Evaluation of the roles of Mex genes in antibiotic resistance of some strains of Pseudomonas aeruginosa and the use of antibiotic combinations to boost their susceptibility pattern

Abstract

Pseudomonas aeruginosa is a prevalent pathogen responsible for various infections, and exhibits significant resistance to a broad spectrum of antibiotics, leading to increased mortality rates. This study aimed to assess the role of mex genes in antibiotic resistance among indigenous strains of Pseudomonas aeruginosa and enhance their susceptibility through antibiotic combinations. Ten isolates were selected based on their appearance on selective media, microscopy and biochemical characterization. Antibiotic resistance profiles for fluoroquinolones (ofloxacin, pefloxacin, sparfloxacin, ciprofloxacin), aminoglycosides (gentamicin, streptomycin), beta-lactams (amoxicillin) Sulfonamide (septrin) and Macrolide (septrin) were determined using the Bauer-Kirby disk diffusion method. Minimum inhibitory concentrations (MICs) for 13 individual antibiotics and 19 combined antibiotics were determined using two-fold serial dilution techniques. DNA was extracted from P. aeruginosa isolates and analyzed by polymerase chain reaction (PCR) to detect resistance genes- MexA, MexB, and MexZ. The MexA and MexZ resistance genes were detected in all isolates, while MexB was present in all except 3 of the isolates. P. aeruginosa exhibited the highest susceptibility to gentamicin (40%) and complete resistance to sparfloxacin (100%). The multiple antibiotic resistance (MAR) index ranged from 0.22 to 1. The MIC values for cefexime and ciprofloxacin was 128 µg/mL, while ciprofloxacin + amoxicillin was 32 µg/mL showing increased susceptibility. This study highlights the presence of highly resistant P. aeruginosa strains, it showed a relationship between the resistant genes and antibiotic resistance. Drug combination of ciprofloxacin and amoxicillin proved to be most susceptible against the pathogen. This brings the need to study the mechanism of resistance in the pathogen and target silencing these resistance genes. There should be sensitization, increased awareness among patients and healthcare providers regarding the rising antibiotic resistance of the strain.