# Associations between antibiotic consumption intensity and extended-spectrum cephalosporin resistance in nursing homes: a retrospective ecological study

## TL;DR

This study explores how antibiotic use in nursing homes relates to resistance in certain bacteria, finding limited overall links but some specific associations.

## Contribution

The study provides new insights into antibiotic consumption and resistance in nursing homes using ecological data from Switzerland.

## Key findings

- No strong overall link was found between antibiotic consumption and resistance rates.
- Cephalosporin and carbapenem use showed modest associations with resistance in some bacteria.
- The findings suggest a need for better surveillance and resident-level data in nursing homes.

## Abstract

Studies relating the usage of antibiotics with extended-spectrum cephalosporin resistance (ESC-R) rates from clinical isolates in nursing homes (NHs) are rare. We investigated associations between the intensity of NH-level antibiotic consumption (ABC) and the frequency of ESC-R expressing urinary Escherichia coli, Klebsiella spp. and Proteus spp. isolates from NH residents.

We used retrospective data on ABC and ESC-R counts aggregated by NH and year between 2017 and 2022 from NHs of canton Vaud in Switzerland. Negative binomial regression was used to relate ABC intensity, expressed as DDDs per 1000 resident days, with counts of ESC-R expressing bacteria.

Fifty-four NHs were included cumulatively accounting for 6601 urinary isolates, of which 5028 E. coli, 999 Klebsiella spp. and 574 Proteus spp. Among these, the 6-year ESC-R cumulative incidence was 10.3% (E. coli 12.6%, Klebsiella spp. 3.8% and Proteus spp. 1.2%). Median annual overall ABC varied between 31.3 and 44.2 DDDs per 1000 resident days. There was no association between overall ABC, most antibiotic categories and ESC-R cumulative incidence. The consumption of cephalosporins [adjusted incidence rate ratio (aIRR): 1.023, 95% CI: 1–1.047] and carbapenems (aIRR: 1.542, 95% CI: 1.018–2.336) was independently associated with increased incidence.

No association was found between overall ABC and ESC-R rates. Cephalosporin consumption showed a modest association, while for carbapenems this could reflect therapeutic use. These findings highlight the need for enhanced surveillance and resident-level data to better understand antibiotic resistance drivers in this setting.