Antibacterial effects of chemomechanical instrumentation and calcium hydroxide in primary teeth with pulp necrosis

PURPOSE

This study's purposes were to: evaluate the antibacterial effect of chemomechanical instrumentation and a calcium hydroxide-based dressing in primary teeth with pulp necrosis secondary to trauma; and detect the presence of Fusobacterium nucleatum and black-pigmented rods in the canals of these teeth.

METHODS

Microbiological sample collections (MSCs) were obtained: after coronal access to the canals of primary incisors (in 18 teeth; MSC 1); after chemomechanical instrumentation (in 10 teeth; MSC 2); and 72 hours after removal of intracanal medication (in 18 teeth; MSC 3). These samples were sent for microbiological processing. The results were analyzed statistically via chi-square, analysis of variance, and Games-Howell tests (P<.05).

RESULTS

Micro-organisms were isolated in approximately 94%, 10%, and 83% of canals, respectively, in MSCs 1, 2, and 3. There was a statistically significant difference only between MSCs 1 and 2 (P<.03). F nucleatum and black-pigmented rods were detected in approximately 56% and 11% of canals in MSC 1, respectively.

CONCLUSION

Chemomechanical instrumentation and calcium hydroxide-based dressing have an anti-bacterial effect by significantly reducing the number of micro-organisms in the main root canal. They showed a limited efficacy, however, and did not prevent bacterial regrowth after endodontic therapy in primary teeth with pulp necrosis secondary to trauma.

Effects of an antimicrobial additive to toothbrushes on residual periodontal pathogens

OBJECTIVE

Previous studies have reported the link between residual microbial contamination of toothbrushes and periodontal diseases. The goal of this pilot study was to evaluate the effects of an antimicrobial additive (Microban) to toothbrushes on residual retention of periodontal pathogens.

METHODOLOGY

Twenty patients had one side of their mouths brushed with a toothbrush containing the antimicrobial agent (experimental side), and the other side with a toothbrush containing no agent (control). Toothbrushes were air-dried (25 degrees C) for four or 24 hours. Toothbrush heads were vortexed and cultured for Prevotella species (Ps), Porphyromonas gingivalis (Pg), Actinobacillus actinomycetemcomitans (Aa), and non-specific colony-forming units (NS). The plates were incubated and counted. Means and standard deviations were calculated, and data were analyzed using a series of t-tests (paired and unpaired) and Wilcoxon matched-pairs signed-rank test.

RESULTS

No significant inter- or intra-group differences in mean counts were found; however, when four-hour and 24-hour data for Aa, Pg, or NS were combined, experimental counts were lower than controls in 39/50 (78%) of the matched pairs (Wilcoxon signed-rank test p = 0.01).

CONCLUSION

Toothbrushes containing the antimicrobial additive showed lower microbial counts than those without, but between-group means were not statistically significant.

Incidence of beta-lactamase production and antimicrobial susceptibility of anaerobic gram-negative rods isolated from pus specimens of orofacial odontogenic infections

The incidence of beta-lactamase production in anaerobic gram-negative rods isolated from 93 pus specimens of orofacial odontogenic infections and the antimicrobial susceptibility of these isolates against 11 antibiotics were determined. A total of 191 anaerobic gram-negative rods were isolated from the specimens. Beta-lactamase was detected in 35.6% of the black-pigmented Prevotella and 31.9% of the nonpigmented Prevotella. However, no strains among the other species isolated produced beta-lactamase. Ampicillin, cefazolin and cefotaxime showed decreased activity as regards beta-lactamase-positive Prevotella strains, whereas the activity of ampicillin/sulbactam, cefmetazole, and imipenem continued to be effective against such strains. All tested beta-lactam antibiotics were effective against Porphyromonas and Fusobacterium. Erythromycin showed decreased activity against nonpigmented Prevotella and Fusobacterium. Clindamycin, minocycline and metronidazole were powerful antibiotics against which anaerobic gram-negative rods could be tested. The present study showed that beta-lactamase-positive strains were found more frequently in the Prevotella strains than in any of the other species of anaerobic gram-negative rods. The effectiveness of adding sulbactam to ampicillin was demonstrated, as well as the difference in cephalosporin activity against beta-lactamase-positive strains.

Liposome-mediated DNA uptake and transient expression in Thermotoga

We report here the successful application of a PCR-based method to detect genetic transformation of Thermotoga neapolitana and Thermotoga maritima. Plasmid vectors were constructed using pRQ7, an 846-bp plasmid found in Thermotoga species strain RQ7, which replicates by a rolling circle mechanism. The vector pJY1 was constructed by placing a gene encoding a thermostable chloramphenicol acetyltransferase from Stacphylococcus aureus under the control of the tac promoter and joining this with pRQ7 in a pBluescript vector. A second vector, pJY2, was similarly constructed using a gene encoding a kanamycin nucleotidyltransferase previously engineered for thermostability. Genetic transformation of T. neapolitana and T. maritima spheroplasts was achieved using cationic liposomes. The transforming DNA was detected in cells grown in liquid cultures using polymerase chain reaction amplification of the cat or kan genes. T. neapolitana could maintain pJY1 for at least 25 generations in liquid medium containing chloramphenicol. The pJY2 vector conferred kanamycin resistance to T. maritima cells grown in liquid culture. Isolation of stable transformants on solid media after 2-3 days of incubation at 77 degrees C was not possible with either vector, probably because of the instability of both vectors and antibiotics under these conditions. However, this transformation procedure provides, for the first time, a method to introduce DNA into this hyperthermophilic bacterium for potential applications such as targeted gene disruption analyses.

[Bactericidal activity of Trovafloxacin and Moxifloxacin against Gram-negative anaerobic bacilli]

Anaerobes are often involved in human pathology, including oral infections. The therapy of anaerobic infection requires certain antibiotics such as: metronidazole, tetracycline or amoxicillin. But the incidence of resistant strains among anaerobes is continuously increasing and it is necessary to find some new agents effective against these bacteria. The aim of our study was to establish the bactericidal activity of two new quinolones against 14 strains of gram-negative anaerobic bacilli. The MIC of tested strains was first detected and then time-kill kinetics was determined by using Miles and Misra methodology. Ciprofloxacin was used as standard-quinolone. The results show that trovafloxacin and moxifloxacin have good activity against anaerobes, better than that of ciprofloxacin. Bactericidal curves suggest a rapid action of moxifloxacin (within the first 4 hours), but a prolonged cidal activity for trovafloxacin (24 hours). For both agents, the antimicrobial effect is concentration-dependent. As previous studies suggest, the new quinolones have good activity against both aerobic and anaerobic bacteria so they are useful in the treatment of mixed infections (common feature of anaerobic infections).

Epitope mapping of monoclonal antibodies specific for the directly cross-linked mesodiaminopimelic acid peptidoglycan found in the anaerobic beer spoilage bacterium Pectinatus cerevisiiphilus

Nineteen monoclonal antibodies (Mabs) were isolated based on reactivity with disrupted Pectinatus cerevisiiphilus cells. All of the Mabs reacted with cells from which the outer membrane had been stripped by incubation with sodium dodecyl sulphate, suggesting the peptidoglycan (PG) layer was involved in binding. Mab reactivity with purified PG confirmed this. Epitope mapping revealed the Mabs in total recognize four binding sites on the PG. Mabs specific for each of the four sites also bound strongly to disrupted Pectinatus frisingensis, Selenomonas lacticifix, Zymophilus paucivorans, and Zymophilus raffinosivorans cells, but weakly to disrupted Megasphaera cerevisiae cells. No antibody reactivity was seen with disrupted cells of 11 other species of Gram-negative bacteria. These results confirm that a common PG structure is used by several species of anaerobic Gram-negative beer spoilage bacteria. These results also indicate that PG-specific Mabs can be used to rapidly detect a range of anaerobic Gram-negative beer spoilage bacteria, provided the bacterial outer membrane is first removed to allow antibody binding.

Antimicrobial susceptibility testing of Bilophila wadsworthia isolates submitted for routine laboratory examination

MICs of antibiotics against Bilophila wadsworthia isolates were measured by agar and broth microdilution with pyruvic acid and by Etest. The inoculum size influenced greatly agar dilution. Despite discrepancies in MICs depending on the measurement method used, clindamycin consistently showed potent activity. Broth microdilution and Etest appear to be candidates for laboratory susceptibility testing.

Susceptibility of the anaerobic gram-negative non-sporulating rod, Bilophila wadsworthia to beta-lactams, beta-lactamase inhibitors, meropenem, metronidazole, clindamycin and quinolones

The susceptibility of eighty-seven strain of Bilophila wadsworthia to five beta-lactams, two beta-lactamase inhibitors, meropenem, metronidazole, clindamycin and two quinolones was determined. Tests were performed by the modified reference agar dilution technique using triphenyltetrazolium chloride for endpoint reading. The test strains showed a reduced susceptibility to the beta-lactams, penicillin G (MIC90 4 micrograms/ml), ampicillin (MIC90 32 micrograms/ml), piperacillin (MIC90 64 micrograms/ml), cephalothin (MIC90 2 micrograms/ml and cefotaxim (MIC90 4 micrograms/ml). The activity of ampicillin was increased by addition of the beta-lactamase inhibitor, sulbactam (MIC90 2 micrograms/ml), as was the activity of piperacillin by the addition of tazobactam (MIC90 4 micrograms/ml) 90.8% of the strains were found to produce beta-lactamase by the nitrocefin tube method. All strains were shown to be highly susceptible to meropenem, metronidazole and clindamycin (MICs < or = 1 microgram/ml). Sparfloxacin (MIC90 1 microgram/ml) and ciprofloxacin (MIC90 0.5 microgram/ml) were found to be active against most of the strains tested.

Periapical abscesses: causal bacteria and antibiotic sensitivity

The purpose of this study was to investigate the aerobic and anaerobic flora of periapical abscesses and evaluate their susceptibility to various antibiotics. In 52 patients, with a diagnosis of periapical abscesses, pus cultures were taken. Forty-two aerobes and 122 anaerobes were revealed, with 2 or more than 2 anaerobic strains isolated in 36 patients. Infections were purely aerobic in 6%, purely anaerobic in 17% and mixed in 75%, while in 2% of the specimens there was no growth of microorganisms. Among anaerobes, microorganisms from the Bacteroides group (38.5%), Peptostreptococcus spp. (24.6%), Peptococcus spp. (13.9%), and Fusobacterium spp. (4.1%), predominated in all cultures. Among aerobes the most prevalent bacteria were streptococci (47.6%) followed by staphylococci (35.6%) while Enterobacteriaceae were isolated in 4.8% of specimens. Selected susceptibility tests performed on several anaerobic species revealed that nitroimidazole derivatives, chloramphenicol and clindamycin retain their broad spectrum killing activity against anaerobes, followed by cefoxitin and moxalactam. Of the newer quinolones, ofloxacin was the most effective. It is evident that the high isolation rate of anaerobic bacteria should influence empiric therapeutic decisions.