The COVID-19 pandemic has impacted bacterial resistance, especially among bacteria prioritized by the World Health Organization. The objective is to describe the incidence density (ID) of multidrug-resistant bacteria (MDRB) between 2019 and 2025 in a high-complexity private hospital.

Cross-sectional study based on data from positive clinical cultures for MDRB between January 2019 and May 2025 identified by the Infection Control Service. Newly identified nosocomial MDRB isolates from any clinical culture were considered. IDs were determined as the number of cultures per 1,000 patient-days for carbapenem-resistant Enterobacterales (producing serine carbapenemase [SBL], metallo-carbapenemase [MBL], or both), carbapenem-resistant Acinetobacter baumannii (CRAB), carbapenem-resistant Pseudomonas aeruginosa (CRPA), oxacillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus faecium (VRE). Microorganisms were identified by MALDI-TOF, carbapenem, oxacillin, and vancomycin resistance were assessed by disk diffusion, and carbapenemases were confirmed by phenotypic tests (Blue Carba Plus).

Variations were observed among the pre-pandemic (2019), pandemic (2020–2021), and post-pandemic (2022–2025) periods. SBL producing Enterobacterales showed an increase in ID from 0.43 (n = 57; 4.75/month) in 2019 to 0.91 (n = 228; 9.5/month) in 2020–2021, decreasing to 0.58 (n = 268; 6.5/month) from 2022 onward. MBL-producing strains also increased, from 0.05 (n = 7; 0.6/month) in 2019 to 0.33 (n = 82; 3.4/month) in 2020–2021, remaining high thereafter (ID 0.39; n = 183; 4.5/month). Similarly, the ID of carbapenemase-producing Enterobacterales rose from 0.24 (n = 64; 5.3/month) in 2019 to 0.62 (n = 310; 12.9/month) in 2020–2021, stabilizing at 0.46 (n = 521; 12.7/month) since 2022. CRAB increased from 0.08 (n = 10; 0.8/month) to 0.66 (n = 165; 6.9/month) during the pandemic, dropping to 0.33 (n = 152; 3.7/month) after. CRPA resistance followed a similar pattern: 0.27 (n = 36; 3/month) in 2019, 0.47 (n = 118; 4.9/month) in 2020–2021, and 0.38 (n = 174; 4.2/month) from 2022 onward. MRSA and VRE rates remained stable across the three periods.

The COVID-19 pandemic impacted the increase in ID of MDRB, particularly in carbapenemase-producing Enterobacterales and CRAB, which remain at elevated levels compared with 2019, even in the years following the pandemic.