Exam 2 Flashcards
What are examples of pathogens that enter via the skin
- S aureus, Candida albicans, pseudomonas aeginosa via mechanical defects
- HIV, Hep viruses via needle sticks
- Yellow fever, plague, Lyme disease, malaria, rabies via animal bites
- schistosoma via direct penetration
What are examples of pathogens that enter via the GI tract
- vibrio cholerae and giardia via attachment and local proliferation
- shigella, salmonella and campylobacter via attachment and local invasion
- poliovirus via uptake through M cells
- Protozoa and helms
- hep A, rotavirus and norovirus (defense: pancreatic enzymes)
- Clostridium difficile
What are examples of infections that spread through nerves
Varicella zoster, rabies
What is an example of a microbe that spreads within inflammatory cells
M tuberculosis in macrophages
What are the host defenses against infection in each of the systems
Skin: tough keratinized barrier, low pH, fatty acids
Respiratory: alveolar macrophages, mucociliary clearance, IgA
GI: acidic gastric pH, viscous mucus, pancreatic enzymes and bile, defensins, IgA, normal flora
GU:repeated flushing and acidic environment created by commensal flora
What are examples of mechanisms of antigenic variation
- Hight mutation rate: HIV, influenza virus
- Genetic reassortment: influenza virus, rotavirus
- Genetic rearrangement: BOrrelia burgdorferi, neisseria gonorrhoeae, trypanosomiasis, plasmodium
- Large diversity of serotypes: rhinoviruses, strep pneumoniae
How do microbes resist phagocytosis
Producing a capsule
What are the viral STDs
- herpes simplex virus: primary and recurrent herpes, neonatal herpes
- Hep B
- HPV:cancer of penis, cervical and vulvar cancer, condyloma acuminatum in both females and males
- HIV
What are the bacterial STDs
- chlamydia trachomatis: urethritis, epididymitis and proctitis in males, urethral syndrome, cervicitis, bartholinitis, salpingitis in females, lymphogranuloma venereum in both
- Ureaplasma urealyticum: urethritis in males
- neisseria gonorrhoeae: epididymitis, prostatitis, urethral stricture in males, cervicitis, endometritis, bartholinitis, salpingitis, infertility, ectopic pregnancy in females, urethritis, proctitis, pharyngitis, disseminated infection in both
- Treponema pallidum: syphylis
- Haemophilus ducreyi: chancroid in both
- Klebsiella granulomatous: granuloma inguinal (donovanosis) in both
What are the Protozoa that cause STDs
-trichomonas vaginalis: urethritis, balanitis in males, vaginitis in females
What is an example of a microbe that causes purulent infection
Staphylococcal pneumonia
What are examples of microbes that cause tissue necrosis
Clostridium perfringens and hep B
What are the staining techniques used for different kinds of infections agents
- gram stain: bacteria
- Acid-fast stain: mycobacteria, nocardiae
- silver stains: fungi, legionellae, pneumocystis
- periodic acid schiff: fungi, amoebae
- mucicarmine: cryptococci
- giemsa: campylobacter, leishmaniae, malaria parasites
What are koplik spots
Ulcerated mucosal lesions in oral cavity seen in measles: marked by necrosis, neutrophilic exudate, and neovasculariziation
What are warthin finkeldey cells
Multinucleate giant cells found in the lymphoid organs in measles: have eosinophilic nuclear and cytoplasmic inclusion bodies; also found in lung and sputum
What are the corneal lesions caused by HSV
Herpes epithelial keratitis: virus induced cytolysis of superficial epithelium
Herpes stromal keratitis: infiltrates of mononuclear cells around keratinocytes and endothelial cells leading to neovascularization, scarring, opacification of cornea and blindness (caused by immune reaction, not HSV itself)
When does the chickenpox rash typically occur
2 weeks after respiratory infection
What is Ramsay hunt syndrome
If varicella zoster involves geniculate nucleus: causes facial paralysis
What is the frequent disease presentation of streptococcus pyogenes
Pharyngitis
What is the common disease presentation of vibrio cholerae and enterotoxigenic E. coli
Noninflammatory gastroenteritis
What it’s eh common disease presentation of shigella, salmonella, campylobacter jejuni, and enterohemorrhagic E. coli
Inflammatory gastroenteritis
What are the common disease presentations of ecoli, pseudomonas aeruginosa, enterococcus species in the GU tract
UTI
What does staphylococcus aureus cause in the skin
Abscess, cellulitis
What does steptococcus pyogenes cause in the skin
Impetigo, erysipelas, necrotizing fasciitis
What does clostridium perfringens cause in the skin
Gas gangrene
What does bacillus anthracis cause in the skin
Cutaneous anthrax
What are the effects of staphylococcal infection on different systems
Resp infection, toxic shock syndrome, osteomyelitis, skin infections (surrounded around hair follicle)-> boils and carbuncle, endocarditis, food poisoning *S aureus -> pyogenic inflammation
What is staphylococcal scalded skin syndrome
Called Ritter disease; usually in children with infection of nasopharynx of skin; sunburn like rash that spreads over entire body that can lead to skin loss
What is erysipelas
Caused by strep pyogenes; characterized by r avidly spreading erythematous cutaneous swelling
What is scarlet fever associated with
Strep pyogenes
Is listeria monocytogenes gram positive or negative
Positive bacillus
What is the classification of Bacillus anthracis
Spore forming gram positive rod shaped bacterium
What is the classification of pseudomonas aeruginosa
Aerobic gram negative bacillus
What is the difference between the ulcers/rashes formed by haemophilus ducreyi and klebsiella granulomatis
Klebsiella: painless
H. Ducreyi: painful
What do the masses formed by Klebsiella sometimes form
Urethral, vulvar, or anal strictures from scarring
What is unique about TB in immunocompromised people
Do not form granuloma a
What is the hallmark of mycobacterium avium in HIV patients
Abundant acid-fast bacilli within macrophages
What are the stages of the protean manifestations of syphilis
Primary: chancre
Secondary: palmar rash, LAD, condyloma Latum, neurosyphilis
Latent
Tertiary: Neurosyphilis (asymptomatic, meningovascular, tabes dorsalis, general paresis), aortitis (aneurysms, aortic regurgitation), gummas (hepar lobatum, skin, bone)
Contrast gram positive and negative bacteria
Positive: thick cell wall; envelope has outer cell wall of complex cross linked peptidoglycan
Negative: thin cell wall
What microbes found in the GI tract can also be spread by oral/anal sex
Shigella and E histolytica
What is the difference between erythema migrans, multiforme and marginatum
Migrans:single lesion
Multiform: multiple lesions
Marginatum: snake-like
Which group of strep is normal in GI tract
D
Which organisms cause necrotizing pneumonia
Rhodococcus equi, klebsiella pneumoniae, staphoreus
How does staphaureus become resistant to penicillin
Contains beta lacrimal which breaks it down
What is Waterhouse-friederichsen?
Caused by neisseria meningitis -> b/l adrenal hemorrhage
Which STI causes one joint arthritis if left untreated
Gonorrhoeae
Which microbe is associated with rose spots
Salmonella typhi
Which microbe is associated with Guillian-Barre
Campylobacter jejuni
Does haemophilus ducreyi cause a painful or painless ulcer
Painful
What is a characteristic of late stage syphilis
Dissecting aortic aneurysm
Describe the micro characteristics of staph aureus
Gram positive, catalase positive, coagulase positive, beta hemolytic, ferments mannitol
What is the virulence factor of staph aureus
Protein A->component of cell wall; binds Fc portion of Igs; prevents opsonization and phagocytosis
Where dose staph aureus colonize
Nares
What diseases does staph aureus cause
- ) inflammation -> pneumonia with patchy infiltrate, most commonly post viral infection; septic arthritis, impetigo, faruncles, boils, abscesses, rapid onset acute endocarditis *tricuspid valve, osteomyelitis *most common cause
- )toxin mediated dz: scalded skin syndrome (protease; skin peels off), TSS, rapid onset food poisoning (more vomiting)
- ) MRSA: alters penicillin binding protein
What does Staph epidermidis often infect
Artificial joints; indwelling Cath important source of infection; *endocarditis in artificial valves; normal skin flora; novobiocin sensitive; cat positive, urease positive, coagulase negative
What does staph saprophyticus cause
UTI in sexually active F; cat positive, urease positive, coagulase negative
Describe the micro characteristics of strep A pyogenes
Encapsulated made of hyaluronic acid which makes it non-immunogenic; beta hemolytic
What does strep pyogenes cause
Impetigo ‘honey crusted’; pharyngitis, cellulitis, erysipelas
- Rheumatic fever: M protein in cell wall *main virulence factor; interferes with opsonization; generates humoral response which makes abs to similar structure (myosin in heart) *mitral valve; ONLY after pharyngitis infections; Symptoms Joints (polyarthritis) O - heart problems, Nodules on forearms or knees, Erythema marginatum, Sydenham chorea: rapid involuntary movements
- post strep glomerulonephritis: type III rxn; dark brown urine, facial swelling, 2 wks after onset after pharyngitis OR skin infection, virulence: streptolysin O: lyse RBCs; streptokinase: convert plasminogen->plasmin, DNAase: depollymerize DNA
What are the infections caused by strep pyogenase toxin (SPE)`
- Scarlett fever: reddening and swelling of tongue (strawberry tongue), pharyngitis, widespread rash that spares face
- toxic shock - like syndrome
- necrotizing fasciitis: SpeB
What is strep agalactiae
Group B strep; meningitis in infants; + hippurate test (hydrolyzes sodium hippurate); poly sacc capsule; CAMP + *distinguishes from other strep -> arrowhead zone of hemolysis; beta hemolytic; swab vaginal canal at 35 wks and prevent with penicillin
Describe the micro characteristics of strep pneumoniae
Alpha hemolytic** (also strep viridans); partial hemolysis (outer has green hue); encapsulated (polysaccharide) *major virulence factor; optochin sensitive; diplococci; bile soluble
What does strep pneumoniae cause
Production of rust colored sputum, MOPS (meningitis, otitis media, pneumonia, sinusitis); virulence factor: cleaves IgA
Describe strep viridans
No capsule; optochin resistant; bile resistant; alpha hemolytic, associated with dental caries; affects damaged heart valves (adheres to fibrin aggregates and platelets)
Describe enterococcus
Inhabits intestines; 2 species: Faecalis *more common and Faecium *more serious; can grow in NaCl; 3 main infections: UTI, endocarditis, biliary tree infections *do you love trees?; nosocomial
What is splenomegaly usually associated with
Viral syndromes
What is a positive heterophil ab test diagnostic for
Mono; CMV can give negative test but still cause mono-like
Does mycoplasma hominis cause neutrophilic or lymphocytosis
Lymphocytosis because not acute pyogenic bacteria
What does the CSF in acute bacterial meningitis look like
Turbid color, increased opening pressure, decreased CSF glucose, increased protein *group B strep, ecoli, listeria, neisseria
Describe the features of bacillus anthracis
Gram positive bacilli; causes black Eschar (necrotic cutaneous lesion with surrounding erythematous ring); encapsulated -> made of protein *poly D glutamate; obligate aerobe; spore former
What are the toxins of bacillus anthracis
- lethal factor: exotoxin; protease that cleaves MAPK -> necrosis
- edema factor: adenylate cyclase increases cAMP -> fluid
- both need to be present to cause symptoms
Describe pulmonary anthrax
Starts with dry cough, progresses to hemorrhagic mediastinitis and widened mediastinum
Describe bacillus cereus
Gram positive bacilli; spore forming *food poisoning in reheated fried rice
Describe the features of clostridium tetani
Gram positive bacilli, obligate anaerobe, spore forming, found in soil, rigid paralysis; Risus Sardonicus *evil grin -> lock jaw; extension of back *opisthotonus; toxin - tentanospasmin -> travels retrograde to spinal cord; protease that cleaves SNARE and inhibits release of GABA and glycine *renshaw neurons
Describe the features of clostridium botulinum
Gramp positive bacilli; obligate anaerobe spore former; flaccid paralysis (descending) only peripheral nerves; cleaves SNARE -> attacks motor neurons that release Ach; *babies, think honey; causes floppy baby syndrome (ingestion of spores) in adults ingestion of preformed toxin
Describe the features of clostridium difficile
Gram positive spore forming nosocomial infection; clindomycin inducive to infection; exotoxins: A (bind to brush border and cause inflammation and cell death -> watery diarrhea) and B (depolymerizes actin -> enterocyte death and necrosis -> yellowish grey exudate that forms pseudomembrane covering colonic mucosa); diagnosis: toxin in stool; obligate anaerobe
Describe the features of clostridium perfringens
Gram positive bacilli, associated with military combat and motorcycle wounds; spore forming obligate anaerobe; causes gas gangrene (alpha toxin inhibits lecithinase and damages cell membrane; zone of double RBC hemolysis) and food poisoning (late onset diarrhea)
Describe the characteristics of corynebacterium diphtheriae
Gram positive bacilli; club shaped; metachromatic granules; exotoxin A (active: EF2) and B; inhibits ribosome function and formed pseudomembrane (gray in throat and tonsils -> LAD *bulls neck); resp transmission; causes myocarditis, arrhythmia and heart block; can demyelinate CN; diagnosis -> plate on telluride or Loeffler’s; diff btw toxic and non toxic -> eleks test
Describe the features of listeria monocytogenes
santa pic Gram positive bacilli; associated with pregnant women; beta hemolytic, motile, catalase positive, survives in cold, *milk, meat, cheese; newborns -> meningitis and in adults over 60
Describe the features of actinomyces Israeli
Gram positive obligate anaerobe; normal flora of oral cavity; infection associated with jaw trauma *dental work; begins as no tender lump on jaw that drains yellow pus
Describe the features of nocardia asteroides
western card game pic Gram positive obligate aerobe found in soil; acid fast satin *mycolic acids; catalase positive, urease positive, *seen in immunocompromised men more than women; 3 sites of infection -> pulm (pneumonia w cavitation), CNS (brain abscess), cutaneous (pyogenic response)
Describe the features of Neisseria overall
Diplococci gram negative; oxidase positive; cannot grow in blood agar; needs heat *chocolate agar; growth on VPN agar; virulence factors: pillus: allows attachment and genetic rearrangement; difficult to target; IgA protease
Describe neisseria meningitidis
Gram negative, spread in close quarters via resp droplets, ferments maltose and glucose, colonizes in nasopharynx, polysaccharide capsule *main virulence factor b/c inhibits phagocytosis; infections usually type B; sickle cell -> more susceptible; spreads via blood -> inflammation generated by LOS proteins in the envelope -> increases permeability -> hypovolemia -> vasoconstriction leads to adrenal insufficiency *waterhouse Fredrich syndrome; petechial rash (DIC)
Describe neisseria gonorrhoeae
Gram negative and invades PMNs; no capsule; males: urethritis, proctitis, orchitis; females: PID, white purulent discharge thicker than chylamydia; PID can spread to peritoneum (Fitz-Hugh Curtis syndrome; causes adhesions to liver); asymmetric polyarthritis; joint fluid that doesn’t gram stain (b/c intracellular); congenital -> purulent conjunctivitis (sooner onset than chlamydia)
Describe Klebsiella pneumoniae
Enteric gram negative bacilli; *UTI, pneumonia, nosocomial; ferments lactose; three A’s: alcoholics, abscesses, and aspiration; polysaccharide capsule; currant jelly sputum, immotile, cavitation lesions, urease postive
Describe enterobacter app and serratia mareasans
Both are motile gram negative bacilli that cause UTI, pneumonia and are nosocomial; serratia has a red pigment when cultured
Describe salmonella enteritidis
Gram negative bacilli, motile, black colonies, capsule, acid labile (easily degraded so need high concentration to cause infection) ie: more susceptible if use antacids; caused from raw chicken; infects macrophages in the colon; faculatative intracellular; causes inflammatory diarrhea; virulence: type III secretion system
Describe salmonella typhi
Gram negative motile bacilli; black colonies, acid labile, capsule; found in the GB of carriers; causes rose spots on the abdomen, number one cause of osteomyelitis in patients with sickle cell; constipation or diarrhea that resembles pea soup; type III secretion system
Describe Shigella
Gram negative bacilli; causes bloody diarrhea; green colonies; immotile, acid stable -> fewer organisms cause infection; M tropic -> invades; facultative intracellular; shigella dysenteriae: hemolytic uremic syndrome (although more assoc with E. coli) -> shigatoxin induces endothelial damage and aggregation of platelets causes a decrease in count; also bind s the 60S subunit and inhibits translation; type III secretion system
Describe E.coli in general
Gram negative bacilli; virulence factors: fibriae -> UTIs, ferments lactose, capsule (K antigen), catalase positive, LPS -> sepsis; *neonatal meningitis ONLY when positive for K antigen
Describe EHEC (hemorrhagic E. coli)
From undercooked meat; causes bloody diarrhea, only ecoli that doesn’t ferment sorbitol; toxin inhibits 60S (shiga-like toxin); causes hemolytic uremic syndrome; O157-H7 Ag linked to outbreaks
Describe ETEC (invasive)
*travelers diarrhea via drinking contaminated water; toxins: heat labile that increases cAMP and heat stable that increases cGMP; watery diarrhea
Describe yersinia enterolitica
Gram negative bacilli transmitted via dog poop; more common in kids (cause also be spread in milk), resistant to cold temps, bipolar safety pin staining; capsule; causes bloody diarrhea, fever, leukocytosis, abscesses, intusseception, perforation and can mimic appendicitis
Describe yersinia pestis
Black Plague; gram negative bacilli; reservoir: rats or prairie dogs; vector: fleas; causes buboes (swollen tender LN), abscesses and DIC from endotoxin; exotoxin and outer proteins use type III secretion system to inhibit phagocytosis
Describe campylobacter jejuni
Gram negative; associated with Gillian barre ascending paralysis; thermophilic, infects intestinal tract (Fecal/oral), causes bloody diarrhea, curved rod shape; oxidase positive; invasive -> reactive arthritis
Describe vibrio cholerae
Gram negative rod, comma shaped, fecal oral route; *does not invade; uses fibriae to attach to wall and secrete cholera toxin which increases cAMP by activated adenylate cyclase leading to increased H2O in lumen; acid labile; oxidase positive; non-cholerae vibrio is transferred via contaminated seafood
Describe H pylori
Gram negative, motile, curved rod, urease positive (reduces acidity and helps it invade) urea breath test, oxidase positive, causes duondenal ulcers
Describe psuedomonas aeruginosa
Gram negative rod, thrives in water *hot tub folliculitis (ecthyma gangrenosum), oxidase positive, catalase positive, blue/green pigment when plated b/c pyocynin; grape like odor; obligate aerobe; number one cause of nosocomial pneumonia; causes osteomyelitis in IV drug users and diabetics, capsule; *causes fatal complications in burn victims; indwelling cath -> UTI; otitis externa *swimmer’s ear; toxin: exotoxin A -> inactivates EF-2 by ribosylation
Describe proteus mirabilis
Gram negative facultative anaerobe, motile, urease positive which causes the formation of staghorn calciculi (kidney stones); UTI’s, fishy odor
Describe bordatella pertussis
Gram negative bacilli; spread by resp droplets which attach to epithelium via pilli(filamentous hemagglutinin) *doesn’t invade -> releases toxins -> pertussis toxin and andenylate cyclase-> ribosylates Gi -> increases cAMP; tracheal toxin ->part of peptidoglylcan wall, damages ciliated cells; initial infxn non specific; paroxysmal stage -> cough, convalescent stage lasts 3 months
Describe haemophilus influenzae
choc covered cherry pic Gram negative cocci-bacilli; grown on chocolate agar which needs factor V (NAD) and X (hematin); aerosol trasmission; causes pneumonia, cherry red epiglottitis with inspiratory stridor and drooling, otitis media, meningitis only when capsular form and type B strain; septic arthritis; asplenic more susceptible
Describe legionella pneumophila
battleship Gram negative but doesn’t stain well so need silver stain; grown on charcoal in presence of cysteine and iron; oxidase positive; causes legionnaires; Pontiac fever -> fever and malaise; atypical pneumonia: patchy infiltrate with consolidation in one lobe; *unique -> associated with hyponatremia, HA with confusion, and diarrhea; high fever; use rapid urine ag test or sputum culture
