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41 Cards in this Set
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Staphylococcus Aureus
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- beta hemolytic
- catalase and coagulase positive Virulence Factors: - protein A: binds to Fc portion of IgG -> prevents opsonization and phagocytosis (cannot expose C1 binding domain) |
Manifestations:
1) inflammatory dz: skin infxns, organ abscesses, pneumonia, osteomyelitis, acute bacterial endocarditis 2) toxin-mediated dz: rapid-onset food poisoning (enterotoxin), staphylococcal scalded skin syndrome (exfoliatin), toxic shock syndrome (TSST-1) - TSST-1 = superAg binding to MHC II and T cell receptor -> polyclonal T cell activation and release of IFNg and IL2 3) MRSA: nosocomial and CA; resistant to b-lactams due to altered PCN-binding protein |
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Staphylococcus Epidermidis
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- catalase positive
- coagulase negative - sensitive to novobiocin |
Manifestations:
- component of nl skin flora - infects prosthetic devices and IV catheters by producing adherent biofilms - contaminates blood cultures |
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Staphylococcus Saprophyticus
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- catalase positive
- coagulase negative - resistant to novobiocin |
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Streptococcus Pneumonia
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- lancet shaped
- a hemolytic (partial, green) - catalase negative - sensitive to optochin - bile soluble Virulence Factos: - capsule (positive quellung) = antiphagocytic - IgA protease -> cleaves IgA to colonize resp mucosa - can undergo transformation |
Manifestation:
- "rusty" sputum - pneumonia - meningitis - otitis media - sinusitis - sepsis in pts with sickle cell or s/p splenectomy |
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Streptococcus Viridans
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- a hemolytic (partial green)
- resistant to optochin - normal flora of oropharynx |
Manifestations:
- S. mutans: dental caries - S. sanguis: subacute bacterial endocarditis |
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Streptococcus Pyogenes
Group A |
- b hemolytic (complete, clear)
- bacitracin sensitive Virulence Factors: - M protein - helps prevent phagocytosis - Ab against M protein may cross react -> rheumatic fever - ASO titer to detect recent S. pyogenes infxn |
Manifestations:
1) Pyogenic: pharyngitis, cellulitis, impetigo 2) Toxigenic: scarlet fever, toxic shock-like syndrome (erythrogenic toxin) 3) Immunologic: acute glomerulonephritis, rheumatic fever (subcutaneous plaques, polyarthritis, erythema marginatum, chorea, carditis) |
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Streptococcus Agalactiae
Group B |
- b hemolytic (complete, clear)
- bacitracin resistant - produces CAMP factor -> enlarges area of hemolysis formed by S. aureus - colonizes vagina |
Manifestations:
- pneumonia, meningitis, sepsis mainly in babies -> screen pregnant women at 35-37weeks of gestation -> if positive give PCN prophylaxis |
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Enterococci
Group D streptococci |
- variable hemolysis, g hemolytic (no hemolysis)
- grow in 6.5% NaCl and bile - normal colonic flora - Lancefield grouping includes enterococci and nonenterococcal group D strep (same C carbohydrate on bacterial cell wall) |
Manifestations:
- resistant to PCN G - UTI and subacute endocarditis - can be vanc resistant |
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Streptococcus bovis
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- colonizes gut
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- bacteremia and subacute endocarditis in colon cancer
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Corynebacterium diphteria
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- club shaped
- gram positive with METACHROMATIC GRANULES (blue and red) - grows on tellurite agar Toxin A: - encoded by b-prophage - ADP ribosylation of EF-2 -> inhibits protein synthesis |
Manifestation:
- pseudomembraneous pharyngitis (gray-white) with LAD - toxoid vaccine to prevent diphtheria |
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Bacterial Spores
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Found in soil:
- C. tetani, C. perfringens, B. anthracis Also: - B. cereus, C. botulinum |
- form when nutrients limited (late stationary phase)
- spores highly resistant to destruction by heat and chemicals - contains dipicolinic acid in their core - no metabolic activity - autoclave at 121˚C for 15min to destroy them |
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Clostridium tetani
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- gram positive
- spore former - obligate anaerobe bacillus Toxin: - tetanospasmin - inhibits release of GABA and glycine from Renshaw cells in spinal cord |
Manifestations:
- spastic paralysis - trismus, risus sardonicus, ophisthotonic posturing |
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Clostridium botulinum
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- gram positive
- spore former - obligate anaerobe Toxin: - preformed, heat-labile (usually canned food, spores in honey) - inhibits release of ACh at NMJ - no vaccine, treat with antitoxin |
Manifestations:
- flaccid paralysis - diplopia, dysphagia, dysphonia w/in 12-24hrs of toxin consumption - Adults: caused by ingestion of preformed toxin - Babies: ingestion of bacterial spores (eg from honey) can cause dz |
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Clostridium perfringens
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- gram positive bacillus
- obligate anaerobe Toxin: - alpha toxi (lecithinase) acts as phospholipase -> causes myonecrosis and hemolysis - loss of membrane integrity |
Manifestations:
- gas gangrene - late-onset food poisoning with watery diarrhea Tx: - debridement of necrotic tissue and IV Abx |
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Clostridium difficile
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- gram positive bacillus
- obligate anaerobe Toxin: - toxin A = enterotoxin, binds to brush border and acts as PMN attractant - toxin B = cytotoxin, destroys cytoskeletal structure of enterocytes |
Manifestations:
- diarrhea - pseudomembraneous colitis usually after Abx tx (ampicillin, clindamycin) Dx and Tx: - detection of toxin(s) in stool - metronidazole |
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Bacillus Anthracis
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- gram positive rod
- spore former - POLYPEPTIDE capsule consisting of D-glutamate Toxin: - anthrax toxin: edema and lethal factor "woolsorter's dz" - inhalation of spores from contaminated wool |
Manifestations:
Cutaneous: - black eschar (necrosis) surrounded by edematous ring, painless - can progress to bacteremia and death Pulmonary: - inhalation of spores - flu-like sx - rapidly progress to fever, pulmonary hemorrhage, mediastinitis, shock |
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Listeria Monocytogenes
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- gram positive rod
- facultative intracellular - ingested from unpasteurized milk/cheese and deli meats - vaginal transmission during birth - form "actin rockets" to move from cell to cell and escape from immune attack |
Manifestations:
- amnionitis, septicemia, spontaneous abortion in pregnant women - granulomatosis infantisepticua - neonatal meningitis, meningitis in immunocompromised - mild gastroenteritis in healthy |
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Actinomyces israelii
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- gram positive
- filamentous branching - ANaerobe - normal oral flora |
Manifestation:
- oral/facial abscesses that may drain through sinus tracts in skin - sulfur granules that contain filaments in pus Tx: PCN |
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Nocardia asteroides
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- gram positive, mildly acid fast
- filamentous branching - aerobe found in soil -> respiratory route of infxn |
Manifestation:
- pulmonary infection in immunocompromised Tx: sulfa drugs |
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Leprosy
Hansen's dz |
Mycobacterium leprae:
- AFB with predilection for cool temps -> infects skin and superficial nerves - cannot be grown in vitro - reservoir: armadillos in US - transmission via respiratory route |
Manifestations:
1) Tuberculoid - intact T-cell response -> limited with few hypoesthetic skin nodules 2) Lepromatous - weak TH1 response - diffuse skin involvement, communicable - leonine facies: loss of eyebrows, nasal collapse, lumpy earlobe - diffuse skin thickening with hypopigmentation - paresis, regional anesthesia of motor and sensory nerves - testicular destruction - blindness Tx: - longterm dapsone -> may cause methemoglobinemia and hemolysis - alternatively, rifampin and combo of clofazimine and dapsone |
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Neisseria Meningitidis
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- gram negative cocci
- ferments glucose and MALTOSE - IgA protease - polysaccheride capsule (vaccine NOT against type B) - LOS (similar to LPS) interacts with TLR-4 -> up TNFa, IL1b, IL6+8 -> septic shock, ARDS - found in respiratory and oral secretions |
Manifestations:
- meningococcemia - meningitis - Waterhouse-Friderichsen syndrome - spread from pharynx -> blood -> choroid plexus -> meninges Tx: - rifampin prophylaxis in close contacts |
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Neisseria Gonorrheae
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- gram negative cocci
- ferments glucose but NOT maltose - IgA protease - no polysaccheride capsule - NO vaccine due to rapid antigenic variation of pilus proteins - sexually transmitted |
Manifestations:
- gonorrhea - septic arthritis - neonatal conjunctivitis - PID and Fitz-Hugh-Curtis syndrome (PID with inflammation/scarring of Glisson's capsule (violin strings) = perihepatitis) |
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Haemophilus influenzae
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- small gram negative coccobacillary rod
- grown in chocolate agar with factor V (NAD) and X (hematin), or w/ S. aureus (makes V) - makes IgA protease - most invasive dz caused by type B (vaccine conjugated to diphteria toxoid) - spread: aerosol transmission, pharynx -> lymphatics -> meninges |
Manifestations:
- epiglossitis ("cherry red" in kids) - meningitis - otitis media - pneumonia Tx: - meningitis w/ ceftriaxone - rifampin prophylaxis for close contacts - vaccine btwn 2-18mo of age - Ab against polyribosyl ribose phosphate -> complement-dependent phagocytosis |
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Legionella pneumophila
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- gram negative rod
- use silver stain to visualize - grow in charcoal yeast extract culture with iron and cysteine - aerosol transmission from water source habitat (AC, etc) - no person to person transmission |
Manifestations:
- Legionnaire's dz: severe pneumonia and fever - Pontiac fever: mild flu-like syndrome - also AIN, with low renin, low aldosterone, HYPONATREMIA Dx: presence of Ag in URINE Tx: erythromycin |
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Pseudomonas
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- gram negative rod
- oxidase positive, non-lactose fermenting - aerobic in WATER source - makes pyocyanin -> blue-green, grape-like odor Toxins: - endotoxin: fever, shock - exotoxin A: inactivates EF-2 |
Manifestation:
- esp burn and wound infxns - pneumonia (esp CF) - septicemia (black skin lesions) - external otitis (swimmer's ear) - UTI - drug use and diabetic osteomyelitis - hot tub folliculitis - endocarditis Tx: aminoglycoside plus extended-spectrum PCN (piperacillin, ticarcillin) |
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Syphilis
treponema pallidum (spirochete) |
- spirochete (spiral shaped with axial filaments)
- detect with dark field microscopy - many treponemes present in chancres (1˚) and condyloma latum (2˚) Tx: PCN G |
Manifestation:
1) Primary: painless chancre (localized) 2) Secondary: condyloma lata, maculopapular rash on palms and soles, constitutional sx (systemic) 3) Tertiary: gumma (chronic granulomas), neurosyphilis, aortitis (destruction of vasa vasorum), Argyll-Robertson pupil - broad-based ataxia, positive Romberg, Charcot joint, stroke without HTN 4) Congenital: saddle nose, saber shins, mulberry molars, Hutchinson's teeths, CN VIII deafness |
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VDRL
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- VDRL detects non-specific Ab that reacts with beef cardiolipin
- used for syphilis screening - confirm positive with FTA-Ab |
False VDRL:
- Viral (mono, hepatitis) - Drugs - Rheumatic fever - Lupus, leprosy |
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Leptospira Interrogans
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- question mark-shaped spirochete
- found in water contaminated with animal urine - common among surfers and in the tropics |
Leptospirosis:
- flulike sx, fever, HA - abdominal pain, jaundice - photophobia with conjunctivitis Weil's dz: - icterohemorrhagic leptospirosis - severe form with jaundice and azotemia (from liver and kidney dysfunction) - fever, hemorrhage, anemia |
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Lyme Dz
Borrelia burgdorferi |
- spirochete big enough to be visualized with aniline dyes (Wright's, Giemsa)
Transmission: - Ixodes tick (also vector for Babesia) - mice are impt reservoirs, deer required for tick life cycle |
Manifestation:
1) erythema chronicum migrans ("bull's eye"), flulike sx 2) neurologic (Bell's palsy), cardiac (AV block, third degree) 3) chronic monoarthritis, migratory polyarthritis Tx: doxycycline, ceftriaxone |
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Helicobacter Pylori
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- gram negative rod
- urease positive -> urease breath test - creates alkaline environment |
Manifestation:
- gastritis, 90% of duodenal ulcers - increases risk for PUD, gastric adenocarcinoma, lymphoma Tx: triple therapy - metronidazole, bismuth, amoxicillin/tetracycline - metronidazole, omeprazole, clarithromycin |
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Yersinia enterocolitica
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- gram negative
- transmission from pet feces, contaminated milk, pork |
Manifestation:
- outbreaks of diarrhea in daycare centers - mesenteric adenitis -> may mimic appendicitis or Crohn's |
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Vibrio cholerae
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- gram negative, comma-shaped
- oxidase positive - grows in alkaline media Toxin: - ADP ribosylation of G protein -> stimulates adenylyl cyclase -> cAMP up - increased Cl- secretion, decreased Na reabsorption - water moves out into gut -> watery diarrhea |
Manifestation:
- profuse, rice-water diarrhea - prompt rehydration necessary |
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Campylobacter jejuni
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- gram negative, comma-shaped
- oxidase positive - grows at 42˚C |
Manifestation:
- major cause of BLOODY diarrhea, esp in kids - common antecedent of Guillain-Barré syndrome Transmission: - fecal-oral through foods such as poultry, meat, unpasteurized milk |
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Salmonella
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- gram negative rod
- non-lactose fermenter - grows on TSI -> H2S - invades intestinal mucosa - flagella and can disseminate hematogenously - animal reservoir (except S. typhi = only in humans) Transmission: - food, feces, fingers, flies |
Manifestation:
- bloody diarrhea - sx may be prolonged with Abx use, monocytic response S. typhi: - typhoid fever: fever, diarrhea, HA, rose spots on abdomen - can remain in gallbladder chronically |
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Klebsiella
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- gram negative
- fast lactose fermenter - intestinal flora |
Manifestations:
- pneumonia (often aspiration), mucoid, red currant sputum - lung abscess (esp w/ pneumonia in alcoholics, diabetics) - also nosocomial UTI and enteric bacteremia |
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Shigella
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- gram negative rod
- non-lactose fermenter - NO H2S on TSI agar - lower infectious dose compared to salmonella (10 vs 10^5) Toxin: - shiga toxin inhibits 60S ribosome and protein synthesis - mucosal invasion is main virulence factor Transmission: food, feces, fingers, flies |
Manifestation:
- bloody diarrhea Pathogenesis: - invade intestinal mucosa via M cells of Peyer's patches - shigella lyses vacuole -> gets into cytoplasm - induces apoptosis and spreads via ACTIN polymerization - host response = PMNs |
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Escherichia coli
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- gram negative rod
- fast lactose fermenter Virulence factors: - fimbriae -> cystitis and pyelonephritis - K capsule -> neonatal meningitis - LPS endotoxin -> septic shock |
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EIEC
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Toxin and MOA:
- produces shiga-like toxin - microbe invades intestinal mucosa - toxin causes necrosis and inflammation |
Presentation:
- invasive - dysentery |
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ETEC
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Toxin and MOA:
- labile toxin (up cAMP) and stable toxin (up cGMP) - no inflammation or necrosis |
Presentation:
- traveler's diarrhea - watery |
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EPEC
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MOA:
- NO toxin - adheres to apical surface - villous blunting and malabsorption |
Presentation:
- diarrhea, usually in children |
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EHEC
O157:H7 most common serotype |
- does not ferment sorbitol!, glucuronidase negative
- distinguishes EHEC from other E. coli Toxin and MOA: - shiga-like toxin inactivates 60S ribosome - necrosis and inflammation - from poorly cooked hamburgers |
Presentation:
- bloody diarrhea, dysentery Hemolytic Uremic Syndrome: - microangiopathic hemolytic anemia - thrombocytopenia - AKI (uremia) -> endothelium swells and narrows lumen -> mechanical hemolysis and decreased blood flow to kidney - damaged endothelium consumes platelets |
