Microbial resistance to drug therapy: a review.

Microbial resistance to the antimicrobials in standard use is becoming more prevalent. A historical perspective frames further discussion. Bacterial resistance is most common, but resistance has been identified in fungi, viruses, and parasites. Resistance is a complex phenomenon that involves the microorganism, the environment, and the patient-separately and interactively. Resistance may be a characteristic of the microbe before exposure to a given drug or may arise as a consequence of therapy. Mechanisms of resistance to antibiotics are discussed. Antibiotic resistance is considered in both hospital and community settings, as ecosystems that are separate yet blending, and the major organisms demonstrating significant resistance problems are presented. A review of existing guidelines, strategies, and plans for addressing resistance and some recommendations conclude this review.