Synovial fluid is a viscous fluid found in cavities of synovial joints. Its role is to reduce friction between cartilage during movement. Synovial fluid may be collected via arthrocentesis, where a syringe is used to aspirate fluid from the joint capsule. Aspirated fluid is analyzed in a microbiology lab to diagnose infections like septic arthritis. Bacteria can enter joints through various routes and cause rapid cartilage damage and pain. Common bacteria that may be found in synovial fluid include Staphylococcus aureus and Streptococcus pneumoniae.

1. Synovial fluid
synovial fluid, is a viscous, fluid found in the cavities of synovial joints.
With its egg white–like consistency, the principal role of synovial fluid is
to reduce friction between the articular cartilage of synovial joints
during movement.

2.  Bacterial joint inflammation is a serious and painful infection in a joint. It’s
also known as bacterial or septic arthritis. Bacteria can get into your joint and
cause rapid cartilage deterioration and bone damage. This can lead to
significant pain, swelling, redness, and loss of movement.

3.  The bacteria that cause bacterial joint inflammation can enter your body through
your:
 skin
 eyes
 ears
 mouth
 nose
 mucous membranes
 Some of the types of bacteria that can cause this infection include:
 Staphylococcus aureus:
 Streptococcus pneumonia:
 Neisseria gonorrhoeae:

4.  Collection
 Synovial fluid may be collected by syringe in a procedure
termed arthrocentesis, also known as joint aspiration.
 Arthrocentesis is the clinical procedure of using a syringe to collect synovial
fluid from a joint capsule. It is also known as joint aspiration. Arthrocentesis
is used in the diagnosis of gout, arthritis, and synovial infections such
as septic arthritis.

5.  Aspirated fluid is transferred to microbiology lab for further investigation.
 For the presence of
 Neisseria
Gram negative diplococci. Non-pathogenic species are sometimes present as
commensal in the upper respiratory tract.
Important pathogenic species are Neisseria meningitidis and Neisseria
gonorrhoeae.
 They are usually found inside the pus cells and are capsulated.

6.  GROWTH CHARACTERISTICS
Pathogenic Neisseriae are aerobic, require enriched media with 5-
10% CO2. Commonly used media are blood agar, chocolate agar.
 Blood agar
 Blood agar consists of a base containing a protein source (e.g. Tryptones), soybean protein digest, sodium chloride (Nacl) and
agar
 Prepare the blood agar base as instructed by the manufacturer. Sterilize by autoclaving at 121°C for 15 minutes.
 Transfer thus prepared blood agar base to a 50°C water bath.
 When the agar base is cooled to 50°C, add 5% sterile blood aseptically and mix well gently. Avoid formation of air bubbles.
(Note: If it is required to prepare a batch of blood agar plates, prepare few blood agar plates first to ensure that blood is
sterile).
 Dispense 15 ml amounts to sterile petri plates aseptically
 Label the medium with the date of preparation.
 Store the plates at 2-8°C, preferably in sealed plastic bags to prevent loss of moisture. The shelf life of thus prepared blood
agar is up to four weeks.

7.  Chocolate agar
 Containing red blood cells that have been lysed by slowly heating to 80°C.
 Some bacteria need growth factors such as NAD (factor V) and hemin (factor
X), which are inside red blood cells lysis of the red blood cells. The heat also
inactivates enzymes which could otherwise degrade NAD.