A multiresistant clone of Pseudomonas aeruginosa sequence type 773 spreading in a burn unit in Orumieh, Iran.

Herein, we describe the phenotypic and genotypic characterization of a multiresistant clone of Pseudomonas aeruginosa disseminating in a burn unit in Orumieh, Iran. A total of 58 isolates of P. aeruginosa were collected during August 2007 and June 2008. Minimum inhibitory concentrations (MICs) of P. aeruginosa isolates were determined against 11 antimicrobial agents by E test. Serotyping, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST) were used for studying the clonal relationship among the isolates. Antibiotic susceptibility testing revealed that most of the isolates were multidrug resistant and colistin was the antibiotic with the highest activity. Pseudomonas aeruginosa isolates fell into nine different serotypes, and O10 and O11 were the most common. PFGE analyses showed 12 different genotypes and 68.1% of isolates showed more than 80% similarity, indicating possible clonal relatedness. These isolates were found to belong to the same sequence type, ST773. This sequence type has earlier been reported from China, and a double locus variant of this ST has been found earlier in France in a PER-1 extended-spectrum β-lactamase-producing P. aeruginosa.