Dithiotreitol pre-treatment of synovial fluid samples improves microbiological counts in peri-prosthetic joint infection

Abstract

Purpose Synovial fluid cultures of periprosthetic joint infections (PJI) may be limited by bacteria living in the fluids as biofilm-aggregates. The antibiofilm pre-treatment of synovial fluids with dithiotreitol (DTT) could improve bacterial counts and microbiological early stage diagnosis in patients with suspected PJI. Methods Synovial fluids collected from 57 subjects, affected by painful total hip or knee replacement, were divided into two aliquots, one pre-treated with DTT and one with normal saline. All samples were plated for microbial counts. Sensitivity of cultural examination and bacterial counts of pre-treated and control samples were then calculated and statistically compared. Results Dithiothreitol pre-treatment led to a higher number of positive samples, compared to controls (27 vs 19), leading to a statistically significant increase in the sensitivity of the microbiological count examination from 54.3 to 77.1% and in colony-forming units count from 1884 ± 2.129 CFU/mL with saline pre-treatment to 20.442 ± 19.270 with DTT pre-treatment (P = 0.02). Conclusions To our knowledge, this is the first report showing the ability of a chemical antibiofilm pre-treatment to increase the sensitivity of microbiological examination in the synovial fluid of patients with peri-prosthetic joint infection. If confirmed by larger studies, this finding may have a significant impact on routine microbiological procedures applied to synovial fluids and brings further support to the key role of bacteria living in biofilm-formed aggregates in joint infections.

Bacteria Living in Biofilms in Fluids: Could Chemical Antibiofilm Pretreatment of Culture Represent a Paradigm Shift in Diagnostics?

“…Arthrocentesis can show whether a joint effusion is inflammatory or not, but microbiological confirmation is needed to rule out or identify an infection. Recent reports have linked the resistance of bacterial joint infections to standard therapies to the presence of bacteria and biofilm aggregates floating in the SF [ 7 , 21 , 22 ]. With reported sensitivities as low as 45% [ 23 ], the poor efficacy of existing microbiological tests on SF may be explained by the ability of bacteria to reside in biofilm aggregates.…”

“…In a recent work by Drago et al [ 7 ], it was shown that the ability of bacteria to live in aggregates in the SF may be a common behavior among several if not all bacteria. They collected SF from 57 subjects affected by a painful total hip or knee replacement, with suspicions of a PJI; then, the samples were divided into two aliquots, one pretreated with dithiothreitol (DTT), and one with normal saline.…”

“…For this reason, the presence of bacteria in PJI synovial fluids may play a significant role in the emergence of a chronic illness that is challenging to identify and manage; therefore, the use of effective antibiofilm pretreatments, as was just discussed, could be effective in increasing cultural examination sensitivity and yield [ 7 ].…”

“…The main purpose of routine diagnostic procedures, including culture-based methods, is to find planktonic (free-floating) germs. Because planktonic and biofilm-associated bacteria differ from one another inherently, these techniques frequently miss biofilms or misjudge their number [ 7 ]. Bacteria in biofilms, for example, can become metabolically dormant and therefore “unculturable” using traditional methods.…”

“…It has been observed recently that bacteria can form biofilms in fluids such as synovial fluid, urine, cerebrospinal fluid, blood, mucus, saliva, and feces [ 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. Numerous environmental elements further influence the biofilm development process in biological fluids: bacterial adhesion, microcolony formation, and maturation can be impacted by variables like pH, oxygen tension, temperature, and fluid shear forces [ 14 ].…”