Bacterial Eye Infections Lecture Notes

BACTERIAL INFECTIONS OF THE EYE Department of Medical Microbiology OBJECTIVES / OUTCOME By the end of the lecture, the learner should be able to  Describe the aetiology, clinical features, differential diagnosis, laboratory diagnosis, treatment and prevention for the following conditions:  Blephar...

BACTERIAL INFECTIONS OF THE EYE Department of Medical Microbiology OBJECTIVES / OUTCOME By the end of the lecture, the learner should be able to  Describe the aetiology, clinical features, differential diagnosis, laboratory diagnosis, treatment and prevention for the following conditions:  Blepharitis  Eyelid abscess  Dacrocystitis  Canaliculitis  Cellulitis  Conjunctivitis  Ophthalmia neonatorum  Trachoma  Keratitis BLEPHARITIS Definition: Blepharitis is inflammation of the margins of the eyelids Anterior  Occurs at the outside front edge where eyelashes attach  Most commonly caused by bacteria (Staphylococcus blepharitis) or dandruff of the scalp and eyebrows (seborrheic blepharitis) Posterior  Affects the inner edge of the eyelid that comes in to contact with eyeball. Caused by irregular oil production by glands of the eyelids which creates favorable environment for bacterial growth STAPHYLOCOCCAL ANTERIOR BLEPHARITIS Symptoms  Burning, grittiness & mild photophobia with remissions & exacerbations. Worse in the mornings Signs:  Hard scales and crusting around base of lashes  Papillary conjunctivitis & chronic conjunctival hyperaemia  Scarring & notching  Secondary changes: Sty formation, marginal keratitis  Associated tear film instability & dry eye ANTERIOR BLEPHARITIS MANAGEMENT OF ANTERIOR BLEPHARITIS Eyelid hygiene:  Daily removal of crusts: scrubbing of the lid with a cotton bud dipped in a dilute solution of baby shampoo/sodium bicarbonate Antibiotics:  Topical: Fusidic acid, bacitracin/chloramphenicol for acute folliculitis, limited value in long standing cases  Oral: Azithromycin may be helpful to control ulcerative lid margin disease  Antibiotic preparations are of limited value in chronic, longstanding cases Weak topical corticosteroid Tear substitutes:  To correct the disturbance of the stability of the tear film EYELID ABSCESS (HORDEOLUM) Definition: These are localised swellings of the eyelids. May be internal or external Usually a pyogenic infection or abscess caused by Staphylococcus aureus a) Internal Hordeolum: rare, results from infection of a Meibomian gland b) External Hordeolum (sty): results from obstruction and infection of eyelash follicle and adjacent glands of Zeis and Moll. More common in children & young adults INTERNAL HORDEOLUM EXTERNAL HORDEOLUM MANAGEMENT OF HORDEOLUM Internal hordeolum Hot compresses on the eye PLUS oral antibiotic Remaining nodule (if any) remove surgically (done by an ophthalmologist!!) External hordeolum Hot compress (increase the blood supply to the inflamed area & may aid in spontaneous draining of the abscess) Epilating eyelash associated with the infected hair follicle will hasten resolution Topical antibiotics DACROCYSTITIS Definition: Nasolacrimal  Inflammation of the lacrimal duct obstruction sac (cyst)  Usually secondary to obstruction of the nasolacrimal duct  It may be acute or chronic Aetiology:  Most commonly due to Staphylococcal / Streptococcal infections ACUTE DACROCYSTITIS Clinical features:  Acute dacrocystitis presents with subacute pain  Redness & swelling of the medial canthus & epiphora  Very tender, red & tense swelling at the medial canthus, may be associated with preseptal cellulitis  Abscess formation in severe cases DACRYOCYSTITIS ACUTE DACROCYSTITIS Treatment:  Hot compress & oral antibiotics like flucloxacillin or amoxicillin/clavulanate  NB: Irrigation & probing should not be performed  Incision & drainage may be considered if pus points and the abscess is about to drain spontaneously (risk of a lacrimal fistula)  Surgical CANALICULITIS Definition & cause:  Canaliculitis is inflammation of the ‘little canals leading from lacrimal puncta to the lacrimal sac  Chronic canaliculitis is an unusual/rare condition  Often caused by Actinomyces  Actinomyces are Gram positive, filamentous bacteria which grow under anaerobic conditions  Obstruction of the canaliculus (lacrimal duct from the lacrimal sac to the eye) may promote growth of anaerobic bacteria – although no identifiable predisposing factor in most cases CANALICULITIS Clinical Features  Unilateral epiphora (overflowing of tears) associated with chronic mucopurulent conjunctivitis refractory to conventional treatment  Gram stain & culture of expressed pus confirms diagnosis Treatment  Topical antibiotics (Ciprofloxacin) – rarely curative  Canaliculotomy involving a linear incision into the conjuctival side of the canaliculus is most effective  Occasionally it may result in scarring & interference with canalicular function PERI-ORBITAL CELLULITIS  Bacterial orbital cellulitis is a life-threatening infection of the soft tissue behind the orbital septum PATHOGENESIS  Sinus related: most commonly ethmoidal, typically affects children & young adults  Extension of preseptal cellulitis: through the orbital septum  Can occur at any age but is more common in children  Most common causative organisms are:  Staphylococcus aureus  Streptococcus pyogenes  Local spread: from adjacent dacrocystitis, mid facial & dental infection  Haematogenous spread  Post-traumatic: develops within 72 hours of injury that penetrates the orbital septum, clinical features may be masked by associated laceration/haematoma  Post-surgical: may complicate retinal, lacrimal or orbital surgery CELLULITIS PERI-ORBITAL CELLULITIS: DIAGNOSIS:  Presentation  Rapid onset of severe malaise, fever, pain & visual impairment COMPLICATIONS  Ocular  Signs  Intracranial (Rare)  Unilateral, tender, warm & red periorbital oedema  Proptosis: often obscured by lid swelling  Painful ophthalmoplegia  Optic nerve dysfunction  CT  Shows preseptal & orbital opacification  Exposure of keratopathy, raised intraocular pressure, occlusion of the central retinal artery/vein, endophthalmitis &optic neuropathy  Meningitis, brain abscess, cavernous sinus thrombosis  Superosteal abscess  Frequently located along the medial orbital wall – may potentially extend intracranially  Orbital abscess  Relatively rare in sinus related orbital cellulitis  May occur in post-traumatic /postoperative cases PERI-ORBITAL CELLULITIS Treatment:  Hospital admission:  With frequent ophthalmic & ENT assessment: mandatory  Intracranial abscess formation: necessitates drainage  Antibiotic therapy  Surgical intervention, should be considered:  Unresponsiveness to antibiotics BACTERIAL CONJUNCTIVITIS Conjunctivitis may have several causes like trauma/injuries, allergic reactions, emphasis is placed on bacterial conjunctivitis in this lecture Bilateral involvement can usually be attributed to allergies, while infectious conjunctivitis frequently begins in one eye & spreads to the other eye within a few days Bacterial & viral infections are the most common causes of infectious conjunctivitis BACTERIAL CONJUNCTIVITIS Causes: Bacteria most commonly involved in infectious conjunctivitis (especially adults): 1) Haemophilus influenzae 2) Streptococcus pneumoniae 3) Staphylococcus aureus 4) Moraxella catarrhalis 5) Neisseria gonorrhoeae 6) Chlamydia trachomatis BACTERIAL CONJUNCTIVITIS BACTERIAL CONJUNCTIVITIS Symptoms:  Acute onset of redness, grittiness, burning & discharge  Involvement is usually bilateral although one eye may become affected 1-2 days before the other  On waking the eyelids are frequently stuck together and are difficult to open spontaneously Signs:  Diffuse conjunctival injection & intense papillary reaction over the tarsal plates  Discharge is initially watery, mimicking viral conjunctivitis later becomes mucopurulent OPHTHALMIA NEONATORUM Pathogenesis:  These infections are usually contracted from an infected maternal birth canal when the mother is carrying a sexually transmitted pathogen, i.e. Chlamydia, Gonorrhoea, genital herpes  Occasionally colonised/infected with S. aureus from the vaginal tract Definition:  Ophthalmia neonatorum/neonatal conjunctivitis develops within 2-3 weeks of birth  Serious condition as no immunity in infant & immaturity of the ocular surface (No lymphoid tissue & poor tear film) Caused by: 1) Neisseria gonorrhoeae 2) Chlamydia trachomatis 3) Other occasional pathogens include: S. aureus, S. pneumoniae, H. influenzae, Enterobacterales OPHTHALMIA NEONATORUM Neisseria gonorrhoeae  Gonorrhoea is a venereal genitourinary tract infection caused by N. gonorrhoeae which is capable of invading the intact corneal epithelium  Most serious cause of bacterial ophthalmia neonatorum Symptoms: Acute, profuse, conjunctivital discharge, usually within first 7 days of birth, frequently bilateral OPHTHALMIA NEONATORUM Neisseria gonorrhoeae Laboratory investigations:  Take a swab for M, C & S  Take directly to the laboratory  Gram stain shows Gram-negative, kidney-shaped diplococci  Culture on enriched media such as chocolate agar or Thayer-Martin medium Gram stain showing inflammatory cells/ pus cells and Gram negative diplococci OPHTHALMIA NEONATORUM Neisseria gonorrhoeae TREATMENT:  Recommended regimen Ceftriaxone 25-30 mg/kg IV or IM in a single dose (not to exceed 125 mg)  Topical antibiotic therapy alone is inadequate and is supplementary to systemic treatment administered OPHTHALMIA NEONATORUM Chlamydia trachomatis  This type of neonatal conjunctivitis usually presents between five and ten days post partum  Initially unilateral conjunctival hyperaemia (redness) with severe oedema of the eyelids and a profuse purulent discharge  Because new-born babies do not have lymphoid tissue in the conjunctiva, they do not develop the typical acute follicular conjunctivitis that is characteristic of Chlamydia infection in adults OPHTHALMIA NEONATORUM Chlamydia trachomatis Laboratory investigations: Specimen: special swab for PCR Tests done: Immunofluorescence or PCR Urgent treatment is indicated in association with paediatrician Infection is treated with oral erythromycin for 2 weeks Topical Erythromycin/Tetracycline ointment is used in addition but not as sole therapy 1% silver nitrate in the baby’s eyes directly after birth, does not provide effective protection against Chlamydia trachomatis conjunctivitis in neonates ADULT CHLAMYDIAL CONJUNCTIVITIS  Chlamydia trachomatis is a small, obligate intracellular bacterium  Sexually transmitted Also responsible for 2 ocular syndromes in adults:  Inclusion conjunctivitis (Acute follicular conjunctivitis)  Serotypes D-K of C. trachomatis  Transmission is by autoinoculation from genital secretions (eye-to-eye may account for 10% of cases)  Incubation period is about 1 week  In addition to conjunctival follicles, the lower eyelid is mostly involved and pre-auricular adenopathy is a common sign  Ocular trachoma TRACHOMA Epidemiology:  Trachoma is chronic follicular kerato-conjunctivitis caused by infection with serotypes A, B, Ba & C of Chlamydia trachomatis  Initial infection is self-limiting & resolves without scarring  Repeated infection, particularly if associated with bacterial conjunctivitis, can lead to blindness  Associated with poverty, overcrowding & poor hygiene  Major cause of blindness, especially in underdeveloped regions like: Africa & Asia where poor hygienic standards promote spread of the infection by means of direct contact between people WHO: SAFE STRATEGY  The current effort to target trachoma headed by the WHO & the Alliance for the Global Elimination of Trachoma by 2020 is called SAFE: S – Surgery for trachoma trichiasis A – Antibiotics for active disease F – Face washing E – Environment improvement BACTERIAL KERATITIS INFECTIOUS CAUSES OF KERATITIS  Bacterial  Viral  Fungal  Parasites RISK FACTORS Contact lens wear Most important risk factor  Particularly soft lenses worn overnight  Pseudomonas spp. account for over 60%  Infections are more likely if there is poor lens hygiene  Bacteria may multiply in the contact lens case where they are protected from disinfection by bacterial biofilm  Corneal epithelium compromised by hypoxia & trauma is also susceptible to infection  A diagnosis of bacterial keratitis must be considered in any contact lens user with an acutely painful red eye RISK FACTORS Trauma Accidental injury - developing countries agricultural injury is a major risk factor Surgical (refractive surgery) and loose sutures Ocular surface disease Such as herpetic keratitis, bullous keratopathy, dry eye, chronic blepharitis, exposure, severe allergic eye disease & corneal anaesthesia Other Topical/systemic immune suppression, diabetes, vitamin A deficiency & measles BACTERIAL KERATITIS  Bacterial keratitis is very uncommon in a normal eye  Some bacteria that can penetrate a normal corneal epithelium  The virulence of the organism & the anatomic site of the infection determine the pattern of disease The most common pathogens are: 1) Pseudomonas aeruginosa 2) Staphylococcus aureus 3) Streptococcus pyogenes 4) Streptococcus pneumoniae BACTERIAL KERATITIS MANAGEMENT Bacterial keratitis has the potential to progress rapidly to corneal perforation  Even small axial lesions can cause surface irregularity & scars and can lead to significant vision loss TREATMENT PRINCIPLES  Decision to treat: Based on clinical grounds, causative organisms cannot be guessed reliably from the appearance of the ulcer. Treatment should be initiated even if Gram stain is negative and before the result of the culture is available  Topical: Can achieve high tissue concentration and initially should involve broad spectrum antibiotic to cover most common pathogens TUBERCULOSIS  Caused by Mycobacterium tuberculosis a notifiable disease  Organism discovered by Robert Koch: 1882  Grows slowly  Disease in highly oxygenated tissue e.g. apex of lungs, kidney  Resistant to dehydration TRANSMISSION  Person to person spread: respiratory aerosols  Initial site: lung  Reticulo-endothelial cells e.g. macrophages  Humans natural reservoir  Most clinical tuberculosis due to reactivation  Risk factors: Low socio-economic Poor housing Poor nutrition Immuno-compromised TUBERCULOSIS Stages: Primary First exposure with infection May progress or it may become latent Latent May be dormant for many years Secondary = reactivation Reactivation of latent bacilli in site of infection with replication Results in caseous necrosis and tissue destruction Tuberculosis - Diagnosis Sputum testing - as lungs are commonest site (pulmonary TB) for reactivation in adults and older children Young children are more likely to have infections in other sites (disseminated TB) Skin tests (Mantoux) can only be used for diagnosis in children in SA >15mm active disease = treat Treatment = 4 drug fixed dose combinations (rifampicin, isoniazid, pyrazinamide, ethambutol) 41 LABORATORY TESTS Smears Ziehl-Neelsen stain (ZN) for acid-fast bacilli Fluorochrome stains e.g. Auramine O Cultures Solid Liquid media Molecular diagnostics GeneXpert Rapid INH and RIF susceptibility 42 ACID FAST STAINS AURAMINE STAIN 43 TB CHORIORETINITIS Normal fundus 44 TUBERCULOSIS Ocular features  Eyelid lesions  Conjunctivitis is uncommon  Keratitis phlyctenular or interstitial scleritis is rare  Anterior uveitis  Granulomatous focal or multifocal choroiditis or diffuse occlusive retinal periphlebitis  Neuro-ophthalmic diseases  Pupillary abnormalities  Optic neuropathy  Ocular motor palsy Effect of TB treatment Ethambutol Bacteriostatic  Part of fixed drug combination  Also used for MDR TB therapy Adverse effects on eye:  Bilateral blurry vision  Impaired visual acuity  Red/green colour vision disturbances  Recommend colour testing monthly esp. those on MDR regimens Thank You