42EVALUATION OF ULTRASTRUTURAL CHANGES INDUCED BY OFLOXACIN ASSOCIATED WITH CEPHALEXIN AGAINST HUMAN AND BOVINE STRAINS OF STAPHYLOCOCCUS AUREUS DURING POST ANTIBIOTIC EFFECT (PAE)The post-antibiotic effect (PAE) of ofloxacin alone and in association with cephalexin were determined in human strains of Staphyococcus aureus from a hospital and in bovine strains. Ofloxacin produced a persistent post-antibiotic effect (PAE) on all strains tested. The association of ofloxacin - cephalexin in strains of S. aureus generally produced an additive PAE. Ultrastructural changes such as intracellular electron-aggregates, changes in cytoplasmic texture and variations in cytoplasmic volume and cell shape were observed during the PAE using transmission electron microscopy. Cytochemical cell labeling for carbohydrate acids using ruthenium red by transmission electron microscopy showed differences in cytochemical staining between human and bovine strains during the PAE. The ultrastructural changes observed support the suggestion that one possible mechanism of PAE may be related to the persistence of the drug in connection sites, or alternatively of the time that the organism needs to synthesize new proteins and enzymes.galba_takaki@yahoo.com.brResearch412014Staphyococcus aureus,Post-antibiotic effect,Ofloxacin,Association ofloxacin - cephalexin,Ultrastructural changesPereira MSV, Siqueira-Júnior JP,Rodrigues E, Cavalcanti ML,Nascimento AE,Campos-Takaki GMDept of Molecular Biology, Universidade Federal da Paraíba - UFPB, 58051-900 João Pessoa-PB, Brazil.,Dept of Molecular Biology, Universidade Federal da Paraíba - UFPB, 58051-900 João Pessoa-PB, Brazil.,Nucleus of Research in Environmental Sciences and Biotechnology, UNICAP, 50.050-590, Recife-PE, Brazi,Nucleus of Research in Environmental Sciences and Biotechnology, UNICAP, 50.050-590, Recife-PE, Brazi,Nucleus of Research in Environmental Sciences and Biotechnology, UNICAP, 50.050-590, Recife-PE, Brazi,Nucleus of Research in Environmental Sciences and Biotechnology, UNICAP, 50.050-590, Recife-PE, Brazi