301. The Use of Multiplex Touchdown PCR to Genotype Cutibacterium (Propionibacterium) acnes Isolated from Periprosthetic Shoulder Infections

BACKGROUND: As biogeographic surveys of the human skin microbiome have shown that C. acnes is a major component of the residential axillary microflora, the organism is frequently isolated from synovial tissue and joint aspirates obtained from patients with suspected periprosthetic shoulder infections. We hypothesized that multilocus sequence typing (MLST) applying a prior validated rapid high through-put multiplex PCR protocol would segregate C. acnes into distinctive phylogroups associated with periprosthetic infections compared with commensal strains. METHODS: C. acnes collected between 2015 and 2017 were correlated with the presence or absence of infection in a detailed retrospective chart review. To determine the C. acnes genotype, bacterial genomic DNA isolated from a single patient isolate served as template in a six locus multiplex touchdown PCR assay using organism-specific primers targeting six genes (16S rRNA, ATPase, sodA, Fic toxin, aspD and recA). Isolates were classified as a contaminant in the absence of multiple positive cultures from an anatomic site and without corresponding clinical, laboratory and histopathologic correlates of infection. The assignment of a diagnosis of prosthetic joint infection (PJI) conformed to the definition recommended by the IDSA Clinical Practice Guidelines of PJI. RESULTS: Of the C. acnes recovered from 94 patients, 14 (14.9%) were from patients with shoulder implants of which shoulder PJI was present in 10 individuals (10.6% of the total). The remaining 84 (89.4%) isolates were retrieved from a variety of tissue and fluid samples of which the majority (65.5%) were deemed as contaminants. Overall, phylogroups IA1, IB, and II predominated (79.8%). Although a similar genetic profile was present in all of the shoulder isolates, no phylogroup association was detected with PJI (P < 0.72). No genetic difference was present in the lineage of strains not causing PJI compared with those responsible for PJI (P < 0.25). CONCLUSION: Our results mirror those from a previous investigation using a less robust four gene MLST PCR based scheme that showed a lack of a phylogenetic association with shoulder PJI. Our results are a reflection of the phylogroup composition of the circulating C. acnes sequence types in our community. DISCLOSURES: All authors: No reported disclosures.