Identification of Cartilage Microbial DNA Signatures and Associations With Knee and Hip Osteoarthritis

OBJECTIVE

Alterations of the gut microbiota have been implicated in many forms of arthritis, but an examination of cartilage microbial patterns has not been performed. This study was undertaken to characterize the microbial DNA profile of articular cartilage and determine changes associated with osteoarthritis (OA).

METHODS

We performed 16S ribosomal RNA gene deep sequencing on eroded and intact cartilage samples from knee OA patients (n = 21 eroded and 21 intact samples) and hip OA patients (n = 34 eroded and 33 intact samples) and cadaver controls (n = 10 knee samples and 10 hip samples). Microbial DNA diversity was assessed, groups were compared, and metagenomic profiles were reconstructed. Confirmation was performed in an independent cohort by clade-specific quantitative polymerase chain reaction. Findings in human cartilage were compared to those in cartilage from OA-susceptible C57BL/6 (B6) mice and OA-resistant MRL/MpJ (MRL) mice. Germ-free B6 mouse cartilage was analyzed as a methodologic control.

RESULTS

Alpha diversity was reduced in human OA versus control samples (P < 0.0001), and in hip versus knee samples (P < 0.0001). Numerous clades were different in human OA versus control samples, and similar findings were noted in comparisons of murine B6 versus MRL mice. Hip samples were microbiologically distinct from knee samples. OA microbial DNA demonstrated increased gram-negative constituents (P = 0.02). Functional analysis demonstrated increases in lipopolysaccharide production (P = 9.9 × 10-3 ), phosphatidylinositol signaling (P = 4.2 × 10-4 ), and nitrogen metabolism (P = 8 × 10-3 ) and decreases in sphingolipid metabolism (P = 7.7 × 10-4 ) associated with OA.

CONCLUSION

Our study reveals a microbial DNA signature in human and mouse cartilage. Alterations in this signature, including increases in gram-negative constituents, occur during the development and progression of human OA. Furthermore, our findings indicate that strain-specific signatures exist within mouse cartilage that mirror human patterns. Further study of the establishment and potential pathogenic role of these DNA signatures is needed.

Induced apoptosis of chondrocytes by Porphyromonas gingivalis as a possible pathway for cartilage loss in rheumatoid arthritis

The role of bacterial infections in the pathogenesis of rheumatoid arthritis (RA) has gained increasing interest. Patients with RA often exhibit periodontal disease, which is associated with pathogens like Porphyromonas gingivalis. The present study examines the direct effects of P. gingivalis on apoptosis of human chondrocytes (a feature of inflammatory joint diseases) as one can assume an interrelation of pathogenesis of RA and P. gingivalis infections. Primary chondrocytes were infected with P. gingivalis. Early apoptotic and dead cell analysis was performed using Annexin-V, 7AAD, and propidium iodide and examined by flow cytometry and fluorescence microscopy. Caspase activation and DNA fragmentation were determined by western blot analysis and TUNEL reaction. Flow cytometry and fluorescence microscopy demonstrated an increase of Annexin-V-positive early apoptotic chondrocytes after infection. Western blot showed upregulation of activated caspase-3 expression, and TUNEL reaction revealed considerable DNA fragmentation following infection. The data show that P. gingivalis promotes early and later stages of apoptosis of primary human chondrocytes, which might contribute to the joint damage seen in the pathogenesis of RA.

Septic arthritis in Western and sub-Saharan African children - a review

This article reviews what is known about the incidence, aetiology, presentation, bacteriology and management of septic arthritis in children. It compares where possible the different presentations and characteristics of this condition in the Western and sub-Saharan African regions.

Role of aggrecanase 1 in Lyme arthritis

OBJECTIVE

Arthritis is one of the hallmarks of late-stage Lyme disease. Previous studies have shown that infection with Borrelia burgdorferi, the causative agent of Lyme disease, results in degradation of proteoglycans and collagen in cartilage. B burgdorferi do not appear to produce any exported proteases capable of digesting proteoglycans and collagen, but instead, induce and activate host proteases, such as matrix metalloproteinases (MMPs), which results in cartilage degradation. The role of aggrecanases in Lyme arthritis has not yet been determined. We therefore sought to delineate the contribution of aggrecanases to joint destruction in Lyme arthritis.

METHODS

We examined the expression patterns of aggrecanases 1 and 2 (ADAMTS 4 and 5, respectively) in B burgdorferi-infected primary human chondrocyte cell cultures, in synovial fluid samples from patients with active Lyme arthritis, and in the joints of mice by real-time quantitative reverse transcription-polymerase chain reaction and immunoblotting techniques. Bovine cartilage explants were used to determine the role of aggrecanases in B burgdorferi-induced cartilage degradation.

RESULTS

ADAMTS-4, but not ADAMTS-5, was induced in human chondrocytes infected with B burgdorferi. The active forms of ADAMTS-4 were increased in synovial fluid samples from patients with active Lyme arthritis and were elevated in the joints of mice infected with B burgdorferi. Using cartilage explant models of Lyme arthritis, it appeared that the cleavage of aggrecan was predominantly mediated by "aggrecanases" rather than MMPs.

CONCLUSION

The induction of ADAMTS-4 by B burgdorferi results in the cleavage of aggrecan, which may be an important first step that leads to permanent degradation of cartilage.

Effect of selected wound antiseptics on adult articular cartilage (bovine sesamoid bone) in the presence of Escherichia coli and Staphylococcus aureus

After removing an inoculum of 10(8)-10(9) cfu of Escherichia coli (E. coli) or Staphylococcus aureus (S. aureus) effectively within 2 h from bovine sesamoid bones (bsb) using the iodophore Betaisodona [0.5 and 1.0% (v/v) PVP-I], the biguanide polihexanide (PHMB) [0.005 and 0.01% (v/v)], and the bispyridinamine Octenidine (Oct) [0.005 and 0.01% (v/v)] the metabolic effect on proteoglycans (PG) in bsb was investigated by subsequent culture of bsb for 7 d and biosynthetically labeling with (35)S-sulfate for a period of 24 h. The treatment with the iodophore stimulates the incorporation of (35)S-sulfate into PG, whereas that of Oct was toxic. The PHMB treatment was both tolerated and effective only when it was used at low concentrations (0.005%). The antiseptic treatment did not result in an increase of catabolism of PG. This in vitro study clearly demonstrates that irrigation of cartilage with an antiseptic should be limited to an effective concentration and treatment time compatible with antiseptic function. Iodophores have no negative feedback on cartilage metabolism, moreover, they stimulate chondrocytes in vitro. Cationic antiseptics are not suited as irrigating solutions.

Production of endogenous antibiotics in articular cartilage

OBJECTIVE

Defensins are broad-spectrum antimicrobial peptides that are components of innate immunity. To date, only epithelial surfaces and blood cells have been shown to produce these cationic peptides in bactericidal concentrations when challenged with microorganisms or inflammatory cytokines. Infections caused by gram-negative pathogens occur only infrequently in association with joint surgery. The present study was undertaken to investigate whether this may be explained by intraarticular production of gram-negative-specialized antimicrobial peptides.

METHODS

Healthy articular cartilage and cultured T/C-28a2 chondrocytes were assessed, by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry, for expression of various antimicrobial peptides. The expression of human beta-defensin 2 (HBD-2) was studied in cultured chondrocytes after exposure to bacterial supernatants and proinflammatory cytokines and was assayed by real-time RT-PCR and immunoblot analysis. A septic arthritis mouse model was used to investigate the regulation of the murine homolog of HBD-2 in articular cartilage after bacterial inoculation.

RESULTS

Healthy articular cartilage and T/C-28a2 chondrocytes were able to produce different antimicrobial peptides. After exposure to gram-negative bacteria and proinflammatory cytokines, expression of cartilage-derived HBD-2 strongly increased. Immunoblot analysis revealed up-regulation of the gram-negative-specialized HBD-2 in microbicidal doses. Immunohistochemistry analysis revealed induction of the murine homolog of HBD-2 in vivo after intraarticular injection of bacteria.

CONCLUSION

This study demonstrated a previously unrecognized function of human chondrocytes. In addition to its biomechanical properties, articular cartilage has the ability to produce antimicrobial substances when challenged with microorganisms. The expression of HBD-2 in microbicidal doses suggests that antimicrobial peptides may contribute to host defense mechanisms in articular joints.

In vitro action of combinations of selected antimicrobial agents and adult bovine articular cartilage (sesamoid bone)

Anatomically intact articular cartilage in form of sesamoid bones from metacarpophalangeal joints of 2-year-old cows was tested for its influence on the microbicidal effect of the iodophore Betaisodona, the bispyridinamine Octenisept, and the biguanide Lavasept. Comparisons were carried out in Ham's F12 medium with and without 0.2% bovine serum albumin as organic matter loading. The expected abolition of the microbicidal effect of these antiseptics against the test organisms Escherichia coli or Staphylococcus aureus in the presence of sesamoid bone was not evident. Furthermore, sesamoid bone alone demonstrated antibacterial activity against Staphylococcus aureus, which may involve adherence of bacteria to surface constituents of articular cartilage. Final concentrations of 2.5-5% Betaisodona, 5% Octenisept as well as 0.025% Lavasept are effective in killing of 10(8)-10(9) cfu/ml Escherichia coli or Staphylococcus aureus in the presence of sesamoid bone without the reduction of antimicrobial activity expected from binding to CS, which has previously been demonstrated for CS in solution.

Legionella pneumophila Arthritis: use of medium specific for Mycobacteria for isolation of L. pneumophila in culture of articular fluid specimens

We report the first case, to our knowledge, of acute purulent arthritis due to Legionella pneumophila in an immunosuppressed patient. L. pneumophila was isolated from samples of blood and articular fluid cultured with use of medium specific for mycobacteria (Bactec 13A medium).

Update: Unexplained deaths following knee surgery--Minnesota, 2001

Since November 13, 2001, the Minnesota Department of Health (MDH), in collaboration with CDC, has been conducting an investigation of three patients who died unexpectedly within 1 week following knee surgery. Patient 1 had received a knee osteochondral allograft, and patients 2 and 3 had undergone total knee replacement surgery. Epidemiologic and microbiologic investigations have not linked the deaths of the three patients.

Influence of interferon-gamma administration on the severity of experimental group B streptococcal arthritis

OBJECTIVE

To assess the effect of interferon-gamma (IFNgamma) administration on the evolution of systemic infection and septic arthritis induced by group B streptococci (GBS) in mice.

METHODS

CD1 mice were inoculated intravenously with arthritogenic strain 1/82 of type IV GBS. Exogenous murine IFNgamma or anti-IFNgamma monoclonal antibodies were administered intravenously either 2 hours (-2 hours) before or 18 hours after infection with 1 x 10(7) GBS. Mice were monitored daily for survival and for signs of arthritis. In a subsequent set of experiments, mice were killed at selected times for examination of bacterial clearance, joint histopathology, and cytokine production.

RESULTS

Mortality in mice treated with IFNgamma at -2 hours was 100%, compared with 20% in those treated at 18 hours and with 40% in controls. As indicated by the arthritis score, mice treated with IFNgamma at -2 hours developed early and more severe arthritis, whereas those treated at 18 hours had milder arthritis compared with infected controls. Less severe joint pathology in the mice treated with IFNgamma at 18 hours correlated with low levels of interleukin-6 (IL-6) and IL-1beta and a low bacterial load in the joints, whereas rapid onset and worsening of articular lesions in those treated at -2 hours corresponded to early and sustained levels of IL-6.

CONCLUSION

The findings of this study demonstrate that the effects mediated by IFNgamma on GBS-induced arthritis may be detrimental or beneficial, depending on the time of administration of IFNgamma in relation to infection with the antigen.

Staphylococcus aureus-induced inflammation and bone destruction in experimental models of septic arthritis

Staphylococcus aureus is the most common cause of septic arthritis. This disease often leads to severe joint destruction and high mortality. An experimental model of S. aureus arthritis has been developed to study the course of inflammation and joint destruction, to elucidate the role of bacterial and host factors for joint pathology and mortality, and to develop therapeutical and preventive devices against septic arthritis and sepsis. Results show that the innate immune system is crucial in defending the host against staphylococcal infection while components of the specific immune system, T and B lymphocytes and their products, are detrimental to the host, mediating joint destruction and increasing mortality rates. Staphylococcal capsule polysaccharides, toxins, cell wall-attached adhesins and possibly also the chromosomal DNA are virulence determinants in S. aureus arthritis. Several vaccine candidates have recently been described which protects against staphylococcal infections, e.g. staphylococcal surface polysaccharides, enterotoxins devoid of their superantigenic properties and collagen adhesin. There are also new approaches suggested for treatment of ongoing infections, such as the combined use of antibiotics and corticosteroids.

[Pathogenetic aspects of chlamydia-associated urogenic arthritis: feasibility of microorganism reproduction in cells of articular cartilage]

AIM

The study of feasibility of Chlamydia trachomatis infection and reproduction. This microorganism is an essential etiologic factor in urogenic arthritis, in chondrocytes and fibroblasts of human skin.

MATERIALS AND METHODS

Infection of human skin chondrocytes and fibroblasts was made with chlamydia CP-1 strain isolated from joint fluid of the patient and serially passaged in the hen's embryo yolksacs. The inoculation results were assessed by direct staining with the use of monoclonal and fluorescent antibodies and hematoxiline.

RESULTS

Chlamydial infection of human skin connective tissue, chondrocytes of the auricular cartilage and fibroblasts in particular, is possible.

CONCLUSION

The findings confirm the ability of Chlamydia trachomatis to reproduce in the cartilage tissue.

Effect of synovial membrane infection in vitro on equine synoviocytes and chondrocytes

OBJECTIVE

To determine the functional response of synovium to infection, and the influence of infected synovium on articular cartilage metabolism.

SAMPLE POPULATION

Synovium and articular cartilage explants from the midcarpal and tarsocrural joints of adult horses.

PROCEDURE

For experiment 1, synovium explants were incubated as follows: control--incubation in standard medium, infected (I)--incubation with Staphylococcus aureus, and infected-filtered (IF)--incubation with medium collected from the infected group and filtered (0.22-micron filter). Daily collected medium was assayed for interleukin 1 beta (IL-1 beta), IL-6, tumor necrosis factor, and hyaluronan (HA) concentrations. For experiment 2, cartilage explants were incubated as follows: control--incubation in standard medium, and IF--incubation in medium collected from infected synovium cultures and filtered. After 48 hours, explant proteoglycan synthesis and endogenous proteoglycan and glycosaminoglycan contents were determined.

RESULTS

IL-1 beta and IL-6 values were significantly increased in synovium explants from the I and IF groups. Hyaluronan concentration was lower in I and IF groups. Proteoglycan synthesis and content, and total glycosaminoglycan and chondroitin sulfate concentrations, were significantly decreased in cartilage from the IF group.

CONCLUSIONS

Bacterial infection was associated with decreased HA concentration and increased mediator release. These effects were also observed despite elimination of bacteria. Exposure to sterile but previously infected medium decreased articular cartilage matrix synthesis and composition.

CLINICAL RELEVANCE

Resident synovial cells may contribute appreciably to articular damage during bacterial infection in the absence of migrant inflammatory cells. This response is prolonged despite elimination of the bacteria.

Blocking of TNF-alpha and IL-1 inhibits leukocyte infiltration at early, but not at late stage of S. aureus-induced arthritis and the concomitant cartilage destruction in rabbits

We investigated the involvement of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) in the pathogenesis of heat-killed S. aureus-induced arthritis. TNF-alpha and IL-1beta peaked at 2 and 24 hr after the injection, respectively. Leukocyte infiltration within 12 hr of the inflammation was significantly inhibited (80%) by coinjection of anti-TNF-alpha mAb and IL-1 receptor antagonist (IL-1Ra) with S. aureus; however, leukocyte infiltration at 24 hr and thereafter was not inhibited by these agents. The loss of proteoglycan in S. aureus-induced arthritis was also unchanged either by anti-TNF-alpha mAb, IL-1Ra, or their combination. These results indicate that direct participation of TNF-alpha and IL-1 in the pathogenesis of S. aureus-induced arthritis may be limited to the early stage of inflammation and blocking of these cytokines did not result in diminishing the severity of inflammation. Thus, therapeutic approaches with the objective to suppress TNF-alpha and IL-1 may not be effective in the clinical treatment of gram-positive bacteria-induced arthritis.

Effects of potentiated chlorhexidine on bacteria and tarsocrural joints in ponies

OBJECTIVES

To evaluate the bactericidal properties of chlorhexidine diacetate (CHD) after potentiation with EDTA and Tris buffer (EDTA-Tris), and to find a potentiated CHD concentration that would achieve 90 to 100% killing for all bacteria tested.

ANIMALS

6 adult ponies.

PROCEDURES

Serial dilutions of CHD, CHD in EDTA-Tris and EDTA-Tris alone were evaluated for bactericidal activity against Staphylococcus aureus, Escherichia coli, and Streptococcus zooepidemicus. The tarsocrural joints of 6 ponies were lavaged with either 1 L phosphate-buffered saline solution (control) or 1 L of 0.0005% CHD in EDTA-Tris. Synovial fluid was collected before lavage and on days 1,4, and 8. Synovia, cartilage, and bone with cartilage were collected on day 8 when the ponies were euthanatized.

RESULTS

In vitro results indicated that 0.0005% CHD in EDTA-Tris was 90% lethal to all bacteria tested. Results of synovial fluid analysis, glycosaminoglycan analysis, and histologic examination of the synovial membrane and articular cartilage indicated that joint lavage with 0.0005% CHD in EDTA-Tris was not detrimental to the synovium or the articular cartilage of pony tarsocrural joints. Changes observed were a result of the actual lavage process, the phosphate-buffered saline solution, and hemarthrosis.

CONCLUSIONS

A concentration of 0.0005% CHD in EDTA-Tris was 90% lethal to all bacteria tested. Pony tarsocrural joint lavage with 0.0005% CHD in EDTA-Tris was not detrimental to the synovium or the articular cartilage. The efficacy of 0.0005% CHD potentiated with EDTA-Tris as a potential joint lavage fluid for treatment of infectious arthritis needs to be evaluated in clinical patients.

Localization of viable bacteria and bacterial antigens in arthritic joints of Erysipelothrix rhusiopathiae-infected pigs

Chronic polyarthritis was induced in pigs by infection with Erysipelothrix rhusiopathiae (serovar 2, strain T28). Viable bacteria could be reisolated as long as 5 months post-infection from synovial fluid, synovial tissue and from isolated chondrocytes. The number of viable bacteria could be increased by hypotonic shock of the chondrocytes indicating a substantial intracellular amount of bacteria. Bacterial antigens were shown by immunohistochemistry to be present on the surface of both chondrocytes and synovial cells in arthritic joints. Neither viable bacteria nor bacterial antigen were detected in unaffected joints.

[Comparison of the effectiveness of sodium azide and merthiolate as bacteriocidal agents--a NMR study]

The pseudohalogenide sodium azide (NaN3) and the organometallic mercury compound merthiolate (sodium salt of ethyl mercurithiosalicylate) are commonly used as preserving solutions for biomaterials. In the present paper, these preserving solutions were compared for their efficacy in preserving porcine articular cartilage. For this purpose, porcine articular cartilage was incubated with phosphate buffer containing the corresponding amounts of NaN3 or merthiolate. Supernatants were assayed using NMR spectroscopy, and the content of soluble saccharides was determined using the dye Alcian blue. The results obtained clearly indicate that merthiolate is more effective than sodium azide. This makes the former a more suitable preserving agent for the storage of cartilage. A significant decrease in the lactate concentration, and enhancement of the acetate and the N-acetyl resonances indicate degenerative changes in the cartilage. However, when a large excess of sodium azide is used, its efficacy approaches that of merthiolate.

A collagen receptor on Staphylococcus aureus strains isolated from patients with septic arthritis mediates adhesion to cartilage

Staphylococcus aureus strains isolated from patients with septic arthritis or osteomyelitis possess a collagen receptor present in two forms, which contains either two or three copies of a 187-amino-acid repeat motif. Collagen receptor-positive strains adhered to both collagen substrata and cartilage in a time-dependent process. Collagen receptor-specific antibodies blocked bacterial adherence, as did preincubation of the substrate with a recombinant form of the receptor protein. Furthermore, polystyrene beads coated with the collagen receptor bound collagen and attached to cartilage. Taken together, these results suggest that the collagen receptor is both necessary and sufficient to mediate bacterial adherence to cartilage in a process that constitutes an important part of the pathogenic mechanism in septic arthritis.

Articular histoplasmosis

Rheumatic manifestations of histoplasmosis are uncommon. Polyarthritis or arthralgias may occur as a part of a sensitization process in primary acute histoplasmosis. Infectious arthritis may accompany disseminated histoplasmosis or occur as solitary monoarthritis. Treatment of the latter traditionally consists of surgical excision followed by amphotericin B. Reports of clinical experience with the newer triazole compounds in treating articular histoplasmosis are lacking. We describe a patient with solitary monoarticular histoplasmosis of the knee who was successfully treated with oral fluconazole and required no surgical intervention. Specific issues that pertain to clinical presentation and management of articular histoplasmosis are discussed.

Yersinia enterocolitica serotype 0:3-induced arthritis in mice: microbiological and histopathological information

Gross anatomical and histopathological changes in arthritic joints resulting from oral challenge with Yersinia enterocolitica serotype 0:3, upon pretreatment with desferrioxamine, were always more severe than those induced by intravenous infection of immunized animals. In all the acute inflammation episodes studied, live Yersiniae were isolated from the arthritic region. Invariably, a heavy mixed infiltration of synovia, joint spaces and soft tissues was observed at this stage. Concurrent fibrous thickening and vascular proliferation, along with erosion of articular cartilages and anomalous bone regeneration, were also apparent. In spite of these significant facts, the bacterium could be histopathologically identified only in bone marrow where it developed microcolonies and caused significant necrosis as well. The live bacterium was also retrieved from two- and six-month-old arthritic ankles/paws examined, but it could not be seen in histological sections of joints. By this time, no cellular infiltration was evident, but there was extensive fibrosis. Bones were at times greatly enlarged, showing a spongeous-like structure. Additionally, articular cartilages could be completely lost and were substituted by an anomalous ossification filling the joint spaces. This situation led to bone fusion, resembling articular ankylosing traits. In summary, we present the first experimental evidence that Y. enterocolitica serotype 0:3 is a causal agent of osteoarthritis and osteomyelitis, and that it may survive for prolonged periods of time in osseous structures.

Differential ability of wild-type and vaccine strains of rubella virus to replicate and persist in human joint tissue

Natural rubella has been reported to be associated with a higher incidence of arthropathy than immunisation with rubella vaccine. In addition, the different vaccines (HPV77/DE5, RA27/3, Cendehill) have been shown to vary in their association with joint symptoms in clinical trials. To investigate possible reasons for these differences in arthritogenicity, the susceptibility of human joint tissue to five rubella virus strains (three vaccines and two wt+) has been examined. Human joint tissue in either organ or dispersed cell-culture was infected in vitro and the degree of replication and persistence of each rubella strain compared. The wt+ strains (M33 and Therien) replicated to high titre in both cell and organ cultures and persisted for over 2 months. The HPV77/DE5 strain (Meruvax I) showed a very similar pattern. In contrast, the replication of RA27/3 (Meruvax II) and Cendehill (Cendevax) was highly restricted in joint cells and both of these strains showed very limited ability to penetrate and persist in the organ cultures. These results concur with the differences in arthritogenicity observed between the strains in vivo, suggesting that local viral replication may play a role in the pathogenesis of rubella-associated arthritis.

Detection of Mycoplasma pulmonis in arthritic joints of rats by indirect immunoperoxidase staining

Neonatal and 8-week-old rats were inoculated with Mycoplasma pulmonis. A portion of the animals developed polyarthritis. Indirect immunoperoxidase staining was used to identify the localization of M. pulmonis within arthritic joints. M. pulmonis antigen was most often observed within cartilage in the neonatal group and in synovial tissue in the 8-week-old group.

Staphylococcal adhesion to collagen in intra-articular sepsis

Ultrastructural studies of the cartilaginous articular surfaces of human and rabbit joints have shown that cartilage is the target substratum for adhesion by Staphylococcus aureus, leading to intra-articular sepsis. Transmission and scanning electron microscope studies demonstrated bacteria in intimate contact with acellular cartilage matrix surfaces, particularly with collagen fibres. Certain strains of Staphylococcus aureus used in these experiments reveal a high binding capacity to collagen that is derived from a cartilage matrix. These studies indicate that the pathogenesis of intra-articular sepsis is based on the ability of certain strains of staphylococci to bind preferentially to a cartilage matrix.

Natural history of acute septic arthritis in an avian model

An experimental model of acute septic arthritis is described, utilizing the injection of S. aureus into chicken hock joints. The course of the infection was monitored over a 14-day period by measurement of chicken growth rate, histopathology of the joint, number of bacteria, and number and type of leukocytes in the synovial fluid. Bacterial numbers decreased initially then increased rapidly over the first 24 h. Leukocyte counts rose sharply, starting between 60 and 90 min after injection. Gross destruction of articular cartilage was observed at 4 days, and appeared to be initiated by the adherence of the staphylococci to the cartilage surface followed by their penetration and invasion of vascular tunnels in the epiphyseal cartilage. Extensive (but focal) erosion of the articular surface was evident by 14 days.

Articular cartilage canals--a new pathogenetic mechanism in infectious arthritis

In experimentally-induced erysipelas polyarthritis, preexisting cartilage canals in articular cartilage play a crucial role during the very onset of the disease. This observation might have some implications for the pathogenesis of other infectious arthritides in young animals or even rheumatoid arthritis in man.

Degradation of bovine articular cartilage proteoglycans in vitro. The effect of Bacteroides gingivalis

The black-pigmented Bacteroides gingivalis has previously been isolated from periodontal pockets and been shown capable of inflicting advanced tissue damage. Its effect on the degradation of articular cartilage proteoglycans has not previously been known. In these experiments it was demonstrated that under aerobic conditions the anaerobic microbe B. gingivalis is very potent in degrading the proteoglycans of fresh articular cartilage. It is even more potent in the presence of fetal calf serum (FCS) than in its absence. When the cartilage has been frozen/thawed there is still a slight enhancement of the degradation by B. gingivalis, but when the cartilage has been devitalized and de-enzymed by heat, the cartilage-degrading capacity of B. gingivalis is totally abolished. However, addition to the cartilage cultures of filtered conditioned medium from B. gingivalis inhibits in some degree the degradation of articular cartilage proteoglycans. It is therefore suggested that the great cartilage-degrading ability of Bacteroides gingivalis shown in this culture system could be due to its ability to degrade proteinase inhibitors.

Localization of Mycoplasma pulmonis in cartilage

Transmission electron microscopy of articular cartilage in Mycoplasma pulmonis-infected neonatal rats revealed the presence of mycoplasmas within the matrix and lacunae. The mycoplasmas appeared to have a tropism for the chondrocytes and induced lysis of both the chondrocytes and matrix of the cartilage.

Staphylococcal septic arthritis in three horses

Three horses were diagnosed as having monarticular septic arthritis due to Staphylococcus aureus on the basis of culture of articular cartilage, synovial membrane and/or synovial fluid. The organisms were all well recognised human phage types and in two cases demonstrated beta-lactamase (penicillinase) activity. Details of case histories are presented and the bacteriological techniques and antibiotic management with cloxacillin, methicillin and penicillin discussed. Following treatment, sterile cultures of synovial fluid were achieved in all cases, but in two horses the infections resulted in degenerative articular changes. This necessitated arthrodesis of the fetlock joint in one case.