Quantification of Listeria spp. contamination on shell and flesh of cooked black tiger prawns (Penaeus monodon)

Aims: To quantify Listeria levels on the shell and flesh of artificially contaminated cooked prawns after peeling, and determine the efficacy of Listeria innocua as a model for L. monocytogenes in this system. Methods and Results: A L. monocytogenes and L. innocua strain were inoculated separately onto cooked black tiger prawns using two protocols ( immersion or swabbing with incubation). Prawns were peeled by two methods ( gloved hand or scalpel and forceps) and numbers of Listeria on shells, flesh and whole prawn controls were determined. Prawns were exposed to crystal violet dye to assess the penetration of liquids. Regardless of preparation method or bacterial strain there were ca 1log(10) CFU more Listeria per shell than per peeled prawn. Dye was able to penetrate to the flesh in all cases. Conclusions: Shell-on prawns may be only slightly safer than shell-off prawns. Listeria innocua is an acceptable model for L. monocytogenes in this system. Significance and Impact of the Study: Reduced risk from L. monocytogenes on prawns can only be assured by adequate hygiene or heating

Microbiological counting in lamb carcasses from an abattoir in São Paulo, Brazil Contagens microbiológicas em carcaças ovinas de um abatedouro de São Paulo, Brasil

The consumption of lamb meat in Brazil has increased in the last years but little information about the microbiological quality of this product is available. To evaluate the hygienic-sanitary conditions of lamb carcasses, the quantification of microorganism populations indicators (mesophiles and psychrotrophs; total and thermotolerant coliforms; Escherichia coli; moulds and yeasts) and the pathogenic microorganisms indentification (Salmonella sp. and Listeria spp.) were performed. A total of 60 lamb carcasses were sampled from one abattoir in São Paulo. Swab samples were collected from three points (forequarter, back and hindquarter) on the muscle surface after carcasses final washing. Statistical analysis consisted of descriptive evaluation of the results whose counts were grouped by intervals of microorganism populations. Counts ranged from 1.0 x 10¹ to 8.0 x 10(4) colony-forming unit cm-2 (CFU cm-2) for mesophiles; 1.0 x 10(0) to 4.4 x 10(4)CFU cm-2 for psychrotrophs; < 1.0 x 10(0) to 4.4 x 10(4)CFU cm-2 for moulds and yeasts; < 0.3 to > 32.0 most probable number/cm² (MPN cm-2) for total and thermotolerant coliforms and Escherichia coli. Salmonella sp. and Listeria spp. were not found in any of the carcasses. Most carcasses presented low counts for all microorganisms. Overall results may be explained by the small size of the industry where the study was taken. Results suggest that good microbiological quality lamb meat is possible to be obtained, but improvement in hygienic-sanitary conditions is still required.<br>O consumo de carne ovina tem aumentado nos últimos anos, no Brasil. Entretanto, pouca informação sobre a qualidade desse produto está disponível. Com o intuito de avaliar as condições higiênico-sanitárias das carcaças ovinas, foram realizadas a quantificação das populações de microrganismos indicadores (mesófilos e psicrotróficos; coliformes totais e termotolerantes; Escherichia coli; bolores e leveduras) e a identificação de microrganismos patogênicos (Salmonella sp. and Listeria spp.). Um total de 60 carcaças foram amostradas em um frigorífico, em São Paulo, entre fevereiro e dezembro de 2006. Suabes foram coletados em três pontos (dianteiro, lombo e traseiro), na superfície muscular das carcaças, após a lavagem final destas. A análise estatística consistiu na avaliação descritiva dos resultados cujas contagens foram agrupadas em intervalos populacionais. As contagens variaram de 1,0 x 10¹ a 8,0 x 10(4)UFC cm-2 para mesófilos; de 1,0 x 10(0) a 4,4 x 10(4)UFC cm-2 para psicrotróficos; de < 1,0 x 10(0) a 4,4 x 10(4)UFC cm-2 para bolores e leveduras; de < 0,3 a > 32,0 NMP cm-2 para coliformes totais e termotolerantes; e Escherichia coli. Salmonella sp. e Listeria spp. não foram detectadas em nenhuma das amostras coletadas nas carcaças. A maioria das carcaças apresentou baixas contagens para todas as categorias de microrganismos. Os resultados encontrados podem ser explicados pelo pequeno tamanho da indústria onde o trabalho foi realizado e sugerem que carne ovina de boa qualidade microbiológica pode ser obtida. No entanto, melhorias nas condições higiênico-sanitárias ainda são necessárias