Insights on carbapenem-resistant Pseudomonas aeruginosa: phenotypic characterization of relevant isolates

Main Article Content

Márió Gajdács
Krisztina Kárpáti
Anette Stájer
Stefania Zanetti
Matthew Gavino Donadu


Pseudomonas aeruginosa (P. aeruginosa) is ubiquitous in nature, and may be a causative agent in severe, life-threatening infections. In >60% of cases, β-lactam antibiotics are used in the therapy of P. aeruginosa infections, therefore the emergence of carbapenem-resistant P. aeruginosa (CRPA) is a significant clinical concern. In this study, phenotypic methods were used to characterize fifty-four (n = 54) P. aeruginosa isolates, which were included based on their suspected non-susceptibility to meropenem. Minimum inhibitory concentrations (MICs) of meropenem, ceftazidime, cefepime, ciprofloxacin, gentamicin, were determined using E-tests, while colistin MICs were determined using broth microdilution. The isolates were subjected to the modified Hodge test (MHT), the modified carbapenem-inactivation method (mCIM) and the imipenem/EDTA combined disk test (CDT). AmpC and efflux pump overexpression was studied using agar plates containing cloxacillin and phenylalanine-arginine β-naphthylamide (PAβN), respectively. Assessment of biofilm-formation was carried out using the crystal violet tube-adherence method. 38.9% of the strains showed meropenem MICs in the resistant range (>8 mg/L). Efflux-pump overexpression and AmpC-hyperproduction was seen in 44.4% and 35.2% of isolates, respectively. 88.8% of the isolates were characterized as strong biofilm-producers. On the other hand, the presence of carbapenemases was suspected in a minority (16.7%) of tested isolates. As safe and effective therapeutic options in carbapenem-resistant Gram-negative infections are severely limited, characterization of these isolates using phenotypic and molecular-based methods is important to provide insights into the epidemiological features of these pathogens.


Download data is not yet available.

Article Details

How to Cite
Gajdács, M., Kárpáti, K., Stájer, A., Zanetti, S. and Donadu, M. G. (2021) “Insights on carbapenem-resistant Pseudomonas aeruginosa: phenotypic characterization of relevant isolates”, Acta Biologica Szegediensis, 65(1), pp. 105–112. doi: 10.14232/abs.2021.1.105-112.