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Evaluation of 15 motility media and a direct microscopic method for detection of motility in enterococci
Kenneth Van Horn1, Clara Tóth, Reiko Kariyama
1Microbiology, Westchester Medical Center, and New York Medical College, Valhalla, New York 10595, USA. vanhornk@wcmc.com
Abstract:
Isolation of motile, vanC enterococci has yet to be a major infection control concern; however, rapid detection still is important. We evaluated 15 motility media from three manufacturers and a 2-h direct microscopic method for accurate detection of 89 enterococcal strains, including 72 vanC enterococcal strains. Resistance genes were confirmed by a multiplex PCR method with the vanC gene detected in all motile enterococci. Motility in the 72 vanC enterococci was detected at 30 degrees C within 72 h in BD Biosciences motility nitrate medium and in Remel motility B medium, motility B medium supplemented with methyl-alpha-D-glucopyranoside (investigational), motility S medium, motility test medium, and motility test medium with tetrazolium indicator. Motility was also observed for all vanC enterococci with the 2-h direct (30 degrees C incubation) microscopic detection method. All Enterococcus faecalis and Enterococcus faecium isolates were observed to be nonmotile in all media and by the direct microscopic method. Since differences between the various motility media tested were observed, the medium used for detection of enterococcal motility must be selected carefully.
Insights
Rapid detection of motile vanC enterococci is crucial. Specific motility media and a direct microscopic method accurately identified these strains, highlighting the need for careful medium selection in clinical settings.
Area of Science:
- Microbiology
- Infectious Diseases
- Clinical Diagnostics
Background:
- Motile vanC enterococci are an emerging concern in healthcare settings.
- Accurate and rapid detection methods for these pathogens are essential for infection control.
- Enterococcal infections, particularly those with vanC resistance, require timely identification.
Purpose of the Study:
- To evaluate the efficacy of various motility media and a direct microscopic method for detecting motile vanC enterococci.
- To compare the performance of 15 different motility media from three manufacturers.
- To assess the speed and accuracy of a 2-hour direct microscopic detection method.
Main Methods:
- Tested 89 enterococcal strains, including 72 vanC strains, using 15 motility media and a direct microscopic method.
- Confirmed vanC resistance genes using multiplex PCR.
- Incubated cultures at 30°C and observed motility within 72 hours.
Main Results:
- Motility was detected in 72 vanC enterococci using specific motility media (BD Biosciences motility nitrate, Remel motility B, supplemented motility B, motility S, motility test, and motility test with tetrazolium).
- A 2-hour direct microscopic method also successfully detected motility in vanC enterococci.
- All Enterococcus faecalis and Enterococcus faecium isolates tested were nonmotile across all methods.
Conclusions:
- The selection of appropriate motility media is critical for accurate enterococcal motility detection.
- Both specific motility media and a rapid direct microscopic method can effectively identify motile vanC enterococci.
- Non-motility was consistent for Enterococcus faecalis and Enterococcus faecium.