ABSTRACT
Background & objectives: Factor causing the elimination of the classical biotype of Vibrio cholerae O1, and its replacement by the El Tor biotype causing the 7th cholera pandemic are unclear. Possible ability of the El Tor strains to adapt better than the classical strains to undefined environmental forces have been largely implicated for the change. Here we describe an environmental bacteriophage designated JSF9 which might have contributed to the range of factors. Methods: Competition assays were conducted in the infant mice model and in microcosms between representative El Tor and classical biotype strains in the absence or in the presence of JSF9 phage. Results: The JSF9 phage was found to kill classical strains and favour enrichment of El Tor strains, when mixtures containing strains of the two biotypes and JSF9 phage were subjected to alternate passage in infant mice and in samples of environmental water. Spontaneous derivatives of the classical biotype strains, as well as transposon mutants which developed resistance to JSF9 phage were found to be defective in colonization in the infant mouse model. Interpretation & conclusions: These results suggest that in addition to other factors, the inherent ability of El Tor biotype strains to evade predation by JSF9 or similar phages which kill classical biotype strains, might have enhanced the emergence of El Tor strains as the predominant pandemic biotype.
Subject(s)
Animals , Bacteriophages/genetics , Bacteriophages/ultrastructure , Genetic Variation , Humans , Male , Pandemics , Vibrio cholerae O1/geneticsABSTRACT
The antinociceptive, anti-inflammatory and diuretic properties of the extracts of P. barbatum (L.) Hara var. barbata, Polygonaceae, at the doses of 200 and 400 mg/kg body weight, were evaluated in mice/rat models using, respectively, the acetic-acid-induced writhing method, the carrageenan-induced edema test and the Lipschitz method. In the acetic-acid-induced writhing test in mice, all extracts displayed a dose dependent analgesic effect. The most potent analgesic activity was observed with the petroleum ether extract at the dose of 400 mg/kg body weight with an inhibition of writhing response 46.8 percent compared to 62.2 percent for the positive control aminopyrine. Petroleum ether extract at the dose of 400 mg/kg body weight also displayed the highest levels of anti-inflammatory activity after 2 h with the 39.3 percent inhibition of paw edema, and this effect was better than the effect observed by the conventional anti-inflammatory agent phenylbutazone (maximum inhibition of 38.3 percent after 4 h). All extracts increased urine volume in a dose-dependent manner, and the ethyl acetate extract showed a significant level of diuresis comparable to that of the standard diuretic agent furosemide.
As propriedades antinociceptiva, antiinflamatória e diurética dos extratos de P. barbatum (L.) Hara var. barbata, Polygonaceae, nas doses de 200 e 400 mg/kg de peso corpóreo foram avaliadas em modelos utilizando camundongos/ratos, respectivamente, o método de contorções induzidas por ácido acético, o teste de edema induzido por carragenina e o método de Lipschitz. No método de contorções induzidas por ácido acetic, todos os extratos apresentaram efeito nociceptivo dose dependente. O efeito nociceptivo mais potente foi observado com o extrato de éter de petróleo na dose de 400 mg/kg com uma inibição das contorções de 46,8 por cento comparado com o controle positivo de aminopirina de 62,2 por cento. O extrato de éter de petróleo na dose de 400 mg/kg também mostrou maior atividade antiinflammatoria após 2 h com 39,3 por cento de inibição do edema de pata, e este efeito foi maior que o observado para o agente antiinflamatório convencional fenilbutazona (inibição máxima de 38,4 por cento após 4 h). Todos os extratos aumentaram o volume de urina de maneira dose dependente e o extrato acetato de etila mostrou um nível de significância de diurese comparável ao agente diurético padrão, furosemida.