Gram-positive/negative bacteria beta-lactam antibiotics

Monobactams like aztreonam are monocyclic, as opposed to bicyclic, beta-lactam antibiotics. They are beta-lactamase-resistant. The monobactams are active against gram negative rods but lack activity against gram positive bacteria or against anaerobes. They are administered intravenously and they are rapidly excreted in the urine. 

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