page_title: Orbital cellulitis
section_title: Causes
hierarchical_section_title: Orbital cellulitis / Causes
caption_attribution_description: English: Gram-positive stain, possibly showing staphylococcus aureus, which is one of the primary causes of orbital cellulitis
context_page_description: Orbital cellulitis is inflammation of eye tissues behind the orbital septum. It is most commonly caused by an acute spread of infection into the eye socket from either the adjacent sinuses or through the blood. It may also occur after trauma. When it affects the rear of the eye, it is known as retro-orbital cellulitis.
  It should not be confused with periorbital cellulitis, which refers to cellulitis anterior to the septum.
  Without proper treatment, orbital cellulitis may lead to serious consequences, including permanent loss of vision or even death.
context_section_description: Orbital cellulitis occurs commonly from bacterial infection spread via the paranasal sinuses, usually from a previous sinus infection. Other ways in which orbital cellulitis may occur are from blood stream infections or from eyelid skin infections. Upper respiratory infection, sinus infection, trauma to the eye, ocular or periocular infection, and systemic infection all increase one's risk of orbital cellulitis.
  Staphylococcus aureus, Haemophilus influenzae B, Moraxella catarrhalis, Streptococcus pneumoniae, and beta-hemolytic streptococci are bacteria that can be responsible for orbital cellulitis.
  Staphylococcus aureus is a gram-positive bacterium, which is the most common cause of staphylococcal infections. Staphylococcus aureus infection can spread from the skin to the orbit. This organism is able to produce toxins which promotes its virulence, leading to the inflammatory response seen in orbital cellulitis. Staphylococcus infections are identified by a cluster arrangement on gram stain. Staphylococcus aureus forms large yellow colonies when cultured (which is distinct from other Staph infections such as Staphylococcus epidermidis, which forms white colonies).
  Streptococcus pneumoniae is also a gram-positive bacterium responsible for orbital cellulitis due to its ability to infect the sinuses.  Streptococcal bacteria can invade surrounding tissues, causing the inflammatory response seen in orbital cellulitis (similar to Staphyloccoccus aureus). Streptococcal infections are identified on culture by their formation of pairs or chains. Streptococcus pneumoniae produce green (alpha) hemolysis, or partial reduction of red blood cell hemoglobin.
caption: Gram-positive stain, possibly showing staphylococcus aureus, which is one of the primary causes of orbital cellulitis.
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