Objective: Bacterial multidrug-resistance (MDR) to antimicrobials has become an important public health issue all over the world and it involves both hospital and community-acquired strains.
Materials and methods: A number of 75 Escherichia coli and 77 Klebsiella pneumoniae (K.) strains identified in biological samples collected from community (CA) and hospital-acquired (HA) infections were found to be resistant to the third generation cephalosporins. Of these, 93 MDR strains were subjected to microarray analysis to detect the expression of 31 antimicrobial resistance genes.
Results: We found that all HA extended-spectrum β-lactamase (ESBL) producing E. coli strains had at least one resistance gene to third generation cephalosporins, while in 54% of all CA strains genetic substrates justifying their antibiotic resistance were identified. Almost 81% of HA-ESBL (Extended-Spectrum β Lactamase) K. pneumoniae strains had at least one resistance gene to third generation cephalosporins, while in only 6% of the CA strains a similar genotype was identified. In the HA group, the blaCTX-M-15 genotype proved to be most frequent in multidrug-resistant E. coli strains and second most frequent (after ampC) in K. pneumoniae, while in the CA group, this genotype was the fourth most frequent in ESBL E. coli (after ampC, sul1, tet(R)).
Conclusions: Overall, in 67% of all ESBL producing Enterobacteriaceae strains a genetic substrate justifying the resistance to beta-lactam antibiotics was identified; most of the remaining 33.33% strains were CA with a predominance of K. pneumoniae, in which a different antibiotic resistance genetic substrate (outside the detection limit of the kit used in this study) might have been involved.