Abstract
Objective: Automatic identification and antimicrobial susceptibility systems are frequently used to identify clinical isolates in hospitalized patients, but mistakes in these systems can lead to potentially devastating treatment failures for patients. Therefore, the ‘‘Centers for Disease Control and Prevention (CDC)’’ recommends confirming all Carbapenem-resistant and low-susceptibility isolates with a different method. The aim of this study is to compare the Carbapenem susceptibility results of isolates reported as Carbapenem-resistant Enterobacteriaceae according to the BD Phoenix 100 automated system with the E-test method. Materials and Methods: The study included 70 strains of Carbapenem-resistant Enterobacteriaceae members which were isolated and grown from several types of clinical samples in the Medical Microbiology Laboratory. Conventional methods (Gram stain, negative oxidase test) and the BD Phoenix 100 automated system were used to identify the isolates. The susceptibility of all strains to imipenem, ertapenem and meropenem was investigated by E-test method. Automated system results and E-test results were compared. Results: The frequency distribution of all isolated bacterial strains comprised K. pneumoniae in 56 (80%) of the samples included in the study. The automated system test results were correlated with the results of the E-test at a rate of 96.1 % for the imipenem-resistant strains, 84.3% for the meropenem-resistant strains, 84.1% for the ertapenem-resistant strains Conclusions: Automated systems are frequently used in microbiology laboratories to identify isolates. However, automated systems can show a high error rate against some antimicrobials. For this reason, comparing the results of automated system test results with tests such as E-test is very important to prevent both treatment failures and inappropriate antibiotic use that may occur on a patient basis.
Highlights
Enterobacteriaceae is a bacteria family containing a large number of genera and species, which are often isolated as infectious agents from humans [1]
Automated systems are frequently used in microbiology laboratories to identify isolates
Automated systems can show a high error rate against some antimicrobials. For this reason, comparing the results of automated system test results with tests such as E-test is very important to prevent both treatment failures and inappropriate antibiotic use that may occur on a patient basis
Summary
Enterobacteriaceae is a bacteria family containing a large number of genera and species, which are often isolated as infectious agents from humans [1]. The rates of antimicrobial resistance have significantly increased in hospitalized patients in recent years [3]. Carbapenem-hydrolyzing βlactamases (Carbapenemases) are the most potent, capable of hydrolyzing almost all β-lactams. Their worldwide spread among the members of the Enterobacteriaceae family creates a major concern [5]. Treatment options are limited and mortality rates are high in patients with infections, in which Carbapenem-resistant Enterobacteriaceae (CRE) are the causative agents [6]. Meropenem is more stable than imipenem, susceptibility panels, disc monitoring and storage conditions are required for both antimicrobials. The ‘‘Centers for Disease Control and Prevention (CDC)’’ recommends confirming all Carbapenem-resistant and low-susceptibility isolates with a different method [7].
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