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Updated: Jul 18, 2026
Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Detection of heterogeneous, intermediate-vancomycin-resistant Staphylococcus aureus (hVISA) using low-concentration
Aroonlug Lulitanond1, Aroonwadee Chanawong, Pipat Sribenjalux
1Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand. arolul@kku.ac.th
Abstract:
Heterogeneous, intermediate-vancomycin-resistant Staphylococcus aureus (hVISA) represents a threat of an incurable infection since the first report in 1997. The method used to detect hVISA isolates is a population analysis profile (PAP); however, it is impractical for routine laboratory analysis. We therefore tested a simple, reliable and inexpensive method for the detection of hVISA. Eighteen isolates of hVISA and 22 of vancomycin-sensitive S. aureus (VSSA) were included. The organisms were tested by the disk diffusion method, using 15-microg vancomycin disks on four different media: Mueller-Hinton agar (MHA), MHA plus 2% NaCI (MHAS), Brain Heart Infusion agar (BHA), and BHA plus 2% NaCl (BHAS). In addition, two different inoculum sizes, bacterial suspensions adjusted to 0.5 and 2.0 McFarland, were tested. The inhibition zone was read independently by three medical technologists after incubation at 37 degrees C for 24 and 48 hours. The use of MHAS with an inoculum size of 2.0 McFarland and 48-hour incubation period yielded the highest sensitivity (94.4%), specificity (81.8%), positive predictive value (80.9%), and negative predictive value (94.7%). The disk diffusion test with 15-microg vancomycin disk is simple and may be used as a screening method for the detection of hVISA.
Insights
A simple disk diffusion test offers a practical method for detecting heterogeneous vancomycin-resistant Staphylococcus aureus (hVISA). This approach provides high sensitivity and specificity, making it suitable for routine laboratory screening of hVISA infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) poses a significant challenge due to treatment difficulties.
- Current detection methods like population analysis profile (PAP) are not practical for routine diagnostics.
Purpose of the Study:
- To evaluate a simple, reliable, and inexpensive disk diffusion method for detecting hVISA isolates.
- To compare the efficacy of different media and inoculum sizes for hVISA detection.
Main Methods:
- Disk diffusion testing using 15-microg vancomycin disks on four media (MHA, MHAS, BHA, BHAS).
- Testing with two inoculum sizes (0.5 and 2.0 McFarland).
- Incubation for 24 and 48 hours, with zone inhibition read by three technologists.
Main Results:
- The optimal conditions involved Mueller-Hinton agar with 2% NaCl (MHAS), a 2.0 McFarland inoculum, and 48-hour incubation.
- These conditions achieved the highest sensitivity (94.4%), specificity (81.8%), positive predictive value (80.9%), and negative predictive value (94.7%).
Conclusions:
- The disk diffusion test with a 15-microg vancomycin disk is a simple and effective screening method for hVISA detection.
- This method can aid in the early identification of hVISA, facilitating appropriate patient management.
