Abstract:
Staphylococcus aureus is an important human pathogen
that is capable of causing a wide range of diseases, from relatively
mild skin infections to deep systemic infections such as
pneumonia. Identification and typing of S. aureus is currently
based on various genomic and phenotypic methods; however, these
methods are time-consuming, expensive and sometimes lack
accuracy. A total of 14 S. aureus isolates were previously
identified by conventional methods including multiple locus
sequence typing (MLST), SCCmec typing and spa typing. Our
purpose is to evaluate the use of Matrix Assisted Laser Desorption
Ionization Time of Flight (MALDI-TOF) for rapid identification
and analysis of these S. aureus isolates. Formic acid extraction was
used to extract proteins which were then subjected to MALDI-TOF
analysis. An identification profile for each isolate was created and
2 programs were developed for further analysis of the obtained
data. With this approach setting stringent parameters on
reproducibility of data, we were able to identify the masses of 5 peaks (4823, 6428, 6612, 8903, and 9644 m/z) that are common to
all S. aureus isolates. To determine whether these 5 peaks were
unique to S. aureus, the same procedure of protein extraction and
data analysis was applied on S. epidermidis and Escherichia coli.
Compared to the m/z list of S. aureus, 3 peaks were discovered to
be common in S. epidermidis but none in E. coli. Thus we were
able to identify 3 peaks unique for the genus Staphylococcus and 2
peaks unique for the species S. aureus. Also, our results suggest
that the program developed is valid and very powerful in analyzing
high-through put data obtained from MALDI analysis. Moreover,
MALDI-TOF MS has high potential to be used as a proteomic tool
for the identification of bacteria. Future work includes
identification of peaks specific at the strain level and Tandem-MS
of the unique peaks to determine their nature.
