Flashcard Machine Microbiology
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| Iga defense mechanism |
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| Neutralization and Opsonization at mucosal surfaces |
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| Lysozyme |
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| cleaves glycosal bonds in the peptidoglycan bacterial cell wall |
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| normal bacterial flora -staph epidermidis -c. xerosis |
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| provide defense by competing with the pathogen |
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| Blepharitis |
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| -Inflamation of the Eyelid -caused by S. Aureus usually -may be caused by HSV, Varicella or Phthiris Pubis -often chronic due to poor hygiene |
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| Conjunctivitis |
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| "Pink- eye" can be both bacterial and viral |
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| Keratitis features |
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| -Infection of the cornea w/ ulcers and necrosis -can cause blindness due to accumulation of immune cells -caused by HSV or a parasite or following corneal trauma or contact lenses |
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| Keratoconjunctivitis |
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| -Infection of the conjunctiva and cornea -caused by Adenovirus and Chlamydia |
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| Blepharitis sx's |
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| -itching, burning, redness and crusting of the eyelashes |
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| Complication of Blepharitis |
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| -Stye/Hordeolum: acute localized infection of the tear gland, seb gland or hair follicle |
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| S. Aureus distinguishing features |
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| -Gram + cocci -CAT POSITIVE -COAG POSITIVE (differentiates from other staph, allows abscess formation) -Beta hemolytic -mannitol fermentation -resistant to penicillin! |
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| S. Aureus virulence factors |
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| -Protein A (binds to Fc of IgG preventing opsonization) -Coagulase -Fibronectin Binding Protein -Alpha toxin (lyses cells) |
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| Bacterial Conjunctivitis distinguishing features |
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| -Acute onset -Purulent Discharge -Pruritis |
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| Bacterial agents causing Conjunctivitis |
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| -S. Epidermidis -S. Pyogenes -S. PNA -H. Aegyptius (gram -) |
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| Bacterial Conjunctivitis Dx and Tx |
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| -Hx and PEx -Gram Stain -Topical Abx |
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| S. Epidermidis distinguishing features |
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| -COAG NEGATIVE (like all staph except Aureus) -Novobiocin sensitive -normal flora of skin -Has Biofilm (protects against complement and phagocytosis) |
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| Streptococcus group features |
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| -Gram + cocci in pairs or chains -facultative anaerobes -non-motile -CAT negative -classified by alpha/beta/gamma -Lancefield Ags |
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| S. Pyogenes distinguishing features |
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| -pairs or chains -group A has A Ag -beta hemolytic *susceptible to bacitracin -lives in nares, URT and skin |
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| S. Pyogenes virulence factors |
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| -M Protein and Protein F (binding to conjunctiva) -Protein G (prevents opsonization) -c5a peptidase and IgA protease -Streptolysins O and S -exotoxins SPEA |
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| S. PNA distinguishing features |
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| -No Lancefield Ags -Alpha hemolytic -grows in pairs (cocci) -Optochin sensitive |
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| S. PNA virulence factors |
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| -Polysaccharide capsule -Autolysins (in cell wall) -Pneumolysins (in cytoplasm) |
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| H. Aegyptius (Influenzae) distinguishing features |
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| -Gram negative bacilli -facultative anaerobe -grows on Choc Agar w/ NAD and Factor X -non-encapsulated |
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| H. Aegyptius virulence factors |
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| -IgA Protease -Biofilm (does NOT cause PNA or otitis media!) |
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| Neonatal Bacterial Conjunctivitis (Purulent) AKA Opthamlmia Neonatorum |
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| -presents during first month of life (3-5 days post birth usually) -caused by N. Gonorrhea or Chlamydia Trachomatis -can lead to blindness or systemis illness -tx w/ erythromycin ointment |
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| N. Gonorrhoeae distinguishing features |
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| -Gram negative diplococci -non motile -Oxidase positive -Aerobic (increase Co2) -ferments GLUCOSE only -NON encapsulated |
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| N. Gonorrhoeae virulence factors |
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| -Pili/adherence-antigentic variation and phase variation; urethral, vaginal, recta, conjunctival epithelium) -lipooligosaccharide -Sialic acid- mimics RBS's -IgA Protease -OMP's for attachement |
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| Chlamydiae distinguishing features |
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| -leading cause of preventable blindness -intracellular parasite (can't make ATP) -grows in inclusion bodies -cell wall looks Gram Neg. -need to identify w/ immunofluorescence -has group specific Ag -transmitted by contact and flies -3-10 day incubation |
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| C.Trachomatis Distinguishing features |
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| -causes Trachoma (serotype A-C) -causes STDs leading to inclusional conjunctivits and PNA in infants -causes Lymphogranuloma Venereum |
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| Neonatal Conjunctivitis (ICN) |
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| -sxs begin 5-14 days post birth in 20-50% of newborns with infected mothers -conjunctival inflammation with purulent YELLOW d/c -tx systemically to prevent PNA x 6 mo. |
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| Viral conjunctivitis sx's |
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| -acute OR subacute onset (more often) -clear, watery d/c -pruritis common -often post URI |
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| Viral conjuntivitis causes |
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| -Adenovirus (esp in kids) -HSV1 (chronic, can progress to keratitis) -VZV |
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| Adenovirus distinguishing features |
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| -non enveloped virus -transmitted by respiratory secretions, fomites and contaminated pools -self limiting virus -may progress to kerato-conjunctivitis |
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| Keratitis sx's |
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| -Pain -Photophobia -Blurred Vision -Redness |
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| HSV1 distinguishing features |
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| -enveloped virus -replicates in conrean epithelium -estbs latency in tirgeminal ganglia -one of the most frequent causes of blindness and conjunctivitis in the US |
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| Parasitic Eye Infection Causes |
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| -Acanthamoeba (Protozoan) -Onchocerca Volvulus (Helminth Nematode) |
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| Acanthamoeba distinguising features |
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| -Protozoan (cyst in environment and trophozoite in pt) -found in fresh, brackish, and salt water, humidifiers, soil and dust -aquired by direct contact, swimming or via contacts -common in US |
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| Keratitits and corneal ulcers caused by Acanthamoeba sx and dx |
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| -FB sensation -Severe pain -Photophobia -can dx by presence of trophozoits/cysts in corneal scrapings |
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| Chronic Granulomatous Amebic Encephalitis (subacute) |
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| -caused by Acanthamoeba -common in chronically ill -sxs for several weeks with a HA and AMS |
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| Filarial Worms general features |
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| -long/thread-like -inhabit lymph system and sub Q tissue -eggs are long and thin- microfilariae |
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| Onchocerca Volvulus distinguishing features/mode of infection |
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| -transmitted by Black Fly (in Africa mostly) -causes 'River Blindness' -fly bites host and injects larval form, adult worms develop and group together, form a fibrous nodule (mate inside and release 1000's of microfilariae p/day), eggs migrate into cornea, leave nodules on trunk, limbs and head while migrating -vascular changes in eye causing inflammation and blindness |
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| Onchocerca Volvulus sx's |
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| -dermatitis/pruritis -skin looses elasticity (wrinkled) -eye lesions/blindness |
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| Trachoma sxs |
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| -caused by C. Trachomatis -early: inflammatory changes in cornea and mucopurulent d/c -late/re-infections: corneal abrasions, scarring, eyelid deformities and blindness -keratoconjunctivitis |
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| Trachoma dx |
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| -clinical appearance (follicles under eyelid) -group specific serovar testing from eye secretions and blood -immunofluorescence -PCR based assay |
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| Folliculitis/Furunculitis |
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| -External Ear infection caused usually by S. Aureus -acute/focal abscess formation in hair follicle |
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| Diffuse Otitis Externa |
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| -Swimmer's ear -diffuse external ear infection -develops as a result of excessive moisture and elevated pH which is hospitable to P. Aerunginosa |
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| P. Aerunginosa distinguishing features |
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| -Gram Negative Bacilli -Aerobic -Motile with single flagella -Oxidase positive -Sweet/grape odor-opportunistic- CF pts -live in the environment, can colonize URT and GI tract |
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| P. Aeruginosa virulence factors |
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| -Extracellular Slime; alginate -Hemolysins -Exotoxin A (causes local effects only- cell death) -Elastase: inactivates IgA, IgG, complement and targets elastin in lungs and BV |
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| Otitis Media features |
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| -follows URI, common in kids -often caused by various viruses, S. PNA, H. Influenzae Type B |
