The typing of Mycoplasma pneumoniae mainly relies on the detection of nucleic acid, which is limited by the use of a single gene target, complex operation procedures, and a lengthy assay time. Here, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) coupled to ClinProTools was used to discover MALDI-TOF MS biomarker peaks and to generate a classification model based on a genetic algorithm (GA) to differentiate between type 1 and type 2 M. pneumoniae isolates. Twenty-five M. pneumoniae strains were used to construct an analysis model, and 43 Mycoplasma strains were used for validation. For the GA typing model, the cross-validation values, which reflect the ability of the model to handle variability among the test spectra and the recognition capability value, which reflects the model's ability to correctly identify its component spectra, were all 100%. This model contained 7 biomarker peaks (m/z 3,318.8, 3,215.0, 5,091.8, 5,766.8, 6,337.1, 6,431.1, and 6,979.9) used to correctly identify 31 type 1 and 7 type 2 M. pneumoniae isolates from 43 Mycoplasma strains with a sensitivity and specificity of 100%. The strain distribution map and principle component analysis based on the GA classification model also clearly showed that the type 1 and type 2 M. pneumoniae isolates can be divided into two categories based on their peptide mass fingerprints. With the obvious advantages of being rapid, highly accurate, and highly sensitive and having a low cost and high throughput, MALDI-TOF MS ClinProTools is a powerful and reliable tool for M. pneumoniae typing.
Mycoplasma pneumoniae is one of the most common pathogens that cause respiratory tract infections (1). The genotyping of clinical isolates is an important means for understanding the epidemiology of M. pneumoniae outbreaks. The 170-kDa protein encoded by the p1 gene is an important adhesion and antigenic factor in M. pneumoniae and is densely clustered at its terminal structure (2-4). The p1 gene contains two previously described repetitive regions, one located within the 3= region (RepMP2/3) and another located within the 5= region (RepMP4). RepMP2/3 and RepMP4 elements are present in the M. pneumoniae genome (5). M. pneumoniae clinical isolates can be categorized as type 1 or type 2 according to the sequence variation of the p1 gene (6-10). At present, among the techniques for laboratory typing to gain understanding of the epidemiology of M. pneumoniae, the most popular is molecular typing based on the p1 gene (7, 9). All M. pneumoniae isolates are classified as type 1 or type 2 according to the RepMP4 and RepMP2/3 repetitive sequences within the p1 gene. However, the genotyping of M. pneumoniae isolates based on a single gene limits our understanding of the biological characteristics of M. pneumoniae. Thus, more rapid and convenient methods for the identification and typing of M. pneumoniae are needed to perfect and supplement the present techniques. Silver nanorod array surface-enhanced Raman spectroscopy was use to detect and...