| Abstrakt: |
ABSTRACTIdentification of Nocardiato the species level is useful for predicting antimicrobial susceptibility patterns and defining the pathogenicity and geographic distribution of these organisms. We sought to develop an identification method which was accurate, timely, and employed tests which would be readily available in most clinical laboratories. We evaluated the API 20C AUX yeast identification system as well as several biochemical tests and Kirby-Bauer susceptibility patterns for the identification of 75 isolates encompassing the 8 medically relevant Nocardiaspecies. There were few biochemical reactions that were sufficiently unique for species identification; of note, N. novawere positive for arylsulfatase, N. farcinicawere positive for opacification of Middlebrook 7H11 agar, and N. brasiliensisand N. pseudobrasiliensiswere the only species capable of liquefying gelatin. API 20C sugar assimilation patterns were unique for N. transvalensis, N. asteroidesIV, and N. brevicatena. There was overlap among the assimilation patterns for the other species. Species-specific patterns of susceptibility to gentamicin, tobramycin, amikacin, and erythromycin were obtained for N. nova, N. farcinica, and N. brevicatena, while there was overlap among the susceptibility patterns for the other isolates. No single method could identify all Nocardiaisolates to the species level; therefore, a combination of methods was necessary. An algorithm utilizing antibiotic susceptibility patterns, citrate utilization, acetamide utilization, and assimilation of inositol and adonitol accurately identified all isolates. The algorithm was expanded to include infrequent drug susceptibility patterns which have been reported in the literature but which were not seen in this study. |
