Abstract
Background: Many clinical isolates of Pseudomonas aeruginosa exhibit antibiotic-resistance and it is the main cause of hospital
infections.
Objectives: The current study aimed at evaluating the diversity of genes coding for antibiotic resistance in clinical and environmental
isolates of P. aeruginosa in Hamadan, West of Iran.
Methods: In the current cross sectional study, 100 clinical and 50 environmental isolates of P. aeruginosa were collected from October
2013 to May 2014. The standard disk diffusion method (SDD) was performed to test antibiotic susceptibility. All isolates were
evaluated by the polymerase chain reaction (PCR) for the presence of class 1 integrons and genes encoding resistance to aminoglycoside
antibiotics. The relationship between antibiotic resistance and integrons was tested by the 2-tailed chi-square (χ
2
) or the Fisher
exact tests. P values ≤ 0.05 were considered statistically significant.
Results: The most common antibiotic resistance was to cotrimoxazole (61.3%). The least observed resistance was to meropenem
(9.3%) and piperacillin /tazobactam (12%). The result of minimum inhibitory concentration (MIC) for amikacin showed that 20%
of the strains were resistant, 15% had intermediate resistance, and 65% were sensitive. Class 1 integrons were found in 57% of the
isolates. The aminoglycoside-resistance cassette included aadA (confers resistance to streptomycin and spectinomycin) and aphA1
(encoded aminoglycoside 3’-phosphotransferase) genes were the most prevalent in the isolates.
Conclusions: Antibiotic resistance had a high prevalence in clinical isolates of P. aeruginosa and was commonly associated with
class 1 integrons. The knowledge of drug resistance patterns helps to apply effective antibiotic treatments and appropriate infection
control measures to prevent the spread of infection in hospitals.