BactoSonic

Implants improves the quality of life

Modern medicine has developed various implants to replace missing anatomical structure or biological function: joint prostheses, internal fixation devices, vascular prostheses, cardiac pacemakers and defibrillators, dental implants, neurosurgical shunts and breast implants. New devices are improved and optimized with regard to biocompatibility and functionality.

Biofilm infections – a challenge of modern medicine

With growing use of implants, modern medicine is facing an increasing risk of infections. Microorganisms on implant surface form biofilms, what makes them difficult to detect by conventional methods such as periprosthetic tissue cultures. For successful treatment of these infections accurate microbiological diagnosis is crucial. Such biofilms consist of an extracellular matrix of polymerized polysaccharide, in which bacteria are embedded (Fig. 1).

Figure 1 Formation of biofilm on implant surface

The microorganisms in biofilm are transformed in low metabolic, stationary growth state. Over weeks to months, depending on the type of microorganism, implant material and host, a complex three-dimensional structure develops, which consists of nutrition channels and rudimentary communication system resembling multicellular organism. Free-living (planktonic) bacteria are killed by antibiotics and the host defense system, while adherent (biofilm) bacteria can survive and persist in the extracellular matrix of the biofilm (Fig. 2).

Figure 1 Formation of biofi lm on implant surface

Sonication – a new diagnostic method

After removal in the operating room, implants are placed in the air-tight container and transported to the microbiological laboratory. After addition of Ringer’s solution, the implant is processed by vortexing (30 seconds) and sonication (1 minute) to dislodge (planktonize) microorganism into the surrounding fluid (sonicate). The sonication fluid is cultured on aerobic and anaerobic agar plates (Fig. 3) and inoculated in broth media.

Figure 3 Sonication removes more than 99.9 % of the biofilm bacteria from the surface

Principle of sonication

High acoustic intensity of conventional ultrasound baths kills microorganisms (especially gram-negative and
anaerobic bacteria). Sonication in the specially designed ultrasound bath BactoSonic® uses low frequency and
low intensity ultrasound at the threshold of microbubble formation (cavitation).
Due micro-currents of sonication fluid, shear forces and oscillating cavitation bubbles biofilm is removed and the bacteria are disaggregated.

Figure 4 Sonication removes the detection of bacteria up to 10,000 times compared to periprosthetic tissue cultures

The resulting cavitation energy is reduce to the level, that no significant cell destruction occurs, enabling culture of viable microorganisms.

Figure 2 Bacteria in biofi lm resist antibiotics and defense system

Advantages of sonication

• High accuracy
With low-intensity sonication, microorganisms are dislodged from the implant but not killed, enabling high sensitivity of conventional cultures (Fig. 4). Particularly difficult to detect microorganisms (including small-colony variants), individual morphotypes and mixed infections can be better detected. The sensitivity is particularly improved in patients receiving previous antibiotics, due to better survival of bacteria in biofilm. Ultrasound reaches through surrounding fluid the whole implant surface, which is associated with high specificity.

• Rapid result
Sonication increases microbial growth by inducing micro-currents in the sonication fluid, thereby shortening the microbial detection time.

• Quantiative biofilm assessment
Since bacteria survive, but not replicate in the sonication fluid, quantitative assessment of removed biofi lm is possible.
The microbial density is expressed as number of colony-forming units (CFU) per ml of sonication fluid.

• Additional investigations

The sonication fluid contains high density of bacteria, making it suitable for further microbial (e.g. PCR, MALDI-TOF, microcalorimetry) and immunological analyses (e.g. determination of biomarkers, gene expression).

Scope of delivery – ready-to-use

The BactoSonic® includes an ultrasonic bath BS 14, different sizes of implant containers, corresponding holders, other accessories and standard operating procedure of the sonication.

Figure 3 Sonication removes more than 99.9 % of the biofi lm
bacteria from the surface

Figure 4 Sonication removes the detection of bacteria up to 10,000 times compared to peri prosthetic
tissue cultures

References

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2. Holinka J, Bauer L, Hirschl AM, Graninger W, Windhager R, Presterl E. Sonication cultures of explanted components as an add-on test to routinely conducted microbiological diagnostics improve pathogen detection. J Orthop Res 2011; 29: 617-622.

3. Holinka J, Pilz M, Hirschl AM, Graninger W, Windhager R, Presterl E. Differential bacterial load on components of total knee prosthesis in patients with prosthetic joint infection. Int J Artif Organs 2012; 35:735-41.

4. Mason PK, Dimarco JP, Ferguson JD, Mahapatra S, Mangrum JM, Bilchick KC, Moorman JR, Lake DE, Bergin JD. Sonication of explanted cardiac rhythm management devices for the diagnosis of pocket infections and asymptomatic bacterial colonization. Pacing Clin Electrophysiol 2011; 34: 143-149.

5. Nelson CL, Jones RB, Wingert NC, Foltzer M, Bowen TR. Sonication of Antibiotic Spacers Predicts Failure during Two-stage Revision for Prosthetic Knee and Hip Infections. Clin Orthop Relat Res 2014.

6. Oliva A, Nguyen BL, Mascellino MT, D‘Abramo A, Iannetta M, Ciccaglioni A, Vullo V, Mastroianni CM. Sonication of explanted cardiac implants improves microbial detection in cardiac device infections. J Clin Microbiol. 2013; 51: 496-502.

7. Piper KE, Jacobson MJ, Cofi eld RH, Sperling JW, Sanchez-Sotelo J, Osmon DR, Steckelberg JM, Mandrekar JN, Fernandez SM, Patel R. Microbiologic diagnosis of prosthetic shoulder infection using implant sonication. J Clin Microbiol 2009; 47: 1878-1884.

8. Portillo ME, Salvadó M, Sorli L, Alier A, Martínez S, Trampuz A, Gómez J, Puig L, Horcajada JP. Multiplex PCR of sonication fluid accurately differentiates between prosthetic joint infection and aseptic failure. J Infect 2012; 65: 541-548.

9. Portillo ME, Salvadó M, Sorli L, Trampuz A, Plasencia V, Rodriguez-Villasante M, Puig L, Horcajada JP. Sonication versus vortexing of removed implants for diagnosis of prosthetic joint infection. J Clin Microbiol 2013; 51: 591-594.

10. Portillo ME, Salvadó M, Alier A, Sorli L, Martínez S, Horcajada JP, Puig L. Prosthesis failure within 2 years of implantation is highly predictive of infection. Clin Orthop Relat Res 2013; 471: 3672-8.

11. Portillo ME, Salvadó M, Alier A, Martínez S, Sorli L, Horcajada JP, Puig L. Advantages of sonication fl uid culture for the diagnosis of prosthetic joint infection. J Infect 2014.

12. Rieger UM, Mesina J, Kalbermatten D, Haug M, Frey HP, Pico R, Frei R, Pierer G, Lüscher NJ, Trampuz A. Capsular contracture is associated with bacterial biofi lms on breast implants. Brit J Surg 2013; 100: 768-774.

13. Rohacek M, Weisser M, Kobza R, Schoenenberger A, Pfyff er G, Frei R, Erne P, Trampuz A. Bacterial colonization and infection of electrophysiologic cardiac devices detected with sonication and swab culture. Circulation 2010; 121: 1691-1697.

14. Sampedro MF, Huddleston PM, Piper KE, Karau MJ, Dekutoski MB, Yaszemski MJ, Currier BL, Mandrekar JN, Osmon DR, McDowell A, Patrick S, Steckelberg JM, Patel R. A biofi lm approach to detect bacteria on removed spinal implants. Spine 2010; 35: 1218-1224.

15. Trampuz A., Piper KE, Jacobson MJ, Hanssen AD, Unni KK, Osmon DR, Mandrekar JN, Cockerill FR, Steckelberg JM, Greenleaf JF, Patel R. Sonication of removed hip and knee prostheses for diagnosis of infection. N Engl J Med2007; 357: 654-663.

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