Molecular identification and antibiotics resistance genes profile of Pseudomonas aeruginosa isolated from Iraqi patients

Pseudomonas aeruginosa is one of the leading Gram-negative organisms associated with nosocomial infections. The increasing frequency of multidrug-resistant P. aeruginosa (MDRPA) strains affects the efficacious antimicrobial options which are severely limited. In this prospective study, forty two different types of samples collected from patients with multiple types of infections attainted to AL-Kadhyimia Teaching Hospital-Baghdad-Iraq, from February, 2012 to August, 2012. Morphological characteristics, biochemical testing by Vitek 2 Compact for Gram-negative Identification, card 2GN and amplification of species-specific 16SrDNA gene were used to identify P. aeruginosa. The antibiotic sensitivity profiles of the strains were determined against ten antibiotics belonging to different classes using the BioMerieux Vitek2 compact system AST card. In order to identify the genes implicated in antimicrobial resistance mechanisms, DNA was extracted from collected samples and resistance genes PstS, blaOXA-50, blaOXA-2 and bla IMP-13 were amplified using polymerase chain reaction (PCR). The results showed that there were difference in number of P. aeruginosa isolates that were identified using Vitek 2 Compact for Gram-negative Identification, card 2GN (25/42) and 16SrDNA gene(29/42), but it was not statistically significant (p value= 1.000). Also, it showed that the highest resistance percentages of strains to tested antibiotics was for Ceftriaxone (96.55%) and the lowest resistant percentages was (17.24%) for Meropenem. Seven strains out of twenty nine (24%) were resistant to all tested antibiotics and were identified as a multidrug resistance strain (MDR). The study detects the presence of PstS gene and blaOXA-50 in (65.5% and 93% of strains, respectively), but it did not identify the presence of blaOXA-2 or blaIMP 13 at any of the tested strains of P. aeruginosa. There was no significant relationship between the presence of blaOXA-50 and resistance to Meropenem, Imipenem, Ceftazidime and Cefepim (p value 1.000, 1.000, 0.474, and 0308, respectively). We concluded that Meropenem is the most effective antibiotic and can be considered as the drug of choice against P. aeruginosa. This study is the first report presence of PstS and blaOXA50 in P. aeruginosa in Iraq. The presence of blaOXA-50 is important in order to identify and track the spread of multidrug-resistant P. aeruginosa clones since blaOXA-50 may be potential clonality marker.   Key words: Pseudomonas aeruginosa, molecular identification, antibiotic resistance genes.