Bacteria and fungi can cause several common eye infections: - Conjunctivitis ("pink eye") is caused by bacterial or viral infection of the conjunctiva and causes redness, watering and discharge from the eye. - Keratitis is inflammation of the cornea that can be caused by bacterial infection following an eye injury. It causes pain and impaired vision. - Fungal eye infections are rare but can develop after a plant injury to the eye. They cause pain, inflammation, tearing and vision changes. - Parasites like Acanthamoeba can also infect the cornea and lead to vision loss if not treated.

1. General and Ocular
Microbiology
Overview

2. Morphologyandprinciplesofcultivatingbacteria
Bacteria are complex and highly variable microbes.
They come in four basic shapes:
spherical (cocci),
rod-shaped (bacilli),
arc-shaped (vibrio),
spiral (spirochete)
Bacterial shapes:

3. Cultivation of Bacteria
Cultivation/Culturing of Bacteria : A microbial culture, is a method of multiplying microorganisms by
letting them reproduce in predetermined culture media under controlled laboratory conditions.
Types of microbial culture media
Bacteria cultivation is a biological activity wherein microorganisms multiply themselves in a predetermined
culture media under laboratory conditions.
Whereas, microbial culture media are used to identify the types of microorganisms and their abundance in
culture media are being tested precisely. It could be observed that MTCC has around 20000 microbial cultures.
More than 80% of the microbial culture available in MTCC is of Indian origin. Culture bacteria are the initial
step to study the morphology of bacteria.
There are various procedures of cultivating bacteria, which are as follows:
• Isolation of bacteria
• Creating antigens for laboratory use
• To estimate viable counts
• Testing for antibiotic sensitivity
• Maintenance of stock culture
• To separate different types of bacteria with the help of microbial culture media
• Certain manipulation of cells and genetic studies of the cell also need that bacterium to be cultured in vitro.

4. Sterilizationanddisinfectionsusedinlaboratoryandhospitalpractice
sterilization is the complete elimination or destruction of all forms of microbial life and is
accomplished in health care facilities by either physical or chemical processes.
Methods used in sterilization procedures include.

5. Disinfectants : are chemical agents applied to non-living objects in order to destroy bacteria,
viruses, fungi, mold or mildews living on the objects.
• Hydrogen Peroxide
• Quaternary Ammonium
Compounds (Quats)
• Chlorine Compounds
• Alcohols
• Aldehydes
• Iodophors
• Phenolic Compounds
The “active ingredient” in each disinfectant formula is what kills pathogens, usually by disrupting
or damaging their cells. Active ingredients are usually aided by other ingredients with various
purposes. For example, surfactants can be added to a disinfectant formula to provide consistent
wetting on a surface or to help in cleaning.

6. DifferencebetweendisinfectionSterilization
Disinfection Sterilization
In this, the number of harmful microbes is minimized to a negligible level. In this, the medium is made completely free from all microbes.
It kills only vegetative cells and not the spores. It kills both vegetative cells and spores.
Wounds are disinfected – with agents such as hydrogen peroxide or rubbing
alcohol.
Wounds cannot be sterilized – as it may kill surrounding healthy cells.
Disinfection only reduces the effect of microbes. Sterilization completely rids microbes from the surface
Chemical methods are used for disinfection Combination of heat, irradiation, high pressure, chemical and physical methods are
used for sterilization
Phenol, alcohol, chlorine, iodine are some of the disinfecting agents. High temperatures, steam, radiation, filtration are some of the sterilization
techniques.
Only adequate cleanliness Extreme cleanliness
Used in daily life. Used primarily for medical and research purposes.
For eg., pasteurization, disinfecting urinals, etc. For eg., sterilization of instruments used during surgery by autoclaving.

7. Commonbacterialinfectionofeye
Conjunctivitis is inflammation of the conjunctiva, most commonly due to an infection.
LEARNING OBJECTIVES
Describe the various causes of conjunctivitis and keratitis and its symptoms
conjunctivitis: An inflammation of the conjunctiva often due to infection.
keratitis: Inflammation of the cornea.
Common Eye Infections
CONJUNCTIVITIS
Conjunctivitis, also called pink eye or Madras eye, is inflammation of the conjunctiva, which
consists of the outermost layer of the eye and the inner surface of the eyelids.
Symptoms and Diagnosis
• An inflamed, red eye (hyperaemia), irritation (chemosis), and watering (epiphora) of the eyes
are symptoms common to all forms of conjunctivitis.
• However, the pupils should be normally reactive and the visual acuity normal.
• Bacterial conjunctivitis due to common pyogenic (pus-producing) bacteria causes marked
grittiness/irritation and a stringy, opaque, greyish or yellowish mucopurulent discharge that
may cause the lids to stick together, especially after sleep.
• Another symptom that could be caused by bacterial conjunctivitis is severe crusting of the
infected eye and the surrounding skin.

8. • KERATITIS
• Keratitis is a condition in which the eye’s cornea, the front part of the eye, becomes inflamed.
The condition is often marked by moderate to intense pain and usually involves impaired
eyesight..
Figure: Keratitis: An eye with non-ulcerative sterile keratitis
• Causes and Treatment
• Keratitis has multiple causes.
• Bacterial infection of the cornea can follow from an injury or from result from wearing
contact lenses.
• The bacteria involved are Staphylococcus aureus and, for contact lens wearers, Pseudomonas
aeruginosa.
• Pseudomonas aeruginosa contains enzymes that can digest the cornea.
• Treatment depends on the cause of the keratitis.
• Infectious keratitis can progress rapidly, and generally requires urgent antibacterial,
antifungal, or antiviral therapy to eliminate the pathogen.

9. Fungal eye infections Fungal eye infections are extremely rare, but they can be very serious. The most common
wayforsomeonetodevelopafungaleyeinfectionisasaresultofaneyeinjury,particularlyiftheinjurywascaused
by plant material such as astick or a thorn.Inflammation or infection of the cornea (theclear, front layer of the eye)
isknownaskeratitis,andinflammation orinfectionintheinterioroftheeyeiscalledendophthalmitis.
• Fungal Eye Infections Symptoms
• An infection can develop after even a minor injury to your eye, such as debris flying into it or
an accidental fingernail scratch. It may take anywhere from just a couple of days to several
weeks to become apparent.
• Even if you've only had a minor trauma, you should watch for:
• Pain in the eye
• Vision blurriness
• Eye inflammation and redness
• Extensive tearing
• Discharge from the eye
• Types of fungi that cause eye infections
Many of different types of fungi can cause eye infections. Common types include:
• Fusarium – a fungus that lives in the environment, especially in soil and on plants
• Aspergillus – a common fungus that lives in indoor and outdoor environments
• Candida – a type of yeast that normally lives on human skin and on the protective lining
inside the body called the mucous membrane.
Fungal eye infections

10. Common viral and parasitic infections of eye
Parasites are organisms that live in, or on, another organism. The host organism
provides the parasites with ideal living conditions and a source of nutrients. Most
parasites damage their hosts in some way.
Three types of parasites that cause diseases in humans. These are:
• protozoa, or single-celled organisms, which can multiply inside of the body, which can lead to
serious infections
• helminths, which include flatworms, flukes, and roundworms
• ectoparasites, or blood-sucking invertebrates, include mosquitoes, lice, ticks, and mites
Acanthamoeba keratitis is a rare but serious eye infection that occurs due to a single-celled organism
called an amoeba. These are present in bodies of water, the soil, and the air.
Acanthamoeba parasites infect the cornea, the transparent covering of the eye. Without treatment,
Acanthamoeba keratitis can lead to severe pain, and in some cases, loss of vision.
.
• Symptoms
• Symptoms can include:
• blurred vision
• eye pain
• eye redness
• light sensitivity
• excessive tearing
• the feeling that something is in the eye

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