Common Bacterial Pathogens Flashcards Preview

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Flashcards in Common Bacterial Pathogens Deck (52):
1

Staphylococcus aureus bacteria type

1. gram+ cocci in clusters 2. catalase positive

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Staphylococcus aureus primary sites

anterior nares and perineum

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Staphylococcus aureus types of infection

1. cutaneous infection 2. toxin-mediated disease 3. Pneumonia (hostpital-aquired) 4. foreign-body associated infections 5. bacteremia/endocarditis

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Staphylococcus aureus: cutaneous infection virulence factors

coagulase=formation of fibrin capsule; alpha-toxin=cytotoxic agent

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Staphylococcus aureus: toxin-mediated disease virulence factor and example

superantigen toxins=non-specific T cell activation (25% of body T cells: e.g. Staphylococcal Toxic Shock Syndrome

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Staphylococcus epidermidis species group

SSNA=staph species, not aureus OR CNS=coagulase negative staphylococcus

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Staphylococcus epidermidis: most common infection

bacterial endocarditis

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Main species w/in genus Streptococcus

1. Streptococcus pyogenes 2. Streptococcus pneumoniae 3. Enterococcus faecalis/Enterococcus faecium

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Main characteristics of genus Streptococcus

1. gram+ cocci in chains/pairs 2. catalase negative

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Streptococcus pyogenes types of infection

1. pharyngeal infection (strep throat) 2. skin and wound infection (cellulitis) 3. Post-streptococcal infections: a. glomerulonephritis b. rheumatic fever

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Streptococcus pneumoniae bacteria structure

gram+ cocci in pairs; "diplococci" or "pneumococcus"

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Streptococcus pneumoniae typical location

normal flora in UR tract of up to 40% of healthy people

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Streptococcus pneumoniae: common infections

1. frequent cause of pneumonia 2. sinusitis 3. otitis media 4. bronchitis 5. meningitis 6. bacteremia/septicemia

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Streptococcus pneumoniae pathogenesis

antiphagocytic polysaccaride capsule allows bacteria to evade host defenses

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Streptococcus pneumoniaevaccines

1. adult=protect against invasive but not pneumonia 2. children=reduces disease in vaccinated

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Viridans streptococci typical location

abundant in mouth

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Viridans streptococci: common infections

1. important cause of bacterial endocarditis 2. dental caries

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Viridans streptococci: pathogenesis

gain access to bloodstream from mouth after dental manipulations and use dextrans to adhere to fibrin/platelet deposits on damaged heart valves

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Enterococcus faecalis & faecium typical location

normal flora of the intestines

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Enterococcus faecalis & faecium: common sites of infection

1. urinary tract 2. surgical wounds 3. biliary tract 4. endocarditis

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Bacteria types w/in genus Clostridium

G+ rods: 1. strict anaerobes 2. endospore-formers

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Clostridium difficile: common infections

1. hospital-aquired diarrhea 2. hospital-aquired pseudomembranous colitis

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Clostridium difficile: typical location

gut flora of ~10% of healthy people

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Clostridium difficile:pathogenesis

1. depletion of gut flora by antibiotic treatment 2. overgrowth of C. difficile 3. enterotoxin 4. potent cytotoxin

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Clostridium tetani pathogenesis

"tetanus"=organism in soil/GI tract of animals-->infection (anaerobic + toxin production --> blocks interneurons in CNS

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Clostridium botulinum pathogenesis

"botulism"=organism in soil/GI tract of animals--> contaminated food (anaerobic) + toxin production --> blocks Ach @ neuromuscular jxns

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Clostridium perfringens: common infections

1. wound infection (gangrene, cellulitis, etc.) 2. food poisoning

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Clostridium perfringens wound infection pathogenesis

anaerobic; alpha toxin production

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Clostridium perfringens food poisoning pathogenesis

consumed with contaminated food; produce enterotoxin that disrupts tight jxns

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Typical Gram- rods

1. E. Coli (Escherichia Coli) 2. Pseudomonas aeruginosa

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E. Coli: typical location

normal gut flora

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E. Coli: sensitivity to antibiotics

sensitive to most antibiotics, one of most common organisms to aquire resistance via drug-resistant plasmids

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E. Coli: common infections

1. GI disease 2. UTI 3. Abdominal infection

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E. Coli: GI disease pathogenesis

consume contaminated food/water --> adherence to intestinal mucosa --> toxins disrupt gut electrolyte balane --> "traveler's diarrhea"

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E. Coli: UTI pathogenesis

endogenous bacteria from gut --> adherence to bladder epithelium + B-hemolysis --> UTI

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E. Coli: Abdominal Infections pathogenesis

contents of colon escape into preitoneal cavity --> anaerobic abcess

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Pseudomonas aeruginosa: common infections

1. infection of traumatic injuries, surgical wounds, and BURNS (opportunistic) 2. chronic lung infection (cystic fibrosis pts) 3. hospital-aquired infections

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Pseudomonas aeruginosa: antibiotic susceptibility

intrinsically resistant to many antimicrobials; must treat w/specialized regimen

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Neisseria gonorrhaeae: bacterial structure

gram - diplococcus

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Neisseria gonorrhaeae: common infections

1. gonorrhea 2. conjuctivitis (-->blindness) in infants born to infected mothers

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Neisseria gonorrhaeae: pathogenesis

pilus=key to adherence and avoidance of neutrophils + antigenic variation avoids recognition; growth on mucosal surface --> inflammatory response --> purulent discharge

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Neisseria gonorrhaeae: antibiotic resistance

1. penicillin 2. fluroquinolone 3. some cephalosporins

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Anaerobic bacteria: typical location

normal flora in various body nitches e.g. colon, mouth, female genital tract, skin

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Anaerobic bacteria: common disease properties

1. endogenous origin 2. abscess formation 3. mixed infections (w/aerobic and anaerobic bacteria)

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Bacteriodes fragilis: common infections

responsible for >80% of intraabdominal infections

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Bacteriodes fragilis: bacteria type

anaerobic bacteria but relatively aerotolerant

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Bacteriodes fragilis: virulence factors

1. tissue destructive enzymes 2. antiphagocytic capsule 3. superoxide dismutase

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Chlamydia trachomatis: bacteria type

obligate intracellular bacteria

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Chlamydia trachomatis: common infections

1. trachoma (conjuctiva infection) 2. genital infections 3. neonatal infections

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Mycoplasma pneumoniae: bacteria type

bacterium w/out cell wall; contains sterols in plasma membrane

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Mycoplasma pneumoniae: common infections

one of most common causes of pneumonia; mild infection

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Mycoplasma pneumoniae: pathogenesis

adheres to respiratory cells --> extracellular growth --> hydrogen peroxide + superoxide radical production --> host tissue damage