Increased sensitivity of bacterial detection in cerebrospinal fluid by fluorescent staining on low-fluorescence membrane filters

Abstract

A membrane-filter-based, fluorescent Gram stain method for bacterial detection in cerebrospinal fluid samples was developed and evaluated as a rapid, sensitive alternative to standard Gram stain protocols. A recently developed, modified version of the aluminium oxide membrane Anopore with low-fluorescence optical properties showed superior performance in this application. Other aspects of the fluorescent Gram stain system that were evaluated include membrane filter selection, strategies to reduce fluorescence fading and the effect of patient blood cells on bacterial detection in the fluorescently stained cerebrospinal fluid samples. The combination of the membrane filter's bacteria-concentrating ability and absolute retention along with high-contrast, fluorescent Gram discriminating dyes enabled rapid bacterial detection and Gram discrimination, with a 1-1.5 order of magnitude increase in the bacterial concentration limit of detection.