A Simple and Rapid Low-Cost Procedure for Detection of Vancomycin-Resistance Genes in Enterococci Reveals an Outbreak of Vancomycin-Variable Enterococcus faecium

Abstract

The detection of resistance to vancomycin in enterococci cultured from patients is important for the treatment of individual patients and for the prevention of hospital transmission. Phenotypic antimicrobial resistance tests may fail to detect potential vancomycin-resistant enterococci. We have developed and tested a PCR based procedure for routine screening for vancomycin-resistance genes in clinical samples with enterococci. Primary cultures from diagnostic samples reported with growth of Enterococcus faecium or E. facalis were tested for vanA and vanB genes by real-time PCR without the isolation of specific bacteria. Up to ten samples were pooled and tested in each real-time PCR reaction, with subsequent individual testing of cultures from positive pools. In a one-month test period in 2017 vanA gene was detected in one out of 340 urine samples with vancomycin-susceptible enterococci reported from diagnostic culture. A second test period in 2018 included 357 urine samples, and vanA gene was detected in samples from eight patients. Subsequently, all urine samples reported with growth of E. faecium during a period of one year were tested. Fifty-eight individuals were identified with enterococci, carrying the vanA gene not previously detected. Routine molecular testing of primary culture material from patient samples may improve the detection of hospitalized patients carrying E. faecium with resistance genes to vancomycin.

Vancomycin Resistance in Enterococcus and Staphylococcus aureus

“…More recently, vanA - or vanB -carrying enterococci [ 449 ] which appear vancomycin-susceptible in traditional phenotypic susceptibility tests [ 450 ], but can revert to a vancomycin-resistant phenotype upon vancomycin treatment [ 451 , 452 ] were reported for the first time in 2011 [ 453 ]. The ability of these strains, termed vancomycin-variable enterococci (VVE), to evade diagnostic tests and switch phenotypes during antibiotic therapy [ 452 ] is thought to be due to major deletions in the Tn 1546 vanA operon [ 453 ] and/or inducible or constitutive vanHAX expression [ 454 ] which significantly compromises treatment success [ 452 ].…”

“…Therefore, it is likely that current epidemiological estimates of VVE, particularly in developing countries, would be below its actual prevalence value. To combat this, molecular-based testing methods such as PCR are required [ 450 ], but the facilities and apparatus for these techniques may be limited in low- and middle-income regions.…”

Evaluation of bactericidal effects of silver hydrosol nanotherapeutics against Enterococcus faecium 1449 drug resistant biofilms

“…As a major pathogen responsible for nosocomial infections, E. faecium isolates have often been found in surgical wound and urinary tract infections ( Huang et al., 2021 ; Strobel et al., 2022 ). Epidemiological investigations have found that VRE caused hospital outbreaks in various occasions ( Szakacs et al., 2014 ; Sivertsen et al., 2016 ; Hammerum et al., 2019 ; Abdullah et al., 2022 ), while E. faecium with dual resistance to linezolid and vancomycin was involved in the E. faecium outbreak in Reunion Island in 2019 ( Kamus et al., 2022 ). In terms of specific MDR, antibiotics such as cephalosporins, macrolides and semi-synthetic penicillin-like beta-lactams demonstrate prominent levels of resistance ( Guirao et al., 2009 ; Kristich et al., 2014 ; Georges et al., 2022 ).…”