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Institutions report rise in periprosthetic infection burden from resistant strains
The rates of MRSA and methicillin-resistant Staph epidermis reportedly doubled from 1999 to 2006.
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A recent study found the number of patients with periprosthetic infections at two institutions increased significantly in a 7-year period. Investigators noted most infections were caused by gram-positive organisms.
“The changing organism profile for periprosthetic joint infection at least observed at two institutions is concerning,” Benjamin Bender, MD, said. “There appears to be a rise in the incidence of periprosthetic joint infection caused by resistant organisms. If confirmed in other institutes, this trend could present a real challenge.”
Bender presented results of a study of 351 patients with periprosthetic joint infections during the American Academy of Orthopaedic Surgeons 75th Annual Meeting. All patients were treated at the Rothman Institute in Philadelphia and Washington University in St. Louis between 1999 and 2006.
In that time, the incidence of methicillin-resistant Staphylococcus aureus (MRSA) more than doubled, increasing from 16% to 37%, said Bender, a Rothman Institute fellow. “A similar trend was noticed for methicillin-resistant S. epidermis (MRSE), with the incidence rising from 11% to 25% in 2006.”
Two-stage revisions
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There were nearly equal numbers of men and women, at a mean age of 66 years old, among the 351 patients with periprosthetic infections in the study; 217 cases involved two-stage exchange revision arthroplasty (62%).
The other surgical treatments included 97 irrigation and debridement procedures and 31 one-stage prosthetic exchanges. Five additional cases involving revisions for mechanical issues were added to the study when the patients had serum cultures revealing infections requiring antibiotic treatment.
In analyzing the infections, “as with other studies, we found that gram- positive organisms account for most of the infections; 10% were caused by gram-negative organisms,” Bender explained.
Referred patients
Investigators included a patient once in their analysis if the same organism was grown during revision and re-revision cultures. But if an individual undergoing a second revision surgery had a different organism cultured during any subsequent procedure, he or she was included in the analysis twice.
Bender said S. aureus and S. epidermis were the most prevalent gram positive infections identified. There was one fungal infection case. He noted 1999 was used as the study’s starting point because electronic microbiology data was first introduced that year.
Investigator Javad Parvizi, MD, FRCS, told Orthopedics Today that 58% of the cases included in the study from the Rothman Institute were referrals. “There is actually a rise in the incidence of cases that are being referred to us that are caused by MRSA or MRSE,” he said.
Growing infection problem
“Among infections being referred to us, a disproportionately higher number are caused by MRSA and MRSE,” Parvizi, a member of the Orthopedics Today Editorial Board, said.
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Investigators from both sites tried to determine if the increase seen in periprosthetic infections was a geographical phenomenon or a more widespread trend, according to Parvizi. Since completing this study, he and others have worked with six centers around the world to study these infection rates.
“[The centers] have seen a similar sort of rise in the incidence of resistant organisms, and this is now being reflected in the literature,” he said. “Clearly there is a rise everywhere and that is worrisome.”
When Orthopedics Today spoke with Parvizi he had just finished analyzing his center’s data concerning resistant infections.
“Not only is the cost of treating patients with MRSA and MRSE much higher — about 2.1-fold — than for patients who have an infection caused by a sensitive organism, but the actual success of the procedure is less,” he said, with many patients tending to have longer stays and rehabilitation, more complications and intermediate procedures between implantation of an antibiotic spacer and the final implant.
A note from the editor:
In September, Javad Parvizi, MD, FRCS, will begin a bi-monthly column for Orthopedics Today called Infection Watch.
For more information:
- Benjamin Bender, MD, can be reached at the Rothman Institute, 925 Chestnut St., 5th Floor, Philadelphia, PA 19107. 267-339-3617. Bender has no direct financial interest in any products or companies mentioned in this article.
- Javad Parvizi, MD, FRCS, can also be reached at the Rothman Institute; e-mail: parvj@aol.com. Parvizi receives research support from and is a consultant to Stryker, he receives miscellaneous funding from Johnson & Johnson and is a consultant to Smith & Nephew.
Reference:
- Parvizi J, Ghanem ES, Steinbrecher J, et al. The changing organism profile in periprosthetic infection. Paper #95. Presented at the American Academy of Orthopaedic Surgeons 75th Annual Meeting. March 5-9, 2008. San Francisco.