Beta-lactam resistance of Enterobacteriaceae

Abstract

Beta-Lactam Resistance in Enterobacteriaceae Hyunjoo Pai, M.D. Division of Infectious Diseases, Hanyang University Medical School Beta-lactams are one of the most commonly prescribed antimicrobials worldwide. With the wide use of beta-lactam-containing agents, the resistance to beta-lactam continues to be increasing. Among several resistance mechanisms, beta-lactamases are the most important one in gram-negative organisms, and new enzymes continue to be identified. ESBLs (extended spectrum beta-lactamases) are considered to be one of the most important resistant determinants, especially in Escherichia coli and Klebsiella pneumoniae. These enzymes are often derived from the common TEM, SHV and OXA enzymes, with an important emerging family of ESBLS named CTX-M. Other important plasmid beta-lactamases include plasmide-mediated cephalosporinases which were considered to be originated from an organism producing an AmpC beta-lactamase. Infections with ESBL-producing organisms are usually hospital-acquired, but there are several reports indicating the spread of those organisms to the community. A recent report shows that overall fatality rate for the bloodstream infections by ESBL-producing organisms is significantly higher than that for the infections by non-ESBL organisms, despite no difference in clinical severity at presentation. Another report compared the characteristics of bloodstream infections caused by organisms producing plasmid-mediated AmpC enzyme and those by ESBL-producers, showing the similar clinical outcome between two groups. The infections caused by these resistant organisms resulted more fatality in patients and posed a great difficulty for selecting empirical antimicrobial agents. Multi-drug resistant plasmids are now being disseminated freely among the enterobacteriaceae, resulting in organisms with an accumulation of resistance factors. Organisms producing ESBLs often are multi-drug resistant because of the resistance selection with the use of antibiotics other than beta-lactams. Few antimocribials against gram-negative organisms are under development at the present, thus the resistance problem will be a big threat in modern hospital.