There are two other ways the a shoulder can meet the the ICM criteria for a definite shoulder periprosthetic infection that do not require positive cultures: "Gross intra-articular pus" and "Presence of a sinus tract from the skin surface to the prosthesis". One should ask, how can such cases of "definite" infection be culture negative?
One answer is that the cultures were negative even though live organisms were present. This situation could arise
(1) if the tissue sampling missed the parts of the shoulder containing live bacteria (at least five different tissue samples are recommended to reduce this risk)
(2) if the culture media were not appropriate (aerobic, anaerobic and both media are recommended for Cutibacterium)
(3) if the time of observation was too short (17 days of observation is recommended for Cutibacteriium)
(4) if prior antibiotic treatment (systemic or topical) prevented the growth of bacteria in culture (antibiotics should be held for two weeks prior to harvesting of specimens)
(5) if the samples were inadvertently placed in media containing antibacterial agents (attention needs to be directed to avoiding "bacteriostatic" saline, for example).
(6) if the bacteria are too fastidious to grow in vitro.
(7) if the infection is caused by fungus, yeast or tuberculosis (see Mycobacterium tuberculosis infection of reverse shoulder arthroplasty)(Shoulder arthroplasty complicated by Mycobacterium tuberculosis infection)
The other possibility is that even though there was intra-articular pus or a sinus track, there were no live organisms present. This might arise in cases of metal allergy, "cement disease", or "detritic synovitis" as in the case below (see this link).
The International Consensus Meeting found that 5% to 34% of shoulder infections were "culture negative. " The ICM recommended an "empirical antibiotic regimen as per an infectious disease specialist considering the local organism profile" for these cases.
Comment: We have a lot to learn about failed shoulder arthroplasties that look like they're infected but do not have positive cultures. It remains to be seen whether PCR or next generation sequencing and metal allergy testing can help resolve the cause of some of these failures.
===
We have a new set of shoulder youtubes about the shoulder, check them out at this link.
Use the "Search" box to the right to find other topics of interest to you.
You may be interested in some of our most visited web pages arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'
