Antimicrobial susceptibility of 800 anaerobic isolates from patients with dentoalveolar infection to 13 oral antibiotics

INTRODUCTION: The aim of this study was to determine the current antimicrobial susceptibility of the principle anaerobic pathogens involved in dentoalveolar infection, to 13 oral antibiotics, and to assess the value of each antibiotic in the management of the infection. METHODS: A total of 800 isolates from patients with dentoalveolar infection (Prevotella species, Fusobacterium species, Porphyromonas species and Peptostreptococcus micros) were tested for their susceptibility to amoxicillin, amoxicillin/clavulanate, cefaclor, cefuroxime, cefcapene, cefdinir, erythromycin, azithromycin, telithromycin, minocycline, levofloxacin, clindamycin, and metronidazole using an agar dilution method. RESULTS: Although the majority of Fusobacterium strains were resistant to erythromycin, azithromycin, and telithromycin, the remaining antibiotics demonstrated a high level of antimicrobial activity. P. micros and Porphyromonas species exhibited high susceptibility to all antibiotics tested in this study. In the case of Prevotella species, resistance to amoxicillin occurred in 34% of isolates and all of these resistant strains were found to produce beta-lactamase. Susceptibility of Prevotella strains to cefaclor, cefuroxime, cefcapene, cefdinir, erythromycin, azithromycin, and minocycline was found to correlate with amoxicillin susceptibility. Amoxicillin/clavulanate, telithromycin, clindamycin, and metronidazole exhibited high antimicrobial activity even against amoxicillin-resistant strains of Prevotella species. CONCLUSION: Amoxicillin would still be advocated therefore as being a suitable first-line agent, while reduced susceptibility of Prevotella strains remains a matter of concern with penicillins. Amoxicillin/clavulanate, clindamycin, and metronidazole are useful alternatives in combating the anaerobic bacteria involved in dentoalveolar infection.     

Antimicrobial susceptibility of Enterococcus faecalis isolated from canals of root filled teeth with periapical lesions

AIM: To test, in vitro, the susceptibility to different antibiotics of Enterococcus faecalis isolates from canals of root filled teeth with periapical lesions. METHODOLOGY: Twenty-one E. faecalis isolates, from canals of root filled teeth with persisting periapical lesions, were tested for their antibiotic susceptibilities. The following antibiotics were used: benzylpenicillin, amoxicillin, amoxicillin-clavulanic acid, erythromycin, azithromycin, vancomycin, chloramphenicol, tetracycline, doxycycline, ciprofloxacin and moxifloxacin. Minimal inhibitory concentrations (MICs) for the antimicrobial agents were determined using the E-test System (AB BIODISK, Solna, Sweden), and the E. faecalis strains classified as susceptible or resistant according to the guidelines of National Committee for Clinical Laboratory Standards (NCCLS). The strains were also tested for beta-lactamase production with nitrocefin (Oxoid, Basingstoke, UK). RESULTS: All strains were susceptible to penicillins in vitro, however, the MICs of amoxicillin and amoxicillin-clavulanic acid (MIC(90) = 0.75 microg mL(-1)) were lower than for benzylpenicillin (MIC(90) = 3.0 microg mL(-1)). All strains studied were also susceptible to vancomycin and moxifloxacin, whilst 95.2% were susceptible to chloramphenicol. Amongst the isolates, 85.7% were susceptible to tetracycline and doxycycline and 80.9% to ciprofloxacin. The MIC of erythromycin ranged from 0.38 to >256 microg mL(-1); only 28.5% of the strains were susceptible (MIC < or = 0.5 microg mL(-1)). Limited susceptibility was also observed with azithromycin which was active against only 14.2% of isolates. No strains produced beta-lactamase. CONCLUSION: Enterococcus faecalis isolates were completely susceptible, in vitro, to amoxicillin, amoxicillin-clavulanic acid, vancomycin and moxifloxacin. Most isolates were susceptible to chloramphenicol, tetracycline, doxycycline or ciprofloxacin. Erythromycin and azithromycin were least effective.     

Identification and antimicrobial susceptibility of enterococci isolated from the root canal

Enterococci are occurring in opportunistic infections involving the oral cavity. This study has identified enterococcal species in 29 endodontic infections undergoing treatment with Ca (OH)2 dressings. The in vitro antimicrobial susceptibility of 29 isolated enterococcal strains was determined. Enterococcus faecalis was speciated for 26 isolates and Enterococcus faecium for three isolates. In vitro antimicrobial susceptibility testing revealed enterococcal isolates resistant to benzylpenicillin, ampicillin, clindamycin, metronidazole and tetracycline but sensitive to erythromycin and vancomycin. Due to low sensitivity to antimicrobial agents, enterococci may be selected in root canals undergoing standard endodontic treatment and significantly contribute to endodontic treatment failures.     

Evaluation of the E test for antimicrobial susceptibility testing of Porphyromonas gingivalis

The antimicrobial susceptibilities of 81 recent clinical Porphyromonas gingivalis isolates and two reference strains were determined by the E test, a new method, and were compared with the minimal inhibitory concentrations for these strains obtained by the reference agar dilution method on supplemented Brucella blood agar. The following agreements were obtained: benzylpenicillin 100%, ampicillin 96%, cefaclor 82%, cefuroxime 91%, erythromycin 93%, clindamycin 99%, tetracycline 66%i, doxycycline 89%, metronidazole 77% and ciprofloxacin 77%. Very major discrepancies were observed with ciprofloxacin. This study indicates that the E test is an acceptable method to determine the susceptibility of P. gingivalis for most antimicrobials.     

Identification of Enterococcci isolated from canals of root filled teeth with periapical lesions and their antimicrobial susceptibility to different antibiotics

Aim The objective of the present study was to investigate the occurrence of Enterococcus spp. in root filled teeth with periapical lesions and the in vitro antimicrobial susceptibility of the isolates. Methodology Sixty teeth with failed root canal treatment were included in the study. During nonsurgical endodontic retreatment, the root filling material was removed and the canals were sampled and microbiologically examined. Enterococcus ssp. isolates were tested for their antibiotic susceptibilities using the E‐test system (AB BIODISK, Solna, Sweden). The following antibiotics were used: benzylpenicillin, amoxicillin, amoxicillin‐clavulanic acid, erythromycin, azithromycin, vancomycin, chloramphenicol, tetracycline, doxycycline, ciprofloxacin and moxifloxacin. The strains were also tested for β‐lactamase production with nitrocefin (Oxoid, Hampshire, England). Results Microorganisms were recovered from 51 of 60 teeth. Enterococcus faecalis was recovered from 27 of the 51 canals with bacteria, 18 times in pure culture. All strains were susceptible to penicillins; however, the MICs of amoxicillin and amoxicillin‐clavulanic acid (MIC₉₀ = 0.75 µg mL^?1) were lower than that for benzylpenicillin (MIC₉₀ = 3.0 µg mL^?1). All strains studied were also susceptible to vancomycin and moxifloxacin, while 95.2% were susceptible to chloramphenicol. Among the isolates, 85.7% were susceptible to tetracycline and doxycycline, and 80.9% to ciprofloxacin. The MIC of erythromycin ranged from 0.38 to >256 µg mL^?1; only 28.5% of the strains were susceptible (MIC ≤ 0.5 µg mL^?1). Limited susceptibility was also observed with azithromycin, which was active against only 14.2% of isolates. No strains produced β‐lactamase. Conclusions Enterococcus faecalis was present in a large number of canals in teeth with failed root fillings and were completely susceptible, in vitro, to amoxicillin, amoxicillin‐clavulanic acid, vancomycin and moxifloxacin. Most isolates were susceptible to chloramphenicol, tetracycline, doxycycline or ciprofloxacin. Erythromycin and azithromycin were least effective. (Supported by the Brazilian agencies FAPESP 00/13686‐8, 00/13689‐7; CNPq 520277/99‐6 and CAPES BEX2449/02‐1).     

Microbiological analysis of infected root canals from symptomatic and asymptomatic teeth with periapical periodontitis and the antimicrobial susceptibility of some isolated anaerobic bacteria

The purpose of the present study was to investigate the correlation between the composition of the bacterial flora isolated from infected root canals of teeth with apical periodontitis with the presence of clinical signs and symptoms, and to test the antibiotic susceptibility of five anaerobic bacteria mostly commonly found in the root canals of symptomatic teeth against various substances using the E-test. Microbial samples were taken from 48 root canals, 29 symptomatic and 19 asymptomatic, using adequate techniques. A total of 218 cultivable isolates were recovered from 48 different microbial species and 19 different genera. Root canals from symptomatic teeth harbored more obligate anaerobes and a bigger number of bacterial species than the asymptomatic teeth. More than 70% of the bacterial isolates were strict anaerobes. Statistical analysis used a Pearson Chi-squared test or a one-sided Fisher's Exact test as appropriate. Suggested relationships were found between specific microorganisms, especially gram-negative anaerobes, and the presence of spontaneous or previous pain, tenderness to percussion, pain on palpation and swelling amoxicillin, amoxicillin + clavulanate and cephaclor were effective against all the strains tested. The lowest susceptibility rate was presented by Prevotella intermedia/nigrescens against Penicillin G. Our results suggested that specific bacteria are associated with endodontic symptoms of infected teeth with periapical periodontitis and the majority of the anaerobic bacterial species tested were susceptible to all antibiotics studied.     

Evaluation of root canal microorganisms isolated from teeth with endodontic failure and their antimicrobial susceptibility

Studies of the microbiota from the canals of teeth with failure of endodontic therapy have revealed that it differs markedly from that of untreated necrotic dental pulps. This study aimed to evaluate the microbiota of 30 root-filled teeth with persisting periapical lesions and to test the antibiotic susceptibility of the most prevalent species. Microbial samples, isolation and speciation were done using advanced microbiologic techniques for anaerobic species. A total of 55 bacterial species were isolated, 80% were gram-positives and 58% facultative anaerobic microorganisms. The bacterial genera most frequently recovered were Enterococcus, Streptococcus, Peptostreptococcus and Actinomyces. Antibiotic sensitivity of Enterococcus faecalis and Peptostreptococcus spp. was accomplished with the E-test system. All species studied were susceptible to benzylpenicillin, amoxicillin, amoxicillin combined with clavulanate. However, 20% of the E.faecalis strains were resistant to erythromycin and 60% to azithromycin. It was concluded that microbial flora in canals after endodontic failure comprised predominantly facultative anaerobes and gram-positive species. E.faecalis was the species most frequently isolated and showed erythromycin and azithromycin resistance among the isolates.     

Prevalence and clonal analysis of Porphyromonas gingivalis in primary endodontic infections

This study investigated the prevalence of Porphyromonas gingivalis in 62 teeth with primary endodontic infections by using a species-specific 16S rRNA gene-based nested polymerase chain reaction assay. P. gingivalis isolates recovered from 2 infected root canals were also analyzed for clonal diversity by using arbitrarily primed PCR. Overall, P. gingivalis was found in 48% of the samples. This species was specifically detected in 36% of canals of teeth with chronic apical periodontitis, in 46% of the cases of acute apical periodontitis, and in 67% of acute apical abscesses. P. gingivalis was significantly more frequent in abscess aspirates than in canals of teeth with chronic apical periodontitis (P < .05). Typing of colonies retrieved from 2 infected canals revealed 2 clones per individual. These findings confirmed that P. gingivalis can be an important endodontic pathogen, mostly associated with acute abscesses, and demonstrated that different clonal types of this species can colonize the root canal in the same individual.     

68例慢性牙周炎患者龈下菌斑致病菌的分布及耐药性分析

目的：了解慢性牙周炎患者龈下菌斑可疑致病菌的分布及抗生素耐药情况,为临床治疗提供参考。方法对口腔门诊诊断为慢性牙周炎患者龈下菌斑中的致病菌进行分离培养,采用琼脂稀释法测定分离菌对甲硝唑、阿莫西林等10种常用抗生素的敏感性。结果从68例慢性牙周炎患者龈下菌斑中共分离到262株可疑致病菌,所有病例均检出有致病菌感染,其中以牙龈卟啉单胞菌和产黑色素普雷沃菌分离率较高,分别检出66.2%和60.3%,其次为伴放线嗜血杆菌（55.9%）、具核梭杆菌（51.5%）和消化链球菌（45.6%）等。药敏结果显示：所测菌株对硝基咪唑类药物敏感性较高,对甲硝唑、替硝唑、奥硝唑的敏感率均在90%以上,对阿莫西林/克拉维酸全部敏感,对阿奇霉素、米诺环素、克林霉素的敏感率在51%~78%之间,但对青霉素、红霉素耐药性高,敏感率仅分别为2.3%和17.9%。结论牙龈卟啉单胞菌、产黑色素普雷沃菌等菌为宁夏青铜峡市小坝地区慢性牙周炎患者龈下菌斑中主要的可疑致病菌,对阿莫西林/克拉维酸和硝基咪唑类药物普遍敏感。     

Antibiotic resistance in the subgingival microflora in patients with adult periodontitis. A comparative survey between Spain and the Netherlands

The widespread use of antibiotics for treatment of bacterial infections has lead to the emergence of resistant human pathogens. Great differences have been documented between European countries in the use of systemic antibiotics. In parallel, significant differences in levels of resistant pathogens have been documented. In order to investigate whether differences in antibiotic use influence the level of antimicrobial resistance of the subgingival microflora, microorganisms from the subgingival plaque of untreated patients with adult periodontitis in The Netherlands (n = 30) and Spain (n = 31) were compared. Blood agar plates containing breakpoint concentrations of penicillin, amoxicillin, amoxicillin and clavulanate, metronidazole, erythromycin, azithromycin, clindamycin and tetracycline were used to determine the proportion of bacteria from the subgingival plaque that was resistant to these antibiotics. In the Spanish patients, statistically significant higher mean levels of resistance were found for penicillin, amoxicillin, metronidazole, clindamycin and tetracycline. The mean number of different bacterial species growing on the selective plates was higher in the Spanish patients, as was the percentage of resistant strains of most periodontal pathogens. A striking difference was observed in the frequency of occurrence of tetracycline-resistant periodontal pathogens. In Spain, 5 patients had > 3 tetracycline resistant periodontal pathogens, whereas this was not observed in any of the Dutch patients. It is concluded that the widespread use of antibiotics in Spain is reflected in the level of resistance of the subgingival microflora of adult patients with periodontitis.     

Antimicrobial resistance in patients with endodontic infections: A systematic scoping review of observational studies

The aim of this study was to assess the prevalence and proportions of antimicrobial-resistant species in patients with endodontic infections. A systematic scoping review of scientific evidence was accomplished involving different databases. Nine investigations were selected including 651 patients. Enterococcus faecalis was resistant to tetracycline (30%–70%), clindamycin (100%), erythromycin (10%–20%), ampicillin (9%) and azithromycin (60%). On the contrary, Prevotella spp., Fusobacterium spp., Peptostreptococcus spp. and Streptococcus spp. were resistant to penicillin, tetracycline, doxycycline, ciprofloxacin, amoxicillin, erythromycin, metronidazole and clindamycin in different proportions. Fusobacterium nucleatum showed high resistance to amoxicillin, amoxicillin plus clavulanate and erythromycin. Prevotella oralis presented a predisposition to augment its resistance to clindamycin over time. Tanerella forsythia exhibited resistance to ciprofloxacin and rifampicin. Lactococcus lactis presented robust resistance to cephalosporins, metronidazole, penicillin, amoxicillin and amoxicillin–clavulanic acid. It was observed high levels of resistance to antimicrobials that have been utilised in the local and systemic treatment of oral cavity infections.     

乳牙感染根管的菌丛分析

目的分析乳牙根尖周炎感染根管菌丛，为进一步防治提供依据。方法用直接酶法对８例乳牙急性根尖周炎、１４例乳牙慢性根尖周炎感染根管菌丛成分进行分析。结果共检出２４０株细菌，厌氧菌２００株，主要分布于消化链球菌、类杆菌、韦永氏菌、真细菌、丙酸杆菌、放线菌和梭杆菌。急性炎症组类杆菌、梭杆菌的检出率明显高于慢性组（Ｐ＜００５），主要差异在牙龈类杆菌和具核梭杆菌；慢性炎症组小韦永氏菌的检出率明显高于急性组（Ｐ＜０．０５）。结论乳牙急、慢性根尖周炎感染根管内是以厌氧菌为优势菌的混合感染。牙龈类杆菌、具核梭杆菌可能与乳牙根尖周炎的急性症状有关。小韦永氏菌在乳牙慢性根尖周炎中的作用不容忽视     

Antibiotic resistance in an in vitro subgingival biofilm model

INTRODUCTION: The purpose of this study was to utilize an in vitro biofilm model of subgingival plaque to investigate resistances in subgingival biofilm communities to antibiotics commonly used as adjuncts to periodontal therapy. METHODS: Biofilms were grown on saliva-coated hydroxyapatite supports in trypticase-soy broth for 4 h-10 days and then exposed for 48 h to either increasing twofold concentrations of tetracycline, amoxicillin, clindamycin, and erythromycin or therapeutically achievable concentrations of tetracycline, doxycycline, minocycline, amoxicillin, metronidazole, amoxicillin/clavulanate, and amoxicillin/metronidazole. RESULTS: Concentrations necessary to inhibit bacterial strains in steady-state biofilms were up to 250 times greater than the concentrations needed to inhibit the same strains grown planktonically. In the presence of therapeutically available antibiotic concentrations, significantly higher proportions of the biofilms remained viable as the biofilms reached steady-state growth. The combinations of amoxicillin/clavulanate and amoxicillin/metronidazole were the most effective in suppressing growth. These combinations were particularly effective against biofilms up to and including 7 days of age and inhibited 90% or more of the bacteria present relative to untreated controls. As the biofilms approached steady state, these combinations were less effective with 50-60% of the bacteria retaining viability. CONCLUSION: Most, but not all, species of subgingival bacteria are considerably more resistant in biofilms than in planktonic cultures. Resistance appeared to be age-related because biofilms demonstrated progressive antibiotic resistance as they matured with maximum resistance coinciding with the steady-state phase of biofilm growth.     

Analysis of the Antimicrobial Susceptibility of Anaerobic Bacteria Isolated from Endodontic Infections in Brazil during a Period of Nine Years

Introduction

The purpose of this study was to analyze the susceptibility of some anaerobic species isolated from a Brazilian population at different periods of time by determining a pattern of development of resistance to frequently prescribed antibiotics in endodontics.

Methods

Root canal samples were collected from infected teeth at different periods of time (2000-2002, 2003-2005, and 2007-2008) and microbiologically identified with conventional culture techniques. The susceptibility of Prevotella intermedia/nigrescens, P. oralis, Fusobacterium nucleatum, and P. micra isolated strains was determined by the minimum inhibitory concentration (MIC) of amoxicillin, amoxicillin + clavulanate, benzylpenicillin, clindamycin, erythromycin, and metronidazole by using the E-test method.

Results

Amoxicillin and amoxicillin + clavulanate were effective against the majority of species at the different periods of study. Overall, there were low statistical differences regarding the microbial susceptibility between the experimental periods. However, an increase in the anaerobic resistance to penicillin G and clindamycin was observed. Resistance to erythromycin was observed in all species, and there were statistically significant differences between 2000-2002 and 2003-2005 periods for F. nucleatum (P < .05) and between 2003-2005 and 2007-2008 periods for P. intermedia/nigrescens and P. oralis (P < .05).

Conclusions

The antimicrobial resistance of anaerobes isolated from primary endodontic infections showed an increase throughout a period of time regarding a specific Brazilian population.     

Antimicrobial resistance of Staphylococcus aureus and oral streptococci strains from high-risk endocarditis patients

This study sought to determine the antimicrobial susceptibility of Staphylcoccus aureus and viridans group streptococci strains collected from the forearm skin and saliva of 30 patients at high risk of endocarditis. Agar susceptibility tests of antibiotics routinely utilized in dentistry were used to verify antimicrobial resistance of bacterial strains. Of the Staphylcoccus aureus strains, 50% were resistant to ampicillin, 53.3% to amoxicillin, 60.0% to penicillin G, 13.3% to amoxicillin/clavulanate, 20.0% to azithromycin, 27.6% to clarithromycin, 23.3% to erythromycin, 3.3% to cefazolin, and 6.7% to clindamycin. Regarding streptococci, 16.7% of the strains were resistant to ampicillin, 16.7% to amoxicillin, 23.3% to azithromycin, 23.3% to clarithromycin, 30.0% to erythromycin, 13.3% to cefazolin, 26.7% to clindamycin, 16.7% to penicillin G, and 3.3% to amoxicillin/clavulanate. Pathogens associated with bacterial endocarditis exhibited elevated resistance rates against the antibiotics used for prophylaxis in dentistry.     

Antimicrobial profiles of periodontal pathogens isolated from periodontitis patients in The Netherlands and Spain

BACKGROUND AND AIM: Antimicrobial resistance of periodontal pathogens towards currently used antibiotics in periodontics has been investigated in a previous study. Microbial resistance in the periodontal microflora was more frequently observed in Spanish patients in comparison with Dutch patients. The aim of the present study was to compare antimicrobial susceptibility profiles of five periodontal bacteria isolated from periodontitis patients in Spain and in The Netherlands. MATERIAL AND METHODS: Subgingival plaque samples from adult patients with periodontitis were collected and cultured on selective and non-selective plates. Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum and Micromonas micros were isolated and used for minimal inhibitory concentration tests using the Epsilometer (E-test) technique. Eight different antibiotics were tested on all bacterial isolates. MIC50 and MIC90 values for each antibiotic and each species were determined and the percentage of resistant strains was calculated. RESULTS: Significantly higher MIC values were noted in Spanish strains of F. nucleatum for penicillin, ciprofloxacin, of P. intermedia for penicillin, amoxicillin and tetracycline, of M. micros for tetracycline, amoxicillin and azithromycin, and of P. gingivalis for tetracycline and ciprofloxacin. Based on breakpoint concentrations, a higher number of resistant strains in Spain were found in F. nucleatum for penicillin, amoxicillin and metronidazole, in Prevotella intermedia for tetracycline and amoxicillin, and in A. actinomycetemcomitans for amoxicillin and azithromycin. Resistance of P. gingivalis strains was not observed for any of the antibiotics tested both in Spain and The Netherlands. CONCLUSIONS: Differences exist in the susceptibility profiles of periodontal pathogens isolated from periodontitis patients in Spain and in The Netherlands. This implicates that antibiotic susceptibility testing is necessary to determine efficacy of antimicrobial agents. Also, clinical studies with antibiotics should take these differences into account. The information from the present study indicates that it may not be possible to develop uniform protocols for usage of antibiotics in the treatment of severe periodontitis in the European Union.     

Antimicrobial susceptibility variation of 50 anaerobic periopathogens in aggressive periodontitis: an interindividual variability study

BACKGROUND/AIMS: The frequent use of antibiotics in developed countries has led to the emergence of widespread bacterial resistance. In this study, the interindividual variability of the antibiotic susceptibility of 50 putative microorganisms in aggressive periodontitis patients has been evaluated by means of VC (variation coefficient). MATERIAL AND METHODS: A total of 60 microbial samples were collected from 20 adult patients diagnosed with aggressive periodontitis (2-4 samples by patient). Bacterial strains of Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, Fusobacterium nucleatum, and Peptostreptococcus micros were isolated according to Slots' rapid identification method. The susceptibilities to 10 antibiotics were studied: penicillin G (PEN), ampicillin (AMP), amoxicillin (AMX), amoxicillin/clavulanate (AMC), tetracycline (TET), doxycycline (DOX), ciprofloxacin (CIP), erythromycin (ERY), spiramycin (SPI) and clindamycin (CLIN), using the Disk Diffusion Susceptibility test (DDS test: Kirby-Bauer's modified method for anaerobic bacteria). The broth microdilution Minimum Inhibitory Concentration test was carried out as a control test. RESULTS: Among the 50 identified bacteria, 15 were P. gingivalis, 12 P. intermedia, 8 T. forsythia, 9 F. nucleatum, and 6 P. micros. The results of the DDS test show that penicillins (especially AMC, AMP, and AMX), cyclines (especially DOX) and CLIN are highly effective against the 50 anaerobic studied bacteria. CIP and ERY have the lowest efficacy against those bacteria. CIP shows a very variable activity according to anaerobic bacteria species, being particularly inactive against P. gingivalis and very efficient against T. forsythia and P. micros. SPI is also highly efficient but not against P. micros. CONCLUSIONS: The interindividual susceptibility of principal periodontal pathogens to antibiotics is not homogeneous and seems to vary according to bacterial species and antimicrobial molecules. This variability seems to be greater with older molecules (PEN, TET, ERY) than with more recent ones, which indicates more stable results (AMC, AMX, AMP, and DOX). P. intermedia appeared to be the bacteria most resistant to penicillins and showed the highest coefficient variation. Together with scaling and root planing, the combination of two antibiotics would therefore seem to be recommended in the treatment of aggressive periodontitis, particularly in the presence of P. intermedia.     

Antimicrobial resistance in the subgingival microflora in patients with adult periodontitis. A comparison between The Netherlands and Spain

BACKGROUND: The widespread use of antibiotics for prophylaxis and treatment of bacterial infections has lead to the emergence of resistant human pathogens. Great differences have been documented between European countries in the use of systemic antibiotics. In parallel, significant differences in levels of resistant pathogens have been documented. AIM: To investigate whether differences in antibiotic use influence the level of antimicrobial resistance of the subgingival microflora of untreated patients with adult periodontitis in The Netherlands and Spain. METHOD: Blood agar plates containing breakpoint concentrations of penicillin, amoxicillin, amoxicillin and clavunalate, metronidazole, erythromycin, azithromycin, clindamycin and tetracycline were used to determine the proportion of bacteria from the subgingival plaque that was resistant to these antibiotics. In the Spanish patients, statistically significant higher mean levels of resistance were found for penicillin, amoxicillin, metronidazole, clindamycin and tetracycline. The mean number of different bacterial species growing on the selective plates was higher in the Spanish patients, as was the % of resistant strains of most periodontal pathogens. A striking difference was observed in the frequency of occurrence of tetracycline-resistant periodontal pathogens. In Spain, 5 patients had > or =3 tetracycline resistant periodontal pathogens, whereas this was not observed in any of the Dutch patients. CONCLUSIONS: The widespread use of antibiotics in Spain is reflected in the level of resistance of the subgingival microflora of adult patients with periodontitis.     

原发性根尖周感染中牙龈卟啉单胞菌kgp基因多态性

目的　通过牙龈卟啉单胞菌（Porphyromonas gingivalis,Pg）kgp基因型在原发性根尖周感染患牙根管中的分布情况,了解kgp基因在原发性根尖周感染中的基因多态性,并分析不同基因型与临床症状的相关性。方法　临床收集190例原发性根尖周感染患者,采集感染根管细菌学样本,抽提DNA,使用Pg的16S rRNA基因的特异引物PCR检测样本中是否有Pg,然后针对Pg检出阳性样本,再使用kgp特异引物PCR获得kgp催化域片段,通过Tru I酶切kgp催化域片段确定kgp的基因型,并使用Pearson χ2方法分析所得到的实验数据。结果　在本研究所采集的190例原发性根尖周感染样本中,共检出Pg55例,其中kgpⅠ型检出率为27.3%, kgp Ⅱ型检出率为38.2%。Pg的检出与临床症状有相关性;kgpⅠ型与疼痛具有相关性。结论　原发性根尖周感染的根管中Pgkgp基因存在基因多态性。因为有些样本中Pg的量较少,本研究中kgp特异引物PCR的方法难以检测到kgp基因,所以今后需发展更灵敏的检测手段以对感染根管中kgp基因做进一步的研究。