Extended-spectrum beta-lactamases.

Extended-spectrum beta lactamase (ESBL) producing gram-negative bacilli are a growing concern, especially because the species of organisms producing these enzymes are increasing. Bacteria possessing these enzymes are resistant to third-generation cephalosporins--antimicrobial agents important for inpatient therapy. These resistant organisms are clinically important because they result in increased morbidity and mortality. Additionally, some laboratories may have difficulty detecting ESBL-producing organisms. These and other issues are discussed in this article.