Propionibacterium acnes biofilm is present in intervertebral discs of patients undergoing microdiscectomy.
2017
Background In previous studies, Propionibacterium acnes was
cultured from intervertebral disc tissue of similar to 25% of
patients undergoing microdiscectomy, suggesting a possible link
between chronic bacterial infection and disc degeneration.
However, given the prominence of P. acnes as a skin commensal,
such analyses often struggled to exclude the alternate
possibility that these organisms represent perioperative
microbiologic contamination. This investigation seeks to
validate P. acnes prevalence in resected disc cultures, while
providing microscopic evidence of P. acnes biofilm in the
intervertebral discs. Methods Specimens from 368 patients
undergoing microdiscectomy for disc herniation were divided
into several fragments, one being homogenized, subjected to
quantitative anaerobic culture, and assessed for bacterial
growth, and a second fragment frozen for additional analyses.
Colonies were identified by MALDI-TOF mass spectrometry and P.
acnes phylotyping was conducted by multiplex PCR. For a sub-set
of specimens, bacteria localization within the disc was
assessed by microscopy using confocal laser scanning and FISH.
Results Bacteria were cultured from 162 discs (44%), including
119 cases (32.3%) with P. acnes. In 89 cases, P. acnes was
cultured exclusively; in 30 cases, it was isolated in
combination with other bacteria (primarily coagulase-negative
Staphylococcus spp.) Among positive specimens, the median P.
acnes bacterial burden was 350 CFU/g (12 - similar to 20,000
CFU/g). Thirtyeight P. acnes isolates were subjected to
molecular sub-typing, identifying 4 of 6 defined phylogroups:
IA1, IB, IC, and II. Eight culture-positive specimens were
evaluated by fluorescence microscopy and revealed P. acnes in
situ. Notably, these bacteria demonstrated a biofilm
distribution within the disc matrix. P. acnes bacteria were
more prevalent in males than females (39% vs. 23%, p = 0.0013).
Conclusions This study confirms that P. acnes is prevalent in
herniated disc tissue. Moreover, it provides the first visual
evidence of P. acnes biofilms within such specimens, consistent
with infection rather than microbiologic contamination.
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