Multidrug-resistant Pseudomonas aeruginosa in ICU patients and hospital surfaces: β-lactamase burden, biofilm formation and clonal spread

Pseudomonas aeruginosa is one of the leading agents of Healthcare-Associated Infections (HAIs), especially in Intensive Care Units (ICUs), where its intrinsic resistance, biofilm-forming ability, and acquisition of β-lactamase genes contribute to therapeutic failure and increased morbidity. Understanding the resistance mechanisms and clonal dynamics of this pathogen in clinical and hospital environments is essential for effective infection control. Overall, 30.5% of the isolates were classified as MDR, with higher non-susceptibility rates to imipenem (41.2%) and meropenem (35.6%). Moderate/strong biofilm formation was observed in 77.3% of the isolates. A high prevalence of β-lactamase genes was detected, particularly blaCTX-M (38.8%), blaTEM (29.1%), blaGES (13.9%), and blaSHV (4.1%), whereas carbapenemase genes were infrequent (blaVIM, blaKPC, blaIMP; 1.8%). The blaCTX-M gene was significantly associated with MDR profiles and resistance to cefepime and ceftazidime. PFGE identified 16 clonal groups among 28 isolates, indicating transmission among patients, hospital surfaces, and different hospitals. MLST revealed 16 sequence types, including four novel STs, with predominance of ST3079. A total of 216 P. aeruginosa isolates obtained from hospitalized patients and hospital surfaces in three public hospitals in Porto Velho, Western Amazon, Brazil, were analyzed. Antimicrobial susceptibility was determined according to CLSI guidelines. Biofilm formation was evaluated in 96-well microplates. β-lactamase and carbapenemase genes were detected by PCR. Genetic relatedness was investigated by PFGE and MLST in multidrug-resistant (MDR) or carbapenem-resistant isolates. P. aeruginosa from ICU patients and hospital surfaces showed high multidrug resistance, strong biofilm production, and widespread β-lactamase genes, particularly blaCTX-M, a key determinant of the MDR phenotype. Clonal dissemination across hospitals and sources highlights the need for strengthened infection control, continuous molecular surveillance, and antimicrobial stewardship.