Evaluation of Antibiotic Tolerance in Pseudomonas aeruginosa for Aminoglycosides and its Prediction of Resistance Development Through In-silico Transcriptomic Analysis

Pseudomonas aeruginosa causes severe life-threatening infections and are difficult to treat. The lack of antibiotic response in P. aeruginosa is due to adaptive resistance, which prevents the entry of antibiotics into cytosol of the cell. Among different groups of antibiotics, aminoglycosides show superior antibiotic response and are used as a parental antibiotic for treatment. This study aims to determine the kinetics of adaptive resistance development and gene expression changes in P. aeruginosa exposed to amikacin, gentamicin, and tobramycin. In vitro antibiotic exposure to P. aeruginosa was performed and optical density of the cells were monitored for every 12 hours until 72 hours. The growth pattern plotted in graph represents the kinetics of adaptive resistance developed to respective antibiotics. The transcriptomic profile of P. aeruginosa PA14 to post exposed antibiotic was taken from Gene Expression Omnibus (GEO), NCBI. The gene expressions of two datasets were analyzed by case-control study. Tobramycin exposed P. aeruginosa failed to develop adaptive resistance in 0.5ug/mL, 1ug/mL and 1.5ug/mL of its MIC. Whereas, amikacin and gentamicin treated P. aeruginosa developed tolerance in the inhibitory concentrations of the antibiotics. This depicts the superior in vitro response of tobramycin over the gentamicin and amikacin. Furthermore, tobramycin treated P. aeruginosa microarray analysis resulted in low expression of catalytic enzyme 16s rRNA Methyltransferase E, B & L, alginate biosynthesis genes and several proteins of Type 2 Secretory System (T2SS) and Type 3 Secretory System (T3SS). The Differentially Expressed Genes (DEGs) of alginate biosynthesis, and RNA Methyltransferases suggests increased antibiotic response and low probability of developing resistance. The use of tobramycin as a parental antibiotic with its synergistic combination might combat P. aeruginosa with increased response.