Evaluation of E-Test for determination of antimicrobial MICs for Pseudomonas aeruginosa isolates from cystic fibrosis patients

Abstract

We determined the E-Test and National Committee for Clinical Laboratory Standards standardized agar dilution MICs of ceftazidime, ciprofloxacin, piperacillin, and tobramycin for Pseudomonas aeruginosa during tests of 100 rough and mucoid P. aeruginosa isolates from cystic fibrosis patients. The levels of agreement (؎1 log 2 dilution) between quantitative E-Test and agar dilution MIC results were 80, 97, 73, and 89% for ceftazidime, ciprofloxacin, piperacillin, and tobramycin, respectively. Comparison of the results after converting the MIC data to qualitative categories (susceptible, intermediate, and resistant) yielded levels of agreement of 84, 96, 88, and 93% for the same agents, respectively. Of the 39 qualitative discrepancies, 36 were minor and 3 were very major. We conclude that use of the E-Test is easier and more practical than use of the agar dilution method for most laboratories and that the E-Test furnishes results which are at least as accurate as those obtained by the agar dilution method. However, the higher cost of the E-Test method would likely discourage most laboratories from selecting it over disk diffusion for routine antimicrobial susceptibility testing of P. aeruginosa isolates from cystic fibrosis patients.

Evaluation of the E Test for Antimicrobial Susceptibility Testing ofPseudomonas aeruginosaIsolates from Patients with Long-Term Bladder Catheterization

“…No very major errors were found between the E test and the NCCLS reference agar methods. The accuracy of the E-test MICs for P. aeruginosa that we found is in agreement with the findings of previous studies (8,10,16). Our data indicate that E-test MICs were within 1 log 2 dilution of reference agar dilution results in 88% of instances for the nine antimicrobial agents tested.…”

Changes in toxin production of environmental Pseudomonas aeruginosa isolates exposed to sub-inhibitory concentrations of three common antibiotics

“…Minimum inhibitory concentrations (MIC) for ciprofloxacin, tobramycin and meropenem were obtained using E-test strip diffusion and micro broth dilution methods. E-test plastic strips (Liofilchem, Italy) that have a predefined gradient of antibiotic concentration [25]. A 0.5 McFarland standard suspension was inoculated onto Mueller-Hinton agar plates.…”

Tratamiento antimicrobiano frente a la colonización pulmonar por Pseudomonas aeruginosa en el paciente con fibrosis quística

“…Sin embargo, no todos los sistemas automáticos comerciales que utilizan la técnica de microdilución han demostrado su idoneidad 22,[64][65][66] . Por el contrario, sí se ha validado el sistema Epsilon-test (E-test) para el estudio de la sensibilidad de P. aeruginosa de pacientes con FQ 67 . Recientemente se ha constatado la dificultad añadida que plantea el estudio de la sensibilidad a los antimicrobianos en las cepas de P. aeruginosa hipermutadoras 68 .…”