CLINICAL QUESTION
What is the nature of the antimicrobial resistance of Pseudomonas aeruginosa isolates of chronic rhinosinusitis (CRS) patients in planktonic and biofilm form, grown in aerobic and anaerobic conditions?
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December 2024BOTTOM LINE
P. aeruginosa isolates from CRS patients grown in anaerobic conditions showed significantly increased antibiotic resistance with increased metabolic activity but decreased biofilm biomass.
BACKGROUND: In CRS, congestion and blockage can cause anaerobic conditions within the sinus cavities, promoting the expression of virulence and antibiotic-resistant genes in invading pathogens. P. aeruginosa is the second most common bacterium isolated in CRS. P. aeruginosa can establish drug-resistant biofilms, and its presence is associated with severe recalcitrant CRS.
STUDY DESIGN: Lab study
SETTING: Basil Hetzel Institute for Translational Health Research, Central Adelaide Local Health Network, The Queen Elizabeth Hospital, Woodville South, South Australia
SYNOPSIS: Researchers grew
P. aeruginosa clinical isolates of 25 CRS patients, 19 of whom also had cystic fibrosis (CF), in planktonic and biofilm form and in aerobic and anaerobic conditions. They then assessed and compared the minimum inhibitory concentration (MIC) and minimum biofilm eradication concentration (MBEC) values of three commonly used antibiotics: ciprofloxacin, levofloxacin, and gentamicin. Metabolic activity by fluorescein diacetate assay, biofilm biomass by crystal violet assay, and eDNA concentration were also assessed in both conditions. Findings showed that P. aeruginosa planktonic cells grown in anaerobic conditions exhibited increased gentamicin resistance (p < .01), whereas P. aeruginosa biofilms grown in anaerobic conditions displayed significantly increased MBEC values for gentamicin (p < .0001) and levofloxacin (p < .001). The metabolic activity of anaerobic biofilms was significantly higher compared with aerobic biofilms (p < .0001); however, the biofilm biomass of isolates grown in aerobic conditions was higher than in anaerobic conditions (p < .5). The differences in MBEC values for the various antibiotics for isolates grown in aerobic and anaerobic conditions were smaller for those isolates sourced from CF CRS patients compared to those harvested from non-CF CRS patients. Study limitations included a lack of healthy control patients.
CITATION: Tuli JF, Ramezanpour M, Cooksley C, et al. Increased antibiotic resistance of Pseudomonas aeruginosa isolates from chronic rhinosinusitis patients grown in anaerobic conditions. Laryngoscope Investig Otolaryngol. 2024;9:e1244. doi: 10.1002/lio2.