The complete nucleotide sequence of the Staphylococcus aureus transposon Tn554, which encodes resistance to erythromycin and spectinomycin, was determined by the dideoxy chain termination method. The transposon was found to be 6691 bp in length and to contain six open reading frames of greater than 125 amino acids. Small insertion and deletion mutations were obtained in each of these by in vitro mutagenesis at restriction endonuclease cleavage sites and the mutants characterized with respect to transposition functions and antibiotic resistance markers. Three of the reading frames, designated tnpA, tnpB and tnpC, encode functions that are required for transposition of Tn554; genetic analysis indicated that these three genes define distinct complementation groups of transposition‐defective mutants. Two of the open reading frames correspond to the resistance determinants spc and ermA, the sixth, designated ORF, has no known function. Tn554‐specific peptides corresponding to tnpA, and spc were identified in a coupled transcription‐translation system in vitro.

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Lysostaphin is an antimicrobial agent belonging to a major class of antimicrobial peptides and proteins known as the bacteriocins. Bacteriocins are bacterial antimicrobial peptides which generally exhibit bactericidal activity against other bacteria. Bacteriocin production is a self-protection mechanism that helps the microorganisms to survive in their natural habitats. Bacteriocins are currently distributed into three main classes. Staphylococcins are bacteriocins produced by staphylococci, which are Gram-positive bacteria of medical and veterinary importance. Lysostaphin is the only class III staphylococcin described so far. It exhibits a high degree of antistaphylococcal bacteriolytic activity, being inactive against bacteria of all other genera. Infections caused by staphylococci continue to be a problem worldwide not only in healthcare environments but also in the community, requiring effective measures for controlling their spread. Since lysostaphin kills human and animal staphylococcal pathogens, it has potential biotechnological applications in the treatment of staphylococcal infections. In vitro and in vivo studies performed with lysostaphin have shown that this staphylococcin has potential to be used, solely or in combination with other antibacterial agents, to prevent or treat bacterial staphylococcal infectious diseases.

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We investigated the mode of action of aureocin A53 on living bacterial cells and model membranes. Aureocin A53 acted bactericidally against Staphylococcus simulans 22, with >90% of the cells killed within a few minutes. Cell death was followed by lysis, as indicated by a clearing of the cell suspension and Gram staining. Aureocin A53 rapidly dissipated the membrane potential and simultaneously stopped biosynthesis of DNA, polysaccharides, and protein. Aureocin A53 induced a rapid release of preaccumulated glutamate and Rb ؉ . Experiments on model membranes demonstrated that aureocin A53 provoked significant leakage of carboxyfluorescein (CF) exclusively from acidic liposomes but only at relatively high concentrations (0.5 to 8 mol%). Thus, the bactericidal activity of aureocin A53 derives from membrane permeation via generalized membrane destruction rather than by formation of discrete pores within membranes. Tryptophan emission fluorescence spectroscopy demonstrated interaction of aureocin A53 with both acidic and neutral membranes, as indicated by similar blue shifts. Since there was no significant aureocin A53-induced CF leakage from neutral liposomes, its appears that the peptide does interact with neutral lipids without provoking membrane damage.During the past decade, a plethora of antimicrobial cationic peptides have been isolated from a range of organisms, including animals, plants, insects, and bacteria (13). The bacteriocins constitute a large family of antimicrobial agents that vary greatly in size and primary sequence but tend to be small cationic peptides of 20 to 60 amino acids with amphipathic characteristics and high isoelectric points (11,16,28). Class I bacteriocins are modified peptides, lantibiotics, which contain lanthionine residues forming intramolecular rings. The peptides generally have a broad spectrum of activity and form unstable pores. Docking molecules may enhance the conductivity and stability of lantibiotic pores (5, 6, 31). Class II bacteriocins are small heat-stable peptides, most with a narrow spectrum of activity, and act primarily by membrane permeabilization of susceptible microorganisms (11); again, specific targets may be involved in the activity, such as the mannosespecific PTS protein in the pediocin family of bacteriocins (8, 9, 23).We have recently described a new nonlantibiotic bacteriocin isolated from Staphylococcus aureus, aureocin A53 (21), which shares some physicochemical characteristics with class II bacteriocins. Aureocin A53 is a tryptophan-rich 51-residue peptide and has a net charge of 8ϩ and an amphiphilic nature. Unlike most class II bacteriocins, aureocin A53 is synthesized without a leader peptide and retains a formylated N terminus. Consequently, genes for biosynthetic enzymes, immunity functions, or regulation of biosynthesis are not found in the vicinity of the aureocin A53 structural gene. Remarkably, an ordered structure in aqueous solution consisting of 36% Ϯ 5% helical and 18% Ϯ 4% ␤-sheet conformation was observed by circulardichroism spectrosco...

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This study analyzed ten strains of coagulase-negative staphylococci (CNS) involved in nosocomial infections in three Brazilian hospitals. Their antibiotic susceptibility profile showed that most strains exhibited multiple antibiotic resistance and possessed the mecA gene. The ability of these strains to adhere to polystyrene microtiter plates was also tested and nine of them proved to be biofilm producers at least in one of the three conditions tested: growth in TSB, in TSB supplemented with NaCl, or in TSB supplemented with glucose. The presence of the bap gene, which codes for the biofilm-associated protein (Bap), was investigated in all ten strains by PCR. AU strains were bop-positive and DNA sequencing experiments confirmed that the fragments amplified were indeed part of a bap gene. The presence of the icaA gene, one of the genes involved in polysaccharide intercellular adhesin (PIA) formation, was also detected by PCR in eight of the ten strains tested. The two icaA-negative strains were either weak biofilm producer or no biofilm producer, although they were bop-positive. To our knowledge, this is the first report demonstrating the presence of the bap gene in nosocomial isolates of CNS, being also the first report on the presence of this gene in Staphylococcus haemolyticus and S. cohnii.