Antimicrobial resistance is recognized as one of the greatest threats to human health worldwide [1]. Drugresistant infections take a staggering toll in the United States (US) and across the globe. Just one organism, methicillin-resistant Staphylococcus aureus (MRSA), kills more Americans every year (19,000) than emphysema, HIV/AIDS, Parkinson's disease, and homicide combined [2]. Almost 2 million Americans per year develop hospital-acquired infections (HAIs), resulting in 99,000 deaths [3], the vast majority of which are due to antibacterial (antibiotic)-resistant pathogens. Indeed, two common HAIs alone (sepsis and pneumonia) killed nearly 50,000 Americans and cost the US health care system more than $8 billion in 2006 [4]. In a recent survey, approximately half of patients in more than 1,000 intensive care units in 75 countries suffered from an infection, and infected patients had twice the risk of dying in the hospital as uninfected patients [5]. Based on studies of the costs of infections caused by antibiotic-resistant pathogens versus

Antimicrobial stewardship is a bundle of integrated interventions employed to optimize the use of antimicrobials in health care settings. While infectious-disease-trained physicians, with clinical pharmacists, are considered the main leaders of antimicrobial stewardship programs, clinical microbiologists can play a key role in these programs. This review is intended to provide a comprehensive discussion of the different components of antimicrobial stewardship in which microbiology laboratories and clinical microbiologists can make significant contributions, including cumulative antimicrobial susceptibility reports, enhanced culture and susceptibility reports, guidance in the preanalytic phase, rapid diagnostic test availability, provider education, and alert and surveillance systems. In reviewing this material, we emphasize how the rapid, and especially the recent, evolution of clinical microbiology has reinforced the importance of clinical microbiologists' collaboration with antimicrobial stewardship programs.

Can the use of serum procalcitonin levels safely reduce antimicrobial use in intensive care unit (ICU) patients? We performed a systematic literature review that identified 6 published randomized controlled trials comparing PCT-guided antimicrobial therapy to usual care in ICU patients, extracting data on ICU and patient characteristics, PCT guideline content, intensity of antimicrobial exposure, ICU length of stay, infection relapse, and mortality. Procalcitonin guidance was associated with significantly reduced antimicrobial exposure (effect sizes, 19.5%-38%) in all 5 studies assessing its impact on treatment duration but did not significantly impact antimicrobial exposure in the study assessing treatment initiation only. Length of ICU stay was significantly decreased in 2 studies but was unchanged in the others. Neither infection relapse nor mortality varied significantly in any of the studies. Procalcitonin guidance of antimicrobial duration appears to decrease antimicrobial use in the ICU safely and significantly and may also decrease the length of stay in the ICU.