When it rains it pours: An increased prevalence of intestinal carriage of vancomycin-resistant Enterococcus faecium related to higher use of oral vancomycin in a tertiary care Hungarian clinical centre during the years of the COVID-19 pandemic

Objectives: This study aims to investigate the association between oral vancomycin consumption and intestinal vancomycin-resistant Enterococcus carriage in the pre- and COVID era in the clinical centre of the University of Szeged, Hungary. Methods: This retrospective microbiological examination was carried out using electronically collected data, corresponding to the period between 1 January 2018 and 31 December 2022, at the Department of Medical Microbiology. Data included isolated species and the according antimicrobial susceptibility patterns. Annual consumption data for oral vancomycin consumption were exported from the database of the central pharmacy of the clinical centre. As a strain typing procedure, Fourier transform infrared spectroscopy analysis was used. Results: There was a significant increase in the number of faecal vancomycin-resistant Enterococcus isolates throughout the study. The prevalence increased significantly during the years of the pandemic. The use of orally administered vancomycin in the clinical centre increased significantly. A strong positive correlation existed between the two phenomena. Several strains with different resistance patterns spread in the clinical centre. Two of these occurred in greater numbers, differing in their high-level aminoglycoside resistance. However, the overall resistance of these strains was stagnating. FTIR analysis revealed that 59 of the 62 strains were also divided into 2 large clusters differing partially in their high-level aminoglycoside resistance. Conclusions: During the pandemic, intestinal VRE carriage among clinical centre patients increased significantly, linked to increased oral vancomycin use. Different strains spread, with aminoglycoside resistance being the primary distinction. This highlights the negative impact of the pandemic on VRE carriage.