No abstract

We report the mobilization by cointegration of the gonococcal 5.2 kb beta-lactamase plasmid pSJ5.2 in an Escherichia coli background. Transfer of pSJ5.2 was measured by filter mating assays with five different conjugative plasmids from Enterobacteriaceae and the gonococcal 41 kb tet(M). Plasmid pSJ5.2 was mobilized to E. coli at frequencies of 1.7x10(-6), 9.3x10(-8) and 2.7x10(-5) by the tet(M), R64 drd-33 and N3 conjugative plasmids, respectively. Mobilization of pSJ5.2 by the 41 kb tet(M) conjugative plasmid resulted in stable Amp(R) E. coli transconjugants consisting of pSJ5.2 plasmid with an insertion located in the 2.4 kb BamHI-BamHI fragment. Mobilization of pSJ5.2 by R64drd-33 and N3 conjugative plasmids involved stable cointegrates as detected by Southern Blot with a DIG-labelled PstI-digested pSJ5.2 probe. Restriction analysis of the R64::pSJ5.2 and N3::pSJ5.2 cointegrates and Southern Blot with the pSJ5.2 probe showed that cointegrates formed by deletion of DNA regions within the 1.8 kb BamHI-HindIII fragment of pSJ5.2. The plasmid thus appears to use multiple recombination mechanisms for cointegration with different conjugative plasmids. The complete nucleotide sequence of pSJ5.2 was determined, and will be a useful tool to further investigate the molecular mechanisms leading to its cointegrative transfer.

Antibacterial activities of methanol and hexane extracts of thirty plants, traditionally used to cure gastrointestinal diseases by six native groups living in Sonora, Mexico, were evaluated against four enteropathogenic bacteria: Salmonella typhimorium (ATCC14028), Shigella flexneri (ATCC 12022), Escherichia coli (ATCC 25922), Escherichia coli (ATCC 35218). The antimicrobial activity was determined using the standard Disk Diffusion Method (DDM) protocol, and assessed by the presence or absence of inhibition zones. Fifteen methanol and four hexane crude extracts had activity against at least one strain. Methanol extracts from Acacia constricta Benth (Mimosaceae), Lysiloma divaricata J.F. MacBride (Fabaceae), Lysiloma watsonii Rose (Fabaceae), and Pithecellobium dulce (Roxb.) Benth (Fabaceae) showed activity against all evaluated enteropathogenic bacteria. The methanol extract of Struthanthus haenkeanus Standley (Loranthaceae) had strong antimicrobial activity against S. flexneri. Only Coursetia glandulosa Gray (gum) (Fabaceae) and Mascagnia macroptera Niedensu (Malpighiaceae) hexane extracts had activity against enterophatogenic bacteria. This is the first evaluation of these medicinal plants against bacterial pathogens that cause gastrointestinal disorders, such as diarrhea and dysentery in the Mexican population.