There are several beta lactam agents with potent activity against Pseudomonas aeruginosa. While several can attain a resistance-suppression target in the blood, few, if any can attain such a target for an acceptable fraction of patients at the infection site where a dense population of organisms exists, such as in a patient with Ventilator-Associated-Pneumonia (VAP). Combination chemotherapy allows additive to synergistic interaction for bacterial cell kill in most instances and suppresses amplification of resistant subpopulations. Multi-resistant Pseudomonas and Acinetobacter spp are an area where the extra toxicity and expense of combination agent therapy may be worth it.
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