Characterization of Listeria monocytogenes isolates of food and human origins from Brazil using molecular typing procedures and in vitro cell culture assays.

The spreading of diseases through foods is a worldwide concern. Here, molecular and in vitro cell-culture assays were employed to characterize 63 Brazilian Listeria monocytogenes isolates (food, 47; clinical, 16). Serotype 4b was the most predominant (49%) followed by (1/2)b (30%), (1/2)a (10%), (1/2)c (6%), 3c (3%) and 3b (2%). Ribotyping yielded 17 ribopatterns, which were grouped into four phylogenetic clusters. Cluster A comprised of 39/63 isolates primarily of food origin, and clusters B, C and D contained both food and clinical isolates. Isolates were positive for virulence determinants prfA, hlyA and inlA: clinical isolates were more invasive to Caco-2 cells and expressed high levels of inlA transcripts than the food isolates. Highly invasive isolates also provoked more Ped-2E9 cells to die by apoptosis than the weakly-invasive strains. These data demonstrate a strong genetic relatedness among clinical and food isolates and suggest transmission of a subset of L. monocytogenes strains from food to humans.

Influence of environmental conditions on the expression of virulence factors by Listeria monocytogenes and their use in species identification.

The hemolytic, lecithinase or phosphatidylinositol-specific phospholipase C activities of Listeria monocytogenes can be used to differentiate this pathogenic bacteria from L. innocua, apathogenic, frequently isolated from environmental sources and food. However, the interpretation of these characteristics is problematic because of the variation in the expression of virulence factors by L. monocytogenes, which can be influenced by environmental conditions. We used a cheap, simple plate assay to monitor this expression in strains obtained from various sources and grown under different culture conditions. The results were increasingly significant and were obtained adding activated charcoal and different salts to the culture media, and in some cases changing the culture temperature, all with a rigorous control on the process of media sterilization.

Diagnóstico laboratorial da coqueluche: freqüência do isolamento de Bordetella pertussis de amostras clínicas, por meio da técnica de cultura realizada nos laboratórios regionais do Instituto Adolfo Lutz, São Paulo, Brasil / Pertussis diagnosis: frequency of Bordetella pertussis detection from clinical samples by the culture method performed at regional laboratories of the Instituto Adolfo Lutz, São Paulo, Brazil

A coqueluche é uma doença respiratória infecciosa aguda, causada por Bordetella pertussis, cocobacilos Gram-negativos fastidiosos com requisitos nutricionais complexos. Recentemente foi descrito em vários países o aumento do número de casos da doença - com o acometimento de populações vacinadas - e da sua incidência em adolescentes e adultos. No Brasil, a coqueluche só se tornou doença de notificação compulsória a partir de 2001. O presente trabalho avaliou o índice de positividade no diagnóstico da coqueluche por meio da técnica de cultura de secreção de nasofaringe, realizada segundo Regan e Lowe, 1997, e também a sua freqüência em diferentes faixas etárias, nas regiões de abrangência dos Laboratórios Regionais do Instituto Adolfo Lutz, São Paulo, SP, no período de 2001 a 2005. Os resultados mostraram aumento no número de amostras positivas a partir de 2004, o que pode ter ocorrido em função da maior conscientização dos profissionais envolvidos na investigação e notificação da doença.O maior número de amostras positivas deu-se na faixa etária de 0 a 6 meses (65,0%), com predomínio da faixa de 1 a 3 meses. A taxa de positividade em adolescentes e adultos foi de 19,4%. Os dados obtidos são relevantes para a melhoria do diagnóstico da coqueluche na região estudada e indicam a necessidade de informações adicionais para dar suporte às estratégias de prevenção e prover um melhor entendimento da doença no país.

Pertussis or whooping cough is an acute respiratory infectious disease caused by Bordetella pertussis, a small Gram-negative coccobacillus which has complex nutritional requirements. Several countries have recently reported an increase in pertussis in immunized populations, accompanied by a significant increase among adolescents and adults. In Brazil, pertussis had its epidemiological surveillance established only in 2001. This study evaluated the indices of positivity on culture method performed according to Regan & Lowe, 1997, for pertussis diagnosis in the regions enclosed by the regional laboratories of the Instituto Adolfo Lutz - São Paulo state, Brazil, from 2001 to 2005. An increase in the number of positive samples was observed since 2004, which could be due to a better identification of the disease by health workers involved on its investigation, diagnosis, and notification. According to these results, the young infants presented the highest positivity rate (age 0-6 months, 65.0%). The older age groups (adolescents and adults) showed 19.4% of positivity. These data are relevant for monitoring pertussis diagnosis and for conducting epidemiological studies in the studied regions, and also to provide support to prevention programs.