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58 Cards in this Set
- Front
- Back
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Staphylococcus aureus---Microbiology
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– Gram-positive cocci that grow in clumps or groups
– Non-motile – Facultative anaerobe – Catalase positive – Small white colonies on blood agar – S. aureus • Coagulase positive • Grows as golden, β-hemolytic colonies on blood agar |
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Staph Aureus- Epidemio
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– Part of the normal flora of the nose, skin, vagina, axilla, perineum, and oropharynx
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Staph Aureus--Pathogenesis
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– Evasion factors
• Capsule – anti-phagocytic • Protein A – binds IgG with high affinity • Carotenoids - neutralizes oxygen free radicals • Catalase – detoxifies hydrogen peroxide • Coagulase – creates fibrin coat on cell to protect from phagocytosis – Superantigens • Toxic Shock Toxin – strongly mitogenic for T lymphocytes – Toxins • Exfoliative toxins – binds cell membrane gangliosides in the stratum granulosum of keratinized epidermis • Alpha-toxin –pore-forming cytolysin |
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Protein A
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binds IgG w/ high affinity for S. aureus
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Coagulase
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creates fibrin coat on cell to protect from phagocytosis--s.aureus
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Toxic Shock Syndrome
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S. aureus
• Sudden onset of fever, chills, vomiting, diarrhea, muscle aches, and rash • Rapidly progresses to severe hypotension and multisystem dysfunction • Desquamation of palms and soles 1-2 weeks after onset • 1-2/100,000 women 15-44 years old • 5% of cases are fatal • Associated with use of tampons and intravaginal contraceptive devices • Complication of postoperative wound infections, particularly nose surgery |
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Scalded Skin Syndrome
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S. aureus
• Also known as Ritter disease or staphylococcal epidermal necrolysis • Acute exfoliation followed by erythematous cellulitis • Caused by exfoliative toxin produced by ~5% of S. aureus • Separation of the epidermis beneath the granular cell layer • Toxin targets desmoglein-1 • In neonates and children; morbidity ~1-5% • Immunocompromised adults |
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Folliculitis
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S. aureus
• Coagulase + staphylococci • Small pustule pierced by hair shaft; may be superficial or deep • Scalp and other hair portions of body |
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Furuncle
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S. aureus
• Infection of a single follicular unit • Fluctuant, erythematous lesion • Yellow, pointed area on surface • Pus and necrotic tissue extruded • Buttocks, axillae, neck, face, waist |
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Carbuncle
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S. aureus
• Multiple follicular units |
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Methicillin resistant Staphylococcus aureus
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– Resistant to almost all antibiotics except vancomycin
– Mechanisms of resistance: • Expression of a novel PBP2 with lower penicillin- binding affinity • Coded for by a large stretch of foreign DNA in the chromosome = mec element |
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Hospital acquired MRSA
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• Isolated from inpatients within 48 hours of admission
• Limited strain diversity |
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Community acquired MRSA
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• Specific version of mec
• Pantone-Valentine leukocidin • Narrower drug resistance pattern • Generally seen in healthy individuals • Spread within families and close contact groups |
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mec element
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novel PBP2 with lower penicillin binding affinity is coded for by this large stretch of foreign DNA in the chromosome of MRSA
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Streptococcus pyogenes--Microbiology
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– Gram-positive cocci that grow in chains
– Non-motile – Facultative aerobe – β-hemolytic when grown on blood agar – Also called Group A streptococcus |
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Strep Pyogenes--Epidemio and Pathogenesis
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• Epidemiology
– Colonizes the mouth, throat, and upper respiratory tract Pathogenesis: Antiphagocytic factors • M protein • Capsule • C5a peptidase Superantigens • SpeA • SpeB – LTA (lipotychoic acid) |
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Scarlet Fever
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Strep pyogenes
• Characterized by a diffuse red rash made up of tiny red bumps • Looks like sunburn and feels like sandpaper • Begins on chest and stomach, but can spread anywhere • After rash, skin on tips of fingers and toes may peel • Strawberry tongue • Transmitted via inhalation of aerosols |
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Impetigo
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strep pyogenes
• Small, erythematous macule that evolves into vesicles beneath stratum corneum • Ruptures leaving a honey-colored crust • Most frequently in children; adults with poor hygiene • Contagious in infants • Most commonly on face |
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Ecthyma
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Strep pyogenes
• Deeper versio of impetigo • May be a sign of gram-negative sepsis • Erosion of epidermis = ulcerated, crusted lesion • Common on legs • Children more susceptible • May be confused with bite of brown recluse spider |
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Ecthyma--s.pyogenes
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Erysipelas--s.pyogenes
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Erysipelas
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strep pyogenes
• Peripherally spreading, infiltrated, erythematous sharply circumscribed plaque • Lesion is warm • Face, scalp, hands, genitals • Susceptibility increases with poor hygiene and trauma |
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Borrelia burgdorferi--- Microbiology
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– Less finely coiled spiral bacterium
– 7-14 flagella at both ends for corkscrew motility – Similar to Gram-negative bacterial cell wall without LPS – Cell wall rich in lipoproteins – 2 atypical glycolipids = cross-reactive with gangliosides – 1 linear chromosome = 1 mega base with several circular and linear plasmids |
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Borrelia burgdorferi--Pathogen
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Surface proteins expressed at different times:
– OspA – OspC – OspE – VlsE--antigenic variation, may switch version of gene being expressed causing immuned system to not respond |
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Lyme Disease
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B. burgdorferi--
• Reservoir = white-footed mouse and deer • Vector = deer tick (nymph) • Humans = accidental host • 3 phases |
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Phase 1 of Lyme Disease
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Phase 1 = skin
• Bacteria inoculated into lower layers of skin • Spreading annular rash (erythema migrans) caused by inflammation • Easily treated with antibiotics |
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Phase 2 of Lyme Disease
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Phase 2 = invasion of bloodstream and dissemination
• Diffuse flu-like symptoms • Reaches joints and causes arthralgias • Reaches nervous tissue |
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Phase 3 of Lyme Disease
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Phase 3 = dormancy
• Lowered metabolic activity • Protected within cells (of immune system) or joint fluid • Chronic Lyme disease = fatigue, arthritis, neurologic damage, and vision impairment • Difficult to treat with antibiotics |
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Mycobacterium leprae
• Microbiology |
– Acid-fast bacterium; may appear faintly Gram-positive
– Grows within skin histiocytes and endothelial cells and Schwann cells of peripheral nerves – Slightly curved or straight rods – Very slow growth |
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Mycobacterium Lepra--Epidemio
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– Found in 9-banded armadillos, chimpanzees, and mangabeys
– Leprosy (Hansen’s disease) = humans only – Transmission related to overcrowding and poor hygiene – Transmission via direct contact and aerosol inhalation – Minimal number of organisms shed through skin – Not highly contagious; requires prolonged contact |
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Tuberculoid Leprosy
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• Blotchy red lesions with anesthetic areas of face, trunk, and extermities
• Thickening of peripheral nerves • Repeated trauma and secondary bacterial infections due to anesthesia • Cell-mediated immune response leading to destruction of bacteria and exaggerated allergic response • Better prognosis |
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Lepromatus Leprosy
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• Loss of eyebrows, thickening and enlargement of nostrils, ears, and cheeks resulting in leonine appearance
• Progressive destruction of nasal septum • Destruction of nasomaxillary facial structures • Damage to nerves resulting in repeated trauma of hands and feet; possible of digits • Weak cell-mediated immune response |
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Poxviruses--virology
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– Poxviridae = dsDNA genome with complex nucleocapsid
– +/- envelope – Brick or ovoid shape – Largest of viruses – Unique in that replication takes in the cytoplasm – Transmission via direct contact with skin lesion |
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Poxvirus--manifestations
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Smallpox, cowpox, monkeypox
• Smallpox eradicated in 1979 • Vaccinia virus = live vaccine for smallpox • Cowpox and monekypox = vesicles similar to smallpox Molluscum contagiosum • Mild infection with nodular lesions • Transmitted between |
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Papilloma Virus--virology
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– Papovaviridae = dsDNA genome with icosahedral or circular nucleocapsid
– At least 100 genotypes – Transmission via direct skin to skin contact or indirect contact |
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Papilloma virus--pathogenesis
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– Infects epithelial cells
– Local multiplication results in a wart after 1-2 months incubation – Warts may regress, but viral DNA remains in epithelial cells and can reactivate |
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Papilloma Virus--manifestations, dx, and treatment
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Manifestations
– Warts on skin and genitals – Sexually transmitted warts increase risk of cervical cancer Diagnosis – Diagnosis via inclusion-bearing cells (koilocytosis) and viral DNA detection via PCR Treatment – Vaccine available = Gardasil |
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All about Blastomyces dermatidis
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• Mycology
– Dimorphic fungus; deep mycosis – Transmission via inhalation of air-borne spores • Epidemiology – Areas surrounding river banks are natural habitat • Pathogenesis – Invasion through lungs and then disseminates throughout body • Manifestation – Can be confused with tuberculosis • Diagnosis – Yeast cells in sputum or skin lesions |
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Cryptococcus neoformans---mycology
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– Encapsulated yeast-like fungus
– Transmission via inhalation of air-borne cells – Found in soil |
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Cryptococcus neoformans--manifestations and dx
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Manifestations
– Influenza-like disease or pneumonia – Meningitis in immunocompromised patients Diagnosis – Isolation of encapsulated yeast in sputum or CSF |
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Sporothrix schenckii--Mycology
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– Dimorphic fungus found in environment
– Transmission by direct contact of fungus with wound |
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Sporothrix schenckii--manifestations and dx
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Manifestation
– Is superficial mycosis, but can invade subcutaneous tissues – Known as “rose gardener’s disease” Diagnosis – Identification of budding cells in inflammatory exudate from lesion |
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Propionibacterium acnes--all
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• Microbiology
o Anaerobic Gram-positive bacillus in chains o Part of normal flora of hair follicles • Pathogenesis o Acts on sebum to form fatty acids and peptides leading to inflammation • Manifestations o Comedomes = greasy plugs of keratin, sebum, and bacteria |
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Coxsackievirus--all
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Virology
---Picornaviridae = + sense ssRNA icosahedral virus ---Transmission via respiratory droplets • Epidemiology ---Generally seen in young children • Manifestations ---Herpangina (blisters on mouth, hand, and foot) |
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Herpes Simplex Virus--Virology
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– Herpesviridae = enveloped dsDNA icosahedral virus
– Transmitted via saliva, vesicle fluid, sexual contact, birth canal (neonate) |
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Herpes Simplex virus--pathogenesis
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– Intraepithelial vesicular lesions on mouth, skin, and genitals
– Axonal travel to latency sites in sensory ganglia – Can reactivate |
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HSV--manifestations 1 vs 2
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HHV-1 = HSV-1
• Gingivostomatitis and cold sores HHV-2 = HSV-2 • Genital herpes, cutaneous herpes |
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Varicella Zoster virus--virology
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– Herpesviridae = enveloped dsDNA icosahedral virus
– Transmitted via respiratory droplets or vesicle fluid |
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VZV--Pathogeneseis
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– Axonal travel to latency sites in sensory ganglia
– Zoster is a reactivation |
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VZV--manifestations and treatment
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• Manifestations
– HHV-3 = varicella (chickenpox) and zoster (shingles) • Prevention/Treatment – Vaccine available |
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Leishmania--microbio, epidemio, and path
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PARASITE
Microbiology – Leishmania species – obligate intracellular parasite – Tissue flagellate • Epidemiology – Transmitted by sandfly bites • Pathogenesis – Live intracellularly in macrophages in amastigote form |
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Leishmania--manifestations and dx
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– Cutaneous leishmaniasis = Leishmania major and L. tropica
• Starts as small papule and progresses to localized ulcers • Heal spontaneously with massive scarring • Immunocompromised = diffuse cutaneous similar to LL – Mucosal leishmaniasis = L. braziliensis • Progressive invasion of mouth and nose Dx: in vitro culture of tissue specimen |
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Leishmania
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Ancylostoma and Nector--What are they
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PARASITES
– Nematodes Ancylostoma and Nector = human hookworms – Transmission via contact with soil contaminated with feces from animals containing eggs |
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Ancylostoma and Nector--pathogenesis and manifestations
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• Pathogenesis
– Invade through skin and larvae burrow through dermis • Manifestations – Cutaneous larva migrans – Leaves intensely itchy sinuous inflammatory trail – Eventually reach intestines |
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serpigenous rash-->hookworms
ancylostoma and nector |
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Onchocerca volvulus--What is it?
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PARASITE
– Filarial nematode = Onchocerca volvulus – Very long, thin worm as adult – Widely found in tropical and subtropical regions |
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Onchocerca volvulus--pathogenesis and manifestations
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• Pathogenesis
– Live in lymphatics or in subcutaneous nodules • Manifestations – Hypersensitivity (IgE) reaction causes skin lesions – Also causes river blindness |
