Un probiótico definido aumenta la exclusión de Salmonella enterica serovariedad Enteritidis durante la crianza de aves ligeras / Enhancement of competitive exclusion by a defined probiotic on Salmonella enterica serovar Enteritidis colonization during rearing of Leghorn chicks

Competitive exclusion degree from a defined (DP) and undefined probiotic (UDP) administered to one-day Leghorn chicks and challenged with 1 x 10(8) CFU of Salmonella enterica serovar Enteritidis fagotype 13A (SE) was evaluated. Birds with DP at 20 day old showed 21.7% of SE positive isolates in liver-spleen (LS), less than 51.7% recorded from birds without any probiotic. In a second study, birds that received DP living together with a group inoculated with SE at third day old, showed 7.5% infection in LS at 13 day of age and 12.5% at 15 day. Whereas, SE inoculated group had 75% and 57.5% of SE isolates, respectively. A third group, living with the last two, without DP or SE showed 27.5% of SE in LS at 13 day, and only 10% at 15 day of age. DP group at 13 day of age, showed a decrease of 75% of SE colonization at cecal tonsils (CT), instead, SE inoculated group was 100% colonized; at 15 day of age, DP decreased 51.4% of SE colonization in CT, while control group showed a decrease of 42.5%, and 68.6% of SE in CT at 13 and 15 days, respectively. In a third study, a DP booster group was dosed three times, at 14 days of age, it had only 4.5% of SE isolates from LS. Birds without DP showed 34.6% of SE isolates, and the group inoculated with only one dose had 17.2% of SE positive birds. DP booster group showed 22.7% of SE in CT, the group with one dose had 62% of SE isolates; birds without DP decreased only 3.9% of SE colonization. DP showed greater margin of protection, decreased horizontal transmission of SE PT13A in LS and CT, and it has good transmission potential. DP booster treatment was better than only one dose. DP is a good alternative for SE prevention and eradication in commercial poultry.

Se determinó el grado de exclusión de un probiótico definido (PECD) y otro no definido (PECND) administrados a aves de la raza Leghorn, de un día de edad, sobre el desafío con 1 x 10(8) UFC de Salmonella enterica serovariedad Enteritidis fagotipo 13A (SE). Las aves con PECD al día 20 mostraron 21.7% de aislamientos positivos de SE en hígado-bazo (HB), menor al 51.7% observado en las aves sin probiótico. En un segundo estudio, las aves que recibieron el PECD y convivieron en piso con un grupo inoculado con SE desde el día tres, mostraron una infección en HB de 7.5% al día 13 y 12.5% al día 15 de edad, el grupo inoculado mostró 75% y 57.5% de SE, respectivamente. Un tercer grupo que convivió con los dos anteriores y no recibió probiótico ni SE, mostró 27.5% de SE en HB al día 13 y sólo 10% al día 15. El grupo con el probiótico muestra una reducción de 75% de SE en tonsilas cecales (TC) al día 13, mientras que el inoculado fue 100% colonizado; al día 15, el probiótico redujo 51.4% la colonización, mientras que el testigo mostró una reducción de 42.5% al día 13 y de 68.6% al día 15. En un tercer estudio un grupo redosificado tres veces, al día 14 de edad disminuyó el porcentaje de aislamientos de SE en HB a tan sólo 4.5%. Las aves que no recibieron el probiótico mostraron 34.6% de SE y las aves que lo recibieron una sola vez mostraron 17.2%. El grupo con refuerzo mostró 22.7% de colonización en TC, el grupo con una dosis mostró 62% de aves positivas a SE, las aves sin probiótico redujeron sólo 3.9% esta colonización. El grupo con PECD muestra mayor margen de protección, reduce la transmisión horizontal de SE PT13A en HB y TC; exhibe además un buen potencial de transmisión. El refuerzo de dosificación del PECD fue mejor que una sola toma. El PECD constituye una buena alternativa en la prevención y erradicación de la SE en la avicultura comercial.

Phylogenetic overdispersion of plant species in southern Brazilian savannas / Dispersão filogenética de espécies de plantas em savanas no Sudeste do Brasil

Ecological communities are the result of not only present ecological processes, such as competition among species and environmental filtering, but also past and continuing evolutionary processes. Based on these assumptions, we may infer mechanisms of contemporary coexistence from the phylogenetic relationships of the species in a community. We studied the phylogenetic structure of plant communities in four cerrado sites, in southeastern Brazil. We calculated two raw phylogenetic distances among the species sampled. We estimated the phylogenetic structure by comparing the observed phylogenetic distances to the distribution of phylogenetic distances in null communities. We obtained null communities by randomizing the phylogenetic relationships of the regional pool of species. We found a phylogenetic overdispersion of the cerrado species. Phylogenetic overdispersion has several explanations, depending on the phylogenetic history of traits and contemporary ecological interactions. However, based on coexistence models between grasses and trees, density-dependent ecological forces, and the evolutionary history of the cerrado flora, we argue that the phylogenetic overdispersion of cerrado species is predominantly due to competitive interactions, herbivores and pathogen attacks, and ecological speciation. Future studies will need to include information on the phylogenetic history of plant traits.

Comunidades ecológicas resultam não somente de processos ecológicos atuais, como a competição e os filtros ambientais, mas também de processos evolutivos passados e contínuos. Com base nessas premissas, podemos inferir mecanismos de coexistência contemporânea a partir das relações filogenéticas das espécies em uma comunidade. Estudamos a estrutura filogenética das comunidades de plantas de quatro áreas de cerrado, no Sudeste do Brasil. Calculamos duas medidas das distâncias filogenéticas das espécies amostradas. Estimamos a estrutura filogenética comparando suas distâncias observadas com a distribuição dessas distâncias em comunidades nulas. Obtivemos comunidades nulas aleatorizando as relações filogenéticas do banco regional de espécies. Encontramos uma dispersão filogenética de espécies de cerrado. Há várias explicações para essa dispersão, dependendo da história filogenética dos traços e das interações ecológicas contemporâneas. Entretanto, com base nos modelos de coexistência entre árvores e gramíneas, nas forças ecológicas dependentes da densidade e na história evolutiva da flora do cerrado, argumentamos que a dispersão filogenética das espécies do cerrado é predominantemente devida às interações competitivas, aos ataques de herbívoros e patógenos e à especiação ecológica. Estudos futuros precisarão incluir informações sobre a história filogenética dos traços das plantas.

Uso de microbiota cecal congelada com crioprotetores em pintos infectados experimentalmente com Salmonella enterica sorovar Enteritidis / Use of frozen cecal microbiota with cryoprotectors in chicks experimentally infected with Salmonella enterica serotype Enteritidis

Pintos de corte com um dia de idade foram tratados com microbiota cecal cultivada em condição de aerobiose, nos tempos de congelamento de 90, 200, 290 e 360 dias, e associada aos crioprotetores sacarose, trealose, dimetilsulfóxido (DMSO) e glicerol. Posteriormente as aves foram desafiadas com Salmonella Enteritidis, visando determinar a eficácia dos tratamentos em relação à quantidade de bactérias viáveis da microbiota que foi maior aos 90 dias (10,58 Log10 UFC/ml), quando as aves foram tratadas com sacarose, e menor aos 290 dias, quando tratadas com glicerol (7,73 Log10 UFC/ml). No tempo zero, todas as aves apresentaram Salmonella (100 por cento) quando tratadas com DMSO e glicerol, com colonização cecal de 4,9 e 5,2 Log10 UFC/g do conteúdo cecal, respectivamente; aos 360 dias nenhuma ave foi infectada, independente do tratamento. A microbiota cecal, independente de tratamento, sempre determinou menor quantidade de S. Enteritidis em qualquer um dos parâmetros pesquisados, quando comparada com a das aves não tratadas. O congelamento em nitrogênio líquido foi eficaz na manutenção da viabilidade da microbiota cecal até 360 dias.

One-day-old broiler chicks were treated with cecal microbiota cultivated under aerobiose conditions, frozen during 90, 200, 290 and 360 days and associated with different cryoprotectors such as sucrose, trehalose, DMSO and glycerol. Subsequently, the birds were challenged with Salmonella Enteritidis in order to determine the efficacy of the different treatments in relation to the quantity of viable bacteria, which was higher at 90 days when treated with sucrose (10.58 log10 CFU/ml) and lower at 290 days when treated with glycerol (7.73 log10 CFU/ml). The quantity of infected birds was 100 percent in 0 time, when the cecal colonization by S. Enteritidis was 4.9 and 5.2 log10 CFU/g of cecal content, respectively treated with DMSO and glycerol. No bird was infected at 360 days, irrespectively of the treatment. In all treatments, the cecal microbiota always determined a lesser quantity of S. Enteritidis for all the studied parameters compared to non-treated birds. Frozen in liquid nitrogen was effective in maintaining the viability of cecal microbiota during the experimental period of 360 days.

Competitive exclusion against Salmonella gallinarum of Salmonella enteritidis infected chickens

To evaluate the degree of competitive exclusion against Salmonella gallinarum(S. gallinarum) of Salmonella enteritidis(S. enteritidis) infected chickens, fifty-six, 4-week old Hyline layer suspected of S. enteritidis infection were challenged with S. gallinarum. All chickens were tested for S. enteritidis isolation using cloacal swabs and serum plate agglutination test using S. enteritidis Ag. before challenge and classified into four groups(SE isolated, SE nonisolated, SE seropositive and SE seronegative). None of the SE isolated and the SE seropositive groups died after challenge and the average weight gains were 245.5g and 254.6g, respectively. But in the SE nonisolated and the SE seronegative groups, mortality was 18.2% and 20.6% and the average weight gains were 150.1g and 111.2g. The incidence of reisolation of S. gallinarum of the SE isolated and the SE seropositive groups were 41.7% and 47.6% from liver, 33.3% and 47.6% from spleen and 8.3% and 14.3% from cecum, respectively, and the SE nonisolated and the SE seronegative group were 63.6% and 64.7% from liver, 84.1% and 88.2% from spleen and 47.7% and 52.9% from cecum. The serological response of the SE isolated and the SE seropositive groups hardly changed from 75.0 and 81.8% before challenge to 75.0 and 85.7% after. But, the other two groups were found to be significantly higher after challenge and increased from 0 and 18.2% to 100%. Consequently, S. enteritidis preinfected chickens were found to be significant different in terms of mortality, weight gain, reisolation of S. gallinarum and serological response compared to noninfected chickens. Moreover, our study shows that S. enteritidis infected chickens appear strong competitive exclusion against the colonization of S. gallinarum.