasture and lower in sorghum pasture. Regardless of the treatment, the meat had luminosity ranging from intermediate to dark, high in red, high in yellow, and considered within the normal range for beef. Meat of higher shear force was found in natural pasture, and lower shear force was observed in meat from annual summer grassland. Average live weight daily gain explained 18% of the shear force. Sensory evaluation by duo-trio test showed differences between samples from distinct pastures in flavor. All the studied systems allow for desirable characteristics in carcass and meat

Carcass characteristics and meat quality of Aberdeen Angus steers finished on different pastures

The present study was conducted to assess carcass features, physicochemical and sensory parameters of meat from steers finished on three types of pastures: natural pasture; natural pasture improved, fertilized and oversown with winter species; and annual summer grassland. The experiment was conducted from December 14, 2009 to November 30, 2010, with treatments distributed in a completely randomized design with a different number of replicates. Animals were used as experimental units. Experimental animals were Aberdeen Angus steers with twenty months of initial age and 354±27.4 kg of live weight, on average. The highest average daily gains were obtained for the annual summer grassland. There was no effect of treatments on carcass conformation. The highest carcass yield was obtained on the improved natural pasture. Forequarter yield, side cut yield and longissimus muscle area were similar between the pastures. Moisture and total lipids were not affected by the pasture. Thawing and cooking losses were higher in improved natural pasture and lower in sorghum pasture. Regardless of the treatment, the meat had luminosity ranging from intermediate to dark, high in red, high in yellow, and considered within the normal range for beef. Meat of higher shear force was found in natural pasture, and lower shear force was observed in meat from annual summer grassland. Average live weight daily gain explained 18% of the shear force. Sensory evaluation by duo-trio test showed differences between samples from distinct pastures in flavor. All the studied systems allow for desirable characteristics in carcass and meat