Cephalosporins are a group of broad spectrum, semi-synthetic beta-lactam antibiotics derived from the mould Cephalosporium. The mechanism of action of cephalosporins is the same as penicillins in that they interfere with bacterial cell wall synthesis. They are classified according to the chronological order in which they were produce. Beta-lactamase inhibitors block the activity of beta-lactamase enzymes. Some species of bacteria produce beta-lactamase enzymes, which cleave the beta-lactam group in antibiotics, such as cephalosporins, that have a beta-lactam ring in their structure. In doing so the beta-lactamase enzyme inactivates the antibiotic and becomes resistant to that antibiotic. To avoid development of resistance, beta-lactamase inhibitors are administered with the beta-lactam antibiotics so the action of beta-lactamase is inhibited. This tends to widen the spectrum of antibacterial activity.