Infections of bone and cartilage tissues, 27 infections (synovial fluid, DNA test - qualitative)

Joint infections, known as septic arthritis, are serious conditions that require prompt and accurate diagnosis to prevent irreversible damage to bone and cartilage tissue. PCR testing from synovial fluid is indicated in the following clinical situations to rapidly identify pathogens:

1. Suspicion of septic arthritis – Patients presenting with severe joint pain, swelling, erythema, and fever. Bacterial infections are most commonly caused by:
   • Staphylococcus aureus (including methicillin-resistant strains)
   • Streptococcus spp.
   • Escherichia coli or other enterobacteria, especially in immunocompromised patients.
2. Patients with joint prostheses – Periprosthetic infections are a serious complication of joint replacement surgeries. Identifying pathogenic bacteria such as:
   • Staphylococcus aureus,
   • Klebsiella pneumoniae,
   • Enterococcus faecalis and
   • Pseudomonas aeruginosa, can guide specific antibiotic therapy and prevent implant failure.
3. Reactive arthritis – Triggered by bacterial or fungal infections in other parts of the body, leading to an inflammatory response in the joints. Relevant pathogens include:
   • Chlamydia trachomatis,
   • Neisseria gonorrhoeae (in gonococcal arthritis),
   • Bacteroides fragilis.
4. Immunocompromised patients – Individuals with diabetes, cancer, or those undergoing immunosuppressive therapy are more susceptible to infections with opportunistic bacteria, including:
   • Candida spp. and
   • Clostridium perfringens, which may colonize the joints.
5. Osteomyelitis and soft tissue infections – If the infection spreads to bone or cartilage tissue, synovial fluid testing can identify relevant pathogens such as:
   • Proteus spp.,
   • Serratia marcescens,
   • Morganella morganii.

Advantages of PCR Testing:

• Rapid diagnosis – enables real-time identification of pathogens, allowing for timely treatment adjustment
• High sensitivity – detects even low levels of bacterial DNA, crucial in chronic or partially treated infections
• Multiplex identification – allows detection of multiple pathogens from a single synovial fluid sample, offering a comprehensive view of the infection
• Polymicrobial infections – PCR can detect multiple pathogens simultaneously, including anaerobes (e.g., Bacteroides fragilis, Anaerococcus prevotii), which are difficult to identify with traditional culture methods
• Antibiotic-resistant infections – specific pathogen identification helps clinicians adjust treatment appropriately, avoiding broad-spectrum antibiotics that may promote resistance (e.g., detection of MRSA guides appropriate therapy)
• Post-treatment monitoring – in severe or recurrent infections, PCR can be used to monitor treatment efficacy

Contraindications and Precautions:

Sample contamination – synovial fluid must be collected under aseptic conditions to avoid contamination from skin or environmental bacteria, which may lead to false-positive results.

Interference from prior treatment – in patients who have received empirical antibiotic therapy, PCR may not detect dead bacteria, potentially resulting in false-negative results. In such cases, bacterial culture may also be necessary for confirmation.

Interpretation of Results:

• Positive result – confirms the presence of specific bacterial DNA in synovial fluid and indicates the need for immediate antibiotic therapy
• Negative result – indicates the absence of detectable pathogens in the sample

PCR testing from synovial fluid is recommended for patients with symptoms of septic arthritis or those at increased risk of joint infections, such as immunocompromised individuals or patients with joint prostheses. Rapid and accurate pathogen identification can improve treatment outcomes and help prevent serious complications.