INFECTIVE & BACTERIALCONJUNCTIVITIS

Infective conjunctivitis, i.e., inflammation of the
conjunctiva caused by microorganisms is the
commonest variety. This is in spite of the fact that
the conjunctiva has been provided with natural
protective mechanisms in the form of :

•  Low temperature due to exposure to air,
•  Physical protection by lids,
•  Flushing action of tears,
•  Antibacterial activity of lysozymes and
•  Humoral protection by the tear immunoglobulins.

 BACTERIAL CONJUNCTIVITIS
There has occurred a relative decrease in the
incidence of bacterial conjunctivitis in general and
those caused by gonococcus and corynebacterium
diphtheriae in particular. However, in developing
countries it still continues to be the commonest type
of conjunctivitis. It can occur as sporadic cases and
as epidemics. Outbreaks of bacterial conjunctivitis
epidemics are quite frequent during monsoon season.

Etiology
A. Predisposing factors for bacterial conjunctivitis,
especially epidemic forms, are flies, poor hygienic
conditions, hot dry climate, poor sanitation and dirty
habits. These factors help the
  infection to establish,
as the disease is highly contagious.

B. Causative organisms. It may be caused by a wide
range of organisms in the following approximate order
of frequency :

•  Staphylococcus aureus is the most common cause of bacterial conjunctivitis and blepharoconjunctivitis.
•  Staphylococcus epidermidis is an innocuous flora of lid and conjunctiva. It can also produce blepharoconjunctivitis.
• Streptococcus pneumoniae (pneumococcus) produces acute conjunctivitis usually associated with petechial subconjunctival haemorrhages. The disease has a self-limiting course of 9-10 days.
•  Streptococcus pyogenes (haemolyticus) is virulent and usually produces pseudomembranous conjunctivitis.
•  Haemophilus influenzae (aegyptius, Koch- Weeks bacillus). It classically causes epidemics of mucopurulent conjunctivitis, known as ‘red-eye’ especially in semitropical countries.
•  Moraxella lacunate (Moraxella Axenfeld bacillus) is most common cause of angular conjunctivitis and angular blepharoconjunctivitis.
• Pseudomonas pyocyanea is a virulent organism. It readily invades the cornea.
•  Neisseria gonorrhoeae typically produces acute purulent conjunctivitis in adults and ophthalmia neonatorum in new born. It is capable of invading intact corneal epithelium.
•  Neisseria meningitidis (meningococcus) may produce mucopurulent conjunctivitis.
•  Corynebacterium diphtheriae causes acute membranous conjunctivitis. Such infections are rare now-a-days.

C. Mode of infection. Conjunctiva may get infected
from three sources, viz, exogenous, local surrounding
structures and endogenous, by following modes :

1. Exogenous infections may spread: (i) directly
through close contact, as air-borne infections or
as water-borne infections; (ii) through vector
transmission (e.g., flies); or (iii) through material
transfer such as infected fingers of doctors,
nurses, common towels, handkerchiefs, and
infected tonometers.

2. Local spread may occur from neighbouring
structures such as infected lacrimal sac, lids, and
nasopharynx. In addition to these, a change in
the character of relatively innocuous organisms
present in the conjunctival sac itself may cause
infections.

3. Endogenous infections may occur very rarely
through blood e.g., gonococcal and meningococcal
infections.

Pathology
Pathological changes of bacterial conjunctivitis
consist of :
1. Vascular response. It is characterised by
congestion and increased permeability of the
conjunctival vessels associated with proliferation
of capillaries.

2. Cellular response. It is in the form of exudation
of polymorphonuclear cells and other
inflammatory cells into the substantia propria of
conjunctiva as well as in the conjunctival sac.

3. Conjunctival tissue repsonse. Conjunctiva
becomes oedematous. The superficial epithelial
cells degenerate, become loose and even

 desquamate. There occurs proliferation of basal
layers of conjunctival epithelium and increase in
the number of mucin secreting goblet cells.

4. Conjunctival discharge. It consists of tears,
mucus, inflammatory cells, desquamated epithelial
cells, fibrin and bacteria. If the inflammation is
very severe, diapedesis of red blood cells may
occur and discharge may become blood stained.
Severity of pathological changes varies depending
upon the severity of inflammation and the causative
organism. The changes are thus more marked in
purulent conjunctivitis than mucopurulent
conjunctivitis.