Distinguishing Clinical <i>Enterococcus faecium</i> Strains and Resistance to Vancomycin Using a Simple In-House Screening Test

• Published in: Antibiotics
• Main Authors: Natkamon Saenhom, Parichart Boueroy, Peechanika Chopjitt, Rujirat Hatrongjit, Anusak Kerdsin
• Format: Article
• Language: English
• Published: MDPI AG 2022-02-01
• Subjects: Enterococci; <i>Enterococcus faecium</i>; screening test; vancomycin
• Online Access: https://www.mdpi.com/2079-6382/11/3/286

Vancomycin-resistant enterococci (VRE) are a major concern as microorganisms with antimicrobial resistance and as a public health threat contributing significantly to morbidity, mortality, and socio-economic costs. Among VREs, vancomycin-resistant <i>Enterococcus faecium</i> (VREfm) is frequently isolated and is resistant to many antibiotics used to treat patients with hospital-acquired infection. Accurate and rapid detection of VREfm results in effective antimicrobial therapy, immediate patient isolation, dissemination control, and appropriate disinfection measures. An in-house VREfm screening broth was developed and compared to the broth microdilution method and multiplex polymerase chain reaction for the detection of 105 enterococci, including 81 VRE isolates (61 <i>E. faecium</i>, 5 <i>E. faecalis</i>, 10 <i>E. gallinarum</i>, and 5 <i>E. casseliflavus</i>). Verification of this screening broth on 61 VREfm, 20 other VRE, and 24 non-VRE revealed greater validity for VREfm detection. The accuracy of this broth was 100% in distinguishing <i>E. faecium</i> from other enterococcal species. Our test revealed 93.3% accuracy, 97.5% sensitivity, and 79.2% specificity compared with broth microdilution and PCR detecting <i>van</i> genes. The kappa statistic to test interrater reliability was 0.8, revealing substantial agreement for this screening test to the broth microdilution method. In addition, the in-house VREfm screening broth produced rapid positivity after at least 8 h of incubation. Application of this assay to screen VREfm should be useful in clinical laboratories and hospital infection control units.