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

• A. E. coli and Klebsiella pneumoniae
• B. Yersinia enterocolitica and Yersinia pestis
• C. Morganella morganii and Proteus vulgaris
• D. Salmonella typhi and Shigella sonnei

Answer: (A)

The isolates of the Enterobacteriaceae family that most commonly produce extended-spectrum β-lactamase (ESBL) are Escherichia coli and Klebsiella pneumoniae. These two species are known for their significant role in the emergence of antibiotic resistance, particularly in hospital settings where infections caused by such resistant bacteria can be challenging to treat.

ESBLs are enzymes that confer resistance to a broad range of β-lactam antibiotics, which includes penicillins and cephalosporins. Both E. coli and Klebsiella pneumoniae have been thoroughly documented in studies as frequent producers of ESBLs. This resistance mechanism primarily arises due to acquired resistance genes, often transmitted via plasmids, which can make the management of infections caused by these organisms quite complex.

On the other hand, the other options listed are less commonly associated with the production of ESBLs. Yersinia enterocolitica and Yersinia pestis are not typically linked with this type of β-lactamase production, while Morganella morganii and Proteus vulgaris may show some resistance but are not as prevalent in producing ESBLs as E. coli and Klebsiella pneumoniae. Similarly, Salmonella typhi