MIIM - Bacteria and Fungi Causing Ocular Infections IV - Week 3

Question 1

What gram stain, shape, and metabolic state is moraxella?

Answer 1

Gram negative diplococci
Strict aerobe

Question 2

Is moraxella oxidase and catalase positive or negative?

Answer 2

Positive for both

Question 3

Name the two major moraxella pathogens, and two conditions each they can cause.

Answer 3

Moraxella lacunata
-conjunctivitis
-keratitis

Moraxella catarrhalis
-acute conjunctivitis
-opportunistic infection (like endophthalmitis)

Question 4

Name 2 means of pathogenesis for moraxella.

Answer 4

Fimbriae mediate attachment
Lipopolysaccharides in the cell wall induces inflammation

Question 5

Name a source for each of the two major moraxella bacteria.

Answer 5

Moraxella catarrhalis - normal component of respiratory and ocular flora
Moraxella lacunata - also found as a commensal

Question 6

What is the ideal specimen for a suspected case of moraxella?

Answer 6

Discharge swab

Question 7

What antibiotics is moraxella resistant to (explain why), and what is the management for an infection?

Answer 7

Most isolates produce β-lactamase, and is resistant to penecillin and amoxycillin.
Amoxycillin-clavulanate or oral cephalosporins are used.
Susceptibility test beforehand is ideal.

Question 8

What gram stain, shape, and metabolic state are neisseria bacteria?

Answer 8

Gram negative diplococci
Aerobic

Question 9

Name the two major neisseria bacteria, and the systemic diseases they cause (3).

Answer 9

Neisseria meningitidis - meningiococcal disease
-meningitis and septicaemia
Neisseria gonnorhoeae - gonorrhoea

Question 10

How is gonorrhoea transmitted?

Answer 10

Sexually

Question 11

Are neisseria bacteria able to survive easily outside the body or are they fastidious?

Answer 11

They are fastidious

Question 12

Name two ocular diseases caused by neisseria gonorrhoea.

Answer 12

Adult conjunctivitis
Ophthalmia neonatorum

Question 13

What can prolonged untreated conjunctivitis lead to?

Answer 13

Keratitis

Question 14

Name 4 ways ophthalmia neonatorum can be prevented.

Answer 14

Screening pregnant women from high risk populations
-antibiotic treatment for those infected

Prophylactic treatment of newborns with ophthalmic ointments like tetracyclines or erythromycin - raises resistance concerns

Silver nitrate eye drops used at birth to prevent gonococcal eye infection

Question 15

Name one way chemical conjunctivitis can be induced?

Answer 15

Siver nitrate drops to prevent gonococcal eye infection

Question 16

Name 6 means of pathogenesis in neisseria.

Answer 16

-Able to penetrate the corneal epithelium without pre-existing defects
-Fimbriae attachement
-Variation in fimbrial proteins to counteract immune response
-Outer membrane proteins mediate invasion and survival in phagocytes
-Cell wall components, especially lipo-oligosaccharides, cause inflammation
-IgA protease

Question 17

Name a source of neisseria. Is it a part of the normal microbiota?

Answer 17

It spreads from contacts with gonorrhoea (sexually or poor hygiene).
It is not part of the normal microbiota.

Question 18

What two ideal specimen for a neisseria lab diagnosis? Elaborate.

Answer 18

A conunctival swab or corneal scraping. Must be transported quickly to the lab in an appropriate transport medium as it is fastidious.

Question 19

Is neisseria pyogenic?

Answer 19

Yes

Question 20

How can neisseria be cultured?

Answer 20

Using a culture of pus or scrapings on enriched media.
Antibiotics may sometimes be added to surpress the normal microbiota.

Question 21

Is neisseria oxidase positive?

Answer 21

Yes

Question 22

Name 4 ways neisseria infections can be managed.

Answer 22

-Penicillin course
-Resistance is common in urban areas - susceptibility tests are essential
-Empirical treatment depends on source of infection
-Treating associated STI essential

Question 23

Name three ways neisseria infections can be prevented.

Answer 23

Health education
Good hygiene
Effective diagnosis and treatment

Question 24

What bacteria is responsible for the most common STI?

Answer 24

Chlamydia trachomatis

Question 25

Does chlamydia trachomatis have a lipopolysaccharide membrane and peptidoglycan layer?

Answer 25

Has an outer lipopolysaccharide layer, but no peptidoglycan

Question 26

Describe the gram stain of chalmydia trachomatis. Elaborate on what is seen on a slide.

Answer 26

Technically it is gram negative, but is not seen in a stain, because of its size.

Question 27

Briefly describe the life cycle of chlamydiae (7).

Answer 27

-Elementary bodies attach by adhesins into mucosal epithelia. -EBs are endocytosed into inclusion, and doesnt fuse with a lysosome. -EBs transform into metabolically active reticulate bodies. -In cells with multiple inclusions, they fuse to form one. -Reticulate bodies multiply. -Reticulate bodies mature back into infectious EBs or persist in the cell as an aberrant body. -Newly matured EBs are released to infect other cells.

Question 28

What two diseases can chlamydia trachomatis cause, and what serovars?

Answer 28

Serovars A-C - trachoma Serovars D-K - inclusion conjunctivitis

Question 29

What chlamydia bacteria is associated with follicular conjunctivitis?

Answer 29

Chlamydophila psittaci - causes psittacosis, associated with follicular conjunctivitis

Question 30

What is the most common cause of preventable blindness worldwide?

Answer 30

Trachoma

Question 31

What conditions is trachoma most common in (5)?

Answer 31

Hot Dry Dusty Scarce water Poor sanitation

Question 32

Describe the progression of trachoma blindness beginning with repeated infection of the conjunctiva (9).

Answer 32

-Repeated infection of the conjunctiva -Lymphoid follicles and inflammatory infiltration -Eyelid scarring -Trichiasis -Entropion -Corneal abrasion -Scarring -Blindness

Question 33

Name three structures that are damaged with trichoma progression.

Answer 33

Goblet cell, lacrimal gland, and tear duct destruction.

Question 34

What lid defect does trachoma cause?

Answer 34

Defects in lid closure like trachiasis.

Question 35

Describe trachiasis.

Answer 35

Eyelashes are misdirected, and grow inwards towards the eye, rubbing on the cornea, conjunctiva, and inner lid surface, causing irritation.

Question 36

Describe entropion. Which eyelid does it usually affect, and which one is affected in trachoma?

Answer 36

It is the turning in of the edge of an eyelid, usually seen on the lower eyelid, but both are affected in trachoma. It causes the lashes and lid edge to rub against the eye.

Question 37

Briefly describe the lifecycle of chlamydiae (3).

Answer 37

Flies carry the bacteria onto eyes when feeding on discharge. Bacteria infects and spreads through direct contact. Flies breeding in human faeces spread the disease to others.

Question 38

Briefly describe how trachoma causes blindness (3).

Answer 38

The infection inflames and thickens the upper eyelid. The scarred eyelids turn inwards and rubs against the cornea. The lashes scratching the cornea continually leads to blindness.

Question 39

Name four symptoms of inclusion conjunctivitis in adults.

Answer 39

Scanty mucopurulent discharge Epithelial keratitis Marginal and central infiltrates

Question 40

Does corneal scarring and neovascularisation occur in inclusion conjunctivitis?

Answer 40

Yes

Question 41

Does inclusion conjunctivitis involve one or both eyes?

Answer 41

In adults, usually just one eye.

Question 42

What appearance does the lower eyelid have with inclusion conjunctivitis, and what are these structures?

Answer 42

The eyes are red, and the lower eyelid has many small red bumps, which are lymphoid follicles. This is called collicular conjunctivitis.

Question 43

In most cases, how does adult inclusion conjunctivitis spread? Name three additional ways.

Answer 43

Mostly caused due to the eye being exposed to infected genital secretions ( ͡° ͜ʖ ͡°) Water in swimming pools Contaminated hot tubs Sharing makeup

Question 44

Name 4 symptoms of neonatal inclusion conjunctivitis.

Answer 44

Eyelid oedema Hyperaemia Conjunctival infiltration Discharge

Question 45

If untreated, what does neonatal inclusion conjunctivitis lead to?

Answer 45

Blenorrhoea, which is excess mucus

Question 46

In what population of babies is neonatal inclusion conjunctivitis seen in?

Answer 46

Babies born vaginally to an asymptomatic (but infected) mother

Question 47

When does neonatal inclusion conjunctivitis present afterbirth?

Answer 47

5-19 days afterbirth

Question 48

Name three means of pathogenesis in chlamydiae.

Answer 48

Adhesins allowing colonisation of columnar epithelium Evasion of host immune responses by forming inclusions Inhibits apoptosis

Question 49

Define tropism.

Answer 49

Specificity towards a particular tissue

Question 50

What two specimens are ideal for a suspected chlamydia infection for lab diagnosis?

Answer 50

Conjunctival discharge or corneal scraping.

Question 51

What is seen on a gram stain of chlamydia (4)?

Answer 51

Lymphocytes Monocytes Macrophages Chlamydiais not seen

Question 52

What is seen on a giemsa stain of chlamydia?

Answer 52

Intracytoplasmic inclusions

Question 53

Name 2 detection methods for chlamydia.

Answer 53

Antigen detection by enzyme immunoassay - EIA Nucleic acid detection by PCR

Question 54

Name 3 means of management for chlamydia infection.

Answer 54

Long term antibiotic treatment due to antibiotics. Personal hygiene Contact tracing of STI

Question 55

What syndrome is C. trachomatis serovars D-K infection associated with?

Answer 55

Reiter's syndrome

Question 56

What is syphilis caused by?

Answer 56

The spirochaete - treponema pallidum

Question 57

When left untreated, name the three stages of syphilis.

Answer 57

Primary - painless chancre at the inoculation site Secondary - skin rashes, other organ involvement including ocular complications Tertiary - cardiovascular involvement and neurosyphilis

Question 58

Describe a chancre.

Answer 58

Fluid filled ulcer

Question 59

How can a definitive diagnosis for syphilis be made?

Answer 59

Lab diagnosis via a serology for antibody response.

Question 60

What percentage of those with syphilis will usually have ocular complications, and what is the most common complication?

Answer 60

10%, most commonly being uveitis.

Question 61

Which antibiotic is used to treat syphilis? Is resistance a problem?

Answer 61

Penicillin is used, which it typically doesnt resist. Reinfection can occur.

Question 62

Name 5 ocular conditions that can be caused by syphilis.

Answer 62

Keratitis Keratoconjunctivitis Orbital cellulitis Endophthalmitis Uveitis

Question 63

Describe keratitis.

Answer 63

Inflammation of the cornea.

Question 64

Describe two causes of non-infectious keratitis.

Answer 64

Minor injury or wearing contact lenses too long.

Question 65

Is infectious keratitis an emergency?

Answer 65

Yes, urgent referral is essential.

Question 66

List 7 symptoms keratitis.

Answer 66

Red eye Eye discomfort Photophobia Blurred or decreased vision Pain Vision loss Pus

Question 67

Name three risk factors of keratitis associated with contact lens wear.

Answer 67

Wearing them too long Poor disinfection Wearing them while swimming

Question 68

List 4 risk factors for keratitis (aside from those associated with contact lenses).

Answer 68

Reduced immunity (including corticosteroid use) Warm climate Previous eye injury Recent corneal disease

Question 69

Name 5 bacteria that can cause keratitis.

Answer 69

Staphylococcus aureus Streptococcus pneumoniae Pseudomonas aureginosa Enterobacteriaceae Moraxella

Question 70

Name three non-bacterial agents that can cause keratitis.

Answer 70

Fungi Parasites (like acanthomoeba) Viruses