Prevalence of Propionibacterium acnes in Intervertebral Discs of Patients Undergoing Lumbar Microdiscectomy: A Prospective Cross-Sectional Study
2016
Background The relationship between intervertebral disc
degeneration and chronic infection by Propionibacterium acnes
is controversial with contradictory evidence available in the
literature. Previous studies investigating these relationships
were under-powered and fraught with methodical differences;
moreover, they have not taken into consideration P. acnes'
ability to form biofilms or attempted to quantitate the
bioburden with regard to determining bacterial counts/genome
equivalents as criteria to differentiate true infection from
contamination. The aim of this prospective cross-sectional
study was to determine the prevalence of P. acnes in patients
undergoing lumbar disc microdiscectomy. Methods and Findings
The sample consisted of 290 adult patients undergoing lumbar
microdiscectomy for symptomatic lumbar disc herniation. An
intraoperative biopsy and pre-operative clinical data were
taken in all cases. One biopsy fragment was homogenized and
used for quantitative anaerobic culture and a second was frozen
and used for real-time PCR-based quantification of P. acnes
genomes. P. acnes was identified in 115 cases (40%),
coagulase-negative staphylococci in 31 cases (11%) and
alpha-hemolytic streptococci in 8 cases (3%). P. acnes counts
ranged from 100 to 9000 CFU/ml with a median of 400 CFU/ml. The
prevalence of intervertebral discs with abundant P. acnes (>=
1x10(3) CFU/ml) was 11% (39 cases). There was significant
correlation between the bacterial counts obtained by culture
and the number of P. acnes genomes detected by real-time PCR (r
= 0.4363, p<0.0001). Conclusions In a large series of patients,
the prevalence of discs with abundant P. acnes was 11%. We
believe, disc tissue homogenization releases P. acnes from the
biofilm so that they can then potentially be cultured, reducing
the rate of false-negative cultures. Further, quantification
study revealing significant bioburden based on both culture and
real-time PCR minimize the likelihood that observed findings
are due to contamination and supports the hypothesis P. acnes
acts as a pathogen in these cases of degenerative disc disease.
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