Antimicrobial Stewardship

What is an Antimicrobial Stewardship Program?

Antimicrobial stewardship programs in hospitals seek to optimize antibiotics prescribing to improve patient care, reduce hospital expenses and slow the spread of antibiotic resistance. With antibiotic resistance on the rise globally and few new drugs in development, antimicrobial stewardship programs are more important than ever in ensuring the continued efficacy of available antimicrobials [1].

What is MRSA?

Methicillin Resistant Staphylococcus aureus, is a dangerous Staph bacterium that is difficult to treat in humans in that it is hard to diagnose and is resistant to penicillin-related antibiotics used to treat ordinary Staph infections [2]. Considered a superbug, MRSA is one of the leading Hospital Acquired Infections (HAI) – targeting those who have been hospitalized or who are in outpatient centers receiving invasive procedures or long-term care. Because MRSA is difficult to treat, the infection spreads easily and can become life threatening, particularly for at-risk people, such as the elderly, the very young, and those with compromised immune systems [3].

The difficulty in accurately diagnosing MRSA has led to the wide-scale use of Vancomycin to all unstable patients suspected of having a Staph infection. Vancomycin is a powerful antibiotic that has a risk of nephrotoxicity when given in high doses intravenously. While Vancomycin has been considered the treatment standard for MRSA infections, over-use of the antibiotic has been cited as one possible reason for its documented clinical failure in treating MRSA [4].

What is CoNS?

Coagulase-negative Staphylococcus. CoNS is an organism found all over the human body. It is part of the normal flora of human skin and is typically non-pathogenic. An example is S. epidermidis, which is present on all skin, and will create a positive blood culture result if the skin is not thoroughly cleansed prior to the blood draw [5].

Why should we care about CoNS?

CoNS can signal a positive blood culture because of external contamination and not an infection in the patient’s bloodstream. S. lugdunensis is highly virulent CoNS that is always considered a true pathogen when isolated from positive blood cultures. Unfortunately, most rapid diagnostic tests on the market do not distinguish the pathogen S. lugdunensis from other non-pathogenic CoNS, which has contributed to the widespread misuse of antibiotics in hospital settings and increased healthcare costs.

What is the prevalence of the pathogenic versus non-pathogenic CoNS?

S. lugdunensis, a pathogenic CoNS, is a clinically significant HAI that, while low in prevalence, is challenging to treat due to the frequency with which it is resistant to penicillin (90-95% of the time) and methicillin (80% of the time). Patients at risk of S. lugdunensis are those with catheters and implanted medical devices. Non-pathogenic CoNS, which constitute most CoNS, is considered relatively avirulent and does not require antibiotic treatment [6]. Due to the lack of adequate diagnostic testing to determine whether a patient has non-pathogenic CoNS or a true pathogen, patients are empirically treated with antibiotics as standard protocol, adding to a significant global problem in over-prescription of antibiotics.


[1] MacDougall, C. & Polk, R.E., “Antimicrobial Stewardship Programs in Health Care Systems,” October 2005. [Online].
Available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1265911/. [Accessed 31 October 2016].
[2] Mayo Clinic, “MRSA Infection,” 20 October 2016. [Online].
Available: http://www.mayoclinic.org/diseases-conditions/mrsa/basics/symptoms/con-20024479.
[3] The Center for Disease Control and Prevention, “Methicillin-resistant Staphylococcus aureus (MRSA),” 20 October 2016. [Online].
Available: http://www.cdc.gov/mrsa/community/index.html.
[4] Micek, S.T., “Alternatives to Vancomycin for the Treatment of Methicillin-Resistant Staphylococcus aureus Infections,” 20 October 2016. [Online].
Available: http://cid.oxfordjournals.org/content/45/Supplement_3/S184.long.
[5] Hall, K.K., Lyman, J.A., “Updated Review of Blood Culture Contamination,” Clinical Microbiology Reviews, vol.19, no. 4, pp. 788-802, 2006.
[6] Tufariello, J.M. and Lowy, F.D., “Treatment of infections due to coagulase-negative staphylococci,” 24 October 2016. [Online]. Available: http://www.uptodate.com/contents/treatment-of-infections-due-to-coagulase-negative-staphylococci.