Test Answers on Micro test 3 – Flashcards
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| TERM |
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| DEFINITION |
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| EXAM 3 - Etiologic Agents of Infectious Disease |
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| infectious disease by organ system Gram-positive rods Gram-positive cocci Gram-negative rods Gram-negative cocci Obligate intracellular pathogens Fungi |
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| How do you get conjunctivitisAka "pink eye" |
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| most commonly due to an infection (either viral or bacterial) or allergies can accur as a symptom of upper respiratory tract viral infection (common cold, sore throat) Sx: inflammation of the eye conjunctiva |
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| Where and how do you get keratitis? |
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| predominately by viral (but also bacterial) infection, e.g. herpes simplex virus the cornea becomes inflamed Sx: moderate-intense pain, often w/ impaired eyesight deep keratitis can be scar-forming |
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| Is retinitis caused by bacterial or viral agents? |
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| Viral Sx: night blindness can proceed to tunnel vision, ultimately producing blindness in middle-age |
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| All infections of the eye are due to ___ |
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| FPs |
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| How do you get otitis externa (OE)Aka "earache" |
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| an infection of the outer ear canal due to trapped water inflammation can be secondary to bacterial or fungal infection, often painful |
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| Where do you contract myringitis? |
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| tympanic membrane of the ear |
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| How and who gets otitis media w/ effusion? |
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| irritants or viral infections or allergic reactions of nasal passages cause inflammation of inner ear and the eustachian tubes (which normally sweep mucous up and out) leading to accumulation of thick secretions bacteria are then able to ascend up the inner ear cavity, produce overgrowth OME = a biofilm |
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| What is the most common sinusitis? |
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| maxillary (either viral or bacterial NF & FPs) antecedent evens cause inflammation, accumulation, blockage overgrowth |
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| What seems to be the general course of pathogenesis for bacterial infections of bady cavities? |
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| (1) some antecedent event (2) inflammation (3) accumulation (4) blockage (5) overgrowth 3, 4, 5 may occur simultaneously? |
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| How do you get rhinitis and why do symptoms manifest? |
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| commonly caused by bacterial or viral agents of the upper respiratory tract production of acute inflammatory mediators (immune response, vasodilation, excess mucous, inflammation) are primarily responsible for signs and symptoms (irritation, sneezing, rhinorrhea, leakiness, nasal congestion) Infectious rhinitis = rhinorrhea (runny nose) Allergic rhinits = clear discharge, swelling |
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| How does bacterial growth produce dental caries? |
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| bacteria form biofilm (plaque) on teeth that calcifies (calculus/tartar) and ferment sugar the lactic acid solubilizes and demineralizes the enamel, producing caries - a chronic, slowly progressive, and not self-limiting disease |
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| What is the difference b/w gingivitis and periodontitis? |
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| in gingivitis, biofilm (plaque) buildup becomes calcified and produces inflammation of the gingiva (aka "gums") periodontitis involves deeper tissue levels, of periodontal bone and ligament, and may result in teeth loss |
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| Where does stomatitis occur? |
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| in the mucous linings of the mouth, oral cavity incl. tongue severe iron deficiency, or B-vitamin deficiency, can result in stomatitis the diploid fungus Candida Albicans causes "thrush" on the tongue |
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| Where does glossitis present? |
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| on the tongue (alone) may become swollen and block airways (medical emergency) can be caused by iron deficiency, B-vitamin deficiency, or colonization by Candida Albicans (aka "thrush") |
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| Where does parotitis present? |
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| in the salivary gland |
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| Are infections/inflammations of the mouth and oral cavity due to NF or FP |
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| NF overgrowth of normal flora |
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| In respiratory tract RTI, what is more likely the cause - NF or FP? |
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| FPs predominately but also could be oral NF bacterial, viral, fungal, or less commonly protozoal |
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| How do you get diphtheria? |
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| bacterial exotoxin serious infection upper RTI caused by Corynebacterium diphtheriae Sx: sore throat, fever, sometimes myocarditis, sometimes neuropathy swelling can close off airways (req. tracheotomy) |
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| Where does pertussis manifest? |
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| in the bronchial tree highly contagious bacterial disease caused by Bordetella Pertussis Sx: severe chronic "whooping" cough |
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| Pneumonitis |
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| inflammation of lung tissue (alveoli) common cause of death among elderly |
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| What is the etiology of lower RTI (e.g. bronchitis, influenza, pneumonitis, pertussis) |
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| allergens, chemicals immune-mediated, or autoimmune infection |
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| Where and how does influenza manifest? |
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| viral infection of the bronchial tree, lower RTI Sx: fever, sore throat, muscle pains, severe headache, coughing, weakness/fatigue |
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| How does bronchitis develop? |
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| inflammatory condition w/o reference to infection incl. bronchitis, bronchiolitis, chronic bronchitis, chronic obstructive pulmonary disease although, inflammation causes further complications (one of the leading causes of death) and acute exacerbations can come in the form of bacterial/viral infection |
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| Croup |
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| viral infection of the trachea primarily in younger children Sx: swelling, "barking" cough, stridor |
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| What are the different types of pneumonia we discussed? |
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| Lobar (consolidation) pneumonia aka "typical" pneumonia: agent colonizes alveolar lining, multiplication, WBC infiltration, displacement Interstitial pneumonia aka "patchy" or "atypical" or "walking" pneumonia: agent replicates in interstitium, fluid accumulation, inflammation here |
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| Cavitary lesions aka lung abscess |
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| necrotizing abscesses caused by microbial infection form a hole in lung tissue that does not grow back often with aspiration, alcoholism |
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| How do you get pneumonia? |
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| viral, bacterial, fungal, protozoan infectious etiology inflammation and immune response ensures there is fluid accumulation in the alveoli caused by Strept. Pneumonia (50% of the time) Sx: breathing problems, fever, cough, chest pain |
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| Tubercles aka organized granulomas aka solitary pulmonary nodule |
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| round nodules surrounded by parenchyma found in the lungs opaque due to calcification tubercles often develop as a result of infection by Mycobacterium tuberculosis (MTB): asymptomatic and latent |
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| What causes emesis (vomiting)? Diarrhea? |
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| ingestion of an enterotoxin aka exotoxin or via systemic immune response to infection diarrhea (liquid feces, increased fluid and electrolyte loss) is usually caused by these same enteroxtoxins |
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| How do you get colitis? |
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| in situ toxin formation leads to intestinal cell destruction and mucosal adherence, bleeding and pseudomembrane formation (necrotic cells, PMNs, monocytes, RBCs) Sx: pain of lower abdomen and rectum |
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| What is tenesmus a symptom of? |
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| dysentery tenesmus = strained, painful defecation w/ little fecal matter actually excreted you can also get mucus/bloody stools and pain in dysentery |
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| What is the POE for GIT? |
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| tissue invasion occurs in stomach or intestine for gastrointestinal infections bacterial agents that cause bacteremia though usually enter through the large intestine |
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| Guillain-Barre'-Syndrome |
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| immune response to foreign antigen is directed at host tissue instead autoimmune attack on PNS myelin often seen as a complication of GIT most commonly caused by Campylobacter Jejuni Sx: autoimmune ascending flaccid paralysis |
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| Hemolytic-Uremic Syndrome (HUS) |
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| a toxemia (exotoxoin in the blood) where the toxin targets endothelial cells of GIT and kidney predominately affects children the "HUS triad" to look for one week after onset of diarrhea (e.g. infectious E. coli) includes: (1) hemolytic anemia via RBC lysis (2) acute renal failure via toxin action (3) thrombocytopenia, failure to clot, bleeding also can have CNS complications |
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| Which UGTIs we discussed are STDs? |
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| Pyelonephritis, Cystitis, Vaginitis = not an STD Urethritis, Cervicitis = STDs |
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| As a result of an STD agent, what are the Sx of urogential tract infection? |
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| genital ulcers (3 FP agents) papilloma (1 FP agent) |
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| How does one contract meningitis? |
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| meningeal inflammation can be caused by infection (bacterial ; fungal are more serious than viral) or less commonly by drugs the etiologic agent grows in the CSF subarachnoid space, edema, reduced cerebral blood flow, inflammation, irritation which elicits a protective response (Nuchal rigidity) |
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| What are the symptoms of meningitis? |
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| meningeal inflammation Sx: stiff neck, headache, fever, vomiting, petechiae, can result in cranial nerve injury, hypoxic-ischemic brain damage, catastrophic FX |
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| What are the four major phyla of fungi? |
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| Zygomycetes (sexual spores: zygospores) Basidiomycetes (external spores: basidia) Ascomycetes (internal spore sac: ascus) Deuteromycetes (no known sexual state) |
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| How do saprophytes obtain nutrients and energy? |
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| from dead plants and animals in soil and water |
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| How are fungi different from bacteria at the cellular level? |
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| Fungi are eukaryotic They have a nucelus (or many) with a nuclear membrane, also have organelles (e.g. ER, mitochondria, 80S ribosomes) They can reproduce sexually or asexually ; fungi have cell membranes that contain ergosterol (analogous to cholesterol in mammals), which makes ergosterol a common target for antifungal drugs like Amphotericin B |
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| Blastoconidia |
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| Yeast that reproduce asexually produce blastoconidia via budding |
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| Which species of yeast has a rigid polysaccharide capsule surrounding it? |
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| Cryptococcus this capsule helps explain some of its pathogenicity (cryptococcosis) |
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| Yeast |
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| Yeast make up only 1% of fungal species but they are unique b/c they are unicellular and mostly produce asexually (via budding: blastoconidia) some species of yeast (e.g. Candida) elongate into chains called pseudohyphae. Candida is responsible for the oral and vaginal infections, known as candidiasis or simply "yeast infection", in humans |
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| Germ tube |
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| unconstricted tubular outpourings observed in germinating yeast and spore-forming fungi A germ tube test is a diagnostic microscopy tool commonly used to confirm the presence of Candida Albicans |
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| Do yeast reproduce sexually? |
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| Some species do, form ascospores (internal sacs) or basidiospores (external spores) |
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| Mold |
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| molds are fungi that grow in multicellular filaments: hyphae they form fluffy, cottony colonies ; their cell wall consists of carbohydrate, chitin, chitosan, glucan and mannan |
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| Pseudohyphae |
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| yeast can form pseudohyphae as a result of incomplete budding |
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| mycelium |
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| a mass of intertwined hyphae, sometimes called shiro it is through the hyphae that fungus absorbs nutrients they can be huge - one site in Oregon identified a contiguous mycelium growth 2,400-acres in size (1,665 football fields) |
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| Diferent types of hyphae |
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| Hyphae can be vegetative: growing adjacent/into the substrate submerged: underground for nutrient absorbtion ; food acquisition aerial: extend above substrate (pictured) w/ fruiting bodies giving rise to spores/conidia demiatiaceaous fungi: contain black pigmented hyphae containing melanin |
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| Demiatiaceaous fungi |
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| have black-pigmented hyphae which contain melanin |
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| Asexual vs. Sexual reproduction in fungi |
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| Asexual: via mitosis, can form Sporangiospores (sporangium cleavage) or Conidiophores (hyphae differentiation) Sexual: via meiosis, can fuse two nuclei to form Zygospores, Ascospores, and Basidiospores just remember, "no sex on SportsCenter" "Zoo Animals Bone" |
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| What are the five thermally dimorphic fungi species that grow as mold/yeast? |
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| Blastomyces dermatiditis Histoplasma capsulatum Cocciodoides immitis Paracoccidoides brasiliensis Sporothrix schenckii "Historically, Spartacus Blamed Croccodiles from Paris to Brazil" |
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| Mnemonic for thermally dimorphic fungi |
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| "Historically, Spartacus Blamed Croccodiles from Paris to Brazil" Histoplasma capsulatum, Sporothrix schenckii, Blastomyces dermatiditis, Cocciodoides immitis, Paracoccidoides brasiliensis |
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| How do fungi find entry into humans to cause disease? |
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| either by inhalation (of spores) or by traumatic introduction into tissue it is thought their ability to cause disease is an accidental phenomenon for fungi, though (175 species out of hundreds of thousands) |
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| What temperature range do fungi like to grow at? |
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| most fungi are mesophilic ; prefer mild temperatures between 20-45*C which is below that of the average human body |
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| What is the best defense against fungal infection? |
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| cell-mediated immunity |
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| How virulent are fungi? |
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| Relatively low virulence in fungi which helps explain why disease/infection often occurs in debilitated immunocompromised hosts |
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| Dermatophytes |
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| type of fungi: feed off keratin in hair, skin, nails they include the following (3) genera: Epidermophyton Microsporum Trichophyton dermatophytes do not usually invade host tissue, but rather colonize the outer layer of skin (epidermis) these are the most common fungal infections in man (ringworm, tinea, "jock itch") "Microsporum no nails, Epidermiphyton no hair, Trichophyton everywhere" "you can't spell Dermatophytes without E-M-T" |
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| KOH stain |
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| A quick, inexpensive fungal test to differentiate between dermatophytes and Candida albicans from other skin disorders (psoriasis, eczema) Normal (negative) result = no fungi Septate, segmented hyphae = possible ringworm Spore-formers show arthroconidia Tinea versicolor shows curved hyphae Yeast cells are round, oval, budding |
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| Calcofluor white stain |
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| binds strongly to cellulose and chitin (found in fungal cell walls, as well as yeast buds) Calcofluor is also the dye used in white-colored clothing which fluoresces under "black-lighting" |
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| Periodic Acid Schiff (PAS) stain |
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| used to detect glycogen and polysaccharides, stains fungal elements (hyphae ; yeast) with a purple-magenta color (picture: esophageal candidiasis) |
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| Wood's lamp |
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| a diagnostic tool used in dermatology to identify/diagnose fungal infections (via UV light) |
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| Lactophenol cotton blue |
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| simple stain for the microscopic identification of fungi organisms in the slide mount stain are killed by the high concentration of phenol |
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| Pitaryiasis versicolor |
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| a chronic, mild mycosis of the stratum corneum Sx: tiny spots (on chest, abdomen, upper limbs, back) eventually grow in size forming branny, discolored or depigmented lesions Risk Fx: poor health, chronic infections, excessive sweating, pregnancy Dx: Wood's Lamp (fluoresces golden-yellow) or KOH stain (shows clusters of round, budding yeast, short branching hyphae) |
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| What fungi species causes Pitaryiasis versicolor? |
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| Malassezia furfur which is NF of the skin "malasSEZIA b/c tiny spots on chest/back grow in SIZE to depigmented lesions" "FURFUR b/c it FLUOResces golden-yellow under Wood's Lamp" |
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| Tinea nigra |
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| a superficial mycosis of the stratum corneum caused by dermatiaceous fungi usually, a tropical disease in equatorial regions Sx: painless macules on palms of hands Dx: KOH stain (shows brown, branching septae ; budding yeast) |
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| mycosis |
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| fungal infection |
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| What fungi species of fungi causes Tinea nigra? |
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| Hortaea (exophiala) werneckii which is dermatiaceous (black pigmented hyphae containing melanin) Dx: Hortaea werneckii stains brown and shows multiple hyphae and budding yeast on KOH stain |
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| Piedra |
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| fungal infection of the hair shaft Sx: irregular nodules |
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| White piedra vs. Black piedra |
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| White piedra: softer granule caused by Trichosporon "white trash" Black Piedra: hard, darkly colored, varies in size caused by Pedraia hortai "black president" |
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| Where do you find dermatophytes? And what families are responsible for human disease |
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| combs, brushes, theater seats, hats they can be anthropophilic (human reservoirs) or zoophilic (animal carriers) or geophilic (live in soil) Microsporum = no nails Epidermiphyton = no hair Trichophyton = everrrrywhere |
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| Tinea capitis |
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| cutaneous mycosis of the head, scalp, eyebrows caused by Microsporum or Trichophyton Sx: itching, dandruff, hair breaks off, leaving patches Dx: KOH mount or Wood's Lamp (in which Microsporum spp. Fluoresce green) |
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| Ecothrix vs. Endothrix |
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| differential types of Tinea Capitis Ecothrix = forms mycelia and conidia around hair shaft, destroys the cuticle usually resolves, but spreads to other tissues "grey patch ringworm" Endothrix = within the hair shaft, no cuticle destruction, esp. from T. tonsurans tendency to become chronic "black dot ringworm" |
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| Tinea corporis |
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| cutaneous mycosis of the body most commonly from Trichophyton rubrum and Trichophyton mentagrophytes Sx: horny layers of skin that spread hair follicles act as reservoirs |
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| Tinea cruris |
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| cutaneous mycosis of the groin usually tropical regions, more in males in the US, most commonly caused by T. rubrum Sx: severe itching |
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| Tinea unguium |
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| cutaneous mycosis of the nails is the form most resistant to treatment Organism: T. rubrum Sx: brittle, yellow crumbly nails |
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| Tinea pedis |
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| cutaneous mycosis of the feet aka "Athlete's Foot", common in institutions can become chronic, drug-resistant Organisms: T. rubrum, T. mentagrophytes, E. floccosum Sx: small vesicles form and rupture |
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| Tinea barbae |
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| cutaneous mycosis of the beard Organisms: T. mentagrophytes, T. rubrum |
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| Tinea manuum |
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| cutaneous mycosis of the hands Organisms: T. rubrum, T. mentagrophytes, E. floccosum |
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| Subcutaneous mycosis |
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| involves the dermis, subcutaneous tissues, muscles and fascia |
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| Sporotrichosis "Rose gardener's disease" |
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| subcutaneous mycosis involving traumatic inoculation into the skin mostly tropical, especially farmers and gardeners Organism: the dimorphic fungus Sporothrix schenckii Sx: nodular skin lesions that ulcerate, pulmonary can be inhaled, can spread in immunosuppressed pt's to form disseminated sporotrichosis Dx: culture, biopsy (cigar-shaped yeast) "sporo :: sporo" |
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| How is the dimorphism of Sporothrix schenckii evident in sporotrichosis? |
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| S. schenckii goes from colonies of hyphae at room temperature to forming cigar-shaped budding yeast at body temp (which can be seen after culture and biopsy) |
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| Opportunistic mycosis |
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| take advantage of immunocompromised host greatly increased w/ organ transplants, radiation therapy and AIDS |
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| What three fungi families are mainly responsible for opportunistic infections? |
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| Candidiasis Aspergillus Rhizopus/Absidia/Mucormycosis Cryptococcus "What an opportunity - CARCAM!" |
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| Candida: NF or FP? |
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| many species are NF |
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| Candidiasis |
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| Candida yeast can enter through any break in the skin, overgrowth of the fungus results in disease (so cell-mediated immunity is key) to infect, C. albicans transforms from unicellular yeast to invasive multicellular filament Sx: thrush (white patches on tongue), candidal vaginitis (itchy cottage cheese), chronic mucocutaneous candidiasis (skin, hair, nails ; mucous membrane infection), or can become disseminated candidiasis (kidney, braine, myocardium, eye) |
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| How do you identify Candida albicans? |
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| Germ tube (+) pseudohyphae blastoconidia |
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| What cells play an important role in suppressing Candidiasis infection? |
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| PMNs, monocytes, eosinophils, dendritic cells ; lymphocytes play an important role this helps explain why patients who are immunosuppressed or have T-lymphocyte dysfunction may end up with chronic mucocutaneous candidiasis |
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| Indwelling catheters are a contributing factor for |
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| Candidiasis infection (probably more) |
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| Why would extended antibiotic use be a contributing factor of Candidiasis? |
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| b/c many Candida sp. are NF |
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| What is in the "pseudomembrane" of thrush? |
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| it's composed of Candida cells, epithelial cells, WBC, food debris, necrotic tissue, bacteria all lumped together in white curdlike patches on tongue prevalent in pt's on inhaled steroids for asthma and AIDS patients |
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| What is the most common cause of vaginits? |
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| Vaginal candidiasis Sx: thick cottage cheese, severe itching Risks: diabetes, pregnancy, antibiotic Rx |
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| What increases risk of disseminated candidasis? |
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| neoplasms, burns, transplants, low birth weight dissemination to kidney, brain, myocardium produces high mortality (~40%) |
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| What is the usual POE for Aspergillus? |
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| inhalation of conidia |
