Clinical tips: antimicrobial resistance

Louis Roller takes a look at the progression of antibiotic resistance… and what pharmacists can do to help stop it

“We will not find an antibiotic which will not also have a resistance gene out there.”
                                                                        Nature. 2011; 31;477:457-61.

The development of antibiotics in the 1940s and 50s was one of the most important advances of medicine. Many bacterial infections that had previously had no effective treatment and often caused significant morbidity and mortality, became treatable with antibiotics, saving millions of lives.

Now, because of the overuse and misuse of antibiotics, bacterial infections that were once easily cured with antibiotics are becoming harder to treat. This is due to antibiotic resistance.

Antibiotic resistance occurs when bacteria change to protect themselves from an antibiotic; they are then no longer sensitive to that antibiotic. When this happens, antibiotics that previously would have killed, or inhibited, the bacteria are no longer effective.

The effects of antibiotic resistance:

  • Using antibiotics when not needed may mean that they won’t work when needed in the future.
  • An antibiotic-resistant bacterial infection will prolong the infection which is likely to lead to more complications of the infection.
  • The infected person could remain infectious for longer, and pass the infection to other people, which increases the problem.

Many people still believe that antibiotics can cure a cold or flu and will help to shorten their illness. This is obviously false, because most respiratory tract infections are caused by viruses, so antibiotics won’t have any effect.

The World Health Organisation (WHO) has called antibiotic resistance one of the biggest threats to human health today.

“Antimicrobial resistance (AMR) threatens the effective prevention and treatment of an ever-increasing range of infections caused by bacteria, parasites, viruses and fungi.

“An increasing number of governments around the world are devoting efforts to a problem so serious that it threatens the achievements of modern medicine.

“A post-antibiotic era – in which common infections and minor injuries can kill – far from being an apocalyptic fantasy, is instead a very real possibility for the 21st Century.”

A utilisation review of the PBS/RPBS for Oct 2014 and Feb 2015 found that:

  • 45% of the Australian population were supplied at least one antibiotic through the PBS.
  • There were over 26 million prescriptions supplied for systemic antibiotics through the PBS.
  • There were more than 29 million prescriptions supplied for any antibiotic (including systemic and topical antibiotics) through the PBS.
  • The most commonly supplied antibiotics were amoxycillin (almost 6 million), cephalexin (over 5 million), and amoxycillin plus clavulanic acid (almost 5 million).
  • The defined daily dose (DDD)was calculated to be 22.8 DDD/1000/day. This is higher than the OECD average of 21.1.
  • $116.5 million in PBS/RPBS benefits was paid for antibiotics.
  • For commonly used systemic antibiotics (amoxycillin, cephalexin, roxithromycin and amoxycillin with clavulanic acid): -repeats were ordered on the majority of prescriptions for cephalexin,amoxycillin with clavulanic acid and roxithromycin; repeats were written on 40% of amoxycillin original prescriptions; the majority of repeats ordered were not dispensed; some original prescriptions and repeats were dispensed long after the date the prescription was written. This use may not be consistent with the original reason for the prescription.

The more that antibiotics are used, the greater the chances bacteria have to become resistant to them.

Major causes of antibiotic resistance include:

  • Using antibiotics when they are not needed.
  • Not taking antibiotics at the doses and times prescribed — this allows time for the bacteria in body to become resistant.

Antibiotics are also often overused in animals (in veterinary medicine and in agriculture which further compounds the situation.

Resistance to antibiotics may occur by: genetic predisposition, low concentrations of antimicrobial and/or transfer of genetic material

Multi-drug resistance (MDR), is a condition enabling disease-causing microorganisms (bacteria, viruses, fungi or parasites) to resist distinct antimicrobials, first and foremost antibiotics, but also antifungal drugs, antiviral antiparasitic medications and other chemicals of a wide variety of structure and function targeted at eradicating the organism.

Some examples of antibiotic resistance include the following:

  • Staphylococcus aureus resistance to penicillin.
  • methicillin-resistant Staphylococcus aureus (MRSA).
  • ampicillin-resistant Eschericha coli, Haemophilus influenza and Neisseria gonorrhoeae.
  • gentamicin-resistant Enterococcus faecalis.
  • cephalosporin-resistant Klebsiella pneumonia.
  • vancomycin-resistant Staphylococcus aureus (VRSA), Enterococcus faecum (VRE).
  • extended spectrum beta-lactamase (ESBL) resistance to Klebsiella pneumonia, Serratia marcescens, Enterobacteriaceae, Pseudomonas aeruginosa.
  • ciprofloxacin-resistant Eschericha coli, Pseudomonas aeruginosa.
  • multidrug resistant Mycobacterium tuberculosis, Shigella.
  • linezolid-resistant Staphylococcus aureus.

Antibiotic stewardship is a strategy; a coherent set of actions which promote using antimicrobials responsibly.

Antimicrobial stewardship in community, inpatient and/or or outpatient setting, ie,

  • appropriate antibiotic;
  • correct dose; and
  • optimal duration.

Pharmacists can educate the public to help prevent antibiotic resistance by:

  • Understanding that most people don’t need antibiotics for colds and flu because they are caused by viruses.
  • Asking for an antibiotic only if it is really necessary.
  • Taking the right dose of the antibiotic at the right time, as prescribed.
  • Taking antibiotics for as long as the prescriber says.
  • Avoid infections and prevent them from spreading.

Long courses may be indicated for severe infections.

However, short courses appropriate, for example:

  • Treatment of UTIs in women.
  • Treatment of uncomplicated cellulitis.
  • Evidence for duration of antibiotic courses is needed.

Patient advice

  • complete the course as specified;
  • be specific on the label;
  • avoid “until all finished” if appropriate;
  • dispose of any remaining antibiotics or only provide the specified duration of antibiotics;
  • void filling or keeping repeat prescriptions;
  • question patients returning to fill a repeat after a long period; and
  • don’t share any antibiotics with another person.

Therapeutic Guidelines: Antibiotic, Version 15, 2014

 Associate Professor Louis Roller, from the Faculty of Pharmacy and Pharmaceutical Sciences Monash University, was the 2014 recipient of the PSA Lifetime Achievement Award.

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