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Evaluation of the Four-Hour Micro-ID Technique for Direct Identification of Oxidase-Negative, Gram-Negative Rods from Blood Cultures

1980; American Society for Microbiology; Volume: 12; Issue: 4 Linguagem: Inglês

10.1128/jcm.12.4.533-537.1980

1098-660X

Peter C. Appelbaum, Suzanne F. Schick, James A. Kellogg,

Vibrio bacteria research studies

A 4-h Micro-ID technique for direct identification of oxidase-negative gram-negative rods from positive blood cultures was compared to subculture and species identification of single colonies by API 20E and Micro-ID, using standardized inocula. A total of 127 patients (220 positive cultures) were studied. Isolates included 96 Escherichia coli , 46 Klebsiella pneumoniae , 7 Klebsiella oxytoca , 8 Enterobacter aerogenes , 17 Enterobacter cloacae , 19 Serratia marcescens , 2 Serratia liquefaciens , 8 Proteus mirabilis , 1 Salmonella species, 1 Morganella morganii , 6 Haemophilus influenzae , 2 Haemophilus parainfluenzae , 3 Bacteroides fragilis , 3 Acinetobacter calcoaceticus biotype anitratus , and 1 Pseudomonas maltophilia . In 90% of the cultures, identification by Micro-ID was identical to that obtained after subculture; if the 15 non-enterobacterial isolates were excluded, the corresponding figure was 96.6%. Enterobacteria identified incorrectly by direct Micro-ID were three S. marcescens (two identified as S. liquefaciens , one as Hafnia alvei ), two S. liquefaciens (both identified as E. cloacae ), and two K. pneumoniae (one identified as Klebsiella ozaenae , the other as Serratia rubidaea ). None of the 15 non-enterobacterial cultures were correctly identified by Micro-ID (non-identifiable, or classified as Providencia/Yersinia/Klebsiella species). Although biochemical discrepancies between direct and final Micro-ID tests occurred in 41% of the enterobacterial cultures, this did not seriously interfere with identification. Direct species identification of Enterobacteriaceae from blood cultures by direct Micro-ID is accurate and easily performed and identified organisms within 4 h compared to at least 24 h by most other methods; the direct Micro-ID technique would be rendered even more valuable by the additional capability of identifying non-enterobacterial gram-negative isolates.