Transversion and positive directional selection determine the major driving force for quorum sensing genes evolution in multi-drug resistant <em>Pseudomonas aeruginosa</em>

The increasing regulation of multi-drug resistance through quorum-sensing genes poses significant public health risks, potentially leading to higher hospitalization rates, ineffective treatments, and even fatalities. This research aims to explore the processes that govern the evolution of quorum-sensing genes in Pseudomonas aeruginosa. To achieve this, Pseudomonas aeruginosa isolates previously obtained and molecularly sequenced in earlier studies were tested for antibiotic susceptibility using standard methodologies. The resistant isolates were screened for minimum inhibitory concentration (MIC) and quorum-sensing genes using the broth dilution method and primer-dependent multiplex polymerase chain reaction, respectively. Mutation detection was conducted using Sequencher software, while transition-transversion bias, McDonald’s test, and Tajima’s neutrality test were assessed with MEGA software. The results indicate that Pseudomonas aeruginosa exhibits significantly reduced susceptibility to the tested antibiotics, as many isolates displayed distinct quorum-sensing genes for PhzS, lasI, RhlI, and lasR in the following proportions: 17 (37%), 8 (17.4%), 12 (26.1%), and 9 (19.6%). The resistance patterns for these quorum-sensing producing organisms ranged from 35.2% to 100% for PhzS, 44.7% to 100% for lasR, 50% to 100% for RhlI, and 62.5% to 100% for lasI. Most isolates also exhibited high MIC values, with many exceeding the highest concentration tested (128 μg/ml). The transition-transversion bias was measured at 0.87 for phzS, 0.73 for lasI, 0.81 for RhlI, and 0.91 for lasR. An analysis of McDonald’s test yielded values of 0.39 for phzS (greater than 0.16), 0.52 for lasI (greater than 0.48), 1.59 for RhlI (greater than 0.23), and 0.51 for lasR (greater than 0.41). These results suggest that the ratio of synonymous to non-synonymous divergence is higher than the ratio of synonymous to non-synonymous polymorphisms. The Tajima’s neutrality test results were negative, indicating that positive directional selection and transversion mutations may be factors contributing to the evolution of quorum-sensing genes.