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Comparison of inoculation methods for testing enterococci by using vancomycin screening agar
J H Jorgensen1, M L McElmeel, C W Trippy
1Department of Pathology, University of Texas, Health Science Center, San Antonto 78284-7750, USA.
Abstract:
One hundred four recent clinical isolates of Enterococcus species were screened for vancomycin resistance by using inocula of 10(5) or 10(6) CFU dispensed by pipet and by use of a cotton swab dipped in a 0.5 McFarland standard organism suspension applied to the surface of brain heart infusion agar containing 6 micrograms of vancomycin per ml. The three inoculation methods were equivalent in the detection of nonsusceptible isolates. The use of swab inoculation was convenient and less costly than the use of micropipets.
Insights
Detecting vancomycin resistance in Enterococcus species is crucial. Swab inoculation proved as effective as pipetting for identifying resistant strains, offering a convenient and cost-effective alternative for clinical laboratories.
Area of Science:
- Clinical Microbiology
- Antimicrobial Resistance
- Infectious Diseases
Background:
- Enterococcus species are significant nosocomial pathogens.
- Vancomycin resistance in Enterococcus is a growing public health concern.
- Accurate and efficient detection methods are essential for patient management.
Purpose of the Study:
- To evaluate the efficacy of different inoculation methods for detecting vancomycin resistance in Enterococcus.
- To compare the convenience and cost-effectiveness of swab inoculation versus pipetting methods.
Main Methods:
- Screened 104 clinical Enterococcus isolates for vancomycin resistance.
- Utilized three inoculation techniques: pipetting (10^5 or 10^6 CFU) and cotton swab (0.5 McFarland standard).
- All methods used brain heart infusion agar supplemented with 6 µg/mL vancomycin.
Main Results:
- All three inoculation methods demonstrated equivalent performance in detecting vancomycin-nonsusceptible Enterococcus isolates.
- Swab inoculation was identified as a convenient and less costly method compared to micropipetting.
Conclusions:
- Swab inoculation is a viable and practical alternative for routine vancomycin resistance screening of Enterococcus in clinical settings.
- This method supports efficient and economical antimicrobial susceptibility testing.