Topically applied antibacterial agents are widely used. Opinions regarding the clinical efficacy of topical antibiotics are conflicting, and for most indications, alternative oral therapies are available. Topical application has many potential advantages over systemic therapy that includes high and sustained concentrations of drug directly at the infected site, low quantity of antibiotic needed, better compliance, fewer systemic side effects and potentially less chance of antimicrobial resistance. Despite these advantages, an important concern has been the difficulty in monitoring antibiotic dosage and duration of therapy. Most topical preparations are applied on sites with pre-existing normal bacterial flora, and the detrimental effect of antibiotic on the 'good' bacteria is difficult to control. Unnecessary exposure of the resident microflora to high drug levels may select drug-resistant phenotypes. The number of antibiotics available and the quality and composition of the formulations recommended for topical drug delivery are improving. Their role in the prevention and treatment of locally invasive infections is established for many clinical conditions. However, there is still a lacuna in the availability of pharmacokinetic (PK) knowledge of these topical preparations and translation of the same to clinical practice. In addition, reporting the clinical outcome following the use of these agents and its analysis considering the recently proposed epidemiological cut-off value-based cut-offs are also areas which merit further research. In this review, we highlight the clinical utility and the PK aspects of topical antimicrobials in various infections. We also discuss the limitations of the current antimicrobial susceptibility testing (AST) protocols and new methods for AMST for topical agents.

中文翻译：

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局部抗菌治疗：现状和挑战。

局部应用的抗菌剂被广泛使用。关于外用抗生素临床疗效的观点是相互矛盾的，对于大多数适应症，可以使用替代口服疗法。与全身治疗相比，局部应用具有许多潜在的优势，包括直接在感染部位提供高且持续的药物浓度、所需抗生素用量低、依从性更好、全身副作用更少以及潜在的抗菌药物耐药性机会更少。尽管有这些优点，一个重要的问题是监测抗生素剂量和治疗持续时间的困难。大多数外用制剂都应用于预先存在正常细菌菌群的部位，抗生素对“好”细菌的有害影响很难控制。常驻微生物群不必要地暴露于高药物水平可能会选择耐药表型。可用抗生素的数量以及推荐用于局部给药的制剂的质量和成分正在改善。它们在预防和治疗局部侵袭性感染中的作用已在许多临床病症中得到证实。然而，这些外用制剂的药代动力学（PK）知识的可用性以及将其转化为临床实践仍然存在缺陷。此外，报告使用这些药物后的临床结果及其考虑最近提出的基于流行病学临界值的分析的分析也是值得进一步研究的领域。在这篇综述中，我们重点介绍了外用抗菌药物在各种感染中的临床效用和 PK 方面。我们还讨论了当前抗菌药物敏感性测试 (AST) 方案的局限性以及外用药物 AMST 的新方法。