Validation of new shoulder periprosthetic joint infection criteria.

BACKGROUND: A periprosthetic joint infection (PJI) in the shoulder can be difficult to diagnose. Many variables have been used to determine a PJI. Recently, the 2018 International Consensus Meeting (ICM) on orthopedic infections gave new criteria to help identify PJI in the shoulder. With the new criteria (major and minor), the PJI definition can be categorized into definite, probable, possible, and unlikely. This study was conducted to assess the new criteria for a series of consecutive first stage revision shoulder arthroplasty cases. METHODS: All patients undergoing a first stage revision shoulder arthroplasty using a prosthesis made of antibiotic-loaded acrylic cement (PROSTALAC) spacer from 2016 through 2019 were evaluated retrospectively. All cases were performed by a single surgeon. Each case was reviewed using the 2018 shoulder ICM diagnostic criteria. Secondary factors evaluated were type of organism identified, accuracy of minor criteria, and frozen vs. permanent section accuracy. RESULTS: A total of 87 first-stage revision arthroplasty cases were reviewed. Based on the 2018 ICM criteria, there were 20 definite (30.0%), 19 probable (21.8%), 6 possible (6.9%), and 42 unlikely (48.3%) infections. Cutibacterium acnes was the most common infectious organism overall (77.3% of culture positive cases) and was present in 39.1% of cases overall. Ten patients (25.6%) grew multiple organisms. Thirty-one patients (35.6%) had a loose humeral stem, with 23 of those patients (74.2%) having a definite or probable infection (odds ratio [OR] 7.2, 95% confidence interval [CI] 2.67-19.37, P = .0001). Eleven patients (91.7%) with an elevated intraoperative synovial neutrophil cell count had a definite or probable infection. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) was elevated in patients with a definite or probable infection (OR 9.4, 95% CI 2.47-35.62, P = .0010, and OR 7.7, 95% CI 2.29-25.56, P = .0009), respectively. Discordant results between frozen and permanent sections were found in 4 patients (4.6%). CONCLUSION: The 2018 ICM shoulder infection criteria gave a new scoring system to diagnose PJI. C acnes was the most common infectious organism identified. Patients who had a loose humeral stem, elevated ESR, or elevated CRP were more likely to have either a definite or probable PJI. Frozen sections were able to accurately identify definite infections. Unexpected wound drainage and positive preoperative cultures were low-yield criteria in this series. More research into determining periprosthetic shoulder infection is needed to help identify which patients are more likely to have an infection.

Bacillus anthracis has two independent bottlenecks that are dependent on the portal of entry in an intranasal model of inhalational infection.

Bacillus anthracis can cause inhalational anthrax. Murine inhalational B. anthracis infections have two portals of entry, the nasal mucosa-associated lymphoid tissue (NALT) and the lumen of the lungs. Analysis of the dissemination from these sites is hindered because infections are asynchronous and asymptomatic until the hosts near death. To further understand and compare how B. anthracis disseminates from these two different environments, clonal analysis was employed using a library of equally virulent DNA-tagged clones of a luminescent Sterne strain. Luminescence was used to determine the origin of the infection and monitor the dissemination in vivo. The number of clones and their proportions in the portals of entry, lymph nodes draining the portals, and kidneys were analyzed. Clonal analysis indicated a bottleneck for both portals of entry, yet the extent and location of the reduction in represented clones differed between the routes. In NALT-based infections, all clones were found to germinate in the NALT, but they underwent a bottleneck as the infection spread to the cervical lymph node. However, lung-based infections underwent a bottleneck in a focal region of growth within the lung lumen and did not need to spread through the mediastinal lymph nodes to cause a systemic infection. Further, the average number of clones found in the kidney and the rate at which genetic drift was affecting the disseminated populations were significantly higher in lung-based infections. Collectively, the data suggested that differences in the host environment alter dissemination of B. anthracis depending on the site of initial colonization and growth.