Orbital Cellulitis Organism-Specific Therapy 

Specific Organisms and Therapeutic Regimens

Orbital cellulitis is an infection of the soft tissues of the orbit posterior to the orbital septum, not involving the globe. ^[1]  It is a serious condition with potentially devastating visual and life-threatening complications that can result from the following ^{[2, 3, 4]} :

• Extension of an infection from the periorbital structures, most commonly the paranasal sinuses
• Direct inoculation of the orbit due to trauma or surgery
• Hematogenous spread from bacteremia

It is more common in the pediatric population and usually is a complication of acute or chronic sinusitis. ^{[5, 6, 7]}

Bacteria that typically cause orbital complications, such as Staphylococcus aureus, Haemophilus influenzae, Streptococcus species, and anaerobic species, including Fusobacterium and Bacteroides, tend to mirror those that cause acute sinusitis. ^{[8, 9]}

Orbital cellulitis can also be caused by non-spore-forming anaerobes Aeromonas hydrophila, Pseudomonas aeruginosa, and Eikenella corrodens. Immunocompromised individuals may harbor fungal pathogens than can cause an invasive orbital cellulitis including Mucorales which can cause mucormycosis seen in those with diabetic ketoacidosis or renal acidosis, and Aspergillus seen in neutropeic patients or those with other immune deficiencies such as HIV. Another rare reported cause of orbital cellulitis includes Mycobacterium tuberculosis. ^{[1, 10]}

Understanding the prevalence and antibiotic resistance patterns of pathogens in the community is necessary for adequate treatment. Prompt recognition and early aggressive treatment are crucial in controlling the spread. ^[11] Prior to the discovery of antibiotic treatment, blindness from orbital cellulitis was seen in approximately 20% of cases, with a mortality rate as high as 40% from intracranial abscess. ^{[12, 13]}

Organism-specific therapeutic regimens for orbital cellulitis are discussed below.

Methicillin-sensitive Staphylococcus aureus (MSSA)

MSSA orbital cellulitis may be treated with the following regimens:

Nafcillin or Oxacillin

• 2 g IV q4h OR

Ampicillin-sulbactam 

• 1.5-3 g IV q6h  OR

Cefuroxime 

• 1.5 g IV q8h  OR

Ceftriaxone 

• 1-2 g/day IV  OR

Clindamycin 600 mg IV q8h

Methicillin-resistant S aureus (MRSA)

Vancomycin 

• 1 g (15 mg/kg) IV q12h  or

Daptomycin 

• 6 mg/kg IV q24h56

Streptococcus pneumonia

Amoxicillin-clavulanate 

• 875 mg/125 mg (20-40 mg/kg) PO q12h  OR

Cefpodoxime 

• 200-400 mg (5 mg/kg) PO q12h  OR

Cefdinir 

• 600 mg/day (14 mg/kg/day) PO

Streptococcus pyogenes

Ampicillin-sulbactam

• 1.5-3 g IV q6h  or

Ceftriaxone

• 1-2 g/day IV  or

Clindamycin

• 600 mg IV q8h

Hemophilus Influenzae

Amoxicillin-clavulanate 

• 875 mg/125 mg (20-40 mg/kg) PO q12h  OR

Ampicillin-sulbactam

• 1.5-3 g IV q6h OR

Aeromonas Hydrophilia

Levofloxacin

• 500-750 mg PO/IV q24h OR

Ceftriaxone 

• 1-2 g/day IV 

Pseudomonas Aeruginosa

Levofloxacin

• 500-750 mg PO/IV q24h OR

Meropenam

• 1g IV q8h OR

Gentamicin

• 1mg/kg IV q8h

Zygomycetes or Aspergillus

Voriconazole 

• 6 mg/kg IV q12h for 2 doses, then  4 mg/kg IV q12h  OR

Voriconazole

• 200-300 mg PO q12h  OR
•  

Amphotericin B deoxycholate 

• 1 mg/kg IV q24h  OR

Liposomal amphotericin

• 3-5 mg/kg q24h

Special considerations

Patients with orbital cellulitis frequently complain of fever and malaise and report a history of recent sinusitis or upper respiratory tract infection. Orbital signs include preseptal cellulitis with limitation in ocular movements, pain with ocular movements, and proptosis.

Imaging studies are crucial in defining the extent and nature of orbital involvement and determining management. CT scanning of the sinus and orbit with and without contrast is the gold standard.

Consider surgical drainage if the response to appropriate antibiotic therapy is poor within 48-72 hours or if CT scans show the sinuses to be completely opacified. If the presence of a drainable fluid collection within the orbital soft tissues is evident on CT scan, surgical drainage should be considered. Surgical intervention is prompted over antibiotic management for large abscesses greater than 10mm or 1cm in diameter. Smaller abscesses can be followed clinically unless patients have failed medical therapy, continue to show progression of symptoms, or develop complications (eg, visual changes, cavernous sinus thrombosis, intracranial involvement). ^{[14, 15]}

Consider orbital surgery, with or without sinusotomy, in every case of subperiosteal or intraorbital abscess formation, and some surgeons may consider leaving drains in place for several days to encourage continues drainage after the initial washout procedure.

In cases of fungal infection, surgical debridement of the orbit is indicated and may necessitate exenteration of the orbit and the sinuses. Surgical debridement also applies to mycobacterial infection of the orbit. Surgery can be performed through the orbit or through endoscopic transcaruncular surgery.

Canthotomy and cantholysis should be performed on an emergent basis if an orbital compartment syndrome is diagnosed via increased intraocular pressure and other clinical signs at any point in the course of the disease.