Ophthalmic Medical Microbiology - Unit 3, Part 2 PDF

**[Unit 3: Part 2: Ophthalmic Medical Microbiology: Microbiology of Anterior Segment Eye]** - Certain microbes that are present in the body elsewhere may cause infection in the cornea when they may not in other parts of the body - Approx 50% of ocular samples come back with micro-organisms...

**[Unit 3: Part 2: Ophthalmic Medical Microbiology: Microbiology of Anterior Segment Eye]** - Certain microbes that are present in the body elsewhere may cause infection in the cornea when they may not in other parts of the body - Approx 50% of ocular samples come back with micro-organisms - Lids have the larger number of micro-organisms compared to conjunctiva - Cornea + AC are thought to be sterile **[MOST COMMON BACTERIA FOUND IN LID + CONJUNCTIVA]**: gram-positive, coagulase (enzyme) negative (inability to form thrombus) - Staphyolococci - Corynebacterium - Propinibacterium Other isolates include**[:]** - Staph. Aureus - Micrococcus - Bacillus - Bacteriodes Gram-negative micro-organisms: less than 5% of cases and they tend to be present as transient micro-organisms rather than persistent colonisers in healthy eyes *At birth the bacterial spectrum in a bit different but overall becomes adult-like within 5 days (during childhood however they is a more frequent streptococcal colonisation)*: - Lactobacaillus - Bifidobacterium - Preptococcus - Corynebacterium - Coagulase negative staphylococcus **[FUNGAL COLLONISATION IN EYES]**: more rarely isolated: -eyelids: 2-52% -conjunctiva: 2-37% - Number and frequency of gram-positive bacteria increases with sleep - Following foreign body removal + patching, prophylactic antibiotics should be given as precaution **[OBTAINING A SAMPLE]**: for a corneal infection 1. *Direct scraping* of the corneal ulcer to provide smears + cultures: insertion of unpreserved single use topical anaesthetics. Unpreserved anaesthetics are preferred as to reduce the microbicidal effects of preservatives - The base and leading edge of the ulcer are scraped using a platinum spatula/surgical - The material is spread onto a clean glass slide and AIR DRIED - The slide is then stained - Subsequent scrapes are inoculated on to solid or liquid media 2. **SEVERE CASES**: corneal biopsy 3. **Acanthamoeba and fungal investigations**: in vivo confocal microscopy (non-invasive imaging technique) 4. *Px brings the contact lens in*: - AGAR SANDWICH TECHNIQUE: contact lens is immersed into hot agar and bacteria upon the contact lens is released - LENS MACERATION TECHNIQUE: **[OBTAINING A SAMPLE FOR VIRAL INFECTION]**: 1. Direct examination of tissue scrapes 2. Cell culture to isolate causative organisms 3. PCR testing -- specific target sequences of microbial DNA are amplified (e.g. used in herpetic disease) **[OBTAINING A SAMPLE FOR A RANGE OF MICRO-ORGANISMS]**: - Southern Blotting - Random amplification of polymorphic DNA - Mitochondrial DNA fingerprinting by restriction fragment length polymorphism **[ROUTINE LAB PROTOCOL]**: - Direct microscopy of samples carried out - Appropriate bacteria culture is inoculated with the bacterial sample and incubated at 37 degrees for 24-48 hours (may change according to bacteria type) - Culture plates are examined at 24 hours and 48 hours of incubation - Significant bacterial growth will then lead to antibiotic sensitivity tests with evaluation after further 24 hours **[STAINING FOR MICROSCOPY]**: GRAM STAIN: 1^st^ major identifier of bacterial identification 1. Fix material on to microscope slide with heat/alcohol treatemt 2. Stain with crystal violet for 2 mins 3. Wash off with water 4. Treat with iodine for 2 mins 5. Wash off with water 6. Decolourise the slide with acetone/alcohol for 5 seconds 7. Wash off with water 8. Counterstain with neutral red, sarfranine or dilute carbol fuschin 9. Wash off with water, dry and apply coverstrip 10. Apply immersion oil and observe under 100x oil immersion objective **[RESULTS OF GRAM STAIN]**: - BLUE -- gram positive and yeast - RED -- gram negative, connective tissues and cells - Fungal hyphae have a variable stain OTHER STAINING TECHNIQUES: 1. **Giemsa Stain**: cytological testing: examining cells/tissue for diseases 2. **Zeil-Neelsen Stain**: used to demonstrate acid-fast bacteria (resist acid decolourisation) esp mycobacteria 3. **Fluorescent Dyes**: rhodamine and fluorescein -- can demonstrate presence of bacteria, fungi and viruses. Specimens are viewed under a fluorescent microscope 4. **Immuno-peroxidase**: used to determine if acanthamoeba is present **[Culturing Micro-Organisms]**: routinely 37 degrees used, however can differ organism to organism - PSYCHROPHILES (cold-loving organisms): \45 degrees **[Gaseous Requirements]**: - AEROBIC -- normal atmosphere - ANAEROBIC -- no free oxygen should be present - MICROAEROPHILLIC -- atmosphere with reduced oxygen levels - FACULATATIVE -- e.g. staphylococci -- will grow in both aerobic + anaerobic conditions - FASTIDIOUS -- e.g. n. gonorrhoeae + meningitidis: require an additional 5% carbon dioxide levels **[CULTURE MEDIA]**: gel or liquid that contains nutrients to grow bacteria Different cell types are grown in various types of medium. Lab mediums must contain: - Carbohydrates - Amino-acids (protein): source of nitrogen - Salts: sodium, potassium, magnesium - Water - Agar -- setting agent -- acts as a stable medium and relatively few bacteria can break down agar i. **[BLOOD AGAR]**: most commonly used in medical lab, contains all of the above and 7% horse/sheep blood. It supports most typesof bacteria, except diptheria and tubercule bacilli ii. **[CHOCOLATE AGAR]**: blood agar heated to 60 degrees for 10 mins. Used to isolate Neisseria + haemophilus species iii. **[SABOURAUD'S AGAR]**: used for isolation of fungi iv. **[BROTH MEDIA]**: allows for growth of small number of organisms, will also dilute any residual antibiotic that may be present in px eye samples **[FUNGAL GROWTH]**: easiest to grow - Moisture is essential - Absorb nutrients from the environment **[BACTERIAL GROWTH]**: generally produced by binary fission - Lag phase - Logarithmic phase (rapid multiplication) - Stationary phase - Decline phase (death of cells) LID MARGIN: BLEPHARITIS, BLEPHAROCONJUNCTIVITS, BLEPHAROKAERTOCONJUNCTIVITIS * * * * * * CONJUNCTIVA: ACUTE BACTERIAL CONJUNCTIVITIS – ADULT * * * * * CONJUNCTIVA: ACUTE BACTERIAL CONJUNCTIITS CHILD * * * Gonorrhae CONJUNCTIVA: PHLYCETENUALR CONJUNCTIVITIS * * CONJUNCTIVA: MEMBRANOUS CONJUNCITIVITIS * * * CONJUNCTIVA: INCLUSION CONJUNCTIVIIS * CORNEA: MICROBIAL KERATITIS * * * * * * * * * * * * * CORNEA: MICROBIAL KERATITIS - CONTACT LENS ASSOCIATED * * * * * * CANALICLULI - CANALICULITIS * ANTERIOR CHAMBER -HYPOPYON – caused by an infection of the AC, sample of AC is collected and examined to find these bacteria * * * ANTERIOR CHAMBER – ENDOPHTHALMITIS * * * * * SCLERA -SCLERITIS * **[BLEPHARITIS]**: bacterial infection of lids -- can be acute or chronic - Specimens are taken from the lid with a moistened swab of bacteriological nutrient broth - Easier to take a specimen with a moist swab instead of a dry swab - Cultured on blood agar plates - Frequency of isolation: +-----------------------------------+-----------------------------------+ | BLEPHARITIS - SACSGCP | | +===================================+===================================+ | Staphylococcus Aureus | - Usually responsible for | | | clinical cases of bleph | | | | | | - May cause lid abscesses | +-----------------------------------+-----------------------------------+ | Coagulase-Negative Staphylococci | - Gram-positive cocci | | | | | | - Major commensals of the skin | | | | | | - Over 20 species -- most | | | common is S. Epidermis | | | | | | - Pxs with chronic infections | | | may be allergic to these | | | commensals and other skin | | | commensals | | | | | | - Pxs are given broad-spectrum | | | antibiotics to reduce the | | | normal skin flora | +-----------------------------------+-----------------------------------+ | Streptococcus Species | - Alpha-hemolytic strains: part | | | of normal skin flora, rarely | | | cause lid infections | | | | | | - Beta-hemolytic strains: | | | Lancefield Group A: can cause | | | severe lid infections + | | | fascitis | +-----------------------------------+-----------------------------------+ | Gram Negative Rods | - Pseudomonas species | | | | | | - Proteus species | +-----------------------------------+-----------------------------------+ | Corynebacterium Species | - Mainly in chronic bleph | +-----------------------------------+-----------------------------------+ | Proponiumbacterium Acnes | - May have a pathogenic role | | | but are accepted as skin | | | commensals too | +-----------------------------------+-----------------------------------+ **[BACTERIAL CONJUNCTIVITS: ]** - Eye is mucopurulent - Bacterial swab is taken out from the conjunctival sac with a sterile swab/plastic disposable loupe - Ideally sample should be immediately plated out on to blood/chocolate agar +-----------------+-----------------+-----------------+-----------------+ | ADULT | CHILD | | | +=================+=================+=================+=================+ | Staph Aureus | - Coagulase | Staph Aureus | | | | positive | | | | | | | | | | - Gram | | | | | positive | | | | | | | | | | - Pyogenic | | | | | Cocci (pus | | | | | forming | | | | | bacteria in | | | | | localised | | | | | infection) | | | | | | | | | | - Cause styes | | | | | on inf lid | | | | | | | | | | - Commonly | | | | | cause wound | | | | | infections, | | | | | eczema, | | | | | boils, | | | | | otilitis + | | | | | food | | | | | poisoning | | | | | | | | | | - Some | | | | | strains are | | | | | resistant | | | | | to | | | | | antibiotics | | | | | and are | | | | | known as | | | | | MRSA | | | | | (methicilli | | | | | n | | | | | resistant | | | | | staph | | | | | aureus) | | | +-----------------+-----------------+-----------------+-----------------+ | Streptococcus | - Gram-positi | | | | Pneumoniae | ve | | | | | | | | | | - Alpha-hemol | | | | | ytic | | | | | | | | | | - Pyogenic | | | +-----------------+-----------------+-----------------+-----------------+ | Haemophilius | - Gram-negati | Haemophillius | | | Influenzae | ve | Influenzae | | | | | | | | | - Pyogenic | | | | | | | | | | - Cocco | | | | | baccili | | | +-----------------+-----------------+-----------------+-----------------+ | Proteus Species | - Pseudomonas | Neisseria | - Gram-negati | | | Aeuroginosa | Gonnorhaea | ve | | | | | cocci | | | - Other | | | | | Proteus | | - Often seen | | | Species | | intracellul | | | | | arly | | | | | | | | | | - Cause | | | | | severe | | | | | haemorrhagi | | | | | c | | | | | mucopurulen | | | | | t | | | | | conjunctivi | | | | | tis | | | | | | | | | | - Corneal | | | | | involvement | | | | | | | | | | - Neonates | | | | | may already | | | | | been born | | | | | with it | +-----------------+-----------------+-----------------+-----------------+ | Moraxella | - Gram | | | | Species | negative | | | | | rods | | | | | | | | | | - Classically | | | | | cause | | | | | angular | | | | | conjunctivi | | | | | tis | | | | | -- | | | | | subconjunct | | | | | ival | | | | | haem | | | | | | | | | | - Natural | | | | | commensal | | | | | of | | | | | naso-phayrn | | | | | x | | | +-----------------+-----------------+-----------------+-----------------+ **[MEMBRANOUS CONJUNCTIVITIS]**: type of conjunctivitis that forms membranes that which when you remove causes bleeding +-----------------------------------+-----------------------------------+ | Neisseria Species | | +===================================+===================================+ | Streptococcus Pyogenes | - Beta hemolytic -- can cause | | | fascitis | | | | | | - Very pyogenic | +-----------------------------------+-----------------------------------+ | Corynebacterium Xerosis | - Gram-positive rods seen in | | | clusters | | | | | | - Commensal of conjunctival sac | | | | | | - Belong to the same species as | | | diptheria bacillus | +-----------------------------------+-----------------------------------+ **[Microbial Keratitis]** -- infection of the cornea caused by bacteria, viruses, fungi, yeasts + amoeba - Infecting microbe gains access to cornea via a break through the epithelium - Washing action of tears normally prevents bacteria to adhere to the normal epithelium - Children, elderly, immunosuppressed and prev infected individuals are particularly susceptible to MK - All pxs with severe MK should be admitted as in-patients and receive intense topical treatment using fortified antibiotics **[BACTERIAL MICROBIAL KERATITIS]**: +-----------------------------------+-----------------------------------+ | Staph Aureus | - Been isolated from over 50% | | | of MK cases in the UK | +===================================+===================================+ | Coagulase Negative Staphylococci | - Over 40 species recognised | | | | | | - Staph Lugdunensis | | | | | | - Staph Haemlyticus | +-----------------------------------+-----------------------------------+ | Streptococcus Species | - Strep Pneumoniae: cause a | | | severe mucopurulent infection | | | | | | - Viridans Streptococci: cause | | | a crystalline keratopathy | | | | | | - Beta-haemolytic Streptococci: | | | rarely isolated from MK cases | +-----------------------------------+-----------------------------------+ | Pseudomonas Aeruginosa | - Frequently isolated from CLs | | | wearers | | | | | | - Within 48 hours this bacteria | | | can penetrate the full | | | thickness of the cornea due | | | to its invasiveness and | | | endotoxins it releases | | | | | | - Found in water | | | | | | - Resistant naturally to many | | | chemicals and antibiotics | | | | | | - Pseudomonas + MRSA: most | | | common causes of hospital | | | acquired infections | +-----------------------------------+-----------------------------------+ | Moraxella | - Gram-negative diplo bacilli | | | | | | - Can cause severe MK | | | | | | - Very sensitive to a wide | | | range of antibiotics | | | | | | - Corneal stroma is slow to | | | heal following an infection | +-----------------------------------+-----------------------------------+ | Branhamella Species | - Gram-negative cocci | | | | | | - Similar to Neisseria | | | | | | - Low pathogenicity, commensal | | | of respiratory tract | | | | | | - Only responsible for a few | | | cases of MK | +-----------------------------------+-----------------------------------+ | Proteus + Serratia Species | - Gram-negative rods | | | | | | - Only responsible for a few | | | cases of MK in | | | immunocompromised patients | +-----------------------------------+-----------------------------------+ | Haemophilus Infuenzae | - Usually cause conjunctivitis | | | but has occasionally been | | | isolated from the cornea | +-----------------------------------+-----------------------------------+ | Nocardia Species | - Gram-positive rods | | | | | | - Pleomorphic: ability to | | | change their shape according | | | to their environment | | | | | | - Microaerophilic: require low | | | levels of oxygen | | | | | | - Prefer to grow at 28 degrees | | | | | | - Low pathogenicity but have | | | been isolated from the cornea | | | and in general medicine in | | | immunocompromised patients | +-----------------------------------+-----------------------------------+ | Chlamidya Trachomatis | - Gram-indeterminate | | | | | | - Cannot be stained with | | | gram-stain | | | | | | - Struturally ery similar to | | | gram-negative | +-----------------------------------+-----------------------------------+ **Fungal Keratitis: Found mainly in humid conditions, rarely in the UK** +-----------------------------------+-----------------------------------+ | **Aspergillus Niger** | - **Found in the UK, on all | | | types of grass, particularly | | **Aspergillus Fumigatus** | in mouldy hay** | +===================================+===================================+ | **Fusarium** | - Cause acute MK: Cornea is | | | severly scarred | | | | | | - Several cases been reported | | | in the UK but mainly | | | infection occurs from abroad | +-----------------------------------+-----------------------------------+ **[MK CAUSED BY YEASTS]**: - Single round bodies - 4-6 microns in diameter - Gram-positive - Reproduce by budding - Can produce pseudohyphae in tissues - Candida albicans -- most frequently isolated from pxs with MK - Candida paropsilosis -- also been found in MK pxs - Px usually has a predisposing infection or is immunosuppressed - Candida species must be treated with antifungals **[Amoebic MK]**: - Free-living organism In water, mud and water-cooling tanks - First identified in the cornea in 1969 - When they invade the cornea they go all the way through the stroma to the Descements Membrane within a few days - Amoeba feed on gram-negative rods -- found in large numbers in lens storage cases of non-compliant patients: solutions not being changed regularly, a biofilm forms and bacterial multiplication occurs - Active, vegetative amoebae: TROPHOZOITES - Non-active state: CYSTS - Acanthamoeba polyphaga: - most isolated - Acanathamoeba castellani - Should take 2 biopsies: 1^st^: histological examination 2^nd^: culture -- corneal material is ground up + inoculated into non-nutrient agar that have been seeded with E. Coli, plates incubated at 37 degrees for 3-6 days -plates examined at surface level with a microscope at 100x mag -if no growth evident, then plates must be incubated at 28 degrees for a further 10 days -amoebae may be detected by this method at 36 hours but can take on average 6 days - TREATMENT: - Brolene -- disinfectant/antifungal - Neomycin- antibiotic - Chlorhexidine -- antiseptic/disinfectant - Antifungals - PHMB -- polyhexamethyl biguanidine -- antimicrobial **[MARGINAL KERATITIS]**: - Staph Aureus - Inflammation of the corneoscleral junction **[CANALICULITIS:]** -Chronic condition -Px may describe a history of epiphora over months/years -Canaliculi are completely blocked leading to anaerobic conditions to develop -TREATMENT: syringing of ducts + Penicillin G +-----------------------------------+-----------------------------------+ | ACTINOMYCES ISRAELII | - Anaerobic | | | | | | - Gram-positive | | | | | | - Found in cheesy concretions | | | that may be expressed from | | | the canaliculi | +===================================+===================================+ | BACTERIODES | - Anaerobic | | | | | | - Gram-negative | | | | | | - Filamentous rods | +-----------------------------------+-----------------------------------+ **[ENDOPHTHALMITIS]**: - Usually caused by post-operative cases/trauma/exogenous infections - Samples of vitreous and AH sent to lab - Microscopic evaluation on immediate arrival of sample AND inoculation on chocolate, blood and Sabouraud's agar - Staph aureus, Pseudomonas, Enteric bacteria, Streptococcus and various fungi **[CHRONIC ENDOPHTHALMITIS]**: - Can manifest many weeks post cataract operation - Skin commensals can adhere to the implant and cause infection - Coagulase-negative Staphylococci + Propionum Bacterium **[Treatment of Anterior Segment Microbial Disease]**: - Initially will give a broad spectrum antibiotic -- An agent that is effective against gram positive, gram negative and rods - IF the disease is moderate, severe or unresponsive then it is usual to attempt to isolate the pathogen - 50% of MK cases are culture negative however- the sample will not produce a pathogen in 24 hours - **[Sensitivity Testing]**: - After isolation, antibiotic sensitivity is tested - Mainly performed for bacteria, not for acanthamoeba, fungi or viruses - DISC DIFFUSION: main method of choice - Zones of inhibition of bacterial growth compared to controls are examined - Where there is growth of bacteria would signify antibiotic resistance -**Broad Spectrum**: effective against gram-positive, gram-negative and rods -**Narrow Spectrum**: effective against only specific microoragnisms -**Bacteriostatic**: inhibit bacterial growth -**Bacteriocida**l: inhibit growth + destroy bacteria +---------+---------+---------+---------+---------+---------+---------+ | ANTIBIO | SYSTEMI | TOPICAL | GRAM | GRAM | BROAD | WHO TO | | TIC | C | | | | | GIVE | | | | | POSITIV | NEGATIV | SPEC | | | | | | E | E | | | +=========+=========+=========+=========+=========+=========+=========+ | AMIKASI | \* | | | \* | | - Giv | | N | | | | | | e | | | | | | | | to | | | | | | | | inf | | | | | | | | ections | | | | | | | | tha | | | | | | | | t | | | | | | | | are | | | | | | | | res | | | | | | | | istant | | | | | | | | to | | | | | | | | GEN | | | | | | | | TAMICIN | +---------+---------+---------+---------+---------+---------+---------+ | AMPICIL | \* | | | \* | | - Giv | | LIN | | | | | | e | | | | | | | | to | | | | | | | | inf | | | | | | | | ections | | | | | | | | tha | | | | | | | | t | | | | | | | | are | | | | | | | | res | | | | | | | | istant | | | | | | | | to | | | | | | | | GEN | | | | | | | | TAMICIN | +---------+---------+---------+---------+---------+---------+---------+ | BACITRA | \* | | \* | | | | | CIN | | | | | | | | ZINC | | | | | | | +---------+---------+---------+---------+---------+---------+---------+ | CEFTAZI | | \* | \* | | | - Giv | | DIME | | | | | | en | | | | | | | | in | | | | | | | | con | | | | | | | | junctio | | | | | | | | n | | | | | | | | wit | | | | | | | | h | | | | | | | | Pol | | | | | | | | ymyxin | | | | | | | | B + | | | | | | | | Neo | | | | | | | | mycin | +---------+---------+---------+---------+---------+---------+---------+ | CEFUROX | \* | | | | \* | | | IME | | | | | | | +---------+---------+---------+---------+---------+---------+---------+ | CHLORAM | \* | \* | | | \* | - Con | | PHENICO | | | | | | junctiv | | L | | | | | | itis | | | | | | | | | | | | | | | | - Not | | | | | | | | sui | | | | | | | | table | | | | | | | | for | | | | | | | | pse | | | | | | | | udomona | | | | | | | | s | | | | | | | | inf | | | | | | | | ections | +---------+---------+---------+---------+---------+---------+---------+ | CIPROFL | \* | \* | | | \* | - Sta | | OXACIN | | | | | | phyloco | | | | | | | | ccal | | | | | | | | inf | | | | | | | | ections | +---------+---------+---------+---------+---------+---------+---------+ | ERYTHRO | \* | | | | \* | - Bac | | MYCIN | | | | | | terial | | | | | | | | ble | | | | | | | | phariti | | | | | | | | s | +---------+---------+---------+---------+---------+---------+---------+ | FUSIDIC | | \* | | | | - Nar | | ACID | | | | | | row | | | | | | | | spe | | | | | | | | ctrum | | | | | | | | mai | | | | | | | | nly | | | | | | | | for | | | | | | | | sta | | | | | | | | phyloco | | | | | | | | cci | +---------+---------+---------+---------+---------+---------+---------+ | GENTAMI | | \* | | \* | | - Ami | | CIN | | | | | | noglyco | | | | | | | | side | | | | | | | | ant | | | | | | | | ibiotic | | | | | | | | | | | | | | | | - Use | | | | | | | | d | | | | | | | | in | | | | | | | | ext | | | | | | | | ernal | | | | | | | | bac | | | | | | | | terial | | | | | | | | inf | | | | | | | | ections | | | | | | | | | | | | | | | | - Eff | | | | | | | | ective | | | | | | | | aga | | | | | | | | inst | | | | | | | | Pse | | | | | | | | udomona | | | | | | | | s | +---------+---------+---------+---------+---------+---------+---------+ | LEVOFLO | | \* | | | \* | - Qui | | XACIN | | | | | | nolone | | | | | | | | ant | | | | | | | | ibiotic | +---------+---------+---------+---------+---------+---------+---------+ | NEOMYCI | | \* | | | \* | - Ami | | N | | | | | | noglyco | | | | | | | | side | | | | | | | | ant | | | | | | | | ibiotic | +---------+---------+---------+---------+---------+---------+---------+ | OFLOXAC | \* | \* | | | \* | - Qui | | IN | | | | | | nolone | | | | | | | | ant | | | | | | | | ibiotic | | | | | | | | | | | | | | | | - Eff | | | | | | | | ective | | | | | | | | aga | | | | | | | | inst | | | | | | | | Pse | | | | | | | | udomona | | | | | | | | s | +---------+---------+---------+---------+---------+---------+---------+ | POLYMYX | | \* | | | | - Can | | IN | | | | | | als | | B | | | | | | o | | SULFATE | | | | | | be | | | | | | | | use | | | | | | | | d | | | | | | | | sub | | | | | | | | conjunc | | | | | | | | tivally | | | | | | | | | | | | | | | | - Eff | | | | | | | | ective | | | | | | | | aga | | | | | | | | inst | | | | | | | | Pse | | | | | | | | udomona | | | | | | | | s | | | | | | | | | | | | | | | | - No | | | | | | | | lon | | | | | | | | ger | | | | | | | | com | | | | | | | | mercial | | | | | | | | ly | | | | | | | | ava | | | | | | | | ilable | | | | | | | | in | | | | | | | | the | | | | | | | | UK | +---------+---------+---------+---------+---------+---------+---------+ | PROPAMI | | \* | \* | \* | | - Aro | | DINE | | | | | | matic | | ISETION | | | | | | dia | | ATE/ | | | | | | midine | | | | | | | | dis | | DIPROMP | | | | | | infecta | | ROPRAMD | | | | | | nt | | INE | | | | | | | | | | | | | | - Eff | | ISETION | | | | | | ective | | ATE | | | | | | aga | | | | | | | | inst | | | | | | | | bot | | | | | | | | h | | | | | | | | but | | | | | | | | mor | | | | | | | | e | | | | | | | | to | | | | | | | | Gra | | | | | | | | m | | | | | | | | Pos | | | | | | | | itive | +---------+---------+---------+---------+---------+---------+---------+ | TETRACY | \* | | | | \* | - Bac | | CLINE | | | | | | terial | | | | | | | | ble | | | | | | | | phariti | | | | | | | | s | | | | | | | | | | | | | | | | - Als | | | | | | | | o | | | | | | | | eff | | | | | | | | ective | | | | | | | | aga | | | | | | | | inst | | | | | | | | som | | | | | | | | e | | | | | | | | pro | | | | | | | | tozoa | +---------+---------+---------+---------+---------+---------+---------+ | TICARCI | \* | | | | | - Eff | | LLIN | | | | | | ective | | | | | | | | aga | | | | | | | | inst | | | | | | | | pse | | | | | | | | udomona | | | | | | | | s | | | | | | | | and | | | | | | | | Pro | | | | | | | | teus | +---------+---------+---------+---------+---------+---------+---------+ **[Treatment of Microbial Keratitis]**: - ANTIMICROBIAL COMPOUNDS: to get rid of the infectious agent - CORTICOSTEROIDS: suppress the immune system to prevent scarring and preserve vision - INITIAL MANAGEMENT: - Intensive therapy - Anti-bacterial therapy: instillation of antibiotics every 30-60 mins for 48 hours (can be longer if fungal or viral infection) - Disease duration, cost to treat + severity: depends on causative agent - Systemic absorption of drops can occur through the conjunctiva, nasolacrimal system, oropharynx, digestive system, and skin - 80% of each eye drop is available for absorption +-----------------+-----------------+-----------------+-----------------+ | Causative agent | Therapy | Mode of Action | Example | | for MK | | | | +=================+=================+=================+=================+ | Standard | Monotherapy | Affect DNA | Ciprofloxacin | | Bacteria | with | synthesis by | | | | fluorquinolone | inhibiting DNA | Ofloxacin | | | eye drops | gyrase enzyme | | | | | of bacteria | | | | | which is | | | | | essential for | | | | | DNA replication | | +-----------------+-----------------+-----------------+-----------------+ | Severe | Fortified | Inhibits | Tobramycin | | Ulceration | antibiotics: | bacterial | | | | aminoglycosides | protein | | | | + cephalosporin | synthesis | | +-----------------+-----------------+-----------------+-----------------+ | Staph-related | Vancomycin | Inhibits | | | MK | | synthesis of | | | | | bacterial cell | | | | | wall | | +-----------------+-----------------+-----------------+-----------------+ | Gram-negative | Gentamicin | | | | MK | | | | +-----------------+-----------------+-----------------+-----------------+ - Viral, fungal and amoebic infections: very difficult to treat: **[VIRAL INFECTIONS]**: - Acylovir: most common drug used to treat viral infections a. Inhibits DNA polymerase enzyme in herpes infections b. Viral DNA polymerases recognise acyclovir as nucleotide thymidine and incorporates acyclovir into the viral DNA which halts the replication of viral DNA **[FUNGAL DISEASE]**: - Azoles: most common drug used to treat fungal infections - Anti-fungal drugs are usually prescribed with debridement of the cornea to allow faster drug penetration - Fungal cells are more similar to human cells -- therefore the anti-fungal drugs taken systemically can prove to be toxic - 1^st^: broad-spectrum topical antibiotic 2^nd^: more specifc anti-fungal drugs **[AMOEBAL INFECTIONS]**: - Ketoconazole, miconazole, propamidine isethionate (brolene) - Multiple antibiotics + antifungals - Hospitalisation: necessary - Penetrating keratoplasty may also be needed in order to recover useful vision