Article

Antimicrobial susceptibility testing of cystic fibrosis and non-cystic fibrosis clinical isolates of Pseudomonas aeruginosa: a comparison of three methods.

CF Research Group, Menzies Research Institute, School of Medicine, University of Tasmania, Hobart, Australia.
British journal of biomedical science (Impact Factor: 0.83). 01/2011; 68(1):1-4.
Source: PubMed

ABSTRACT Pseudomonas aeruginosa is an important pathogen in humans, particularly in the context of nosocomial infection and infections of the cystic fibrosis (CF) lung. In order to provide clinicians with information about the likely effectiveness of specific antimicrobial treatment for P. aeruginosa infections, clinical laboratories employ in vitro antimicrobial susceptibility testing. Two commonly employed methods are the CLSI disc-diffusion and Etest methods. The purpose of this study is to compare the accuracy of susceptibility results generated by these two methods against agar dilution as the reference method. Susceptible or nonsusceptible (resistant and intermediate) results of the Etest and CLSI disc-diffusion methods are compared with CLSI agar dilution results for a large cohort of clinical cystic fibrosis (n = 71) and non-cystic fibrosis (n = 83) isolates using CLSI interpretive criteria. An unacceptable number of major and very major errors were observed for various antimicrobials tested against both CF and non-CF isolates when using the Etest and CLSI disc-diffusion methods. The potential for error in standard laboratory antimicrobial susceptibility testing should be considered by clinicians when being guided by the results of such tests in the prescription of antimicrobial agents for P. aeruginosa infection.

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    ABSTRACT: This study was carried out with the objective of determining the genomic variability of P. aeruginosa strains isolated from patients suffering from cystic fibrosis or from environmental cultures collected from different locations in the unit they admitted. A total of 57 clinical and environmental P. aeruginosa isolates were genotyped by enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR), and antimicrobial susceptibility testing was performed using the Clinical and Laboratory Standards Institute method. One predominant ERIC profile (type A) was identified in 46 strains (81% of all typed isolates) which was responsible for thirty-nine of 44 clinical isolates (89%) and 7 of 13 environmental isolates (54%). All clinical isolates were susceptible to piperacillin-tazobactam, ceftazidime and cefepime followed by ticarcillin, aztreonam, amikacin and tobramycin (96.5%). In our country CF patients are not segregated from other patients, and transmission of bacteria between these patients and other patients might occur in the wards via personal contact or contaminated environment. Future evaluation for policy of patient segregation is necessary and the elimination of contaminated sources and control of environmental spread and recurrent contamination risk is needed.
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