Molecular Detection of tox A Gene in Multidrug Resistance Pseudomonas aeruginosa Isolated from Burn Infections

Abstract Background: Exotoxin A (ExoA) is the most widespread and toxic virulence agent among pathogenic Pseudomonas aeruginosa species that acquire adenosine diphosphate-ribosyltransferase activity belonging to the class of exotoxins secreted by pathogenic bacteria that cause human diseases. Objectives: The aim of this study is to investigate ExoA in multidrug resistance P. aeruginosa isolated from burn infections. Materials and Methods: About 89 P. aeruginosa were isolated from burned infections. The Kirby–Bauer disc diffusion method on Mueller–Hinton agar was used to test different antibiotic susceptibilities. In addition, the ExoA encoding gene was analyzed using the polymerase chain reaction (PCR)-DNA-sequencing method. Results: The antibacterial susceptibility test of 89 P. aeruginosa showed a higher percentage of antibiotics resistant against amikacin for 14 isolates at (58.42%), then intermediate resistance against piperacillin was 21 isolates at (23.60%), while the higher sensitivity of antibiotics was against meropenem at 84 isolates (94.38 %). The presence of the tox A gene was not associated with antibiotic resistance ( P = 0.45), but the multidrug-resistant (MDR) isolates became more virulent when they produced the ExoA. PCR-DNA sequencing results appeared the presence of several mutations in tox A gene within two of the studied isolates that leads to change the amino acids, which may be the effect on exotoxin functions in the P. aeruginosa isolate 18-GF and slightly effects in the P. aeruginosa isolate 61-NR1 by effecting on protein conformation of domain III that participate in forming exotoxin complexed with nicotinamide and adenosine monophosphate. Conclusion: Most P. aeruginosa isolates recovered from burn infections produce ExoA and generally resist recently used antibiotics and some MDR isolates.