Pharmacy OneSource Blog

Antibiotic Use and Outcomes on Resistance Development and Persistence

Uniquely among medications, antibiotics affect not just the individuals who take them, but as a consequence of antibiotic resistance, potentially affect other individuals in the community and around the world.

Bacteria can develop resistance to an antibiotic to which they, or other bacteria in the local environment, are exposed. According to Anna Zorzet, PhD, of Action on Antibiotic Resistance (ReAct) and the Department of Medical Sciences at Uppsala University in Sweden, resistance to different antibiotics is found on genetic elements on bacteria, which can lead to bacteria’s resistance of multiple antibiotics at once.1

Use of any antibiotic can increase the risk of developing a multidrug resistant organism (MDRO)–not just a resistant version of the targeted pathogen, but potentially a resistance form of any bacteria. “All resistance genes in the environment can be regarded as a big ‘pool’ of resistance genes that can potentially transfer to pathogenic bacteria,” Zorzet said in a news briefing at the 2015 American Association for the Advancement of Science (AAS) meeting in San Jose, California.

Antibiotic resistance now endangers millions in the developing world, as multidrug resistant forms of typhoid, pneumonia, tuberculosis, malaria and other pathogens spread over growing territories. International travel allows resistant pathogens to easily spread to Europe and North America, too, as seen with extremely difficult to treat bacteria such as New Delhi metallo-beta-lactamase-producing Klebsiella from India that now occurs worldwide.

In the U.S., the Centers for Disease Control and Prevention (CDC) currently lists 18 drug-resistant pathogens as urgent, serious or concerning threats. The CDC considers Clostridium difficile, carbapenem-resistant Enterobacteriaceae (CRE) and Neisseria gonorrhoeae to pose an urgent hazard as “high-consequence antibiotic-resistant threats.”2

These pathogens pose a great risk to patients and hospital costs. C.difficile infects more than 250,000 patients in U.S. hospitals each year, killing 14,000 and accounting for $1 billion in excess medical costs annually. CRE infect about 9,000 Americans annually, resulting in 600 deaths and they are now resistant to all or nearly all available antibiotics. According to the CDC, nearly half of hospital patients who develop bloodstream infections caused by CRE die from the infection. Neisseria gonorrhoeae cause more than a quarter of all gonococcal infections.

The CDC categorized 15 resistant organisms as serious threats, which it expects to worsen and potentially become urgent without effective monitoring and prevention activities. These serious threats include multidrug-resistant Acinetobacter, drug-resistant Campylobacter, fluconazole-resistant Candida, extended spectrum Enterobacteriaceae and vancomycin-resistant Enterococcus. Also on the urgent list are multidrug resistant Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus as well as the drug-resistant strains of non-typhoidal Salmonella, Salmonella serotype typhi, Shigella and Streptococcus pneumoniae.

Drug-resistant tuberculosis also made the “serious” list. While most cases of tuberculosis can be treated with first-line drugs in this country, it is one of the leading causes of death worldwide. Drug-resistant strains pose challenges for treatment in the U.S. and extensively drug-resistant forms of TB are spreading abroad.

The CDC considers three other bacteria lower level “concerning threats” because they have developed resistance to specific antibiotics, but multiple other therapeutic options remain available. Vancomycin-resistant Staphylococcus aureus, erythromycin-resistant Streptococcus Group A and clindamycin-resistant Streptococcus Group B fall into this class.

Has your hospital seen an increase in infections caused by drug-resistant pathogens?

  1. AAAS 2015: Keeping up with antibiotic resistance. Emerging Diseases. February 17, 2015.

  2. Biggest Threats. Antibiotic/Antimicrobial Resistance. Updated September 16, 2013.


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