* Active against gram-negative species including aerobic species such as ''Pseudomonas aeruginosa''.
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* Active against gram-positives (doesn't work that well against Streptococcal species and enterococci.)
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* Works well against Mycoplasmas and Rickettsia.
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* Poor activity against obligate anaerobes.
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* Their activity is very pH dependent wit their activity increasing above pH 7.4 and decreasing below pH 7.0.
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It should be noted that they are active at very low concentrations, they don't kill protective enterococci and anaerobes, and they will inhibit aminoglycoside and beta-lactam resistant bacteria.