Culture Aerobic (Body Fluid) Test

Aerobic culture is nothing but the culture of body fluids for the detection of aerobic bacteria present in the body causing some illness. It is difficult to detect the bacteria directly in the body as they are less in number relative to the volume of the body fluid. Therefore they are cultured so that they increase in number which makes it easy to detect them. These cultures are performed on specialised media which provide the nutrients necessary for the bacteria to grow. Different culture media used include blood agar, chocolate agar, cooked meat broth, etc. Different nutrients are added to these culture media based on the requirement of the bacteria which is to be cultured. Few culture media are specific for certain bacterial species and this makes it easy for their growth and detection.

Initially, the patient should be explained about the procedure of collection of the fluid to be cultured. All the clothing should be removed from the area from where the fluid is to be removed. The patient should be instructed to cooperate as aspiration of the fluid will cause slight pain. No diet or fluid restriction is recommended for the collection of fluid. The culture media which are inoculated with the aspirated fluid should be handled with extreme care as they highly contagious as they contain bacteria. Therefore spread of bacteria through these media is really very easy.

Aerobic culture of body fluids is useful for the isolation and identification of the pathogenic micro-organisms present in the body fluids. The pattern of growth, color at the growth area will represent the type of bacteria growing. TCBS agar medium is used to selectively isolate vibrio cholera. Salmonella typhi is recovered from wilson and blair’s agar. Staph aureus is recovered from mannitol salt agar. MacConkey agar is used for the growth of enterobacteriaceae. LJ medium is used for the growth of mycobacterium tuberculosis.

Usually, 5-10 ml of the fluid is aspirated using a syringe for the purpose of culture. Fluids such as peritoneal fluid, synovial, bile, pericardial, etc are used. A cotton pad dipped in alcohol or spirit is used to clean the area from where the fluid is to be aspirated. A wide bore needle is pierced through the skin and the fluid is aspirated. This fluid is inoculated into the cultured media. These media are then sent to research laboratories where they are incubated and observed for growth of the organisms.