Resistance bacteria?

Question

Since many of the common pathogens found in respiratory tract infections are Beta-Lactamase producing (resistant to penicillin), why aren't they also resistant to cephalosporins? I am asking because wikipedia says Penicillin and Cephalosporins are both Beta-latam drugs.

Answer 1

Cephalosporins are chemically similar to penicillins, but have more stable or protected beta-lactam rings, making them less likely to be broken down by bacterial penicillinases.  

Extended-spectrum beta-lactamases (ESBLs), however, are generally pumps which push the antibiotics out of the bacterial cell wall and cell membrane, protecting the bacteria from a wider variety of antibiotics.