Strain-level Staphylococcus differentiation by CeO2-metal oxide laser ionization mass spectrometry fatty acid profiling.
BACKGROUND
The Staphylococcus genus is composed of 44 species, with S. aureus being the most pathogenic. Isolates of S. aureus are generally susceptible to β-lactam antibiotics, but extensive use of this class of drugs has led to increasing emergence of resistant strains. Increased occurrence of coagulase-negative staphylococci as well as S. aureus infections, some with resistance to multiple classes of antibiotics, has driven the necessity for innovative options for treatment and infection control. Despite these increasing needs, current methods still only possess species-level capabilities and require secondary testing to determine antibiotic resistance. This study describes the use of metal oxide laser ionization mass spectrometry fatty acid (FA) profiling as a rapid, simultaneous Staphylococcus identification and antibiotic resistance determination method.


RESULTS
Principal component analysis was used to classify 50 Staphyloccocus isolates. Leave-one-spectrum-out cross-validation indicated 100 % correct assignment at the species and strain level. Fuzzy rule building expert system classification and self-optimizing partial least squares discriminant analysis, with more rigorous evaluations, also consistently achieved greater than 94 and 84 % accuracy, respectively. Preliminary analysis differentiating MRSA from MSSA demonstrated the feasibility of simultaneous determination of strain identification and antibiotic resistance.


CONCLUSIONS
The utility of CeO2-MOLI MS FA profiling coupled with multivariate statistical analysis for performing strain-level differentiation of various Staphylococcus species proved to be a fast and reliable tool for identification. The simultaneous strain-level detection and antibiotic resistance determination achieved with this method should greatly improve outcomes and reduce clinical costs for therapeutic management and infection control.
Department of Chemistry, Colorado School of Mines, Golden, CO, 80401, USA.
Nicholas R
NR
Saichek
Department of Chemistry, Colorado School of Mines, Golden, CO, 80401, USA.
Christopher R
CR
Cox
Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul, 136-791, Republic of Korea.
Seungki
S
Kim
Center for Intelligent Chemical Instrumentation, Department of Chemistry, Clippinger Laboratories, Ohio University, Athens, OH, 45701, USA.
Peter B
PB
Harrington
Department of Chemistry, Colorado School of Mines, Golden, CO, 80401, USA.
Nicholas R
NR
Stambach
Department of Chemistry, Colorado School of Mines, Golden, CO, 80401, USA. kvoorhee@mines.edu.
Kent J
KJ
Voorhees
D002563:Cerium / Q000494:pharmacology*; D005227:Fatty Acids / Q000378:metabolism*; D006801:Humans; D055432:Metabolomics / Q000379:methods; D010802:Phylogeny; D025341:Principal Component Analysis; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013203:Staphylococcal Infections / Q000382:microbiology; D013210:Staphylococcus / Q000145:classification* / Q000302:isolation & purification
D005227:Fatty Acids; D002563:Cerium; C030583:ceric oxide
Fatty acids; MALDI–MS; MOLI MS; MRSA; Staphylococcus