Phenotypic and Genotypic Characterization of ESBL-, AmpC-, and Carbapenemase-Producing <b><i>Klebsiella pneumoniae</i></b> and <b><i>Escherichia coli</i></b> Isolates

Abstract

<b><i>Objectives:</i></b> Drug resistance among gram-negative bacteria is a worldwide challenge. Due to the importance of drug-resistant <i>Klebsiella pneumoniae</i> and <i>Escherichia coli</i> strains in hospital-acquired infections, we aimed to determine the phenotypic and genotypic characteristics of ESBL-, AmpC-, and carbapenemase-producing isolates obtained from hospitalized patients in Tehran and Ilam (Iran). <b><i>Materials and Methods:</i></b> In total, 90 <i>K. pneumoniae</i> isolates and 65 <i>E. coli</i> isolates were collected from various infections. Phenotypic identification of bacterial isolates was performed using standard methods. Phenotypic screening of ESBL, AmpC, and carbapenemase enzymes was carried out. Detection of ESBL, AmpC, and carbapenemase genes was also performed by the PCR method. <b><i>Results:</i></b> Phenotypic detection tests showed that 36 (40%) <i>K. pneumoniae</i> and 23 (35.4%) <i>E. coli</i> isolates were ESBL producers. Moreover, 18 (20%) and 6 (9.2%) <i>K. pneumoniae</i> and <i>E. coli</i> isolates were AmpC producers, respectively. Modified Hodge test results indicated that 39 (43.3%) <i>K. pneumoniae</i> and 18 (27.7%) <i>E. coli</i> isolates produced carbapenemase. Molecular tests showed that 40% of <i>K. pneumoniae</i> and 36.9% of <i>E. coli</i> isolates were ESBL positive. AmpC was detected in 24.4 and 13.8% of <i>K. pneumoniae</i> and <i>E. coli</i> isolates. Carbapenemase was detected in 34 (37.8%) <i>K. pneumoniae</i> and 13 (20%) <i>E. coli</i> isolates. ­<b><i>Conclusion:</i></b> In this study, 3 <i>K. pneumoniae</i> isolates simultaneously carried ESBL, AmpC, and carbapenemase genes. Up-to-date strategies such as combination therapy or utilization of new antimicrobial agents might help to combat such drug-resistant organisms.