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Link discovered between multidrug-resistant infections and length of hospital stay

Jenny Scarnecchia | MUSC News Center | November 13, 2014

John BossoPhoto by Helen Adams
John Bosso, Pharm.D., was senior author of a study that showed doctors and patients need to think carefully about how long someone should be in the hospital. 

You are scheduled to undergo a minor inpatient procedure at the hospital. Friends and family immediately sound alarms:

“You might get an infection!”
“People get infections all the time!”
“The longer you stay the more likely you are to get a superbug!”

In reality, the odds of infection are extremely low, patients rarely get them and ... well, yes, actually, the longer you stay, the more risk you do face for a multidrug-resistant infection (MDR).

While conventional wisdom has been that long hospital stays increase infection risks, there has been little quantification of the link between length of stay (LOS) and risk of infection with an MDR.

A recent single-center study at the Medical University of South Carolina (MUSC) found the risk of MDRs did increase with the length of hospital stay. The results were presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy in Washington, D.C., earlier this fall.

This study is the first to quantify a link between hospital LOS and risk of infection, which senior author John Bosso decided to study more broadly after earlier research showed the assumption between LOS and MDR was not always accurate. These new findings suggest a strong argument against unnecessary hospitalization and unnecessarily long hospitalization.

“The study showed exactly how much the risk increases and at which point in the stay, within the parameters of the study,” said Bosso, professor of clinical pharmacy and outcomes sciences at the South Carolina College of Pharmacy, which has a campus at MUSC. “This may need to start being factored in to how often and for how long patients are admitted.”

Bosso and colleagues analyzed 949 episodes of documented Gram-negative infections recorded at the hospital and compared the day of infection with the day of the hospital stay. Gram-negative bacteria cause infections such as pneumonia in health care settings and are resistant to multiple drugs. Their analysis revealed the number of infections that were MDRs rose one percent for every day a patient was in the hospital and was highest for patients with hospital stays of 10 or more days.

“Resistance to antibiotics is a major problem we’re facing right now,” said Tonya Smith, a 2014 S.C. College of Pharmacy graduate now at the University of Utah. “We wanted to see if we could quantify different things that would help us understand the risk factors so we could help patients avoid getting these hard-to-treat organisms.”

Infection control is high on the priority list for all hospitals and a patient’s chance of acquiring any infection while in the hospital remains low. As an example, in 2013 at MUSC’s hospital there were 10 hospital onset events of MRSA bloodstream infection per more than 100,000 patient days for an incidence rate of 0.071.

At the same time, patients can take some control over how much risk they face.

“Patients need to be more actively involved in their care decisions,” Bosso said. “Not going into the hospital when you don’t need to, not staying longer than you need to, making sure your doctor doesn’t give you antibiotics when they’re unnecessary or longer than necessary – all those are risk factors for infections.

The single-center study, which was limited to a tertiary-care academic hospital, defined MDR pathogens as those that were resistant to at least one drug in each of at least three antibiotic classes. Gram-negative infections were the focus of the study because these are generally the most resistant pathogens. As a result, the analysis did not include Staphylococcus aureus — one of the most drug-resistant pathogens — because it is a Gram-positive organism. Bacteria are classified as Gram-negative or Gram-positive as a way of identifying and distinguishing them via the Gram staining method of bacterial differentiation.

According to the Centers for Disease Control and Prevention, “Gram-negative bacteria cause infections including pneumonia, bloodstream infections, wound or surgical site infections and meningitis in healthcare settings. Gram-negative bacteria are resistant to multiple drugs and are increasingly resistant to most available antibiotics.

“These bacteria have built-in abilities to find new ways to be resistant and can pass along genetic materials that allow other bacteria to become drug-resistant as well. CDC’s aggressive recommendations, if implemented, can prevent the spread of gram-negatives.”



Related Stories >>

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CNN: Hospital infections

Resources >>

CDC: About antimicrobial resistance

Presentation about MDR/LOS study

What are multidrug-resistant organisms?

MUSC News Center archives

Jenny Scarnecchia works in admissions and communications for the College of Pharmacy at MUSC.


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