Which isolates of the Enterobacteriaceae family most commonly produce extended-spectrum B-lactamase (ESBL)?

The isolates of the Enterobacteriaceae family that most commonly produce extended-spectrum beta-lactamases (ESBL) are indeed Escherichia coli and Klebsiella pneumoniae. This is primarily due to their association with resistance mechanisms that have evolved in response to the widespread use of beta-lactam antibiotics.

In the case of E. coli, it is one of the most frequent causes of urinary tract infections and other infections, making its ability to produce ESBLs a significant concern in clinical settings. Similarly, Klebsiella pneumoniae is known for being associated with severe infections, particularly in hospital environments, and is recognized for producing ESBLs, contributing to its pathogenicity and complicating treatment options.

These bacteria can acquire resistance genes either through plasmids or by horizontal gene transfer, leading to a higher incidence of these resistant strains in healthcare settings. Thus, the identification of these organisms as significant producers of ESBLs emphasizes the challenges in treating infections caused by them and underscores the need for effective infection control measures.