The aim of this study was to compare a commercially available automated broth microdilution system (Merlin; Micronaut, Germany) with the standard agar dilution method for susceptibility testing of pulmonary isolates from cystic fibrosis patients. Accurate susceptibility testing of bacterial isolates from cystic fibrosis patients is known to pose problems. Although commercially available automated test systems could facilitate susceptibility testing of such isolates in routine diagnostics, these systems have not been recommended thus far. However, a pilot study recently indicated that the Merlin system, which is based on an endpoint measurement rather than on growth curves, might be applicable in the susceptibility testing of isolates from cystic fibrosis patients. In the present study, the Merlin system was further evaluated using an extended panel of nonmucoid and mucoid Pseudomonas aeruginosa isolates. The results showed that the MICs obtained with the Merlin system tended to be lower than those obtained with the agar dilution method, a finding that became increasingly apparent when mucoid Pseudomonas aeruginosa strains were tested. The correlation coefficients (r values) of the MIC results for all strains tested were between 0.6 and 0.8 for five of the seven antimicrobial agents, with r values exceeding 0.8 for only meropenem and ciprofloxacin. However, since the overall rate of serious discrepancies was within an acceptable range, the Merlin system appears to be applicable for routine clinical use in susceptibility testing of P. aeruginosa isolates from cystic fibrosis patients.
Since accurate antimicrobial susceptibility testing of bacterial cystic fibrosis isolates is known to be problematic and an optimal in vitro testing method has not yet been evaluated, the study presented here was conducted to compare the performance of the reference agar dilution method and broth microdilution with a commercially available automated susceptibility test system (Merlin; Micronaut, Germany). In this pilot study, the susceptibility of 70 clinical strains of Pseudomonas aeruginosa and Burkholderia cepacia-like organisms to nine antimicrobial agents was tested using these methods. Susceptibility results generated by broth microdilution (both automated and according to the National Committee for Clinical Laboratory Standards recommendations) were demonstrated to be of good reproducibility, and they compared favourably to the time- and material-consuming standard agar dilution reference method, especially after a prolonged incubation time (48 h).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.