Transcript culture
Indications • Mainly in Suspected cases of meningitis. See video Aim of the test • Diagnosis of the bacteria or fungal meningitis by microscopic examination and culture with identification and susceptibility test of the isolated organism. commensals Specimen collection • Explain procedure to the patient and obtain written consent. • See video 4 • Quantity of specimen 3 ml of CSF is sufficient for culture. • Time relapse before processing the sample CSF is an emergency specimen and should be processed immediately. • Storage: Room temperature •The sample is submitted in 3 tubes: chemistry, microscopic, culture sensitivity. Specimen processing • Media • • • • Two Blood Agar Chocolate Agar MacConkey Agar Fluid Thioglycollate Culturing procedure • As a general rule in CSF and body fluid specimens for culture • Centrifuge clear specimen and inoculate plates and do staining from sediments. • Turbid specimens may not be centrifuged. Result reporting • Results of the microscopy and all positive cultures of CSF are reported immediately to the treating physician. • Negative bacterial results are sent out 72 hours after the CSF is received. • Examine all plates and broth medium for growth after 24 hrs. • If no visible growth reincubate. • Check all plate daily and discard after 7 days especially if gram stain was + • Generally +ve culture indicate pathogens Turn around time • Gram stain result is reported within 30 minutes of specimen receipt • Positive Culture results = 3- 5 days • Negative Culture results = 2-3 day Additional information • Several antigen detection methods are available for capsular antigen of H. influenzae, N. meningitidis, S. pneumoniae and Group B streptococci in CSF which showed specificity and sensitivity of about 90-97%. • The routine culture for CSF does not include all organisms mentioned in the above table. • Finding bacteria does not necessarily mean the infection is contagious, unless it is meningococcal meningitis • Viral we test mainly: HSV and Enterovirus • Fungal we test for Candida and Cryptococcus. Body Fluid Culture • This means • Culture of Body Fluid such as peritoneal, pericardial, plural, ascitic, synovial. • Aim of the test • Isolate and identify pathogenic organisms from normally sterile body fluids and perform sensitivity test. • Types of specimen • Aseptically aspirated body fluid (e.g., synovial, peritoneal fluid, pericardial fluid, and pleural fluid ). Patient preparing • Explain procedure to the patient and obtain written consent. • Swab skin over the site of puncture with 2% tincture of iodine in concentric circles. • Iodine should remain in contact with skin for at least 1 minute prior to puncture to ensure complete antisepsis. • Before puncture, 70% alcohol is used to remove iodine from skin. Specimen collection • Contamination with normal microbiota from skin, rectum, vaginal tract, or other body surfaces should be avoided. • Indicate the specific source and pertinent clinical history on the request form. See video • Quantity of specimen: 1-5 mL is adequate. • Time relapse before processing the sample • Body fluids should be treated as CSF specimens and should processed immediately. • Storage • Maintain specimen at room temperature. Do not refrigerate. • Media • • • • Blood Agar (2 plates) Chocolate Agar, MacConkey Agar Thioglycollate broth Specimen processing Result reporting • Report Gram stain finding as an initial report. • Report the isolated pathogen and its sensitivity pattern as a final report. • Turn around time: • Gram stain and wet mount results should be available 1 hour after specimen receipt. • Isolation of a possible pathogen can be expected after 2-3 days. • Negative culture will be reported out 1-2 days after the receipt of the specimen.