The Dominance of Pilus Islet 1 in Pneumococcal Isolates Collected From Patients and Healthy Individuals

BACKGROUND Pili in Streptococcus pneumoniae have been shown to be one of the adherence factors for epithelial cells in the human upper respiratory tract. Two types of pilus-like structures (pilus islet-1 and pilus islet-2) have been distinguished in S. pneumoniae. OBJECTIVES To investigate the presence of pilus islet-1 (PI-1) in S. pneumoniae and the correlation between our isolates. MATERIALS AND METHODS In this study, 162 S. pneumoniae isolates were collected from clinical specimens, and normal flora were also examined for the distribution of PI-1 using the presence of the rlrA and rrgC genes as markers for this islet and sipA as an indicator of pilus islet-2 (PI-2). BOX-PCR analyses were performed to determine the genetic relationship between isolates. RESULTS The results confirmed the presence of rlrA and rrgC genes in both clinical (n = 39) and normal flora (n = 26) isolates. The minimal inhibitory concentration results revealed that the rate of resistance of these isolates to the three antibiotics tested ranged from 26% for penicillin to 46% for erythromycin and tetracycline. Furthermore, 12% of the isolates were resistant to all three antibiotics. Strain typing using repetitive element BOX-PCR analysis among the 65 isolates identified 8 different band patterns. CONCLUSIONS Our results indicated that the dissemination of PI-1 was widespread in S. pneumoniae isolates, although no PI-2 isolates were detected. Furthermore, the frequency of rlrA and rrgC of clinical isolates was significantly more than that of normal flora isolates.