Alpha Defensin and 16S rRNA Gene in Diagnosis of PJI
Alpha Defensin and 16S rRNA Gene in Diagnosis of PJI
Total joint replacement is considered one of the most successful surgical procedures in the
 field of orthopedics. Despite this achievement, prosthetic joint infections is still
 considered a severe complication often leading to catastrophic results and requiring repeated
 and extensive treatment.

 The incidence of PJI (a prosthetic joint infection) varies depending on the joint involved;
 the rate of arthroplasties becoming infected is as follows: 1.7% of primary and 3.2%of
 non-primary hip arthroplasties.

 The accurate diagnosis of prosthetic joint infection often involves the combination of
 multiple factors including symptoms, signs, synovial fluid cell count, serum inflammatory
 markers, and culture.

 The sensitivity of synovial fluid culture is only 85%, so a negative culture does not rule
 out infection. However, the specificity of synovial fluid culture is approximately 95%, and
 positive cultures often imply the presence of prosthetic joint infection.

 The synovial fluid alpha-defensin test is an immunoassay that was specifically developed to
 aid in the diagnosis of prosthetic joint infection .

 The sensitivity and the specificity of the alpha-defensin immunoassay test have been reported
 to be above 96%.

 Molecular diagnostic tests using polymerase chain reaction (PCR) are emerging as a tool for
 the diagnosis of infections and noninfectious conditions. The application of PCR techniques
 with primers derived from the highly conserved regions of the bacterial 16S rRNA gene has
 been useful in the detection of bacterial organisms.

 Use of broad-range 16S rRNA gene PCR as a tool for identification of bacteria is possible
 because the 16S rRNA gene is present in all bacteria .

 Aim of the work:

 .Determine sensitivity and specificity of alpha defensing and 16S rRNA gene in diagnosis of
 prosthetic joint infection.

 -  Detection of antibiotic sensitivity for different organisms isolated from synovial fluid
Total joint replacement is considered one of the most successful surgical procedures in the
 field of orthopedics, alleviating pain and limitation of movement due to degenerative or
 traumatic joint damage. Despite this achievement, prosthetic joint infections is still
 considered a severe complication often leading to catastrophic results and requiring repeated
 and extensive treatment .

 Infection is a major problem in orthopedics leading to implant failure. It is a challenging
 task to treat orthopedic implant infections that may lead to implant replacement and, in
 severe cases, may result in amputation and mortality Sources of infectious bacteria include
 the environment of the operating room, surgical equipment, clothing worn by medical and
 paramedical staff, resident bacteria on the patient's skin and bacteria already residing in
 the patient's body Implant-associated infections are the result of bacteria adhesion to an
 implant surface and subsequent biofilm formation at the implantation site .

 Staphylococci account for more than 50% of total prosthetic joint infections. Approximately
 20% may be polymicrobial, 15% caused by gram-negative, and about 10% are culture negative .

 The incidence of PJI (a prosthetic joint infection) varies depending on the joint involved;
 the rate of arthroplasties becoming infected is as follows: 1.7% of primary and3.2%of
 non-primary hip arthroplasties .

 A correct and early appropriate therapy if correct and timely microbiological diagnosis of
 infections is done within 4 weeks, it could be possible to follow a conservative approach on
 the prosthesis, since microorganisms are not yet organized in biofilms. A delayed diagnosis
 (>4 weeks) of early and late infections involves the necessity of prosthesis removal due to
 the production of a structured and mature microbial biofilm . The definition of PJI was
 recently revised by the International Consensus Group on Periprosthetic Joint Infection

 According to PJI Consensus Group, patients should be considered to have a PJI if they meet
 one of the major criteria or at least three of the minor criteria:

 Major criteria are as follows:

 1. Two positive periprosthetic cultures with phenotypically identical organisms.

 2. A sinus tract communicating with the joint.

 Minor criteria are as follows:

 1. Elevated serum C reactive protein and erythrocyte sedimentation rate.

 2. Elevated synovial fluid white blood cell (WBC) count or ++ change on leukocyte esterase
 test strip.

 3. Elevated synovial fluid polymorph nuclear neutrophil percentage.

 4. positive histological analysis of periprosthetic tissue.

 5. A single positive culture .

 Risk factors:

 Different pathologies can increase the risk of prosthesis infections: previous infections,
 obesity, diabetes mellitus, immunodeficiency, and malnutrition or drugs therapy. The clinical
 assessment provides more details for the suspicion of infection. During physical examination,
 the surgeon can find the typical inflammation signs as swelling, redness, pain and loss of
 function .

 the most frequent sign was loss of function (95%), followed by pain (85%) and swelling
 furthermore only 22% of patients presented fever and 14% had feeling of illness but 19% had
 fistula as primary sign of infection .

 Diagnosis:

 The accurate diagnosis of prosthetic joint infection often involves the combination of
 multiple factors including symptoms, signs, synovial fluid cell count, serum inflammatory
 markers, and culture .

 A culture is an important tool for the diagnosis of prosthetic joint infection. Aspirated
 joint fluid culture should be sent in multiple sets of culture media.

 The sensitivity of synovial fluid culture is only 85%, so a negative culture does not rule
 out infection. However, the specificity of synovial fluid culture is approximately 95%, and
 positive cultures often imply the presence of prosthetic joint infection .

 Numerous preoperative tests for determination and diagnosis of a failed total hip replacement
 are available. These tests include hematological screening tests (measurement of the
 erythrocyte sedimentation rate, and the level of C-reactive protein, white blood-cell
 count,), aspiration of the hip joint, plain radiography, and radionuclide imaging studies.
 None of these tests is 100 % reliable and are subject to a variable spectrum of false
 negative or false positive results. A misdiagnosis has crucial consequences for the treatment
 and for the patient. In case of a misdiagnosed periprosthetic infection, revision of the
 prosthesis without appropriate debridement would keep a failed total hip replacement and risk
 an early failure. On the other hand a wrong assumption about periprosthetic infection caused
 by a false positive test, the patient has to undergo surgery which would be highly inadequate
 as a girdle stone operation or a cemented revision .

 The diagnosis of PJI is based on the clinical findings of arthritis, an abnormal synovial
 fluid (SF) analysis, and microbiologic confirmation with a positive SF gram stain or culture
 There are limitations to cultures which may include the following: a delay of at least 2 days
 from the time of submission for the recovery of the pathogen on the culture medium, the
 results can be affected by a small inoculum, fastidious organisms may require specialized
 microbiologic testing, and prior antibiotics may render the culture negative Thus, there is a
 need for a rapid, sensitive, and specific method in the diagnosis of PJI.

 The synovial fluid alpha-defensin test is an immunoassay that was specifically developed to
 aid in the diagnosis of prosthetic joint infection PJI .

 The simplicity of the alpha-defensin test, combined with its ability to provide a clinical
 result soon after a preoperative joint aspiration, makes it an attractive tool for diagnosing
 PJI The alpha-defensin protein is an antimicrobial peptide that is naturally released by
 neutrophils responding to a pathogen in the synovial fluid. It is therefore very reasonable
 to question whether this antimicrobial peptide is released in response to all pathogens and
 also whether the alpha-defensin test can detect PJIs caused by all organisms .

 The sensitivity and the specificity of the alpha-defensin immunoassay test have been reported
 to be above 96% .

 Use of broad-range 16S rRNA gene PCR as a tool for identification of bacteria is possible
 because the 16S rRNA gene is present in all bacteria. The 16S rRNA gene consists of highly
 conserved nucleotide sequences, interspersed with variable regions that are genus- or
 species-specific.

 Molecular diagnostic tests using polymerase chain reaction (PCR) are emerging as a tool for
 the diagnosis of infections and noninfectious conditions. The application of PCR techniques
 with primers derived from the highly conserved regions of the bacterial 16S rRNA gene has
 been useful in the detection of bacterial organisms.
Inclusion Criteria:

 - The study will include all patient with prosthetic joint suspected to be infected through
 clinical manifestation (fever, pain, fistula redness, swelling ,hotness and loss of
 function) associated with radiological evidence.

 Exclusion Criteria:

 -  Any patient began antibiotic treatment will be excludes from the samples.