Diagnosis of Propionibacterium acnes bone and joint infection is challenging due to the long cultivation time of up to 14 days. We retrospectively studied whether reducing the cultivation time to 7 days allows accurate diagnosis without losing sensitivity. We identified patients with at least one positive P. acnes sample between 2005 and 2015 and grouped them into "infection" and "no infection." An infection was defined when at least two samples from the same case were positive. Clinical and microbiological data, including time to positivity for different cultivation methods, were recorded. We found 70 cases of proven P. acnes infection with a significant faster median time to positivity of 6 days (range, 2 to 11 days) compared to 9 days in 47 cases with P. acnes identified as a contamination (P < 0.0001). In 15 of 70 (21.4%) patients with an infection, tissue samples were positive after day 7 and in 6 patients (8.6%) after day 10 when a blind subculture of the thioglycolate broth was performed. The highest sensitivity was detected for thioglycolate broth (66.3%) and the best positive predictive values for anaerobic agar plates (96.5%). A prolonged transportation time from the operating theater to the microbiological laboratory did not influence time to positivity of P. acnes growth. By reducing the cultivation time to 7 days, false-negative diagnoses would increase by 21.4%; thus, we recommend that biopsy specimens from bone and joint infections be cultivated to detect P. acnes for 10 days with a blind subculture at the end. P ropionibacterium acnes is a facultative anaerobic Gram-positive rod, abundant on the human skin, and mainly associated with the sebaceous glands of the shoulder and axilla (1). It is most commonly associated with the chronic skin disease acne vulgaris. However, it may also cause bone and joint infections, including implant-associated infections. P. acnes has been recognized as an emerging cause of shoulder infections (2, 3) and is among the most common pathogens isolated in shoulder periprosthetic joint infections (PJI) (4, 5). P. acnes has also been implicated in other biofilm-related infections (6-8), such as cardiovascular implantassociated infections (9), spinal osteomyelitis (10, 11), and endophthalmitis (12, 13).Diagnosis of P. acnes bone and joint infections is challenging since pain is often the only symptom (14, 15). For a long time, P. acnes was underdiagnosed in bone and joint infections due to the short cultivation time routinely used in diagnostic laboratories. In general, biofilm-forming bacteria are known to replicate at a slow rate due to low metabolism (16). Since recent studies recommended a prolonged cultivation time of up to 14 days for bone and joint infections (17, 18), the diagnosis of P. acnes infections has become more frequently documented (19). In view of the high costs of a long incubation period, a recent study suggested that 7 days of incubation should be sufficient for accurately diagnosing orthopedic implant-associated infections (20). In this study, 96.6% ...

If a bone or joint infection is suspected, perioperative antibiotic prophylaxis is frequently withheld until intraoperative microbiological sampling has been performed. This practice builds upon the hypothesis that perioperative antibiotics could render culture results negative and thus impede tailored antibiotic treatment of infections. We aimed to assess the influence of antibiotic prophylaxis within 30 to 60 min before surgery on time to positivity of microbiological samples and on proportion of positive samples in bone and joint infections. Patients with at least one sample positive for between January 2005 and December 2015 were included and classified as having an "infection" if at least 2 samples were positive; otherwise they were considered to have a sample "contamination." Kaplan-Meier curves were used to illustrate time to culture positivity. We found 64 cases with a infection and 46 classified as having a contamination. Application of perioperative prophylaxis significantly differed between the infection and contamination groups (72.8% versus 55.8%; < 0.001). Within the infection group, we found no difference in time to positivity between those who had or had not received a perioperative prophylaxis (7.07 days; 95% confidence interval [CI], 6.4 to 7.7, versus 7.11 days; 95% CI, 6.8 to 7.5; = 0.3). Also, there was no association between the proportion of sample positivity and the application of perioperative prophylaxis (71.6% versus 65.9%; = 0.39). Since perioperative prophylaxis did not negatively influence the microbiological yield in infections, antibiotic prophylaxis can be routinely given to avoid surgical site infections.

Introduction Periprosthetic joint infection (PJI) is a devastating complication following total joint replacement (TJR). Cutibacterium acnes (C. acnes) is a low virulent skin commensal, commonly found during TJR revision surgery for “aseptic” causes. The purpose of the present study was to report the treatment outcomes of patients with C. acnes contamination or infection in the presence of a TJR treated with a revision surgery ± implant exchange ± prolonged (≥ 8 weeks) postoperative antibiotics. Methods Medical records of patients with at least one positive C. acnes culture in intraoperative tissue samples or sonication fluid from a TJR revision surgery between January 2005 and December 2014 were retrospectively evaluated. The primary endpoint was infection eradication according to Delphi criteria. The diagnostic accuracy of preoperative TJR aspiration regarding the diagnosis of C. acnes PJI was also investigated. Results A total of 52 TJR (28 shoulders, 17 hips, 7 knees) in 52 patients (35 males, 17 females) with an average age of 63 ± 11 (33–86) years were included. At an average follow-up of 67 ± 33 (24–127) months, the infection eradication of C. acnes PJI was 97% regardless of the surgical treatment or administration of prolonged postoperative antibiotics. The incidence of unsuspected C. acnes PJI was 28.8%. The sensitivity and specificity of preoperative joint aspiration in detecting C. acnes PJI were 59% and 88%, whereas the PPV and NNV were 83% and 67%, respectively. Conclusion Infection eradication of C. acnes PJI was very high at a minimum follow-up of 24 months, suggesting that C. acnes PJI could be adequately treated with a combination of revision surgery and prolonged postoperative antibiotics. The preoperative diagnosis of C. acnes PJI might be challenging with more than one-quarter of patients presenting without suspicion of C. acnes PJI. The appropriate treatment of patients with a single positive culture remains still unclear. A negative TJR aspiration should not rule out a C. acnes PJI, especially in the presence of clinical correlates of infection. Level of evidence Retrospective case–control study, Level III. IRB approval Kantonale Ethikkommission Zürich, BASEC Nr.:2017-00567.