Vancomycin-resistant Enterococcus faecium in a Veterans Affairs Medical Center: association with antibiotic usage

Area of Science:

• Infectious Diseases
• Hospital Epidemiology
• Antimicrobial Stewardship

Background:

• Vancomycin-resistant Enterococcus faecium (VREF) infections are a growing concern, often linked to individual antibiotic use.
• Previous studies focused on individual patient antibiotic exposure, necessitating an examination of aggregate usage patterns.

Purpose of the Study:

• To investigate the association between aggregate antibiotic usage on nursing units and the incidence of VREF infections.
• To determine if hospital-wide antibiotic usage metrics correlate with VREF colonization and infection rates.

Main Methods:

• A retrospective correlation study was conducted using antibiotic usage data and VREF infection rates from a Veterans Affairs Medical Center.
• An Average Usage Ratio (AUR) was calculated for each nursing unit to quantify aggregate antibiotic consumption relative to hospital-wide use.
• Univariate and multivariate regression analyses correlated AUR with VREF incidence, controlling for unit characteristics.

Main Results:

• A strong positive correlation was observed between the Average Usage Ratio (AUR) and VREF recovery on nursing units.
• While univariate analysis showed associations for all tested antibiotics, only clindamycin remained significant in multivariate models due to inter-antibiotic usage correlations.
• Intensive care, acute care, and smaller units had higher VREF infection rates compared to subacute or larger units.

Conclusions:

• Higher aggregate antibiotic use on nursing units is significantly associated with an increased incidence of VREF infections.
• Antibiotic usage ratios offer a practical method for assessing the link between antibiotic consumption and nosocomial infections.
• Findings underscore the importance of antimicrobial stewardship at the unit level to mitigate VREF spread.