RESUMO
FIZ15 bacteriophage, from a human clinical isolate of Pseudomonas aeruginosa, causes lysogenic conversion in the P. aeruginosa strain PAO1. The prophage-conferred phenotypes are: (1) increased resistance to phagocytosis by mouse peritoneal macrophages; (2) increased resistance to killing by normal human serum, and (3) increased adhesion to human buccal epithelial cells. These phenotypes are related to the prophage-induced change at the level of its own bacterial receptor, which appears to be the O-antigen.
Assuntos
Fagos de Pseudomonas/patogenicidade , Pseudomonas aeruginosa/virologia , Animais , Aderência Bacteriana/fisiologia , Humanos , Camundongos , Fagocitose , Fenótipo , Pseudomonas aeruginosa/patogenicidade , Coelhos , VirulênciaRESUMO
Bacteria were isolated from soil samples, containing high exchangeable lead concentrations, obtained from a busy freeway in the México City metropolitan area. Forty-five selected strains (86.7% Gram-positive) had a single MIC distribution pattern for lead (800-1600 micrograms/ml lead nitrate) and were considered lead-resistant. The isolates showed variable levels of resistance to arsenate (86.7%), chromate (66.7%), cadmium (57.6%), and mercury (31.1%) ions. Multiple inorganic-ion resistance was shown by all strains.
Assuntos
Bactérias/efeitos dos fármacos , Chumbo/farmacologia , Microbiologia do Solo , Poluentes do Solo/farmacologia , Arseniatos/farmacologia , Cádmio/farmacologia , Cloreto de Cádmio , Cloretos/farmacologia , Cromatos/farmacologia , Resistência Microbiana a Medicamentos , Íons , Chumbo/análise , Cloreto de Mercúrio/farmacologia , México , Testes de Sensibilidade Microbiana , Compostos de Potássio/farmacologia , Solo/análise , Poluentes do Solo/análise , Emissões de VeículosRESUMO
Escherichia coli C600 and C600(lambda) strains were tested for their susceptibility to the bactericidal action of 4% normal human serum. C600 survival was reduced to 30%, 23% and 16% after 60, 150 and 180 min of exposure to serum, respectively, whereas the percentage of survival of C600(lambda) was 199, 109 and 65% at the same times. The estimated exposition times for 50% killing showed an eight-fold difference, they were 23 and 202 min for C600 and C600(lambda), respectively. None of the two strains tested was killed when incubated with serum whose alternative complement pathway was inactivated by heating at 50 degrees C for 20 min, showing that this pathway, and not the classical one, was responsible of the bactericidal action, a conclusion further supported by the finding that both strains were differentially killed by the alternative complement pathway, C600 showing a 14X, 10X and 4X greater susceptibility than C600(lambda) at 60, 120 and 180 min of exposure to serum whose classical pathway was selectively inhibited by chelation with 10 mM EGTA plus 2 mM MgCl2. We feel that lambda phage may lower the serum sensitivity of its lysogen by altering the bacterial external surface, perhaps by the inclusion of some protein encoded by an accessory gene of the lambda genome, and thus interfering with either the formation, deposition or activity of the membrane attack complex.
