SEATTLE – Antibiotic-resistant infections are becoming more common in hospitalizations, and the profile of patients with these infections is changing, according to a retrospective study of about 370 million U.S. hospitalizations spanning a recent 10-year period.
During 1997-2006, the percentage of those having a diagnosis of antibiotic-resistant infection nearly quadrupled, researchers reported at the annual meeting of the North American Primary Care Research Group.
Dr. Arch G. Mainous III
The mean age of the patients with resistant infections fell by 22 years, and the proportion with health insurance decreased by 7%. In addition, those who were uninsured had a shorter length of stay than did their insured counterparts.
"There has been a steady upward trend in antibiotic-resistant [infections in] hospitalizations," commented lead investigator Arch G. Mainous III, Ph.D. "Resistant infections now account for almost 2.5% of infection-related hospitalizations, and we have to assume that that [percentage] will only go up."
Better strategies to combat rising resistance are needed, both in the community (for example, a tighter control of physicians' prescribing practices and the elimination of avenues by which people obtain antibiotics without a prescription) and in hospitals (such as the use of better infection control measures), he said.
The findings suggest that insurance status may influence the care of inpatients with resistant infections, according to Dr. Mainous. "Either people without insurance are being discharged prematurely, or people with insurance are [being kept] in the hospital longer than they need to be [so that hospitals can] make money," he said. "Either way, I think it has particular implications for quality of care."
Dr. Franklin Michota, however, did not think that the lack of insurance was leading to premature discharge. "One reason that [length of stay] for antibiotic-resistant infections is getting shorter may be that our ability to provide home therapies – such as IV antibiotics, which we typically end up giving when antibiotic resistance is found – was available in 2006, but not in 1997. In addition, the skilled inpatient facility was not available in 1997 to the extent that it is today, so many patients who simply need IV antibiotics to treat resistant infections may be discharged to receive care elsewhere. It is not as if their care is ending."
The criteria for discharge are the same between resistant and nonresistant infections, noted Dr. Michota, who is the director of academic affairs in the department of hospital medicine at the Cleveland Clinic. "Furthermore, there is nothing in this study to suggest that those patients who presented with resistant infections were more ill than those patients with infections involving antibiotic-susceptible organisms."
The researchers analyzed data from the National Hospital Discharge Survey for the years 1997-2006. Survey participants are a nationally representative sample of short-stay, children's, and general hospitals.
The researchers evaluated hospitalizations, looking for diagnosis codes for infections and drug resistance. National estimates were based on a weighted 370.3 million hospitalizations.
Results showed that the annual number of infection-related hospitalizations with resistance rose by nearly 136,000 (or 327%) between 1997 and 2006, reported Dr. Mainous, a professor in the department of family medicine at the Medical University of South Carolina in Charleston.
Among all hospitalizations, the percentage having a diagnosis of resistant infection increased from 0.12% to 0.46%. And among just infection-related hospitalizations, the percentage having a diagnosis of resistance increased from 0.66% to 2.40%.
The mean age of patients having resistant infections fell sharply, from 65.7 years in 1997 to 44.2 years in 2006. The rise in these infections was greatest among patients younger than 18 years of age.
By far, the most common resistance found was to penicillin, with penicillin-resistant infections accounting for 94% of all resistant infections. Infections having isolated vancomycin resistance came in a distant second, at 3%.
In a finding that Dr. Mainous described as "definitely counterintuitive," the median length of stay for infection-related hospitalizations with resistance decreased by 40%, from 6.6 to 4.0 days. The stay for those without resistance remained essentially unchanged, at 4.8 and 4.3 days.
About 97% of patients with resistant infections had health insurance in 1997, but that figure fell to 90% in 2006. And uninsured patients had shorter stays than did their insured peers.
"What we are seeing is that as people get younger, they are less likely to have insurance and their length of stay goes down," Dr. Mainous commented. "We couldn't come up with a specific mechanism by which insurance would make the infection less virulent."
Over the 10-year period, there were favorable trends in outcomes whereby infection-related hospitalizations that involved resistance were less likely to end in death or discharge to a care institution, and more likely to end in routine discharge.