Microbiological Investigation of Osteo-articular infections
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Microbiological Investigation of Osteo-articular infections



Microbiological Investigation of Osteo-articular infections

Microbiological Investigation of Osteo-articular infections



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Microbiological Investigation of Osteo-articular infections Microbiological Investigation of Osteo-articular infections Presentation Transcript

  • Microbiological Investigations of thejoint and spine infectionsDr. Mahen Kothalawala MBBS, Dip in Microbiology, MD, MPH(NZ)Consultant Clinical MicrobiologistTeaching Hospital Kandy
  • • Diagnostic aspect of of SA• TB arthritis and TB spine• PCR based molecular assays in findingaetiology of osteo- artricular infections
  • A. Diagnosis of SA
  • Diagnosis of SA• SA- Separate entity• Purulent invasion of a joint/joints by infectious agent– Heamatogenous or Post surgical/traumatic• Only type of arthritis amenable to treatment withAntibiotics• Failure to prompt early aggressive therapy → lead to– joint destruction– septicemia/death
  • Diagnosis of SA - challenging• Clinical signs and symptoms → poor sensitivityand specificity• Children – usually present with classical symptoms&signs• Adults/Pts with existing joint disorders - symptoms&signs• Lab based test-very essential
  • Diagnosis of SA – challenging….• Made on Clinical Suspicion and confirmedwith laboratory tests• Two types of tests are employed1. Synovial Fluid Analysis2. Routine blood tests/ tests for Inflammatorymarkers
  • 1. Synovial Fluid Analysis• If properly performed provide valuableinformation to evaluate for Joint Disorders andguide treatment
  • Specimen collection and transportation• Specimen – Joint Fluid• Container –– Sterile Tube with Anti-coagulant (Clot interfere withcounts)– Blood Culture Bottle• Contact lab and request for early report
  • Specimen collection and transportation cont..• Immediately dispatch for processing and culturing.• Directly inoculating in to culture bottles, ↑ sensitivity ofdetecting organisms– Meticulous sterile technique is required to ↓ False Positives• In clinical suspicion of SA, culture of synovial membrane ↑isolation rates• Concurrent specimens for Ix,– Sputum,– urine, and– blood cultures required
  • Joint Fluid Analysis….. chemical analysisComponent inJt fluidNormal Value Septic Episode likely with CommentGlucose 80% of that ofPlasma(Average of 10mg/dllower than plasma)< 40mgGreater than 20mg/dL dropsuggestive of infectionLikely-hood of SA ishigher with lowervaluesProtein Usually within 25%of the Plasmaglucose1 to 3g/dL> 3g/dL in SAHigh protein levels seen in•anky spond,•SA,•Gout,•Reiters,•Psoriatic ArthropathyAll types of plasmaproteins present in JtfluidLactatedehydrogenase>333 IU/L or >10mg/L May increase inRheumatoid Arthritis,Infectious Arthritisand in Gout
  • WBC BreakpointsCut off level Differential InterpretationUp to 150/ml Mostly Mono nuclear Normal Cell Count< 2000 /ml Unlikely to be of inflammatory origin> 2000 /ml Likely to be inflammatory< 5000 /ml with RBCS influidLikely to be following traumatic5000 to 15,000/ml <25% are PMN Toxic Synovitis10000- to 15000/ml Nearly 50% are PMN Acute Rheumatic Fever/ Early SA/ GC> 50,000 /ml Nearly 75% PMN Likely to be septic arthritis> 100,000 /l > 90% Septic Arthritis LikelyLow total count with>90% DCgout, pseudogout, acute rheumaticfever, Reiters disease, andRA
  • Gram Stain and Culture• Gram stains → Confirms septic arthritis.• Helps to initiate therapy on empiric basis (Before ASTavailable)• Sensitivity → from 29% to 50%– Gram positive pathogens 50 to 75%– Sensitivity for Gram Negative organisms –less– Sensitivity for GC- <30%• Specificity 100%• Sensitivity of Culture – 82% - Higher for NON GC septicarthritis
  • 2. Blood analysis• Blood culture (Sensitivity 50%)• Inflammatory markers (Supports ∆ of SA)– CRP,– Pro-calcitonin• ESR and Full count
  • Detection of Septic insults to human body –Which inflammatory marker is better?False Positives21/04/2013Receiver observer characteristicsTrue positives
  • 21/04/2013
  • Joint WBC count(area under thecurve (AUC) 0.75, 95% confidenceinterval (CI) 0.58 to 0.92),ESRWBC(AUC 0.69, 95% CI 0.57 to0.80)
  • Causative organisms of SA• Virtually all bacterial organism has beenreported• Type of Organism largely dependent on hostfactors• Role of exotic organisms- Atypical Mycos,Fungi emerged due to immuno-supressionand prosthetic implants
  • Organism RemarksStaphylococcus aureus most frequent organism in all ages and risk groups except > 2yearsIncidence of MRSA on the rise - >25% of cases are due to MRSA37%-56%of AllStreptooccus sp Streptococcus pyogenes most common, usually after a trauma, procedureor Secondary to chronic skin conditionGroup B – specially in elderly with chronic diseases such as DM,Cirrhosis,CRF etcGroup C and Pneumococci- Less frequentGram Negatives Rods Escherichia coli, Proteus mirabilis, Klebsiella and Enterobacter - RareMainly in very young and in elderly with co-morbid factorsat least20%Anerobes a history of diabetes, joint prosthesis implantation or followingpenetrating traumaRarecausesHIV associated- SA, S pneumonia, Mycoand fungal spAre common causes, But difficult to diagnoseGram Negative Cocci androdsN. gonorrhoeae and N. Meningitidis H. influenzae is uncommon in theadult population, commonest <2yrs20%Causative organisms of SA- Adult SA
  • Causative organisms-pediatric age groupAge 5 years to 12yearsMajor Pathogen MSSAand MRSAAs in adultsAge 2 months to 5yearsmethicillin-sensitive S.aureus and MRSAMajor cause of septic arthritisStreptococcuspneumoniaSignificant reduction of SA due to Strep notedrecently due to vaccination, but considerablenumber of cases may be due to Strep. Pneumotypes which were not covered by vaccinationHaemophilusinfluenzaeKingella Kingaein children between the ages of 2 months and5 years major cause of gram negative organismis K.kingi, may be due to HIB vaccinationInfants <2 months age S. aureus, Still major pathogen is Staph. aureusS. agalactiae andgram-negative entericbacteria.
  • Synovial Fluid• Request for - Three “C”s– Cell count– Crystals &– Culture• Gram Stain
  • Infections of the spine• History and Examination• Imaging for evidence of infection at site and imagingfor possible primary site (Infective endocarditis etc)• Specimens-– Blood– Needle aspiration– Bone biopsy– IV Disc Biopsy
  • B. Diagnosis of TB arthritis and TB spine
  • B. TB arthritis and TB spine• infect the musculoskeletal system(3% cases)Commonest area – Spine• Patho-physiology– Hematogenous dissemination to long bones, spine– Direct spread to bone → adjacent tuberculouslymphadenitis• Forms- caseating granulomatous inflammationwith bone necrosis - PATHLOGIC HALLMARK
  • Diagnosis of TB arthritis• TB SA and spine are pauci-bacillary, Smears for(AFB often negative) Typically, 104 – 106 organisms/mlnecessary for AFB positivity• Classical constitutional symptoms rare finding• Tuberculin skin testing (TST) and interferon-gamma release assays (IGRA) are adjunctivediagnostic tools.
  • Diagnosis• Blood tests – ESR (usually >100mm/hr,WBC/DC usually lymphocytes• Sputum and urine for AFB to excludeconcurrent involvement of other sites (50% ofcases Positive)• Synovial fluid culture for TB →gold standardtest
  • Synovial Biopsy for AFB and culture• If performed correctly→ Higher yield for AFB(TB prefers synovium)• Culture – Gold standard- take up to 8/52• Synovial Fluid PCR –Rapid results
  • TB arthritis• 70% percent to 90% of patients may have apositive TST.• Similar numbers – Quantiferone gold +• 50% have abnormalities on chest x-rayconsistent with TB
  • Establishment of Diagnosis of TB arthritis• A high level of suspicion required with riskfactor identification• Specimens for microbiology and histology.• Gold Standard – by culture demonstration &AST.– Delay of up to 8 to 10 weeks– Delays in diagnosis and initiation of therapy areassociated with increased mortality.
  • Role of Synovial Biopsy• Specimen of choice to diagnose TB arthritis.• Biopsy may yield culture positive in 90% to95%-can be performed if the diagnosis of TB arthritis remains inquestion• Synovial fluid AFB smear is positive in <20%but culture may be positive in up to 80%.
  • Diagnosis of TB arthritis using Adenosine Deaminaselevels in serum and synovial fluid• ADA – Level reflects ↑ activity of monocyteand lymphocyte stimulation• Which occur in TB arthritis, Theoretically ADAshould increase in TB A
  • Serum ADA Levels• ADA levels high → in inflammatory arthritis• Can differentiate inflammatory from noninflammatory arthritis• High serum ADA reported in– RA,– crystal-induced arthritis– septic arthritis
  • Synovial fluid ADA level• High in all inflammatory arthritis• But not as high as in TB arthritis (Zamani et al, 2010)
  • A synovial fluid ADA level of 31 U/l gave a sensitivity of 83.3% (95%CI 3599.6) and a specificity of 96.7% (95%CI 82.8-99.9) with a Kappa of agreemof 0.8 (p<0.001).
  • ADA in TB arthritis• With reference to the gold standard test,– Sensitivity> 95% &– specificity > 80%,• Synovial ADA might be an alternative tool forthe early diagnosis of TB arthritis
  • • C. PCR based Molecular assays in findingaetiology of osteo- artricular diseases
  • PCR• Multiplication of genetic material using seriesof steps and detecting them subsequently• Has very high sensitivity• Chances of Contamination is high- need tofollow strict protocols• Two method– Conventional and Real time
  • PCR based tests• IS useful in many fastidious, slow-growing oruncultured bacteria,• used when an empirical antibiotic treatmenthas already been initiated.• Two steps –– Broad Base Primer to identify Bacterial etiology– Specific primer- to identify specific pathogens
  • RT-PCR• RT-PCR easier to interpret and allowed todetect fours time more cases thanconventional PCR.
  • Specimens for PCR• All specimens prior to commencement oftherapy – Can use– Biopsy specimens– Synovial biopsies– Fine needle aspirates under guidanceContainers- Plain bottles, If anticoagulant necessaryuse only heparinContact the service provider to obtain containers
  • Molecular diagnostic methods for TBarthritis• HSP 65 – 65 kDa gene which is highlyconserved and specific for Mycobacteriae• Advantage of PCR based tests– Prevent mis-identification as in phenotypicanalysis– Early rapid diagnosis– Not subject to false negative results– Identification of unusual organisms
  • • Thank you