Slow release of tetracycline hydrochloride from a cellulose membrane used in guided tissue regeneration.

The objective of this study was to evaluate if the biologic membrane utilized for GTR can be impregnated by tetracycline hydrochloride and if the chemotherapeutic agent, once impregnated, can be released in minimal inhibitory concentrations for a period compatible with clinical application. Initially, an in vitro study was done with cellulose membranes cut in pieces measuring 9 cm2. A volume of 100 microliters containing a 72,000 micrograms/ml solution of tetracycline was dispensed onto each fragment, and dried for 70 minutes at 37 degrees C. Four pieces measuring 0.5 cm2 were cut from different points of the 9 cm2 membrane (presumably, containing 400 micrograms of tetracycline), placed in test tubes containing 4 ml of sterile deionized water, and agitated for 2 minutes. A standard curve was made from known concentrations of tetracycline and compared to 10 microliters of the test solutions obtained by the elution of the 0.5 cm2 fragments. The concentrations were determined through the bioassay technique in 3 duplicate experiments. The samples recovered from the membrane fragments had a mean of 101 micrograms/ml of tetracycline liberated, demonstrating that the membrane was impregnated homogeneously by the chemotherapeutic agent. In a second phase, an in vivo study was carried out to determine the length of time the drug was liberated from the membranes and at which concentrations, in the presence of an inflammatory process. Fourteen 0.5 cm2 fragments containing 400 micrograms of tetracycline were placed in 14 polypropylene chambers containing 200 microliters of thioglycolate medium. The chambers were implanted in the peritoneal cavities of 14 mice, one chamber per animal, and left in from 1 to 14 days. They were then removed and the concentrations of tetracycline determined from 20 microliters samples using a bioassay. The results showed that the antibiotic was released slowly from the 1st through the 12th day in decreasing concentrations that varied from 218 to 20.8 micrograms/ml. The impregnated cellulose membrane can probably be used in GTR acting as a membrane and as a slow-release device, liberating the chemotherapeutic agent in concentrations high enough to eliminate periodontopathic microorganisms.

Susceptibility of streptococci to newer tetracyclines and cephalosporins and to other antimicrobial agents.

Two hundred and thirty-nine strains of Streptococcus including 71 strains of Group A, 81 strains of Group B, 69 strains of enterococci, and 18 strains of S. pneumoniae were tested against 12 antimicrobial agents using an agar dilution method. Cefamandole was the most active cephalosporin tested. Doxycycline and minocycline were more active than tetracycline, although the tetracyclines were considerably less inhibitory than the cephalosporins. Regression line analysis of zones of inhibition versus minimal inhibitory concentration values for tetracycline and minocycline showed the tetracycline disc to be unacceptable for predicting the susceptibility of the Group A Streptococcus to minocycline. Minimal inhibitory concentrations for clindamycin, erythromycin, chloramphenicol, nitrofurantoin, and spectinomycin are also given.

The long-term effect of systemic tetracycline used as an adjunct to non-surgical treatment of advanced periodontitis.

AIM: In the present study both the short- and the long-term effects were evaluated of a treatment that, during the phase of basic therapy, included administration of systemic tetracycline and non-surgical intervention. MATERIAL AND METHODS: 35 adult human subjects with advanced periodontitis, 19 females and 16 males, aged between 24 and 60 years, were included in a test group. 80 age- and sex-matched adult periodontitis subjects were recruited for a control group (42 females and 38 males). A baseline examination included assessment of the following parameters: number of teeth, plaque, bleeding on probing, probing attachment level, probing pocket depth. In radiographs, the distance between the cemento-enamel junction and the alveolar bone crest was determined at all interproximal sites. The subjects were given oral hygiene instruction. The members of the test group were provided with tablets with 250 mg of tetracycline hydrochloride and were instructed to take 1 tablet 4x per day for a period of 3 weeks. No antibiotic was given to the subjects in the control group. During the 3-week interval, all participants received 4-6 sessions of non-surgical periodontal therapy. All subjects were subsequently enrolled in a maintenance care program and were provided with supportive periodontal therapy (SPT) 3-4x per year. Clinical re-examinations were performed after 1, 3, 5 and 13 years. RESULTS: The present investigation demonstrated that tetracycline administered during a 3-week period concomitant with non-surgical treatment enhanced the outcome of mechanical therapy. At the re-examination 1 year after active therapy, there was in the test group an average gain in probing attachment that was almost 3x higher than the gain that occurred in an age and sex matched Control group. Re-examinations after 3, 5, and 13 years of SPT disclosed that this short-term benefit was not maintained in the longer perspective. CONCLUSION: The beneficial effect of systemically administered tetracycline on probing attachment level occurred in the first year post-therapy. Annual rates of probing attachment level change from 1 to 13 years did not differ between groups.

The persistence of R-plasmid-carrying E. coli in a married couple, one of whom was receiving antibiotics.

The aerobic Gram-negative intestinal flora of two individuals, husband and wife, has been followed for about 20 months. The wife was receiving prolonged tetracycline treatment for acne during the first year of the study and was found to carry a large proportion of tetracycline resistant E. coli in her faecal flora even after the tetracycline treatment had ended. A brief therapeutic course of ampicillin during the period when no tetracycline was being taken resulted in the temporary disappearance of the tetracycline resistant flora, but this returned, even though no tetracycline was being taken, as soon as the ampicillin ended. The husband took no antibiotics during the period under study but was frequently found to excrete the same resistant E. coli as his wife. Moreover, the plasmids carried by the tetracycline resistant strains in the wife and the husband were often indistinguishable. This suggests that R-plasmids may spread from people under treatment to close relatives who have not been treated.