Common Bacterial Pathogens Flashcards
Staphylococcus aureus bacteria type
- gram+ cocci in clusters 2. catalase positive
Staphylococcus aureus primary sites
anterior nares and perineum
Staphylococcus aureus types of infection
- cutaneous infection 2. toxin-mediated disease 3. Pneumonia (hostpital-aquired) 4. foreign-body associated infections 5. bacteremia/endocarditis
Staphylococcus aureus: cutaneous infection virulence factors
coagulase=formation of fibrin capsule; alpha-toxin=cytotoxic agent
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
Staphylococcus epidermidis species group
SSNA=staph species, not aureus OR CNS=coagulase negative staphylococcus
Staphylococcus epidermidis: most common infection
bacterial endocarditis
Main species w/in genus Streptococcus
- Streptococcus pyogenes 2. Streptococcus pneumoniae 3. Enterococcus faecalis/Enterococcus faecium
Main characteristics of genus Streptococcus
- gram+ cocci in chains/pairs 2. catalase negative
Streptococcus pyogenes types of infection
- pharyngeal infection (strep throat) 2. skin and wound infection (cellulitis) 3. Post-streptococcal infections: a. glomerulonephritis b. rheumatic fever
Streptococcus pneumoniae bacteria structure
gram+ cocci in pairs; “diplococci” or “pneumococcus”
Streptococcus pneumoniae typical location
normal flora in UR tract of up to 40% of healthy people
Streptococcus pneumoniae: common infections
- frequent cause of pneumonia 2. sinusitis 3. otitis media 4. bronchitis 5. meningitis 6. bacteremia/septicemia
Streptococcus pneumoniae pathogenesis
antiphagocytic polysaccaride capsule allows bacteria to evade host defenses
Streptococcus pneumoniaevaccines
- adult=protect against invasive but not pneumonia 2. children=reduces disease in vaccinated
Viridans streptococci typical location
abundant in mouth
Viridans streptococci: common infections
- important cause of bacterial endocarditis 2. dental caries
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
Enterococcus faecalis & faecium typical location
normal flora of the intestines
Enterococcus faecalis & faecium: common sites of infection
- urinary tract 2. surgical wounds 3. biliary tract 4. endocarditis
Bacteria types w/in genus Clostridium
G+ rods: 1. strict anaerobes 2. endospore-formers
Clostridium difficile: common infections
- hospital-aquired diarrhea 2. hospital-aquired pseudomembranous colitis
Clostridium difficile: typical location
gut flora of ~10% of healthy people
Clostridium difficile:pathogenesis
- depletion of gut flora by antibiotic treatment 2. overgrowth of C. difficile 3. enterotoxin 4. potent cytotoxin
Clostridium tetani pathogenesis
“tetanus”=organism in soil/GI tract of animals–>infection (anaerobic + toxin production –> blocks interneurons in CNS
Clostridium botulinum pathogenesis
“botulism”=organism in soil/GI tract of animals–> contaminated food (anaerobic) + toxin production –> blocks Ach @ neuromuscular jxns
Clostridium perfringens: common infections
- wound infection (gangrene, cellulitis, etc.) 2. food poisoning
Clostridium perfringens wound infection pathogenesis
anaerobic; alpha toxin production
Clostridium perfringens food poisoning pathogenesis
consumed with contaminated food; produce enterotoxin that disrupts tight jxns
Typical Gram- rods
- E. Coli (Escherichia Coli) 2. Pseudomonas aeruginosa
E. Coli: typical location
normal gut flora
E. Coli: sensitivity to antibiotics
sensitive to most antibiotics, one of most common organisms to aquire resistance via drug-resistant plasmids
E. Coli: common infections
- GI disease 2. UTI 3. Abdominal infection
E. Coli: GI disease pathogenesis
consume contaminated food/water –> adherence to intestinal mucosa –> toxins disrupt gut electrolyte balane –> “traveler’s diarrhea”
E. Coli: UTI pathogenesis
endogenous bacteria from gut –> adherence to bladder epithelium + B-hemolysis –> UTI
E. Coli: Abdominal Infections pathogenesis
contents of colon escape into preitoneal cavity –> anaerobic abcess
Pseudomonas aeruginosa: common infections
- infection of traumatic injuries, surgical wounds, and BURNS (opportunistic) 2. chronic lung infection (cystic fibrosis pts) 3. hospital-aquired infections
Pseudomonas aeruginosa: antibiotic susceptibility
intrinsically resistant to many antimicrobials; must treat w/specialized regimen
Neisseria gonorrhaeae: bacterial structure
gram - diplococcus
Neisseria gonorrhaeae: common infections
- gonorrhea 2. conjuctivitis (–>blindness) in infants born to infected mothers
Neisseria gonorrhaeae: pathogenesis
pilus=key to adherence and avoidance of neutrophils + antigenic variation avoids recognition; growth on mucosal surface –> inflammatory response –> purulent discharge
Neisseria gonorrhaeae: antibiotic resistance
- penicillin 2. fluroquinolone 3. some cephalosporins
Anaerobic bacteria: typical location
normal flora in various body nitches e.g. colon, mouth, female genital tract, skin
Anaerobic bacteria: common disease properties
- endogenous origin 2. abscess formation 3. mixed infections (w/aerobic and anaerobic bacteria)
Bacteriodes fragilis: common infections
responsible for >80% of intraabdominal infections
Bacteriodes fragilis: bacteria type
anaerobic bacteria but relatively aerotolerant
Bacteriodes fragilis: virulence factors
- tissue destructive enzymes 2. antiphagocytic capsule 3. superoxide dismutase
Chlamydia trachomatis: bacteria type
obligate intracellular bacteria
Chlamydia trachomatis: common infections
- trachoma (conjuctiva infection) 2. genital infections 3. neonatal infections
Mycoplasma pneumoniae: bacteria type
bacterium w/out cell wall; contains sterols in plasma membrane
Mycoplasma pneumoniae: common infections
one of most common causes of pneumonia; mild infection
Mycoplasma pneumoniae: pathogenesis
adheres to respiratory cells –> extracellular growth –> hydrogen peroxide + superoxide radical production –> host tissue damage
