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Updated: May 11, 2026
Peptide and Protein Quantification Using Automated Immuno-MALDI (iMALDI)
Published on: August 18, 2017
Quantitative analysis of autoinducing peptide I (AIP-I) from Staphylococcus aureus cultures using ultrahigh
Hiyas A Junio1, Daniel A Todd, Keivan A Ettefagh
1Department of Chemistry/Biochemistry, The University of North Carolina Greensboro, 435 Sullivan Bldg, Greensboro, NC 27402, USA.
Abstract:
Staphylococcus aureus infections acquired in hospitals now cause more deaths per annum in the US than does HIV/AIDS. Perhaps even more alarming is the rise in community associated methicillin-resistant S. aureus (CA-MRSA) infections, which have spread out of hospital settings and are infecting otherwise healthy individuals. The mechanism of enhanced pathogenesis in CA-MRSA remains unclear, but it has been postulated that high activity in the agr quorum-sensing system could be a contributing factor. The purpose of this study was to develop a quantitative method for analysis of autoinducing peptide I (AIP-I), the activating signal for the agr system in S. aureus. An effective method was developed using ultrahigh performance liquid chromatography (UHPLC) coupled to electrospray ionization mass spectrometry with an LTQ Orbitrap mass spectrometer. Relying on the exceptional resolving power and mass accuracy of this instrument configuration, it was possible to quantify AIP-I directly from the complex growth media of S. aureus cultures with a limit of detection (LOD) of 0.25μM and a linear dynamic range of 2.6 to 63μM. The method was then employed to monitor time-dependent production of AIP-I by S. aureus cultures, and it was observed that AIP-I production reached a maximum and leveled off after approximately 16h. Finally, it was determined that virulence of S. aureus was correlated with AIP-I production in some (but not all) strains analyzed.
Insights
A new method quantifies autoinducing peptide I (AIP-I) in Staphylococcus aureus, a key signal in infections. This advance helps understand how CA-MRSA (community-associated methicillin-resistant S. aureus) becomes more virulent.
Area of Science:
- Microbiology
- Infectious Diseases
- Analytical Chemistry
Background:
- Hospital-acquired Staphylococcus aureus infections cause significant mortality in the US.
- The increasing prevalence of community-associated methicillin-resistant S. aureus (CA-MRSA) poses a growing public health threat.
- The agr quorum-sensing system's high activity is a potential factor in CA-MRSA pathogenesis.
Purpose of the Study:
- To develop a quantitative method for analyzing autoinducing peptide I (AIP-I), the S. aureus agr system's activating signal.
- To investigate the role of AIP-I in CA-MRSA virulence.
Main Methods:
- Ultrahigh performance liquid chromatography (UHPLC) coupled with electrospray ionization mass spectrometry (LTQ Orbitrap).
- Direct quantification of AIP-I from complex S. aureus growth media.
- Analysis of time-dependent AIP-I production and correlation with strain virulence.
Main Results:
- A sensitive method for AIP-I quantification was established with a limit of detection (LOD) of 0.25μM and a linear dynamic range of 2.6 to 63μM.
- AIP-I production in S. aureus cultures peaked around 16 hours.
- A correlation between S. aureus virulence and AIP-I production was observed in certain strains.
Conclusions:
- The developed UHPLC-MS method enables precise quantification of AIP-I in S. aureus cultures.
- Understanding AIP-I dynamics provides insights into the agr system's role in S. aureus pathogenesis.
- Further research is needed to fully elucidate the link between AIP-I and virulence across all S. aureus strains.
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