By Stan Deresinski, MD, FACP, FIDSA, FESCMID

Clinical Professor of Medicine, Stanford University

Dr. Deresinski reports no financial relationships relevant to this field of study.

SYNOPSIS: The risk of periprosthetic joint infection resulting from bacteremia depends on the organism.

SOURCE: Honkanen M, Jämsen E, Karppelin M, et al. Periprosthetic joint infections as a consequence of bacteremia. Open Forum Infect Dis 2019;6:ofz218.

The occurrence of bacteremia in a patient with existing implanted foreign material, such as a joint prosthesis, rightly raises concern that the device had become infected due to exposure to bacteria in the bloodstream. Honkanen and colleagues retrospectively examined the risk of incident prosthetic joint infection (PJI) in patients with bloodstream infection (BSI) due to a variety of bacteria from 2002-2013 at the Coxa Hospital for Joint Replacement in Tampere, Finland.

At least one episode of bacteremia occurred in 542 of 14,378 (3.8%) patients who had undergone primary knee or hip replacement. Of these, 85 (0.6%) had more than one episode of BSI, with one patient experiencing eight episodes. A total of 643 BSI episodes occurred, with an incidence of 7.4 per 1,000 person-years. The interval from joint replacement to the occurrence of BSI ranged from three to 4,285 days (median, 1,460 days).

PJI occurred with 46/643 (7%) episodes of BSI in 45/542 (8%) patients (one patient had two separate episodes). The interval between the first positive blood culture and identification of PJI ranged from zero to 522 days, with a median interval of two days. In 10 (21%) PJIs, however, no organism was recovered from the joint.

Among the wide variety of organisms causing BSI, Escherichia coli and Staphylococcus aureus were the most frequently isolated, accounting for 37% and 16%, respectively. However, while only 3/241 (1.3%) episodes of E. coli bacteremia and 1/73 (1.4%) due to other aerobic gram-negative bacilli resulted, 21 of 105 (20%) BSI due to S. aureus BSI did so. Streptococcal bacteremias also frequently were associated with PJI: 12/58 (21%) β-hemolytic streptococci and 4/25 (16%) viridans streptococci, although only 2/43 (5%) Streptococcus pneumoniae bacteremias developed PJI. Among the remaining organisms, the rates were 0/28 for coagulase-negative staphylococci and 1/28 (4%) for enterococci.

COMMENTARY

For the most part, previous studies have focused on the risk of PJI development in patients with S. aureus bacteremia. These studies confirmed the finding that the risk was high, and often much higher than the 20% found by Honkanen and colleagues. Thus, in a retrospective study at the Mayo Clinic in Rochester, MN, 35/85 (41.2%) patients were found to have bacteremia due to this organism.1 As in the study reviewed here, the incidence of knee PJI was approximately twice the incidence with hips. An important finding in the Mayo study was that only 3% of infections were asymptomatic.

Of further interest in the study by Honkanen et al was the very low risk of PJI in patients with gram-negative bacteremia (4/314) and the unexpectedly (at least to me) high risks of the 21% and 16% associated with β-hemolytic streptococci and viridans streptococci, respectively.

One can argue that in some of the very early onset cases, the bacteremia may have resulted from an unrecognized PJI rather than the other way around. One can also argue that, for at least some of the PJIs for which no pathogens were isolated from the joint, these results overstate the problem. Even if true, this does not significantly detract from the overall value to the clinician.

REFERENCE

  1. Tande AJ, Palraj BR, Osmon DR, et al. Clinical presentation, risk factors, and outcomes of hematogenous prosthetic joint infection in patients with Staphylococcus aureus bacteremia. Am J Med 2016;129:221.e11-20.