Case Study on Infectious Conjunctivitis and Gentamicin Mechanism of Action

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1. Background of the case study (Total: 5 marks)
1.1 What is infectious conjunctivitis?
The inflammation of the conjunctiva, lining of the eyelid and eye, due to infection by virus
or bacteria, leads to infectious conjunctivitis. It can spread due to contact with the
contagious towel, handkerchief etc. It results in swelling, irritation, fluidic discharge from
eyes. The cause of infectious conjunctivitis can be detected by examining and culture of
the eye discharge (Bishop, 2016a).
1.2 Of the four micro-organisms listed below, justify which one is more likely to be the cause
of John’s eye infection. Indicate why the other micro-organisms from the list are least likely
to cause the infection.
Legionella pneumophila
Yes or no, with reason:
Yes, but less likely to cause conjunctivitis, because it is a gram-negative bacteria. It is a
primary bacteria causing pneumonia, but can infect the eye causing conjunctivitis (Bishop,
2016a).
Plasmodium ovale
Yes or no, with reason:
No. It is a protozoa that cannot cause conjunctivitis (Bishop, 2016b).
Adenovirus
Yes or no, with reason:
Yes. Viral conjunctivitis can be caused by adenovirus (adenoviral keratoconjunctivitis)
(Bishop, 2016b)
Staphylococcus aureus
Yes or no, with reason:
Yes. This gram positive bacteria is the most common cause of conjunctivitis. The
carbohydrate layer of the cell wall of bacteria intrigues inflammation, leading to tissue
damage. The bacterial released proteins like alpha-toxin, beta toxin, leukocidins initiate
the process (Department of Health. 2017).

2. Mechanism of action and adverse reactions (Total: 5 marks)
2.1 Describe the mechanism of action of gentamicin?
Gentamicin is a broad-spectrum antibiotic, aminoglycoside in nature. It kills the gram-
positive bacteria in a concentration-dependent manner, and can also kill the gram-
negative bacteria efficiently. It helps in the prevention of infection, by blocking the protein
synthesis of the bacteria. It binds to 30S subunit of ribosome, blocking the initiation of
translation of protein. It does not promote the interaction of the messenger-RNA and
transfer-RNA, thus stalling the process of protein synthesis (Hill, Hall & Glew (Eds.).
2017).
2.2 Name two adverse reactions of this drug?
Gentamicin can cause potential damage such as nephrotoxicity and neurotoxicity. They
affect the proximal tubular cells of the kidney. After filtering by the kidney, they are actively
taken by proximal tubular epithelial cells and are incorporated in the lysosomes during
phospholipid metabolism. They also exert toxic effects on the kidney and cause renal
vasoconstriction. The aminoglycoside of gentamicin causes neuromuscular blockade, and
is deposited in the lysosomes, causing lysosomal morphological anomaly. The
neuromuscular blockage can lead to conditions as myasthenia gravis (Hill, Hall & Glew
(Eds.). 2017)
3. Physiological basis of signs (Total: 10 marks)
3.1 sign 1:
One sign that is observed in John’s eye was that it became red and swollen
Explanation of this phenomenon:
John was diagnosed with conjunctivitis. Eyes generally become red and swollen due to
inflammation and accumulation of fluid in conjunctivitis. The infectious conjunctivitis
resulted in immune reaction in the eye that released a lot of histamines which
accumulated in the region, intriguing the blood vessel dilation that resulted in the red eye.
The site of conjunctivitis is very close to the meibomian gland. The bacterial infection and
the inflammation resulted in the blockage of the oil-producing meibomian gland that
caused the inflammation. The above mechanisms can result in redness and swelling of
eyes. The inflammation of the columnar epithelium generally causes swelling in the
glands, and hence, there is swelling of the eye. The blood vessel dilation due to exposure

to infections is the main cause of redness of the eye. The ocular surface of the eye can
inflame and become reddish due to a potent allergen (Department of Health, 2017)
3.2 sign 2:
There was purulent and sticky discharge noticed from the eye of John
Explanation of this phenomenon:
Conjunctivitis is an allergic reaction caused due to any kind of infections that leads to the
discharge of an excessive amount of sticky, purulent fluid. There is inflammation of the
mucous layer and the ocular layer of the eye that results in such condition. Because of
excessive inflammation of the layers of the eye, along with associated tear glands, there is
huge discharge of fluids or tear from the eye (epiphora). Due to allergic reaction and
irritation in the eye, the mucous layer also secretes its component in the teary water and
so it becomes sticky and purulent. The mucoid components mainly categorize from
different immunoglobulins, lysozymes, and glycoproteins to inorganic salts. In expert
opinions, the watery discharge (rheum) has some advantages. They include the fact that
potentially harmful materials and debris are ejected out from the eye helping in curation of
the infection. Hence, the tear glands, mucous gland, and meibomian gland together
release its component in huge amount to form the fluidic discharge (Jarvis, 2016)
3.3 sign 3:
John complained that he possessed pain in his eyes.
Explanation of this phenomenon:
Eye pain that occurs during conjunctivitis can be called as ophthalmalgia. Conjunctivitis is
a potent allergic condition of the eye resulting in inflammation of the ocular membrane and
the orbital membrane. There is inflammation of the membranes which causes redness and
itching causing further irritation to cause aching pain in the ocular and the orbital
membrane. Conjunctivitis can lead to corneal abrasion and blepharitis (inflammation of the
oil glands), chalazon that provides pressure on the optic nerves which can potentially
cause pain. Pain is associated with the input of foreign objects in the eye. During
conjunctivitis, there is an insertion of a pool of bacteria, virus, dust and other particles
which can potentially cause the symptom of pain. That kind of eye pain in conjunctivitis
can be treated efficiently with eye drops, to ease the condition. It can also resolve in itself