This document discusses ocular microbiology. It begins by outlining the teaching objectives which are to describe common eye pathogens, the diseases they cause, and their transmission, prevention and treatment. It then provides an overview of common eye infections like blepharitis, dacryocystitis, conjunctivitis and their causes. Specific pathogens discussed include bacteria like Staphylococcus, viruses like herpes and adenovirus, and parasites that cause trachoma and river blindness. Laboratory diagnosis of conditions like blepharitis and conjunctivitis is also summarized.

1. Ocular Microbiology
By: KIFLOM HAGOS
MEKELLE-ETHIOPIA

2. Teaching Objectives
After completing this session, the students are expected to
 Describe the most common bacterial , virus, fungi and
parasite infection in humans eyes.
Identify the diseases caused by common bacterial, virus,
fungi and parasite pathogens of eyes.
Describe the reservoirs mode of transmission ,epidemiology,
Prevention, control and treatment of common bacterial, virus,
fungi and parasite pathogens of eyes.

3. Ocular infections
 Ocular infections can be divided into external structures—eyelids,
conjunctiva, sclera, and cornea------internal sites.
 The major defense mechanisms of the eye are the tears and the
conjunctiva, as well as the mechanical cleansing that occurs with
blinking of the eyelids.
 The tears contain secretory IgA and lysozyme, and the conjunctiva possesses
numerous lymphocytes, plasma cells, neutrophils, and mast cells, which can
respond quickly to infection by inflammation

4. CONT..
• The internal eye is protected from external invasion primarily
by the physical barrier imposed by the sclera and cornea
• If these are breached (e.g, by a penetrating injury or
ulceration), infection becomes a possibility.
• In addition, infection may reach the internal eye via the blood-
borne route to the retinal arteries and produce chorio-retinitis
and/or uveitis.

5. Cont..
• Other causes of inflammation of the external or internal eye
can involve autoimmune, which may be provoked by
infectious agents or diseases such as rheumatoid arthritis.
COMMON CLINICAL CONDITIONS
Blepharitis: is an acute or chronic inflammatory disease of the
eyelid margin. It can take the form of a localized inflammation in
the external margin (stye) or a granulomatous reaction to
infection and plugging of a sebaceous gland of the eyelid.

6. Cont..
• Dacryocystitis is an inflammation of the lacrimal sac. It
usually results from partial or complete obstruction within the
sac or nasolacrimal duct.
• Conjunctivitis is a term used to describe inflammation of the
conjunctiva; it may extend to involve the eyelids, cornea
(keratitis), or sclera (episcleritis).
• Extensive disease involving the conjunctiva and cornea is
often called keratoconjunctivitis. Progressive keratitis can
lead to ulceration, scarring, and blindness.

7. Cont..
• Ophthalmia neonatorum is an acute, sometimes severe,
conjunctivitis or keratoconjunctivitis of newborn infants.
• Endophthalmitis is rare, but often leads to blindness even
when treated aggressively. The term refers to infection of the
aqueous or vitreous humor
• Chalazion It is a persistant inflammatory response due to
ocular bacterial and fungal infections
• Uveitis consists of inflammation of the uveal tract—iris,
ciliary body, and choroid.
• Chorioretinitis, in which inflammatory infiltrates are seen in
the retina; this infection can lead to destruction of the choroid
and inflammation of the optic nerve (optic neuritis)

8. Trachoma: Ocular trachoma is a chronic Chlamydia trachomatis
infection of the epithelial cells of the eye and a major cause of
blindness in certain parts of the world. Trachoma and simple
conjunctivitis are caused by different strains of C. trachomatis.
Keratitis: A more serious eye infection than conjunctivitis.
Herpes simplex viruses (HSV-1 and HSV-2) and Acanthamoeba
cause two different forms of the disease.
River Blindness: A chronic parasitic helminth infection
.The condition is caused by a symbiotic pair, the bacterium
Wolbachia living inside the helminth Onchocerca. The worm is
transmitted to humans by small biting black flies.

9. Cont..
• The external ocular surface harbors commensal organisms, such as
Staphylococcus species, Corynebacterium species, and
Propionibacterium species, which form the resident flora. The
intraocular tissues and spaces, however, are sterile.
• While the conjunctiva is protected by blood supply, the cornea is
avascular; therefore, the types of organisms invading these tissues
may vary.

10. Cont..
• The intraocular tissues are relatively immune-privileged and can
be infected by any organism that manages to enter the inside of
the eye.
• Trauma is an important predisposing factor for infection of the
cornea and intraocular tissues. While exogenous infections are
most common, eye infection may develop by spread of infection
from neighbouring organs or hematogenously.
• Ocular infections may be caused by bacteria, fungi, parasites, or
viruses, and each of these may produce a spectrum of disease.

15. Blepheritis :
• Staphylococcal blepharitis : This is a chronic inflammations
of eyelid margins colonized by Staphylococcus aureus and
Staphylococcus epidermidis
• It has been shown that the majority of S. aureus isolates from
blepharitis produce : alpha, beta and delta lysins.
• CMI response with hypersensitivity to S. aureus has been
implicated in the pathogenesis of this disease.

16. Lab. dx
• For laboratory diagnosis lid margin swabs are collected in case
of blepharitis.
• Sterile cotton tipped swab or calcium alginate swab moistened
in Hank’s balanced salt solution (HBSS) or brain heart
infusion broth (BHIB) or normal saline is rubbed over the lid
margin.
• Swab is inoculated directly onto Blood agar (BA), Chocolate
agar (CA), MacConkey agar (MA) and Sabouraud dextrose
agar (SDA).

17. Conjunctivitis :
• Infection of the conjunctiva is relatively common.
• It can be caused by specific microorganisms that have a
predilection for eye tissues, by contaminants that proliferate due to
the Presence of a contact lens or an eye injury, or by accidental
inoculation of the eye by a traumatic event.
Types of Bacterial Conjunctivitis :
Hyperacute – N.gonorrhoeae, Neisseria . meningitidis
Acute - pathogenic bacteria
Chronic – S. aureus and Moraxella lacunata S. pneumoniae H.
infleunza , and H.aegyptius

18. Cont..
• Several pathogenic bacteria can cause conjunctivitis but the most frequently
associated bacteria are S. aureus, S. pneumoniae and Haemophilus influenzae
(H. aegyptius-Koch-Week bacillus).
• H. influenzae causes acute purulent conjunctivitis of a longer duration than
other organisms and in immunocompromised persons complication of corneal
scrarring.
• Hyperacute purulent conjunctivitis caused by N.gonorrhoeae occurs in
neonates (Ophthalmia neonatorum) and young adults with complication of
ulcerative keratitis resulting in permanent visual loss and corneal perforation,

19. • S. pyogenes, N. gonnorhoeae H. influenzae and rarely S. aureus
and S. pneumoniae cause the severe form of-pseudomembranous
conjunctivitis which should be differentiated from membranous
conjunctivitis caused by C. diphtheriae.
• Diphtheritic conjunctivitis is associated with necrosis and
sloughing of conjunctival epithelium due to diffusible toxins
produced by the bacterium

20. • Chronic Conjunctivitis : Conjunctivitis caused lasting more
than 4 weeks is referred to as chronic conjunctivitis and is
usually caused by S. aureus and Moraxella lacunata.
– The later organism is associated with angular
blepharoconjunctivitis and may cause epidemics.
Sign and symptoms
Inflammation of conjunctiva tissue almost always causes a
discharge of some sort.
Most bacterial infections produce a milky discharge, whereas.
It is typical for a patient to wake up in the morning with an
eye ―glued‖ shut by secretions that have accumulated and
solidified through the night.

21. Cont..
• Some conjunctivitis cases are caused by an allergic response, and
these often produce copious amounts of clear fluid as well.
• Allergic conjunctivitis is typically divided into five types:
seasonal allergic conjunctivitis (SAC), perennial allergic
conjunctivitis (PAC), vernal keratoconjunctivitis (VKC), atopic
keratoconjunctivitis (AKC) and giant papillary conjunctivitis
(GPC).
• The pain generally is mild, although often patients report a gritty
sensation in their eye(s). Redness and eyelid swelling are
common, and in some cases patients report photophobia .

22. LABORATORY DIAGNOSIS OF CONJUNCTIVITIS
• In external bacterial infections of the eye, etiologic diagnoses
can usually be established by Gram stain and culture of surface
material.
– The specimen could be Sterile moistened cotton swab
– Conjunctival scrapings for C. trachomatis
– Immunoflorescent staining for C.trachomatis
Several diagnostic methods are available to detect C. trachomatis
in direct smears from the lesions such as Giemsa stain cytology,
fluorescent antibody test (FAT), enzyme immune assay (EIA)
using either monoclonal or polyclonal antibodies.

24. Growth of bacteria on BAP

26. Lacrimal apparatus infections
Dacroadenitis - inflammation of the lacrimal gland
Most common causes of infection in lacrimal system are
Nocardia, species Actinomyces and anaerobic bacteria, or a
mixed flora of both gram positive and gram negative bacteria
Therefore apart from aerobic cultures, anaerobic cultivation is
necessary
Pus from Lacrimal sac may be obtained by slight pressure
over the lower eyelid at the inner canthus and pus would come
out of the punctum from infected canaliculus

27. Scleritis
Clinical presentation
Localised firm tender nodule scleral ulcer /abscess
; relatively uncommon inflammation pyogenic /
granulamatous / immune mediated

28. Viral Conjunctivitis :
• Viral conjunctivitis, a highly infectious condition, is a self
limiting disease with low morbidity.
• An acute follicular conjunctivitis of sudden onset often with
respiratory and systemic symptoms
• Preauricular lymphadenopathy, lid oedema, conjunctival
haemorrhages and corneal changes are often associated with
this condition.

29. 29
Eye Infections
• Mild ocular involvement may be part of the respiratory-
pharyngeal syndromes
• Pharyngoconjunctival fever tends to occur in outbreaks
– at children's summer camps ("swimming pool
conjunctivitis")
– associated with types 3 & 7
• Duration of conjunctivitis is 1–2 weeks
• Complete recovery with no lasting sequelae is the common
outcome
Adenovirus Eye Infections

30. 30
Eye Infections…
- A more serious disease is epidemic keratoconjunctivitis
– highly contagious and occurs mainly in adults
– viruses can remain viable for several weeks on sinks and hand
towels
– The disease is characterized by
• acute conjunctivitis
• followed by keratitis that usually resolves in 2 weeks
• may leave subepithelial opacities in the cornea for up to 2
years
– It is caused by types 8, 19, and 37.
Adenovirus Eye Infections

31. • The viruses spread rapidly in the community as a result of
respiratory tract to eye, eye to eye and via infected tissues
and clothes and other fomites and contaminated swimming
pools.
• Laboratory diagnosis of adenoviral conjunctivitis consists of
detection of virus by direct methods and isolation of the
infecting agent.
• The most sensitive method and isolation of the infecting
agent, the most sensitive method of diagnosis of adenovirus
conjunctivitis is its isolation by conventional test tube cell
cultures.

33. 33
Keratoconjunctivitis
• Recurrent lesions of the eye are common as
– dendritic keratitis or corneal ulcers or as vesicles on the eyelids
– Permanent opacification and blindness
Figure Herpes simplex virus
(HSV) keratitis. Dendritic
ulcers, seen here on the
cornea, are common in
recurrent HSV infections
Herpes Simplex Viruses

34. Follicular conjunctivitis:
 Eyelid vesicles, preauricular lymphadenopathy and sometimes
ulcerative blepharitis, usually unilateral may be diagnosed as
due to HSV.
 Recurrent herpes occurs in about 25% of patients and cornea is
more than involved.
Varicella zoster virus (VZV)
 May cause ocular complications, following reactivation
of latent endogenous virus
 Occur in nearly 60 to 70% of patients with
involvement of ophthalmic division of trigeminal nerve.
34

35. • A papillary, follicular or membranous conjunctivitis may
occur.
• In 65% of cases cornea is affected. Distinctive skin
eruptions on the eyelid and forehead are diagnostic.
Involving the ophthalmic division of the trigeminal nerve with associated
conjunctivitis and involvement of the side of the nose
35

36. • Laboratory diagnosis of HSV and VZV conjunctival
infections are similar to what is detailed under
infectious keratitis.
• Acute follicular conjunctivitis may be caused by
Influenza A virus, Newcastle disease virus and
Cytomegalovirus. Molluscum contagiosum may
cause chronic toxic conjunctivitis.
36

37. Conjunctivitis
37

38. Trachoma
• Ocular trachoma is a chronic Chlamydia trachomatis
infection of the epithelial cells of the eye
• It is an ancient disease and a major cause of blindness
several million cases occur endemically in parts of Africa
and Asia in certain parts of the world.
• Transmission is favored by contaminated fingers,
fomites, fleas, and a hot, dry climate.
• It is caused by a different C. trachomatis strain than the
one that causes simple conjunctivitis.
38

39. Cont..
• Ongoing infection or many recurrent infections with this
strain eventually lead to chronic inflammatory damage
and scarring.
• The first signs of infection are a mild conjunctival
discharge and slight inflammation of the conjunctiva.
• These symptoms are followed by marked infiltration of
lymphocytes and macrophages into the infected area.
• As these cells build up, they impart a pebbled (rough)
appearance to the inner aspect of the upper eyelid
39

40. Cont..
• In time, a vascular pseudomembrane of exudates and
inflammatory leukocytes forms over the cornea, a condition
called pannus, which lasts a few weeks
• Chronic and secondary infections can lead to corneal damage
and impaired vision.
• Early treatment of this disease with azithromycin is highly
effective and prevents all of the complications.
40

41. 41
Chlamydial conjunctivitis is the
commonest form of neonatal
conjunctivitis

42. Trachoma
Epidemiology
• > 400 million people throughout the world have
trachoma ( 20 million are blinded by it )
• Most prevalent in
– Africa
– Asia
– The Mediterranean basin
– childhood infection may be universal, and severe
blinding disease is common
42
hygienic conditions
are poor and water
is scarce

43. Cont..
Prevention and Treatment
• Good hygiene is the only way to prevent conjunctivitis in
adults and children other than neonates
• In newborn children should be administered antimicrobials
in their eyes after delivery to prevent neonatal conjunctivitis
from either N. gonorrhoeae or C. trachomatis.
• Treatment of those infections, with erythromycin, both
topical and oral If N. gonorrhoeae is confrmed, oral
therapy is usually switched to ceftriaxone
.
43

44. • Ciprofloxacin eye drops are a common choice. Erythromycin
or gentamicin are also often used.
• Because conjunctivitis is usually diagnosed based on clinical
signs, a physician may prescribe prophylactic antibiotics even
if a viral cause is suspected.
S-A-F-E strategy
• S- Surgery for deformed eyelids
• A-Azithromycin therapy periodically
• F-Face washing and hygiene and
• E- Environmental improvement
44

45. Trachoma
45

46. Summery
Eye Diseases Caused by Microorganisms
Conjunctivitis: Infection of the conjunctiva (commonly
called pinkeye) has many different clinical presentations.
Neonatal eye infection is usually associated with Neisseria
gonorrhoeae or Chlamydia trachomatis;
They are transmitted vertically via a genital tract infection in
the mother. Bacterial conjunctivitis in other age groups is
most commonly caused by S .epidermidis or by S.pyogenes,
S. pneumoniae, H. influenzae, or Moraxella species.
Viral conjunctivitis is commonly caused by adenoviruses.
Both bacterial and viral conjunctivitis are highly contagious
46

47. INFECTIOUS KERATITIS :
(MICROBIAL KERATITIS)
• Infective Keratitis (microbial keratitis) is a major ophthalmic
problem often leading to corneal blindness.
• Keratitis is a more serious eye infection than conjunctivitis.
Invasion of deeper eye tissues occurs and can lead to complete corneal
destruction.
• Any microorganism can cause this condition, especially after
trauma to the eye.
• It can cause keratitis in the absence of predisposing trauma.
47

48. Cont..
• Clinical characteristics of bacterial keratitis caused by
individual bacteria are so much overlapping
• Bacteria by virtue of their toxins, adherence captivities,
invasiveness or strain differences in within a species may
produce different types of clinical picture.
• The variation in the clinical feature may be related to the
varying types of contact lenses used or with types of trauma or
previous scar in the cornea due to a virus infection.
48

49. Cont..
• In general Gram-positive bacteria tend to produce discrete,
small abscess like lesions whereas Gram-negative bacteria
produce diffuse rapidly spreading necrotic lesions.
• Patients with infectious corneal ulceration complain of pain,
watering, foreign body sensation reduces and reduced vision.
• Acute pain with watering and rapidly spreading corneal ulcer
is likely to be due to Pseudomonas aeruginosa and
Streptococcus penumoniae.
49

50. Cont..
• Indolent corneal ulcers may be caused by S.aureus or Moraxella
species. Gram-negative corneal ulcers produce marked eyelid
eodema and conjunctival chemosis.
• Hypopyon is commonly associated with corneal ulcers of any of
the aetiological origin, but is an important sign of Pneumococcal
or Pseudomonas ulcer.
• Hemorrhagic hypopyon is associated with pneumococcal or
Herpes simplex virus corneal ulcer.
50

51. Fungal Keratitis
• Corneal infection of fungal aetiology is very common
Aspergillus and Fusarium are responsible for 70 percent of
cases.
• These affect young, immunocompetent healthy adults, more
often from rural areas. A history of trauma with organic matter is
elicited in a significant percentage of cases.
• The ulcer commences insidiously and runs and indolent
course.
51

52. Cont…
• It begins at the mid-periphery of healthy cornea in the exposed
areas.
• The epithelium may show defect at the site of infiltration or
epithelial defect would have healed with deep stromal infiltrate
or endothelial plaque.
• The ulcer spreads towards the center of the cornea. Moderate
hypopyon or cheesy hypopyon is frequently noticed. In rare
cases one may see a haemorrhagic hypopyon.
• The ulcer base has a raised, wet, soft creamy to grayish-white
or yellowish-white infiltrate without mucous or
exudates.
52

53. Cont..• In advanced stages with involvement of the whole cornea the
typical clinical signs of fungal ulcer become obliterated.
• Satellite lesions and immune ring, which are infrequent, may assist
in diagnosing fungal ulcer.
• Endothelial plaque and posterior corneal abscess are seen more
frequently
53

54. Cont…
• In pigmented ulcers (chromomycosis) the brown, dark brown
or black pigment covering the ulcer base is the unique clinical
sign caused by pigmented fungi (dematiaceous).
• In some of these eyes the slough is dry, tough and leathery and
one usually needs a blade to remove it. These ulcers heal very
slowly
• Keratitis caused by Candida is extremely rarely seen and
should be differentiated from staphylococcal and Moraxella
ulcers.
54

55. Cont..
• Stromal herpes and other low virulent bacterial ulcers should
be considered in the differential diagnosis
• All these clinical features mentioned earlier may be masked or
altered by using native medicines, steroids or / and minor
surgical procedures
• Although fungal ulcers spread very slowly, corneal perforation
can occur within 5 to 6 days from the onset as in
Pseudomonas ulcer.
55

56. Acanthamoeba Keratitis
Parasitic infection is now reported with increasing frequency
though out the world. An amoeba called Acanthamoeba has been
causing serious keratitis cases, especially in people who wear
contact lenses
• Trauma with organic matter, exposure to muddy or brakish
water are the major predisposing factors.
• There is no marked difference in the symptom between
Acanthamoeba keratitis and fungal keratitis.
• Ring of stromal infiltration at mid-periphery of the cornea
without involving the pupillary area with intact gray or hazy
epithelium is noticed in a high percent of cases.
56

57. Cont…
• This free-living amoeba is everywhere—it lives in tap water,
freshwater lakes, and the like. The infections are usually
associated with less-than-rigorous contact lens hygiene, or
previous trauma to the eye
• A higher index of suspicion is the key to diagnosing
Acanthamoeba keratitis. Keratitis due to Herpes simplex,
atypical Mycobacteria and fungi should be thought of in the
differential diagnosis
57

58. Figure. Acanthamoeba infection of the eye.
58

59. Viral Keratitis
• Among the causative agents of viral keratitis, Herpes simplex
virus (HSV) infection is the most important one as it often
leads to blindness.
• Among the two types of HSV, type I is more commonly
associated with this condidtion. Type II virus keratitis if found
in 20 % of infants born with HSV infection.
• The usual cause of herpetic keratitis is a ―misdirected‖
reactivation of (oral) HSV-1. The virus, upon reactivation,
travels into the ophthalmic rather than the mandibular branch
of the trigeminal nerve.
59

60. Cont..
• HSV-2 can also occur as a result of a sexual encounter with the
virus or transfer of the virus from the genital to eye area or if an
individual has a recurrent oral infection with HSV-2.
• Preliminary symptoms are a gritty feeling in the eye,conjunctivitis,
sharp pain, and sensitivity to light. Some patients develop
characteristic branched or opaque corneal lesions as well
• .In 25% to 50% of cases, this keratitis is recurrent and chronic and
can interfere with vision. Blindness due to herpes is the leading
infectious cause of blindness in the United States
60

61. Cont..
• Various nonspecific stress factors, e.g., trauma, fever,
menstruation, psychological stress, climatic changes are
implicated as precipitating factors

62. HSV keratitis

63. Cont…
• The viral condition is treated with trifluridine or acyclovir
or both.
Geographic or Amoeboid Herpetic Ulcers :
Occasionally a linear dendritic figure progresses to a broad area
of epithelial involvement with irregular angulated borders
(―geographic‖ or ―amoeboid‖ ulcer).
These lesions have a much longer clinical course, often of many
months and often follow the injudicious use of topical
corticosteroids for the treatment of dendritic keratitis.
63

64. 64

65. Disciform Kerattis
• This is a central round (Disciform) lesion of the cornea, with
opacity and swelling of the corneal stroma.
• Disciform keratitis due to HSV is associated with marked
anaeshtesia and with keratic precipitates immediately beneath
the lesion on the corneal endothelium.
• It may also follow infections with vaccinia, herpes zoster,
mumps and varicella viruses but is most frequently associated
with HSV ocular infections.
65

66. Cont..
• It may run a course of a few weeks to several months.
• The milder cases tend to heal without sequel, but severe cases
sometimes progress to permanent stromal scarring.
66

67. Herpes Zoster Ophthalmicus; (HZO)
• It occurs due to activation of latent varicella zoster virus
infection which persists after primary varicella infection
• The most common findings are dendrites and punctate keratitis
• The zoster dendrite is more coarse, ropy and stellate, also the
terminal bulbs seen in simples dendrites are absent.
• They resolve without treatment within one month.
• Other findings in cases with corneal involvement in HZO are
puntate keratitis and mucous plaques
67

68. INFECTIOUS ENDOPHTHALMITIS ( BACTERIAL &
FUNGAL)
• Endophthalmitis refers to the inflammatory process that involves
the ocular cavity and adjacent structures.
• Infectious endophthalmitis is causes mainly by bacteria and
fungi. Viruses and parasites as causative agents are very rarely
implicated.
• Infectious endophthalmitis can be classified according to the
mode of entry, type of etiological agent and location in the eye.
68

69. Based on the mode of entry into the eye
A. Endophthalmitis is exogenous
when the microorganisms are introduced into the eye from the
environment.
 Endogenous infection is caused by the haematogenous
spread of organisms into the eye as a metastatic infection from
an infected site elsewhere in the body.
B. Endogenous endophthalmitis
 Occurs either following surgery (post-surgical or post-
operative endophthalmitis) or
 Trauma (post-traumatic endophthalmitis) or may involve the
intra-ocular contents in a generalized fashion.
69

70. • When the episclera participates significantly in the inflammatory
process, a panophthalmitis will be present .
Post-operative endophthalmitis
 The most common form of endophthalmitis accounting for
approximately 70% of infectious endophthalmitis.
 It may occur after any surgical procedure during which there
has been communication between the interior of the eye and the
external environment.
 The large majority of post-operative endophthalmitis
follows cataract surgery since it is the most common ophthalmic
surgical procedure performed.
70

71. Cont..
• Many potential sources of infection during surgery, the most
common is the periocular Normal flora of the patient.
• Around 75% of the conjunctival cultures from normal eyes
harbor S. epidermidis, S. aureus and various streptococci.
• The periocular flora normally gain access into the eye
during surgery.
• Additionally, an intraocular lens can become contaminated if it
touches the ocular surface or with the air of the operating room.
71

72. • Bacterial endophthalmitis, the most severe form of vision
threatening ocular infection may follow surgery, trauma,
bacterial keratitis or may be of endogenous origin.
• Several Gram positive and Gram negative bacteria including
anaerobic bacteria cause endophthalmitis.
• A rational therapy on the use of antibiotics and steroids
necessitates to determine whether the inflammation is
infectious or sterile.
Therefore, in such cases, an etiological diagnosis is necessary
72

73. 73

74. Chronic endophthalmitis
 is seen in patients who manifest the signs of inflammation late
but in whom all evidence indicates that the organisms
 The organisms commonly associated are the relatively less
virulent ones such as Propionibacterium acnes, S. epidermidis
and fungi
 The infective agents enter the eye long after surgery (during
the post-operative period) and develop endophthalmitis
rapidly.
 The patient must have some avenue for the source of infection
such as wound dehiscence or filtering bleb. The organisms
commonly associated are H. influenzae and Streptococcus spp.
74

75. Aetiological agents
• The most common organisms responsible for post-operative
endophthalmitis include mainly Gram positive bacteria followed
by Gram negative bacteria and fungi.
• Gram positive bacteria include S. epidermidis S. aureus, S.
pneumoniae, S. viridans and S.pyogenes.
• Gram negative bacteria isolated including Pseudomonas
aeruginosa is the most common and others such as Klebsiella
penumoniae, H. influenzae, E coli and Enterobacater aerogenes
.
75

76. • Post-operative fungal endophthalmitis is uncommon, but
many different fungi often considered saprophytes or
opportunistic pathogens (E.g. Cephalosporium Paecilomyces,
Candida, Aspergillus or Penicillum)
Bleb-induced endophthalmitis
• Patients with surgically produced filtering blebs for glaucoma
or blebs resulting inadvertently
• After intra-ocular surgery are susceptible to the development
of endophthalmitis months or years after surgery.
• Bacteria(such as Streptococcus spp. and H. influenzae )must
be capable of penetrating intact conjunctiva overlying filtering
blebs in order to enter the eye.
76

77. Post–traumatic endophthalmitis
• Endophthalmitis following penetrating eye injuries has a
relative poor prognosis.
• This is due to the underlying eye trauma and the
causation by more virulent bacteria such as Bacillus spp.
• Endophthalmitis occurring at a higher frequency in a rural as
compared to a non-rural setting is attributed to a hither
incidence of soil contamination in the rural areas.
• In addition to Bacillus spp, Gram positive cocci - both
Staphylococci and Streptococci are more common than Gram
negative bacilli and fungal isolates.
77

78. Cont..
• Posttraumatic endophthalmitis can also be cased by anaerobes,
commonly Clostridial species such as Clostridial species such
as C.perfringens.
• Fungal infections are higher in injuries with vegetable matter.
E.g. thorns, tree branches etc.
78

79. Endogenous endophthalmitis
 Most common responsible for endogenous endophtalmitis is
typical fungi such as C. stellatoidea and C. krusei. Aspergillus
spp. of second in frequency Next to Candida.
 Various other saprophytic, opportunistic and pathogenic fungi
including Sporothrix schenckii, Cryptococcus neoformans,
Coccidiodes immitis and Mucor have been reported in isolated
cases.
79

80. 80

81. Cont..
• Endogenous bacterial endophthalmitis is very rare. In
previously time , Neisseria meningitides accounted for
more common than S. pneumoniae and S. aureus.
• Now days, bacterial pathogens, especially Gram negative
bacilli (E. coli, Pseudomonas spp. and Proteus spp.) began to
occur more frequently.
81

82. OCULAR PARASITIC DISEASES
INTRAOCULAR PROTOZOAL INFECTIONS OF EYE
Toxoplasmosis : Caused by Toxoplasma gondii
 This protozoan has a life cycle in Cat : sexual life cycle
in the epithelium of intestine Man and other animals;
asexual life cycle in tissues including eye.
 Diagnosis is made by detecting antibodies to toxoplasma
in patients serum. Disease of the eye and brain can
occur as congenital infection.
82

83. HELMINTHIC INFECTIONS
Cysticercosis
 This is caused by Taenia solium which is tapeworm causing
intestinal infection of pig. Man passes egg in his faeces.
 These eggs ingested by pig larva is liberated in stomach
pass into the circulation and may lodge in muscles, meninges
and eye and form a cyst called cysticercus cellulosae.
 Man ingests infected pork and develops taeniasis with the
development of adult Taenia solium worm in the intestine
83

84. • The eggs may regurgitate in to the stomach from the intestine
and larva may be liberated in the stomach pass in to the
circulation and lodge in muscles, meninges and eye and form
cysticercus cellulosae.
• Man can also develop larval forms in his tissues.
• Diagnosed by histopathology examination of the biopsy tissue.
Serology by ELISA also can be used for diagnosis
84

85. Echinococcosis: Hydatid disease ; Caused by larva of
Echinococcus granulosus - dog tape worm.
 Larval form develops in man and ungulates - sheep, buffalo,
camel and deer .
 Egg (ovum) is liberated by adult tapeworm in the dogs
intestine and passed in the faeces. The egg, when ingested by
man or the ungulates hatch in the intestine, larva is liberated.
 Larva enters into circulation through intestinal wall and then
lodge in various organs including eye.
 Disease of eye often can be diagnosed by biopsy
85

86. Toxocariasis
• Round worm, Toxocara canis, normally occurs in the intestine
of pup
• The egg liberated is passed into the faeces. If man ingests this
egg, larva liberated from it, may pass into circulation and
lodge itself into any organ including eye.
• This migration of larva in the unnatural host often caused the
condition called larva migrans( Toxocariasis).
• Diagnosis is done by finding antibody in the serum against
Toxocara larval antigen
86

87. Other Parasitic diseases :
• Entamoeba histolytica, malarial parasite, larval stages of
filarial worm (Wuchereria bancrofti) and other helminths may
cause eye diseases.
• Diagnosis is made by detecting antibodies in patients serum.
Disease of the eye and brain can occur as congenital infection.
87

88. River Blindness
• River blindness is a chronic parasitic (helminthic)
infection. It is endemic in dozens of countries in Latin
America, Africa, Asia, and the Middle East.
• At any given time, approximately 37 million people are
infected with the worm called Onchocerca volvulus
• This organism is a flarial (threadlike) helminthic worm
transmitted by small biting vectors called black flies.
• These voracious flies often attack in large numbers, and it is
not uncommon in endemic areas to be bitten several hundred
times a day.
88

89. 89

90. • The disease gets its name from the habitat where these
flies are found, rural settlements along rivers bordered
with overhanging vegetation
• The Onchocerca larvae are deposited into a bite wound
and develop into adults in the immediate subcutaneous
tissues, disfiguring nodules form within 1 to 2 years after
initial contact.
• Microflariae given off by the adult female migrate via the
bloodstream to many locations but especially to the
eyes.
• While the worms are in the blood, they can be
transmitted to other feeding black flies
90

91. Cont..
• The condition was caused by degeneration of the worms
and the inflammation and granulomatous lesion
formation that result from the release of their antigens.
• It is in fact the case that the worms eventually invade the
entire eye, producing much inflammation and permanent
damage to the retina and optic nerve
• In 1999, researchers first discovered large colonies of
bacteria called Wolbachia living inside the Onchocerca
worms.
•
91

92. • There is convincing evidence that the damage caused
to human tissues is induced by the bacteria rather than by the
worms.
• Of course, the worms serve as the delivery system to
the human as it does not appear that the bacteria can infect
humans on their own.
• These bacteria enjoy a mutualistic relationship with their
hosts; they are essential for normal Onchocerca development
92

93. • In regions of high prevalence, it is not unusual for an
ophthalmologist to see microflariae wiggling in the anterior
chamber during a routine eye checkup.
• Microflariae die in several months, but adults can exist for up
to 15 years in skin nodules
• River blindness has been a serious problem in many areas of
Africa. In some villages, nearly half of the residents are
affected by the disease.
• A campaign to eradicate onchocerciasis is currently underway,
supported by the Carter Center, an organization run by former
U.S. President Jimmy Carter.
93

94. • The approach is to treat people with ivermectin, a
potent anti-flarial drug, and to use insecticides to
control the black flies. Eliminating the protozoan will
still eliminate the disease .
• The drug company that manufactures ivermectin has
promised to provide the drug for free for as long as
the need for it exists.
94

95. 95

96. References
• K. LILY THERESE and .N. MADHAVAN L .INTRODUCTION TO
OCULAR MICROBIOLOGY. MICROBIOLOGY RESEARCH CENTRE
VISION RESEARCH FOUNDATIONl8, COLLEGE ROAD, CHENNAI -
600 006.
• Cowan, M. Kelly. MICROBIOLOGY: A SYSTEMS APPROACH, THIRD
EDITION McGraw-Hill, a business unit of The McGraw-Hill Companies,
Inc., 1221 Avenue of the Americas, New York, NY 10020. 2012