Bacteriostatic and bactericidal in vitro activities of clarithromycin and erythromycin against periodontopathic Actinobacillus actinomycetemcomitans

A Quantitative Survey of Bacterial Persistence in the Presence of Antibiotics: Towards Antipersister Antimicrobial Discovery

Background: Bacterial persistence to antibiotics relates to the phenotypic ability to survive lethal concentrations of otherwise bactericidal antibiotics. The quantitative nature of the time-kill assay, which is the sector's standard for the study of antibiotic bacterial persistence, is an invaluable asset for global, unbiased, and cross-species analyses. Methods: We compiled the results of antibiotic persistence from antibiotic-sensitive bacteria during planktonic growth. The data were extracted from a sample of 187 publications over the last 50 years. The antibiotics used in this compilation were also compared in terms of structural similarity to fluorescent molecules known to accumulate in Escherichia coli. Results: We reviewed in detail data from 54 antibiotics and 36 bacterial species. Persistence varies widely as a function of the type of antibiotic (membrane-active antibiotics admit the fewest), the nature of the growth phase and medium (persistence is less common in exponential phase and rich media), and the Gram staining of the target organism (persistence is more common in Gram positives). Some antibiotics bear strong structural similarity to fluorophores known to be taken up by E. coli, potentially allowing competitive assays. Some antibiotics also, paradoxically, seem to allow more persisters at higher antibiotic concentrations. Conclusions: We consolidated an actionable knowledge base to support a rational development of antipersister antimicrobials. Persistence is seen as a step on the pathway to antimicrobial resistance, and we found no organisms that failed to exhibit it. Novel antibiotics need to have antipersister activity. Discovery strategies should include persister-specific approaches that could find antibiotics that preferably target the membrane structure and permeability of slow-growing cells.

Impact of antibiotics on smell dysfunction

OBJECTIVE

Viral or bacterial respiratory infections can cause long-lasting olfactory dysfunction. Antibiotic therapy is indicated in severe cases; however, it is unclear whether antibiotic use produces a positive, negative, or null effect on olfactory function. This retrospective study sought to determine whether antibiotic use has an influence on odor identification and detection threshold test scores of patients with smell dysfunction secondary to upper respiratory infections (URIs), lower respiratory infections (LRIs), or rhinosinusitis.

METHODS

Data from a total of 288 patients presenting to the University of Pennsylvania Smell and Taste Center were evaluated.

RESULTS

Patients with a URI etiology who had taken bactericidal antibiotics had lower detection thresholds than did patients who had not taken antibiotics (P < 0.023; analysis of covariance with age and time since infection onset as covariates). Moreover, thresholds were lower for bactericidal antibiotic users than for bacteriostatic antibiotic users with either URI (P = 0.023) or rhinosinusitis (P = 0.028) etiologies. No meaningful influences of antibiotics on the odor identification test scores were evident.

CONCLUSIONS

These findings, which need to be confirmed in prospective double-blind studies, suggest that bactericidal antibiotic therapy may be beneficial in mitigating, at least to some degree, chronic decrements in smell sensitivity due to URIs and rhinosinusitis.

Evaluating the effectiveness of clarithromycin as an adjunct to scaling and root planing: A randomized clinical trial

Background

Administration of systemic antibiotics may implement persuasive treatment effect for chronic periodontitis by intending tissue-invasive bacteria in addition to accustomed nonsurgical periodontal therapy (NSPT).

Aims

The aim of this study was to assess the ancillary effects of oral clarithromycin (CLM) along with NSPT for chronic periodontitis.

Materials and Methods

Thirty periodontitis patients were randomly divided into two equal groups in this double-blind, randomized, parallel group, and active-controlled trial: test group - scaling and root planning (SRP) plus CLM (500 mg thrice daily for 7 days, orally) was given, and control group - only SRP was done. Clinical analysis, such as gingival index (GI), probing depth (PD), and clinical attachment loss (CAL), were taken at baseline, 3 months, and 6-month intervals for both groups. Subgingival plaque samples were cultured for periodontopathic organisms. Immunological parameter C-reactive protein (CRP) levels were estimated.

Results

SPSS version 14 was used for statistical analysis. The intragroup comparison showed a significant reduction in the mean scores of all the parameters from baseline to 6 months. The intergroup comparison showed a statistically significant reduction of PD from baseline to 3 months (P < 0.001). GI, CAL, and CRP levels were also reduced but not statistically significant. The mean colony-forming units (CFU) of Aggregatibacter actinomycetemcomitans (Aa) and Porphyromonas gingivalis (Pg) showed a statistically significant reduction from baseline to 3 months only in the test group (P = 0.042) and (P = 0.046), respectively. There was no statistically significant reduction of Aa and Pg at 6 months.

Conclusions

CLM conceivably accepted as an addendum to NSPT for a shorter period.

Clarithromycin as an Adjunct to One-Stage Full-Mouth Ultrasonic Periodontal Debridement in Generalized Aggressive Periodontitis: A Randomized Controlled Clinical Trial

BACKGROUND

The aim of the present study is to evaluate the periodontal clinical and microbiologic responses and possible adverse effects of clarithromycin (CLM) combined with periodontal mechanical therapy in the treatment of patients with generalized aggressive periodontitis.

METHODS

Forty patients were selected and randomly assigned into one of two groups: 1) CLM (n = 20): one-stage full-mouth ultrasonic debridement (FMUD) associated with CLM (500 mg, every 12 hours for 3 days); and 2) placebo (n = 20): FMUD associated with placebo pills. Clinical and microbiologic parameters were evaluated at baseline and 3 and 6 months postoperatively.

RESULTS

Both treatments presented statistically significant clinical and microbiologic improvements. However, the CLM group presented lower means of probing depth for pockets ≥7 mm at 6 months (4.0 ± 1.7 mm) compared with the placebo group (4.7 ± 1.3 mm) (P = 0.04). In addition, the CLM group also presented greater reduction of Porphyromonas gingivalis (Pg) DNA counts at 6 months (P = 0.0001).

CONCLUSION

Results from this study suggest both treatments are effective; however, adjunct use of CLM to FMUD leads to better reduction of deep pockets and Pg at 6 months compared with FMUD alone.

Azithromycin enhances phagocytic killing of Aggregatibacter actinomycetemcomitans Y4 by human neutrophils

BACKGROUND

Aggregatibacter actinomycetemcomitans resists killing by neutrophils and is inhibited by azithromycin (AZM) and amoxicillin (AMX). AZM actively concentrates inside host cells, whereas AMX enters by diffusion. The present study is conducted to determine whether AZM is more effective than AMX at enhancing phagocytic killing of A. actinomycetemcomitans by neutrophils.

METHODS

Killing assays were conducted in the presence of either 2 μg/mL AZM or 16 μg/mL AMX (equipotent against A. actinomycetemcomitans). Neutrophils were loaded by incubation with the appropriate antibiotic. Opsonized A. actinomycetemcomitans strain Y4 was incubated with the indicated antibiotic alone, with loaded neutrophils and antibiotic, or with control neutrophils (without antibiotic) at multiplicities of infection (MOIs) of 30 and 90 bacteria per neutrophil.

RESULTS

Neutrophil incubation with 2 μg/mL AZM yielded an intracellular concentration of 10 μg/mL. At an MOI of 30, neutrophils loaded with AZM failed to kill significantly more bacteria than control neutrophils during the 60- and 90-minute assay periods. At an MOI of 90, neutrophils loaded with AZM killed significantly more bacteria than either AZM alone or control neutrophils during 60- and 90-minute incubations (P < 0.05), and killed significantly more bacteria after 90 minutes than the sum of the killing produced by AZM alone or neutrophils alone. Neutrophils incubated with AMX under identical conditions also killed significantly more bacteria than either AMX alone or control neutrophils, but there was no evidence of synergism between AMX and neutrophils.

CONCLUSIONS

Neutrophils possess a concentrative transport system for AZM that may enhance killing of A. actinomycetemcomitans. Its effects are most pronounced when neutrophils are greatly outnumbered by bacteria.

Periodontal tissue and serum concentration of clarithromycin after systemic administration in patients affected by chronic periodontitis

BACKGROUND

During the past two decades, dentists and microbiologists have relied on periodontal antibiotic therapy in the management of periodontitis. This association has accumulated and strengthened exponentially. Macrolides attain high therapeutic concentrations in infected tissue, so they are potentially a good choice for inhibiting invasive periodontal pathogens. Clarithromycin accumulates in phagocytes, monocytes, fibroblasts, polymorphonuclear cells, macrophages, and lymphocytes. These cells are more numerous at inflamed sites, so it is reasonable to expect clarithromycin levels to be higher in periodontally diseased sites. This study determines the distribution profile of clarithromycin in the gingiva of patients with periodontitis compared to serum after systemic administration of clarithromycin.

METHODS

Twenty patients (14 males and six females, aged 25 to 45 years) with chronic periodontitis were enrolled in the study. Gingival index and plaque index were recorded at baseline and 3 days after administration of 500 mg clarithromycin, twice daily, for 3 days. Intravenous blood and biopsy of periodontal tissue samples were taken on the third day. These samples were analyzed for detection of clarithromycin concentration using high-performance liquid chromatography.

RESULTS

Approximately 6 hours after the last dose of clarithromycin, mean clarithromycin concentrations in serum and periodontal tissue were 0.465 μg/mL and 2.61 μg/g, respectively, and the difference was statistically significant.

CONCLUSIONS

Clarithromycin can attain higher levels in gingiva than serum of patients with periodontitis. This distribution profile of clarithromycin can thus be advantageous in the management of periodontal lesions.

Evaluation of subgingivally delivered 0.5% clarithromycin as an adjunct to nonsurgical mechanotherapy in the management of chronic periodontitis: a short-term double blinded randomized control trial

OBJECTIVE

As the risk involved with systemic antimicrobials (high doses, microbial resistance, adverse reactions, etc.) restricts their use and local delivery of antimicrobials into periodontal pockets improves periodontal health, this study was designed to investigate the effects of subgingivally delivered clarithromycin (CLM; 0.5%) as an adjunct to nonsurgical mechanotherapy in chronic periodontitis subjects.

METHODS

Ninety-eight patients were categorized into two treatment groups: scaling and root planing (SRP) plus 0.5% CLM (test; group 1) and SRP plus placebo (control; group 2). Clinical parameters included gingival index (GI), sulcus bleeding index (SBI), plaque index (PI), probing depth (PD), and periodontal attachment level (PAL), recorded at 4, 8 and 12 weeks. The concentration of 0.5% CLM in gingival fluid was estimated by reverse-phase high pressure liquid chromatography. anova, the chi-square test and the Scatterthwaite test were used for statistical analysis.

RESULTS

Patients treated with SRP + CLM showed enhanced reductions in GI, SBI, and PD, and gains in PAL (P < 0.001) over time, as compared with the placebo group. However, no statistically significant differences were noted for PI. The mean concentration of CLM was detected in gingival crevicular fluid for up to 7 weeks, fulfilling the conditions for a controlled-release device.

CONCLUSION

Adjunctive use of 0.5% CLM as a controlled drug delivery system enhanced the clinical outcome up to 3 months.

Locally delivered 0.5% clarithromycin, as an adjunct to nonsurgical treatment in chronic periodontitis with well-controlled type 2 diabetes: a randomized controlled clinical trial

OBJECTIVE

Several epidemiologic studies have identified a greater incidence of periodontitis in patients with type 2 diabetes. Recent developments suggest that local delivery of antimicrobials into periodontal pockets improve periodontal health. The present study was designed to investigate the adjunctive effects of subgingivally delivered clarithromycin (CLM) (0.5% concentration) as an adjunct to scaling and root planing for treating chronic periodontitis in patients with well-controlled type 2 diabetes.

METHODS

Sixty-three patients were categorized into two treatment groups: Group 1, scaling and root planing (SRP) plus 0.5% CLM; Group 2, SRP plus placebo gel. Clinical parameters were recorded at baseline, 1, 2, and 3 months; which included gingival index (GI), sulcus bleeding index (SBI), plaque index (PI), probing depth (PD), and periodontal attachment level (PAL).

RESULTS

Both therapies resulted in significant improvements. Using a subject-based analysis, patients in Group 1 treated with SRP + CLM showed enhanced reductions in PI, GI, SBI, and PD, and gains in PAL (P < 0.001) over a period of 6 months as compared to Group 2.

CONCLUSION

Although both treatment strategies seemed to benefit the patients, the adjunctive use of 0.5% CLM as a controlled drug delivery system enhanced the clinical outcome.

Clarithromycin accumulation by phagocytes and its effect on killing of Aggregatibacter actinomycetemcomitans

BACKGROUND

Clarithromycin inhibits several periodontal pathogens and is concentrated inside gingival fibroblasts and epithelial cells by an active transporter. We hypothesized that polymorphonuclear leukocytes (PMNs) and less mature myeloid cells possess a similar transporter for clarithromycin. It is feasible that clarithromycin accumulation inside PMNs could enhance their ability to kill Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans).

METHODS

To test the first hypothesis, purified PMNs and cultured HL-60 cells were incubated with [(3)H]-clarithromycin. Clarithromycin transport was assayed by measuring changes in cell-associated radioactivity over time. The second hypothesis was examined with PMNs loaded by incubation with clarithromycin (5 μg/ml). Opsonized bacteria were incubated at 37°C with control and clarithromycin-loaded PMNs.

RESULTS

Mature human PMNs, HL-60 cells differentiated into granulocytes, and undifferentiated HL-60 cells all took up clarithromycin in a saturable manner. The kinetics of uptake by all yielded linear Lineweaver-Burk plots. HL-60 granulocytes transported clarithromycin with a K(m) of ≈250 μg/ml and a V(max) of 473 ng/min/10(6) cells, which were not significantly different from the values obtained with PMNs. At steady state, clarithromycin levels inside HL-60 granulocytes and PMNs were 28- to 71-fold higher than extracellular levels. Clarithromycin-loaded PMNs killed significantly more A. actinomycetemcomitans and achieved shorter half-times for killing than control PMNs when assayed at a bacteria-to-PMN ratio of 100:1 (P <0.04). At a ratio of 30:1, these differences were not consistently significant.

CONCLUSIONS

PMNs and less mature myeloid cells possess a transporter that takes up and concentrates clarithromycin. This system could help PMNs cope with an overwhelming infection by A. actinomycetemcomitans.

[Antibiotic therapy in odontogenic infections in children and adolescents: pharmacokinetic/pharmacodynamic analysis]

INTRODUCTION

The objective of this study was to evaluate the efficacy of the most commonly used antimicrobial treatments in odontogenic infections in children and adolescents on the basis of pharmacokinetic/ pharmacodynamic (PK/PD) criteria.

METHODS

Unbound drug plasma concentration-time curves were simulated with mean population pharmacokinetic parameters of amoxicillin, co-amoxiclav, cefuroxime axetil, spiramycin, clindamycin, azithromycin, and metronidazole. For drugs showing time-dependent antibacterial killing, the time above MIC90 of the pathogens studied was calculated (T>MIC). For drugs with concentration-dependent bactericidal activity, the area under the concentration-time curve (AUC)/MIC90 ratio was calculated.

RESULTS

Adequate efficacy indexes (T>MIC>40%) against all the microorganisms examined with the exception of Veillonella spp. were obtained with co-amoxiclav (80 mg/kg/day). Clindamycin (40 mg/kg/day) obtained adequate PK/PD indexes except for Lactobacillus, Actinobacillus actinomycetemcomitans, penicillin-resistant Peptostreptococcus, and Eikenella corrodens. High-dose amoxicillin yielded unsatisfactory results against many bacterial species. Azithromycin and metronidazole showed inadequate efficacy indexes against the majority of pathogens studied (AUC/MIC90<25).

CONCLUSION

When antibiotic therapy is needed for odontogenic infections in children and adolescents, the most active empirical therapeutic choice is co-amoxiclav with high doses of amoxicillin. Clindamycin can be used as an alternative option. These results should be confirmed in clinical trials, in which the PK/PD approach could be useful for the design and assessment of results.

Distribution of systemic clarithromycin to gingiva

BACKGROUND

Aggressive and recurrent forms of periodontitis are associated with infections by Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans) and Porphyromonas gingivalis. Because these pathogens invade tissue, they are difficult to eliminate by root planing alone. The use of systemic antibiotics in conjunction with root planing significantly enhances clinical and microbiologic treatment outcomes. Although it is not widely prescribed by periodontists, clarithromycin is potentially useful because it is taken up by host cells and has favorable antimicrobial activity.

METHODS

Experimental gingivitis was induced in eight healthy subjects at one randomly selected maxillary posterior site. The contralateral maxillary site served as the healthy control. Thereafter, subjects were administered six doses of clarithromycin, 500 mg, every 12 hours. Blood was then drawn, and samples of gingiva were harvested from both sites. The samples were extracted, and clarithromycin content was analyzed by liquid chromatography.

RESULTS

Mean clarithromycin concentrations in healthy control and inflamed gingiva (2.4 and 3.0 microg/g, respectively) were significantly higher than in serum (0.5 microg/ml; P <0.05). Clarithromycin levels at control and gingivitis sites were higher than serum by 5.7- and 7.0-fold, respectively (difference between sites was significant; P = 0.02). At control sites, a significant decrease in gingival crevicular fluid flow rate was evident at the conclusion of the clarithromycin regimen (P = 0.018).

CONCLUSIONS

Clarithromycin can attain higher levels in gingiva than serum and reach higher levels in inflamed gingiva than in healthy gingiva. Its distribution profile seems to be suitable for the treatment of periodontitis. The reduction in crevicular fluid flow at control sites suggested that clarithromycin may produce anti-inflammatory effects.

Clarithromycin transport by gingival fibroblasts and epithelial cells

Macrolide antibiotics penetrate cells, but the mechanism by which this occurs is unclear. The objective of this study was to characterize the mechanisms of clarithromycin uptake by gingival fibroblasts and oral epithelium. Cultured human gingival fibroblasts and SCC-25 cells were incubated with [(3)H]-clarithromycin. We assayed clarithromycin transport by measuring cell-associated radioactivity over time. Fibroblasts and epithelial cells rapidly accumulated clarithromycin, attaining steady-state intracellular concentrations within 15 minutes. Incubation in medium containing 2 mug/mL clarithromycin yielded steady-state intracellular concentrations of 75.8 mug/mL in fibroblasts and 6.6 mug/mL in SCC-25 cells. Clarithromycin transport exhibited Michaelis-Menten kinetics and was inhibited below 37 degrees C. The Michaelis constants for fibro-blasts and SCC-25 cells were 78.4 and 227 mug/mL, respectively, while the maximum transport velocities were 264 and 381 ng/min/10(6) cells, respectively. Thus, both types of cells take up clarithromycin via a concentrative active transport system. By increasing intracellular clarithromycin levels, this system may enhance the effectiveness of clarithromycin against invasive periodontal pathogens.

Clarithromycin reduces recurrent cardiovascular events in subjects without periodontitis

Inflammation leading to acute coronary syndrome may be triggered by bacteria causing periodontal infection. We investigated if recurrence of cardiovascular events in unstable coronary patients are associated with periodontitis or microbiological/serological markers of it. Periodontitis-related parameters of 141 patients with acute non-Q-wave infarction or unstable angina pectoris, who participated in a double-blind, placebo-controlled study with clarithromycin for 3 months, were adjusted to the occurrence of a recurrent cardiovascular event during a follow-up period (average 519 days). In the age group under 65 years the patients with periodontitis had a univariate odds ratios (OR) 95% confidence intervals (95% CI) of 5.0 (1.02-24.55) for a recurrent cardiovascular event in comparison with patients without periodontitis. Dental status correlated positively with serum lipopolysaccharide concentrations and combined IgG antibody response to Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis. The end point frequency did not differ between clarithromycin and placebo groups in bacterium-positive, seropositive, or periodontitis patients. Fewer end points in clarithromycin group were seen in bacterium-negative, seronegative, edentulous, and non-periodontitis patients. Periodontitis and edentulousness are associated with recurrent cardiovascular events, especially in younger patients. Long-term clarithromycin therapy seems to be beneficial in prevention of recurrent cardiovascular events in non-periodontitis but not in periodontitis patients.

Quantitative comparison of the cytocidal effect of seven macrolide antibiotics on human periodontal ligament fibroblasts

The cytocidal effect of seven macrolide antibiotics on human periodontal ligament fibroblasts (Pel cells) was studied. Pel cells were exposed for 48 h to erythromycin (EM), clarithromycin (CAM), roxithromycin (RXM), azithromycin (AZM), josamycin (JM), midecamycin (MDM), and rokitamycin (RKM), and allowed to form colonies. The cytocidal effect of the macrolides was measured as a decrease in colony-forming efficiency and was found to increase with the concentration. To obtain a quantitative measure of the cytocidal effect, the LD50, i.e. the concentration that decreases colony-forming efficiency 50% relative to control cells, was extrapolated from the concentration-response curves. The rank of the macrolides according to their cytocidal effect (LD50) was RKM > RXM > CAM > AZM > JM > MDM approximately EM. RKM, RXM, CAM, AZM, and JM were at least 1.7-12.2 times more cytocidal than MDM or EM. When extrapolated from the concentration-response curves, the relative survival of the Pel cells exposed to each of the macrolides at the MIC90 concentrations for periodontopathic bacteria was estimated to be: > or = 53.8% for RKM, > or = 92.7% for RXM, > or = 94.6% for CAM, > or = 97.1% for AZM, and > or = 86.2% for EM. The effect of the antibiotics on the mRNA expression of alkaline phosphatase (ALP) and type I procollagen (COL) was examined in Pel cells exposed for 48 h to RXM, CAM, AZM, and EM, which exhibited strong, moderate, and weak cytocidal activity. The constitutive levels of both ALP and COL mRNA were retained in cells exposed to RXM at < or = 3 microM, CAM at < or = 10 microM, and AZM or EM at < or = 3 microM. The MIC90 against periodontopathic bacteria is < or = 4.8 microM for RXM, 5.3 microM for CAM, 2.7 microM for AZM, and 21.8 microM for EM. These results suggest that topical administration of CAM or AZM to the gingival crevice at their MIC90 concentration for periodontopathic bacteria would have little adverse effect on the growth and differentiation of the periodontal ligament. It is important to note, however, that these findings have yet to be extrapolated to in vivo conditions.

Recent developments in macrolides and ketolides

Emergence of bacterial resistance to macrolide antibiotics, particularly in Gram-positive bacteria, has been observed. Novel macrolides having C-4" carbamate functional groups and ketolides, the 3-keto derivatives of macrolides, have been found to have activities against macrolide-resistant strains. Several potential non-antibacterial activities of macrolides have been reported, such as inhibition of cytokine production, neutrophil attachment to human bronchial epithelial cells and vesicular transport.