The Influence of Seasonality and Antimicrobial Resistance Genes on Biofilm Formation in Hospital-Acquired Resistant Bacteria.

BACKGROUND

Hospital-acquired resistant infections (HARI) are difficult to manage due to limited treatment options and their ability to withstand stress conditions through biofilm production. HARI were defined as infections occurring at least 48 h after hospital admission. This work aimed to assess the distribution of HARI-associated bacterial species in north Israel and to investigate associations between biofilm formation and extended-spectrum β-lactamase(ESBL) genes, bacterial and patient characteristics, and hospitalization length, season and year.

METHODS

Methicillin-resistant Staphylococcus aureus (MRSA), multidrug-resistant (MDR) Pseudomonas aeruginosa (P. aeruginosa) and Acinetobacter baumannii (A. baumannii), ESBL-producing Escherichia coli (ESBL-E. coli), Klebsiella pneumoniae (ESBL-K. pneumoniae) and Proteus mirabilis (ESBL-P. mirabilis) were isolated from 569 blood, urine, wound and respiratory samples of hospitalized patients with HARI during 2020-2022 in north Israel. Enterobacterales were included if ESBL-positive (Vitek 2 and disc tests), and Acinetobacter and Pseudomonas if resistant to ≥ 3 antibiotic families. Biofilm-formation capacity was assessed by the crystalline violet method. ESBL genes were detected by real-time PCR. Data regarding season, time to infection, bacterial species, patient demographics, year, and hospital department, were collected from medical records.

RESULTS

ESBL-K. pneumoniae was the most prevalent (31.6%) bacteria. Strong biofilms were produced by 346 (60.8%), most of the strong biofilm producers were K. pneumoniae, accounting for 160 out of 346 strong-biofilm isolates (46.2%). blaCTX-M was the most commonly detected ESBL gene (87.7%). Most strains (61.2%) carried more than one ESBL gene. Hospitalization season had a notable impact on biofilm production, with a heightened risk of infection by robust biofilm producers during spring, summer and autumn compared to winter. Furthermore, the presence of blaSHV and blaTEM genes were significantly associated with enhanced biofilm production. Bacteria harboring all three ESBL genes exhibited the highest biofilm production capacities, compared to those carrying fewer than three.

CONCLUSIONS

Biofilm-production intensity differs across bacterial species and seasons and is influenced by the presence of ESBL genes.