Diagnosing Biofilm Infections
Polymicrobial infections are associated with poorer outcomes, but are vastly underestimated by culture methods
Credit: CDC/ Rodney M. Donlan, Ph.D.; Janice Haney Carr
Biofilms foster tolerance to both antibiotics and host immune defenses, and multiple factors complicate biofilm chronic joint infection diagnosis and therefore treatment, including:
- Biofilm growth characteristics
- Sampling tools and techniques
- Inherent limitations of culture — such as difficulty growing biofilms, VNBC bacteria, and delayed incubation of specimens
With some 80% of PJI associated with polymicrobial biofilms, MicroGenDX is working hard to provide you the best tools for PJI diagnosis. Read More
Biofilm growth characteristics
- Biofilms growing on implant or tissue surfaces may be limited to one area or proliferate to multiple areas, so full coverage sampling is necessary to capture the diverse microbial community at the site
- When biofilms mature, cells disperse from the original microcolony and can also be detected in synovial fluid — however, the low presence of dispersal in synovial fluid alone may lead to negative results
The inherent limitations of culture
- Bacteria from biofilms can exhibit impaired growth in culture — even when the species involved are readily culturable, and permissive conditions are used
- Human pathogens can resuscitate from a VBNC state without losing their virulence after escaping culture detection
- Bacteria viability can be affected by delayed specimen incubation: Over 50% of revision specimens are incubated outside of the 2-hr window required by protocol
Sampling tools and techniques
Full sampling coverage provides best results: implants, medial and lateral gutters, as well as the intramedullary canal are all potential biofilm growth areas that will need to be swabbed. Proper sampling technique is critical for accurate and actionable OrthoKEY results. View videos
References
- Ehrlich GD, DeMeo P, et al. Culture-Negative Infections Orthopedic Biofilm Infections, Springer Series on Biofilms 7. DOI 10.1007/978-3-642-29554-6_2
- Taha M, Abdelbary H, et al. New Innovations in the Treatment of PJI and Biofilms—Clinical and Preclinical Topics. Curr Rev Musculoskelet Med. 2018 Sep; 11(3): 380–388. 1007/s12178-018-9500-5
- Blevins K M, GoswamiK, ParviziThe Journey of Cultures Taken During Revision Joint Arthroplasty: Preanalytical Phase. J Bone Jt Infect. 2019 May 21;4(3):120-125. doi: 10.7150/jbji.32975. eCollection 2019
- Li L, Mendis N, et al. The importance of the viable but non-culturable state in human bacterial pathogens. t Microbiol. 2014 Jun 2;5:258. doi: 10.3389/fmicb.2014.00258
Next-gen DNA sequencing (NGS) can identify the multiple bacteria and fungi that make up a biofilm, which is a first step in addressing this challenge
- Microorganisms in free-living planktonic state.
- In seconds – Planktonic cells initiation attachment to each other.
- Within 24 hours – Microbes build a protective community with an extracellular matrix (EPS) of polysaccharides, proteins, and glycoproteins. Horizontal gene transfer strengthens antimicrobial resistance for the community.
- Within 72 hours – Biofilm matures. Aerobic and anaerobic bacteria occupy spaces with differed O2 levels, and nutrient limitations of the biofilm’s interior induce slow-growth or no-growth states.
- Bacteria will continually detach individually – or in clumps that can retain antimicrobial resistance – and establish other biofilm colonies.