WASHINGTON – With each day of hospitalization, the risk rises by 1% for contracting an infection with a gram-negative, multidrug-resistant organism, based on results from a single-hospital retrospective study.
While conventional wisdom holds that infection risk increases with duration of hospitalization, the study is the first to quantify the potential risk of contracting a multidrug-resistant infection based on length of stay. And while the results may not be applicable to all patients at all hospitals, the findings do give clinicians a sense of the risk posed by a prolonged stay, according to John A. Bosso, Pharm.D., a professor in the College of Pharmacy at the Medical University of South Carolina, Charleston.
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Each day in the hospital could raise infection risk by 1%, doctors cautioned.
Dr. Bosso and his colleagues focused on gram-negative organisms because a colleague had compiled data for 949 episodes of documented gram-negative infections that occurred between 1998 and 2011 at the university hospital. A statement issued at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy noted that the Centers for Disease Control and Prevention has estimated that on any given day, 1 in 25 hospitalized patients has at least one health care–associated infection, and about a third of these are caused by gram-negative bacteria.
The study defined drug-resistant organisms as those that did not respond to treatment with one or more agents in three or more antibiotic classes. The five classes of antibiotics used in the cases studied included aminoglycosides, penicillins, cephalosporins, fluoroquinolones, and folic acid inhibitors. The largest percentage of isolates (38%) was taken from patients with blood stream infections; 29% had pneumonia, 23% had surgical site infections, 6% had urinary tract infections, and 4% had other infections.
Of the 949 organisms reviewed, 251 (26%) were determined to be multidrug resistant.
Ultimately, the type of infection was found to be unrelated to whether a patient had a multidrug-resistant infection. Certain pathogens were more likely to be multidrug resistant. About 56% of Enterobacter isolates, for example, were multidrug resistant as compared with 20% of all other organisms. Alternatively, Pseudomonas isolates were 44% less likely than other isolates to be multidrug resistant.
Length of stay seemed to have the greatest impact on contracting multidrug-resistant strains of gram-negative organisms, with risk maximizing at 10 days of hospitalization. Each day of hospitalization increased the likelihood of multidrug resistance by 1%, Dr. Bosso said.
The researchers were unable to determine the proportion of patients who were already colonized with a multidrug-resistant strain at admission from those who acquired their infections while hospitalized, said Dr. Bosso.
Dr. Bosso reported no financial conflicts of interest.
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