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Paper of the week: Risk factors associated with periprosthetic joint infection after total elbow arthroplasty

Paper of the week: Risk factors associated with periprosthetic joint infection after total elbow arthroplasty. Somerson JS, Boylan MR, Hug KT, Naziri Q, Paulino CB, Huang JI. Shoulder Elbow. 2019 Apr;11(2):116-120. doi: 10.1177/1758573217741318.

Summary by Dr Sreeram Penna

This is a retrospective registry study of patients who had total elbow arthroplasty (TEA). Data was obtained from New York SPARCS database. Study included 1452 patients who had TEA in New York state between 1st Jan 2003 to 30th September 2012. Overall rate of infection was 3.72% (54/1452). There were 30 early infections (2.1%), 17 delayed infections (1.2%) and seven late infections (0.5%). Regression model showed that main risk factors associated with periprosthetic joint infection in TEA was rheumatoid arthritis (OR:3.31; p<0.001), tobacco use disorder (OR:3.39; p=0.003) and hypothyroidism (OR:2.04; p=0.045).

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Paper of the week: Large variations in clinical antibiotic activity against Staphylococcus aureus biofilms of periprosthetic joint infection isolates.

Paper of the week: Large variations in clinical antibiotic activity against Staphylococcus aureus biofilms of periprosthetic joint infection isolates. Mandell JB, Orr S, Koch J, Nourie B, Ma D, Bonar DD, Shah N, Urish KL. J Orthop Res. 2019 Mar 27. doi: 10.1002/jor.24291

Summary by Dr Sreeram Penna

In this study researchers assessed the efficacy of various antibiotics against staphylococcal aureus bacterial isolates in both planktonic and biofilm stages. They have measured minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for isolates in planktonic state and minimum biofilm inhibitory concentration (MBIC) and minimum biofilm bactericidal concentration (MBBC) for bacteria isolates grown in biofilm state. They have tested two lab strains USA300 and SH1000 and 10 Methicillin resistant Staphylococcus aureus (MRSA) clinical isolates and 8 Methicillin sensitive Staphylococcus aureus (MSSA) clinical isolates. They have tested these isolates against various dilutions of vancomycin, rifampin, gentamycin, trimethoprim/sulphamethoxazole, doxycycline and daptomycin. In addition to above MSSA isolates were tested with cefazolin and nafcillin and MRSA isolates were tested with clindamycin and linezolid.

Results showed that across the bacterial isolates MIC concentrations varied largely for gentamicin, trimethoprim/sulfamethoxazole and vancomycin (approximately 1.5 log spread) and smaller variation (0.5 log spread) for rifampin, doxycycline, and daptomycin. Similarly, MBC concentrations varied significantly (2 log spread) for all antibiotics. Rifampin was superior to other antibiotics against planktonic cultures with MBC concentrations ranging from 0.13 to 8 microgram / ml. With biofilm isolates most antibiotics showed significant variability (2 to 3 log spreads) in MBIC except daptomycin. Of all the antibiotics tested only rifampin, doxycycline, and daptomycin had impact on 48-hour mature biofilms, with biofilm MBCs ranging from 80 to 2000 μg/ml. In conclusion this research shows variable impact of antibiotics on different strain isolates and also difference in susceptibilities of isolates in planktonic stages versus biofilm stages.