The Expression of von Willebrand Factor-Binding Protein Determines Joint-Invading Capacity of Staphylococcus aureus, a Core Mechanism of Septic Arthritis

Septic arthritis, one of the most dangerous joint diseases, is predominantly caused by Staphylococcus aureus In contrast, coagulase-negative staphylococci are rarely found in septic arthritis. We hypothesize that coagulases released by S. aureus, including coagulase (Coa) and von Willebrand factor-binding protein (vWbp), play potent roles in the induction of septic arthritis. Four isogenic S. aureus strains differing in expression of coagulases (wild-type [WT] Newman, Δcoa, Δvwb, and Δcoa Δvwb) were used to induce septic arthritis in both wild-type and von Willebrand factor (vWF)-deficient mice. Septic arthritis severity was greatly reduced when wild-type mice were infected with the Δcoa Δvwb and Δvwb variants compared to WT or Δcoa strains, suggesting that vWbp rather than Coa is a major virulence factor in S. aureus septic arthritis. vWF-deficient mice were more susceptible to bone damage in septic arthritis, especially when the Δvwb strain was used. Importantly, no difference in arthritis severity between the Δvwb and WT strains was observed in vWF-deficient mice. Collectively, we conclude that vWbp production by S. aureus enhances staphylococcal septic arthritis.IMPORTANCE Septic arthritis remains one of the most dangerous joint diseases with a rapidly progressive disease character. Despite advances in the use of antibiotics, permanent reductions in joint function due to joint deformation and deleterious contractures occur in up to 50% of patients with septic arthritis. So far, it is still largely unknown how S. aureus initiates and establishes joint infection. Here, we demonstrate that von Willebrand factor-binding protein expressed by S. aureus facilitates the initiation of septic arthritis. Such effect might be mediated through its interaction with a host factor (von Willebrand factor). Our finding contributes significantly to the full understanding of septic arthritis etiology and will pave the way for new therapeutic modalities for this devastating disease.

From 'OPAT' to 'COpAT': implications of the OVIVA study for ambulatory management of bone and joint infection

Bone and joint infection contributes significantly to clinical activity within outpatient parenteral antimicrobial therapy (OPAT) services. The OVIVA (oral versus intravenous antibiotics for bone and joint infection) randomized study has challenged the practice of prolonged intravenous therapy, because non-inferiority of oral antibiotic therapy was demonstrated, thereby implying that early transition to oral therapy is an appropriate alternative to prolonged intravenous therapy. We examine the caveats to the study and discuss the implications for OPAT practice, highlighting the importance of careful oral antibiotic selection with attention to bioavailability, bone penetration, drug interactions, compliance and toxicity monitoring. We emphasize that ambulatory antibiotic therapy (whether intravenous or oral) in this patient group requires expert multidisciplinary management, monitoring and follow-up, and ideally should be undertaken within existing OPAT or, more accurately, complex outpatient antibiotic therapy (COpAT) services.

Strain-specific joint invasion and colonization by Lyme disease spirochetes is promoted by outer surface protein C

Lyme disease, caused by Borrelia burgdorferi, B. afzelii and B. garinii, is a chronic, multi-systemic infection and the spectrum of tissues affected can vary with the Lyme disease strain. For example, whereas B. garinii infection is associated with neurologic manifestations, B. burgdorferi infection is associated with arthritis. The basis for tissue tropism is poorly understood, but has been long hypothesized to involve strain-specific interactions with host components in the target tissue. OspC (outer surface protein C) is a highly variable outer surface protein required for infectivity, and sequence differences in OspC are associated with variation in tissue invasiveness, but whether OspC directly influences tropism is unknown. We found that OspC binds to the extracellular matrix (ECM) components fibronectin and/or dermatan sulfate in an OspC variant-dependent manner. Murine infection by isogenic B. burgdorferi strains differing only in their ospC coding region revealed that two OspC variants capable of binding dermatan sulfate promoted colonization of all tissues tested, including joints. However, an isogenic strain producing OspC from B. garinii strain PBr, which binds fibronectin but not dermatan sulfate, colonized the skin, heart and bladder, but not joints. Moreover, a strain producing an OspC altered to recognize neither fibronectin nor dermatan sulfate displayed dramatically reduced levels of tissue colonization that were indistinguishable from a strain entirely deficient in OspC. Finally, intravital microscopy revealed that this OspC mutant, in contrast to a strain producing wild type OspC, was defective in promoting joint invasion by B. burgdorferi in living mice. We conclude that OspC functions as an ECM-binding adhesin that is required for joint invasion, and that variation in OspC sequence contributes to strain-specific differences in tissue tropism displayed among Lyme disease spirochetes.

Infection by different Lyme disease bacteria is associated with different manifestations, such as cardiac, neurologic, or, in the case of B. burgdorferi, the major cause of Lyme disease in the U.S., joint disease. The basis for these differences is unknown, but likely involve strain-specific interactions with host components in the target tissue. The sequence of the outer surface lipoprotein OspC varies with the strains, and we found that this variation influences the spectrum of host extracellular matrix components recognized. Infection of mice with strains that are identical except for ospC revealed that OspC variants that differ in binding spectrum promote infection of different tissues. A strain producing OspC invaded and colonized the joint in living animals, but an altered OspC protein incapable of binding tissue components did not. Thus, tissue-binding by OspC is critical for infection and joint invasion, and OspC variation directly influences tissue tropism.

Surveillance of Extrapulmonary Nontuberculous Mycobacteria Infections, Oregon, USA, 2007-2012

Limited data are available describing extrapulmonary nontuberculous mycobacteria (NTM) infections in the general population. We describe results from statewide population-based laboratory surveillance in Oregon, USA, during 2007–2012. We defined a case of extrapulmonary NTM infection as >1 isolate from skin/soft tissue, disseminated sites, lymph node, joint, or other sites. The annual incidence of extrapulmonary NTM infection (other than Mycobacterium gordonae) was stable, averaging 1.5 cases/100,000 population. Median age of the 334 patients was 51 years, and 53% of patients were female. Half of cases were caused by M. avium complex, but rapid-growing NTM species accounted for one third of cases. Most extrapulmonary NTM infections are skin/soft tissue. Compared with pulmonary NTM infection, more extrapulmonary infections are caused by rapid-growing NTM species. the designation of NTM as a reportable disease in Oregon in 2014 will result in better detection of changes in the incidence and patterns of disease in the future.

Neutrophils: Beneficial and Harmful Cells in Septic Arthritis

Septic arthritis is an inflammatory joint disease that is induced by pathogens such as Staphylococcus aureus. Infection of the joint triggers an acute inflammatory response directed by inflammatory mediators including microbial danger signals and cytokines and is accompanied by an influx of leukocytes. The recruitment of these inflammatory cells depends on gradients of chemoattractants including formylated peptides from the infectious agent or dying cells, host-derived leukotrienes, complement proteins and chemokines. Neutrophils are of major importance and play a dual role in the pathogenesis of septic arthritis. On the one hand, these leukocytes are indispensable in the first-line defense to kill invading pathogens in the early stage of disease. However, on the other hand, neutrophils act as mediators of tissue destruction. Since the elimination of inflammatory neutrophils from the site of inflammation is a prerequisite for resolution of the acute inflammatory response, the prolonged stay of these leukocytes at the inflammatory site can lead to irreversible damage to the infected joint, which is known as an important complication in septic arthritis patients. Thus, timely reduction of the recruitment of inflammatory neutrophils to infected joints may be an efficient therapy to reduce tissue damage in septic arthritis.

[Pneumococcal arthritis in paediatric population]

OBJECTIVE

Cases of septic arthritis in paediatric population by Streptococcus pneumoniae in the Health Area of Santiago de Compostela (Spain) were reviewed.

METHODS

A retrospective study from January 2005 to March 2014 was conducted for all S. pneumoniae isolates obtained from joint fluids in children.

RESULTS

From the 7,416 joint fluids received in the Microbiology Department, 77 belonged to paediatric patients, and of these, only 8 had positive culture. In total, there were three positive cases for S. pneumoniae, two with positive culture and a third with positive antigen detection. In the three patients (two of them under 15 months) the affected joint was hip, antibiotic treatment was combined with surgical drainage and evolution was favourable.

CONCLUSIONS

We conclude that pneumococcal arthritis is an entity that must be taken into account since most cases of arthritis in paediatric population appear as a complication of bacteraemia after a common cold or an ear infection. The greatest risk of sequel is associated with delays in diagnosis, so it is essential clinical and microbiological early diagnosis.

Radiological features of experimental staphylococcal septic arthritis by micro computed tomography scan

BACKGROUND

Permanent joint dysfunction due to bone destruction occurs in up to 50% of patients with septic arthritis. Recently, imaging technologies such as micro computed tomography (μCT) scan have been widely used for preclinical models of autoimmune joint disorders. However, the radiological features of septic arthritis in mice are still largely unknown.

METHODS

NMRI mice were intravenously or intra-articularly inoculated with S. aureus Newman or LS-1 strain. The radiological and clinical signs of septic arthritis were followed for 10 days using μCT. We assessed the correlations between joint radiological changes and clinical signs, histological changes, and serum levels of cytokines.

RESULTS

On days 5-7 after intravenous infection, bone destruction verified by μCT became evident in most of the infected joints. Radiological signs of bone destruction were dependent on the bacterial dose. The site most commonly affected by septic arthritis was the distal femur in knees. The bone destruction detected by μCT was positively correlated with histological changes in both local and hematogenous septic arthritis. The serum levels of IL-6 were significantly correlated with the severity of joint destruction.

CONCLUSION

μCT is a sensitive method for monitoring disease progression and determining the severity of bone destruction in a mouse model of septic arthritis. IL-6 may be used as a biomarker for bone destruction in septic arthritis.

Use of MALDI-TOF mass spectrometry after liquid enrichment (BD Bactec™) for rapid diagnosis of bone and joint infections

Advantages of MALDI-TOF MS (MS) were evaluated for diagnosis of bone and joint infections after enrichment of synovial fluid (SF) or crushed osteoarticular samples (CSs). MS was performed after enrichment of SF or crushed osteoarticular samples CS (n = 108) in both aerobic and anaerobic vials. Extraction was performed on 113 vials (SF: n = 47; CS: n = 66), using the Sepsityper^® kit prior identification by MS. The performances of MS, score and reproducibility results on bacterial colonies from blood agar and on pellets after enrichment in vials, were compared. MS analysis of the vial resulted in correct identification of bacteria at a species and genus level (80.5% and 92% of cases, respectively). The reproducibility was superior for aerobic Gram-positive bacteria (Staphylococci and Gram-positive bacilli: 100% colonies), as compared to aerobic Gram-negative bacilli (89.7%), anaerobes (83.3%) and Streptococcus/Enterococcus (58.8%). MS performance was significantly better for staphylococci than for streptococci on all identification parameters. For polymicrobial cultures, identification (score>1.5) of two species by MS was acceptable in 92.8% of cases. Use of MS on enrichment pellets of bone samples is an accurate, rapid and robust method for bacterial identification of clinical isolates from osteoarticular infections, except for streptococci, whose identification to species level remains difficult.

[Septic arthritis in systemic lupus erythematosus: a retrospective analysis of 6 cases]

Base on the clinical characteristics of septic arthritis in a group of systemic lupus erythematosus patients, this study has found out that high systemic lupus erythematosus disease activity index, leucopenia, high cumulative dose of glucocorticoid, methylprednisolone intravenous pulse therapy and joint cavity puncture were closely correlated with septic arthritis. Once septic arthritis is suspected, culture specimens should be collected and appropriate antibiotics are suggested immediately. Also, surgical drainage is a very useful approach.

In Vivo Assessment of Phage and Linezolid Based Implant Coatings for Treatment of Methicillin Resistant S. aureus (MRSA) Mediated Orthopaedic Device Related Infections

Staphylococcus comprises up to two-thirds of all pathogens in orthopaedic implant infections with two species respectively Staphylococcus aureus and Staphylococcus epidermidis, being the predominate etiological agents isolated. Further, with the emergence of methicillin-resistant S. aureus (MRSA), treatment of S. aureus implant infections has become more difficult, thus representing a devastating complication. Use of local delivery system consisting of S.aureus specific phage along with linezolid (incorporated in biopolymer) allowing gradual release of the two agents at the implant site represents a new, still unexplored treatment option (against orthopaedic implant infections) that has been studied in an animal model of prosthetic joint infection. Naked wire, hydroxypropyl methylcellulose (HPMC) coated wire and phage and /or linezolid coated K-wire were surgically implanted into the intra-medullary canal of mouse femur bone of respective groups followed by inoculation of S.aureus ATCC 43300(MRSA). Mice implanted with K-wire coated with both the agents i.e phage as well as linezolid (dual coated wires) showed maximum reduction in bacterial adherence, associated inflammation of the joint as well as faster resumption of locomotion and motor function of the limb. Also, all the coating treatments showed no emergence of resistant mutants. Use of dual coated implants incorporating lytic phage (capable of self-multiplication) as well as linezolid presents an attractive and aggressive early approach in preventing as well as treating implant associated infections caused by methicillin resistant S. aureus strains as assessed in a murine model of experimental joint infection.

Porphyromonas gingivalis facilitates the development and progression of destructive arthritis through its unique bacterial peptidylarginine deiminase (PAD)

Rheumatoid arthritis and periodontitis are two prevalent chronic inflammatory diseases in humans and are associated with each other both clinically and epidemiologically. Recent findings suggest a causative link between periodontal infection and rheumatoid arthritis via bacteria-dependent induction of a pathogenic autoimmune response to citrullinated epitopes. Here we showed that infection with viable periodontal pathogen Porphyromonas gingivalis strain W83 exacerbated collagen-induced arthritis (CIA) in a mouse model, as manifested by earlier onset, accelerated progression and enhanced severity of the disease, including significantly increased bone and cartilage destruction. The ability of P. gingivalis to augment CIA was dependent on the expression of a unique P. gingivalis peptidylarginine deiminase (PPAD), which converts arginine residues in proteins to citrulline. Infection with wild type P. gingivalis was responsible for significantly increased levels of autoantibodies to collagen type II and citrullinated epitopes as a PPAD-null mutant did not elicit similar host response. High level of citrullinated proteins was also detected at the site of infection with wild-type P. gingivalis. Together, these results suggest bacterial PAD as the mechanistic link between P. gingivalis periodontal infection and rheumatoid arthritis.

Clinical and epidemiological data indicates that chronic periodontal disease (PD), one of the most prevalent infectious inflammatory disease of mankind, is linked to systemic inflammatory diseases such as cardiovascular diseases (CVD), rheumatoid arthritis (RA) and chronic obstructive pulmonary disease (COPD). Nevertheless, the causative mechanisms of association between PD and chronic inflammatory diseases are very poorly understood. Recent findings suggest a causative link between periodontal infection and rheumatoid arthritis via bacteria-dependent induction of a pathogenic response to citrullinated epitopes. In present study we show that infection with viable periodontal pathogen Porphyromonas gingivalis but not another oral bacterium (Prevotella intermedia), exacerbated CIA, as manifested by earlier onset, accelerated progression and enhanced severity of the disease, including significantly increased bone and cartilage destruction. The ability of P. gingivalis to augment CIA was dependent on the expression of a unique enzyme peptidylarginine deiminase, which converts arginine residues in proteins to citrulline. This knowledge may create new perspectives in the treatment and prevention of RA in susceptible individuals.

The link between ankylosing spondylitis, Crohn's disease, Klebsiella, and starch consumption

Both ankylosing spondylitis (AS) and Crohn's disease (CD) are chronic and potentially disabling interrelated conditions, which have been included under the group of spondyloarthropathies. The results of a large number of studies support the idea that an enteropathic pathogen, Klebsiella pneumoniae, is the most likely triggering factor involved in the initiation and development of these diseases. Increased starch consumptions by genetically susceptible individuals such as those possessing HLA-B27 allelotypes could trigger the disease in both AS and CD by enhancing the growth and perpetuation of the Klebsiella microbes in the bowel. Exposure to increased levels of these microbes will lead to the production of elevated levels of anti-Klebsiella antibodies as well as autoantibodies against cross-reactive self-antigens with resultant pathological lesions in the bowel and joints. Hence, a decrease of starch-containing products in the daily dietary intake could have a beneficial therapeutic effect on the disease especially when used in conjunction with the currently available medical therapies in the treatment of patients with AS and CD.

Tissue tropism of Ornithobacterium rhinotracheale in chickens determined by culture and nucleic acid detection

The aim of the present study was to evaluate the ability of Ornithobacterium rhinotracheale (ORT) to colonize chosen organs of chicks infected intratracheally (group A1), or intravenously (group A2), with the use of bacteriological methods and PCR. The bacteriological methods enabled to reisolate ORT bacteria from trachea and lungs of the birds from group A1 only on day 3 and 6 after infection. The PCR technique additionally detected the bacterial genetic material in these organs on the 9th day after infection, and gave positive results in the samples from air sacs until the 6th day of the experiment. In birds infected intravenously (A2) ORT was reisolated from liver on day 3 and from spleen on day 3 and 6 after infection, whereas the reisolation from the tibiotarsal joint occurred during the entire experimental period. PCR enabled to detect the bacterial DNA in the liver, spleen and lungs of chickens until the 9th day after infection and in case of tibiotarsal joint during the whole time of the study.

Borrelia burgdorferi requires glycerol for maximum fitness during the tick phase of the enzootic cycle

Borrelia burgdorferi, the spirochetal agent of Lyme disease, is a vector-borne pathogen that cycles between a mammalian host and tick vector. This complex life cycle requires that the spirochete modulate its gene expression program to facilitate growth and maintenance in these diverse milieus. B. burgdorferi contains an operon that is predicted to encode proteins that would mediate the uptake and conversion of glycerol to dihydroxyacetone phosphate. Previous studies indicated that expression of the operon is elevated at 23°C and is repressed in the presence of the alternative sigma factor RpoS, suggesting that glycerol utilization may play an important role during the tick phase. This possibility was further explored in the current study by expression analysis and mutagenesis of glpD, a gene predicted to encode glycerol 3-phosphate dehydrogenase. Transcript levels for glpD were significantly lower in mouse joints relative to their levels in ticks. Expression of GlpD protein was repressed in an RpoS-dependent manner during growth of spirochetes within dialysis membrane chambers implanted in rat peritoneal cavities. In medium supplemented with glycerol as the principal carbohydrate, wild-type B. burgdorferi grew to a significantly higher cell density than glpD mutant spirochetes during growth in vitro at 25°C. glpD mutant spirochetes were fully infectious in mice by either needle or tick inoculation. In contrast, glpD mutants grew to significantly lower densities than wild-type B. burgdorferi in nymphal ticks and displayed a replication defect in feeding nymphs. The findings suggest that B. burgdorferi undergoes a switch in carbohydrate utilization during the mammal to tick transition. Further, the results demonstrate that the ability to utilize glycerol as a carbohydrate source for glycolysis during the tick phase of the infectious cycle is critical for maximal B. burgdorferi fitness.

Borrelia burgdorferi is the vector-borne pathogen that causes Lyme disease. It has a complex life cycle that involves growth in a tick vector and a mammalian host — two diverse environments that present B. burgdorferi with alternative carbohydrate sources for support of growth. Previous studies suggested that glycerol may be an important nutrient in the tick vector. Here we show that genes predicted to be involved in glycerol metabolism have significantly elevated expression during all tick stages. Repression of expression in the mammalian host is dependent on the alternative sigma factor, RpoS. A mutant that cannot convert glycerol into dihydroxyacetone phosphate to support glycolysis was able to infect mice. In contrast, the mutant was present at significantly lower levels in nymphal ticks, its replication was delayed during nymphal feeding and longer feeding times were required for transmission from nymph to mouse. The results demonstrate that the ability to utilize glycerol as a carbohydrate source for glycolysis during the tick phase of the infectious cycle is critical for maximal B. burgdorferi fitness.

What are we doing about septic arthritis? A survey of UK-based rheumatologists and orthopedic surgeons

This study aims to determine the current practices and beliefs of United Kingdom (UK)-based rheumatologists and orthopedic surgeons (OS) in managing septic arthritis (SA) and to determine awareness levels of national guidance. Two-hundred OS and 200 rheumatologists were sent a link to a web-based survey tool via email. Questions posed related to the management of SA, including the respondent's views on antibiotic therapy, joint drainage, which specialty should manage these cases, and also the clinician's evidence base. There were 354 functioning addresses with 182 responses (51%). One hundred fifty-one (77 OS, 74 rheumatologists) (43%) responses were complete and included for analysis. Eighty percent of rheumatologists and 82% of OS recommended 6-weeks total antibiotic therapy. Seventy-three percent in each group recommended 1-2 weeks intravenous therapy initially followed by oral continuation therapy. In patients at risk of methicillin-resistant Staphylococcus aureus (MRSA), 25% rheumatologists and 14% OS would ensure MRSA cover. Seventy-seven percent of rheumatologists and 66% of OS recommended surgical joint drainage; 22% and 27%, respectively, recommended repeated closed needle aspiration as their chosen method of joint drainage. Sixty-six percent of rheumatologists and 65% of OS believed OS should manage SA. Twenty-three percent of rheumatologists and 22% of OS quoted published guidance as their main evidence base in the treatment of SA. Only 24% of rheumatologists and 34% of OS quoted British Society of Rheumatology (BSR) guidance when asked if they were aware of any guidelines. Views of rheumatologists and OS are not that dissimilar in managing SA. Surprisingly, rheumatologists are more aggressive regarding the recommendation for surgical joint drainage. Within both groups, significant variation in management principles exists often discrepant to recommendations laid out by the BSR. There are poor awareness levels of the BSR guidelines.

Are bacterial load and synovitis related in dogs with inflammatory stifle arthritis?

It has been proposed that small quantities of microbial material within synovial joints may act as a trigger for development of synovitis. We have previously identified an association between intra-articular bacteria and development of inflammatory stifle arthritis and cranial cruciate ligament rupture (CCLR) in dogs, and now wished to quantify bacterial load and markers of synovitis in dogs with and without stifle arthritis and CCLR. Joint tissues were collected from dogs with CCLR (n=51) and healthy dogs with normal stifles (n=9). Arthritis was assessed radiographically in CCLR dogs. Bacterial load was assessed using qPCR and broad-ranging 16S rRNA primers. qRT-PCR was used to estimate expression of the T lymphocyte antigen receptor (TCR Vβ), CD3ɛ, tartrate-resistant acid phosphatase (TRAP), IL-4, IL-17, and TNF-α genes. Severity of synovitis was assessed histologically. Bacterial load was increased in arthritic stifles, when compared with healthy stifles. Histologic synovitis in arthritic stifles was mononuclear and was significantly correlated with bacterial load (1 of 2 primer sets) (S(R)=0.49, p<0.001). In arthritic stifles, expression of TRAP in synovium was increased relative to healthy stifles. Expression of pro-inflammatory genes was not correlated with bacterial load, histologic inflammation, or radiographic arthritis. Translocation of bacterial material to the canine stifle is related to the presence of joint inflammation. The lack of a strong positive correlation suggests that bacterial load is unlikely to be a primary pro-inflammatory factor. However, dysregulation of immune responses within synovial tissues may be dependent upon an environmental microbial trigger.

A mouse model of post-arthroplasty Staphylococcus aureus joint infection to evaluate in vivo the efficacy of antimicrobial implant coatings

BACKGROUND

Post-arthroplasty infections represent a devastating complication of total joint replacement surgery, resulting in multiple reoperations, prolonged antibiotic use, extended disability and worse clinical outcomes. As the number of arthroplasties in the U.S. will exceed 3.8 million surgeries per year by 2030, the number of post-arthroplasty infections is projected to increase to over 266,000 infections annually. The treatment of these infections will exhaust healthcare resources and dramatically increase medical costs.

METHODOLOGY/PRINCIPAL FINDINGS

To evaluate novel preventative therapeutic strategies against post-arthroplasty infections, a mouse model was developed in which a bioluminescent Staphylococcus aureus strain was inoculated into a knee joint containing an orthopaedic implant and advanced in vivo imaging was used to measure the bacterial burden in real-time. Mice inoculated with 5x10(3) and 5x10(4) CFUs developed increased bacterial counts with marked swelling of the affected leg, consistent with an acute joint infection. In contrast, mice inoculated with 5x10(2) CFUs developed a low-grade infection, resembling a more chronic infection. Ex vivo bacterial counts highly correlated with in vivo bioluminescence signals and EGFP-neutrophil fluorescence of LysEGFP mice was used to measure the infection-induced inflammation. Furthermore, biofilm formation on the implants was visualized at 7 and 14 postoperative days by variable-pressure scanning electron microscopy (VP-SEM). Using this model, a minocycline/rifampin-impregnated bioresorbable polymer implant coating was effective in reducing the infection, decreasing inflammation and preventing biofilm formation.

CONCLUSIONS/SIGNIFICANCE

Taken together, this mouse model may represent an alternative pre-clinical screening tool to evaluate novel in vivo therapeutic strategies before studies in larger animals and in human subjects. Furthermore, the antibiotic-polymer implant coating evaluated in this study was clinically effective, suggesting the potential for this strategy as a therapeutic intervention to combat post-arthroplasty infections.

Rare coexistence of gouty and septic arthritis: a report of 14 cases

OBJECTIVES

To analyse the characteristic features of patients with coexistence of gouty arthritis and pyarthrosis at our university hospital in southern Taiwan, an area with high prevalence of hyperuricemia and gout.

METHODS

A retrospective chart review was performed for patients who had concomitant gouty and septic arthritis from July 1998 to June 2008. Clinical and laboratory data of these patients were analysed. Furthermore, a comparison was made with published cases in English literature.

RESULTS

Fourteen cases with coexistence of gouty arthritis and pyarthrosis have been identified during the past 10 years. There were 13 male and 1 female, all of Han Chinese in ethnicity, with ages ranging from 45 to 85 and an average of 63.7 years. At disease presentation, there were 11 oligoarticular cases (78.6%), 2 monoarticular cases (14.3%) and 1 polyarticular case (7.1%). Ankle and knee joints were most commonly involved. Bacteriological analyses demonstrated gram-positive cocci in 12 cases, of these 10 were oxacillin-sensitive Staphylococcus aureus (71.4%). Multiple tophi deposition was noted in 13 patients (92.9%) and among them 11 patients (84.6%) had associated chronic kidney disease.

CONCLUSION

Different clinical presentations and bacteriological characteristics have been identified in the present series. While the mechanisms responsible for such a coexistence remain to be elucidated, these cases underline the importance of thorough evaluation of the aspirated synovial fluid. Our report adds a novel insight into the understanding of the clinical and microbiological manifestations of such a rare concurrence of gouty and septic arthritis.

In vivo sortase A and clumping factor A mRNA expression during Staphylococcus aureus infection

The Staphylococcus aureus cell surface protein clumping factor A (ClfA) and the enzyme sortase A (SrtA), which attach surface proteins to the cell wall, have both been shown to be virulence factors in models of septic arthritis and sepsis. The mRNA levels of clfA, srtA and the putative housekeeping gene gyrase B (gyrB) in S. aureus were determined using real-time PCR during the course of sepsis/septic arthritis. Expression was measured in joints, being a target of localized infection, and in kidneys, representing a systemic compartment. In infected kidneys, the mRNA levels of clfA, srtA and gyrB were all decreasing over time, from day 3 of infection to day 14. The transcript numbers of clfA and srtA decreased faster in septic mice than in mice with a non-septic disease. The mRNA levels of clfA and gyrB in joints, though, were increasing during the course of infection. These differences suggest that the specific tissue environment is decisive for the differentiation of staphylococci. Also, there was a negative relationship between bacterial load in a tissue and the numbers of clfA, srtA and gyrB transcripts per colony-forming unit. Possibly enters the majority of bacteria a metabolically dormant steady state at high bacterial loads.

Evaluation of 99mTc-UBI 29-41 scintigraphy for specific detection of experimental Staphylococcus aureus prosthetic joint infections

PURPOSE

(99m)Tc-UBI 29-41 (UBI), an antimicrobial peptide, specifically targets bacteria. We tested the ability of UBI to discriminate between infected and uninfected prosthetic joints using a rabbit model previously validated.

METHODS

Left knee arthroplasty was performed on 20 New Zealand rabbits, then 10(7) cfu of S. aureus (n = 12) or sterile saline (n = 8) was injected into the joint. On days 9 and 20 after surgery, planar UBI scintigraphy was performed in six infected and four uninfected rabbits, 1 h and 4 h p.i. (150 MBq), on a gamma camera. Operated-to-normal knee activity ratio (ONKR) was calculated on each scintigram. Then, after sacrifice, tissue samples of both knees were counted in a gamma counter.

RESULTS

One rabbit injected with sterile saline had cutaneous infection at sacrifice and was excluded from analysis. ONKR was higher in infected than in uninfected animals 4 h p.i. 20 days after surgery: 1.75 +/- 0.48 vs 1.13 +/- 0.11, p = 0.04. From 1 h to 4 h p.i., ONKR increased in 9/12 infected and 0/7 uninfected animals. According to UBI uptake intensity and kinetics, scintigraphy was truly positive in all infected cases on day 9 and in four of six infected cases on day 20. It was truly negative in two of three sterile inflamed prosthetic knees on day 9, and in all cases on day 20. Biodistribution studies revealed increased UBI uptake in periprosthetic tissues in all animals 9 days after surgery, and only in infected animals on day 20.

CONCLUSION

In this experimental study, (99m)Tc-UBI 29-41 scintigraphy permitted the early detection of acute prosthetic joint infection, and exclusion of infection in chronic sterile prosthetic joint inflammation.

State-of-the-Art Treatment of Coccidioidomycosis Skeletal Infections

Coccidioidomycosis is a fungal infection endemic to the southwestern United States. Typically a respiratory illness, coccidioidomycosis can rarely present as extrapulmonary infection. Skeletal coccidioidomycosis occurs in 20% to 50% of disseminated infections. Skeletal coccidioidomycosis is a chronic and progressive infection that eventually results in bone destruction and loss of function and often involves adjacent structures, such as joints, muscles, and tendons and other soft tissues. Sinus tract formation may occur. This infection may be multifocal. Although radiographs, white blood cell count scans, and other imaging methods identify and define relevant abnormalities, histopathologic examination with culture of the involved bone is the only means to confirm the diagnosis. Serologic testing is adjunctive, and complement fixation titers can be evaluated serially to assess response to treatment. A number of studies addressing the efficacy of various antifungal agents have been performed, and the results of these studies as they pertain to skeletal coccidioidomycosis are summarized herein. Among the various studies, response rates ranged from 23% to 100%, but relapse was common. A combination of medical therapy-often, itraconazole or fluconazole-and surgical débridement is often needed to control skeletal coccidioidomycosis. Early diagnosis and treatment are critical to avoid long-term problems with chronically infected bones and joints. Anatomical issues, diagnostic studies, and data related to treatment of this form of extrapulmonary coccidioidomycosis are reviewed in this article.

Mice lacking CD21 and CD35 proteins mount effective immune responses against Borrelia burgdorferi infection

CD21/35(-/-) mice, deficient in CD21 and CD35 (complement receptors 2 and 1, respectively), were infected with Borrelia burgdorferi to assess the role of these receptors in a chronic bacterial infection. Although CD21/35(-/-) mice on both C57BL/6 and BALB/c backgrounds produced less B. burgdorferi-specific antibodies than did wild-type mice, spirochete levels and arthritis severity were similar.

A case of isolated and transient splenial lesion of the corpus callosum associated with disseminated Staphylococcus aureus infection

We report a 20-year-old man who presented with temporary encephalopathy. Serial brain MRI revealed an isolated and transient splenial lesion of the corpus callosum (SCC). He was subsequently diagnosed with septic metastasis of Staphylococcus aureus (S. aureus) involving both lungs and multiple joints; however, there was no indication of S. aureus involvement of the meninges or brain parenchyma in CSF and MRI studies. Within 24 h of presentation, the serum sodium concentration and effective osmolality changed by approximately 10 mmol/L and 25 mOsm/kg H(2)O, respectively. On the basis of the MRI findings, the changes in electrolyte concentration, and a review of relevant literature, an isolated and transient SCC in this case might be related to osmotic demyelination caused by fluid imbalance rather than direct invasion of S. aureus.

Short report: Association of macrophage inflammatory response and cell death after in vitro Borrelia burgdorferi infection with arthritis resistance

Susceptibility to Borrelia burgdorferi infection and subsequent arthritis is genetically determined in mice and determined by innate immunity. Accordingly, macrophage responses to B. burgdorferi challenge may differ between mouse strains. Bone marrow-derived macrophages were infected ex vivo with clonal B. burgdorferi strain N40. Interleukin-12 and tumor necrosis factor-alpha (TNF-alpha) production were higher in macrophages from resistant C57Bl/6 mice than in macrophages from susceptible C3H/HeJ mice. However, TNF-alpha production was observed in lower concentrations in C3H/HeJ (toll-like receptor-4(-/-)) macrophages than in C3H/FeJ (TLR4(+/+)) macrophages, suggesting that TLR4 might contribute to the response to B. burgdorferi. A higher cytokine response to B. burgdorferi was associated with cell death in macrophages from resistant C57Bl/6 mice. Understanding variability in the response of macrophages to B. burgdorferi may contribute to understanding Lyme arthritis.

Soft tissue and joint infection

Soft tissue infection may be acute or chronic and may be introduced by the haematogenous route, or by inoculation, including surgical infection, or spread from other areas. The spectrum of infecting organism differs in primary infection, in immunodeficiency or when foreign bodies, including prostheses, are present. Bacterial infections are usually more rapid than those due to fungi or atypical organisms. Inflammation usually begins as cellulitis, proceeding through necrosis to cavitation and abscess formation, sometimes complicated by haemorrhage. Imaging, apart from MRI in selected cases, is rarely helpful in the early stages, but early diagnosis of pyomyositis and necrotizing fasciitis is mandatory. When infection is established, US, CT and MRI all have individual value in diagnosis, including biopsy, and in directing therapy, including percutaneous or surgical drainage or debridement. Both MRI and CT are best suited to monitoring progress. Septic arthritis presents as rapidly progressive, destructive arthritis, and early diagnosis is essential to prevent long-term morbidity. Ultrasound offers the best method of detecting early joint effusion and synovial thickening, but aspiration is usually required for diagnosis. In more advanced stages CT is valuable for revealing destructive changes, and MRI for documenting intra-articular changes and detecting inflammation in surrounding bone.

Persistent joint swelling and borrelia-specific antibodies in Borrelia garinii-infected mice after eradication of vegetative spirochetes with antibiotic treatment

We wanted to study the pathogenesis and the long-term manifestations of Borrelia garinii infection in SJL and C3H/He mice. We report here that B. garinii A218 causes a persisting infection in these mouse strains. Mice infected with intracutaneous inoculation of B. garinii at 4-5 weeks of age developed a disseminated infection and joint swelling within 2 weeks of inoculation and remained infected with joint symptoms until the end of follow-ups of up to 52 weeks. Treatment with ceftriaxone or ampicillin at 18 or 44 weeks of infection did not affect the joint swelling during the follow-ups of 19 and 8 weeks, respectively. However, B. garinii could not be cultured from any of the post mortem tissue samples of the treated mice, whereas the spirochete grew from samples of all untreated infected animals. Borrelia-specific IgG antibodies were detectable after 2 weeks of infection, and in late infection, all mice had high anti-borrelia IgG levels. Antibiotic treatment had no effect on antibody levels. Histology showed only slight changes in the joints of the infected mice with occasional lymphocyte infiltration, synovial proliferation and slight involvement of the Achilles' tendon. No difference was seen in the findings between ceftriaxone-treated and untreated mice. The results suggest that the presence of vegetative spirochetes is no prerequisite for persisting joint symptoms and elevated anti-borrelia IgG levels in these B. garinii-infected mice.

Matrix metalloproteinase-9 (gelatinase B) deficiency leads to increased severity of Staphylococcus aureus-triggered septic arthritis

Matrix metalloproteinases constitute a family of structurally related endopeptidases that are crucial for the normal turnover of the extracellular matrix. Elevated levels of MMP-9 have been demonstrated in synovial fluids of rheumatoid arthritis patients, and a correlation with the severity of the disease has been described. The aim of this study was to explore the impact of MMP-9 expression on joint inflammation and destruction in a model of bacterially induced septic arthritis. MMP-9 knock-out mice and C57Bl6 congenic controls were inoculated intravenously or intra-articularly with Staphylococcus aureus. Arthritis was evaluated clinically and by means of histology. Zymographic analyses were performed to study ex vivo induction of MMP-9 following exposure to S. aureus. The MMP-9 knock-out mice displayed a significantly higher frequency and severity, but not destructivity, of arthritis than did the wild-type mice. The knock-out mice also proved to harbour an increased number of bacteria locally in joints and systemically in kidneys, possibly by impaired extravasation and recruitment of leukocytes and a deficient early defence against infection. Our findings indicate that deficiency in MMP-9 increases the degree of joint inflammation due to decreased bacterial clearance.

Arthritis in adults with community-acquired bacterial meningitis: a prospective cohort study

BACKGROUND

Although the coexistence of bacterial meningitis and arthritis has been noted in several studies, it remains unclear how often both conditions occur simultaneously.

METHODS

We evaluated the presence of arthritis in a prospective nationwide cohort of 696 episodes of community-acquired bacterial meningitis, confirmed by culture of cerebrospinal fluid, which occurred in patients aged >16 years. The diagnosis of arthritis was based upon the judgment of the treating physician. To identify differences between groups Fisher exact statistics and the Mann-Whitney U test were used.

RESULTS

Arthritis was recorded in 48 of 696 (7%) episodes of community-acquired bacterial meningitis in adults. Joint-fluid aspirations were performed in 23 of 48 patients (48%) and joint-fluid cultures yielded bacteria in 6 of 23 patients (26%). Arthritis occurred most frequently in patients with meningococcal meningitis (12%). Of the 48 patients with bacterial meningitis and coexisting arthritis, four died (8%) and 10 (23%) had residual joint symptoms.

CONCLUSION

Arthritis is a common manifestation in patients with community-acquired bacterial meningitis. Functional outcome of arthritis in bacterial meningitis is generally good because meningococcal arthritis is usually immune-mediated, and pneumococcal arthritis is generally less deforming than staphylococcal arthritis. Nevertheless, additional therapeutic measures should be considered if clinical course is complicated by arthritis. In patients with infectious arthritis prolonged antibiotic therapy is mandatory.

Endogeneous sources of infection in transplant recipients

The mammal organisms carry on their surfaces and in their tissues cohorts of microorganisms of various nature. There is a balance of interests and profits between the host and microbial inhabitants. The bacteria and fungi behave like comensals, colonizers, dormants, however, under certain, mostly unknown, conditions may evoke reaction of the host. This process is damaging both for the host and microbes. Large surgical trauma and allograft itself, as well as, immunosuppression create favorable conditions for imbalance between inhabiting microorganism and the recipient. The host flora and that transplanted with the organ graft become activated. Active combating of the proliferating bacteria with antibiotics becomes necessary. Our knowledge of the bacterial flora of the so called "sterile" tissues remains rudimentary. There is still a great deal of prejudice on the sterility of deep tissues e.g. muscles, fat tissue, etc. This review cumulates pertinent literature data on the microorganisms-host interactions. Our own findings on colonization of arteries and adjacent tissues are discussed in the context of atherosclerosis and grafting.

Universal primers for detection of common bacterial pathogens causing prosthetic joint infection

The diagnosis of low grade prosthetic joint infection is difficult and time consuming. Nested-PCR for universal bacterial DNA segments detection of "orthopaedic" bacteria was tested in a laboratory setting. This method is based on amplification of the 16S bacterial ribosomal RNA coding sequences. 11 species of the most frequent bacterial pathogens (Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, Streptococcus agalactiae, Enterococcus faecium, Enterococcus faecalis, Klebsiella pneumoniae, Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, Serratia marcescens) involved in prosthetic joint infections were studied. All could be detected rapidly and sensitively by this method.

Temporal analysis of pathogenic events in virulent and avirulent Brucella melitensis infections

Despite progress in mouse models of brucellosis, much remains unknown regarding Brucella dissemination and tissue localization. Here, we report the dynamics of Brucella infection in individual mice using bioluminescent Brucella melitensis. Bioluminescent imaging of infected interferon regulatory factor-1 knockout (IRF-1(-/-)) mice identified acute infection in many tissues. Brucella was found to replicate in the salivary glands of IRF-1(-/-) and wild-type C57BL/6 mice suggesting a previously unknown tissue preference. Establishing a niche in this region may have relevance in humans where infection can result from ingestion of few bacteria. Sublethal infection of IRF-1(-/-) mice resulted in chronic Brucella localization in tail joints, an infection parallel to osteoarticular brucellosis in humans. Importantly, bioluminescent imaging rapidly identified attenuated EZ::TN/lux mutants in infected mice and revealed differences in dissemination, thereby defining the contribution of Brucella genes to virulence and tissue localization. Surprisingly, a virB mutant, though defective in persistence, disseminated similarly to virulent Brucella, suggesting bacterial spread is independent of VirB proteins that are important for intracellular survival. Together, our results reveal kinetics of acute and chronic Brucella infection in individual mice that parallels human infection as well as readily identified attenuated bacteria. Our approach facilitates identifying virulence determinants that may control tissue specific replication and may help develop therapeutics to overcome Brucella-induced chronic debilitating conditions.

Candida albicans Cell-Wall Fraction Exacerbates Collagen-Induced Arthritis in Mice

The immune system generates a specific response against most pathogens, while developing tolerance to self-antigens. Commensal micro-organisms can express molecular structures that mimic self-epitopes. During acute infection, such pathogen may activate self-reactive T-cell clones promoting autoimmunity. In the present study, a beta-mercaptoethanol cell-wall fraction (MF) from Candida albicans was injected into the paw of naive ICR and BALB/c mice and into the paw of ICR mice with bovine collagen type II-induced arthritis (CIA). Development of inflammation was monitored for 6 weeks. MF provoked a stable swelling and histopathologic changes in the injected joint, with a predominance of T-helper 1 cytokines in ICR mice. In BALB/c strain, a swelling was observed only in the early period, with no evidence of joint pathology. Injection of the MF fraction exacerbated the disease in ICR mice with CIA, and this was associated with the elevation of interferon-gamma and anti-bovine type II collagen (bCII) immunoglobulin G2a antibodies. These results indicate that component(s) in the MF fraction cross-react with bCII-specific cells.

Detection and identification of Mycobacterium tuberculosis in joint biopsy specimens by rpoB PCR cloning and sequencing

Osteoarticular tuberculosis (OAT) is an extrapulmonary tuberculosis and accounts for 1 to 3% of all tuberculosis cases. We used an rpoB PCR-plasmid TA cloning-sequencing method to detect and identify tubercle bacilli in surgical specimens from patients suspected of having OAT. By comparing the similarities of the rpoB sequences determined with those in GenBank, Mycobacterium tuberculosis was detected in 23 of 43 samples. Three of the 23 positive samples had mutations at codon 531, which are commonly observed in rifampin-resistant M. tuberculosis strains. Our results suggest that the rpoB PCR-TA cloning-sequencing method developed, which detects M. tuberculosis and which simultaneously determines its rifampin susceptibility, can also be used efficiently for the diagnosis of OAT.

Inflammation induced by inoculation of the joint with Candida albicans

In humans Candida albicans is the most frequently isolated opportunistic fungal pathogen. In immunocompromized host the balance with the commensal fungus easily turns to life-threatening disseminated infection. The asymptomatic Candida persistence in organs and the recurrent infections suggest continuous circulation of yeast cells and their degradation products. Under certain conditions, joints might become one of the infectious sites. More easily a reactivation and destructive process can be provoked in individuals with established arthritis. We have investigated the joint inflammation caused by inoculation of the paw with live C. albicans, in intact mice and mice with collagen-induced arthritis (CIA). The results demonstrate that C. albicans infection when localized into the joints caused rapidly progressing septic arthritis. The effect was associated with a strong swelling, a rapid influx of polymorphonuclear (PMN) cells, and an elevated secretion of TNF-alpha and IFN-gamma by lymph node cells. Joint infection exacerbated the established CIA which correlated with an increased level of anti-collagen antibodies.

Metalloproteinase-7 contributes to joint destruction in Staphylococcus aureus induced arthritis

Septic arthritis induced by Staphylococcus aureus causes a rapid destruction of joint cartilage and periarticular bone. The mechanisms behind this phenomenon are not fully understood. Earlier studies have shown that cytokines and metalloproteinases are of importance in bone metabolism. Matrix metalloproteinase-7 (MMP-7) has pleiotropic function including facilitating migration of both macrophages and neutrophils. The aim of this study has been to investigate the significance of MMP-7 expression in septic arthritis. MMP-7 deficient mice and congeneic controls were intravenously inoculated with an arthritogenic dose of S. aureus LS-1. This study shows that MMP-7 deficient mice exposed to S. aureus developed significantly less severe arthritis both clinically and histologically. Despite this finding, bacterial growth in the deficient animals was significantly increased. In vitro responses to staphylococcal antigens and superantigens did not differ between MMP-7(+/+) and MMP-7(-/-) mice with respect to cytokine production and if anything increased the production of certain chemokines. In addition MMP-7(-/-) mice exhibited decreased numbers of peripheral blood mononuclear cells before and one day after bacterial inoculation, but increased numbers of peripheral granulocytes on day 1. In conclusion, MMP-7 contributes to the development of a destructive course of septic arthritis despite decreased bacterial load. In addition, expression of MMP-7 is of importance for the distribution of peripheral leukocytes.

Protective niche for Borrelia burgdorferi to evade humoral immunity

The Lyme disease spirochete, Borrelia burgdorferi, is an extracellular microbe that causes persistent infection despite the development of strong immune responses against the bacterium. B. burgdorferi expresses several ligand-binding lipoproteins, including the decorin-binding proteins (Dbps) A and B, which may mediate attachment to decorin, a major component of the host extracellular matrix during murine infection. We show that B. burgdorferi was better protected in the joints and skin, two tissues with a higher decorin expression, than in the urinary bladder and heart, two tissues with a lower decorin expression, during chronic infection of wild-type mice. Targeted disruption of decorin alone completely abolished the protective niche in chronically infected decorin-deficient mice but did not affect the spirochete burden during early infection. The nature of protection appeared to be specific because the spirochetes with higher outer surface protein C expression were not protected while the protective niche seemed to favor the spirochetes with a higher dbpA expression during chronic infection. These data suggest that spirochetal DbpA may interact with host decorin during infection and such interactions could be a mechanism that B. burgdorferi uses to evade humoral immunity and establish chronic infection.

Comparison of disseminated and nondisseminated strains of Borrelia burgdorferi sensu stricto in mice naturally infected by tick bite

Clinical isolates of Borrelia burgdorferi sensu stricto have been categorized into disseminated and nondisseminated groups based on distinct ribosomal spacer restriction fragment length polymorphism genotypes (RSTs). In order to determine whether transmission by tick bite would alter the dissemination dynamics and disease produced by distinct genotypes, disseminated isolates (RST1), nondisseminated isolates (RST3), and a standard laboratory strain (B-31) were established in a murine cycle utilizing infections transmitted by ticks. B-31 spirochetes circulated in the blood of inbred C3H/HeJ mice longer than in the blood of outbred mice. The majority of C3H mice exposed to RST1-infected ticks contained cultivable spirochetes in their blood for up to 17 days; in contrast, mice exposed to RST3 isolates demonstrated a precipitous decline in infection after day 7 postexposure. A quantitative PCR (q-PCR) assay demonstrated that the densities of spirochetes in blood were similar for the RST1 and RST3 isolates, except during the 2nd week postexposure, when the RST1 isolates displayed a markedly higher density in blood. Spirochete load in the heart and bladder of infected mice was measured by q-PCR at 8 weeks postexposure; the numbers of spirochetes in these tissues were similar for mice infected with either disseminated or nondisseminated strains. Similarly, histopathology samples of heart, bladder, and joint tissue obtained at 8 weeks postexposure did not reveal greater pathology in mice infected with the disseminated isolates. We conclude that although the spirochetemia induced by tick-transmitted disseminated isolates was more intense and of longer duration than that induced by nondisseminated isolates, the resultant pathologies produced by these strains were ultimately similar.

Klebsiella pneumoniae septic arthritis in a cirrhotic patient with hepatocellular carcinoma

Despite septic arthritis is increasingly being reported in elderly patients with diabetes or alcoholism, reported cases of spontaneous bacterial arthritis in cirrhotic patients are extremely rare. We present the first reported case of K. pneumoniae septic arthritis and spontaneous bacterial peritonitis in a cirrhotic patient with hepatocellular carcinoma. K. pneumoniae, one of the most common causative organisms of spontaneous bacterial peritonitis in cirrhotic patients, was isolated from both the blood and the joint fluid, which suggests that the route of infection was hematogenous. After the treatment with cefotaxime and closed tube drainage, the condition of the patient was improved, and subsequently, the joint fluid became sterile and the blood cultures were proved negative. Therefore, this case provides further evidence for the mode of infection being bacteremia in cirrhotic patients and suggests that the enteric bacteremia in cirrhotics may cause infection in different organ systems.

Septicaemia and arthritis in pigs experimentally infected with Pasteurella multocida capsular serotype A

Twenty-five caesarean-derived, colostrum-deprived (CDCD) pigs and 18 specific pathogen-free pigs, aged 8 to 14 weeks, were inoculated intranasally or intratracheally with Pasteurella multocida capsular serotype A, isolated from a severe pneumonic lesion in a growing pig. The pigs were killed for necropsy on day 6 or 14 post-inoculation (PI) or, in the case of the only fatally infected animal, examined at the time of death. One CDCD pig, inoculated intratracheally with 5 ml of a bacterial suspension containing 1.7x10(9) colony-forming-units/ml, died of septicaemia on day 1 PI. Histological lesions such as severe pleuropneumonia, thrombi in glomerular capillaries, haemorrhage of the spleen, and abscesses in the tonsillar crypts were observed. The organism was recovered from a number of sites and its antigens were detected immunohistochemically in the pneumonic lesions, blood vessels of the tissues, and tonsillar crypts in the dead pig. Pneumonia, pleural adhesions and suppurative arthritis in the extremital joints were observed grossly in 3/29, 8/29 and 7/29 intratracheally inoculated pigs, respectively. In intranasally inoculated pigs, no macroscopical abnormalities were seen; histologically, however, exudative bronchopneumonia and fibrinous pleurisy were observed in 9/14 and 4/14 pigs, respectively. No significant changes were seen in the tissues of uninfected control pigs. The organism was recovered from the lesions and P. multocida type A antigen was demonstrated immunohistochemically. The organism was rarely recovered from the liver, spleen or lymph nodes (bronchopulmonary or mesenteric). The results suggest that P. multocida capsular serotype A alone can cause not only pneumonia in pigs but also septicaemia or arthritis.

Legionella pneumophila serogroup 4 isolated from joint tissue

We report the isolation of Legionella pneumophila serogroup 4 from synovial tissue obtained from an 80-year-old female with chronic swelling of her right metacarpophalangeal joint. Synovial tissue infections caused by L. pneumophila are rare. Interestingly, this isolate was recovered from chocolate agar after 5 days of incubation.

[A case of association of atypical localisations of Streptococcus pneumoniae]

Streptococcus pneumoniae can be responsible for spinal, joints, pulmonary or infrequently cutaneous septic localisations. The association between different septic localisation is extremely rare with this microorganism. We describe the first case of concomitant spinal, joints and cutaneous septic localisations in a critically ill patient with S. pneumoniae septicaemia. This observation illustrates that heterogeneity of clinical features depends on the pathogen characteristic and its interaction with the host.

Use of Polymerase Chain Reaction to Diagnose Tuberculous Arthritis From Joint Tissues and Synovial Fluid

Context.—Tuberculosis of the joints and bones is a significant worldwide problem, often leading to joint and bone destruction. The diagnosis of this disease manifestation is difficult.

Objective.—To assess the role of conventional diagnostics compared to polymerase chain reaction applied to samples obtained at arthroscopy.

Design.—This was an open observational study that was blinded to the microbiologist, histopathologist, and molecular biologist responsible for assessing the main outcome measures.

Patients.—Seven patients (8 samples) with joint and bone tuberculosis and 14 patients (16 samples) with nontuberculous joint and bone disease.

Intervention.—Arthroscopic examination and tissue sample collection.

Main Outcome Measures.—Mycobacterium tuberculosis staining, culture, and histopathologic assessment of caseating granulomas vs polymerase chain reaction.

Results.—Polymerase chain reaction was positive in all cases of true tuberculosis and falsely identified 2 samples as positive, both however, in patients who had lung tuberculosis in the past.

Conclusions.—Conventional bacteriological methods for demonstration of M tuberculosis are not very sensitive and can be time-consuming. Polymerase chain reaction of arthroscopically obtained joint tissue biopsies appears promising in the early diagnosis of tuberculous arthritis.

Borrelia burgdorferi population dynamics and prototype gene expression during infection of immunocompetent and immunodeficient mice

The population dynamics of Borrelia burgdorferi were quantified by real-time PCR targeting the flaB gene in skin (inoculation site, noninoculation site, and ear), heart (heart base and ventricle), quadriceps muscle, and the tibiotarsal joint at 1, 2, 4, 6, and 8 weeks after intradermal inoculation in C3H and C3H-scid mice. In addition, RNA transcription was assessed for several prototype genes, including flaB, ospA, ospC, dbpA, arp, vlsE, fbp, oppA-2, and p37-42. Spirochete numbers were equivalent in C3H and C3H-scid mice at 1 or 2 weeks and then declined in C3H mice, but they continued to rise and then plateaued in C3H-scid mice. Gene transcription was likewise higher in C3H-scid mice than in C3H mice, particularly at 4 or more weeks of infection. Gene transcription showed variation among tissues, with the highest levels of transcription in heart and joint tissue, which are sites of inflammation.

Effect of complement component C3 deficiency on experimental Lyme borreliosis in mice

Mice deficient in complement component C3 (C3(-/-)) and syngeneic C57BL/6 control mice were challenged with Borrelia burgdorferi to determine the role of complement in immune clearance and joint histopathology during experimental Lyme borreliosis. Tibiotarsal joint, ear, and heart tissues were monitored for spirochete numbers at 2, 4, 8, and 12 weeks postinoculation with 10(5) B. burgdorferi B31 clone 5A4 by using quantitative real-time PCR. The spirochete load in joint and ear tissue remained higher in the C3(-/-) mice than in the wild-type counterparts throughout the 12-week study, whereas the numbers in heart tissue of both groups of mice decreased substantially at 8 to 12 weeks postinfection. Histopathology scores for joint tissue were generally higher in the C3(-/-) mice compared to C57BL/6 controls at 2 and 4 weeks postinfection, which may reflect the presence of higher numbers of bacteria in the joints at these early time points. Levels of anti-B. burgdorferi immunoglobulin G tended to be reduced in the C3(-/-) mice compared to control mice. Furthermore, a 5.5-fold-lower number of the complement-sensitive Borrelia garinii was needed to infect C3(-/-) mice compared to C57BL/6 mice, indicating that its sensitivity to complement is one barrier to infection of the mouse model by B. garinii. These results indicate that the complement system may be important in controlling the early dissemination and progression of B. burgdorferi infection.

The role of Staphylococcus aureus sortase A and sortase B in murine arthritis

Gram-positive pathogenic bacteria display proteins on their surface that play important roles during infection. In Staphylococcus aureus, these surface proteins are anchored to the cell wall by two sortase enzymes, SrtA and SrtB, that recognize specific surface protein sorting signals. The role of sortase enzymes in bacterial virulence was examined using a murine septic arthritis model. Intravenous inoculation with any of the Delta(srtA), Delta(srtB) or Delta(srtAB) mutants resulted in significantly increased survival and significantly lower weight loss compared with the parental strain. Mice inoculated with the Delta(srtA) mutant did not express severe arthritis, while arthritis in mice inoculated with the Delta(srtB) mutant was not different from that seen in mice that were infected with the wild-type parent strain. Furthermore, persistence of staphylococci in kidneys and joints following intravenous inoculation of mice was more pronounced for wild-type and Delta(srtB) mutant strains than for Delta(srtA) or Delta(srtAB) variants. Together these results indicate that sortase B (srtB) plays a contributing role during the pathogenesis of staphylococcal infections, whereas sortase A (srtA) is an essential virulence factor for the establishment of septic arthritis.