In Vitro Activity of Rifampin, Rifabutin, Rifapentine, and Rifaximin against Planktonic and Biofilm States of Staphylococci Isolated from Periprosthetic Joint Infection.

The in vitro activities of rifampin, rifabutin, rifapentine, and rifaximin were tested against 200 periprosthetic joint infection (PJI)-associated staphylococci. Seven rifampin-resistant isolates had MICs of ≥4 µg/ml. Three isolates had rifampin MICs of 0.25 to 1 µg/ml and harbored an Asp471Gly RpoB variant, suggesting that the CLSI rifampin-susceptible staphylococcal breakpoint of ≤1 µg/ml may be too high. The remaining isolates had rifampin MICs of ≤0.016 µg/ml, and the rifampin, rifabutin, rifapentine, and rifaximin minimum biofilm bactericidal concentrations (MBBC) for ≥50% of isolates were 8, 1, 2, and 4 µg/ml (for S. aureus) and 2, 0.06, 0.25, and 0.5 µg/ml (for S. epidermidis), respectively, for rifampin-susceptible isolates. Nonrifampin rifamycins have promising staphylococcal activity, including antibiofilm activity.

The Impact of Anesthetic Management on Surgical Site Infections in Patients Undergoing Total Knee or Total Hip Arthroplasty.

BACKGROUND: Surgical site infection (SSI) is one of the most challenging and costly complications associated with total joint arthroplasty. Our primary aim in this case-controlled trial was to compare the risk of SSI within a year of surgery for patients undergoing primary total knee arthroplasty (TKA) or total hip arthroplasty (THA) and revision TKA or THA under general anesthesia versus neuraxial anesthesia. Our secondary aim was to determine which patient, anesthetic, and surgical variables influence the risk of SSI. We hypothesized that patients who undergo neuraxial anesthesia may have a lesser risk of SSI compared with those who had a general anesthetic. METHODS: We conducted a retrospective, case-control study of patients undergoing primary or revision TKA and THA between January 1, 1998, and December 31, 2008, who subsequently were diagnosed with an SSI. The cases were matched 1:2 with controls based on type of joint replacement (TKA versus THA), type of procedure (primary, bilateral, revision), sex, date of surgery (within 1 year), ASA physical status (I and II versus III, IV, and V), and operative time (<3 vs >3 hours). RESULTS: During the 11-year period, 202 SSIs were identified. Of the infections identified, 115 (57%) occurred within the first 30 days and 87 (43%) occurred between 31 and 365 days. From both univariate and multivariable analyses, no significant association was found between the use of central neuraxial anesthesia and the postoperative infection (univariate odds ratio [OR] = 0.92; 95% confidence interval [CI], 0.63-1.34; P = 0.651; multivariable OR = 1.10; 95% CI, 0.72-1.69; P = 0.664). The use of peripheral nerve block also was not found to influence the risk of postoperative infection (univariate OR = 1.41; 95% CI, 0.84-2.37; P = 0.193; multivariable OR = 1.35; 95% CI, 0.75-2.44; P = 0.312). The factors that were found to be associated with postoperative infection in multivariable analysis included current smoking (OR = 5.10; 95% CI, 2.30-11.33) and higher body mass index (BMI) (OR = 2.68; 95% CI, 1.42-5.06 for BMI ≥ 35 kg/m compared with those with BMI < 25 kg/m). CONCLUSIONS: Recent studies using large databases have concluded that the use of neuraxial compared with general anesthesia is associated with a decreased incidence of SSI in patients undergoing total joint arthroplasty. In this retrospective, case-controlled study, we found no difference in the incidence of SSI in patients undergoing total joint arthroplasty under general versus neuraxial anesthesia. We also concluded that the use of peripheral nerve blocks does not influence the incidence of SSI. Increasing BMI and current smoking were found to significantly increase the incidence of SSI in patients undergoing lower extremity total joint arthroplasty.

Laboratory and clinical characteristics of Staphylococcus lugdunensis prosthetic joint infections.

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.