Periorbital (Preseptal) Cellulitis

• Streptococcus pneumoniae in young children
• Staphylococcus aureus or Streptococcus pyogenes post-

  Traumatic causes

Orbital (Postseptal) Cellulitis

• Staphylococcus aureus, Streptococcus pyogenes,Streptococcus pneumoniae, Haemophilus influenzae and Enterobacteriaceae

Dacryocystitis

• Streptococcus pneumoniae, Staphylococcus aureus,Haemophilus influenzae, Streptococcus pyogenes, and Pseudomonas aeruginosa

Conjunctivitis

• Viral- Adenoviruses*, Herpes Simplex viruses types 1 and 2 (less common but more serious infection)
• Bacterial (pink-eye)-Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Pseudomonas aeruginosa, Neisseria gonorrhoeae and Neisseria meningitidis
• Chlamydial- Chlamydia trachomatis

Keratitis

• Bacteria*
  • Gram positive bacteria (Streptococcus pneumoniae, Staphylococcus epidermidis, Streptococcus pyogenes, Streptococcusviridans, enterococci and Peptostreptococcus) are most frequently obtained with the most common of them being Staphylococcus aureus.
  • Gram positive bacilli that cause keratitis include Corynebacterium diphtheriae, Bacillus and Clostridium
  • Gram negative bacilli that cause keratitis include Pseudomonas aeruginosa, Proteus mirabilis, Klebsiella pneumoniae, Serratia marcescens, Escherichia coliand Aeromonas hydrophila. Pseudomonas aeruginosa is one of the most destructive of the bacterial causes of keratitis.
  • Gram negative cocci or coccobacilli that cause keratitis include Neisseria gonorrhoeae, Neisseria meningitidis, Moraxella, Pasteurella multocida and Acinetobacter.
  • Ocular lymphogranuloma venereum is more serious than simple chlamydial conjunctivitis because corneal scars, conjunctival scars, and micropannus formation can occur (serotypes L1-L3 ofChlamydia trachomatis).
• Viruses
  • Herpes Simplex 1 and 2*- most common of viruses
  • Adenoviruses- epidemic keratoconjunctivitis
  • Varicella Zoster virus

  Respiratory Tract Infections
  

Acute Rhinosinusitis

• Usually caused by various respiratory viruses.

Acute Bacterial Rhinosinusitis

• Streptococcus pneumoniae
• Haemophilus influenzae (nontypable)

Common cold (Rhinitis)

• Rhinoviruses*
• Coronaviruses

Pharyngitis

• Adenovirus
• Herpes Simplex virus
• Epstein Barr Virus
• Coxsackie viruses
• Remember Streptococcus pyogenes (group A streptococcus is important because of the complications that can result (rheumatic fever).

Viral Croup

• Parainfluenza virus
• Influenza virus
• Respiratory syncytial virus (most common cause of bronchiolitis in children under 1 year of age).

Bacterial tracheitis

• Staphylococcus aureus

Epiglottitis

• Haemophilus influenzae type b (very rare now due to the Hib vaccine)

Bronchitis

• Respiratory viruses that infect the upper respiratory tract: influenza viruses A and B, parainfluenza viruses, adenovirus, respiratory syncytial virus, herpes simplex virus, rhinovirus, coxsackievirus A and B, and echovirus.
• Mycoplasma pneumoniae
• Chlamydophila pneumoniae (TWAR agent)- 5% of cases
• Streptococcus pyogenes

Bronchiolitis

• Respiratory Syncytial virus (RSV)

Pneumonia

Neonatal (0-1 month)

• Escherichia coli
• Streptococcus agalactiae (group B streptococcus)

Infants (1-6 month)

• Chlamydia trachomatis (afebrile pneumonia with staccato cough)
• RSV

Children (6month-5 year)

• RSV
• Parainfluenza virus

Children (5-15 year)

• Mycoplasma pneumoniae
• Influenza virus type A

Young Adults (16-30 yr)

• Mycoplasma pneumoniae

Older Adults

• Streptococcus pneumoniae*
• Haemophilus influenzae
•