Best laboratory practices for respiratory cultures

Respiratory specimens for culture are one of the most common test requests received in the clinical microbiology laboratory and often the most difficult to evaluate. Samples are frequently contaminated with resident upper airway flora, and it is often difficult to determine which organisms represent potential pathogens. These challenges often result in time and resources being spent to assess and report cultures that may provide little clinical value. In addition, working up and reporting results from mixed cultures may generate clinically misleading information that leads to inappropriate and unnecessary antimicrobial therapy.This article discusses the evaluation and reporting of results on respiratory samples beginning with the direct specimen Gram stain through culture. It describes a clinically relevant interpretation and reporting scheme for direct specimen Gram stains, reviews the use of the direct Gram stain to guide respiratory culture workup, and provides several logical and easy-to-follow strategies that can be employed in the laboratory to ensure that results are clinically relevant and culture examination and work up are consistent among technologists.