Vergidis, Paschalis

Abstract:BackgroundThe clinical features and outcome of prosthetic joint infection (PJI) among solid organ transplant (SOT) recipients have not been characterized. We performed a retrospective, matched case‐control study to examine potential risk factors.MethodsWe reviewed cases ofPJIamong transplant recipients who were evaluated at the Mayo Clinic between 1989 and 2009. Cases were matched to non‐infected controls based on transplant type, prosthetic joint type, and order of organ transplantation/joint implantation.ResultsAmong 367 patients with both a joint prosthesis and anSOT, there were 12 cases of infection in those receiving immunosuppression. These occurred in 8 renal recipients, 3 liver recipients, and 1 heart transplant recipient. Six subjects had hip and 6 had knee arthroplasty infections. The observed time to prosthesis failure ranged from 0.5 to 148 months after implantation. Gram‐positive bacteria (staphylococci and streptococci) caused the infection in 8 subjects. Two cases were caused by nontuberculous mycobacteria, whereas the remaining 2 cases were culture‐negative in the setting of antimicrobial use. We did not find a statistically significant association between obesity, diabetes mellitus, or antimicrobial prophylaxis (given in the setting of immunosuppression) and development ofPJI. A marginal association was seen betweensurgical site infectionand the risk ofPJI; however, this did not reach statistical significance.ConclusionIn our series, infection was mainly caused by gram‐positive bacterial pathogens, similar to the commonly encountered organisms in the immunocompetent host, although opportunistic pathogens were also isolated.

Abstract:Post‐transplantation histoplasmosis may be acquired via inhalation, may result from endogenous reactivation, or may be derived from the allograft. The Histoplasma and Aspergillus enzyme‐linked immunoassays are increasingly being relied upon for rapid diagnosis of fungal infections, especially in immunocompromised patients. We describe 4 cases of solid organ transplant recipients who had histoplasmosis and a falsely positive Aspergillus galactomannan (GM) obtained from the serum or bronchoalveolar lavage (BAL) fluid. We also report our experience, testing for Histoplasma antigen (Ag) in specimens positive for Aspergillus GM. From January 2007 through December 2010, of 2432 unique patients who had positive Aspergillus GM tests, 514 (21%) were tested for Histoplasma Ag, and 27 were found to be positive. Most specimens that tested positive for both Aspergillus and Histoplasma were obtained by BAL. False‐positive tests for Aspergillus GM can occur in immunosuppressed patients who have histoplasmosis, and may obscure the correct diagnosis.

ABSTRACT Rifampin monotherapy was compared to the combination of linezolid or vancomycin with rifampin in an experimental rat model of methicillin-resistant Staphylococcus aureus (MRSA) chronic foreign body osteomyelitis. MRSA was inoculated into the proximal tibia, and a titanium wire was implanted. Four weeks after infection, rats were treated intraperitoneally for 21 days with rifampin alone ( n = 16), linezolid plus rifampin ( n = 14), or vancomycin plus rifampin ( n = 13). Thirteen animals received no treatment. At completion of treatment, qualitative cultures of the wire and quantitative cultures of the bone (reported as median values) were performed. Quantitative cultures from the control, rifampin monotherapy, linezolid-plus-rifampin, and vancomycin-plus-rifampin groups revealed 4.54, 0.71, 0.10, and 0.50 log 10 CFU/gram of bone, respectively. The bacterial load was significantly reduced in all treatment groups compared to that in the control group. Rifampin resistance was detected in isolates from 10, 2, and 1 animal in the rifampin, linezolid-plus-rifampin, and vancomycin-plus-rifampin groups, respectively. Cultures of the removed wire revealed bacterial growth in 1 and 2 animals in the rifampin and linezolid-plus-rifampin groups, respectively, with no growth in the vancomycin-plus-rifampin group and growth from all wires in the untreated group. In conclusion, we demonstrated that combination treatment with linezolid plus rifampin or vancomycin plus rifampin is effective in an animal model of MRSA foreign body osteomyelitis in the context of retention of the infected foreign body.