Bacteriolytic and bactericidal activity of sera and synovial fluids in rheumatoid arthritis and in osteoarthritis

In vitro effect of synovial fluid from patients undergoing arthroplasty surgery on MRSA biofilm formation

BACKGROUND

Bacterial biofilm is a key component in the pathogenesis of prosthetic joint infection (PJI). Synovial fluid has been shown to have inhibitory activity against planktonic bacteria. However, the contribution of synovial fluid in prevention of Staphylococcus aureus (including MRSA) planktonic and biofilm forms is unknown.

OBJECTIVES

To test the antibacterial and antibiofilm activities of synovial fluid, including that containing cefazolin, against MSSA and MRSA.

MATERIALS AND METHODS

We determined the antiplanktonic and antibiofilm activities of synovial fluid collected from patients given preoperative cefazolin while undergoing elective arthroplasty surgery. MICs of cefazolin were determined for planktonic and biofilm cultures of biofilm-forming strains of MSSA and MRSA.

RESULTS

Synovial fluid inhibited planktonic and biofilm cultures of MSSA and MRSA. Cefazolin-containing synovial fluid had greater antibacterial and antibiofilm activities than the same cefazolin concentration in glucose LB (GLB) broth. MSSA and MRSA MICs of cefazolin suspended in synovial fluid were 0.7 mg/L. The MICs of cefazolin diluted in GLB broth were higher, measuring 1.4 mg/L for MSSA and 23 mg/L for MRSA.

CONCLUSIONS

Synovial fluid containing cefazolin inhibited biofilm- and planktonic-state MRSA cultures. This may explain the apparent effect of cefazolin in the prevention of MRSA PJI.

Staphylococcal persistence due to biofilm formation in synovial fluid containing prophylactic cefazolin

Antibiotic prophylaxis is standard for patients undergoing surgical procedures, yet despite the wide use of antibiotics, breakthrough infections still occur. In the setting of total joint arthroplasty, such infections can be devastating. Recent findings have shown that synovial fluid causes marked staphylococcal aggregation, which can confer antibiotic insensitivity. We therefore asked in this study whether clinical samples of synovial fluid that contain preoperative prophylactic antibiotics can successfully eradicate a bacterial challenge by pertinent bacterial species. This study demonstrates that preoperative prophylaxis with cefazolin results in high antibiotic levels. Furthermore, we show that even with antibiotic concentrations that far exceed the expected bactericidal levels, Staphylococcus aureus bacteria added to the synovial fluid samples are not eradicated and are able to colonize model implant surfaces, i.e., titanium pins. Based on these studies, we suggest that current prophylactic antibiotic choices, despite high penetration into the synovial fluid, may need to be reexamined.

Current concepts in the treatment of rheumatoid arthritis

The treatment of RA is complex and often frustrating. The pathologic process of RA is composed of acute inflammation, chronic immunologic phenomenon, and chronic connective tissue degradation. It is important to understand not only the pathophysiology of RA but also the mechanism of action of our therapeutic drugs so that treatment can be tailored to affect the important aspects of the process leading to end-organ damage. Despite the many drugs available, therapy is still unsatisfactory. Many drugs work in only certain patients. This could be secondary to variability in the disease state or to difference in drug metabolism. A better understanding of both disease and therapeutic agents may lead to better use of our present agents and development of new, more effective treatment modalities.

Mechanisms of action of gold

Since the successful introduction of injectable gold compounds for the treatment of rheumatoid arthritis over 50 years ago, numerous studies on the possible mechanism of action have been performed. This heavy metal has been show to possess a bewildering array of biological effects. Studies using gold performed both in vitro and in vivo can be grouped into anti-microbial, anti-immunologic, anti-inflammatory, anti-enzymatic and other effects. In this survey, we have analyzed these multiple approaches to the study of the mechanism of action of injectable gold preparations and apply the findings to rheumatoid arthritis.

Serum lysozyme, antinuclear factors and antibody to native DNA

This work was done in order to investigate the previously reported antinuclear property of lysozyme (LZM). Addition of human or hen egg white lysozyme (hLZM or eLZM) to normal serum and to 11 sera with different types of antinuclear factors (ANF) produced no consistent changes in ANF titre or type. Likewise, absorption of LZM from the sera with bentonite failed to influence ANF titre and, finally, hLZM and eLZM were incapable of binding native DNA (nDNA). Elevated serum lysozyme levels in rheumatic diseases are therefore unlikely to produce false-positive results in tests for antinuclear antibodies.

Death rate and causes of death in patients with rheumatoid arthritis

Patients with rheumatoid arthritis, 500 males and 500 females, aged 40 years or over, and an age- and sex-matched control population were observed over a 3-year period. During the follow-up, 122 RA patients and 69 controls had died. The most common causes of death in RA patients were cardiovascular diseases (57 patients), renal failure (27 patients), infections (19 patients), and malignant neoplasms (11 patients); in the controls, the respective data are: cardiovascular diseases (35 people), malignant neoplasms (21 people), accidents (7 people), and infections (5 people).