Exploring the Antibiotic Resistance Profile of Clinical Klebsiella pneumoniae Isolates in Portugal

While antibiotic resistance is rising to dangerously high levels, resistance mechanisms are spreading globally among diverse bacterial species. The emergence of antibiotic-resistant Klebsiella pneumoniae, mainly due to the production of antibiotic-inactivating enzymes, is currently responsible for most treatment failures, threatening the effectiveness of classes of antibiotics used for decades. This study assessed the presence of genetic determinants of beta-lactam resistance in 102 multi-drug resistant (MDR) K. pneumoniae isolates from patients admitted to two central hospitals in northern Portugal from 2010 to 2020. Antimicrobial susceptibility testing revealed a high rate (> 90%) of resistance to most beta-lactam antibiotics, except for carbapenems and cephamycins, which showed antimicrobial susceptibility rates in the range of 23.5-34.3% and 40.2-68.6%, respectively. A diverse pool of beta-lactam resistance genetic determinants, including carbapenemases- (i.e., bla(KPC-like) and bla(OXA-48-like)), extended-spectrum beta-lactamases (ESBL; i.e., bla(TEM-like), bla(CTX-M-like) and bla(SHV-like)), and AmpC beta-lactamases-coding genes (i.e., bla(CMY-2-like) and bla(DHA-like)) were found in most K. pneumoniae isolates. bla(KPC-like) (72.5%) and ESBL genes (37.3-74.5%) were the most detected, with approximately 80% of K. pneumoniae isolates presenting two or more resistance genes. As the optimal treatment of beta-lactamase-producing K. pneumoniae infections remains problematic, the high co-occurrence of multiple beta-lactam resistance genes must be seen as a serious warning of the problem of antimicrobial resistance.