title: Rapid identification of Streptococcus pneumoniae in blood cultures by using the ImmuLex, Slidex and Wellcogen latex agglutination tests and the BinaxNOW antigen test.
abstract: Rapid identification of Streptococcus pneumoniae in blood culture (BC) bottles is important for early directed antimicrobial therapy in pneumococcal bacteraemia. We evaluated a new latex agglutination (LA) test on BC bottles, the ImmuLex™ S. pneumoniae Omni (Statens Serum Institut, Denmark), and compared the performance with the Slidex® pneumo-Kit (bioMérieux, France) and the Wellcogen™ S. pneumoniae (Remel, UK) LA tests, as well as the BinaxNOW® S. pneumoniae (Alere, USA) antigen test. The four tests were directly applied on 358 positive BC bottles with Gram-positive cocci in pairs or chains and on 15 negative bottles. Valid test results were recorded in all cases for ImmuLex and BinaxNOW and in 88.5 % (330/373) and 94.1 % (351/373) of cases for Slidex and Wellcogen, respectively. Based on bottles positive for S. pneumoniae by conventional methods, the sensitivity of ImmuLex was 99.6 %, similar to the other tests (range, 99.6-100 %). Based on bottles positive for non-pneumococcal pathogens, the specificity of ImmuLex was 82.6 %, in comparison to 97.6 % for Slidex (p < 0.01) and 85.4 % for Wellcogen (p = ns). The BinaxNOW test had a lower specificity (64.1 %) than any LA test (p < 0.01). On BC bottles positive for α-haemolytic streptococci, ImmuLex was positive in 12/67 (17.9 %) cases, Slidex in 2/59 (3.4 %) cases, Wellcogen in 11/64 (17.2 %) cases and BinaxNOW in 25/67 (37.3 %) cases. In conclusion, the ImmuLex test provides a valid and sensitive technique for the rapid detection of S. pneumoniae in BC bottles, similar to the other compared methods. However, the specificity was sub-optimal, since the test may cross-react with other Gram-positive bacteria.
authors.affiliation: Division of Clinical Microbiology F 72, Karolinska Institutet, Karolinska University Hospital, Huddinge, 141 86, Stockholm, Sweden.
authors.forename: O
authors.initials: O
authors.lastname: Altun
authors.affiliation: Department of Infectious Diseases, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Athlin
authors.affiliation: Division of Clinical Microbiology F 72, Karolinska Institutet, Karolinska University Hospital, Huddinge, 141 86, Stockholm, Sweden.|Department of Microbiology, Faculty of Medicine, King Abdul-Aziz University, P.O. Box 80205, Jeddah, 21589, Saudi Arabia.
authors.forename: M
authors.initials: M
authors.lastname: Almuhayawi
authors.affiliation: Department of Infectious Diseases, Karolinska Institutet, Karolinska University Hospital, Huddinge, Stockholm, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Strålin
authors.affiliation: Division of Clinical Microbiology F 72, Karolinska Institutet, Karolinska University Hospital, Huddinge, 141 86, Stockholm, Sweden. volkan.ozenci@karolinska.se.
authors.forename: V
authors.initials: V
authors.lastname: Özenci
mesh_terms: D016470:Bacteremia / Q000175:diagnosis*; D003955:Diagnostic Tests, Routine / Q000379:methods*; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D011008:Pneumococcal Infections / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D013296:Streptococcus pneumoniae / Q000302:isolation & purification*; D013997:Time Factors