Bacteria belonging to theEnterobacteriaceaefamily that produce extended-spectrumβ-lactamase (ESBL) enzymes are important pathogens of infections. Increasing numbers of ESBL-producing bacterial strains exhibiting multidrug resistance have been observed. The aim of the study was to evaluate the prevalence ofblaCTX-M,blaSHV, andblaTEMgenes among ESBL-producingKlebsiella pneumoniae,Escherichia coli, andProteus mirabilisstrains and to examine susceptibility to antibiotics of tested strains. In our study, thirty-six of the tested strains exhibitedblaCTX-Mgenes(blaCTX-M-15,blaCTX-M-3,blaCTX-M-91, andblaCTX-M-89). Moreover, twelve ESBL-positive strains harboredblaSHVgenes(blaSHV-18,blaSHV-7,blaSHV-2, andblaSHV-5), and the presence of ablaTEMgene(blaTEM-1)in twenty-five ESBL-positive strains was revealed. AmongK. pneumoniaethe multiple ESBL genotype composed ofblaCTX-M-15, blaCTX-M-3, blaSHV-18, blaSHV-7, blaSHV-2, andblaSHV-5genes encoding particular ESBL variants was observed. Analysis of bacterial susceptibility to antibiotics revealed that, amongβ-lactam antibiotics, the most effective againstE. colistrains was meropenem (100%), whereasK. pneumoniaewere completely susceptible to ertapenem and meropenem (100%), andP. mirabilisstrains were susceptible to ertapenem (91.7%). Moreover, among non-β-lactam antibiotics, gentamicin showed the highest activity toE. coli(91.7%) and ciprofloxacin the highest toK. pneumoniae(83.3%).P. mirabilisrevealed the highest susceptibility to amikacin (66.7%).

Antimicrobial resistance due to the continuous selective pressure from widespread use of antimicrobials in humans, animals and agriculture has been a growing problem for last decades. KPC β-lactamases hydrolyzed β-lactams of all classes. Especially, carbapenem antibiotics are hydrolyzed more efficiency than other β-lactam antibiotics. The KPC enzymes are found most often in Enterobacteriaceae. Recently, these enzymes have been found in isolates of Pseudomonas aeruginosa and Acinetobacter spp. The observations of bla KPC genes isolated from different species in other countries indicate that these genes from common but unknown ancestor may have been mobilized in these areas or that bla KPC -carrying bacteria may have been passively by many vectors. The emergence of carbapenem resistance in Gram-negative bacteria is worrisome because the carbapenem resistance often may be associated with resistance to many β-lactam and non-β-lactam antibiotics. Treatment of infections caused by KPC-producing bacteria is extremely difficult because of their multidrug resistance, which results in high mortality rates. Therapeutic options to treat infections caused by multiresistant Gram-negative bacteria producing KPC-carbapenemases could be used polymyxin B or tigecycline.

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An increase in the antibiotic resistance among members of the Enterobacteriaceae family has been observed worldwide. Multidrug-resistant Gram-negative rods are increasingly reported. The treatment of infections caused by Escherichia coli and other Enterobacteriaceae has become an important clinical problem associated with reduced therapeutic possibilities. Antimicrobial carbapenems are considered the last line of defense against multidrug-resistant Gram-negative bacteria. Unfortunately, an increase of carbapenem resistance due to the production of Klebsiella pneumoniae carbapenemase (KPC) enzymes has been observed. In this study we describe the ability of E. coli to produce carbapenemase enzymes based on the results of the combination disc assay with boronic acid performed according to guidelines established by the European Community on Antimicrobial Susceptibility Testing (EUCAST) and the biochemical Carba NP test. Moreover, we evaluated the presence of genes responsible for the production of carbapenemases (bla KPC, bla VIM, bla IMP, bla OXA-48) and genes encoding other β-lactamases (bla SHV, bla TEM, bla CTX-M) among E. coli isolate. The tested isolate of E. coli that possessed the bla KPC-3 and bla TEM-34 genes was identified. The tested strain exhibited susceptibility to colistin (0.38 μg/mL) and tigecycline (1 μg/mL). This is the first detection of bla KPC-3 in an E. coli ST479 in Poland.