Review Question - QID 216839

Cutibacterium acnes (formerly Proprionibacterium acnes), a commensal skin bacterial species. C. acnes is a gram-positive, anaerobic bacteria that may take up to 3 weeks to grow on culture.

Shoulder prosthetic joint infections (PJI) are serious complications of shoulder arthroplasty and a major cause for revision within the first 2 years. Diagnosis is multifaceted and involves a high index of suspicion given the indolent nature of the most common organism Cutibacterium acnes. Elevated inflammatory markers, radiographic changes around the prosthesis and aspiration results can all assist with diagnosis. Treatment generally involves prolonged IV antibiotics and two-stage revision arthroplasty. The mean duration of culture incubation for C. acnes is between 7-21 days.

Grosso et al. reviewed the sensitivity of frozen section histology in identifying patients with Propionibacterium acnes (now C. acnes) infection during revision TSA and investigated various diagnostic thresholds of acute inflammation that may improve frozen section performance. They report that using current histopathology grading systems, frozen sections were specific but showed low sensitivity with respect to the P. acnes infection. They concluded that a new threshold value of a total of ten or more polymorphonuclear leukocytes (PMNs) in five high-power fields may increase the sensitivity of frozen section, with minimal impact on specificity.

Padegimas et al. reviewed PJI following shoulder arthroplasty. They reported that hospitalization costs for PJI are comparable to those of primary arthroplasty, however, they are incurred after the original cost of shoulder arthroplasty. They concluded that certain identifiable patient variables correlate with higher PJI rates and risk factor modification may decrease PJI incidence and help contain costs.

Florschütz et al. retrospectively reviewed whether a difference in infection rate existed after primary anatomic TSA (aTSA) and primary reverse TSA (rTSA). They reported no difference in infection rate after primary aTSA and primary rTSA in shoulders that have not undergone previous operative interventions. They concluded that infection is more likely to develop in shoulders undergoing primary rTSA that have had one or more nonarthroplasty operative procedures.

Figure A is the AP radiograph of a previously placed anatomic TSA which reveals radiolucent lines concerning for PJI

Incorrect Answers:
Answer 2: Staphylococcus aureus is a facultative aerobic, Gram-positive coccal (round) bacterium
Answer 3: Escherichia coli is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium
Answer 4: Neisseria gonorrhoeae is a Gram-negative, diplococci bacteria
Answer 5: Corynebacterium diphtheriae is a nonmotile, noncapsulated, club-shaped, Gram-positive bacillus