Exocellular phospholipase C activity from a Propionibacterium acnes strain isolated from a periodontal pocket.

The culture supernatant of a strain of Propionibacterium acnes was investigated for its phospholipase (PL) activity. The microorganism was isolated from a periodontal pocket of a patient with periodontal disease. Supernatants from cultures of this microorganism were used as a source to obtain enzymes. Proteins from the supernatants were concentrated, and their enzymatic activity was partially purified through molecular sieving. The procedure yielded two peaks of activity. This activity was shown to hydrolyze phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) and was effective in a pH range of 5 to 9, with an optimal activity at pH 7.0. Divalent cations were not required for activity of the enzymes. Analysis of the products obtained from the hydrolysis of PC labeled in the choline, phosphoryl, or acyl moieties and PE containing labeled oleic acid indicated that the supernatants' activity was mostly phospholipase C (PL-C). Phospholipase C can act synergistically with other factors to produce tissue damage, and hence may contribute to the pathogenesis of periodontal disease.

Comparative activity of ciprofloxacin against anaerobic bacteria.

The in vitro activity of ciprofloxacin was assessed against 362 strains of anaerobic bacteria and compared with that of cefoxitin, clindamycin, metronidazole, and mezlocillin. Only 31% of the strains tested were susceptible to ciprofloxacin. The other agents were active against most of the strains tested.

Phospholipase A activity in supernatants from cultures of Bacteroides melaninogenicus.

The phospholipase A activity in culture supernatants of two strains of Bacteroides melaninogenicus is described. The enzyme utilize phosphatidylcholine as substrate and produce mainly lysophosphatidylcholine and free fatty acids. The activities are Ca2+-independent, are not affected by the presence of a chelating agent, have a broad pH range (5-9) and an optimum temperature for activity of approx. 50 degrees C. The activity in a growing bacterial culture increases from the end of the lag phase to the late exponential phase of growth. Analysis of the products resulting from the actions of the enzymes on L-alpha-palmitoyl-beta-oleoyl[1-14C]phosphatidylcholine indicates that the enzymes are phospholipase A1 (EC 3.1.1.32).

Susceptibility of some plaque microorganisms to chemotherapeutic agents.

Investigators have used chemotherapeutic agents topically for plaque control without knowing the drug concentration necessary to inhibit the growth of odontopathic microorganisms. S mutans, S sanguis, A viscosus and A naeslundii are important components of the plaque flora. The minimal inhibitory concentrations (MIC) and minimal bactericidal concentrations (MBC) of niddamycin, vancomycin, bacitracin, and kanamycin were determined for each organism in liquid culture. These antibiotics were selected because of their low absorption from the gastrointestinal tract. Niddamycin, vancomycin, and bacitracin had the lowest MIC, from 0.2 to 10 units/ml. Kanamycin was inhibitory only at much higher concentrations (130 to 500 units/ml). The corresponding MBC was generally higher than the MIC. A viscosus was the most resistant organism tested. These data are important in designing controlled release devices for delivering a suitable antibiotic on a continuous basis intraorally.

Deoxyribonucleic acid modification by intermediate-type modification mutants of Escherichia coli K-12 and B.

The modification of bacteriophages grown on r-m+/- restriction and modification mutants of Escherichia coli K-12 or B appears to be related to the number of restriction-specific sites in the viral genome. Bacteriophage fd and its mutant U1 fd, which carry two and one B-specific sites, respectively, are not modified in vivo by rB-mB+/- mutant strains. In vitro treatment of fd RF-B+/- deoxyribonucleic acid (DNA) or U1 fd RF-B+/- DNA by endo R-Eco B results in cleavage of the substrate DNA. Lambda bacteriophage, after growth in r-m+/- mutant host strains (lambda-K+/- or lambda-B+/-), is partially protected from in vivo degradation by wild-type homospecific strains. Its efficiency of plating on these strains is approximately 10(-2). However, a hybrid phi80-lambda phage which carries only one K-specific site (sklambda-1) is not modified by rK-mK+/- strains. Labeled DNAs from lambda-B+/- and lambda-K+/- phages were used as substrates for endo R-Eco B and endo R-Eco K nucleases. Zonal centrifugation analysis of the products of the reactions indicate that rK-mK+/- mutants do not protect lambda DNA from in vitro degradation by endo R-Eco K. In contrast, rB-mB+/- mutants appear to partially protect lambda DNA from attack by endo R-Eco B.