The investigations of the antibacterial actions, observed in ternary associations involving silver nanoparticles (AgNPs), chitosan and the antibiotics azithromycin (AZ), levofloxacin (LE) or tetracycline (TE), against Gram-negative and Gram-positive bacterial strains, were performed by in vitro antimicrobial susceptibility testing and checkerboard assays. The pH impact in the culture medium was carefully discarded, but preserving the best conditions for solubilizing chitosan. The synergistic antibacterial effects were observed in the most combinations of AgNPs, chitosan and antibiotic, leading to a reduction from 37 to 97% in the minimum inhibitory concentration of the drugs. The mechanisms for the enhanced antimicrobial effects were proposed based on the investigations of the adsorptions of the drugs on the silver surfaces through surface-enhanced Raman scattering (SERS) spectroscopy.

Genótipos de mamoeiro (Carica papaya) ('NT Red', 'Golden', 'Baixinho de St. Amália', 'Sunrise Solo', 'Cross Paris', 'Tailândia Verde', 'Tailândia Roxo', 'Tailândia Roxão', 'Sekati' e 'Tainung-1') foram avaliados quanto à reação à varíola (Asperisporium caricae) e à podridão-do-pé (Phytophthora palmivora). O estudo foi conduzido em uma área com plantas naturalmente infectadas com ambos os patógenos e sob telado utilizando solo naturalmente infestado com P. palmivora. A severidade de varíola foi avaliada usando-se uma escala, de 1 (0-3% da superfície coberta por lesões) a 6 (>de 50% da superfície coberta por lesões). As avaliações foram feitas entre março e abril / 2003 e entre outubro 2003 e fevereiro 2004. A podridão-do-pé foi avaliada, no campo, por incidência em cada cultivar nos mesmos períodos. Nos experimentos sob telado a severidade da doença por P. palmivora foi avaliada em cada planta utilizando-se a seguinte escala: 0- sem sintomas; 1- até 50% de murcha; 2- de 51 a 100% de murcha; 3- morta. Quanto à varíola, verificou-se que plantas de 'Sekati' (grupo Formosa) apresentaram os menores valores médios finais de severidade da doença na folhagem (2,0) enquanto que, 'Golden' (3,1) e'NT Red' (3,7) apresentaram os maiores. Nos frutos, 'Tailândia Roxão' (1,6), 'Tailândia Verde' (1,7) e 'Sekati' (1,7) apresentaram os menores valores de varíola, enquanto que, 'Tailândia Roxo' (2,3), 'Cross Paris' (2,5), e 'Sunrise Solo' (3,1) apresentaram os maiores. Quanto à podridão do pé, 'Tailândia Roxão' (grupo Formosa) apresentou a menor quantidade de doença, enquanto que, 'Golden', 'Sunrise Solo e 'NT Red' apresentaram os maiores valores.

Papaya (Caryca papaya) genotypes ('NT Red', 'Golden', 'Baixinho de St. Amália', 'Sunrise Solo', 'Cross Paris', 'Tailândia Verde', 'Tailândia Roxo', 'Tailândia Roxão', 'Sekati' and 'Tainung-1') were evaluated for resistance to black-spot (Asperisporium caricae) and foot-rot (Phytophthora palmivora). The study was conducted in an area where both pathogens occurred naturally and in a greenhouse using soil naturally infested with P. palmivora. Black-spot severity was evaluated using a scale, from 1 (0-3% of the surface covered by lesions) to 6 (> of 50% of the surface covered by lesions). The evaluations were made between March / 2003 and April / 2003 and between October / 2003 and February / 2004. Foot-rot was evaluated, on the field trial, by counting the total number of plants with yellowing or wilt symptoms in the same period. On the greenhouse trials P. palmivora severity was evaluated in each plant using a scale from 0 (no wilt symptoms) to 3 (plant death). In relation to black-spot, the genotype 'Sekati' of the Formosa group presented the lowest average value of severity (2,0) on the foliage while ''Golden' (3,1) and NT Red' (3,7) had the largest. 'Tailândia Roxão' (1,6), 'Tailândia Verde' (1,7) and 'Sekati' (1,7) also had the lowest averages of severity on the fruit, while, 'Tailândia Roxo' (2,3), 'Cross Paris' (2,5), and 'Sunrise Solo' (3,1) presented the largest. In relation to foot rot, 'Tailândia Roxão' (Formosa group) presented low amount of disease and 'Golden', 'Sunrise Solo, and 'NT Red' presented higher values.