Ocorrência de Cryptosporidium spp. na cadeia produtiva de alface (Lactuca sativa L.), sua captura e retenção por biofilmes de Pseudomonas fluorescens e seu controle por surfactantes

• Autor(a) principal: Careli, Roberta Torres
• Data de Publicação: 2009
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/420
• topic: Cryptosporidium e Giardia; Alface; Higienização; Cryptosporidium and Giardia; Lettuce; Higienization; CNPQ::CIENCIAS AGRARIAS::CIENCIA E TECNOLOGIA DE ALIMENTOS::CIENCIA DE ALIMENTOS

The occurrence of Cryptosporidium spp. and Giardia spp was evaluated on plantations of oily lettuce, variety Vitoria de Santo Antão, on the countryside of Viçosa, Minas Gerais state, on dry and wet seasons. It was found both protozoans in the water, on lettuce, organic fertilizer and soil, at least in one plantation and one season. The main contamination source of both protozoans on lettuce was the water used on the irrigation. The number of microorganisms was affected by rainfall variations, and higher values were observed on the wet season. The microbiological contamination of water, lettuce, organic manure and soil was shown by different bacteriological analysis. It was observed high correlation between the occurrence of Cryptosporidium spp. and Giardia spp. in all the types of samples, except by the fertilizer. High correlations between the protozoans and C. perfringens were found in water samples. The results denoted that some bacteriological indicators, such as the coliform group, cannot predict the presence of protozoans. Besides that, the turbidity of the different sources of water presented higher values on the wet season, which shows high correlation with the presence of Cryptosporidium spp. e Giardia spp. in irrigation water. The ability to remove Cryptosporidium parvum adhered to lettuce leaves, as pure culture and mixed with Pseudomonas fluorescens, was evaluated by using solutions of different concentrations of benzalkonium chloride, Tween 80, and sodium dodecyl sulphate (SDS), after 10 minutes of contact. It was verified that SDS presented better protozoans removal, and its effectiveness increased as the concentration (p < 0,05). It was evaluated the ability to capture and retain oocysts of C. parvum by P. fluorescens biofilms established on polyvinylchloride (PVC) pipes. The number of captured oocysts was higher (p < 0,05) than the number of retained oocysts after increasing the flow in six times. It was verified that the oocysts present little ability to adhere to the PVC surface. The thermodynamic features related to the formation of P. fluorescens biofilm and C. parvum oocysts adhesion on PVC pipes were also evaluated. It was observed that the surfaces of C. parvum and P. fluorescens are hydrophilic, whereas PVC is a hydrophobic material. Such results were confirmed by quantifying the surface free energy (&#916;Gsws).The determination of the total free interaction energy denoted that the adhesion of P. fluorescens biofilm and C. parvum oocysts was thermodynamically favorable (&#916;GadesãoTOT < 0) for all the conditions. The control of P. fluorescens biofilm and C. parvum oocysts adhered to PVC pipes was carried out by applying benzalkonium chloride.The tested concentrations of benzalkonium chloride leaded to an increase (P < 0,05) on the DR number of both microorganisms, as they were submitted to higher concentrations of surfactants. The application of benzalkonium chloride on higienization procedures can be an alternative to control bacteria and protozoan adhered to PVC pipes used on vegetable irrigation. However, some toxicological tests are necessary in order to evaluate the prejudicial effect of the suggested concentration.