1012. Characterization of Non-typeable Streptococcus pneumoniae in Adults
Session: Poster Abstract Session: Detecting, Identifying, and Typing Bacteria
Saturday, October 22, 2011
Room: Poster Hall B1
Background: Non-typeable Streptococcus pneumoniae (NTPn) are often viewed as colonizing organisms with some reports of localized infections. Newer techniques such as Multi-Locus Sequence Typing (MLST) have characterized NTPn in pediatric populations. Adult literature is limited and no study has evaluated overall prevalence of NTPn and their clinical significance in adults. We aimed to determine NTPn prevalence in adult pneumococcal isolates, use MLST for their genotypic characterization, explore their phylogenetic relatedness to other pneumococci and correlate this information with clinical diagnoses to illuminate their role in disease/carriage states in adults.

Methods: We studied 416 isolates identified as pneumococci in microbiology laboratory, Veterans Affairs Medical Center, Houston. They were obtained from nasopharynx, expectorated sputum, bronchoscopic washing, pleural or peritoneal fluid, middle ear fluid, wound/abscess, urine and blood. We performed standard phenotypic assays and confirmed non-typeability with capsular serotyping or quelling reaction with omniserum.  We used MLST to define true NTPn and calculated their prevalence. We also performed phylogenetic analysis and correlated laboratory findings with clinical data.

Results: Phenotypic assays identified 32 NTPn (18 optochin-sensitive and 14 optochin-resistant isolates of which 7 were bile-sensitive and 7 bile-resistant). Of these, only 5 isolates amplified internal fragments of all pneumococcal housekeeping genes and were sequenced. Sequence analysis of the alleles according to S.pneumoniae MLST scheme revealed only 2 alleles that had been previously deposited in the database. Remaining alleles exhibited 95-99% homology with existing alleles. Our study revealed 5 putative NTPn of which 3 were isolated from carriage state and 2 from patients with tracheobronchitis. No NTPn was responsible for invasive pneumococcal disease.

Conclusion: True NTPn form a small percentage of pneumococcal population in adults. 1.2% of organisms originally identified to be pneumococci were found to be putative NTPn. Our study challenges the validity of currently accepted pneumococcal identification assays to identify and characterize NTPn.

Subject Category: D. Diagnostic microbiology

Shruti Patel, MD1, Adriana M. Rueda, MD2,3, Charles Stager, PhD4, Kristina Hulten, PhD5 and Daniel Musher, MD, FIDSA2,3, (1)Section of Infectious Diseases, Baylor College of Medicine, Houston, TX, (2)Michael E. DeBakey VA Medical Center, Houston, TX, (3)Baylor College of Medicine, Houston, TX, (4)Baylor College of Medicine , Houston, TX, (5)Baylor College of Medicine and Texas Children's Hospital, Houston, TX


S. Patel, None

A. M. Rueda, None

C. Stager, None

K. Hulten, None

D. Musher, None

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.