Determination of Minimum Inhibitory Concentration of Different Antibiotic Groups in Clinical Isolates of Pseudomonas aeruginosa Containing p-AmpC and Their Relationship with Antibiotic Resistance Pattern

AmpC-type beta-lactamases have been implicated in group C of Amber, which includes EBC, CIT, MOX, FOX, DHA, and ACC. The active presence of these plasmid genes in clinical isolates of P.aeruginosa has resulted in resistance to a wide range of antibiotics. Therefore, we aimed to determine the minimum inhibitory concentrations (MIC) of different antibiotic groups in clinical isolates of P. aeruginosa carrying AmpC enzyme and study their relationship pattern.
In this descriptive study, the MIC of 95 P. aeruginosa isolates was determined using E-test for cefocytosine, cefpodoxime, cefotaxime, ceftazidime, ciprofloxacin, colicitin, aztreonam, and ceftriaxone antibiotics (Liofilchem, Italy). Multiplex polymerase chain reaction was used to amplify and identify plasmid genes. The Chi-squared test was used to determine the relationship between variables.
Of the 95 P. aeruginosa isolates, 95 (100%) isolates were resistant to cefoxitin, 79 (83.5%) isolates to cefpodoxime, 2 (2.1%) isolates to ceftazidime, 87 (81.57%) isolates to ceftriaxone, and 22 (23.15%) isolates were resistant to aterranum, but none of the isolates was resistant to colistin. In addition, 21 (22.1%) isolates had FOX gene, 13 (11.57%) isolates had AAC gene, 7 (36.6%) isolates had MOX gene, 4 (21.4%) isolates had CIT gene, 2 (2.1%) isolates had DHA gene, and 1 (1.05%) isolate had EBC gene. It is worth mentioning that there was a significant relationship between the presence of plasmid genes and antibiotic resistance (level of significance: P≤0.05).
The presence of the genes encoding the AmpC enzyme can provide the ground for resistance to a broad range of antibiotics.