AMR Gene Family
TEM-1 is the most commonly-encountered beta-lactamase in gram-negative bacteria. Up to 90% of ampicillin resistance in E. coli is due to the production of TEM-1. Also responsible for the ampicillin and penicillin resistance that is seen in H. influenzae and N. gonorrhoeae in increasing numbers. Although TEM-type beta-lactamases are most often found in E. coli and K. pneumoniae, they are also found in other species of gram-negative bacteria with increasing frequency. The amino acid substitutions responsible for the ESBL phenotype cluster around the active site of the enzyme and change its configuration, allowing access to oxyimino-beta-lactam substrates. Opening the active site to beta-lactam substrates also typically enhances the susceptibility of the enzyme to b-lactamase inhibitors, such as clavulanic acid. Although the inhibitor-resistant beta-lactamases are not ESBLs, they are often discussed with ESBLs because they are also derivatives of the classical TEM- or SHV-type enzymes. These enzymes were at first given the designation IRT for inhibitor-resistant TEM beta-lactamase; however, all have subsequently been renamed with numerical TEM designations. There are at least 19 distinct inhibitor-resistant TEM beta-lactamases. Inhibitor-resistant TEM beta-lactamases have been found mainly in clinical isolates of E. coli, but also some strains of K. pneumoniae, Klebsiella oxytoca, P. mirabilis, and Citrobacter freundii. Although the inhibitor-resistant TEM variants are resistant to inhibition by clavulanic acid and sulbactam, thereby showing clinical resistance to the beta-lactam-lactamase inhibitor combinations of amoxicillin-clavulanate (Co-amoxiclav), ticarcillin-clavulanate, and ampicillin/sulbactam, they normally remain susceptible to inhibition by tazobactam and subsequently the combination of piperacillin/tazobactam, although resistance has been described.
Antibiotic
Amoxicillin is a moderate-spectrum, bacteriolytic, beta-lactam antibiotic used to treat bacterial infections caused by susceptible microorganisms. A derivative of penicillin, it has a wider range of treatment but remains relatively ineffective against Gram-negative bacteria. It is commonly taken with clavulanic acid, a beta-lactamase inhibitor. Like other beta-lactams, amoxicillin interferes with the synthesis of peptidoglycan.
Antibiotic
Ampicillin is a penicillin derivative that is highly acid stable, with its activity similar to benzylpenicillin.
Antibiotic
Cefalotin is a semisynthetic cephalosporin antibiotic activate against staphylococci. It is resistant to staphylococci beta-lactamases but hydrolyzed by enterobacterial beta-lactamases.
Drug Class
Monobactams are a class of beta-lactam antibiotics with a broad spectrum of antibacterial activity, and have a structure which renders them highly resistant to beta-lactamases. Unlike penams and cephems, monobactams do not have any ring fused to its four-member lactam structure. Monobactam antibiotics are bactericidal, and act by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls. The peptidoglycan layer is important for cell wall structural integrity, especially in Gram-positive organisms.
Drug Class
Cephalosporins are a class of beta-lactam antibiotics, containing the beta-lactam ring fused with a dihydrothiazolidine ring. Together with cephamycins they belong to a sub-group called cephems. Cephalosporin are bactericidal, and act by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls. The peptidoglycan layer is important for cell wall structural integrity, especially in Gram-positive organisms.
Drug Class
Penams, often referred to as penicillins, are a group of antibiotics derived from Penicillium fungi. Penicillin antibiotics are historically significant because they are the first drugs that were effective against many previously serious diseases such as syphilis and Staphylococcus infections. Penicillins are still widely used today, though many types of bacteria are now resistant. All penicillins are beta-lactam antibiotics in the penam sub-group, and are used in the treatment of bacterial infections caused by susceptible, usually Gram-positive, organisms.
Drug Class
Penems are a class of unsaturated beta-lactam antibiotics with a broad spectrum of antibacterial activity and have a structure which renders them highly resistant to beta-lactamases. All penems are all synthetically made and act by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls. They are structurally similar to carbapenems, however, where carbapenems have a carbon, penems have a sulfur.
Resistance Mechanism
Enzymatic inactivation of antibiotic to confer drug resistance.