Drinking water is currently a scarce world resource, the preparation of which requires complex treatments that include clarification of suspended particles and disinfection. Seed extracts of Moringa oleifera Lam., a tropical tree, have been proposed as an environment-friendly alternative, due to their traditional use for the clarification of drinking water. However, the precise nature of the active components of the extract and whether they may be produced in recombinant form are unknown. Here we show that recombinant or synthetic forms of a cationic seed polypeptide mediate efficient sedimentation of suspended mineral particles and bacteria. Unexpectedly, the polypeptide was also found to possesses a bactericidal activity capable of disinfecting heavily contaminated water. Furthermore, the polypeptide has been shown to efficiently kill several pathogenic bacteria, including antibiotic-resistant isolates of Staphylococcus, Streptococcus, and Legionella species. Thus, this polypeptide displays the unprecedented feature of combining water purification and disinfectant properties. Identification of an active principle derived from the seed extracts points to a range of potential for drinking water treatment or skin and mucosal disinfection in clinical settings.

RP 59500 is a new injectable streptogramin composed of two synergistic components (quinupristin and dalfopristin) which are active against erythromycin-susceptible and -resistant gram-positive pathogens. The present experiments compared the therapeutic efficacy of RP 59500 with that of vancomycin against experimental endocarditis due to either of two erythromycin-susceptible or two constitutively erythromycin-resistant isolates of methicillin-resistant Staphylococcus aureus. RP 59500 had low MICs for the four test organisms as well as for 24 additional isolates (the MIC at which 90% of the isolates were inhibited was <1 mg/liter) which were mostly inducibly (47%) or constitutively (39%) erythromycin resistant. Aortic endocarditis in rats was produced with catheter-induced vegetations. Three-day therapy was initiated 12 h after infection, and the drugs were delivered via a computerized pump, which permitted the mimicking of the drug kinetics produced in human serum by twice-daily intravenous injections of 7 mg of RP 59500 per kg of body weight or 1 g of vancomycin. Both antibiotics reduced vegetation bacterial titers to below detection levels in ca. 70% of animals infected with the erythromycin-susceptible isolates (P < 0.05 compared with titers in controls). Vancomycin was also effective against the constitutively resistant strains, but RP 59500 failed against these isolates. Further experiments proved that RP 59500 failures were related to the very short life span of dalfopristin in serum (<2 h, compared with >6 h for quinupristin), since successful treatment was restored by artificially prolonging the dalfopristin levels for 6 h. Thus, RP 59500 is a promising alternative to vancomycin against methicillinresistant S. aureus infections, provided that pharmacokinetic parameters are adjusted to afford prolonged levels of both of its constituents in serum. This observation is also relevant to humans, in whom the life span of dalfopristin in serum is also shorter than that of quinupristin.RP 59500 is a new injectable streptogramin composed of a streptogramin B, quinupristin, and a streptogramin A, dalfopristin, combined in a 30:70 ratio. Both compounds bind to the 23S RNA of the 50S ribosomal subunit, and they act synergistically to inhibit protein synthesis and also to kill a number of gram-positive organisms (4, 18). The drug combination is very effective against bacteria which are susceptible to macrolidelincosamide-streptogramin B (MLS) antibiotics. It is also effective against inducibly MLS-resistant strains (1,11,19,21), because quinupristin and dalfopristin are poor inducers of erythromycin resistance methylase (erm) genes, the most frequent MLS resistance determinants in gram-positive pathogens (19). In addition, the synergism of the combination against constitutively MLS-resistant organisms is preserved, in spite of the fact that the streptogramin B (quinupristin) fraction of RP 59500 is inactive against such bacteria. This presumably results from a dalfopristin-induced conformational alteration of the 23S ...

Staphylococcus aureusNewman with an insertion mutation in clfB, the gene encoding clumping factor B, only marginally decreased infection rate (P > 0.05) in rats with experimental endocarditis. In contrast, clfB complementation on a multicopy plasmid significantly increased infectivity (P < 0.05) over the deleted mutants. Although clfB could affect endovascular infection, its importance in experimental endocarditis was limited.Staphylococcus aureus is a major cause of endovascular infections, including both native valve and prosthetic valve endocarditis (13). One reason for this association is its peculiar tropism for damaged endothelia. This is thought to occur via ligand-adhesin interactions between host proteins recovering endovascular injuries and prosthetic materials and staphylococcal surface determinants (7, 8, 10-12, 16, 22, 24).Fibrinogen/fibrin is the most abundant host protein in endothelial lesions (6). It is a 340-kDa hexamer composed of 2␣-, 2␤-, and 2␥-chains (18). Staphylococci express several fibrinogen-binding proteins on their surface (1,3,19,20). Among those, clumping factor A (ClfA) is responsible for typical S. aureus clumping in plasma and was shown to promote both adherence to fibrinogen-coated surfaces in vitro (4, 14, 24) and endocarditis in experimental animal models in vivo (16).Recently, a new clumping factor, ClfB, was described (17). ClfA and ClfB have a similar molecular organization and a great deal of sequence similarity. However, their fibrinogenbinding domain (the A domain) is only 26% identical (17) and interacts with different parts of fibrinogen, i.e., the ␥-chain for ClfA and both the ␣-and ␤-chains for ClfB (15,17). Moreover, the clfA and clfB genes are differentially regulated, clfA being expressed throughout bacterial growth, whereas clfB is expressed only during the early logarithmic phase (14,17). This raises the question of whether ClfA and ClfB might act in synergy to help cells attach more firmly to fibrinogen-coated surfaces during the bacterial growth cycle.In the present experiments, this hypothesis was tested in rats with catheter-induced aortic vegetations. Specifically, we determined the ability of isogenic clfA and clfB single and double mutants, as well as of their clfB-complemented derivatives, to induce valve infection using a previously described experimental design (16). The bacterial strains used and their clumping phenotypes are listed in Table 1. Microorganisms were grown on blood agar plates or in tryptic soy broth (Difco Laboratories, Detroit, Mich.) with aeration at 37°C. For both clumping determination and inoculum preparation, overnight broth cultures of bacteria were diluted 1:100 in fresh medium and grown to the early logarithmic phase, at an optical density at 620 nm of 0.2, corresponding to ca. 10 8 CFU/ml. Mutant strains were grown on antibiotic-supplemented medium containing either 2 g of erythromycin per ml (for strain DU5852), 2 g of tetracycline per ml (for strains DU5943 and DU5944), or 5 g of chloramphenicol per ml (for the clfB-comple...

Quinupristin-dalfopristin (Q-D

Beta-lactams active against methicillin-resistant Staphylococcus aureus (MRSA) must resist penicillinase hydrolysis and bind penicillin-binding protein 2A (PBP 2A). Cefamandole might share these properties. When tested against 2 isogenic pairs of MRSA that produced or did not produce penicillinase, MICs of cefamandole (8-32 mg/L) were not affected by penicillinase, and cefamandole had a > or =40 times greater PBP 2A affinity than did methicillin. In rats, constant serum levels of 100 mg/L cefamandole successfully treated experimental endocarditis due to penicillinase-negative isolates but failed against penicillinase-producing organisms. This suggested that penicillinase produced in infected vegetations might hydrolyze the drug. Indeed, cefamandole was slowly degraded by penicillinase in vitro. Moreover, its efficacy was restored by combination with sulbactam in vivo. Cefamandole also uniformly prevented MRSA endocarditis in prophylaxis experiments, a setting in which bacteria were not yet clustered in the vegetations. Thus, while cefamandole treatment was limited by penicillinase, the drug was still successful for prophylaxis of experimental MRSA endocarditis.

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RP 59500 is a new injectable streptogramin composed of two synergistic components (quinupristin and dalfopristin) which are active against a number of erythromycin-susceptible and -resistant gram-positive bacteria. The following experiments investigate the ability of RP 59500 to prevent experimental endocarditis due to either of two erythromycin-susceptible streptococcal isolates or their constitutively erythromycinresistant Tn916⌬E transconjugants. RP 59500 had low MICs (0.125 to 0.5 mg/liter) for all four test organisms and was substantially bactericidal in vitro. Rats with catheter-induced aortic vegetations were given single-dose antibiotic prophylaxis 30 to 60 min before bacterial inoculation through a computerized pump system which permitted the simulation of drug kinetics for humans produced by either 7 mg of RP 59500 per kg of body weight or 1 g of vancomycin. Single-dose RP 59500 prophylaxis successfully prevented endocarditis due to both the erythromycin-susceptible parent strains and their erythromycin-resistant derivatives in rats challenged with the minimal inoculum infecting 90% of controls. In addition, RP 59500 also prevented infection in animals challenged with fivefold-larger inocula of the erythromycin-susceptible parent strains. Vancomycin successfully prevented endocarditis due to any of the four test organisms. These results underline the in vivo efficacy of RP 59500 against both erythromycin-susceptible and -resistant streptococci. Such good results against the resistant strains would not be expected with erythromycin or clindamycin, which are the standard macrolidelincosamide-streptogramin antibiotics used for endocarditis prophylaxis in humans. An oral form of RP 59500 which might advantageously replace some of the older prophylactic regimens is currently being developed.Most authorities recommend that patients at risk for infective endocarditis take antibiotics prior to medicosurgical procedures that might induce bacteremia. In the case of dental or upper respiratory tract interventions, standard regimens include either oral or parenteral amoxicillin, alone or combined with gentamicin (7,9,(25)(26)(27). For ␤-lactam-allergic patients on the other hand, the use of erythromycin, clindamycin, or vancomycin has been proposed (7,9,25,26). Although widely accepted, all of these drugs present some limitations related either to poor tolerance, limitations of antimicrobial spectrum, or inconvenient route of administration. This is exemplified by (i) the frequent occurrence of ␤-lactam allergy or erythromycin-induced gastrointestinal side effects (26), (ii) the inefficacy of erythromycin and clindamycin against most macrolide-resistant organisms, and (iii) the inconvenience of 60-min intravenous (i.v.) administrations of vancomycin, which is likely to severely alter compliance by outpatients.Some recommendations in Europe also include pristinamycin for ␤-lactam-allergic patients (27). Pristinamycin is a natural mixture of several macrolactones which bind to the 23S RNA of the 50S ribosomal subuni...

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