Abstract
BackgroundRapid and accurate identification of pathogens is of utmost importance for management of patients. Current identification relies on conventional phenotypic methods which are time consuming. Matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF MS) is based on proteomic profiling and allows for rapid identification of pathogens.ObjectiveWe compared MALDI-TOF MS against two commercial systems, MicroScan Walkaway and VITEK 2 MS.MethodsOver a three-month period from July 2013 to September 2013, a total of 227 bacteria and yeasts were collected from an academic microbiology laboratory (N = 121; 87 Gram-negatives, seven Gram-positives, 27 yeasts) and other laboratories (N = 106; 35 Gram-negatives, 34 Gram-positives, 37 yeasts). Sixty-five positive blood cultures were initially processed with Bruker Sepsityper kit for direct identification.ResultsFrom the 65 blood culture bottles, four grew more than one bacterial pathogen and MALDI-TOF MS identified only one isolate. The blood cultures yielded 21 Gram-negatives, 43 Gram-positives and one Candida. There were 21 Escherirchia coli isolates which were reported by the MALDI-TOF MS as E. coli/Shigella. Of the total 292 isolates, discrepant results were found for one bacterial and three yeast isolates. Discrepant results were resolved by testing with the API system with MALDI-TOF MS showing 100% correlation.ConclusionThe MALDI-TOF MS proved to be very useful for rapid and reliable identification of bacteria and yeasts directly from blood cultures and after culture of other specimens. The difference in time to identification was significant for all isolates. However, for positive blood cultures with minimal sample preparation time there was a massive difference in turn-around time with great appreciation by clinicians.
Highlights
IntroductionThe identification of microorganisms in patient specimens has historically been based on the detection of pathogen-specific phenotypic characteristics.[1]
In clinical microbiology laboratories, the identification of microorganisms in patient specimens has historically been based on the detection of pathogen-specific phenotypic characteristics.[1]These include microscopic and colony morphology features and biochemical phenotypes that can be detected with either manual or automated methods.[1]
A total of 227 isolates were evaluated over the three-month study period
Summary
The identification of microorganisms in patient specimens has historically been based on the detection of pathogen-specific phenotypic characteristics.[1] These include microscopic and colony morphology features and biochemical phenotypes that can be detected with either manual or automated methods.[1] The most commonly used automated systems in South Africa are the VITEK 2 MS and MicroScan Walkaway systems. These systems allow for the identification of most bacterial isolates with great accuracy, they are costly and time consuming. Matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF MS) is based on proteomic profiling and allows for rapid identification of pathogens
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