Does dithiothreitol improve bacterial detection from infected prostheses? A pilot study.
BACKGROUND
Sonication and scraping of infected prostheses usually are used to improve diagnosis of prosthetic infections, reducing false negatives. Chemical methods that reduce biofilms also may allow higher levels of detection.


OBJECTIVE
We therefore asked: (1) Do dithiothreitol (DTT) and N-acetylcysteine (NAC) remove bacteria from biofilm formed on prosthetic materials? (2) Is bacterial recovery affected by differing DTT and NAC concentrations and incubation times? (3) Do treatments with DTT and NAC detach the same amounts of bacteria from biofilm on prosthetic materials as sonication and scraping? (4) Are these methods reproducible?


METHODS
We treated polyethylene and titanium discs covered by biofilm formed by Pseudomonas aeruginosa and Staphylococcus aureus with DTT or NAC solutions at different concentrations for different times. We compared colony counts of S aureus, P aeruginosa, Staphylococcus epidermidis and Escherichia coli after treatment with NAC, DTT, sonication and scraping. We determined colony counts after treatment of biofilm formed by one strain of S aureus and one of P aeruginosa on five discs of each material analyzed on the same day and on five discs analyzed on five consecutive days.


RESULTS
Mean colony counts (LogCFU/mL) obtained after treatment with 1 g/L DTT for 15 minutes (5.3) were similar to those after sonication (4.9) and greater than those obtaining by scraping (3.4) and treatment with 2 g/L NAC for 30 minutes (1.9). DTT and sonication showed good reproducibility.


CONCLUSIONS
Our data suggest that treatment of prostheses with DTT may be a reasonable alternative to sonication to improve detection of biofilm-associated bacteria and supplement conventional laboratory culturing techniques for diagnosing periprosthetic infections.
Laboratory of Clinical Chemistry and Microbiology, IRCCS Galeazzi Institute, 20161, Milan, Italy. lorenzo.drago@unimi.it
Lorenzo
L
Drago
Carlo Luca
CL
Romanò
Roberto
R
Mattina
Valentina
V
Signori
Elena
E
De Vecchi
D000111:Acetylcysteine / Q000008:administration & dosage; D001419:Bacteria / Q000302:isolation & purification*; D001431:Bacteriological Techniques / Q000379:methods; D018441:Biofilms; D004229:Dithiothreitol / Q000008:administration & dosage; D007595:Joint Prosthesis / Q000382:microbiology*; D010865:Pilot Projects; D013010:Sonication; D013997:Time Factors
D004229:Dithiothreitol; D000111:Acetylcysteine