The pattern of antibiotic resistance within clinical isolates of Pseudomonas aeruginosa and detection of AmpC

Despite the improvements in hospital care and the introduction of a wide range of antimicrobial agents, Pseudomonas aeruginosa is also a common cause of infection in patients hospitalized in different wards of the hospital. Due to the rising resistance of this bacterium to antibacterial drugs, the importance of its resistance is increased. The enzyme β-lactamase AMP-C is a type of cephalosporinase coded on the chromosome of the bacterium. In many bacteria, induction of AMP-C enzymes can occur at high levels by many mutations. In this paper, the detection of AMP-C gene was reported in clinical isolates of Pseudomonas aeruginosa.
80 Pseudomonas aeruginosa bacteria, verified by gram stain and biochemical tests, were isolated from wound samples collected from patients with burning at burning hospital in Tehran. For identifying antibiotic resistance, in vitro susceptibility of 80 Pseudomonas aeruginosa isolates to 15 antimicrobial agents, includimg colistin, amoxicillin, ceftriaxone, cefixime, cefalotin, ciprofloxacin, amikacin, doxycyclin, ampicillin, trimethoprim, ceftazidime, gentamicin, cefotaxime, piperacilin and imipenem was performed by Kirby-Bauer’s disk diffusion method according to Clinical and Laboratory Standards Institute (CLSI, 2016) guideline. PCR method was used to identify AMP-C gene in 80 Pseudomonas aeruginosa strains.
Pseudomonas aeruginosa strains showed the highest resistance to cephalotin (100%), doxycycline (100%), cefixime (100%), amoxicillin (100%), ampicillin (100%), amikacin (100%) and teri-methaprime (100%). Highest sensitivity of Pseudomonas aeruginosa strains was observed to colistin (67.5%), gentamicin (32.5%), piperacillin (30%), ciprofloxacin (28.7%), imipenem (18.7%), ceftazidime (13.7%), ceftriaxone (11.2%) and cefotaxime (10%). AMP-C gene was detected in 5% of isolates.
According to the results of this study, in many Pseudomonas aeruginosa strains, the presence of all resistance genes in an isolate was not observed. Therefore, it can be hoped that β-lactamase enzymes are not coded in most isolates