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Penicillinase was the first β-lactamase to be identified. It was first isolated by Abraham and Chain in 1940 from E. coli (which are gram-negative) even before penicillin entered clinical use, [5] but penicillinase production quickly
Penicillin resistance in Staphylococcus aureus [3] appeared very soon after penicillin entered general clinical use in 1943, and the mechanism of resistance was the production of β-lactamase. Modification of the penicillin molecule so that it was resistant to being broken down by β-lactamase was able to temporarily overcome this problem.
The β-lactam core structures. (A) A penam.(B) A carbapenam.(C) An oxapenam.(D) A penem.(E) A carbapenem.(F) A monobactam.(G) A cephem.(H) A carbacephem.(I) An oxacephem. This is a list of common β-lactam antibiotics—both administered drugs and those not in clinical use—organized by structural class.
β-Lactam antibiotics are indicated for the prevention and treatment of bacterial infections caused by susceptible organisms. At first, β-lactam antibiotics were mainly active only against gram-positive bacteria, yet the recent development of broad-spectrum β-lactam antibiotics active against various gram-negative organisms has increased their usefulness.
Penicillin core structure. The β-lactam ring is part of the core structure of several antibiotic families, the principal ones being the penicillins, cephalosporins, carbapenems, and monobactams, which are, therefore, also called β-lactam antibiotics. Nearly all of these antibiotics work by inhibiting bacterial cell wall biosynthesis.
Penicillinase is a bacterial enzyme produced by bacteria resistant to other β-lactam antibiotics which hydrolyses the antibiotic, rendering it non-functional. Methicillin is not bound and hydrolysed by penicillinase, meaning it can kill the bacteria, even if this enzyme is present.
The extended-spectrum penicillins are a group of antibiotics that have the widest antibacterial spectrum of all penicillins. [1] Some sources identify them with antipseudomonal penicillins, [2] others consider these types to be distinct. [3] This group includes the carboxypenicillins and the ureidopenicillins.
Flucloxacillin is insensitive to beta-lactamase (also known as penicillinase) enzymes secreted by many penicillin-resistant bacteria. The presence of the isoxazolyl group on the side chain of the penicillin nucleus facilitates the β-lactamase resistance, since they are relatively intolerant of side chain steric hindrance .