SUMMARY The API ZYM system of detection of enzymes has been applied to 81 bacteria belonging to several species. It was found to be easy to use and has produced results that may be useful in the identification of a variety of bacteria.Most of the methods used in clinical microbiology laboratories for the identification of bacteria require growing organisms and detect the end result of complex metabolic activities. An alternative is to use a single substrate and a heavy inoculum of organism that need not grow to detect specific enzymes. The Auxotab system for detecting esterases, lipases, peptidases, and other enzymes, described by Buissiere et al. (1967), makes use of this alternative approach. It has been modified and made commercially available as the API ZYM system (API Laboratory Products Ltd, Philpot House, Rayleigh, Essex) which makes it possible to detect the activity of enzymes on 19 substrates within four hours. This paper reports a preliminary assessment of the API ZYM system in the identification and typing of a selection of medically important bacteria.
Methods and materialsThe API ZYM system (Figure) consists of a plastic gallery of cupules, in the bottom of each of which is a fabric support carrying the substrates and buffer. These substrates detect the following enzymes: alkaline and acid phosphatases, butyrate esterase, caprylate esterase lipase, myristate lipase, leucine, valine and cystine aminopeptidases, trypsin, chymotrypsin, phosphoamidase, ot-galactosidase, f-galactosidase, fl-glucuronidase, ax-glucosidase, fl-glucosidase, ,B-glucosaminidase, (x-mannosidase, and cx-fucosidase.The organisms to be tested were grown on blood agar plates, and a suspension was made in peptone water to an opacity equivalent to that of a McFarland No. 5 standard. Some of the organisms "Requests for reprints should be addressed to IP Received for publication 25 August 1976 were ultrasonicated for 5 minutes at an amplitude of 22 )um in an ultrasonic disintegrator (MSE Mk 2 150 watts). During the process the bottle was placed in iced water. An API ZYM gallery was placed in its humidification chamber (to which distilled water had been added), and 0-04 ml volumes of bacterial suspension or ultrasonicate were placed in each cupule. After incubation at 37°C for 4 hours 0-02 ml of fresh colour reagent containing 20 mg Fast Blue BB (Sigma F0250) in 10 ml was added to each cupule, and the gallery was kept in the dark for 5 minutes and then exposed for 30 seconds under a 750-watt lamp to prevent non-specific yellowing of the colour reagent. The reactions were then graded 0-5, depending on the intensity of colour compared with representations on a colour chart.The strains of bacteria investigated were isolated in the
