Download Causes of Otitis media

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).
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.
N
-Necrotizing otitis externa is a form of infection in
immunocompromised patients.
-This type of infection could be complicated by
inflammation of cranial nerves and their branches
; facial nerve paralysis.
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.
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.
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).
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:
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
monoclonal antibodies.
Epithelial cells of conjunctiva.
Localization of specific AdenovirusCoxsackievirus receptor on