detection of ispa1328 and isppu21, two novel insertion sequences in the oprd porin and blaimp-1 gene among metallo-beta-lactamase-producing pseudomonas aeruginosa isolated from burn patients

background carbapenemes are a good choice for treatment of infections caused by multidrug resistant pseudomonads aeruginosa. the emergence of carbapenem resistance has become a major problem in treatment of this organism especially among immunocompromised patients including burn patients. objectives the aim of this study was to investigate carbapenem-resistance mechanisms among burn patients in tehran, iran, during 2014 - 2015. methods the antibiotic resistance phenotypic test was accomplished by the kirby bauer disk diffusion method. the phenotypic investigation of metallo-beta-lactamase (mbl) producers was evaluated by the combined disk diffusion test (cddt) method. the prevalence of mbl genes, including blaimp-1 and blavim-1 was evaluated by polymerase chain reaction (pcr) and sequencing methods. amplification of oprd was performed by pcr and the results of sequencing were aligned with wild-type p. aeruginosa strain pao1. results a total of 100 p. aeruginosa were investigated, of which, 95 were resistance to imipenem. out of 95 imipenem resistant isolates,, 81 (85.2%) were mbl producers. among all isolates, 13 strains carried the blaimp-1 gene, whereas all of the strains were negative for the blavim-1 gene. amplification of oprd porin was performed for all 100 p. aeruginosa strains. two insertion sequences (iss) including isppu21 and ispa1328 were detected in pcr products of oprd gene, that were larger than expected. conclusions the prevalence of β-lactamase-producing isolates and their isolation from life-threatening infections in burn patients is increasing at an alarming rate worldwide. also, we have identified two novel is elements, ispa1328 and isppu21, in p. aeruginosa isolates from hospitals in tehran, iran. in most of the isolates, insertional inactivation of oprd by ispa1328 and isppu21 were associated with carbapenem resistance.