Otitis media, Otitis externa , and Eye diseases:

Otitis media:

is the inflammation of the area between Eardrum

(Tympanic membrane) and the inner ear; including

Eustachian tube.-Infections of air-filled cavities of the head occur when normal drainage routes become obstructed.-Infection of air-filled cavities of the head results in: 1-Otitis media. 2-Sinusitis. 3-Mastoiditis.

N

-Because the cavity of the middle ear is contiguous with the

mastoid air cells(spaces of temporal bone); individuals

with

acute otitis media also have mastoiditis.

N

-The majority of cases occur in children between 6 and 36 months of age.-Children are susceptible to otitis media for several reasons: 1-The medial orifice of the eustachian tube is more open in infancy than later in life.2-Milk feeding (giving a bottle at bedtime) results in reflux of pharyngeal contents into the lumen of eustachian tube.

3-Eustachian tube is shorter and more horizontal in young children. 4-The viral infection of upper respiratory tract and lymphoid tissue results in eustachian tube obstruction.

Pathogenesis:

-Inflammation of upper respiratory tracts due to: 1-Viral infections; influenza A or B, and adenovirus. 2-Allergy (Rhinitis).-Swelling of lymphoid tissue (Eustachian tonsil)around eustachian tube.-Eustachian tube obstruction.-Absorption of air of middle ear slowly by surrounding tissues.-Creation of negative pressure (vacuum) in the middle ear.

-Accumulation of fluids ; so normal flora of upper respiratory tract could invade middle ear space.

N

-Colonization of middle ear cavity lining epithelium.-If the microbe has a polysaccharide capsule: -Polyclonal lymphocyte activator; cytokines production; chemotaxis of immune cells and inflammation.

-Conductive hearing loss.

-If the infection is not treated; otitis media and mastoiditis could be complicated by: 1-Facial nerve paralysis. 2-Infection of peripheral nerves; results in deeper brain abscess.

N

3-Infection of veins that bridge surrounding bony structures and the cerebral cortex; septic thrombophlebitis) results in subdural empyema (in some cases; related to epidural abscesses).

Acute abscess is frequently caused by a mixed bacterial flora

consisting of obligate and facultative anaerobic bacteria;

similar to the mixture of microbes infecting middle ear,

mastoid, and sinuses.

N

Treatment of poly-microbial brain abscesses:Antibiotic combination:1-Vancomycin or Ceftriaxone: to cover Staphylococci and other Gram positive beta-lactamase producers.

2-Metronidazole: to cover anaerobic bacteria.

3-Quinolones or Macrolides working effectively at acidic pH.

The Normal flora of upper respiratory tracts:

-Streptococcus pneumoniae (Nasopharynx).

-Haemophilus influenzae (non-type b) (Nasopharynx).

-Moraxella catarrhalis (Nasopharynx).

-Staphylococcus aureus.

-Coagulase negative Staphylococcus species.

-Diphtheroids species.

-Neisseriae species.

-Candida species.

Causes of Otitis media:

1-Streptococcus pneumoniae (the most common cause).2-Non-typeable Haemophilus influenzae. (the second common cause).-Both Strep. pneumoniae and H. influenzae causes 80% of otitis media cases.

3-Moraxella catarrhalis. -Gram’s negative non-motile coccobacilli in pairs. -Aerobic fastidious oxidase positive bacteria.

4-Other normal flora of upper respiratory tracts(rare).

Clinical Classification of Otitis media:

1-Acute suppurative:- Pus accumulated in middle ear; mainly in infant

and children.2-Chronic:

A-Recurrent OM due to other causes. B-Secretory OM : Very common persisting middle ear

effusion after OM in 40% of cases.( Thick fluid consistency .)

Management: 1-Amoxicillin or Ceftriaxone.

2-Amoxicillin/Clavulanate for Beta-Lactamases strains .

Otitis Externa :

Otitis Externa: is an inflammation of the outer ear and ear canal.

-It is mainly caused by bacterial or fungal agents.

-Otitis externa could be established due to:

1-Swimming in polluted water (germs contamination).

2-Impairment in the integrity of the skin (dermatitis).

-Hospital acquired otitis externa could be caused by

hospital dwelling bacteria as a post-surgical infection.

Causes of Otitis Externa:Exogenous:-Pseudomonas aeruginosa (the most common cause).

Endogenous: Normal flora of outer ear canal: -Coagulase negative Staphylococci. -Staphylococcus aureus. -Gram negative bacilli. -Fungi: Candida species. Malassezia furfur.

Clinical classification of Otitis Externa:

1-Acute localized secondary to folliculitis: -Painful pustule with local lymph node enlargement; Staphylococcus aureus.

2-Acute diffuse (Swimmer’s ear): -Pseudomonas aeruginosa. -Itchy, painful, edematous, reddened OE with purulent discharge.

3-Chronic OE secondary to chronic otitis media. -Fungi, Candida plus other chronic disease (Immunocompromised Pat. ).

N

4-Malignant OE (Necrotizing OE) Secondary to diabetic microangiopathy; Pseudomonas spp. -Serious infection. -Not-malignant (Non-Cancerous). -Malignant in its progressive, fatal course. -Spreading of infection to surrounding bone, blood vessels, facial nerve and meninges.

-Complicated by inflammation of cranial nerves and their

branches ; facial (7th) nerve paralysis.

-It is associated with immunocompromised patients. -Diagnosis: Full investigations: CT Scan, MRI.

N

Management:1-Acute: As OM.2-Acute diffuse: Local Neomycin, Polymyxin.3-Chronic: Local imidazole for fungi and treatment of OM.4-Malignant OE: I.V Tobramycin and Ceftazidime (weeks) With surgery.

Diagnosis:Clinical specimen: Ear Swab (cotton swab).

N

Culture: on Enriched media. -Blood agar incubated under aerobic conditions. -Chocolate agar: incubated under anaerobic conditions.

Isolation of Pseudomonas species:-Encapsulated, motile, Gram negative bacilli.-Oxidase positive , Exopigments production.-Antibiotic resistance strains. (greenish yellowish exopigment production; pyoverdin).

N

Isolation of Staphylococci:Staphylococcus aureus:Gram positive cocci, coagulase positive, novobiocin sensitive, and Mannitol fermenters.Other Staphylococci:Gram positive cocci, coagulase negative, novobiocin resistance.

Novobiocin sensitivity Mannitol fermentation.

Infectious diseases of the Eye:

Keratitis: inflammation of transparent eye’s cornea; the anterior part of the eye (covers the iris, and pupil).Causes:1-Amoebic keratitis: a serious corneal infection usually affecting contact lens wearers. Etiology: Acanthamoeba.2-Bacterial keratitis: Due to injury of wearing contact lenses. Etiology: Staphylococcus aureus, &Pseudomonas species.

N

Staphylococcus aureus is a major cause of infections of

the eyelid and cornea.

Staphylococcus aureus can infect the glands of the eyelid;

resulting in the production of a sty.

Sty is a painful red swelling

on the margin of the eyelid.

Treatment:

bacitracin ointment.

N

3-Fungal keratitis: Keratomycosis: Etiology: Fusarium species. -Infection is established due to corneal injury in agriculture workers or immunocompromised patients.

Fusarium Chlamydospores. Fusarium Macroconidia.

N

4-Viral Keratitis: Etiology: Herpes simplex virus types 1 and 2. Diseases: A-Primary infectious keratitis: Vesicular eruption of the eyelid, infection of cornea leading to corneal ulcers.

B-Recurrent herpes keratitis: -(More common than primary keratitis). -In immunocompromised patients. -Mild irritation and photophobia.

N

5-Onchocercal Keratitis: Onchocerciasis: -Parasitic infection of the eye’s cornea (Corneal lesions). -Etiology: Onchocerca volvulus. -Transmitted by the bite of blackfly. -Disease: African River blindness.

n

Chemotherapy for Keratitis and Corneal Ulcers:1-Bacterial Keratitis: Local broad-spectrum antibiotics; Vancomycin and tobramycin.

2-Viral keratitis: Acyclovir.

3-Fungal Keratitis: Amphotericin B.

4-Amoebic keratitis: Propamidine drops plus oral ketoconazole.

Conjunctivitis:

Conjunctiva: is a thin, translucent, mucous membrane that lines the eyelid and covers the white portion of the eyeball.

Conjunctivitis is divided according to etiology into:A-Bacterial conjunctivitis: -Redness, swelling of the eyelid, and muco-purulent discharge. - Yellowish-greyish discharge: pyogenic cocci infection. -Treatment: Local bacitracin or neomycin.

N

Types of bacterial conjunctivitis:1-Trachoma: Etiology: Chlamydia trachomatis:

Serotypes A, B, Ba, and C causes chronic

keratoconjunctivitis (Trachoma) that results in blindness.

Trachoma is a leading cause of blindness in endemic areas

of northern India, the Middle East, and North Africa. Transmission: -Personal contact ; eye-to-eye via droplets by contaminated hands (transfer of elementary bodies). Chemotherapy: Oral azithromycin or tetracycline.

N

Chlamydia trachomatis:-Unicellular obligatory intracellular bacteria that has rigid cell wall.

-Infective stage: The elementary body.

-Inclusion bodies (Trachoma) infected conjunctival epithelial cells (Reticulate body: diagnostic stage).

N

2-Ophthalmia neonatorum : Etiology:

1-Neisseria gonorrhoeae:- The most severe cause of

hyperacute bacterial conjunctivitis of newborn.

-It is acquired during passage of newborn through the birth canal of a mother infected by gonococci.

-Neisseria species are Gram negative oxidase positive

diplococci that ferment glucose only .

N

2-Chlamydia trachomatis:(Ophthalmia neonatorum): -This type of newborn conjunctivitis is associated with serotypes D-K. - 50% of Infants born with infection due to passage through the birth canal. - inclusion conjunctivitis heals without eye damage

-Treatment of both types 1 and 2: (Prophylactic drug):

Erythromycin ointment; most strains of Neisseria

gonorrhoeae are Beta-Lactam resistant.

N

B-Viral Conjunctivitis:(Pink Eye): diffuse pinkness of Conjunctiva.

- Adenovirus infection is the most common cause of viral conjunctivitis.

- Acute conjunctivitis, and pharyngoconjunctival fever.- A more serious infection is epidemic keratoconjunctivitis,

which involves formation of a painful ulcer of the corneal epithelium.

Electron microscopy:

Double-Stranded DNA, Icosahedral

naked virus.

N

-Herpes simplex virus cause serious Herpetic keratoconjunctivitis, which requires treatment with

acyclovir .-Acute hemorrhagic conjunctivitis is a highly

contagious disease caused by: 1-Enterovirus 70 .

2-Coxsackievirus A24 .

Viral hemorrhagic Conjunctivitis

due to Enterovirus-70

infection.

Diagnosis of Eye infection:Clinical specimens:

1-Eye cotton Swab.2-Conjunctival Scraping .

1-Direct microscopy: A-Swab for Microbiology (Gram’s stain ):

detection of G+ve and G-ve bacteria, and yeast . B-Conjunctival scrapes for cytology lab: detection of Chlamydia diagnostic stage.

C-Conjunctival Scrapes for immunohistochemistry : detection of viral infections or Chlamydia infection .

N

2-Detection of viral genetic material and Chlamydia genetic material by molecular methods:

1-Nucleic acid DNA hybridization.(Probe hybridization).

2-PCR : Primer amplification of genetic material .

3-Cultivation of bacterial agents:- Eye swab should be inoculated on Enriched media.

- Blood agar and Chocolate agar should be incubated under aerobic and anaerobic conditions respectively.

Clinical significance: isolation of pyogenic cocci and Neisseria gonorrhoeae .

Detection of Virus and Chlamydia genetic materials by Immunofluorescent Microscopy:

Detection of viral antigen by Localization of specific Adenovirus- monoclonal antibodies. Coxsackievirus receptor on

Epithelial cells of conjunctiva .