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Block 2 - Bugs and Drugs > Bugs > Flashcards

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0
Q

Staphylococcus aureus

A

*Coagulase positive
Clumping factor (fibrinogen binding protein)
Intrinsically virulent organism
Skin syndromes - lots
Toxicities - scalded skin/bulbous impetigo, toxic shock syndrome

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1
Q

Staphylococci - general

A

Aerobic, gram positive, grape cluster
*Catalase positive - allows growth in oxygen
Positive or negative coagulase
*systemic infections can end up almost anywhere

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2
Q

Coagulase negative staphylococcus

A

About 30
S. epidermis - causes disease on medical devices
S. saprophyticus - causes uti in young women

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3
Q

Staphylococci reservoirs

A

Nose - s. aureus, often a source for bacteremia

Skin - s. aureus intermittently, all coagulase-negative

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4
Q

Staphylococcal virulence factors

A

*capsular polysaccharide = antiphagocytic
Protein a - binds Ig, possible immune evasion
Secreted factors
*antibiotic resistance - 60-70% MRSA nationwide, 50% at parkland

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5
Q

Beta hemolytic streptococci serogroups pathogenic for humans

A
  • lancefield group A - pharyngitis

* lancefield group D - bacteremias associated with colon cancers

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6
Q

Group A streptococcal virulence factors

A
  • adherence - m protein, lipoteichoic acids, fibronectin binding protein
  • immune evasion - m protein, capsule, Ig binding protein, c5a peptidase
  • invasion and spread
  • toxicity - super antigens, pyrogenic exotoxins
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7
Q

Where are group a streptococci resident?

A

On skin and in throat, can include local and invasive infections and toxicity syndromes
Antibiotics don’t shorten duration of illness but can prevent later complications
Strep can spread to deeper tissues

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8
Q

Streptococcal toxicity syndromes and post infectious sequelae

A

Scarlet fever - skin infection following throat, lysogen if phages
Streptococcal toxic shock - follows invasive disease, bacteremia, superantigen, different than toxic shock from staph
Post - rheumatic fever (follows pharyngitis only), acute post-streptococcal glomerulonephritis (follows skin infection or pharyngitis)

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9
Q

Group b streptococci

A

Postpartum infections
Neonatal infections
Capsular polysaccharide - antiphagocytic, type 3 most associated with disease

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10
Q

Streptococcus pneumoniae

A

Gram positive, alpha hemolytic, grows in pairs, capsule
*optochin sensitive - rest of alpha streps resist lysis by this chemical
Otitis media in children, sinusitis, conjunctivitis, chronic bronchitis, pneumonia, meningitis
Polysaccharide adhesion factors adhere to n-acetylglucosamine for attachment

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11
Q

Enterococcus

A 
Non hemolytic or weak alpha hemolysis
Same group antigen as group d strep
-*grows in 6.5% Salt, s. bovis does not - easy lab ID 
12 species - 2 imp in humans
Live in intestines of many animals 
Poor pathogen
Nosocomial infections
Vancomycin resistance
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12
Q

Bacillus anthracis

A

Aerobic, nonhemolytic, spore forming gram positive rod, chain like appearance histologically
Encapsulated - polyglutamic not carb
Intracellular pathogen of macrophages
Habitat is soil or GI tract of animals

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13
Q

Anthrax

A

Toxin mediated
Three main clinical syndromes - cutaneous, GI, inhalation
Inhalational - spores carried in macrophage to draining lymph nodes and germinate, form toxins to kill macrophage and other tissue, spread to blood stream and other organs

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14
Q

Bacillus cereus

A 
Aerobic, spore forming gram pos. rod
Soil and GI tract of herbivores
Identical gram stain to b. anthracis
GI disease - emetic, *classically associated with eating fried rice, diarrheal
blood stream infections and cellulitis
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15
Q

Listeria monocytogenes

A 
Non spore forming gram positive rod, beta hemolytic, aerobic coccobacillary
Tumbling motility
Intracellular - grows in cytoplasm 
*can grow at "deli temp"
Animal reservoir, food borne disease
*treatment is ampicillin
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16
Q

Enterobacteriaceae

A 
Gram negative rods, facultative anaerobes
Non spore forming
Catalase positives 
Reduce nitrate to nitrite
Ferment glucose and other sugars
Motile with flagella 
Includes e. coli
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17
Q

E. Coli

A

Motile, facultative anaerobe, gram negative rod
Most commensal in GI tract
Most common syndromes - uti, diarrhea, neonatal sepsis and meningitis
*number 1 cause of UTI

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18
Q

E. Coli toxins

A
  • heat labile toxins (plasmid)
  • AB toxin, travelers diarrhea
  • heat stable toxin (plasmid)
  • shiga-like toxin (lysogenic prophage)
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19
Q

Vibrio

A

Curved GNR shaped like comma
Motile with single flagellum
*habitat = aqueous environments
Vibrio cholerae - classic syndrome

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20
Q

Heliobacter pylori

A

Curved motile GNR
microaerophilic - use amino acids for energy
*malignancies - gastric carcinoma, MALT lymphoma (can be cured by antibiotics)

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21
Q

Campylobacter

A

Curved, motile GNR
*temperature optimum of 42 deg c
Reservoir is birds - most chickens
Syndrome of febrile bloody diarrhea

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22
Q

Pseudomonas aeruginosa

A 
GNR, motile with polar flagellum
Aerobic, non fermenter
*oxidase positive
Fruity smell in culture
Soil and water organisms
*forms biofilms (imp in CF)
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23
Q

Pasteurella multocida

A

Nonmotile GNR
Kills many
Lives in mouths of cats and dogs

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24
Francisella tularensis
Causes tularemia - zoonotic infection Nonmotile GNR Bioterrorism a gent Acquired by skin puncture or inhalation
25
Legionella pneumophilia
Aerobic GNR ubiquitous in water Grows in macrophage Community acquired pneumonia
26
Neisseria meningitidis and neisseria gonorrhoeae
``` Gram negative diplococci No motile, aerobic - do not ferment Require increased co2 for growth in lab Grow on chocolate agar Oxidase positive All other neisseria not pathogens IgA protease ```
27
The meningococcus
Reservoir is nasopharynx of humans Epidemics in densely congregated of closed populations Encapsulated Vaccine effective against 4 of 5 disease serotypes (not B) Most common cause of sporadic bacterial meningitis in young adults
28
The gonococcus
Humans only reservoir Pilin for attachment Phase variation for immune evasion
29
Anaerobes
Mouth - lung, oral, and pharyngeal abscesses, periodontal disease *GI tract - comprise 99.99% of colonic flora - abdominal abscess GU tract - PID, tubo-ovarian abscesses Skin appendages - hair follicles and sweat glands
30
Chlamydia and clamydophila
*obligate intracellular parasites Grow in culture on embryonic eggs or in tissue culture Rigid cell wall - *no peptidoglycan LPS *cannot synthesize ATP - rely entirely on host
31
Different types of chlamydia
Chlamydophila pneumoniae - pneumonia Chlymadophila psittaci - in birds, causes pneumonia syndrome Chlamydia trachomatis - std, neonatal disease, ocular disease (leading cause of infectious blindness in the world)
32
Rickettsia
Structurally gram neg - LPS and peptidoglycan *does not stain with gram stain Obligate intracellular parasite - egg yolk and tissue culture *replicate in endothelial cells of blood vessels Rocky Mountain spotted fever and typhus
33
Rocky Mountain spotted fever
Mostly in southeast Spring and summer peaks One week incubation First present with fever myalgias and headache After one week rash - must treat presumptively before this
34
Epidemic typhus
Transmitted by human body louse | Problem in areas with poor hygienic conditions
35
Ehrlichia and anaplasma
Gram negative like with dual membrane but *no LPS or peptidoglycan *no stain with gram stain - use wright or giemsa Obligate intracellular parasite E - in monocytes A - in granulocytes *acute febrile syndrome with blood cell abnormalities
36
Coxiella burnetii
Causes Q fever - acute (resolves without treatment) and chronic (endocarditis) and pregnancy (abortions and neonatal deaths) Obligate intracellular parasite Gram neg membrane but doesn't stain with gram *undergoes phase variation based upon LPS animal reservoir - humans acquire by inhalation
37
Mycoplasma
*causes walking pneumonia = community acquired pneumonia
38
Spirochetes
Never cultivated in vitro Too narrow tone seen in gram stain or light microscope - use dark field In tissue use silver based stains - *warthin-starry or dieterle Two membranes but not gram neg *treponema and borrelia do not have LPS but leptospira does Peptidoglycan Periplasmic flagella and corkscrew motility
39
Treponema pallidum
Causes syphilis Obligate parasites - humans only hosts, extra cellular Microaerophiles Not cultivable in vitro but can be in rabbits Multiply locally and disseminate throughout body
40
Syphilis
3 stages Primary - 3 weeks after infection, painless genital ulcer, heals on it own Secondary - general rash resolves spontaneously, relapses Then latency Tertiary - skin and bones, cardiovascular, neurosyphilis Treatment =penicillin
41
Borrelia
Lyme disease | Relapsing fever - endemic or epidemic
42
Lyme disease
Zoonotic, follows ioxodid ticks Early - characteristic rash, joints, conduction abnormalities, neurological symptoms Late - arthritis, carditis, neuropathy
43
Relapsing fever
Endemic - soft bodied ticks, rodent reservoirs with humans as accidental hosts Epidemic - carried by body louse, humans only host, associated with unhygienic environments, more mortality
44
Leptospira
Has LPS primarily disease of tropics and subtropics Urban cycle in temperate environments Zoonotic *excreted in urine and contaminates water Absorbed through skin or mucous membranes then bacteremia Weil's disease - bleeding, liver failure
45
Mycobacteria and filamentous bacteria
*slow growing | Resemble fungi on plates
46
Mycobacteria
Aerobic, sort of gram pos, lack LPS *does not stain with gram stain Waxy coat of mycolic acids - long chain fatty acids Cell wall has LAM - glycolipid that is major virulence factor and modulates macrophage function and scavenges oxygen radicals Cord factor - causes serpentine cords in culture, toxic to PMN, damages mitochondria, causes formation of granulomas
47
Acid fast staining
Acid fastness is property of mycobacteria and nocardia Procedure analogous to gram stain Background is blue *"red snappers" = mycobacterium tuberculosis
48
Mycobacterium tuberculosis
Five species Humans major reservoir - 1/3 of worlds population Transmission usually through inhalation - does not require a lot Ingestion also possible Tuberculosis - engulfed by macrophages and inhibits phagolysosome fusion, resistant to reactive species and killing by macrophages, drain to hilar and mediastinal lymph nodes, then bacteremia
49
Stages of tuberculosis
Primary - most people a symptomatic, may present as pneumonia Progressive - usually in elderly or immunocompromised Re activation - about 4% per year first two years then 1% per year
50
Testing and diagnosis of tuberculosis
``` Skin testing - tuberculin, PPD Quantiferon - interferon gamma release assays Staining Culture - "gold standard" Molecular techniques - PCR, probes ```
51
Treatment of tuberculosis
Multiple drugs over extended periods of time | Multidrug resistant and extremely drug resistant tb exist
52
Nontuberculous mycobacteria
Runyon classification Group 1 - photochromogens - produce pigment only in light Group 2 - scotochromogens - produce pigment in light or dark Group 3 - nonchromogens - no pigment Group 4 - rapid growers
53
Mycobacterium avium complex
``` Runyon group 3 Ubiquitous in water environments Temp optimum of 41 deg c Causes avian tb Two major disease syndromes - lung disease and HIV infections ```
54
Mycobacterium chelonae
Associated with tattoos
55
Mycobacterium leprae
Morphologically identical and genetically related to m. Tb Not cultivable in vitro but grows in footpads of mice or armadillo Spread by respiratory or direct contact but transmission difficult Incubation period 2-10 years Treatment = dapsone, rifampin and clofazimine Tuberculoid and lepromatous responses
56
Tuberculoid m. Leprae
Stronger T cell response Fewer skin lesions Localized skin reaction Few bacteria
57
Lepromatous m. Leprae
Absent T cell response Many modular legions - leonine faces Abundant bacteria in lesions Progressive clinical course
58
Nocardia
``` Gram pos - SOD and catalase Branching and filamentous Slow growing *weakly acid fast (modified acid fast stain) Shorter chain mycolic acids Soil bacteria Opportunistic pathogens Clinical syndromes - pneumonia, skin disease, long duration of treatment ```
59
Actinomyces
Filamentous branching gram pos rod *does not stain with acid fast - no mycolic acids Anaerobic or microaerophilic Slow growing Part of normal flora in mouth, GI tract, and GU tract - infections in immunocompromised host Chronic draining sinuses - *"sulfur granules" Clinical syndromes - bad dentition and lumpy jaw, thoracic descending infection, abdominopelvic after surgery or IUD prolonged therapy with penicillin

Block 2 - Bugs and Drugs (9 decks)

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