Attractiveness of Golden Hamster infected with Leishmania amazonensis (Kinetoplastida: Trypanosomatidae) to laboratory-reared Lutzomyia longipalpis (Diptera: Psychodidae).

Lutzomyia longipalpis is the primary vector of Leishmania infantum in the Americas and a permissive vector for Leishmania amazonensis. Previous studies showed that Leishmania infantum-infected hosts can release different volatile organic compounds (VOCs) compared with uninfected hosts, presenting a higher attractiveness to vectors. In this study, we aimed to evaluate a possible effect of L. amazonensis infection of golden hamsters in three parameters: attractiveness to Lu. longipalpis females; blood volume ingested by sand fly females; and VOCs released by the animals.. Attractiveness was measured indirectly by the number of Lu. longipalpis females that blood fed in each L. amazonensis-infected and uninfected animal. For VOCs extraction, solid phase micro extraction fibers were used, which were analyzed by gas chromatography-mass spectrometry. Behavioral trials did not show any effect of L. amazonensis infection on the attraction of sand flies nor difference on blood meal rates of Lu. longipalpis fed in both goups of hamsters. Additionally, there was no difference between the VOCs profiles of L. amazonensis-infected or uninfected hamsters.

Influence of Leishmania (Viannia) braziliensis infection on the attractiveness of BALB/c mice to Nyssomyia neivai (Diptera: Psychodidae).

BACKGROUND: Phlebotomine sand flies are vectors for several pathogens, with Leishmania being the most important. In Brazil, the main aetiological agent of American cutaneous leishmaniasis (ACL) is Leishmania (Viannia) braziliensis, and Nyssomyia neivai is one of its main vectors in São Paulo state and other areas of South America. Similar to other haematophagous insects, sand flies use volatile compounds called kairomones to locate their hosts for blood meals. A possible increase in the attractiveness of hosts infected with Leishmania infantum to their vectors has been demonstrated. In the present study, we aimed to investigate whether L. braziliensis-infected hosts present higher attractiveness to Ny. neivai and to identify differences in the volatile compounds released by infected and uninfected mice. RESULTS: Behavioural experiments in which sand fly females directly fed on infected or uninfected mice showed no significant differences in the attractiveness of the mice or the blood volume ingested. Y-tube olfactometer bioassays also revealed no significant differences in the attractiveness of these hosts to Ny. neivai. No differences were observed in the profiles of the volatile compounds released by the two groups of mice. However, PCA and cluster analysis were able to classify the 31 identified compounds into three clusters according to their abundances. This classification showed a possible role for individual variation in the absence of differences in volatile profiles and attractiveness between infected and uninfected mice. CONCLUSION: In this first cross-sectional study with an aetiological agent of ACL, there were no statistically significant differences in the attractiveness of infected hosts to their vector.

Solid phase microextraction, sand flies, oviposition pheromones, plaster of Paris and siloxanes-What is in common?

Sand flies are natural hosts of various microorganisms. Due to their epidemiological importance, sand fly colonies are kept in laboratories to be studied in terms of their biology and vector/host/parasite interactions. In order to investigate the presence of oviposition pheromones in Nyssomyia neivai, experiments using Solid Phase Microextraction (SPME) were performed. However, siloxanes which is an external class of contamination, present in breeding containers made by plaster used to maintain sand flies in colonies, may be hindered the experiments.

Determination of yeast killer activity in fermenting sugarcane juice using selected ethanol-making strains

A atividade 'killer' poderia garantir às leveduras fermentativas uma vantagem competitiva sobre outras linhagens durante a fermentação etanólica, no entanto, pouco se sabe sobre o papel do sistema 'killer' nesse tipo de fermentação alcoólica. A seleção de linhagens 'killer' altamente produtivas pode ser uma abordagem interessante. Vinte e quatro dentre 342 leveduras isoladas do processo fermentativo mostraram atividade 'killer' e 3 delas foram selecionadas para a avaliação da eficiência fermentativa em sistema de batelada com reciclo de células, em escala de frascos e fermentador. As 3 linhagens 'killer' selecionadas não apresentaram resultados similares àqueles apresentados pelo fermento prensado (panificação) em relação aos rendimentos em etanol (0,07-0,18; 0,12-0,20; 0,10-0,13; 0,22-0,25 g/g, respectivamente) e biomassa (0,19-0,26; 0,33-0,39; 0,13-0,27; 0,47-0,61 g/g, respectivamente) e eficiência fermentativa (12,3-36,3; 21,0-40,0; 19,3-26,3; 47,6-54,0 %, respectivamente) em caldo de cana-de-açúcar, em frascos. Em fermentador, observou-se o mesmo comportamento. No entanto, elas mostraram alta viabilidade celular e atividade 'killer' (usando filtrado livre de células) ao longo dos ciclos fermentativos, a despeito das condições desfavoráveis do meio, como alta variação de pH do meio (de 5,5-6,0 a 3,0-4,0), baixa aeração e temperatura mais alta (30oC), as quais não são as ideais para a produção/atividade das toxinas 'killer'. Uma linhagem de Pichia (CCA 510) mostrou os melhores resultados entre as linhagens 'killer' testadas, além de exibir uma poderosa atividade 'killer' contra 92% de leveduras fermentativas isoladas do processo e contra o fermento prensado. Demonstrou também atividade 'killer' (usando preparado de toxina bruta) em temperaturas elevadas (38oC) e baixo pH (4,0) após 72 horas de incubação, sob condições proliferativas e não-proliferativas. Os resultados permitem indicar que a atividade 'killer' deve ser uma característica a ser avaliada na seleção de linhagens para a fermentação etanólica, além de outras características baseadas na produtividade, uma vez que pode assegurar a permanência da linhagem selecionada durante o processo.