To Örebro University

Background: The emergence of multidrug-resistant Pseudomonas aeruginosa (MDR-PA) is a therapeutic challenge in patients with CF. β-lactamases are the most important mechanism of resistance to β-lactam antibiotics.

Aims: To identify the variability of β-lactamase resistance genes of MDR-PA in sputa of CF patients

Methods: Two hundred forty -six MDR-PA isolates were collected from lower respiratory samples of patients with pulmonary diseases over the 3-year period. Eighteen(7.32%) sputa samples were from 5 CF patients. The identification and antimicrobial susceptibility of the MDR-PA isolates were performed using BD PhoenixTM and E-test in compliance with CLSI guidelines. Whole-genome sequencing was used for gene identifications.

Results: Nine sputum samples were collected from CF patient 1;4 samples from patient 2;2 samples each of patients 3 and 4 and 1 sample from patient 5. The β-lactamase resistant P aeruginosa showed the highest resistance toward cefepime (100%), 55.56% toward each piperacillin-tazobactam and meropenem, and 50% to ceftazidime. β-lactamase genes in MDR-PA were variable within the same CF individual and from patient to patient. All classes of β-lactamase genes were identified (Class A; SHV-11, VEB-9, TEM-87, TEM-116, TEM-126. Class B;VIM-2. Class C;PDC-1, PDC-3, PDC-7, PDC-8. Class D;OXA-10, OXA-50, OXA-114a) with the highest percentage for OXA-50 harbored in 61.11% of isolates

Conclusions: Variability of β-lactamase genes in P aeruginosa isolates from CF patients may affect the progression of CF and personal specific antibiotics response to such infection