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Rapid identification and antimicrobial susceptibility testing of Gram-positive cocci in blood cultures by direct inoculation into the Phoenix system.
Clin Microbiol Infect. 2009 Jul 22;
Authors: Lupetti A, Barnini S, Castagna B, Nibbering PH, Campa M
Abstract Rapid identification and antimicrobial susceptibility testing (AST) of the causative agent(s) of bloodstream infections are essential for selection of the appropriate antimicrobial therapy. To speed up the identification and AST of the causative agent the fluid from blood culture bottles of the Bactec 9240 containing Gram-positive cocci was mixed with saponin. After a 15 min incubation the bacteria were harvested and then applied onto the appropriate Phoenix panels for identification and AST. With this approach, further referred to as the direct method, we concordantly/correctly identified 56 (82%) of the 68 monomicrobial cultures using the results obtained by the method currently used in our laboratory as comparator; two (3%) isolates could not be identified and 10 (15%) were misidentified. Complete agreement in clinical categories or MIC values between the AST of the cocci determined by the direct method and the current method was found for 32 (55%) of 58 isolates. The E-test indicated that the direct method yielded a correct susceptibility profile for 13 of the other 26 blood cultures. Therefore, 45 (77%) of 58 cultures showed a concordant/correct susceptibility profile for all antimicrobial agents. The overall error rate amounted to 1.9%; the majority (1.3%) being minor errors. Importantly, the results obtained by the direct method were 12-24 hours earlier available than those by the current method.
PMID: 19681952 [PubMed - as supplied by publisher]