Oral cavity colonization by Pseudomonas aeruginosa in patients admitted in the intensive care units (ICUs)

Patients admitted in the Intensive Care Units (ICUs) often experience various oral health issues during their hospitalization, which can lead to a shift in their oral flora from Gram-positive to pathogenic Gram-negative bacteria, including Pseudomonas aeruginosa. Aim: This study aimed to identify the colonization of P. aeruginosa in the oral cavity of ICU patients, as well as to assess its antimicrobial susceptibility profile, phenotypic resistance mechanisms, and biofilm-forming capacity. Methods: Oral cavity samples were collected from patients in ICUs across three public hospitals in Porto Velho, Rondônia, Brazil. Antimicrobial susceptibility testing was performed using the disk diffusion method, phenotypic research on resistance determinants was conducted using a disk method with and without the addition of enzymatic inhibitors, and biofilm formation was assessed by measuring absorbance in microplates. Results: A total of 114 oral cavity samples were obtained, with 28% showing colonization by P. aeruginosa. The antimicrobial susceptibility profile revealed that 93.7% of the isolates were susceptible to Polymyxin B. The highest rate of non-susceptibility was observed with levofloxacin (46.8%), followed by carbapenems: imipenem (43.7%) and meropenem (40.6%). Additionally, 37.5% of the isolates were classified as multidrug-resistant (MDR). In phenotypic research for carbapenemases, 35.7% of the isolates were positive for plasmid-mediated AmpC, and 14.3% were positive for Metallo-β-lactamases. Regarding biofilm production, 75% of the isolates were classified as moderate/strong biofilm producers. Conclusion: Therefore, oral cavity colonization by P. aeruginosa in ICU patients is evident, with notable multidrug resistance to antibiotics, highlighting the need for vigilant monitoring and effective oral hygiene practices for these patients.