Studies on siderophore production of different diarrhoeagenic Escherichia coli.

In the present study, siderophore production capacity of various diarrhoeagenic E coli strains was tested on quantitative basis. The collected strains were classified under enteropathogenic E coli, enterotoxigenic E coli and entero-invasive E coli groups by using appropriate techniques. A few reference . enterotoxigenic E coli strains were also included in this study. The confirmation of various properties of enteropathogenic E coli, enterotoxigenic E coli and entero-invasive E coli strains was carried out by standard procedures. Several non-pathogenic E coli strains were also included in the study to assess their siderophore producing capacity. The results presented in the study showed that, the phenolate type of siderophore, that is enterochelin was predominantly produced by majority of these E coli strains. Only 30% of enteropathogenic E coli and 33% of enterotoxigenic E coli strains failed to produce any detectable level of enterochelin. On the other hand, only 50% of enteropathogenic E coli strains and all the entro-invasive E coli (100%) showed the positive aerobactin that is hydroxamate type of siderophore production ability. None of the enterotoxigenic E coli and non-pathogenic strains produced aerobactin.

Transferable colicinogeny in Salmonella bareilly.

Twenty eight (5.6%) of the 500 isolates of S. bareilly studied were found to be colicin producers. Of these 27 (96.4%) were Col V producers. None of these produced aerobactin and 18 (64.3%) were multidrug resistant. Among 23 (85.2%) strains both drug resistance as well as colicinogeny could be transferred by conjugation. This is the first time that the transferable colicinogeny has been demonstrated in S. bareilly.

Cloned genes of the aerobactin system of virulent avian Escherichia coli do not confer virulence to recombinant strains

1. We cloned the aerobactin region and its receptor from pMV14, a large nonconjugative plasmid isolated from the virulent strain UEL14, to assess the importance of the aerobactin iron uptake system as a virulence determinant in septicemic avian Escherichia coli. 2. The physical map of the region of the recombinant plasmid (pGMV1) containing the genes for synthesis of aerobactin and its receptor was very similar to the corresponding region in pABN1 containing the genetic determinants for the aerobactin system of pColV-K30. 3. The 74-kDa outer-membrane protein encoded by pGMV1 cross-reacted immunologically with the 74-kDa aerobactin receptor protein encoded by pABN1. 4. Various avirulent E. coli strains carrying the recombinant plasmid, which contains only the aerobactin system, were assayed for virulence and were found to be avirulent for chickens. Only the wild-type aerobactin-producing strain was virulent in a pathogenicity test for chickens. 5. These results show that the aerobactin system by itself does not confer virulence, and that other factors are necessary for virulence of avian strains of E. coli

Plasmid coding for aerobactin production and drug resistance is involved in virulence of Escherichia coli avian strains

Strain of avian septicemic E. coli were examined for association among the determinants of drug resistance, the genes for aerobactin production and virulence. In conjugation experiments, a single plasmid (100 Md) from a strain of septicemic E. coli (UEL 29) transferred to E. coli K12 pathogenicity for 1-day old chicks plus resistance to streptomycin and the ability to produce aerobactin and colicin. Additional evidence for the association of R-plasmid and the production of aerobactin, colicin, resistance to sulfadiazine and pathogenicity was obtained by disassociation when all traits were lost simultaneously. These data provide additional evidence for the importance of the aerobactin system for the pathogenicity of avian E. coli

Acidos hidroxâmicos: aspectos químicos e atividade biológica / Hydroxamic acids: chemical aspects and biological activity

Foi feita uma revisäo extensiva da literatura recente relativa aos principais aspectos da química e das propriedades biológicas de ácidos hidroxâmicos. Foram enfatizados os métodos gerais de preparaçäo desses ácidos, porém outros aspectos como reatividade e estrutura também foram discutidos. Relativamente aos aspectos biológicos, foram abordados os seguintes: inibiçäo da enzima urease, propriedades anti-hipertensivas, inibiçäo da síntese do DNA, efeito carcinogênico, açäo contra tripanossomas, inibiçäo de zinco-metaloproteases, atividade fungicida etc