Common Bacterial Pathogens

Question 1

Staphylococcus aureus bacteria type

Answer 1

1. gram+ cocci in clusters 2. catalase positive

Question 2

Staphylococcus aureus primary sites

Answer 2

anterior nares and perineum

Question 3

Staphylococcus aureus types of infection

Answer 3

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

Question 4

Staphylococcus aureus: cutaneous infection virulence factors

Answer 4

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

Question 5

Staphylococcus aureus: toxin-mediated disease virulence factor and example

Answer 5

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

Question 6

Staphylococcus epidermidis species group

Answer 6

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

Question 7

Staphylococcus epidermidis: most common infection

Answer 7

bacterial endocarditis

Question 8

Main species w/in genus Streptococcus

Answer 8

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

Question 9

Main characteristics of genus Streptococcus

Answer 9

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

Question 10

Streptococcus pyogenes types of infection

Answer 10

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

Question 11

Streptococcus pneumoniae bacteria structure

Answer 11

gram+ cocci in pairs; “diplococci” or “pneumococcus”

Question 12

Streptococcus pneumoniae typical location

Answer 12

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

Question 13

Streptococcus pneumoniae: common infections

Answer 13

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

Question 14

Streptococcus pneumoniae pathogenesis

Answer 14

antiphagocytic polysaccaride capsule allows bacteria to evade host defenses

Question 15

Streptococcus pneumoniaevaccines

Answer 15

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

Question 16

Viridans streptococci typical location

Answer 16

abundant in mouth

Question 17

Viridans streptococci: common infections

Answer 17

1. important cause of bacterial endocarditis 2. dental caries

Question 18

Viridans streptococci: pathogenesis

Answer 18

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

Question 19

Enterococcus faecalis & faecium typical location

Answer 19

normal flora of the intestines

Question 20

Enterococcus faecalis & faecium: common sites of infection

Answer 20

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

Question 21

Bacteria types w/in genus Clostridium

Answer 21

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

Question 22

Clostridium difficile: common infections

Answer 22

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

Question 23

Clostridium difficile: typical location

Answer 23

gut flora of ~10% of healthy people

Question 24

Clostridium difficile:pathogenesis

Answer 24

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

Question 25

Clostridium tetani pathogenesis

Answer 25

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

Question 26

Clostridium botulinum pathogenesis

Answer 26

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

Question 27

Clostridium perfringens: common infections

Answer 27

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

Question 28

Clostridium perfringens wound infection pathogenesis

Answer 28

anaerobic; alpha toxin production

Question 29

Clostridium perfringens food poisoning pathogenesis

Answer 29

consumed with contaminated food; produce enterotoxin that disrupts tight jxns

Question 30

Typical Gram- rods

Answer 30

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

Question 31

E. Coli: typical location

Answer 31

normal gut flora

Question 32

E. Coli: sensitivity to antibiotics

Answer 32

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

Question 33

E. Coli: common infections

Answer 33

1. GI disease 2. UTI 3. Abdominal infection

Question 34

E. Coli: GI disease pathogenesis

Answer 34

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

Question 35

E. Coli: UTI pathogenesis

Answer 35

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

Question 36

E. Coli: Abdominal Infections pathogenesis

Answer 36

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

Question 37

Pseudomonas aeruginosa: common infections

Answer 37

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

Question 38

Pseudomonas aeruginosa: antibiotic susceptibility

Answer 38

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

Question 39

Neisseria gonorrhaeae: bacterial structure

Answer 39

gram - diplococcus

Question 40

Neisseria gonorrhaeae: common infections

Answer 40

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

Question 41

Neisseria gonorrhaeae: pathogenesis

Answer 41

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

Question 42

Neisseria gonorrhaeae: antibiotic resistance

Answer 42

1. penicillin 2. fluroquinolone 3. some cephalosporins

Question 43

Anaerobic bacteria: typical location

Answer 43

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

Question 44

Anaerobic bacteria: common disease properties

Answer 44

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

Question 45

Bacteriodes fragilis: common infections

Answer 45

responsible for >80% of intraabdominal infections

Question 46

Bacteriodes fragilis: bacteria type

Answer 46

anaerobic bacteria but relatively aerotolerant

Question 47

Bacteriodes fragilis: virulence factors

Answer 47

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

Question 48

Chlamydia trachomatis: bacteria type

Answer 48

obligate intracellular bacteria

Question 49

Chlamydia trachomatis: common infections

Answer 49

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

Question 50

Mycoplasma pneumoniae: bacteria type

Answer 50

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

Question 51

Mycoplasma pneumoniae: common infections

Answer 51

one of most common causes of pneumonia; mild infection

Question 52

Mycoplasma pneumoniae: pathogenesis

Answer 52

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