title: Evaluation of gene-technological and conventional methods in the identification of Streptococcus pneumoniae.
abstract: To find reliable methods able to identify the "difficult" Streptococcus pneumoniae isolates, an in-house polymerase chain reaction (PCR) for pneumolysin gene (Ply-PCR) and a commercial RNA hybridisation test (AccuProbe) were evaluated. Selected isolates of suspected pneumococci, sent for confirmation of identification and for serotyping, were classified into four groups based on their optochin sensitivity and capsule reaction. All isolates in Group 1, which consisted of 24 typical, optochin-sensitive, encapsulated pneumococcal strains, were positive in the Ply-PCR and AccuProbe tests. In Group 2, which consisted of 25 optochin-sensitive, but unencapsulated pneumococcal strains, all the isolates were positive in the Ply-PCR test, and 23 were positive in the AccuProbe test. In Group 3, which consisted of 15 atypical, optochin-resistant but encapsulated pneumococci, 12 of the isolates were positive in the Ply-PCR and 12 in the AccuProbe test, and 11 of these 12 strains were positive in both tests. In Group 4, which consisted of 36 equivocal optochin-resistant, unencapsulated isolates, 15 strains were positive in the Ply-PCR test and 8 strains in the AccuProbe test. As a conclusion, the Ply-PCR and AccuProbe tests identified similarly typical optochin-sensitive pneumococci, but gave partly controversial results about atypical pneumococci. Thus, they did not reliably help in the identification of suspected pneumococcal isolates lacking the conventional characteristics of pneumococcus.
authors.affiliation: KTL, National Public Health Institute, P.O. Box 310, FIN-90101 Oulu, Finland. tarja.kaijalainen@ktl.fi
authors.forename: Tarja
authors.initials: T
authors.lastname: Kaijalainen
authors.forename: S
authors.initials: S
authors.lastname: Rintamäki
authors.forename: E
authors.initials: E
authors.lastname: Herva
authors.forename: M
authors.initials: M
authors.lastname: Leinonen
mesh_terms: D016667:Bacterial Capsules / Q000032:analysis; D001426:Bacterial Proteins; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D003840:Deoxycholic Acid; D009693:Nucleic Acid Hybridization; D011018:Pneumonia, Pneumococcal / Q000382:microbiology; D016133:Polymerase Chain Reaction; D011803:Quinine / Q000031:analogs & derivatives*; D012680:Sensitivity and Specificity; D013296:Streptococcus pneumoniae / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D013301:Streptolysins / Q000096:biosynthesis / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D013301:Streptolysins; C032290:plY protein, Streptococcus pneumoniae; D003840:Deoxycholic Acid; C017303:ethylhydrocupreine; D011803:Quinine