Microbiology

Tissues and Fluids

Fluids from normally sterile sites

These include joint, bursa, pericardial, peritoneal, pleural and amniotic fluids.

A minimum volume of 1ml should be collected by aseptic technique and placed in a dry sterile white cap universal container and transported to the laboratory as soon as possible. If for some reason a long delay (>8hrs) is anticipated the specimen should be refrigerated and NOT put in an incubator.

Peritoneal dialysis fluid

Withdraw the fluid aseptically from the injection port of the dialysate bag using a sterile needle and syringe. Send 30ml in a sterile white capped container and a blood culture set consisting of an aerobic FAN and anaerobic bottle each of which has been inoculated with 10ml of dialysis fluid. Out of hours the blood culture bottles should be put in the incubator. The fluid must NOT be put in the incubator.

Ascitic fluid

A cell count will only be performed if the patient has a diagnosis of spontaneous bacterial peritonitis (SBP) or is specifically discussed with a Consultant Microbiologist prior to specimen receipt. Relevant clinical details are essential to ensure appropriate investigation is undertaken.

Pus and exudates

Specimens of pus and exudates are always preferable to swabs. Collect the pus into a dry sterile white screw cap 60ml bottle using a sterile syringe, or, only if this is not possible, take a swab. Please ensure the site of infection is clearly and accurately recorded on the request.

Serous fluids

Send samples in sterile bottles for culture and microscopy. If culture for M. tuberculosis is required, a large volume of fluid should be sent in a bottle containing citrate.

Tissue

Pieces of tissue for microscopy and culture should be sent in a dry sterile container with a description of the site and clinical details. Where several pieces of tissue are taken they should be put in separate sterile containers. Under no circumstances should the tissue for culture be put in formalin.

Tissue may be sent for 16S r DNA PCR after discussion with a Consultant Microbiologist. This is a highly specialised test and the indications for its use are limited. This specimen needs to be placed in a separate sterile container to prevent contamination.

Prosthetic joint infection specimens

Multiple specimens (optimum number 5-6 specimens if more are taken they will not be tested) taken in theatre using separate instruments should be placed in individual sterile container and clearly labelled.