Common Bacterial Pathogens Flashcards
Gram + cocci
Staph family: Staphylococcus aureus -SSNA "staph species, not aureus" Strep family: -streptococcus pyogenes -streptococcus pneumoniae -"viridans" streptococci -Enterococcus faecalis/Enterococcus faecium
Gram+ rods
Most = clostridium
Endospore forming obligate ANAEROBES
- clostridium difficile
- clostridium tetani
- clostridium botulinum
- clostridium perfringens
Aerobic and facultative Gram - rods
- E.coli
- Pseudomonas aeruginosa
Gram - (diplo) cocci
Neisseria gonorrhoeae
Anaerobic bacteria (other than clostridia)
bacteroides fragilis
Obligate Intracellular Bacteria
Richettsia
Chlamydia trachomatis
Bacteria w/o cell walls
Mycoplasma pneumoniae
Staph. aureus
Primary pathogenic species
Gram+ cocci, clusters
Carried in anterior nares/perineum, asymptomatic in 30% of carriers.
Coagulase = virulence factor, interferes w/ phagocytosis
Alpha-toxin = cytotoxic agent
Drug resistance to penicillins, methicillin, and vancomycin.
Staph. aureus
cutaneous infection
Folliculitis, boils, wound infection.
Localized abscess
Formation of fibrinous capsule which walls of infection (associated w/ presence of foreign body)
Staph. aureus - toxic shock syndrome
Caused by superantigen toxin - non-specific T-cell antivation, massive cytokine release.
High fevel, low BP, malaise, confusion. Can progress to coma/death. Characteristic rash (will slough off 10-14 days after infection if pt survives)
Staph. aureus - food poisoning
Superantigen toxin. Ingestion of preformed toxin of contaminated food.
Staph. aureus - pneumonia
Opportunistic and common in hospital acquired pneumonia.
Staph. aureus - foreign body associated infections
Vascular catheter related infections, prosthetic joint, hardware.
Staph. aureus - endocarditis
Common cause of heart valve infection :(
Staph. epidermidis
SSNA/CNS (coagulase neg. staph)
Found in normal skin flora
Disease causing b/c produce slime, a glycocalyx which adheres to various implanted devices and allows for growth of biofilm
Resistant to methicillin. Dif. to treat b/c biofilm makes reaching these infections hella hard.
Streptococcus pyogenes
“Group A Strep”
Causes pharyngeal infection, skin and wound infection and post-strep diseases.
Strep. pyogenes - Pharyngeal infections
Strep throat!
Virulence factor: M-protein.
Spread by contact of nasal sections/droplets.
Strep. pyogenes - Skin and wound infections
Commonly cellulitis.
Produce hydrolyric enzymes that bread down tissue and kill phagocytic cells.
SO THIS SPREADS (unlike w/ staph aureus)
Strep. pyogenes - Glomerulonephritis
Post strep infection.
Immune complex disease, antigen-antibody complex gets stuck in basement membrane of kidney. Complement mediated damage to kidney results.
Strep. pyogenes - rheumatic fever
Autoimmune. Cross-reaction of host antigens with fibrin which is found on heart valves + myocardium. Antibody mediated damage to tissues.
(this is independent of bacteria)
Strep. pneumoniae
Usually in pairs (diplococci)
Normal flora in UR tract in 40% of people.
Pathogenesis associated w/ antiphagocytic polysaccharide capsule.
Resistant to penicillin (some strains)
Strep. pneumoniae non-invasive disease examples
Pneumonia
Sinusitis
Otitis Media
Bronchitis
Strep. pneumoniae, invasive disease examples
Meningitis
Bacteremia/septicemia
Pneumonia w/ septicemia
Strep. pneumoniae Vaccines
Adult - Pneumovax, PPSV23. protection against invasive strains. Not against pneumonia. 65+ and immunocompromised adults.
Children: hepta or 13 valent, reduced overall pneumoccocal carriage. gr8 for herd immunity.
Viridans streptococci
Bacterial endocarditis!!!
Can be either alpha-hemolytic or non-hemolytic.
Abundant in mouth. Associated w/ dental carries - may get access to blood w/ dental procedures.
Viridans streptococci - Bacterial endocarditis
Produce dextrans which adhere to tissue/teeth.
There allow for adherence to fibrin/platelet deposits on damaged heart valves.
Enterococcus faecalis / Enterococcus faecium
Common normal flora in intestines.
May cause a shit-ton of things in: Urinary tract Biliary tract Endocaditis Nosocomial infections Surgical wounds
Often selected for w/ therapy of cephalosporins.
Biggest problem are vancomycin resistant enterococci.
Clostridium difficile
hospital acquired infections
normal flora in 10%
Causes diarrhea and pseudomembranous colitis
Produces both endotoxin and cytotoxin.
Resistant to most antibiotics.
Clostridium tetani
Found in soil and GI tract of animals.
Causes tetanus - lockjaw
Causes retrograde axonal transport of toxin in CNS.
Spastic paralysis due to clock of inhibitory interneurons in CNS.
Vaccine much more effective than using human immunoglobulins in ppl who already have it.
Clostridium botulinum
Found in soil + GI tract of animals
Grows in contaminated food under aerobic conditions.
Produces botulinum toxin, which blocks acetylcholine at neuromuscular junctions.
Causes flaccid paralysis.
Clostridium perfringens - wound infection
Such as: cellulitis, myonecrosis and gangrene.
Happens w/ crushing types of injury where oxygen cut off to tissue. Produce alpha toxin (phospholypase enzyme) which kills phagocytic cells and muscle tissue.
Clostridium perfringens - food poisoning
Produces enterotoxin and bacteria sporulate in gut.
This disrupts tight junctions between endothelial cells in ilium, resulting in issues w/ electrolyte balance and fluid transport (sounds like it would cause diarrhea eh??? )
Escheria coli
Aerobic and facultative
Normal flora in large intestine
Usually pretty sensitive to antibiotics, but drug resistance HAS been seen w/ acquisition of plasmids
E. coli - GI disease
food/water contaminated w/ e.coli usually the cause.
Typical travelers diarrhea. This e-coli adheres to intestinal mucosa w/ pili
Uses some awesome enterotoxin to disrupt electrolyte balance
E.coli - UTI
Usually from own GI tract.
Adheres to bladder epithelium, these stains are often beta hemolytic
E. coli - Abdominal Infections
escape of bacteria in colon into the peritoneal cavity due to surgical wounds/trauma/colon cancer.
Often mixed, friendly w/ anaerobic bacteria (perhaps using up all the O2 so these babies can live?)
Pseudomonas aeruginosa
Common environmental bacteria
Most people are resistant.
Resistant to most anti-staph drugs.
Pseudomonal aeruginosa - Chronic Lung Infection in CF Patients
Nearly all CF patients get chronically infected w/ this by 15-20.
Protected from phagocytosis by thick mucus produced by patient.
Damages lungs by toxin secretion and immune system activation.
Most common cause of death in patients w/ CF.
Pseudomonal aeruginosa - Hospital acquired infections
Include UTIs, pneumonia and occasionally intravascular catheter related infections
Neisseria gonorrhoeae
Gram - cocci which is obvi the causative agent of the gonorrhea we know and love
THE KEY TO ITS INFECTIVENESS IS!!!! Its pilus. Required for adherence and interferes w/ bacterial killing by neutrophils.
Causes purulent discharge, local tissue invasion, eventually scarring and fibrosis (w/o treatment)
Almost always resistant to penicillin, fluroquinolone, and some resistant to cephalosporins
Neisseria gonorrhoeae - males
Present as asymptomatic to urethritis.
Neisseria gonorrhoeae - females
Infection of cervix, urthera. More often asymptomatic than males.
Ascending infection (up reproduction tract) may lead to fibrosis and infertility
Neisseria gonorrhoeae - babies
Blindness in infants born to infected mothers (conjunctivities)
Anaerobic bacteria
Usually normal flora in mouth, colon, female genitalia and skin.
Typical lesion: absess
The hallmark of anaerobic bacterial infection is MIXED infection w/ aerobic and anaerobic bacteria.
Most effective drug: metronidazole
Least effective: aminoglycosides
Bacteriodes fragilis
(anaerobic bacteria)
Associated w/ 80% of intra abdominal infections
Relatively aerotolerant
Virulence factors: produces a variety of tissue destructive enzymes, ant phagocytic capsule and superoxide dismutase
Obligate Intracellular Bacteria
Only grow within infected eukaryotic cells
Rickettsia
Causes Rocky Mountain Fever
Has lost the ability to make own ATP and completely relies on host
Chlamydia trachomatis - trachoma
Chronic infection of conjunctive, leading to scarring and blindness. Endemic in Asia and Africa.
Chlamydia trachomatis - genital infections
Can present as:
Male: non-gonococcal urthritis
Female: urethritis, cervicitis, PID
Relately common STD. Co-infections w/ gonorrhea.
Chlamydia trachomatis - Neonatal infections
Neonatal conjunctivitis/pneumonia
Infants born to infected mothers may become infected at birth
Lots of screening for this now tho
Bacteria without Cell Walls
Mycoplasma pneumoniae
contain sterols in plasma membrane, no cell wall obvi
Doesn’t stain w/ Gram stain, so good way to rule out other infections.
Common cause of pneumonia in ages 5-20, adheres to respiratory epithelial cell. Generally mild pneumonia with fever, headache, sore throat.
Bacteria produces hydrogen peroxide and superoxide radicals.
Penicillins NOT EFFECTIVE b/c cell is highly pleomorphic
