Bacterial arthritis in a Swedish health district

Exploring the role of bacterial virulence factors and host elements in septic arthritis: insights from animal models for innovative therapies

Septic arthritis, characterized as one of the most aggressive joint diseases, is primarily attributed to Staphylococcus aureus (S. aureus) and often results from hematogenous dissemination. Even with prompt treatment, septic arthritis frequently inflicts irreversible joint damage, leading to sustained joint dysfunction in a significant proportion of patients. Despite the unsatisfactory outcomes, current therapeutic approaches for septic arthritis have remained stagnant for decades. In the clinical context, devising innovative strategies to mitigate joint damage necessitates a profound comprehension of the pivotal disease mechanisms. This entails unraveling how bacterial virulence factors interact with host elements to facilitate bacterial invasion into the joint and identifying the principal drivers of joint damage. Leveraging animal models of septic arthritis emerges as a potent tool to achieve these objectives. This review provides a comprehensive overview of the historical evolution and recent advancements in septic arthritis models. Additionally, we address practical considerations regarding experimental protocols. Furthermore, we delve into the utility of these animal models, such as their contribution to the discovery of novel bacterial virulence factors and host elements that play pivotal roles in the initiation and progression of septic arthritis. Finally, we summarize the latest developments in novel therapeutic strategies against septic arthritis, leveraging insights gained from these unique animal models.

The epidemiology of and risk factors for invasive Staphylococcus aureus infections in western Sweden

We conducted a prospective study of all cases of invasive Staphylococcus aureus infections (ISA) in the catchment area of Skaraborg Hospital (population 255,109) in western Sweden from March 2003 to February 2005. The annual incidence was 33.9 cases/100,000 population. Of these, 49% were classified as community-acquired, 32% as nosocomial and 19% as health care-associated. The mean age was 65 y. We registered children (age < or = 18 y) in 13 episodes. The most common predisposing illnesses/conditions were persons undergoing haemodialysis (relative risk 291), peritoneal dialysis (relative risk 204), persons with rheumatoid arthritis (relative risk 9), diabetes mellitus (relative risk 8), and cancer (relative risk 7). The patients were treated at various departments; only 18% of the episodes were primarily cared for at a department of infectious diseases. The most common diagnosis was soft tissue infection (27% of the episodes), bacteraemia without focus (19%), arthritis (15%), and line-associated infection (14%). A total of 197 invasive isolates was obtained, the vast majority from blood, in 141 of 170 episodes. We documented the wide spectrum of signs and symptoms. One- quarter of the patients had no history of fever, and one-third of the bacteraemia patients had normal white blood cell count (<10 x 10(9)/l) at presentation. All cases were of MSSA (methicillin-sensitive Staphylococcus aureus).

Hematogenous infection of a total knee arthroplasty with Klebsiella pneumoniae in association with occult adenocarcinoma of the cecum

Acute hematogenous septic arthritis caused by the genus Klebsiella is extremely rare. This case report describes a prosthetic joint infected with Klebsiella pneumoniae via acute hematogenous spread. This is the first reported case of K pneumoniae pyogenic arthritis with a coexisting occult colonic adenocarcinoma. The patient was treated successfully with open irrigation, debridement, polyethylene spacer exchange, and chronic suppressive antibiotics. The underlying colon cancer was recognized early, and the patient responded well to surgery and adjuvant chemotherapy. This case illustrates the importance of having a high index of suspicion for underlying pathologic processes when an unusual organism presents as the cause of septic arthritis.

Diagnostic utility of laboratory tests in septic arthritis

BACKGROUND

Septic arthritis remains a challenging diagnosis in which the doctor often relies on laboratory tests.

OBJECTIVE

To examine the diagnostic utility of three ancillary tests--namely, white blood cells (WBC), erythrocyte sedimentation rate (ESR) and the WBC in the joint fluid (jWBC)--using likelihood ratios (LRs) and receiver operating characteristic (ROC) curves.

METHODS

This was a retrospective cohort study at the Jacobi Medical Center. Medical charts of patients who had undergone arthrocentesis were included. Patients who had "dry taps" were excluded from the study. Patients were considered to have septic arthritis if they had a positive arthrocentesis culture or operative findings. The primary outcomes of this study were the sensitivities, specificities, LR(+) and LR(-) values of the laboratory tests for septic arthritis. The performance characteristics of the laboratory tests were analysed using ROC curves.

RESULTS

156 patients were enrolled, 16 (10%) had septic arthritis. The sensitivities for WBC, ESR and jWBC were 0.75, 0.75 and 0.50, and the specificities were 0.55, 0.11 and 0.88, respectively. The LR(+) values were 1.7, 0.84 and 4.0, and the LR(-) values were 0.46, 2.4 and 0.57, respectively. In ROC curve analysis, jWBC was the best test (area under the curve (AUC) 0.75, 95% confidence interval (CI) 0.58 to 0.92), followed by WBC (AUC 0.69, 95% CI 0.57 to 0.80) and ESR (AUC 0.55, 95% CI 0.37 to 0.74). A cut-off of jWBC = 17 500 maximised sensitivity and specificity on the ROC curve.

CONCLUSIONS

jWBC was the best diagnostic test for septic arthritis, WBC and ESR were poor tests. However, no test was diagnostic, and the clinician must be careful with patients with a potential septic joint.

Laboratory tests in adults with monoarticular arthritis: can they rule out a septic joint?

It is difficult to differentiate septic arthritis from other causes of monoarticular arthritis solely with a history and physical examination. The clinician must rely on ancillary tests to make a diagnosis, such as the white blood cell count of peripheral blood (WBC), the erythrocyte sedimentation rate (ESR), and the white blood cell count of the joint fluid (jWBC) obtained from arthrocentesis. Although it is known that septic arthritis is associated with abnormalities in these tests, the majority of the data are based on studies in the pediatric population. In addition, although several emergency medicine texts indicate that a jWBC greater than 50,000 cells/mm(3) is "positive," it is known that septic arthritis can occur in patients with low jWBCs.

OBJECTIVES

To determine whether specific ancillary tests have sufficiently high sensitivities to rule out septic arthritis in adults.

METHODS

This was a retrospective consecutive case series of patients from an urban emergency department (ED). Patients at least 18 years old who had septic arthritis confirmed by positive arthrocentesis culture or operative findings were included in the study. WBC greater than 11,000 cells/mm(3), ESR greater than 30 mm/hr, and jWBC greater than 50,000 cells/mm(3) were considered elevated.

RESULTS

Seventy-three patients met the inclusion criteria. The sensitivities of an elevated WBC, ESR, or jWBC in adults who had septic arthritis were 48%, 96%, and 64%, respectively. There were broad ranges of WBC, ESR, or jWBC among the patients. More than one third of adult patients with septic arthritis had jWBCs less than 50,000 cells/mm(3). All patients had an abnormality in at least one of these tests.

CONCLUSIONS

The WBC, ESR, and jWBC are extremely variable in adults with septic arthritis. Laboratory tests do not rule out septic arthritis with accuracy.