Extended spectrum lactamase producing Enterobacteriaceae (ESBLs). Extended-spectrum B-lactamase is an enzyme that allows bacteria to become resistant to a wide variety of penicillins and cephalosporins. Bacteria that contain this enzyme are known as ESBLs or ESBL-producing bacteria. ESBL-producing Enterobacteriaceae are resistant to strong antibiotics including extended spectrum cephalosporins. According to the Centers for Disease Control and Prevention, more than two million people in the United States get infections that are resistant to antibiotics and at least 23,000 people die as a result. Over-prescription of antibiotics leads to antibiotic-resistant germs.