Detection of Pseudomonas cytochrome oxidase and esterase in blood culture broths

: Search for cytochrome-oxidase was performed directly on blood culture broths without prior isolation of the pathogen on agar, using paper disks impregnated with "oxidase" reagent and the Api Z strip which enables additional detection of esterases. Both these tests are indicative of the presence of Pseudomonas. False-positive results were recorded in only 0.65% of the 167 strains of Enterobacteria studies. The 38 strains of Pseudomonas aeruginosa gave 5.26% false-negative results; 88.6% of Pseudomonas strains were esterase-positive. Simultaneous search for both these enzymes thus allows for identification and antibiotic sensitivity testing before agar isolation.