What is the clinical impact of positive cultures at the time of primary total shoulder arthroplasty?
These authors sought to determine differences in clinical outcomes based on culture positivity at the time of primary shoulder arthroplasty in 134 patients who underwent primary anatomic or reverse total shoulder arthroplasty.
In each case, 5 tissue samples were collected and processed in a single laboratory for culture on aerobic and anaerobic media for 13 days.
Minimum 2-year functional outcomes scores (American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form [ASES] and Single Assessment Numeric Evaluation [SANE]) and reoperation data were analyzed.
Forty-two (31.3%) patients had positive cultures (30 Cutibacterium and 21 with at least 2 positive cultures) at the time of surgery.
There was no statistically significant difference in postoperative functional outcome scores (ASES: 82.5 vs. 81.9; P ..89, SANE: 79.5 vs. 82.1; P . .54) between culture-positive and culture-negative cohorts.
There were no cases of infection. Two patients (4.8%; 2/42) with positive cultures required reoperation compared with 4 patients (5.6%; 4/71) without positive cultures.
Comment: This study demonstrates that substantial deep inoculation with Cutibacterium occurs in almost half (31/68) of male patients and 31% of all patients. In spite of this high rate of inoculation, the authors found no difference in two-year patient reported outcomes revision rates, revision rates or periprosthetic infections between the culture positive and culture negative groups. This finding suggests that the patients' defenses combined with routine surgical prophylaxis effectively manages the inoculated bacterial load in most cases.
In our practice, we assume that a large percentage of shoulder arthroplasty wounds - especially those of male patients - are inoculated with Cutibacterium. Particularly in patients known to be at higher risk for Cutibacterium periprosthetic infection (young males, prior surgery, strongly positive skin cultures obtained in the clinic for Cutibacterium), we often use additional methods of prophylaxis: topical antibiotics, Betadine lavage, and a short course of postoperative antibiotics). While at present there is a lack of evidence to support these adjunctive steps, we are committed to maximizing our efforts to minimize the risk of a devastating Cutibacterium periprosthetic infection.
These authors point out that the use of perioperative antibiotics or new preoperative skin preparations, such as BPO, intended to reduce the Cutibacterium burden may inadvertently affect the complex microbiome of the normal shoulder. There is evidence that proteins and fatty acids secreted by Cutibacterium may inhibit growth of organisms such as Staphylococcus (see this link and this link). For example, Cutimycin, a thiopeptide antibiotic produced by Cutibacterium, has been shown to inhibit Staphylococcus colonization of human follicles.
Of note, in a recent article, Benzoyl peroxide treatment decreases Cutibacterium acnes in shoulder surgery, from skin incision until wound closure, five patients in the study were subsequently treated for early deep surgical site infections. Three were from a group treated with preoperative benzoyl peroxide (BPO). Deep cultures from the these cases showed S. aureus in two and a mixture of S. epidermidis and Cutibacterium in the third. Even though this is a small sample, it is of interest that the bacterial distribution in the surgical site infections in patients treated with BPO is different than that in non-BPO treated patients. Both cases of surgical site infections in the non-BPO group hade growth of Cutibacterium only
In 1886 Robert Louis Stevenson wrote the gothic novel
It is able to thrive in the anoxic sebaceous gland by using proteases to liberate the amino acid arginine from skin proteins and lipases to degrade triglyceride lipids in sebum; this releases free fatty acids, which promote bacterial adherence. Sebum levels positively correlate with Cutibacterium abundance.
The relative abundance of skin microbial species, including Cutibacterium is restructured during puberty, a time when increased levels of hormones stimulate the sebaceous glands to produce additional sebum. Thus, the skin of postpubescent individuals favors the expansion of lipophilic microorganisms, such as bacterial Cutibacterium and Corynebacterium. By contrast, pre-pubescent children have greater abundances of Firmicutes (Streptococcaceae spp.), Bacteroidetes and Proteobacteria (betaproteobacteria and gammaproteobacteria) .
