What are the definitions of Extended-Spectrum Beta-Lactamases (ESBL)?

From the Guidelines

ESBL-producing bacteria are defined as organisms that show resistance to third-generation cephalosporins and monobactams, but remain susceptible to cephamycins and carbapenems, as stated in the most recent guideline endorsed by multiple Italian societies 1. The definition of ESBL-producing bacteria is crucial in guiding antibiotic therapy, as these organisms are resistant to many commonly used antibiotics.

• ESBLs are primarily found in Gram-negative bacteria, especially Escherichia coli and Klebsiella species.
• The Ambler classification system is used to classify carbapenemases, which confer carbapenem resistance in Enterobacteriaceae, into different classes, including Class A, Class B, and Class D 1.
• Knowledge of the molecular mechanism responsible for the carbapenem-resistant phenotype is crucial because each class of enzymes confers variable susceptibility profiles that require different treatment strategies.
• Recent data indicate that infections caused by ESBL-producing organisms are an emerging problem in outpatient settings in various parts of the world, and hospital laboratories may need to routinely screen for ESBL-producing Enterobacteriaceae originating from the community 1.
• When treating ESBL infections, carbapenems are typically the drugs of choice, though alternatives like piperacillin-tazobactam, ceftazidime-avibactam, or fosfomycin may be considered depending on susceptibility testing and infection site.
• The use of rapid testing strategies to identify specific carbapenemases and to guide antibiotic therapy is strongly recommended, as it can influence the outcome of critically ill patients with bloodstream infections caused by KPC-producing K. pneumoniae 1.

From the Research

ESBL Definitions

• Extended Spectrum Beta-lactamases (ESBLs) are defined as enzymes produced by certain bacteria that are able to hydrolyze extended spectrum cephalosporin 2.
• ESBLs are enzymes capable of hydrolysing penicillins, broad-spectrum cephalosporins and monobactams, and are generally derived from TEM and SHV-type enzymes 3.
• ESBL-producing organisms pose unique challenges to clinical microbiologists, clinicians, infection control professionals and antibacterial-discovery scientists 3.

Key Characteristics of ESBLs

• ESBLs are effective against beta-lactam antibiotics such as ceftazidime, ceftriaxone, cefotaxime and oxyimino-monobactam 2.
• ESBLs are often located on plasmids that are transferable from strain to strain and between bacterial species 3.
• The prevalence of ESBLs is increasing, and in many parts of the world 10-40% of strains of Escherichia coli and Klebsiella pneumoniae express ESBLs 3.

Clinical Significance of ESBLs

• ESBL-producing Enterobacteriaceae have been responsible for numerous outbreaks of infection throughout the world and pose challenging infection control issues 3.
• Clinical outcomes data indicate that ESBLs are clinically significant and, when detected, indicate the need for the use of appropriate antibacterial agents 3.
• Therapy of infections caused by ESBL-producing bacteria with an antimicrobial to which they are resistant results in treatment failure, higher cost and increased mortality 4.