## Summary
 <table>
 <tbody>
 <tr>
 <td>Cocci</td>
 </tr>
 <tr>
 <td>Staphylococci</td>
 <td>Gram positive</td>
 <td>Aerobic Facultatively anaerobic</td>
 <td>Belong to Micrococcaceae family All types produce catalase S. aureus cause haemolysis on blood agar - S. epidermidis don't Divides in two planes</td>
 <td>Coag positive: S. aureus, S. intermedius, S hyicus S. aureus - yellow colony S. epidermidis - white colony. Associated with hypersensitivity marginal keratitis</td>
 </tr>
 <tr>
 <td>Streptococci (rare ocular pathogens)</td>
 <td>Gram positive</td>
 <td>AerobicFacultatively anaerobic</td>
 <td>Catalase negative Slightly oblong cell shape Divides in one plane</td>
 <td>Strep pyogenes (beta-haemolytic): scarlet fever Strep pneumoniae (alpha-haemolytic): pneumonia and meningitis (associated with C3 deficiency) Crystalline keratopathy</td>
 </tr>
 <tr>
 <td>Neisseria</td>
 <td>Gram negative</td>
 <td>Aerobic</td>
 <td>IgA proteases cleave immunoglobulins N. gonorrhoea ferments glucose N. meningitidis ferments glucose and maltose</td>
 <td>N. meningitidis: meningococcus (associated with C5-9 deficiency) N. gonorrhoea: gonococcus (ophthalmia neonatorum). CAN breach intact epithelium Grow on chocolate agar Have endotoxin activity</td>
 </tr>
 <tr>
 <td>
 Bacilli
 </td>
 </tr>
 <tr>
 <td>Mycobacteria</td>
 <td>Ziehl-Neelson stain</td>
 <td>Aerobic</td>
 <td>&nbsp;</td>
 <td>M. tuberculosis: man is the primary host. Resists destruction by intracellular enzymes. Caseating granuloma of macrophages</td>
 </tr>
 <tr>
 <td>Bacillus genus</td>
 <td>Gram positive</td>
 <td>Aerobic&nbsp;</td>
 <td>Catalase-positive, spore-forming</td>
 <td>Bacillus anthracis: anthrax Bacillus cereus: food poisoning Post-traumatic endophthalmitis (25% of cases especially with intraocular foreign bodies and rural settings). Causes a fulminant endophthalmitis with rapid/severe vision loss. Treat with intravitreal vancomycin or clindamycin</td>
 </tr>
 <tr>
 <td>Clostridia</td>
 <td>Gram positive</td>
 <td>Obligate anaerobes</td>
 <td>Can produce powerful exotoxins. Tetanus toxin affects presynaptic terminals of inhibitory interneurones, preventing normal inhibitory control of motor neurones</td>
 <td>C. tetani: tetanus. Toxin travels beyond the wound but the bacteria do not. Tetanus can occur weeks after infection. Antitoxin is ineffective once nervous tissue affected C perfringens: gas gangrene, conjunctivitis, necrotizing keratitis, panophthalmitis (detected by positive Nagler reaction) *these produce disease if implanted deep in tissues</td>
 </tr>
 <tr>
 <td>Propionibacterium acnes</td>
 <td>Gram positive</td>
 <td>Obligate anaerobe</td>
 <td>&nbsp;</td>
 <td>CommensalBlepharitis, (delayed post-op, chronic) endophthalmitis</td>
 </tr>
 <tr>
 <td>Actinomyces</td>
 <td>Gram positive</td>
 <td>Facultative/obligate anaerobe</td>
 <td>&nbsp;</td>
 <td>Chronic canaliculitis Sensitive to penicillin Discharges contain yellow sulphur granules</td>
 </tr>
 <tr>
 <td>Haemophilus influenzae</td>
 <td>Gram negative</td>
 <td>Facultative anaerobe. Depends on haematin which is produced by many bacteria</td>
 <td>Type b capsule antigen is key determinant of virulence. It is not always encapsulated but increased virulence if so as it can avoid phagocytosis</td>
 <td>Commonly isolated in preseptal/orbital cellulitis in infants/toddlers. CAN breach intactcorneal epithelium Meningitis, sinusitis,&nbsp; and epiglottitis</td>
 </tr>
 <tr>
 <td>Enterobacteriaceae</td>
 <td>Gram negative</td>
 <td>Aerobic</td>
 <td>GI commensals</td>
 <td>E. coli (motile) Klebsiella (non-motile) Salmonella (urease neg) Proteus (urease pos)</td>
 </tr>
 <tr>
 <td>Moraxella lacunata</td>
 <td>Gram negative</td>
 <td>&nbsp;</td>
 <td>Grows on MacConkey agar Sensitive to chloramphenicol</td>
 <td>Central corneal ulcers, chronic conjunctivitis, angular blepharitis</td>
 </tr>
 <tr>
 <td>Pseudomonas</td>
 <td>Gram negative</td>
 <td>Aerobic. Dependent on iron for growth</td>
 <td>Proteases allow penetration through traumatised epithelium (note cannot pass through intact epithelium).Toxin A destroys protein glycol matrices</td>
 <td>Risk factors: trauma, burns, vitamin A deficiency, immunosuppression</td>
 </tr>
 <tr>
 <td>Bartonella henselae</td>
 <td>Gram negative</td>
 <td>&nbsp;</td>
 <td>Transmitted via a cat scratch or bite</td>
 <td>Cat-scratch neuroretinitis (macular star with optic disc swelling) and Parinaud&rsquo;s oculoglandular syndrome (unilateral granulomatous conjunctivitis with ipsilateral swollen preauricular nodes) Treatment: oral doxycycline or erythromycin (with or without rifampicin)</td>
 </tr>
 <tr>
 <td>
 Other
 </td>
 </tr>
 <tr>
 <td>Chlamydia trachomatis(ovoid shape)</td>
 <td>Gram negative (weak)</td>
 <td>Obligate intracellular bacteria</td>
 <td>No cell wall Grow within eukaryotic cells: cannot produce energy alone. Glycogen positive</td>
 <td>Serotypes A, B and C: trachoma Serotypes D to K: inclusion conjunctivitis (STI) Serotypes L1, 2 and 3: lymphogranuloma venereumDiagnosis: Giemsa staining, ELISA, antibody in serum (immunofluorescent staining), PCR or NAAT</td>
 </tr>
 <tr>
 <td>Borrelia burgdorferi</td>
 <td>spirochaete</td>
 <td>&nbsp;</td>
 <td>Rodents are the main reservoir (humans are incidental hosts via ticks)</td>
 <td>Lyme disease</td>
 </tr>
 <tr>
 <td>Treponema pallidum</td>
 <td>spirochaete</td>
 <td>Temperature sensitive</td>
 <td>Enclosed in cytoplasmic membrane and peptidoglycan cell wall and envelope. Motile&nbsp;</td>
 <td>T. pallidum: SyphilisT. pertenue: yaws&nbsp;</td>
 </tr>
 </tbody>
 </table>


## Conjunctivitis and blepharitis
<ul>
 <li>Streptococcus pneumoniae</li>
 <li>Staphylococcus aureus</li>
 <li>Moraxella&nbsp;</li>
 <li>Neonatal conjunctivitis</li>
 <ul>
 <li>Neisseria gonorrhoeae</li>
 <li>Chlamydia trachomatis</li>
 <li>Herpes simplex virus (rare)</li>
 <li>
 Typically treated with systemic antibiotics and regular irrigation of the conjunctival sac
 (topical therapy may be added)
 </li>
 </ul>
</ul>
<HotTopic>
 
 Neisseria gonorrhoeae is the most common cause of hyperacute, purulent conjunctivitis. As it can
 penetrate intact corneal epithelium, it can rapidly progress to ulceration and perforation.
 
</HotTopic>
Pseudomonas aeruginosa
<ul>
 <li>Most common cause of bacterial keratitis worldwide (60% of CL-related keratitis)</li>
 <li>Gram negative bacillus</li>
 <li>GI commensal</li>
 <li>Common in freshwater</li>
 <li>Risk factors:</li>
 <ul>
 <li>CL wear</li>
 <li>Corneal injury</li>
 </ul>
 <li>Virulence factors</li>
 <ul>
 <li>
 Exotoxins via type III secretion system (T3SS). T3SS acts like a needle, creating a
 pore-forming complex with the host plasma membrane through which effector proteins (exotoxins)
 are &ldquo;injected&rdquo; into the cytosol.
 </li>
 <li>ExoU causes rapid cell lysis and severe corneal disease&nbsp;</li>
 </ul>
 <li>
 Host response is primarily innate immunity driven although adaptive immunity does play a role in
 later stages of infection
 </li>
 <ul>
 <li>
 LPS and flagellin activate TLR4 and TLR5 on macrophages producing a chemotactic and
 proinflammatory response
 </li>
 </ul>
</ul>

## Streptococcus
<ul>
 <li>S. pyogenes is a common Gram positive throat commensal</li>
 <li>S. pneumoniae is an upper respiratory commensal and commonly found in the conjunctiva</li>
 <li>Common cause of bacterial keratitis</li>
 <li>Corneal injury allows opportunistic infection (often aggressive)</li>
 <li>Exotoxins are produced: pneumolysin is the most potent</li>
 <ul>
 <li>Forms pores in host cell membranes leading to leakage and death</li>
 </ul>
</ul>

## Staphylococcus aureus
<ul>
 <li>Gram positive, coagulase positive, phosphatase positive</li>
 <li>Produces exotoxins</li>
 <li>Ferments mannitol</li>
 <li>Colonies have a golden appearance</li>
 <li>Less severe disease compared to streptococcus and pseudomonas</li>
 <li>Causes peripheral ulcers</li>
 <li>Most common cause of carbuncle and phage types I and II cause boils</li>
 <li>Resistant strains can be difficult to treat: MRSA</li>
 <li>Virulence factors: haemolysins facilitate bacterial survival.</li>
 <li>Other coagulase positive staph include S. intermedius and S. hyicus</li>
</ul>

## Trachoma
<ul>
 <li>Most prevalent microbial cause of blindness worldwide</li>
 <li>Caused by chlamydia trachomatis subgroup A, B, Ba, and C</li>
 <ul>
 <li>Serotypes D-K cause an inclusion conjunctivitis</li>
 </ul>
 <li>Replicate in conjunctival epithelium</li>
 <li>Forms spores that are transmitted</li>
 <li>Clinical features</li>
 <ul>
 <li>Mixed papillary conjunctivitis and follicular response</li>
 <li>Tarsal conjunctival scarring</li>
 <li>
 Entropion due to contraction of the scar and trichiasis
 </li>
 <li>Blinding corneal opacity due to corneal scratch from lashes</li>
 <li>Stages</li>
 <ul>
 <li>I: involvement of conjunctival stroma</li>
 <li>II: involvement of the cornea with pannus formation</li>
 <li>III: fibrous replacement of inflamed tissue</li>
 <li>IV: contraction with entropion and trichiasis</li>
 </ul>
 </ul>
 <li>IFN-gamma plays a role</li>
 <li>Treatment</li>
 <ul>
 <li>Azithromycin</li>
 <li>Hygiene/facial cleanliness to prevent transmission</li>
 <li>Lid surgery for entropion and trichiasis</li>
 <li>Environmental health</li>
 </ul>
</ul>

## Reiter&rsquo;s syndrome
<ul>
 <li>May follow chlamydial urethritis or Gram negative dysentery</li>
 <li>Commoner in people with HLA-B27</li>
 <li>Males &gt; females</li>
 <li>Triad:</li>
 <ul>
 <li>Non-gonococcal urethritis</li>
 <li>Conjunctivitis</li>
 <li>Arthritis</li>
 </ul>
 <li>Systemic findings</li>
 <ul>
 <li>Keratoderma blennorrhagica</li>
 <li>Aphthous ulcers</li>
 <li>Circinate balanitis</li>
 </ul>
</ul>

## Moraxella lacunata
<ul>
 <li>Gram negative bacillus</li>
 <li>Chronic conjunctivitis</li>
 <li>Angular blepharitis</li>
 <li>Keratitis in frail patients</li>
</ul>

## Spores
<ul>
 <li>Central cortex with layered outer coat of keratin</li>
 <li>Mostly produced by Gram positive bacilli</li>
 <li>Function as a resting and defensive form for bacteria to exist (NOT for reproduction)</li>
 <ul>
 <li>Resistant to antibiotics</li>
 <li>Can be killed by temperatures of 120 degrees for 20 minutes</li>
 </ul>
 <li>Cannot be identified with Gram staining</li>
</ul>

## Chlamydia life cycle
<ul>
 <li>Two forms:</li>
 <ul>
 <li>Elemental body (infectious form)</li>
 <li>Reticulate body (replicate form)</li>
 </ul>
 <li>Elemental body penetrates cell</li>
 <li>Enclosed in cytoplasmic vesicle to avoid lysosomal destruction</li>
 <li>Organises into reticulate body</li>
 <li>Divides for 24 hours</li>
 <li>Regresses to elemental form</li>
 <li>Chlamydia can cause latent infection</li>
</ul>

## Syphilis
<ul>
 <li>Caused by Treponema pallidum (a spirochaete)</li>
 <li>Treponema dies quickly in the outside environment</li>
 <li>
 VDRL (Venereal Disease Research Laboratory test) is a screening test but can also be positive in
 leprosy, malaria and connective tissue diseases including RA, SLE and APS
 </li>
 <ul>
 <li>Detects anti-cardiolipin antibodies</li>
 <li>Produces a titre which can be used to monitor the response to treatment</li>
 </ul>
 <li>FTA-ABS (fluorescent treponemal antibody absorption test) is the confirmatory test</li>
 <ul>
 <li>More sensitive&nbsp;</li>
 <li>Remains positive for life</li>
 <li>No titre</li>
 </ul>
 <li>Treatment: high-dose penicillins, doxycycline or erythromycin</li>
</ul>

## Borrelia burgdorferi
<ul>
 <li>Spirochaete</li>
 <li>Helical structure with flagella</li>
 <li>Can be visualised with dark-ground (aka dark-field) microscopy</li>
 <li>ELISA can be used to detect IgG and IgM antibodies</li>
 <li>Transmitted by ticks: causes Lyme disease</li>
</ul>

## Endophthalmitis
<ul>
 <li>
 Present 2-5 days postoperatively and is generally caused by an organism of the patient&rsquo;s
 lid flora
 </li>
 <li>Most commonly cause by Gram positive organisms</li>
 <ul>
 <li>
 Coagulase negative staphylococci (eg. Staph. epidermidis): best visual
 prognosis
 </li>
 <li>Staphylococcus aureus</li>
 <li>Beta-haemolytic streptococci</li>
 <li>Enterococcus faecalis: worst visual prognosis</li>
 </ul>
 <li>Gram negative culprits</li>
 <ul>
 <li>Haemophilus influenzae</li>
 <li>Pseudomonas aeruginosa</li>
 </ul>
</ul>

## Encapsulated organisms
<ul>
 <li>Staphylococcus</li>
 <li>Streptococcus pneumoniae</li>
 <li>Haemophilus influenzae type B</li>
 <li>Neisseria meningitidis</li>
 <li>Group B streptococcus</li>
 <li>Klebsiella pneumoniae</li>
 <li>Salmonella typhi</li>
 <li>Pneumocystis carinii</li>
</ul>

Microbiology

Bacterial Infections

Intro

FRCOphth Part 1 Study Notes

Orbit and ocular adnexae

Orbit

Extraocular Muscles

Orbital Blood Vessels

Paranasal Sinuses

Lacrimal Glands

Tear Film

Eyelids

Blinking

Anterior segment - ocular surface

Conjunctiva

Conjunctivitis

Sclera

Cornea

Corneal Structure And Development

Corneal Physiology

AC to Lens

Angle

Ciliary Body

Aqueous Humour Dynamics

Iris

Pupil

Lens

Posterior segment

Choroid

Vitreous

Retinal Macrostructure

Neurosensory Retina

Retinal Pigment Epithelium

Neuroanatomy

Venous Sinuses

Cerebral Ventricles

Cerebral Blood Supply

Supranuclear Gaze Pathways

Head And Neck Autonomic Nervous Supply

Head And Neck Glands

Osteology

Nerves

Muscles And Pharyngeal Arches

Extraocular Nerves

Sensory Nerves

Physiology

Physics Of Blood Flow

Neuronal Control Of Blood Vessels

Oxygen-Haemoglobin Dissociation Curve

Cytochrome p450

Pituitary Gland

Thyroid Hormone Production

Insulin

Glucagon

Parathyroid Hormone

Corticosteroids

Catecholamines

Cardiac Cycle

Renal Physiology

Fluid Balance

Acid-Base Balance

Muscle Physiology

Sensory Fibres

Cutaneous Receptors

Endocytosis

Glycosaminoglycans

Condensed Ocular Biochemistry

Eye Movements

Accomodation

Vision

Visual Cycle And Phototransuction

Visual Pathway

Visual Acuity

Colour Vision

Binocular Vision

Pathology

Collagen

Tissue Damage

Inflammation

Disease Entities

Wound Healing

Thrombosis / Atherosclerosis

Cell Growth

Neoplasia

Histopathology

Nystagmus

Free Radicals And Antioxidants

Immunology

Ocular Immunology

Viral Infections

Fungal Infections

Protozoa

Nematodes

Antimicrobials

Genetics

Chromosomes

Mitosis

Meiosis

Genes

Polypeptide Synthesis

Histones

MicroRNA

Hardy-Weinberg Equilibrium

Mutations

Chromosome Defects

Autosomal Inheritance

X-Linked Inheritance

Mitochondrial Inheritance

Multifactorial Inheritance