To the Editor—The spread of drug-resistant pathogens and a lack of novel antimicrobial agents impact human health worldwide. Consequently, antimicrobial stewardship (AS) strategies that conserve the utility of existing antimicrobials and enhance appropriate drug use are of significant importance. Current and widespread interest in AS is reflected by recent governmental statements supporting the expansion of AS initiatives and by a recent white paper from the Society for Healthcare Epidemiology of America that provides guidance for the knowledge and skills required for AS leaders. ^{1 ,} Reference Cosgrove, Hermsen, Rybak, File, Parker and Barlam ² In directing AS efforts, evidence-based interventions are required to ensure the most efficient use of available resources.

A guideline for the development of an institutional program to enhance AS was published in 2007 by the Infectious Diseases Society of America and the Society for Healthcare Epidemiology of America.Reference Dellit, Owens and McGowan ³ Additionally, several reviews have been published on the topic.Reference Wagner, Filice and Drekonja ^{4 ,} Reference Leuthner and Doern ⁵ Such publications provide a detailed analysis and perspective of the literature, but opportunity exists to provide a more global perspective on the status of this area of research. The purpose of this letter is to complement existing literature, document trends in practice, elucidate knowledge gaps, and identify future needs by objectively describing characteristics of original AS research from 2000 to 2013.

A structured literature search utilizing PubMed (http://www.ncbi.nlm.nih.gov/pubmed) was performed in August 2014 using the term “antimicrobial stewardship” to identify existing publications within this area of study. Search filters included the following: abstract available, human species, English language, and publication date from January 1, 2000, through December 31, 2013. Search results were exported into a spreadsheet (Excel; Microsoft) and publications were individually assessed. Non-primary literature and publications not investigating an AS strategy were excluded from the analysis. Remaining studies were assessed for the following characteristics: year of publication, journal title, journal profession affiliation(s), author profession(s), location(s) of research, institution type, study focus, and financial data. Journal profession affiliations were determined by reviewing online journal descriptions. The 2007 Infectious Diseases Society of America/ Society for Healthcare Epidemiology of America AS Guideline was used to define and categorize the AS strategy or strategies investigated within each publication.

The literature search identified 305 unique publications, of which 88 (29%) were found to be primary literature investigating an AS strategy. Figure 1 denotes the quantity of AS literature produced annually during the study period. No studies published before 2007 met inclusion criteria, yet the number of included publications gradually increased thereafter. North America produced the largest number of publications (n=58), followed by Europe (n=14), Asia (n=12), South America (n=2), Africa (n=1), and Australia (n=1). The United States was the country with the most publications (n=56). In regards to setting, of the 88 studies, 53 (60%) were conducted in a teaching hospital, 23 (26%) were conducted in a community hospital, 4 (5%) were conducted in a long-term care setting, and 8 (10%) did not fall into one of these specific setting categories. Four publications (5%) were specifically focused on pediatric populations.

Figure 1 Annual publications in the field of “antimicrobial stewardship” from 2000 through 2013.

Thirty-six unique journals published at least 1 included study, and Infection Control and Hospital Epidemiology published the most articles (n=14). The medical (n=47) and pharmacy (n=18) disciplines were the most common journal professional affiliations identified. Analysis of author disciplines identified 55 interprofessional collaborations, of which 48 featured at least 1 physician and 1 pharmacist.

All AS core and supplemental elements were found to have been studied, with 55 publications investigating multiple strategies and 33 investigating a single strategy. The most common strategies investigated were guidelines and clinical pathways (n=29) and prospective audit with intervention and feedback (n=24). The least common strategies investigated were antimicrobial cycling (n=3), combination therapy (n=3), and antimicrobial order forms (n=1). In regards to which therapies were targeted, 51 studies (58%) addressed antibacterials, 9 (10%) addressed antifungals, 3 (3%) addressed antivirals, and 25 (28%) had no particular focus. In regards to which pathogens were targeted, 35 studies (40%) focused on a specific organism or group of organisms. The most commonly targeted pathogen was Clostridium difficile (n=10 studies).

For economic end points, 31 studies (35%) discussed financial implications, of which 27 (87%) provided objective financial end point data. Cost savings was reported by 24 studies, 2 studies reported a neutral economic impact, and 1 study reported increased costs. For funding, 41 studies (47%) provided a direct funding source, 30 studies (34%) did not provide a funding disclosure, and 17 studies (19%) were stated to be unfunded.

These data show that a large number of journals have interest in AS, interprofessional collaboration within AS research is frequent, funding exists to perform AS-related research, and AS literature has increased precipitously over the past 10 years. However, the availability of primary literature in this area remains limited and many opportunities exist to expand on current knowledge. For example, data show expansion of research is needed within pediatric populations and long-term care locations. Furthermore, several AS strategies are particularly in need of study (eg, antimicrobial order forms).

Study limitations include a search restricted to the English language and query of only 1 database. A more extensive search may have provided additional primary publications. In addition, the term “antimicrobial stewardship” has become mainstream only in the past decade or so. It is possible that AS was simply not mentioned or was identified by alternative means in non-included publications, resulting in an underrepresentation of the literature.

As AS becomes further integrated into healthcare delivery systems, implementation of research initiatives to fill existing knowledge gaps is essential to elucidating the optimal management of potential AS endeavors. Development of an interprofessional journal or journal sections for AS-specific content may soon be warranted.