Quantification of Porphyromonas gingivalis and fimA genotypes in smoker chronic periodontitis

Aim: Porphyromonas gingivalis fim A genotypes were associated with virulence factors in vitro , but little evidence of an association with disease severity were shown in humans. We aimed to correlate levels of P. gingivalis fimA genotypes II and IV and probing depth in smoker-chronic periodontitis subjects.
Material and Methods: One hundred and sixty eight subgingival samples of 20 smokers non-treated chronic periodontitis subjects obtained from sites with different probing depths [shallow (3 mm), intermediate (4–6 mm), deep (7 mm)] were analysed by real-time PCR for P. gingivalis and genotypes fimA II and IV.
Results: P. gingivalis and fimA IV were detected in all subjects, whereas fimA II was detected in 18 subjects (90%). One hundred and fifty two sites (90.5%) harboured P. gingivalis . Genotypes II and IV were detected in 28% and 69.6% of sites, respectively. The proportions of genotypes II and IV in relation to P. gingivalis levels were similar in shallow, intermediate and deep probing sites (2.4%, 4.6%, 1.4% for genotype II and 15.5%, 17.7%, 11.7% for genotype IV, respectively), indicating that other non-tested genotypes were more abundant. Increased levels of genotype IV were associated with increasing probing depth, but not of genotype II.
Conclusions: The data suggested an association between P. gingivalis genotype fimA IV and disease severity in smoker-chronic periodontitis subjects.     

大黄素-8-O-β-D-吡喃葡萄糖苷对牙龈卟啉单胞菌唾液酸酶活性及其毒力基因表达影响研究

目的    探讨大黄素-8-O-β-D-吡喃葡萄糖苷对牙龈卟啉单胞菌（P. gingivalis）唾液酸酶活性及其毒力基因表达的影响。方法    使用不同质量浓度的大黄素-8-O-β-D-吡喃葡萄糖苷（0.2、0.5、2、5、10 mg/mL）处理P. gingivalis W83（实验组）,用未加药物的P. gingivalis W83作对照（对照组）,采用荧光法检测大黄素-8-O-β-D-吡喃葡萄糖苷对P. gingivalis唾液酸酶活性的作用。5 mg/mL大黄素-8-O-β-D-吡喃葡萄糖苷作用于P. gingivalis W83,Real-time PCR法检测毒力基因fimA、fimR、fimS、kgp、rgpA和rgpB的表达情况。结果    大黄素-8-O-β-D-吡喃葡萄糖苷对P. gingivalis唾液酸酶活性产生了抑制作用,当其质量浓度为0.2、0.5、2、5、10 mg/mL时,对唾液酸酶活性的抑制率分别为11.4%、32.23%、40.21%、73.54%、84.31%。与对照组比较,实验组（5 mg/mL大黄素-8-O-β-D-吡喃葡萄糖苷处理）的fimA、fimR、fimS、kgp、rgpA和rgpB基因表达均下降,差异均有统计学意义（均P < 0.05）。结论    大黄素-8-O-β-D-吡喃葡萄糖苷可有效抑制P. gingivalis唾液酸酶活性,其抑制作用会降低细菌毒力基因表达,有望成为预防及治疗牙周炎的新型药物。     

Prevalence of fimA genotypes of Porphyromonas gingivalis and periodontal health status in Chinese adults

Background and Objective:  Porphyromonas gingivalis fimbriae play a key role in colonization of the oral cavity. The fimA gene, which encodes fimbrillin ( FimA ), can be classified into six types (I–V and Ib) according to nucleotide sequence. In the present study, we investigated the relationship between the prevalence of P. gingivalis -specific fimA genotypes and periodontal health status in Chinese adults.
Material and Methods:  One-hundred and fifteen patients with chronic periodontitis and 136 periodontally healthy adults were selected. P. gingivalis detection, determination of fimA genotypes, and the co-existence of Actinobacillus actinomycetemcomitans and Tannerella forsythia with various fimA types, were assessed by the polymerase chain reaction. Odds ratios and 95% confidence intervals were calculated for associating the fimA -specific genes with periodontitis.
Results:  P. gingivalis was detected in 22.1% of healthy subjects and in 81.7% of the patients. A single fimA genotype was detected in most samples. In healthy adults, the most prevalent fimA genotype was type I (66.7%). However, type II was detected most frequently (43.6%) in the patient group, followed by type IV (30.9%). The frequency of co-existing A. actinomycetemcomitans and T. forsythia was highest in type II fimA -positive sites. Statistical analysis revealed that periodontitis was associated with occurrences of type I (odds ratio 0.97), Ib (odds ratio 13.26), II (odds ratio 36.62), III (odds ratio 4.57), IV (odds ratio 22.86) and V (odds ratio 1.19).
Conclusion:  P. gingivalis type II followed by type IV were considered as disease-associated strains that account for the pathogenesis of chronic periodontitis in Chinese adults.     

Genotypic characterization of Porphyromonas gingivalis isolated from subgingival plaque and blood sample in positive bacteremia subjects with periodontitis

Aim: The objective of this study was to investigate clonal relationship among Porphyromonas gingivalis isolated from subgingival plaque and blood samples in positive transient bacteremia subjects with periodontitis.
Material and Methods: Unrelated patients with general chronic periodontitis or general aggressive periodontitis requiring scaling and root planing (SRP) were included in the study. Genotyping of each isolate was performed using pulsed field gel electrophoresis technique. Genetic relatedness of strains isolated within an individual or between different patients was determined by dendogram analysis.
Results: Following SRP, from 16 patients, seven patients showed positive P. gingivalis bacteremia and nine were negative. Thirty-two strains were isolated from subgingival plaque and blood samples before and during induced transient bacteremia. The majority of the patients harboured one clonal type. Two patients showed different clones in plaque and blood samples suggesting that more than one clone can be found in subgingival plaque. P. gingivalis isolates from periodontitis patients after transient bacteremia following SRP, revealed a high heterogeneity among isolates.
Conclusion: In 6/16 subjects the same P. gingivalis isolate was found in the blood and in oral cavity. P. gingivalis heterogeneity suggests no association of a unique clonal type with transient bacteremia.     

牙龈卟啉菌蛋白酶基因rgpA与rgpB蛋白酶区的克隆和表达

目的克隆牙龈卟啉单胞菌(Porphyromonas gingivalis,Pg)rgpA、rgpB蛋白酶区,构建rgpA、rgpB蛋白酶区原核表达系统。方法采用聚合酶链式反应(PCR)从PgATCC33277菌株中扩增rgpA、rgpB蛋白酶区,T-A克隆后测定核苷酸序列,构建pET42a的rgpA/rgpB蛋白酶区表达载体,在E.coli BL21DE3宿主菌中用不同浓度的IPTG诱导其表达。结果所克隆的PgATCC33277菌株rgpA、rgpB基因蛋白酶区的核苷酸序列与报道的相应核苷酸序列同源性分别为98.9%、99.0%,氨基酸序列同源性分别高达99.2%、99.1%。pET42a-rgpA/rgpB-E.coli BL21DE3系统的蛋白表达量为细菌总蛋白的60%左右。结论本研究成功地构建PgrgpA、rgpB蛋白酶区高效表达系统,为测定RgpA、RgpB免疫原性及作用提供前提。     

慢性牙周炎患者龈下菌斑中不同基因型牙龈卟啉单胞菌的检测

摘要 目的:建立临床标本中牙龈卟啉单胞菌(P.g)的PCR检测方法,探讨慢性牙周炎患者不同牙位的龈下菌斑中P.g基因型的差异。方法:采用培养法分离鉴定慢性牙周炎患者不同牙位龈下菌斑中P.g,同时采用PCR检测 P.g16SrDNA、prtC和fimA基因。部分扩增产物测定了核苷酸序列。结果:在66例患者的127个龈下菌斑标本中, P.g16SrDNA、prtC和fimA多重引物扩增的阳性率为9814%;PCR阳性率显著高于培养法P.g的检出率(P< 0101)。3010%的患者(18/60)同时感染了不同基因型的P.g菌株。P.g16SrDNA、prtC和fimA扩增片段的核苷酸序列同源性在98162%~100%之间。结论:本文所建立的P.g的PCR检测方法具有较高的敏感性和特异性,适用于P.g的快速临床诊断。同一患者可被不同感染来源的多株P.g同时感染。     

Mixed infection of Porphyromonas gingivalis and Bacteroides forsythus in a murine abscess model: involvement of gingipains in a synergistic effect

Several microorganisms including Porphyromonas gingivalis and Bacteroides forsythus have been implicated to be etiologically important agents of periodontal disease. In this study, we determined the ability of combinations of periodontopathogenic microorganisms to cause tissue destruction in a murine abscess model. Although all bacterial combinations used in this study produced larger abscesses than did monoinfection of each bacterium, the combination of P. gingivalis and B.forsythus showed a synergistic effect on abscess formation. Since these two bacteria have been frequently found together in lesions of periodontitis, these results suggest the significance of their co-infection in the progression of periodontitis. P. gingivalis produces extracellular and cell-associated cysteine proteinases (gingipains) which appear to be involved in its virulence. The rgpA rgpB double and kgp mutants induced significantly smaller abscesses than the wild type. Moreover, the rgpA rgpB kgp triple (gingipain-null) mutant hardly showed lesion formation at all with the experimental conditions used in this study, indicating that these genes encoding gingipains are important for virulence of P. gingivalis. Mixed infection of these P. gingivalis mutants with B. forsythus showed an additive effect on abscess formation, indicating that the gingipains of P. gingivalis may play an important role in the pathological synergism between P. gingivalis and B. forsythus.     

Progression of chronic periodontitis can be predicted by the levels of Porphyromonas gingivalis and Treponema denticola in subgingival plaque

Introduction:  Chronic periodontitis is an inflammatory disease of the supporting tissues of the teeth associated with bacteria. Diagnosis is achieved retrospectively by clinical observation of attachment loss. Predicting disease progression would allow for targeted preventive therapy. The aim of this study was to monitor disease progression in patients on a maintenance program and determine the levels of specific bacteria in subgingival plaque samples and then examine the ability of the clinical parameters of disease and levels of specific bacteria in the plaque samples to predict disease progression.
Methods:  During a 12-month longitudinal study of 41 subjects, 25 sites in 21 subjects experienced disease progression indicated by at least 2 mm of clinical attachment loss. Real-time polymerase chain reaction was used to determine the levels of Porphyromonas gingivalis , Treponema denticola , Tannerella forsythia , Fusobacterium nucleatum , and Prevotella intermedia in subgingival plaque samples.
Results:  No clinical parameters were able to predict periodontal disease progression. In sites undergoing imminent periodontal disease progression within the next 3 months, significant partial correlations were found between P. gingivalis and T. forsythia ( r  = 0.55, P  < 0.001) and T. denticola and T. forsythia ( r  = 0.43, P  = 0.04). The odds of a site undergoing imminent periodontal disease progression increased with increasing levels of P. gingivalis and T. denticola .
Conclusion:  Monitoring the proportions of P. gingivalis and T. denticola in subgingival plaque has the potential to help identify sites at significant risk for progression of periodontitis, which would assist in the targeted treatment of disease.     

Relationship of Porphyromonas gingivalis with glycemic level in patients with type 2 diabetes following periodontal treatment

Introduction:  The aim of this study was to assess the relationship between serum glycemic levels and subgingival microbial profile alteration following periodontal treatment in patients with type 2 diabetes mellitus.
Methods:  We studied 30 periodontitis patients with type 2 diabetes mellitus who received full-mouth subgingival debridement by analyzing their subgingival microbial profiles using a polymerase chain reaction method at baseline and various time-points for 12 months following treatment. Concurrently, probing pocket depth, bleeding on probing, and metabolic parameters, including glycated hemoglobin A1c (HbA1c), blood sugar level, C-reactive proteins, total cholesterol, triglyceride, and high-density and low-density lipoprotein cholesterol, were recorded.
Results:  Periodontal conditions were significantly improved after treatment, and the occurrence rates of periodontal bacterial species, including Porphyromonas gingivalis , Tannerella forsythensis , Treponema denticola , and Prevotella intermedia , were also reduced. Interestingly, P. gingivalis was detected more frequently in subjects with increased HbA1c values after periodontal treatment than in those patients with decreased HbA1c values. Furthermore, P. gingivalis with type II fimbriae was detected only in HbA1c-increased subjects, while improvements in HbA1c values were observed only in subjects without type II clones.
Conclusions:  These results suggest that glycemic level in diabetes is affected by the persistence of P. gingivalis , especially clones with type II fimbriae, in periodontal pockets.     

龈下菌斑中牙龈卟啉单胞菌牙龈素基因片段的检测

目的：检测慢性牙周炎患者龈下菌斑中牙龈卟啉单胞菌（Porphyromonas gingivalis,P.gingivalis）的2个基因片段kgp-cd和rgpB-cd,探讨2个基因片段的存在和缺失与牙周临床指标之间的关系.方法：选择慢性牙周炎患者龈下菌斑84个,对P.gingivalis阳性的龈下菌斑样本进行kgp-cd和rgpB-cd基因片段检测;根据2个基因片段的有无,将P.gingivalis分为A型和B型,采用SPSS11.5统计软件包,用t检验和x2检验分析不同基因型P.gingivalis与牙周临床指标的关系.结果：A型P.gingivalis在慢性牙周炎中的检出率高于B型（P＜0.05）,分别为85.29%和14.71%.不同基因型P.gingivalis引起的牙周袋探诊深度和牙龈出血倾向存在显著性差异（PD：t=2.85,P＜0.05;BOP：P＜0.05）.结论：kgp-cd和rgpB-cd基因与P.gingivalis的致病性有关.     

The effect of Porphyromonas gingivalis infection on cytokine levels in type 2 diabetic mice

Background and Objective:  Several studies have shown that diabetes mellitus increases the severity of periodontitis. Conversely, periodontitis has been shown to have an impact on diabetes, although the underlying mechanisms of this are unclear. The aim of this study was to compare the inflammatory response to Porphyromonas gingivalis infection in normal and diabetic mice.
Material and Methods:  Porphyromonas gingivalis were inoculated adjacent to the periosteum, at a point on the midline of the skull located between the ears, in C57BL/6 (normal) and KKAy (diabetic) mice. After induction, the levels of tumor necrosis factor-α, interleukin-6 and adiponectin in the mice were measured using real-time polymerase chain reaction and enzyme-linked immunosorbent assay.
Results:  The KKAy mice showed significant increases in blood glucose, serum tumor necrosis factor-α and interleukin-6 levels after inoculation with Porphyromonas gingivalis , and a significant decrease in adiponectin to 35.7%. Similar results were observed at the mRNA level in liver and visceral adipose tissue.
Conclusion:  These observations suggest that tumor necrosis factor-α, interleukin-6 and adiponectin are an integral part of the link between diabetes mellitus and Porphyromonas gingivalis infection.     

Effect of enamel matrix derivative on periodontal ligament cells in vitro is diminished by Porphyromonas gingivalis

BACKGROUND: Enamel matrix derivative (EMD) has been shown to possess a mitogenic effect to induce effective periodontal regeneration, however, it is unclear whether periodontal pathogens can modulate the effect of EMD. The present study examined the influence of Porphyromonas gingivalis on EMD-stimulated periodontal ligament (PDL) cells. METHODS: P. gingivalis ATCC33277 and its mutants deficient in fimbriae (delta fimA) or gingipains (delta rgpA delta rgpB, delta kgp, and delta rgpA delta rgpB delta kgp) were employed. PDL cells were grown on EMD-coated dishes and infected with P. gingivalis wild strain or a mutant. Cell migration and proliferation were then evaluated with an in vitro wound healing assay. The expression of transforming growth factor-beta1 (TGF-beta1) and insulin-like growth factor I (IGF-I) mRNA by PDL cells was examined. Further, the degradation and phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) as well as paxillin in infected PDL cells were estimated using Western blot analysis. RESULTS: P. gingivalis ATCC33277 inhibited the migration and proliferation of PDL cells on EMD-coated dishes, and the mutants delta fimA, delta rgpA delta rgpB, and delta kgp showed the same effects. Further, each of these organisms diminished the expression of TGF-beta1 and IGF-I mRNA, as well as the phosphorylation of ERK1/2 from EMD-stimulated PDL cells. In addition, total paxillin protein was markedly degraded by both the wild-type strain and each of the mutants except for delta rgpA delta rgpB delta kgp, which showed a negligible effect in all of the assays with EMD-stimulated PDL cells. CONCLUSION: These results suggest that P. gingivalis diminishes the effect of EMD on PDL cells in vitro through a cooperative action of gingipains.     

Prevalence of Porphyromonas gingivalis fimA genotypes in Caucasians

The aim of the present study was to determine the prevalence of Porphyromonas gingivalis fimA genotypes in Caucasian patients with periodontitis. A total of 102 patients harboring P. gingivalis subgingivally were enrolled into the study. Pooled subgingival plaque samples of the six most severely affected sites were taken and analysed by fimA-specific polymerase chain reaction (PCR) and restriction analysis. Moreover, 26 P. gingivalis isolates were analysed by sequence analysis of the fimA gene. Sequence analysis revealed five major fimA genotypes (fimA types I-V) and allowed further subtyping of fimA genotypes II and IV into two subgroups each. The overall prevalences of fimA genotypes as assessed by PCR and restriction analysis among the P. gingivalis-positive patients with periodontitis were: type I, 25.5%; type II, 38.2%; type III, 4.9%; type IV, 18.6%; type V, 3.9%; and non-typable, 6.9%. Two patients were colonized by both type II and type IV, or type III and type IV fimA genotypes, respectively. Patients harboring different fimA genotypes showed no significant difference in severity of periodontal disease, as assessed by pocket probing depth and bleeding on probing following adjustment for smoking habit and age. The results indicate that predominant fimA genotypes in Caucasian periodontitis patients are types I, II, and IV. However, there was no difference in the association of the various fimA genotypes with disease severity.     

不同fimA基因型牙龈卟啉单胞菌在慢性牙周炎患者中的分布

目的　分析不同fimA基因型牙龈卟啉单胞菌(P.gingivalis)在慢性牙周炎患者中的分布状况。方法　收集101例慢性牙周炎患者的龈下菌斑,采用常规培养法和16S rRNA PCR检测P.gingivalis,并根据各fimA基因型的特异引物,用聚合酶链反应(PCR)检测不同fimA基因型菌株的分布。结果　16S rRNA PCR检测P.gingivalis阳性检出率为88·1%。大多数受检牙龈下菌斑中只检测出一种fimA基因型菌株(65·1%),各fimA基因型的总检出率: ⅠfimA为24·7%;ⅡfimA为43·8%;ⅢfimA为15·7%;ⅣfimA为40·4%;VfimA为3·4%。结论　慢性牙周炎患者龈下菌斑中的牙龈卟啉单胞菌存在fimA基因多态性,ⅡfimA和ⅣfimA基因型P.gingivalis菌株与慢性牙周炎的发生发展关系密切。     

Antibody responses to Porphyromonas gingivalis infection in a murine abscess model--involvement of gingipains and responses to re-infection

BACKGROUND: Porphyromonas gingivalis is one of the most important periodontopathogens. It produces cysteine proteinases named gingipains. We previously examined the effect of gingipains on abscess formation in a murine model. The rgpA rgpB double and kgp mutants induced smaller abscesses than the wild type. Moreover, the rgpA rgpB kgp triple (gingipain-null) mutant hardly showed lesion formation at all under the experimental conditions used, indicating that genes encoding gingipains are important for P. gingivalis virulence. OBJECTIVES: Here, we further report the humoral immune responses induced by P. gingivalis strains. METHODS: After the lesions were apparently cured, sera were collected from the mice and immunoglobulin G (IgG) responses against the whole cell antigens of wild-type P. gingivalis were measured. RESULTS: Wild-type strain was found to induce a strong antibody reaction. On the other hand, the rgpA rgpB kgp triple and kgp mutants induced significantly lower antibody responses compared to the wild type. Western blotting analysis confirmed the differences in antibody production. Next, these mice were re-infected with wild-type strain. Mice that were first infected with wild-type strain showed significantly smaller lesion formation than control mice that were first infected with medium only. On the other hand, mice that were first infected with mutant strains devoid of gingipain activities did not show resistance to re-infection and immunoglobulins directed against gingipains may be protective. CONCLUSIONS: These results suggest that gingipains play an important role in abscess formation in mice, and humoral immune responses seem to be partly responsible for the resistance to re-infection by P. gingivalis.     

Comparative analysis of putative periodontopathic bacteria by multiplex polymerase chain reaction

Background and Objective:  The polymerase chain reaction (PCR) has been applied for the rapid and specific detection of periodontopathic bacteria in subgingival plaque and is potentially of clinical benefit in the diagnosis and treatment of periodontitis subjects. However, several technical points need to be modified before the conventional PCR detection system can be used by clinicians.
Material and Methods:  To develop a PCR-based technique more applicable for clinical use than conventional PCR, we established a multiplex PCR for five putative periodontopathic ( Treponema denticola , Porphyromonas gingivalis , Aggregatibacter actinomycetemcomitans , Prevotella intermedia and Tannerella forsythia ) and two nonperiodontopathic ( Streptococcus sanguinis and Streptococcus salivarius ) species of bacteria using whole-plaque suspension as templates, and detected bacteria in subgingival plaque taken from 85 subjects at the supportive periodontal therapy stage after active periodontal treatments.
Results:  Among putative periodontopathic bacteria, the detection frequency of T. denticola and P. gingivalis was elevated in parallel with higher probing pocket depth and clinical attachment loss, and had 4.2–14.1 times increasing odds of the clinical parameters tested. Detection of any of the five species of putative periodontopathic bacteria markedly increased the odds ratio of a higher probing pocket depth, clinical attachment loss and bleeding on probing.
Conclusion:  The multiplex PCR system developed in this study enabled the detection of all the bacteria under investigation in one reaction tube in a less time- and labor-intensive manner than conventional PCR. These results support the potential clinical use of multiplex PCR for detecting periodontopathic bacteria and for evaluating therapeutic strategies and predicting the prognosis for each subject.     

牙龈卟啉单胞菌在龈下菌斑和颊黏膜中的检测

目的　检测牙周健康者及牙周炎患者在颊黏膜和龈下菌斑中牙龈卟啉单胞菌的阳性率,探讨其与牙周炎发生和发展的关系。方法　选取40例牙周健康者和39例慢性牙周炎患者,分别收集颊黏膜和龈下菌斑样本,提取细菌DNA,设计细菌通用引物和牙龈卟啉单胞菌的特异引物用于PCR扩增,检测牙龈卟啉单胞菌的阳性率。结果　牙周健康组菌斑样本和颊黏膜样本牙龈卟啉单胞菌的阳性率分别为37·5%和32·5%,而牙周炎组菌斑样本和颊黏膜样本牙龈卟啉单胞菌的阳性率分别为69·23%和46·15%。牙周炎组菌斑的牙龈卟啉单胞菌阳性率高于牙周健康组,颊黏膜的牙龈卟啉单胞菌阳性率在组间无统计学差异;牙周炎组菌斑牙龈卟啉单胞菌阳性率高于颊黏膜, 牙周健康组两部位阳性率无统计学差异。结论　牙龈卟啉单胞菌除在菌斑中有高检出率外,在颊黏膜中也有较高的检出率,提示颊黏膜也是牙周细菌在口腔定植的重要部位,牙龈卟啉单胞菌也可在健康人群中检出,提示其有可能是口腔内固有菌群之一。     

Susceptibility of type 2 diabetic mice to low-virulence bacterial infection: induction of abscess formation by gingipain-deficient Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE: Type 2 diabetes mellitus is considered an important risk factor of adult periodontitis. However, recent studies have revealed that the subgingival microbial flora of diabetes mellitus patients does not differ from that of healthy individuals. In this study, we examined the response of type 2 diabetes mellitus hosts to low-virulence bacteria in a murine abscess model. MATERIAL AND METHODS: Porphyromonas gingivalis ATCC 33277 or KDP128 (rgpA rgpB kgp) were injected into two mouse strains - C57BL/6J and its derivative, KK/A(Y), which becomes diabetic spontaneously. RESULTS: Lesions of KK/A(Y) mice injected with either low-virulence P. gingivalis KDP128 or wild-type 33277 were significantly larger than those of C57BL/6J mice injected with the same strains. Histologically, more neutrophils and macrophages migrated to the lesions in the KK/A(Y) mice injected with P. gingivalis 33277 and KDP128 compared with those of C57BL/6J mice injected with the same respective strains. CONCLUSION: These results suggest that severe inflammation is observed in response to low-virulence bacteria in addition to the highly virulent bacteria in type 2 diabetes mellitus hosts.     

Distribution of fimA genotypes of Porphyromonas gingivalis in subjects with various periodontal conditions

Fimbria encoded by the gene fimA is considered one of the main factors in the colonization of the oral cavity by Porphyromonas gingivalis. Allelic variation in fimA led to the classification of strains of P. gingivalis into six genotypes. The occurrence of P. gingivalis was determined by polymerase chain reaction using 16S rRNA primers in 302 subgingival samples obtained from 102 Brazilian subjects exhibiting different periodontal conditions. Distribution of fimA genotypes was assessed in 146 P. gingivalis positive samples by polymerase chain reaction using primers pairs homologous to the different fimA genes. P. gingivalis was detected in 51 of 57 (89.4%) patients with periodontal attachment loss, in six of 20 gingivitis patients (30.0%) and in two of 25 (8.0%) subjects with a healthy periodontium. Variant type II was the only type detected in 53 sites (39.3%), distributed among 19 periodontitis patients (37.3%) and in one patient with no periodontal destruction. Type Ib was the second most prevalent genotype in periodontitis patients (19.6%). Genotype V was not detected in the studied population. Type IV was the most commonly type found among gingivitis patients, either alone or in combination with other genotypes. Multiple genotypes were detected in nine sites (6.1%). A fimA genotype was not identified in 26 sites (17.8%) of 146 sites positive for P. gingivalis, suggesting that other alleles of fimA not yet sequenced may be prevalent in this population. These data demonstrated that P. gingivalis type II strains followed by type Ib are more prevalent in periodontitis patients from a multiracial population in Brazil, suggesting an increased pathogenic potential of these types.