The development of multiple antibiotic resistance is a global problem. It is necessary to find new tools whose mechanisms of action differ from those of currently used antibiotics. It is known that fatty acids and cationic polypeptides are able to fight bacteria. Here, we describe the synthesis of fatty acids linked to a polypeptide with antibacterial activity. The linkage of fatty acids to a polypeptide is reported to increase the antibacterial effect of the linked fatty acid in comparison with free fatty acids (FA) or free poly-L-lysine (PLL) or a mixture of both (FA free + PLL free). A number of C6–C18 fatty acids were linked to PLL to obtain new synthetic products. These compounds were assessed in vitro to evaluate their antibacterial activity. Some fatty acid-PLLs showed a good ability to fight bacteria. Their bactericidal activity was evaluated, and, lauryl linked to PLL was found to be the most active product against both Gram-positive and Gram-negative bacteria. This new active component showed a good degree of specificity and reproducibility and its minimum inhibitory concentration (MIC) was comparatively good. The antibacterial activity of the lauryl-PLL compound suggests that it is a new and promising antimicrobial agent.

This work aims at studying the optimization of an on-line capillary electrophoresis (CE)-based tryptic digestion methodology for the analysis of therapeutic polypeptides (PP). With this methodology, a mixture of surrogate peptide fragments and amino acid were produced on-line by trypsin cleavage (enzymatic digestion) and subsequently analyzed using the same capillary. The resulting automation of all steps such as injection, mixing, incubation, separation and detection minimizes the possible errors and saves experimental time. In this paper, we first study the differents parameters influencing PP cleavage inside the capillary (plug length, reactant concentration, incubation time, diffusion and electrophoretic plugs mixing). In a second part, the optimization of the electrophoretic separation conditions of generated hydrolysis products (nature, pH and ionic strength (I) of the background electrolyte (BGE)) is described. Using the optimized conditions, excellent repeatability was obtained in terms of separation (migration times) and proteolysis (number of products from enzymatic hydrolysis and corresponding amounts) demonstrating the robustness of the proposed methodology.

The genetic nature of penicillin (Pc) and tetracycline (Tc) resistance plasmids in Staphylococcus epidermidis were studied and compared with those in S. aureus. Of 10 S. epidermidis strains transduced for penicillin resistance, we could isolate Pc plasmids from only 3. One of these plasmids also encoded for cadmium resistance and another encoded for resistance to ethidium bromide, traits also associated with S. aureus Pc plasmids. Endonuclease fingerprinting of the Pc plasmids from the two species revealed extensive heterogeneity. Two S. epidermidis strains were also transduced for tetracycline resistance. Both harbored plasmids indistinguishable from S. aureus Tc plasmids as judged by endonuclease fingerprinting. These data suggest that genetic exchange between S. aureus and S. epidermidis occurs in vivo.Although the penicillin (Pc) and tetracycline (Tc) resistance plasmids of Staphylococcus aureus have been well characterized (8), little is known about these resistance determinants in S. epiderinidis. Only recently has a Pc' plasmid been identified in S. epidermidis (18). Before this time, the only evidence for S. epidermidis pcr plasmids was cotransduction or loss of penicillin resistance with other traits (14,19,21,22). The Tcr plasmids of S. epidermiidis have been studied in greater detail and are the same size as those of S. aureus (12,20). Recently the Tcr plasmids of S. epidermidis and S. aureus were compared by deoxyribonucleic acid (DNA) homology and restriction enzyme analysis and appeared to be similar but not identical (5).Antibiotic resistances in S. epidermidis are clinically important for two reasons: (i) S. epidermidis has been increasingly implicated as an opportunistic pathogen (9,10,25), and the spread of antibiotic resistance markers within this species could seriously complicate chemotherapy; and (ii) if staphylococci exchange plasmids in vivo, antibiotic resistances harbored by S. epidermidis may spread to coresident S. aureus strains. The importance of this interspecific exchange is evident when one considers that more strains of S. epidermidis are antibiotic resistant than are strains of S. aureus isolated under comparable conditions (1, 10).To determine whether S. epidermidis and S. aureus strains exchange plasmid DNA in vivo, we characterized the Tcr and pcr plasmids of

Two strains of Staphylococcus aureus, Smith and M, were studied for the elimination of encapsulation. For S. aureus M, encapsulation was stable. For S. aureus Smith, spontaneous loss of encapsulation was 1.3% and increased markedly in medium containing surface-active agents. In the presence of sodium dodecyl sulfate, unencapsulated cells had a considerable selective advantage. Attempts to demonstrate covalently closed circular plasmid deoxyribonucleic acid were unsuccessful. In cultures of unencapsulated cells, encapsulated cells were observed occasionally. These data argue against a plasmid location for the determinants controlling encapsulation in this organism in spite of a high spontaneous loss of this character.

THE PRODUCTION of coagulase is universally accepted as the most distinctive characteristic of Staphylococcus aureus. Furthermore, among the numerous extracellular proteins commonly associated with staphylococcal virulence, coagulase seems to be the most stably associated. Recently we have developed a technique whereby it is readily possible to detect one colony that produces coagulase among 30 OOO coagulase-negative colonies by means of a pour-plate technique (parisi, Baldwin and Sottile, 1973). Coagulase-producing colonies in the agar can be detected by the dense zone of precipitated fibrin around them. This technique makes feasible certain types of genetic studies on production and regulation of coagulase, as well as studies of other aspects of its possible role in staphylococcal disease. MATERIALS AND METHODSBacteriaf strains. A coagulase-negative mutant was obtained from strain 1-746 after exposure of the culture to 100 pg of N-methyl-N-nitro-N-nitrosoguanidine (Aldrich Chemical Co. Inc., Milwaukee, Wis.) per ml of 0 . 1~ phosphate buffer, pH 7.0. Transduction experiments were done with the coagulase-negative mutant of strain 1-746 and with a lysogenic variant of this mutant strain. Both parent and mutant, before lysogenisation, were susceptible to lysis by phages 80 and 81 of the International Basic Set of staphylococcal phages. Upon lysogenisation, the coagulase-negative mutant was untypable. The S. aweus strains listed in the table were used in the curing experiments. All cultures were maintained on Difco Brain Heart Infusion @HI) agar at 4°C.Lysogenisation of strain I-746. Lysogenisation of a coagulase-negative mutant of S.aureus strain 1-746 with phage 80 was carried out by the method of Blair and Carr (1961). Lysogenisation was confirmed by immunity to phage 80, a change in the phage typing pattern, and the release of a phage which lysed the propagating strain for phage 80 (PS 80) when the lysogenised culture was induced with mitomycin C (Sigma Chemical Co., St Louis, Mo.) according to the method of Yu and Baldwin (1971). Bacteriophage and transductions. Phage 80 was propagated, titrated, and maintained as described by Kasatiya and Baldwin (1967), except that 0 . 1~ phosphate buffer, pH 7.0, was used for harvesting the phage. For transduction, two 18-h BHI-agar-slant cultures of the coagulase-negative or lysogenic coagulase-negative mutant of S. aureus strain 1-746 were suspended in each of 2 ml of Trypticase Soy Broth (BBL) containing Difco Yeast Extract 0-3 % (w/v) (YETS) to which calcium chloride had been added at a concentration of 400 pg per ml. The h a l cell concentration was 1010 to 2 x 1010 c.f.u. per ml. One ml of suspension was mixed in a centrifuge tube with 1 ml of phage-80 suspension that had been exposed for 60 s. to ultraviolet (UV) irradiation from a General Electric 25-W germicidal lamp at a distance of 46 cm. This suspension which contained 2 x 109 plaque-forming units gave a multiplicity of infection of about 0.1, Control tubes contained 1 ml of bacterial suspension and 1 ml of Y...