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Principles of rational antibiotic use

A video outlining the principles of rational antibiotic use by Dr Philip Oshun.
Today we will be discussing principles of rational antibiotic use. Antibiotics can be used for treatment or prophylaxis. For treatment, it can be empiric or definitive therapy. Empiric antibiotic therapy provides an initial control of infection based on suspected organisms that may cause the infection, while definitive therapy is directed towards a known organism with antimicrobial sensitivity results. There are some questions to ask before commencing an empiric therapy. The first question is, is there good clinical evidence of infection? This can be ascertained using the total white cell count, procalcitonin, C reactive protein and clinical signs and symptoms of infection. With bacterial infections, the total white cell counts is usually increased with increased neutrophil count.
The procalcitonin or serum reactive protein may also be elevated in bacterial infection. The second question is, what are the likely causative organisms? And will these organisms respond to antimicrobial therapy?
Based on the clinical signs and symptoms, with laboratory test results and also knowing the site of infection. For example, urinary tract infections are caused by Gram negative bacilli, which are part of the intestinal flora. For example, E coli, Klebsiella and Proteus. Viral infections of the respiratory tract and viral diarrhoea would not respond to antibiotic therapy and so should not be treated with antibiotics. The third question is, has the relevant samples been collected for culture and other laboratory tests included antigen and antibody testing?
Ideally, cultures should be taken before commencement of antibiotic therapy. There’s need to assess the severity of the infection to determine whether a patient is critically ill or stable. This will affect the timing, dose, frequency, and route of administration of antibiotics.
When all these questions have been answered, we need to choose the appropriate antibiotics with respect to the dose, route of administration, and duration of therapy. This choice will depend on the host factor of the patient and previous antibiotic treatment. Those factors will include age, underlying diseases, drug allergy, and severity of illness. The elderly tend to metabolise and excrete antibiotics more slowly. An antibiotic with significant toxicity, like gentamicin, is avoided in the elderly. It’s also important to take into account liver or renal diseases and make those adjustments accordingly. It is important to determine the likelihood of antibiotic resistance in a patient.
The factors to look out for will include recent antibiotic use, local antibiotic sensitivity pattern, and prior exposure to the health care facility. Depending on the severity of infection and the spectrum of disease that may cause the infection, empiric antibiotic therapy may be commenced with broad spectrum antibiotics, which can be changed to a narrower spectrum antibodies when microbiology results become available. Use of multiple antibiotics for treating infections may result in antagonism of antibiotics. It may also increase the risk of infection with highly resistant organisms. It may increase the risk of adverse events and also increase the costs and risk for administration errors. However, in some cases, like penicillin and aminoglycoside for the treatment of Enterococcal infections, this combination may be synergistic.
Within three days of commencing antimicrobial therapy, there should be a review of the results of microbiology data. By this time, the bacteria causing the infection would have been identified and antibiotic sensitivity results determined.
So it’s important to reevaluate antibiotic therapy based on clinical response and microbiology data. This is called ‘antimicrobial time out’ or ‘antibiotic time out’. There may be a need to deescalate or streamline the antibiotics. Then we need to escalate or discontinue antibiotics. Antibiotics will be discontinued if results shows that there’s no evidence of infection or an alternative non infective diagnosis has been made. Antibiotics may be escalated to more broad spectrum antibiotics if there is multi-drug resistance.
Deescalation of antibiotics or streamlining of antibiotics involves switching to a narrower spectrum antibiotic based on the sensitivity testing. It also involves optimising the dose of the antibiotics, changing the routes of antibiotics, for example, from IV to oral antibiotics, and also considering adverse effect of antibiotics based on those factors.
Thereafter the duration of treatment needs to be determined and planned, usually based on available treatment guidelines.

As we have seen the increase in antibiotic misuse has led to the increase in antibiotic resistance.

In this video Dr Philip Oshun, Clinical Microbiologist, Infection Control Practitioner MBChB, MPH MSc, FMCPath, explains how this increase can be prevented by the rational use of antibiotics.

He expands on the key messages provided by Professor Marc Mendelson in steps 1.13 & 1.15

This article is from the free online

Antimicrobial Stewardship for Africa

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