Search

Background: Clinical characteristics and control of the infection of patients with culture-negative (CN) prosthetic joint infection (PJI) have not been well assessed. Prior use of antimicrobial therapy has been speculated but not proven as a risk factor for CNPJI., Questions/purposes: We therefore determined whether prior use of antimicrobial therapy, prior PJI, and postoperative wound healing complications were associated with CN PJI., Methods: We performed a retrospective case-control study of 135 patients with CN PJI treated between January 1, 1985, and December 31, 2000 matched with 135 patients with culture-positive (CP) PJIs (control patients) during the study period. The time to failure of therapy compared between cases and control patients using a Kaplan-Meier analysis., Results: The use of prior antimicrobial therapy and postoperative wound drainage after index arthroplasty were associated with increased odds of PJI being culture-negative (odds ratio, 4.7; 95% CI, 2.8-8.1 and odds ratio, 3.5; 95% CI, 1.5-8.1, respectively). The percent (+/- SE) cumulative incidence free of treatment failure at 2 years followup was similar for CN and CP PJI: 75% (+/- 4%) and 79% (+/- 4%), respectively., Conclusions: Prior antimicrobial therapy and postoperative wound drainage were associated with an increased risk of negative cultures among patients with PJI. Physicians should critically evaluate the need for antimicrobial therapy before establishing a microbiologic diagnosis of PJI in patients with suspected PJI., Level of Evidence: Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The aim of this study was to evaluate the efficacy and safety of rifampin for Staphylococcus aureus (SA) or coagulase negative staphylococci (CNS) prosthetic joint infection (PJI) treated with debridement and retention (D/R). We calculated the treatment failure cumulative incidence (TF) of a cohort of 101 patients with SA or CNS PJI treated with D/R and antimicrobial therapy. The effect of the use of a rifampin-based regimen was evaluated. Cox proportional hazards regression evaluated the association between treatment and time-to-TF controlling for the propensity to treat with rifampin and temporal confounders. Seven percent (1/14) of the prospective rifampin-treated patients, 32% (10/31) of the historical rifampin-treated patients and 38% (21/56) of the historical non-rifampin treated patients developed TF. After controlling for the propensity to treat with rifampin and American Society of Anesthesia scores, patients in the prospective cohort had a lower risk of TF compared to patients in the historical cohort not treated with rifampin (HR 0.11; 95%CI 0.01-0.84). None (0/14) of the patients in the prospective study developed hepatotoxicity. The outcome of staphylococcal PJI treated with D/R and rifampin-based regimens was better when compared with a historical cohort treated without rifampin.

Study Design: This is a prospective study comparing the diagnosis of spinal implant infection by conventional peri-implant tissue culture with a technique which uses a combination of vortexing and bath sonication to dislodge bacteria growing as a biofilm on the surface of retrieved spinal implants., Objective: We hypothesized that the biofilm-sampling technique would be more sensitive than peri-implant tissue culture., Summary of Background Data: Culture of peri-implant tissue is inaccurate for the diagnosis of orthopedic device-related infection; cultures taken from the implant may be more sensitive. We have developed a technique which uses vortexing-bath sonication to sample bacterial biofilms on the surface of retrieved hip and knee implants, and shown that it is more sensitive than peri-prosthetic tissue culture for the microbiologic diagnosis of prosthetic knee, hip, and shoulder infection., Methods: We compared peri-implant tissue culture to the vortexing-bath sonication technique which samples bacterial biofilm on the surface of retrieved spinal implants, for the diagnosis of spinal implant infection. In addition, we compared detection of Staphylococcus and Propionibacterium acnes by rapid cycle real-time polymerase chain reaction with culture of sonicate fluid., Results: A total of 112 subjects were studied; 22 had spinal implant infection. The sensitivities of peri-implant tissue and sonicate fluid culture were 73% and 91% (P = 0.046), and the specificities were 93% and 97%, respectively. P. acnes and coagulase-negative staphylococci were the most frequent microorganisms detected among subjects with spinal implant infection, with P. acnes detected in 56 and 45%, and coagulase-negative staphylococci detected in 31 and 40% of peri-implant tissue and sonicate fluid cultures, respectively. Compared with the culture of sonicate fluid, polymerase chain reaction was 100 and 67% sensitive for the detection of culture-positive Staphylococcus and P. acnes spinal implant infection, respectively., Conclusion: Implant sonication followed by culture is more sensitive than peri-implant tissue culture for the microbiologic diagnosis of spinal implant infection.

Staphylococcus lugdunensis is a coagulase-negative staphylococcus that has several similarities to Staphylococcus aureus. S. lugdunensis is increasingly being recognized as a cause of prosthetic joint infection (PJI). The goal of the present retrospective cohort study was to determine the laboratory and clinical characteristics of S. lugdunensis PJIs seen at the Mayo Clinic in Rochester, MN, between 1 January 1998 and 31 December 2007. Kaplan-Meier survival methods and Wilcoxon sum-rank analysis were used to determine the cumulative incidence of treatment success and assess subset comparisons. There were 28 episodes of S. lugdunensis PJIs in 22 patients; half of those patients were females. Twenty-five episodes (89%) involved the prosthetic knee, while 3 (11%) involved the hip. Nine patients (32%) had an underlying urogenital abnormality. Among the 28 isolates in this study tested by agar dilution, 24 of 28 (86%) were oxacillin susceptible. Twenty of the 21 tested isolates (95%) lacked mecA, and 6 (27%) of the 22 isolates tested produced beta-lactamase. The median durations of parenteral beta-lactam therapy and vancomycin therapy were 38 days (range, 23 to 42 days) and 39 days (range, 12 to 60 days), respectively. The cumulative incidences of freedom from treatment failure (standard deviations) at 2 years were 92% (+/-7%) and 76% (+/-12%) for episodes treated with a parenteral beta-lactam and vancomycin, respectively (P=0.015). S. lugdunensis is increasingly being recognized as a cause of PJIs. The majority of the isolates lacked mecA. Episodes treated with a parenteral beta-lactam antibiotic appear to have a more favorable outcome than those treated with parenteral vancomycin.

Background: C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) have been shown to be useful for diagnosis of prosthetic hip and knee infection. Little information is available on CRP and ESR in patients undergoing revision or resection of shoulder arthroplasties or spine implants., Methods/results: We analyzed preoperative CRP and ESR in 636 subjects who underwent knee (n=297), hip (n=221) or shoulder (n=64) arthroplasty, or spine implant (n=54) removal. A standardized definition of orthopedic implant-associated infection was applied. Receiver operating curve analysis was used to determine ideal cutoff values for differentiating infected from non-infected cases. ESR was significantly different in subjects with aseptic failure infection of knee (median 11 and 53.5 mm/h, respectively, p=<0.0001) and hip (median 11 and 30 mm/h, respectively, p=<0.0001) arthroplasties and spine implants (median 10 and 48.5 mm/h, respectively, p=0.0033), but not shoulder arthroplasties (median 10 and 9 mm/h, respectively, p=0.9883). Optimized ESR cutoffs for knee, hip and shoulder arthroplasties and spine implants were 19, 13, 26, and 45 mm/h, respectively. Using these cutoffs, sensitivity and specificity to detect infection were 89 and 74% for knee, 82 and 60% for hip, and 32 and 93% for shoulder arthroplasties, and 57 and 90% for spine implants. CRP was significantly different in subjects with aseptic failure and infection of knee (median 4 and 51 mg/l, respectively, p<0.0001), hip (median 3 and 18 mg/l, respectively, p<0.0001), and shoulder (median 3 and 10 mg/l, respectively, p=0.01) arthroplasties, and spine implants (median 3 and 20 mg/l, respectively, p=0.0011). Optimized CRP cutoffs for knee, hip, and shoulder arthroplasties, and spine implants were 14.5, 10.3, 7, and 4.6 mg/l, respectively. Using these cutoffs, sensitivity and specificity to detect infection were 79 and 88% for knee, 74 and 79% for hip, and 63 and 73% for shoulder arthroplasties, and 79 and 68% for spine implants., Conclusion: CRP and ESR have poor sensitivity for the diagnosis of shoulder implant infection. A CRP of 4.6 mg/l had a sensitivity of 79 and a specificity of 68% to detect infection of spine implants.

Background: The actual risk of prosthetic joint infection as a result of dental procedures and the role of antibiotic prophylaxis have not been defined., Methods: To examine the association between dental procedures with or without antibiotic prophylaxis and prosthetic hip or knee infection, a prospective, single-center, case-control study for the period 2001-2006 was performed at a 1200-bed tertiary care hospital in Rochester, Minnesota. Case patients were patients hospitalized with total hip or knee infection. Control subjects were patients who underwent a total hip or knee arthroplasty but without a prosthetic joint infection who were hospitalized during the same period on the same orthopedic floor. Data regarding demographic features and potential risk factors were collected. Logistic regression was used to assess the association of variables with the odds of infection., Results: A total of 339 case patients and 339 control subjects were enrolled in the study. There was no increased risk of prosthetic hip or knee infection for patients undergoing a high-risk or low-risk dental procedure who were not administered antibiotic prophylaxis (adjusted odds ratio [OR], 0.8; 95% confidence interval [CI], 0.4-1.6), compared with the risk for patients not undergoing a dental procedure (adjusted OR, 0.6; 95% CI, 0.4-1.1) respectively. Antibiotic prophylaxis in high-risk or low-risk dental procedures did not decrease the risk of subsequent total hip or knee infection (adjusted OR, 0.9 [95% CI, 0.5-1.6] and 1.2 [95% CI, 0.7-2.2], respectively)., Conclusions: Dental procedures were not risk factors for subsequent total hip or knee infection. The use of antibiotic prophylaxis prior to dental procedures did not decrease the risk of subsequent total hip or knee infection.

We recently described a sonication technique for the diagnosis of prosthetic knee and hip infections. We compared periprosthetic tissue culture to implant sonication followed by sonicate fluid culture for the diagnosis of prosthetic shoulder infection. One hundred thirty-six patients undergoing arthroplasty revision or resection were studied; 33 had definite prosthetic shoulder infections and 2 had probable prosthetic shoulder infections. Sonicate fluid culture was more sensitive than periprosthetic tissue culture for the detection of definite prosthetic shoulder infection (66.7 and 54.5%, respectively; P = 0.046). The specificities were similar (98.0% and 95.1%, respectively; P = 0.26). Propionibacterium acnes was the commonest species detected among culture-positive definite prosthetic shoulder infection cases by periprosthetic tissue culture (38.9%) and sonicate fluid culture (40.9%). All subjects from whom P. acnes was isolated from sonicate fluid were male. We conclude that sonicate fluid culture is useful for the diagnosis of prosthetic shoulder infection.

Background: The optimal medical or surgical therapy and outcome of enterococcal prosthetic joint infection are unknown., Method: We performed a retrospective cohort study involving all patients with enterococcal total hip or knee arthroplasty infection treated at our institution from 1969 through 1999. The outcome for patients treated with combination systemic antimicrobial therapy (a cell wall-active agent and an aminoglycoside) versus monotherapy with a cell wall-active agent was analyzed., Results: Fifty episodes of prosthetic joint infection due to enterococci occurred in 47 patients. The median duration of follow-up was 1253 days (range, 29-4610 days). The median age at the time of diagnosis was 70 years (range, 32-89 years). Fifty percent of episodes (25 of 50 episodes) occurred in male patients; 48% (24 of 50 episodes) involved total hip or knee arthroplasty. The estimate of 2-year survival free of treatment failure was 94% (95% confidence interval [CI], 83%-100%) for patients treated with 2-stage exchange, 76% (95% CI, 58%-100%) for patients treated with resection arthroplasty, and 80% (95% CI, 51.6%-100%) for patients treated with debridement and retention of the components (P=.9). The overall rate of 2-year survival free of treatment failure was 88% (95% CI, 77%-100%) for patients treated with monotherapy and 72% (95% CI, 54%-96%) for patients treated with combination therapy (P=.1). The development of cranial nerve VIII toxicity was significantly more common among patients receiving combination therapy (P=.002). Nephrotoxicity was more frequent in the combination therapy group (occurring in 26% of episodes; P=.09)., Conclusions: Enterococcal prosthetic joint infection is uncommon at our institution. Patients receiving combination therapy and those receiving monotherapy did not differ with respect to outcome. There were more cases of ototoxicity in the combination therapy group than there were in the monotherapy group.

Purpose: This study was designed to determine the microbiology and risk of infection following open, agricultural, upper extremity injuries. Specifically, we sought to evaluate the microbiology of the wounds at the time of initial treatment and the development of any subsequent infections, determine whether the development of subsequent infection was related to injury severity, and clarify whether the microorganisms isolated at the time of initial treatment and development of subsequent infection were susceptible to the initial antibiotic prophylaxis., Methods: A retrospective chart review of 214 patients was conducted., Results: The initial injuries were classified into 1 of 3 groups, with 1 being the least severe and 3 being the most severe. Twenty-six were type 1 injuries, 94 type 2, and 94 type 3 injuries. Forty patients developed infection following the injury. Seventeen had superficial wound infection, 16 had deep soft tissue infections, and 7 developed osteomyelitis. Six went on to an amputation due to infection. Fifteen of the infections were polymicrobial. The number of patients who developed infection in the first 6 months following injury was 2, 14, and 24 for type 1, 2, and 3 injuries respectively (p=.07)., Conclusions: Empiric antimicrobial regimens for the management of infection requiring surgical debridement following open upper extremity agricultural injury should be active against staphylococci, aerobic gram-negative bacilli, and anaerobes, but not necessarily against fungi. These antibiotics ideally should be administered on initial presentation of the patient to the emergency department. Prospective studies with emphasis on timely acquisition of cultures and sensitivities are needed to determine optimal prophylactic antimicrobial therapy for these injuries and directed antibiotic regimens for the infections that may develop., Type of Study/level of Evidence: Prognostic II.

Background: Culture-negative (CN) prosthetic joint infection (PJI) has not been well studied. We performed a retrospective cohort study to define the demographic characteristics and determine the outcome of patients with CN PJI., Methods: All cases of CN total hip arthroplasty and total knee arthroplasty infections (using a strict case definition) treated at our institution from January 1990 through December 1999 were analyzed. Kaplan-Meier survival methods were used to determine the cumulative probability of success., Results: Of 897 episodes of PJI during the study period, 60 (7%) occurred in patients for whom this was the initial episode of CN PJI. The median age of the cohort was 69 years (range, 36-87 years). Patients had received a prior course of antimicrobial therapy in 32 (53%) of 60 episodes. Of the 60 episodes, 34 (57%), 12 (20%), and 8 (13%) were treated with 2-stage exchange, debridement and retention, and permanent resection arthroplasty, respectively. The median duration of parenteral antimicrobial therapy was 28 days (range, 0-88 days). Forty-nine (82%) of 60 episodes were treated with a cephalosporin. The 5-year estimate of survival free of treatment failure was 94% (95% confidence interval, 85%-100%) for patients treated with 2-stage exchange and 71% (95% confidence interval, 44%-100%) for patients treated with debridement and retention., Conclusions: CN PJI occurs infrequently at our institution. Prior use of antimicrobial therapy is common among patients with CN PJI. CN PJI treated at our institution is associated with a rate of favorable outcome that is comparable to that associated with PJI due to known bacterial pathogens.

Background: Prosthetic joint infection (PJI) due to rapidly growing mycobacteria (RGM) is only occasionally encountered in clinical practice. Therefore, the optimal clinical management for this condition is unknown., Methods: The medical records of patients who had PJI due to RGM during 1969-2006 were reviewed to summarize its clinical characteristics, treatment, and outcome., Results: Eight patients developed 9 episodes of PJI (7 episodes involving the knee and 1 each involving the hip or elbow) due to RGM at a median of 312 weeks (range, 1-170 weeks) after prosthesis implantation. Patients presented with joint pain (7 patients), joint swelling (7 patients), and fever (3 patients), accompanied by an elevated erythrocyte sedimentation rate (median, 70.5 mm/h) and C-reactive protein level (median, 6 mg/dL). Mycobacterium chelonae (n=3), Mycobacterium abscessus (n=2), Mycobacterium fortuitum (n=3), and Mycobacterium smegmatis (n=1) were isolated from the 9 infected joints. Seven of 9 prostheses were resected, whereas 2 were retained after surgical debridement. Six of 8 patients received > or = 1 active antimicrobial agent for at least 6 months. During a median follow-up period of 33 weeks (range, 2.6-326 weeks) after surgical intervention, no clinical or microbiological relapses were observed. Reimplantation was performed successfully for 2 of 6 patients who underwent resection arthroplasty. The 2 patients with retained prosthesis continued to receive prolonged courses of suppressive antimicrobial therapy., Conclusions: RGM is a rare cause of PJI that should be suspected in patients with negative results of routine bacterial cultures. The combination of resection arthroplasty and antimicrobial therapy is the preferred approach. However, in cases involving retained prosthetic components, RGM infection may be suppressed with lifelong courses of effective antibiotic therapy.

The pathogenic potential of Propionibacterium acnes in implant-associated spine infections is increasingly recognized. However, the clinical findings and outcomes associated with this pathogen in nonimplant-associated spine infections are unknown. We retrospectively reviewed nine male patients who met our strict case definition for P. acnes vertebral osteomyelitis to determine whether the laboratory, radiographic, and histopathology found in these infections differs from that typically associated with vertebral osteomyelitis. We also determined clinical outcomes as they related to medical and surgical treatments rendered. Radiographic results, laboratory results, and histopathology results of patients with P. acnes vertebral osteomyelitis were often not those classically described for this disease. Two of the nine patients' imaging examinations did not suggest infection. Five of six patients had normal erythrocyte sedimentation rates at diagnosis. Three of six patients' histopathology did not show evidence of infection. Two patients whose treatment included spinal surgery with implant placement developed relapse of their infection. The remaining seven patients had rapid improvement with antimicrobial therapy. Patients with P. acnes vertebral osteomyelitis may present with atypical findings. Clinicians should be aware of the pathogenic potential of this organism, particularly following invasive spine procedures.

Background: Spinal implant infections provide unique diagnostic and therapeutic challenges., Methods: We conducted a retrospective cohort study to evaluate risk factors for treatment failure in patients with early- and late-onset spinal implant infections at the Mayo Clinic (Rochester, MN) during 1994-2002., Results: We identified 30 patients with early-onset spinal implant infection and 51 patients with late-onset spinal implant infection. Twenty-eight of 30 patients with early-onset infection were treated with debridement, implant retention, and antimicrobial therapy. The estimated 2-year cumulative probability of survival free of treatment failure for patients with early-onset infection was 71% (95% confidence interval [CI], 51%-85%). Thirty-two of 51 patients with late-onset infection were treated with implant removal. Their estimated 2-year cumulative probability of survival free of treatment failure was 84% (95% CI, 66%-93%). For patients with early-onset infections, receiving oral antimicrobial suppression therapy was associated with increased cumulative probability of survival (hazard ratio, 0.2; 95% CI, 0.1-0.7). For patients with late-onset infections, implant removal was associated with increased cumulative probability of survival (hazard ratio, 0.3; 95% CI, 0.1-0.7)., Conclusions: Early-onset spinal implant infections are successfully treated with debridement, implant retention, and parenteral followed by oral suppressive antimicrobial therapy. Implant removal is associated with successful outcomes in late-onset infections.

Background and Purpose: Follow-up MR imaging examinations are increasingly used to monitor response to treatment in patients with spine infection. We aim to describe follow-up MR imaging examination findings 4-8 weeks after diagnosis and initiation of treatment of spine infections and to compare with clinical findings., Materials and Methods: Thirty-three patients with spinal infection and available baseline and 4-8-week follow-up MRIs were included in this retrospective cohort study. Baseline and follow-up MR imaging were graded by 2 neuroradiologists blinded to clinical characteristics and outcome. Clinical findings and outcomes were independently obtained by retrospective review of the medical record., Results: Compared with baseline MR imaging examinations, follow-up MR imaging more frequently demonstrated vertebral body loss of height (26/33 [79%] versus 14/33 [47%]; P < .001) and less frequently demonstrated epidural enhancement (19/32 [59%] versus 29/33 [88%]; P = .008), epidural canal abscess (3/32 [9%] versus 15/33 [45%]; P = .001), and epidural canal compromise (10/32 [31%] versus 19/33 [58%]; P = .008). Most follow-up MR imaging examinations demonstrated less paraspinal inflammation and less epidural enhancement compared with baseline. However, vertebral body enhancement, disk space enhancement, and bone marrow edema more often were equivocal or appeared worse compared with baseline. Twenty-one of 32 (66%) follow-up MR imaging examination overall grades were considered improved, 5 (16%) were equivocal, and 6 (19%) were worse. No single MR imaging finding was associated with clinical status., Conclusion: Soft tissue findings, not bony findings, should be the focus of clinicians interpreting follow-up MR imaging results. No single MR imaging parameter was associated with the patients' clinical status.

We retrospectively determined the rate of therapeutic intraarticular steroid injection within 1 year before total hip arthroplasty (THA) for osteoarthritis and whether the injection of the steroid increased the risk of infection. In a retrospective matched cohort study, 224 primary THAs (217 patients) implanted within 1 year of intraarticular steroid injection (Group 1) were compared with 224 primary THAs (220 patients) in patients who had not received an injection (Group 2). The mean time between injection and THA was 112 days (SD, 81 days). In Group 1, there were three deep and 11 superficial infections compared with one deep and eight superficial infections in Group 2. The hazard ratios of deep and superficial infections were 3 (95% CI, 0.3, 29.8) and 1.5 (95% CI, 0.6, 3.6), respectively. Intraarticular steroid injection within 1 year of THA did not affect postoperative rates of infection. However, the mean time from steroid injection to THA was 44 days (SD, 23 days) in the few patients who had deep infection develop. While not statistically significant, this raises a concern of increased risk of deep infection when receiving a steroid injection within 6 weeks of THA. Caution should be used before giving an intraarticular steroid injection within 2 months before THA.

A systematic review of the presentation and management of prosthetic joint infection (PJI) due to zoonotic microorganisms, fungi, mycobacteria and other unusual microorganisms is not available. We therefore sought to provide a resource for the practicing orthopaedic surgeon which will serve as a guide for making appropriate decisions in managing such rare, but potentially problematic conditions. We conducted a Medline search of all case reports of PJI due to these unusual microorganisms. Our review of the current literature showed the diagnosis of PJI due to zoonotic microorganisms, fungi, mycobacteria and other unusual microorganisms typically necessitates specialized diagnostic tests. Maintaining a high index of suspicion in diagnosis of such unusual microorganisms and requesting the appropriate laboratory tests at the time of surgical débridement is crucial for determining the microbiologic etiology of these infections. The appropriate medical and surgical management of such infections is complex and often requires the use of special antimicrobials with which the orthopaedist may not be familiar. Collaboration with an infectious disease specialist is advisable when treating these infections.

The association of certain microorganisms, such as Staphylococcus epidermidis, Staphylococcus aureus, and beta-hemolytic streptococci, with prosthetic joint infection (PJI) has been recognized for many years. To our knowledge, a systematic review of the presentation and management of less commonly encountered species of coagulase-negative staphylococci, nutritional-variant streptococci, aerobic non-spore and spore forming Gram-positive or anaerobic bacteria is not available. We therefore sought to provide a comprehensive literature review of PJI due to these microorganisms that will provide a valuable and quick reference for clinicians caring for these patients. We conducted a Medline search of all case reports and case series of PJI due to unusual aerobic and anaerobic bacteria. The presentation, surgical, and medical management strategies were reviewed. Appropriate medical and surgical management of such infections is complex and evolving as newer diagnostic tests, surgical techniques and antimicrobials become available. Management of patients with these infections requires close collaboration between the orthopaedic surgeon, infectious disease specialist and microbiology laboratory.

Background: The ability of follow-up imaging examinations to predict treatment failure in patients with spine infections has not been well studied., Methods: We conducted a retrospective cohort analysis of patients with spine infection who had both baseline and 4-8-week follow-up imaging results available at the Mayo Clinic (Rochester, MN) during the period of 1994-2002. Follow-up imaging findings were categorized as improved, equivocal, or worse, compared with the baseline findings, on the basis of a simple grading system that focused on associated soft-tissue findings., Results: Baseline and 4-8-week follow-up imaging findings were available for 79 patients with spine infection who presented to the Mayo Clinic during 1994-2002. Thirty-five infections (44%) were due to Staphylococcus aureus, 9 (11%) were due to coagulase-negative staphylococci, and 16 (20%) were culture negative. Twenty-seven (34%), 38 (48%), and 14 (18%) follow-up images were graded improved, equivocal, or worse, respectively. The cumulative rates of 1-year survival free of microbiologically confirmed treatment failure were 100%, 89% (95% CI, 74%-96%), and 56% (95% CI, 24%-83%) for patients with improved, equivocal, and worse follow-up imaging findings, respectively (P=.004). Only 3 (6%) of 52 patients deemed to have had clinical improvement at the time of the follow-up imaging study experienced treatment failure. Elevated levels of inflammatory biomarkers identified 2 of these patients as high risk for treatment failure, and the levels were not performed for the third patient., Conclusions: Applying a simple grading scale to assess follow-up imaging examinations for patients with spinal infection stratifies their risk of treatment failure. Patients' clinical statuses and inflammatory biomarker responses may be helpful for selecting patients at high risk for treatment failure who should undergo follow-up magnetic resonance imaging.

Polymethylmethacrylate loaded with antimicrobial agents (most commonly vancomycin and/or aminoglycosides) is used for treatment and prevention of orthopaedic infections. Emergence of organisms resistant to vancomycin or aminoglycosides or both has been reported. Therefore, we studied in vitro release from polymethylmethacrylate beads of antimicrobials with suitable spectra for orthopaedic infections, including cefazolin, ciprofloxacin, gatifloxacin, levofloxacin, linezolid, and rifampin (2.5%, 7.5%, and 15%). Beads were placed in a continuous flow chamber, and antimicrobial concentrations in chamber outflow were determined by bioassay at timed intervals thereafter. Release profiles were bimodal with initial rapid release of high concentrations followed by sustained, slow release. Antimicrobial agents studied showed varied release profiles, indicating that elution from polymethylmethacrylate is unique to individual antimicrobial agents. Increasing antimicrobial concentration in polymethylmethacrylate increased peak concentrations and area under the curve. Cefazolin, ciprofloxacin, gatifloxacin, levofloxacin, linezolid, and rifampin may be suitable for incorporation into polymethylmethacrylate for management of orthopaedic infections.

Background: Debridement and retention of the prosthesis represents an attractive surgical modality for treatment of prosthetic joint infection, but risk factors for treatment failure require clarification., Methods: We conducted a retrospective cohort analysis of all patients with a prosthetic joint infection who were treated with debridement and retention of the prosthesis at the Mayo Clinic (Rochester, Minnesota) between 1995 and 1999., Results: Debridement and retention of the prosthesis was the initial treatment modality for 99 episodes of prosthetic joint infection that occurred in 91 patients who presented to the Mayo Clinic during 1995-1999. A total of 32% and 23% of all episodes were due to Staphylococcus aureus and coagulase-negative staphylococci, respectively. The median duration of intravenous antimicrobial therapy was 28 days (range, 1-90 days). Oral antimicrobial suppression was used in 89% of the episodes, for a median duration of 541 days (range, 5-2673 days). Treatment failure occurred in 53 episodes during a median follow-up period of 700 days (range, 1-2779 days). The 2-year survival rate free of treatment failure was 60% (95% confidence interval [CI], 50%-71%). Variables associated with an increased risk of treatment failure in multivariable analysis included the presence of a sinus tract (hazard ratio, 2.84; 95% CI, 1.48-5.44; P = .002) and a duration of symptoms prior to debridement of > or = 8 days (hazard ratio, 1.77; 95% CI, 1.02-3.07; P = .04)., Conclusions: Debridement and retention of the prosthesis is a common surgical modality at our institution to treat prosthetic joint infection. Risk factors independently associated with treatment failure include the presence of a sinus tract and duration of symptoms prior to debridement of > or = 8 days.

Objective: Prior studies have suggested an association of human retrovirus 5 with rheumatoid arthritis. The purpose of this study was to determine if human retrovirus-5 proviral DNA is present in synovial tissue and blood specimens from patients with rheumatoid arthritis or osteoarthritis, or those without joint disease., Methods: Synovial tissue and whole blood from 75 patients with rheumatoid arthritis, 75 patients with osteoarthritis, and 50 patients without a primary arthritis diagnosis were assayed by real-time quantitative polymerase chain reaction (PCR) using primers that amplify a 186-bp fragment of human retrovirus-5 proviral DNA., Results: A total of 200 tissue specimens, 200 mononuclear cells, and 196 of 200 granulocyte specimens tested negative for human retrovirus-5 proviral DNA. No association between human retrovirus 5 and rheumatoid arthritis or osteoarthritis (P = 0.516) was identified. Granulocyte specimens from 4 patients, 2 with rheumatoid arthritis and 2 with osteoarthritis, yielded a low positive human retrovirus-5 proviral DNA signal (83-1,365 copies of human retrovirus-5 proviral DNA/ml blood)., Conclusion: Contrary to prior reports, we did not find an association between human retrovirus 5 and rheumatoid arthritis or osteoarthritis using a real-time PCR assay. Our findings are consistent with the recent finding that human retrovirus 5 is actually rabbit endogenous retrovirus H.

Explanted orthopedic implants from 54 patients with aseptic failure and 24 patients with prosthetic knee or hip infection were sonicated in polyethylene bags. The sensitivities of periprosthetic tissue and sonicate fluid cultures for the diagnosis of prosthetic joint infection were 54% and 75%, whereas the specificities were 98% and 87%, respectively. Sonication in bags improved bacterial recovery from the surface of orthopedic implants; however, it lacked specificity, due to bag leakage.

Background: Prosthetic joint infection in patients with rheumatoid arthritis is a serious complication of total joint arthroplasty. Little information is available on the outcome of medical and surgical treatments of prosthetic joint infection in patients with rheumatoid arthritis., Methods: We conducted a retrospective analysis of all patients with rheumatoid arthritis and a total hip or total knee arthroplasty infection evaluated at Mayo Clinic (Rochester, MN) between 1 January 1969 and 31 December 1995., Results: A total of 200 first episodes of prosthetic joint infection in 160 patients with rheumatoid arthritis were diagnosed during the study period. Thirty-seven percent of prosthetic joint infection episodes were due to Staphylococcus aureus. Of these episodes, 23% and 19% were treated with debridement and retention of components and 2-stage exchange, respectively. The type of surgical procedure was the only analyzed clinical variable that was associated with treatment failure (P < .001). Rates of 5-year survival free of treatment failure for patients with prosthetic joint infection episodes treated with debridement and retention of components, 2-stage exchange, and resection arthroplasty were 32% (95% confidence interval [CI], 21%-49%), 79% (95% CI, 66%-93%), and 61% (95% CI, 49%-74%), respectively., Conclusions: S. aureus is the most common pathogen among patients with rheumatoid arthritis with prosthetic joint infection. Two-stage exchange was used in only 19% of the prosthetic joint infection episodes among patients with rheumatoid arthritis during the study period, but it was associated with the best outcome. The variable most strongly associated with the outcome was the type of surgical procedure.

The problem of prophylaxis in orthopedic implant surgery will become increasingly important and complex as the population ages and requires more arthroplasty procedures, and the prevalence of antimicrobial-resistant bacteria meanwhile also continues to rise. Energy spent preventing prosthetic joint infection is more effective than that expended in treating the infection of a prosthetic joint, once established. Preventive measures encompass a wide array of variables related to host response, wound environment, and microorganisms. Prophylaxis should address these areas in the preoperative, intraoperative, and postoperative periods. Antimicrobial prophylaxis remains the single most effective method of reducing the prevalence of infection after total joint arthroplasty. In the postoperative period, prophylaxis aims to protect the prosthetic joint against hematogenous seeding from oral, urologic, skin, or gastrointestinal sources. Currently, dental and urologic advisory statements provide recommendations for antimicrobial prophylaxis for high-risk patients with total joint arthroplasty undergoing high-risk procedures. Close collaboration between the orthopedic surgeon, urologist, or dentist and the infectious disease specialist is crucial for providing recommendations regarding prophylaxis in special circumstances. In these particular circumstances, individual decisions should be made based on clinical judgment.

The purpose of this study was to assess the outcome of prosthetic joint infection initially diagnosed by multiple positive intraoperative cultures after revision arthroplasty and treated by strategies that include less than 6 weeks of intravenous antimicrobial therapy. Between January 1995 and December 1999, 16 of 509 (3%) episodes of prosthetic joint infection in 16 patients initially were diagnosed by positive intraoperative cultures after revision arthroplasty. Patients were followed up for a median of 1057 days (range, 731-1969 days). The median age of the patients was 65 years, and 65% of patients had revision total hip arthroplasty. Coagulase-negative staphylococci and Propionibacterium spp were the main pathogens identified. Intravenous antimicrobial therapy was used in 81% of patients and chronic oral suppression was used in 56% of patients. Three patients received no antimicrobial therapy. The median duration of intravenous antimicrobial therapy was 28 days (range, 2-42 days). The 5-year survival free of treatment failure for the 16 episodes was 89%. These results suggest a favorable outcome of prosthetic joint infections because of low virulence pathogens initially diagnosed as positive intraoperative cultures after revision arthroplasty with a variety of medical treatment strategies, including strategies that contain less than 6 weeks intravenous antimicrobial therapy.

Gentamicin and tobramycin are two aminoglycosides commonly impregnated into polymethylmethacrylate for treatment and prevention of prosthetic joint infection. Susceptibilities of staphylococci to aminoglycosides are not reported routinely in the United States. The gentamicin and tobramycin minimum inhibitory value of 93 staphylococci from patients with PJI were determined. Forty-one and 66% of the isolates were resistant to gentamicin and tobramycin, respectively. Methicillin-resistant Staphylococcus aureus isolates were more likely to be resistant to gentamicin or tobramycin than were their methicillin susceptible counterparts. The findings suggest that consideration should be given to the further study of agents other than aminoglycosides for incorporation into polymethylmethacrylate for the treatment and prevention of prosthetic joint infection.

The use of the preoperative skin preparation DuraPrep is thought to enhance the adhesion qualities of an incise drape. If there is less drape lift it was hypothesized that there may be a reduction in wound contamination. We did a single-center, randomized trial to determine if a preoperative skin preparation containing DuraPrep solution plus Ioban 2 drapes reduced wound contamination in total joint replacement surgery compared with a povidone iodine scrub and paint plus Ioban 2 drapes. Secondary research questions focused on comparisons of differences in drape lift and cost between the two groups. Of the 176 evaluable patients, the proportion of patients with a contaminated wound was similar in the two groups (DuraPrep 28.0% versus povidone iodine 36.4%). The mean drape lift in the DuraPrep group was less than the povidone iodine group (1.5 cm versus 9.9 cm respectively). The mean cost of prepping was lower for the DuraPrep group compared with the povidone iodine group (dollars 93.36 and dollars 248.91, respectively). A preoperative skin preparation regimen containing DuraPrep solution plus Ioban 2 drapes is equivalent to a povidone iodine scrub and paint and Ioban 2 for the prevention of wound contamination during total joint replacement surgery. Improved drape lift and cost may influence the choice between the two methods.

It is important to diagnose prosthetic joint infection accurately because the medical and surgical treatment of prosthetic joint infection differs from that of other causes of prosthetic joint failure. Recognition of the presence or absence of infection at or before the time of surgery is important in directing the appropriate surgical approach. Recovery and susceptibility testing of the infecting organism are essential to the selection of appropriate anti-infective therapy.

Because daptomycin is active against Gram-positive cocci, it may be useful in the treatment and prevention of bone and joint infections when incorporated into polymethylmethacrylate (PMMA). The release kinetics of daptomycin from PMMA were studied in a continuous flow chamber designed to simulate in vivo conditions. Three-millimeter beads containing 2.5%, 7.5%, and 15.0% daptomycin (weight daptomycin per weight PMMA) were individually placed in a chamber with 1 mL Krebs Ringer buffer flowing at 1 mL/hour. The majority of daptomycin was released in the first 24 hours. The mean peak concentrations were 13.4, 62.3, and 146.7 microg/mL; the mean AUC0-infinity were 30, 272, and 1204 h x microg/mL; and the mean percentages of daptomycin released were 6%, 18%, and 42% for the beads containing 2.5%, 7.5%, and 15.0% daptomycin, respectively. Daptomycin is released from PMMA in a continuous flow chamber at a rate similar to that previously determined by our laboratory for vancomycin.

Purpose: Criteria for the interpretation of synovial fluid are well established for native joint disorders but lacking for the evaluation of prosthetic joint failure. Our aim was to define cutoff values for synovial fluid leukocyte count and neutrophil percentage for differentiating aseptic failure and prosthetic joint infection., Methods: We performed a prospective study of 133 patients in whom synovial fluid specimens were collected before total knee arthroplasty revision between January 1998 and December 2003. Patients with underlying inflammatory joint disease were excluded., Results: Aseptic failure was diagnosed in 99 patients and prosthetic joint infection was diagnosed in 34 patients. The synovial fluid leukocyte count was significantly higher in patients with prosthetic joint infection (median, 18.9 x 10(3)/microL; range, 0.3 to 178 x 10(3)/microL) than in those with aseptic failure (median, 0.3 x 10(3)/microL; range, 0.1 to 16 x 10(3)/microL; P <0.0001); the neutrophil percentage was also significantly higher in patients with prosthetic joint infection (median [range], 92% [55% to 100%] vs. 7% [0% to 79%], P <0.0001). A leukocyte count of >1.7 x 10(3)/microL had a sensitivity of 94% and a specificity of 88% for diagnosing prosthetic joint infection; a differential of >65% neutrophils had a sensitivity of 97% and a specificity of 98%. Staphylococcus aureus was the only pathogen associated with leukocyte counts >100 x 10(3)/microL., Conclusion: A synovial fluid leukocyte differential of >65% neutrophils (or a leukocyte count of >1.7 x 10(3)/microL) is a sensitive and specific test for the diagnosis of prosthetic knee infection in patients without underlying inflammatory joint disease.

The majority of patients with prosthetic joint replacement (arthroplasty) experience dramatic relief of pain and restoration of satisfactory joint function. In the United States, more than.5 million people have a primary arthroplasty each year. Less than 10% of prosthesis recipients have complications develop during their lifetime, commonly as a result of aseptic biomechanical failure, followed by prosthetic joint infection. The pathogenesis of prosthetic joint infection is related to bacteria in biofilms, in which they are protected from antimicrobial killing and host responses rendering these infections difficult to eradicate. Current microbiology laboratory methods for diagnosis of prosthetic joint infection depend on isolation of a pathogen by culture. However, these methods have neither ideal sensitivity nor ideal specificity. Therefore, culture-independent molecular methods have been used to improve the diagnosis of prosthetic joint infection. In the research setting, detection of 16S ribosomal deoxyribonucleic acid by polymerase chain reaction has been used in the molecular diagnosis of prosthetic joint infection. Various antibiofilm strategies directed at disruption of adherent bacteria are the focus of intense research to improve the detection of biofilm organisms and their eradication. In this article, molecular and antibiofilm approaches to prosthetic joint infection are reviewed.

Debridement with retention of the prosthesis was the initial treatment modality for 19 cases of penicillin-susceptible streptococcal prosthetic joint infection that occurred in 18 patients who presented to the Mayo Clinic (Rochester, Minnesota) during 1969-1998. All of the cases of prosthetic joint infection occurred >30 days after implantation of the prosthesis, which was well fixed at the time of debridement. The median duration of symptoms before debridement was 4 days (range, 1-10 days). Treatment failure (defined as relapse of infection with the original microorganism) occurred in 2 cases (10.5%) during a median follow-up period of 3.9 years (range, 0.3-21.7 years). The 1-year cumulative risk of relapse was 11% (95% confidence interval, 0%-26%). Relapse of prosthetic joint infection due to penicillin-susceptible streptococci after debridement and retention of the prosthesis is uncommon. For patients who present with a well-fixed prosthesis and a short duration of symptoms, debridement with retention appears to be an effective treatment modality.

Polymethylmethacrylate is used for local delivery of antimicrobials in the treatment of musculoskeletal infections. A novel continuous flow chamber system was designed to measure in vitro antimicrobial release. Three-millimeter beads containing amikacin, gentamicin, tobramycin, or vancomycin [concentration of 7.5% (weight per weight)] were placed individually in a continuous flow chamber with a total volume of 1 mL Kreb's Ringer buffer flowing at 1 mL/hour. Effluent was sampled hourly for 24 hours and then every 2 hours up to 48 hours; antimicrobial concentrations were measured in triplicate by bioassay. The mean peak concentrations were 40.9, 30.1, 30.0, and 19.1 microg/mL; the mean areas under the concentration time curves (Time 0 to infinity) were 263, 327, 110, and 180 hours x microg/mL of antibiotic; and the mean percentages of initial amount of antimicrobial released were 11.7%, 14.5%, 6.6%, and 10.9% for tobramycin, gentamicin, amikacin, and vancomycin, respectively. The results for each polymethylmethacrylate-antimicrobial agent combination were reproducible. In contrast to other in vitro elution systems, this novel system operates under the premise that there is dynamic flow surrounding polymethylmethacrylate in vivo and permits rapid in vitro comparison of the relative release of antimicrobial agents from polymethylmethacrylate.

A previously reported staging system for prosthetic joint infection was evaluated in 26 consecutive patients with an infected hip arthroplasty. Six patients were treated by a definitive resection arthroplasty whereas the remaining 20 patients received delayed insertion of another hip arthroplasty. Four of the 20 patients (20%) receiving a new prosthesis had reinfection develop. The only variable in common among the patients who had reinfection was the use of a massive femoral structural allograft at reconstruction. Because of the small number of patients in this study, the power of statistical analysis did not allow definitive determination of the effect of the staging system score with respect to recurrent infection. Based on this study, recommendations can be suggested for addition and deletion of certain variables within the existing staging system. Although the concept of a staging system for treatment of an infected hip arthroplasty is promising, the number of patients required to evaluate the use of a staging system will require a multicenter collaborative study.

The medical treatment of many musculoskeletal infections requires prolonged intravenous antimicrobial therapy, much of which is administered outside the hospital under the guidance of an infectious disease specialist. The essential elements of patient selection, antimicrobial administration, and clinical and laboratory monitoring of outpatient intravenous antimicrobial therapy for adult patients with musculoskeletal infection is described in the current study. Orthopaedists who treat patients with musculoskeletal infection should know the essential details of outpatient intravenous antimicrobial therapy to optimize the medical and surgical treatment of patients with these infections.

We report an unusual case of septic arthritis due to Streptococcus sanguis, a member of the viridans group of streptococci that are part of the normal flora of the mouth and upper respiratory tract. Our patient had severe underlying periodontal disease, which likely contributed to his joint sepsis through hematogenous spread. Although viridans streptococci are rare causes of septic arthritis in native joints, they should be considered in the setting of severe periodontal disease.

Fungal prosthetic joint infection (PJI) is rare, with Candida species being the most frequently reported pathogen in the medical literature. The risk of relapse following delayed reimplantation arthroplasty for candidal PJI is unknown. We describe 4 new cases and summarize 6 previously reported cases of candidal PJI treated with delayed reimplantation arthroplasty. Ninety percent of the patients received antifungal therapy. Eight patients received amphotericin B either alone or in combination with other antifungals. One patient received fluconazole alone. The median duration of time from resection arthroplasty to reimplantation for total hip and total knee arthroplasties was 8.6 and 2.3 months, respectively. Eight patients did not have relapse of candidal PJI following delayed reimplantation arthroplasty after a median duration of follow-up of 50.7 months (range, 2--73 months). Candidal PJI can be successfully treated with delayed reimplantation arthroplasty after receipt appropriate antifungal therapy.

Staphylococcus simulans, a coagulase-negative staphylococcus, is a common animal pathogen that is rarely encountered in human infections. We describe a 70-year-old man who developed multifocal vertebral osteomyelitis and late prosthetic joint infection caused by this pathogen. The patient was a farmer who had daily contact with cows and drank unpasteurized milk, although the portal of the pathogen's entry remains speculative. Culture of the vertebral disk biopsy specimen and cultures during resection arthroplasty yielded S. simulans. A review of the literature suggests that S. simulans may be more virulent than other species of coagulase-negative staphylococci. Accurate identification of S. simulans isolates would facilitate studies to further define its pathogenic role in human infections.

Objectives: To assess the efficacy of Lactobacillus GG in preventing antibiotic-associated diarrhea (AAD) in adults and, secondarily, to assess the effect of coadministered Lactobacillus GG on the number of tests performed to determine the cause of diarrhea., Patients and Methods: In this prospective, randomized, double-blind, placebo-controlled trial conducted from July 1998 to October 1999, 302 hospitalized patients receiving antibiotics were randomized to receive Lactobacillus GG, 20 x 10(9) CFU/d, or placebo for 14 days. Subjects recorded the number of stools and their consistency daily for 21 days. The primary outcome was the proportion of patients who developed diarrhea in the first 21 days after enrollment. Weekly telephone follow-up was also performed. Results were analyzed in an intention-to-treat fashion., Results: Diarrhea developed in 39 (29.3%) of 133 patients randomized to receive Lactobacillus GG and in 40 (29.9%) of 134 patients randomized to receive placebo (P=.93). No additional difference in the rate of occurrence of diarrhea was found between treatment and placebo patients in a subgroup analysis of those treated with beta-lactam vs non-beta-lactam antibiotics. Too few patients had stool cultures, additional laboratory tests for diarrhea, or a positive diagnosis of Clostridium difficile infection to assess between-group differences., Conclusion: Lactobacillus GG in a dose of 20 x 10(9) CFU/d did not reduce the rate of occurrence of diarrhea in this sample of 267 adult patients taking antibiotics initially administered in the hospital setting.

Patients with long-standing, severe, erosive rheumatoid arthritis who have extra-articular manifestations and have undergone joint replacement surgery are at increased risk for serious infection and premature mortality. New therapies, including cytokine antagonists, hold great promise for improving the course of rheumatoid arthritis. However, they have powerful anti-inflammatory effects that may mask symptoms of serious infection. We report a case of fatal pneumococcal sepsis occurring in a 37-year-old woman with rheumatoid arthritis treated with the tumor necrosis factor antagonist etanercept and suggest management strategies for early detection and management of this complication.

In a group of 37 infected hip arthroplasties (36 patients) treated consecutively between January 1997 and October 1999, the feasibility of published patient selection criteria for direct exchange arthroplasty was tested. These criteria include the requirement of a healthy patient with good soft tissues, minimal femoral bone loss, and an organism identified preoperatively as an antibiotic sensitive gram-positive organism. After assignment of the selection criteria, only four patients (four hips) (11%) were deemed potential candidates for a direct exchange procedure. Infected arthroplasties excluded from a primary exchange included 14 patients (15 hips) with gram-negative or methicillin-resistant gram-positive organisms obtained from preoperative joint aspirations, 10 patients (10 hips) with moderate or severe femoral bone loss, four patients (four hips) who required a proximal femoral osteotomy for component removal, two patients (two hips) with poor health status, and two patients (two hips) with poor soft tissues. Because of the increasing emergence of antibiotic-resistant bacteria and an increased prevalence of revision arthroplasties with associated bone loss, the feasibility of published selection criteria for direct exchange are limited. A philosophy of delayed reconstruction for the treatment of the infected hip arthroplasty seems most appropriate in the current era of patient treatment.

Objective: To reduce prophylactic vancomycin use in patients with a history of penicillin or cephalosporin allergy undergoing elective orthopedic surgery by using a targeted allergy consultation and penicillin allergy skin testing., Patients and Methods: The participants in this practice improvement study were patients with a history of penicillin or cephalosporin allergy who were scheduled for elective orthopedic surgery and referred by orthopedic surgeons for allergy consultation and penicillin allergy skin testing between September 22, 1998, and April 15, 1999. The primary outcome measure was the percentage of participants who received prophylactic cefazolin during the study period compared with historical controls., Results: Of the 60 study patients, 59 received a penicillin allergy skin test, 58 underwent orthopedic surgery, and 55 received antibiotic prophylaxis. Fifty-five patients had a history of allergy to penicillin, a cephalosporin, or both, and 5 had a history of nonspecific antibiotic allergy. Of the 59 patients, 55 (93%) had negative penicillin allergy skin test results. Fifty-four (90%) of the 60 patients were given clearance by the allergist to receive cefazolin. Of the 55 study patients who received antibiotic prophylaxis, 6 (11%) received vancomycin compared with 38 (30%) of 127 historical controls (P < or = .05). None of the study patients had an immediate reaction to cefazolin or to vancomycin., Conclusion: Prophylactic vancomycin use in patients with a history of penicillin or cephalosporin allergy undergoing elective orthopedic surgery can be reduced by a targeted allergy consultation and penicillin allergy skin testing.

Staphylococcus lugdunensis, a coagulase-negative staphylococcus, is being increasingly recognized as the cause of serious infections. We report 2 cases of total knee arthroplasty infection caused by S lugdunensis. S lugdunensis frequently produces a clumping factor that can result in a positive slide (short) coagulase test result. If the microbiology laboratory does not use the tube coagulase (long) test to confirm the slide coagulase test result, the organism may be misidentified as Staphylococcus aureus. S lugdunensis is more virulent than other coagulase-negative staphylococci and in many clinical situations behaves like S aureus, further increasing the confusion. However, S lugdunensis differs from S aureus in that it is susceptible to most antibiotics. This fact may alert the microbiology laboratory or the clinician that the isolate is likely not S aureus and prompt further testing of a specific isolate. Accurate identification of S lugdunensis isolates facilitates studies to define the epidemiology and pathogenesis of prosthetic joint infection due to S lugdunensis and delineates optimal medical and surgical therapies.

Antimicrobial prophylaxis is used by clinicians for the prevention of numerous infections, including sexually transmitted diseases, human immunodeficiency virus infection, tuberculosis, rheumatic fever, recurrent cellulitis, meningococcal disease, recurrent uncomplicated urinary tract infections in women, spontaneous bacterial peritonitis in patients with cirrhosis, influenza, malaria, infective endocarditis, pertussis, plague, anthrax, early-onset group B streptococcal disease in neonates, and animal bite wounds. Certain opportunistic infections such as Pneumocystis carinii pneumonia in immunocompromised patients also can be effectively prevented with primary antimicrobial prophylaxis. Perioperative antimicrobial prophylaxis is recommended for various surgical procedures to prevent surgical site infection. Optimal antimicrobial agents for prophylaxis are bactericidal, nontoxic, inexpensive, and active against the typical pathogens that cause surgical site infection postoperatively. To maximize its effectiveness, intravenous perioperative prophylaxis should be given within 30 to 60 minutes before the time of surgical incision. Antibiotic prophylaxis should be of short duration to decrease toxicity, antimicrobial resistance, and excess cost.

An intravenous antibiotic, administered just before skin incision, effectively reduces the prevalence of deep wound infection. The optimal antimicrobial agent has not been determined definitively; however, a short duration of prophylaxis is recommended. Institutional compliance strategies are cost-effective and improve the timing of antibiotic administration. Also, published antimicrobial restriction recommendations are warranted because of the concern of emerging antibiotic-resistant bacteria. Specifically, restriction of vancomycin in orthopaedic surgery should be targeted critically. Supplemental antibiotic administration includes additional intra-operative antibiotic dosing, use of antibiotic-irrigant solutions, and admixture of antibiotics into acrylic bone cement or bone graft. There are no established standards or clinical guidelines for these supplemental antibiotic applications. Post-operatively, antimicrobial agents frequently are overused for various clinical scenarios and this pattern of antibiotic usage is potentially detrimental. A prophylaxis strategy for prevention of early and late hematogenous infection requires consideration of host risk factors, wound environment variables, and sources of potential bacteremia. This strategy should include deliberation of the cost-effectiveness, efficacy, and complications associated with routine use of antibiotics. Advisory statements for elective procedures, which potentially may cause bacteremia, are being developed and additional research is required for this area of antimicrobial agent prophylaxis.