Special Senses Microbiology: Eye & Ear Infections PDF

# Microtuorials: Special Senses ## **Eye and Ear Infections** ### **Special Senses Microbiology** #### ***Eye & Ear Infections*** ### **Normal Microbiota of the Eye** - Staph. epidermidis, Lactobacillus spp. & P. acnes ### ***Defense Mechanisms of the Eye*** - The eyelashes - The lids blink...

# Microtuorials: Special Senses ## **Eye and Ear Infections** ### **Special Senses Microbiology** #### ***Eye & Ear Infections*** ### **Normal Microbiota of the Eye** - Staph. epidermidis, Lactobacillus spp. & P. acnes ### ***Defense Mechanisms of the Eye*** - The eyelashes - The lids blink 15 to 20 times per minute - Secretions of the lacrimal glands and goblet cells wash away bacteria and foreign matter. - Lysozyme and immunoglobulin A (IgA) in tears ### **I- Lid Infections** **Etiology**: Staph. aureus **Types**: - Infection of lid margin: Plephritis - Infection of Lid glands & folliciles: Sties **C/P**: irritation, redness, burning sensation & itching ### **II- Conjunctivitis** **Etiology**: **Bacterial**: - Staphylococcus aureus - Streptococcus pneumoniae - Haemophilus influenzae - Moraxella species - N. gonorrhoeae and C. trachomatis **Viral**: - HSV-I & Adenovirus - Enterovirus & and Coxsackie virus A24 "Naked ss RNA viruses, Hgc conjunctivitis" - Systemic viral infection "Measels, mumps, rubella & Chicken pox - Covid-19 **Mode of transmission**: - Direct and indirect contact - Auto-inoculation from genital infection: n. gonorrhea & C. trachomatis "Via hand or fomites” ### **Clinical picture**: - Lacrimation - Red eye - Discharge - Watery: Viral - Purulent: Bacterial ### **Types of Conjunctivitis**: - HSV Conjunctivitis - Pharyngo-conjunctival fever (PCF) - Trachoma - Ophthalmia neonatorum ### **I- Herpes simplex virus-I Conjunctivitis** **Structure**: enveloped Ds DNA virus **Pathogenesis**: HSV-I: Latent infection in trigeminal ganglia & reactivates in immunosuppressed hosts. NB: HSV-2 can also cause neonatal conjunctivitis, but it's usually accompanied by generalized herpes ### **2- Pharyngo-conjunctival fever (PCF) "Adenovirus"** **Structure**: non-enveloped Ds DNA Viruses, has many serotypes, PCF infections mostly by type 3 **Disease**: Pharyngo-conjunctival fever or non-specific follicular conjunctivitis **MOT**: Use of inadequately chlorinated swimming pools and small lakes. ### **3- Opthalmia neonatorum** **Definition**: Conjunctivitis that occur in neonates acquired during the passage of infected birth canal **Etiology**: Usually bacterial - Chlamydia trachomatis "Mc" - Neisseria gonorrheae "2nd MC" - Staphylococcus aureus - Streptococcus pneumonia - HSV-2 **Prevention**: - Gonococcal infections: Erythromycin eye drops or ointment immediately after delivery - Chlamydial conjunctivitis: oral Erythromycin ### **4- Trachoma & inclusion conjunctivitis** **Etiology**: **Chlymidia**: non-motile coccoid bacteria - Obligate intracellular pathogen - Got rigid cell wall with group specefic LPS "Detected by complement fixation" & without peptidoglycan - Species: - C. trachomatis: * 15 immunotypes (A-L) according to specefic protein Ags detected by immunofluorescence • Types A, B, and C cause trachoma * Types D-K cause genital tract infections & can cause inclusion conjunctivitis via Auto-inoculation causing Inclusion conjunctivitis **Epidemiology & MOT**: - Trachoma is mostly found in developing countries in dry hot regions such as north Africa - C. trachomatis infects only humans and transmitted by finger-to-eye or fomite-to-eye contact. **Chlymedia replication cycle**: - Extracellular, metabolically, inert "spore-like " elementary body enters the cell and transforms into a larger, metabolically active reticulate body. - Reticulate body undergoes repeated cycles of binary fission to form daughter reticulate bodies - Reticulate bodies develop into Elemntary bodies - site of replication within the cell appears as an inclusion bodies "IBs” - IBs can be stained and visualized microscopically = useful in the identification of these organisms in lab diagnosis **Notes**: ### **Pathogenesis**: - Chlamydiae infect primarily epithelial cells of the mucous membranes. - The pathogen multiplies in cells of the conjunctiva and kills them, triggering a large amount of purulent (pus-filled) discharge scarring the conjunctiva - Such scarring in turn causes the patient's eyelids to turn inward “Trichiasis" - eyelashes scratch, irritate, and scar the cornea causing corneal opacity and blindness **NB**: Reiter's syndrome: Autoimmune reaction by Antibodies formed against chlymedia, composed of the classic triad of Urethritis, Arthritis & uveitis ### **Clinical picture**: - First clinical signs are mild conjunctival inflammation & discharge - infiltration of lymphocytes and MQs into the infected area makes the inner aspect of the upper eyelid pebbled "rogh” - Chronic and repeated infections causes scarring and trachiasis = corneal irritation and damage - In inclusion conjunctivitis “Auto-infection or infants born to infected mothers”, discharge is mucopurulent and it usually affects the lower lid | = no corneal affection and recovery is the rule ### **Diagnosis**: - In endemic areas: Clinical diagnosis **Lab diagnosis**: Mostly used in reseach: - PCR "NAATS" : best techniqe to confirm occular C. trachomaitis infections - Ag detection by ELISA or DIF - Isoaltion on tissue culture and detection of - Cytoplasmic IBs: by Giemsa stain - Glycogen filled inclusions by iodine stain - Serology: Not used to diagnose trachoma in egypt as infection rate is so high ### **Prevention** - Sexually transmitted C. trachomatis: prompt treatment of both the patient and the sexual partners - Oral erythromycin given to newborn infants of infected mothers can prevent inclusion conjunctivitis and pneumonitis caused by C. trachomatis. - No vaccine ### **Treament** - Eye infections in adults: oral tetracycline, doxycycline, or erythromycin for 3 to 6 Weeks - Eye infections in newborns: tetracycline or erythromycin cream for 10-14 days - Surgical correction of eyelid deformities: prevents corneal scratching, scarring, and blindness ### **III- Keratitis** **Infection of the cornea, usually follows some type of trauma to the ocular surface.** **Etiology** **Bacterial**: - Staphylococcus aureus - Streptococcus pneumoniae - P. aeruginosa **Viral**: - HSV-I - Adenovirus - Varicella zoster Virus "VZV" **Fungal** - Fusarium solani **Clinical picture**: - Symptoms of corneal irritation: Pain, Lacrimatiom & Photophobia "PLP" - Gritty feeling in the eye - C/P of the cause: Dendritic branching ulcer in HSV, Vesicles is VZV ### **I- Herpes simplex virus-I keratitis** **Structure**: enveloped Ds DNA virus **Pathogenesis**: HSV-I: Latent infection in trigeminal ganglia & reactivates in immunosuppressed hosts. causing dendritic branching ulcer, Repeated infections = scarring and blindness **Treatment**: Topical & oral Acyclovir ### **2- Epidemic keratoconjunctivitis (EKC), "Adenovirus 8 & 19"** **Structure**: non-enveloped Ds DNA Viruses, EKC by type 8 & 19 **Disease**: Epidemic Kerato-Conjunctivitis (EKC), the most serious form of adenoviral eye infections **MOT**: Close personal contact & Eye examination with non sterile ophthalmic instruments ### **3- Herpes Zoster Ophthalmicus "VZV"** **Pathogenesis**: VZV: Latent infection in trigeminal ganglia & reactivates in immunosuppressed hosts. causing hz ophthalmicus "Unilateral painful vesicles + Keratits, conjunctivitis & iritis **Treatment**: Oral Acyclovir only ### **General Charachtaristics of important bacterial agents** ### **1- Staph. aureus** - Gram +ve cocci in groups, catalase +ve - Coagulase +ve - beta hemolytic on blood agar - Mannitol fermenter on Mannitol salt agar - Golden yellow colonies on Nutrient agar **VFs**: Coagulase "free and bound" # fibrinogen fibrin Staph. Protein A: Binds to Fc of the IgG antibody stopping it's action aureus capsule: Antiphagocytic and Anti complement e ẞ lactam "Penicillin" ### **2- Streptococcus pneumoniae:** - Gram +ve cocci in pairs, catalase -ve - Alpha hemolytic on blood agar - Optichin & bile sensitive **VFs**: capsule: Antiphagocytic and Anti complement Toxins P-V Alpha toxin "Hemolytic exotoxin" Capsule IgA-l protease: breaks down secreatory IgA in secretions ### **3- H. influenzae:** - Small gram -ve coccobacilli “rods” - isolation of the organism on laboratory media requires the addition of two components: factor X & factor V ### **4- N. gonorrhea "Gonococci"** - Gram-negative "kidney-bean shaped" diplococci - Oxidase-positive **VFs**: MQ Receptors X Receptors مر Pill IgA A IgA IgA Protease IgA protease ### **5- Pseudomonas aeruginosa** - Gram -ve bacilli "rods", Aerobic - Oxidase +ve, non lactose fermenter - Produce blue - green exopigment on nutrient agar "pyocyanin & Pyoverdine" **VFs**: Capsule MQ Xx Exotoxin A: (inactivates Elongation Factor -2) = inhibits Pt synthesis ### **Infections of the deeper layers of the eyes** **Infection can occur through traumatic injury or via blood** **Examples:** - Opportunistic infection by Pseudomonas aeruginosa - In utero infections of Rubella and Cytomegalovirus (CMV)causing cataract, microphthalmia and severe chorioretinitis - CMV causes severe chorioretinitis in AIDS patients - Ocular complications of West Nile virus infection and Rift Valley virus infection ### **Diagnosis of Eve Infections** **Specimen**: conjunctival swab or corneal scrapings - Blood and chocolate agar plates should be inoculated and incubated under 5% to 10% CO2. Isolated colonies are identified by Gram stained films and biochemical tests. - For viral infection: PCR for the suspected virus. ### **Infections of the Ear** ### **Otitis Externa (External Ear Infections** - Otitis externa is similar to skin and soft tissue infection. - Acute localized disease occurs in the form of a pustule or furuncle and typically is caused by Staphylococcus aureus. - Acute diffuse otitis externa (swimmer's ear) is related to maceration (softening of tissue) of the ear from swimming or hot, humid weather. Gram-negative bacilli, particularly Pseudomonas aeruginosa, play an important role. - Malignant otitis externa is a necrotizing infection that spreads to adjacent areas of soft tissue, cartilage, and bone. P. aeruginosa, in particular, and anaerobes are frequently associated with this process. This condition is seen in patients with diabetes. ### **Acute Otitis Media** - An acute Infection of the middle ear, caused mainly by: **Bacterial pathogens:** - S.pneumoniae (most common), H. influenzae, Moraxella catarrhalis. **Viral pathogens:** - Respiratory syncytial virus: The virus belongs to paramyxovirus. They have unsegmented (-) sense/ ssRNA. - Coronaviruses (CoVs): They are enveloped (+) sense/ ssRNA viruses. They have the largest genomes of any RNA virus. They have helical nucleocapsid. - Rhinoviruses: The most common cause. They belong to Picorna viruses. They are small non-enveloped (+) sense/ ssRNA viruses. There are several serotypes. They replicate better at 33°C than at 37°C (infection is limited to the mucosa of the the upper respiratory tract and conjunctiva). ### **Laboratory Diagnosis** - Mainly clinical - Culture of discharge - Needle aspiration of middle ear fluid ### **Treatment** - Antimicrobials - Follow up is important, as residual fluid may lead to chronicity, resulting in hearing impairment