Streptococcus pneumoniae Serotyping by a Single Polymerase Chain Reaction-Based Multiplex Assay.

Background: Streptococcus pneumoniae is a prominent pathogen in children younger than 5 years as well as elderly people. Capsular serotyping of S. pneumoniae is necessary to develop the new vaccines and prevent invasive and noninvasive infections by S. pneumoniae. In this study, we used 2-step multiplex polymerase chain reaction (mPCR) that contained primers to detect PCV13 (13-valent pneumococcal conjugated vaccine) and non-PCV13 serotypes in different clinical and normal flora samples. Methods: A total of 100 S. pneumoniae isolates were obtained between 2013 and 2015 in Tehran, Iran. The sources of isolates were clinical and normal flora. Clinical isolates were eye infection (26%), blood (19%), sputum (18%), sinusitis and cerebrospinal fluid (9% each), trachea (7%), pleural aspirate (3%), otitis (3%), and urine, bronchoalveolar lavage, and abscess (2% each). Moreover, 43 normal flora isolates were collected from healthy individuals. The strain isolates were tested for antimicrobial susceptibility and serotyped by mPCR. Results: The highest rate of resistance was seen for trimethoprim-sulfamethoxazole (96%) followed by tetracycline (77%), erythromycin (64%), clindamycin (56%), chloramphenicol (44%), and penicillin (26%). All isolates were susceptible to imipenem, ceftriaxone, vancomycin, linezolid, gemifloxacin, levofloxacin, moxifloxacin, and ofloxacin. By using mPCR, 91 and 7 isolates were typed in the first and second reactions, respectively. Two isolates were identified as nontypeable. The most frequent serotypes in 98 typeable serotypes were 23F (n = 21 [22%]), 14 (n = 19 [20%]), 3 (n = 13 [13%]), and 19F (n = 13 [13%]). Conclusions: Our multiplex assay is a precise and reliable method that can be used instead of the Quellung reaction for S. pneumoniae serotyping studies. Copyright (C) 2017 Wolters Kluwer Health, Inc. All rights reserved.

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