A 55-year-old female nonsmoker presented to her local emergency department with a 2-day history of fever, hemoptysis, and shortness of breath. She was previously healthy except for type 2 diabetes that was controlled with diet and metformin. Upon admission to the hospital the woman was hypoxic, with an oxygen saturation of 89% on room air, and in obvious respiratory distress, with decreased breath sounds over the base of her right lung. Her white blood cell count was 100 cells/µL and a chest x-ray revealed a right lower lobe infiltrate with effusion. She was admitted to the intensive care unit (ICU) with sepsis, severe pneumonia, and adult respiratory distress syndrome. She was started on levofloxacin but did not improve and required ventilatory support. This very sick woman was not a stranger to the ICU, for she was an ICU nurse who worked at another hospital. 
The discovery of antibiotics and their widespread application in healthcare early in the 20th century was doubtless one of the most pivotal events in the history of medicine. The practice of medicine was no longer limited to diagnosing disease; with this new and formidable weapon, many diseases could be treated and cured. It appeared that bacteria could be stopped from causing severe illness and death in humans.
This jubilance was short-lived. It was not long before bacteria revealed their remarkable ability to evolve and evade destruction, a phenomenon known as antimicrobial resistance.As antibiotics were increasingly used to treat illness, the degree and complexity of antimicrobial resistance also grew.An entire pool of antimicrobial resistance genes developed to provide a ready supply of mechanisms that allowed microorganisms to swiftly outmaneuver each new antibiotic that came along.
Just like bacteria, viruses, parasites, and fungi also can learn to survive and multiply, even in the presence of agents that previously would have killed them or suppressed their growth. Antimicrobial resistance has become so significant a problem that it is now considered one of the greatest threats to human health.
Medscape Nurses © 2010 WebMD, LLC
Cite this: Laura A. Stokowski. Antimicrobial Resistance: A Primer - Medscape - Sep 27, 2010.