Increasing rates of resistance to antimicrobials among hospital pathogens is a worldwide problem that has been recognized for more than 20 years. The spread within the last 10 years of Extended Spectrum Beta Lactamase producing Enterobacteriaceae (ESBL-PE), and recently Carbapenemase producing Enterobacteriaceae (CPE) and the role of antimicrobial consumption (ref) in the increasing of this phenomenon, underline the emergency of implementation of antimicrobial stewardship program before and during outbreak episodes concomitantly with infection control measures. Patterns of consumption of different classes of antibiotics classes have been closely correlated with the emergence of bacteria resistant to those classes [1,2].Consequently, many publications have suggested the importance of antimicrobial stewardship to avoid  and to control [4,5] the emergence of antibiotic resistance.The main purpose of antimicrobial stewardship programs is to improve how antibiotics are used, in order to optimize clinical outcomes while minimizing unintended consequences of antimicrobial use, including toxicity, the selection of pathogenic organisms (such as Clostridium difficile), and the emergence of resistance . Since at least a third of antibiotic use is usually inappropriate or unnecessary in most hospital settings, antibiotic stewardship programs lead to reductions in total antibiotic consumption.
2. Antimicrobial stewardship programs: definitions and objectives.
Several terms have been used to describe antimicrobial stewardship programs (ASPs) such as antibiotic policies, antibiotic management programs or antibiotic control policies. They all refer to an effort by the healthcare institution (as a whole) to optimize antimicrobial use among hospitalized patients in order to improve patient outcomes and to reduce antimicrobial resistance.
The main objectives of ASPs could be summarised as:
An advisable step before development of any program is to first attempt to define the most important issues that exist with respect to antimicrobial use within a given healthcare institution. Once institution-specific problems have been identified, it is important to evaluate potential causes and solutions. As part of this, any existing antibiotic recommendations and policies should be reviewed.
3. Antimicrobials stewardship components.
3.1. In case of an outbreak, when should we implement an ASP?
Many publications suggest that ASPs can help to control the spread of resistant microorganisms. The most convincing evidence of an effect on antimicrobial resistance rates was provided by studies aimed at reducing the incidence of Clostridium difficile associated disease . However, use of specific antibiotic classes seems to be correlated with a higher incidence of certain microorganisms, suggesting that close monitoring of their specific consumption could help to contain outbreaks [2,16].
4. Evaluating antimicrobial stewardship programs.
From an infection control point of view, the most relevant goal to be assessed may be the ecological effects of the ASP. In this context, the main objectives of the ASP may be to reduce antimicrobial collateral damage, such as Clostridium difficile associated diarrhea, or avoiding multi drug resistance microorganisms.
A major consideration when measuring resistance is choosing which types of specimens to include. Four main options are possible:
Measurements of antibiotic use are an essential component of ASPs, and provide data for assessing the impact of ASP interventions. The most commonly used metric for measuring aggregated antibiotic use is the defined daily dose (DDD) proposed by the World Health Organization, expressed as DDD per 1000 patient-days. This measure allows comparisons between institutions. However, it underestimates the real consumption in some populations, such as children and patients with renal failure. Others methods that can be used include days of therapy for each antibiotic administered, and total length of therapy.
Studies  have shown that early reassessment of antibiotic therapy after 24-48 hours is an important step towards appropriate use of antibiotics. This may be focused on appropriateness of antibiotics used according to local clinical guidelines or available microbiological results. Rates of early switching to oral antibiotic therapies can also be used to evaluate ASPs.
All of these data may be collected on a hospital-wide basis as part of regular point prevalence studies within the ASP.
Original contribution from Jean Ralph Zahar (Unitéd' Hygiène Hospitalière, CHU Angers)