Summary auto-generated
Researchers developed a rapid diagnostic method for bacterial meningitis using gas chromatography-mass spectrometry with selected ion monitoring (GC-MS-SIM) to detect fatty acid markers in cerebrospinal fluid (CSF). They screened 20 candidate ions from bacterial cultures and identified ion m/e 268 (probably a C16:1 fatty acid) as a potential marker. Testing this marker on 135 clinical CSF specimens showed 88% sensitivity and 98% specificity for detecting common bacterial meningitis pathogens including Haemophilus influenzae, Streptococcus pneumoniae, and Escherichia coli. The method produced results within 2 hours and was more sensitive than conventional microscopy and culture. However, inconsistent results occurred with coagulase-negative staphylococci, Mycobacterium tuberculosis, Cryptococcus neoformans, and some other uncommon organisms. The authors conclude that chemical marker detection by GC-MS-SIM shows promise for rapid bacterial diagnosis but note that simpler detection methods would be needed for routine clinical practice.
Key findings
- Ion m/e 268 detected in cerebrospinal fluid with 88% sensitivity and 98% specificity for bacterial meningitis caused by common pathogens
- The GC-MS-SIM method produced diagnostic results within 2 hours and was more sensitive than conventional microscopy and bacterial culture
- Ion m/e 268 was unreliable for detecting mycobacterial, cryptococcal, staphylococcal, and salmonella infections
- The method successfully identified bacteria in three culture-negative but antigen-positive specimens, demonstrating superior detection capability
- Individual organisms produced characteristic ion profiles suggesting potential for rapid diagnosis to genus or species level using multiple-ion monitoring
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Abstract
A chemical marker of bacterial meningitis was sought by comparing derivatives of sterile cerebrospinal fluid (CSF) with cultures of organisms in spinal fluid and artificial media. The technique of gas chromatography-mass spectrometry with selected ion monitoring (GC-MS-SIM) was used, optimised for the analysis of fatty acids. Twenty candidate ions were screened, and an ion of mass: charge ratio (m/e) 268 was chosen for detection in clinical specimens. The origin of this marker is unknown, but it is probably the molecular ion of a C16:1 fatty acid. In 135 clinical specimens of CSF examined, the m/e 268 ion was found to be a useful marker for the common organisms that cause bacterial meningitis, giving a sensitivity of 88% and a specificity of 98%. The method was more rapid and more sensitive than conventional microscopy and culture, but CSF containing coagulase-negative staphylococci, Mycobacterium tuberculosis, Cryptococcus neoformans and some other uncommon pathogens gave inconsistent results. Many organisms produced characteristic ion profiles with multiple-ion monitoring, and this method of chemical analysis holds promise for the rapid diagnosis of bacterial infections to genus or species level.