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Updated: Aug 7, 2025
Integrated Photoacoustic Ophthalmoscopy and Spectral-domain Optical Coherence Tomography
Published on: January 15, 2013
Differentiating methicillin resistant and susceptible Staphylococcus aureus from ocular infections using
Robert H Edgar1, Anie-Pier Samson2, Regis P Kowalski3
1Swanson School of Engineering, Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States.
Introduction:
Antibiotic resistance in bacterial species constitutes a growing problem in the clinical management of infections. Not only does it limit therapeutic options, but application of ineffective antibiotics allows resistant species to progress prior to prescribing more effective treatment to patients. Methicillin resistance in Staphylococcus aureus is a major problem in clinical infections as it is the most common hospital acquired infection.
Methods:
We developed a photoacoustic flow cytometer using engineered bacteriophage as probes for rapid determination of methicillin resistance in Staphylococcus aureus with thirteen clinical samples obtained from keratitis patients. This method irradiates cells under flow with 532 nm laser light and selectively generates acoustic waves in labeled bacterial cells, thus enabling detection and enumeration of them. Staphylococcus aureus isolates were classified from culture isolation as either methicillin resistant or susceptible using cefoxitin disk diffusion testing. The photoacoustic method enumerates bacterial cells before and after treatment with antibiotics. Decreasing counts of bacteria after treatment indicate susceptible strains. We quantified the bacterial cells in the treated and untreated samples.
Results:
Using k-means clustering on the data, we achieved 100% concordance with the classification of Staphylococcus aureus resistance using culture.
Discussion:
Photoacoustics can be used to differentiate methicillin resistant and susceptible strains of bacteria from ocular infections. This method may be generalized to other bacterial species using appropriate bacteriophages and testing for resistance using other antibiotics.
Insights
A novel photoacoustic flow cytometry method rapidly determines methicillin resistance in Staphylococcus aureus. This technique shows 100% concordance with traditional culture methods, offering a faster diagnostic approach for bacterial infections.
Area of Science:
- Microbiology
- Biomedical Engineering
- Diagnostic Technology
Background:
- Antibiotic resistance in Staphylococcus aureus is a significant clinical challenge, complicating infection management.
- Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of hospital-acquired infections, necessitating rapid diagnostic tools.
- Current methods for determining antibiotic resistance can be time-consuming, delaying appropriate patient treatment.
Purpose of the Study:
- To develop and validate a rapid photoacoustic flow cytometry method for detecting methicillin resistance in Staphylococcus aureus.
- To assess the concordance of the photoacoustic method with standard culture-based antibiotic susceptibility testing.
- To evaluate the potential of this technology for clinical application in diagnosing bacterial infections.
Main Methods:
- Development of a photoacoustic flow cytometer utilizing engineered bacteriophages as specific probes.
- Irradiation of bacterial cells with a 532 nm laser to generate acoustic waves for detection and enumeration.
- Classification of Staphylococcus aureus isolates as methicillin-resistant or susceptible using cefoxitin disk diffusion and photoacoustic analysis before and after antibiotic treatment.
Main Results:
- The photoacoustic method successfully enumerated bacterial cells in treated and untreated samples.
- K-means clustering analysis of the photoacoustic data achieved 100% concordance with conventional culture-based classification of methicillin resistance.
- The study demonstrated the ability to differentiate methicillin-resistant and susceptible strains from clinical samples.
Conclusions:
- Photoacoustic flow cytometry is a viable method for rapid differentiation of methicillin-resistant and susceptible Staphylococcus aureus strains.
- This technology offers a promising alternative to traditional methods for diagnosing antibiotic resistance in bacterial infections.
- The photoacoustic approach may be adaptable for detecting resistance in other bacterial species and to various antibiotics.
