Author(s): Joyanes P, del Carmen Conejo M, MartnezMartnez L, Perea EJ
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Abstract VITEK 2 is a new automatic system for the identification and susceptibility testing of the most clinically important bacteria. In the present study 198 clinical isolates, including Pseudomonas aeruginosa (n = 146), Acinetobacter baumannii (n = 25), and Stenotrophomonas maltophilia (n = 27) were evaluated. Reference susceptibility testing of cefepime, cefotaxime, ceftazidime, ciprofloxacin, gentamicin, imipenem, meropenem, piperacillin, tobramycin, levofloxacin (only for P. aeruginosa), co-trimoxazole (only for S. maltophilia), and ampicillin-sulbactam and tetracycline (only for A. baumannii) was performed by microdilution (NCCLS guidelines). The VITEK 2 system correctly identified 91.6, 100, and 76\% of P. aeruginosa, S. maltophilia, and A. baumannii isolates, respectively, within 3 h. The respective percentages of essential agreement (to within 1 twofold dilution) for P. aeruginosa and A. baumannii were 89.0 and 88.0\% (cefepime), 91.1 and 100\% (cefotaxime), 95.2 and 96.0\% (ceftazidime), 98.6 and 100\% (ciprofloxacin), 88.4 and 100\% (gentamicin), 87.0 and 92.0\% (imipenem), 85.0 and 88.0\% (meropenem), 84.2 and 96.0\% (piperacillin), and 97.3 and 80\% (tobramycin). The essential agreement for levofloxacin against P. aeruginosa was 86.3\%. The percentages of essential agreement for ampicillin-sulbactam and tetracycline against A. baumannii were 88.0 and 100\%, respectively. Very major errors for P. aeruginosa (resistant by the reference method, susceptible with the VITEK 2 system [resistant to susceptible]) were noted for cefepime (0.7\%), cefotaxime (0.7\%), gentamicin (0.7\%), imipenem (1.4\%), levofloxacin (2.7\%), and piperacillin (2.7\%) and, for one strain of A. baumannii, for imipenem. Major errors (susceptible to resistant) were noted only for P. aeruginosa and cefepime (2.0\%), ceftazidime (0.7\%), and piperacillin (3.4\%). Minor errors ranged from 0.0\% for piperacillin to 22.6\% for cefotaxime against P. aeruginosa and from 0.0\% for piperacillin and ciprofloxacin to 20.0\% for cefepime against A. baumannii. The VITEK 2 system provided co-trimoxazole MICs only for S. maltophilia; no very major or major errors were obtained for co-trimoxazole against this species. It is concluded that the VITEK 2 system allows the rapid identification of S. maltophilia and most P. aeruginosa and A. baumannii isolates. The VITEK 2 system can perform reliable susceptibility testing of many of the antimicrobial agents used against P. aeruginosa and A. baumannii. It would be desirable if new versions of the VITEK 2 software were able to determine MICs and the corresponding clinical categories of agents active against S. maltophilia.
This article was published in J Clin Microbiol
and referenced in Pharmaceutica Analytica Acta