Safer use of antimicrobials in hospitals: the value of antimicrobial usage data

Antimicrobial resistance is a major threat to the great advances in treatment of infectious diseases over the past 40 years.1 The relationship between antimicrobials and resistant organisms is complex, encompassing selection and dissemination of resistance determinants between humans and bacterial hosts. Despite difficulties in proving a cause–effect relationship, there is good evidence that overuse and inappropriate use of antimicrobials lead to emergence and dissemination of resistant organisms, with studies showing that resistance rises with increased antimicrobial use and falls after reduced use.1-3 Patients with infections due to resistant bacteria have poorer outcomes, experiencing delayed recovery, treatment failure and even death.4 Inappropriate use of antimicrobials also increases the risk of patient harm from adverse effects such as Clostridium difficile infection, and increases costs to health care and society. Prudent use of antimicrobials is considered central to the control of resistance, and active surveillance of antimicrobial usage is paramount.

Changing antimicrobial use in hospitals is complex and challenging and requires an organised approach, such as an antimicrobial management program, also termed antimicrobial stewardship (AMS). AMS involves a systematic approach to optimising antimicrobial use. Successful hospital AMS programs have been shown to improve the appropriateness of antimicrobial use, and to reduce institutional resistance rates and, in turn, morbidity and mortality.5-10 Together with infection control, hand hygiene and surveillance, AMS is considered a key strategy in local and national programs to decrease preventable health care-associated infections. When supported by hospital management, a decrease in inappropriate use, improved patient outcomes and savings in health care costs can be achieved.5,6,8,9

Hospital AMS programs include a range of different interventions aimed at improving antimicrobial prescribing. One of the essential components of an AMS program is monitoring antimicrobial usage11 to:

• identify trends in prescribing that require further investigation through targeted audits;

• measure the effect of stewardship activities, including cost savings; and

• provide feedback to prescribers (one of the most effective interventions to influence prescribing behaviour).

The monitoring of antimicrobial usage is also critical to understanding antimicrobial resistance by linking patterns of usage with the emergence of resistant organisms. Box 1 provides an example of the temporal relationship between the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) and the use of antimicrobial agents known to induce methicillin resistance.

There are two main methods of antimicrobial data collection: patient-level surveillance and population surveillance.13

Patient-level surveillance involves collecting data about the dosage and duration of therapy for individual patients. This approach gives the most accurate information, particularly if the aim is to link excessive antimicrobial use with development of resistance in a particular area of practice.

Population-level surveillance data are aggregated antimicrobial use data. The data are generally derived from the volume of antimicrobial agents issued to wards and clinical units or from individual patient prescription data from pharmacy reports summarised at the level of a hospital or unit. Although not as accurate as patient-level surveillance, population-level surveillance is currently the only realistic option for ongoing, systematic monitoring of antimicrobial use.

Comprehensive data at individual patient level are not available from most hospitals in Australia, and aggregate data from issues to wards combined with individual patient dispensing records are most commonly used.1 Here, we discuss how population surveillance data can be used to drive safety and quality improvement in hospital practice.

National antimicrobial usage data allows contributing hospitals to compare their usage with peer-group hospitals, identify trends in prescribing requiring further investigation and measure the effectiveness of AMS programs, including cost savings. The regular feedback is a useful tool for educating prescribers and monitoring the effect of targeted interventions. Overall high usage has been used by hospitals and area health services as a stimulus for initiation or expansion of AMS programs.

There is potential to further utilise the data, including linking longitudinal usage data with resistance data, at national and hospital levels, to identify reduction in resistant organisms and emerging patterns of resistance.

Comparison of national usage data with international data indicates that Australian hospitals are relatively high users of antimicrobials when compared with their northern European counterparts. The national focus on implementing AMS programs in hospitals, which is led by the Australian Commission on Safety and Quality in Health Care, is aimed at improving patient safety by reducing inappropriate antimicrobial prescribing and by reducing health care-associated infections from resistant organisms. Antimicrobial usage data, such as that provided through NAUSP, will be useful for monitoring the effect of these programs on influencing antimicrobial prescribing at hospital, state and territory, and national levels.

1 Monthly rates of methicillin-resistant Staphylococcus aureus (MRSA) infection and monthly antimicrobial use, Aberdeen Royal Infirmary, Scotland, January 1996 – December 200012

2 Meropenem use in a non-intensive care unit setting (Case study 1)

OBD = occupied bed-days.

3 Ceftriaxone usage over 8 years at a major teaching hospital in South Australia (Case study 2)

OBD = occupied bed-days.

4 Usage of carbapenems and third-generation cephalosporins over 4 years illustrating the effect of implementing an AMS program (Case study 3)

AMS = antimicrobial stewardship. OBD = occupied bed days.