CITATION: Baird RW. 1997. Antibiotic prescribing, controls and antimicrobial resistance: an Australian experience. APUA Newsletter 15(4): 1-2,6.


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Antibiotic prescribing, controls and antimicrobial resistance: an Australian experience
Robert W Baird
Melbourne Pathology, Collingwood, VIC Australia

The development of antibiotic resistance is often dependent upon the amount and type of antimicrobial prescribed. Australia is in what appears superficially to be an incongruous position of having a high level of outpatient antimicrobial use compared to other developed countries (1), while at the same time reporting paradoxically lower levels of the antibiotic-resistant nosocomial pathogens and community bacteria that plague other developed nations.

Antibiotic Prescribing
Recent published data from a variety of local sources revealed that compared with other developed countries, Australia has a high national rate of antibiotic use (Figure 1). Retail sales of antibiotics in Australia in 1994 were approximately 25 defined-daily-doses/1000 population/day as compared to 24 in the United States, 16 in the United Kingdom, and 11 in West Germany. In contrast to increasing antibiotic use in many other developed countries, Australia's rate of oral antibiotics use has not altered significantly since 1989.

Australia's 5 most commonly prescribed antimicrobials (1) are
amoxicillin, amoxicillin/clavulanate, cefaclor, doxycycline and cephalexin. The first 4 antibiotics are predominantly prescribed for respiratory tract infections including sinusitis, bronchitis, and otitis media. Cephalexin is primarily prescribed for urinary tract, skin and soft tissue infections. Australia prescribes proportionally less fluoroquinolones than other developed countries due to prescribing restrictions, and a proportionally higher percentage of tetracyclines, possibly due to their widespread use in treating acne.

Antimicrobial Resistance Surveillance
Monitoring of bacterial resistance to antimicrobials was formalized in 1991 under the auspices of the Expert Panel on Antibiotics of the National Health and Medical Research Council. This replaced previous voluntary state reporting schemes, although additional data are still collected by state, industry and professional groups. As this system matures it provides dependable national data on significant resistance patterns. An interpretive snapshot of Australia's current levels of antimicrobial resistance in several common community and nosocomial pathogens was collated by the National Antimicrobial Resistance Surveillance Program (NASRP) (2). These data show patterns of gradually increasing resistance of all common pathogens to antimicrobials with wide geographical variation in resistance rates for both community and nosocomial pathogens. This trend parallels those overseas, though fortunately the actual resistance rates appear to lag several years behind.

Community Pathogens
Streptococcus pneumoniae. Recent NASRP data reveal penicillin resistance rates of 4% nationally, with pockets of higher resistance In some Aboriginal communities. Erythromycin resistance in S. pneumoniae is 10. 7 % and tetracycline resistance 14.3 %.

Escherichia coli. Ampicillin resistance in E. coli is now 44% in isolates from community acquired urinary tract infections. Cephalexin or trimethoprim are now advocated as the standard outpatient therapy of uncomplicated urinary tract infection.
Streptococcus pyogenes. Erythromycin resistance occurs in 5.% of isolates and tetracycline resistance 24.1 %.
Haemophilus influenzae. Ampicillin resistance occurs in approximately 20% of isolates ranging from 4-38 % in different geographical areas.

Nosocomial Pathogens
Enterococcus species. Vancomycin resistant enterococcal (VRE) isolates were first reported in Australia in 1994. VRE currently occurs at low levels (< 1 %) nosocomially, confined mainly to teaching hospitals, transplant units and intensive care units. Hospital formulary restrictions on oral vancomycin use, use of third generation cephalosporins, and the voluntary usage of prescription guidelines may explain our current low levels of this organism.

Staphylococcus aureus. Methicillin resistance is predominantly confined to S. aureus isolates from nosocomial infections with rates of between 10- 20 % are being seen in S. aureus isolates from teaching hospitals. Resistance to rifampicin and ciprofloxacin is also on the rise. Methicillin resistant S.aureus (MRSA) isolates from geographically isolated Western Australia are usually not multi-drug resistant, unlike those from Eastern Australian states.
Extended-spectrum ß-lactamase producing
Klebsiella sp. Resistance to third generation cephalosporins is becoming increasingly prevalent in Australia with nosocomial isolates of Klebsiella pneumoniae having average resistance levels of 5%, 2% and 4% to cefotaxime, ceftriaxone and ceftazidime, respectively.

Antibiotic controls
Prior to 1975, MRSA comprised less than 2% of all strains of
S.aureus in teaching hospitals (3). A marked increase in cases of MRSA occurring from 1979 -1981 was a seminal event, leading to national media interest and review of infection control procedures. This resulted in formation of an Antibiotic Guidelines Sub-Committee in Victoria which was the first comprehensive Australian initiative to control antimicrobial use. Currently, the prescription of antimicrobials in Australia is controlled on three levels. First, there are financial measures. Prescription drugs in Australia are subsidized by the Federal government through a national Pharmaceutical Benefits Scheme (PBS). This provides a wide range of antimicrobials at internationally cost effective prices. A strict regulatory process is followed for the introduction of new antimicrobials, and restrictions are placed on the prescribing of certain antimicrobials. For instance, the fluoroquinolone, ciprofloxacin, is the only systemically acting quinolone available in Australia, and may be prescribed only for a limited range of indications. This may explain the proportionally low prescription of quinolones in Australia compared to other developed countries.

A second approach to control is educational. Various materials are available to doctors to help them with rational antibiotic selection. These include a small handbook,
Antibiotic Guidelines (4) which covers both outpatient and hospital based antimicrobial prescribing recommendations, including indications for prophylaxis. This guide, now in its ninth edition, is used widely by medical students and practicing physicians. Additional educational initiatives include papers in the Medical Journal of Australia (2) as well as industry and government information and literature such as reports from the National Adverse Reactions reporting scheme. Despite these efforts, however, there remains a significant gap in Australia's educational efforts namely patient education. Patients need to be educated not to request prescriptions for antimicrobials for illnesses which are often of viral etiology, such as common upper respiratory tract disease. To implement this, both patient and legal expectations will need to be challenged.

Lastly, control of antibiotic use is achieved through institutional means. Australia has a two-tiered healthcare system of a universal publicly funded health insurance for all citizens and a private hospital system, with approximately 30% of citizens having additional private insurance. Drug formularies operate throughout the publicly funded hospital system, reducing the prescribing of broad-spectrum, expensive agents such as imipenem. In the late 1980's and early 1990's, drug formularies markedly limited prescribing of third generation cephalosporins. More recently, they restrict oral and parenteral vancomycin use to particular indications.

Australia currently has systems for monitoring antimicrobial resistance in both community and hospital associated bacterial infections (5). In addition, there are effective means of monitoring the prescription of antibiotics. However, the correlation of bacterial resistance patterns with particular antimicrobial prescribing habits must be assessed, both in Australia and internationally. Areas, such as tertiary care facilities, with high levels of antibiotic usage and cross-infection problems, pose a continuing and significant risk for the development of resistance. Therefore, future efforts need to focus on decreasing total antimicrobial prescribing in both hospital and community settings.

References

  1. McManus P, Hammond L, Whicker SD et al. Antibiotic use in the Australian community, 1990-1995. Med J Aust; 167: 124-127.
  2. Turnidge J. Antibiotic use or misuse? Med J Aust . 1997; 167:116-117.
  3. McDonald PJ, Methicillin-resistant staphylococci. A sign of the times. Ed. Med J Aust, 1982 1,11: 445.
  4. Victorian Drug Usage Advisory Committee. Antibiotic Guidelines, 9th edition. Melbourne: Victorian Medical Postgraduate Foundation Therapeutics Committee,1996.
  5. Bell J, Turnidge J. National Antimicrobial Resistance Surveillance Program. 1993 Report. National Health and Medical Research Council, Canberra. 1995.
 

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