107 Int. J. Odontostomat., 7(1):107-112, 2013. Distribution of Serotype-specific Genotypes of Aggregatibacter actinomycetemcomitans in Brazilian Patients with Down Syndrome with Different Periodontal Conditions Distribución de los Serotipos Genotipos Específicos de Aggregatibacter actinomycetemcomitans en los Pacientes Brasileños con Síndrome de Down con Diferentes Condiciones Periodontales Elerson Gaetti Jardim Júnior * ; Doris Hissako Sumida ** & Christiane Marie Schweitzer *** GAETTI-JARDIM JÜNIOR, E.; SUMIDA, D. H. & SCHWEITZER, C. M. Distribution of serotype-specific genotypes of Aggregatibacter actinomycetemcomitans in Brazilian patients with Down syndrome with different periodontal conditions. Int. J. Odontostomat., 7(1):107-112, 2013. ABSTRACT: This study evaluated the occurrence of highly or minimally leukotoxic strains of Aggregatibacter actinomycetemcomitans (Aa) from patients with Down syndrome and the distribution of the different serotype-specific genotypes of this microorganism. Sixty-seven patients with Down syndrome were subjected to dental, periodontal and radiographic evaluations. Samples of subgingival biofilm were collected and plated onto TSBV agar and characteristic colonies of A. actinomycetemcomitans were identified by biochemical methods. The occurrence of this bacterium was also evaluated directly in the clinical specimens by PCR. The presence of 530 bp deletion in the promoter region was also determined by PCR in order to evaluate distribution of highly or minimally leukotoxic strains. A. actinomycetemcomitans was detected in 11.1% by culture and 22.2% by PCR from periodontally healthy subjects, 100% of the patients with Down syndrome with aggressive periodontitis, 50% and 75% of patients with chronic periodontitis by culture and PCR respectively. Only two patients with aggressive periodontitis were colonized by highly leukotoxic Aa. Serotype-specific genotypes a and c were the most prevalent. The results suggest the role of peculiar characteristics of Aa and patients with Down syndrome in the development of periodontitis and the influence of peculiar characteristics of the population in this process. KEY WORDS: gingivitis, bacteria, periodontitis, down syndrome. INTRODUCTION Down syndrome (DS) is a genetic disorder caused by an extra chromosome 21, with an incidence of 1/700 live births, producing several effects on physical and psychological development. Patients with Down syndrome frequently present higher susceptibility to opportunistic infections, particularly gingivitis and periodontitis (Khocht et al., 2012). This susceptibility to aggressive periodontitis has been studied at the level of immune responsiveness, clinical and microbiological aspects (Sakellari et al., 2005; Khocht et al.). In Latin America, due to the great diversity of influences related to human colonization, habits and geographic conditions, these peculiar characteristics are outstanding even within a single country (Herrera et al., 2008). Aggregatibacter actinomycetemcomitans (Aa) is frequently implicated with aggressive episodes of periodontitis and its distribution is influenced by ethnic and geographic characteristics (Haubek et al., 2008). The virulence and distribution of different serotypes of Aa may vary significantly and some serotypes are more closely associated to the development of periodontal breakdown than others. This statement has been discussed particularly in patients with localized forms of aggressive periodontitis, where serotype b is frequently detected, while serotypes a and c have a stronger association with periodontal health or chronic forms of periodontitis (Kaplan et al.; Roman-Torres et al., 2010). However, data on serotypes distribution of Aa in patients with Down syndrome are scarce, * Department of Pathology and Clinical Propaedeutics. School of Dentistry of Araçatuba, UNESP-Univ Estadual Paulista, Araçatuba, SP, Brazil ** Department of Basic Sciences, School of Dentistry of Araçatuba, UNESP-Univ Estadual Paulista, Araçatuba, SP, Brazil *** Department of Mathematics, Faculty of Engineering of Ilha Solteira, UNESP-Univ Estadual Paulista, Ilha Solteira, SP, Brazil, GRANTS: Fundação de Amparo à Pesquisa do Estado de São Paulo, FAPESP. Process number: 2007/51016-3.