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.