Emergence of Multidrug-Resistant Pseudomonas aeruginosa: Detection of Isolates harboring blaCTX gene causing infections in hospital and determination of their susceptibility to antibiotics

Introduction and Because of its ubiquitous nature, ability to survive in moist environments, and innate resistance to many antibiotics and antiseptics, P. aeruginosa is a common pathogen in hospitals. The goals of this study were detection of Psudomonas aeruginosa harboring blaCTX gene causing infections in hospitals, determination of their susceptibility to antibiotics and survey the ESBL production. In the present cross-sectional study, clinical samples from hospitalized patients (Shiraz, Iran) were collected, and culture was done on microbiological media. For final identification, biochemical tests and API 20NE system were used. Disc diffusion, combination disk, modified hodge test (MHT) and E-test were used for antibiotic susceptibility testing, ESBL production, carbapenemas production, and MIC values for imipenem, respectively, according to CLSI 2014 recommendations. The blaCTX gene was detected in the isolates by PCR molecular method. In the current study, 45 isolates of Pseudomonas aeroginosa were obtained from hospitalized patients, consisting of 19 males (42.2%) and 26 females (57.8%). As observed, 57.8% (26 strains) of isolates were recovered from sputum. The most effective antibiotics against isolates were amikacin and colistin, with 97.8% of isolates showing sensitivity to them. The highest resistance was to cefotaxime (97.8%). As revealed, 77.8% of isolates showed response to group 2 carbapenems (imipenem, meropenem). All imipenem resistant strains have MIC > 32 for imipenem. Seventeen strains (37.7%) were resistant to quinolones (ciprofloxacin, norfloxacin). The results of PCR on blaCTX gene indicated that 15.5% of the isolates possess the gene. This study is important from a practical point of view. We believe that the use of imipenem for the treatment of P. aeruginosa should be reserved for situations where the infection is polymicrobial, particularly when anaerobic bacteria are present, or for pseudomonal isolates resistant to other antibiotics.