Common Bacterial Pathogens

Question 1

Name the Gram positive Cocci

Answer 1

Staphylococcus and SSNA (staph species, not aureus)

Question 2

Name the Gram positive Rods

Answer 2

Clostridium

Question 3

Name the Gram negative Cocci

Answer 3

Neisseria gonorrhoeae

Question 4

Name the Gram negative Rods

Answer 4

E. coli, Pseudomonas aeruginosa

Question 5

Name the Anaerobic Bacteria

Answer 5

Clostridia, Bacteroides fragilis. Typically form an abscess. Often in mixed infection because aerobes will metabolize oxygen, allowing anaerobs to grow.

Question 6

Name the Obligate Intercellular Bacteria

Answer 6

Cannot make own ATP.

Rickettsia, Chlamydia.

Question 7

Name the Bacteria without cell walls

Answer 7

Mycoplasma (mycoplasma pneumoniae)

Ureaplsma

Question 8

Staphylococcus aureus

Answer 8

Gram positive cocci in clusters
Asymptomatic carriage in 30% of ppl, usually anterior nares and perineum. Contains Alpha-toxin. Has enzyme coagulase which walls off the infection into a boil, evading phagocytosis. Staph endotoxin is a SUPERantigen

Question 9

Staph aureus Cutaneous infection

Answer 9

Folliculitis, boils, and wound infections. Often as a result of a foreign body (ie suture, splinter, catherter, prosthetic joints)). Coagulase creates a fibrinous capsule that restricts phagocytosis.

Question 10

Staph aureus Pneumonia

Answer 10

Heath-Care Associated Pneumonia (HCAP), Hospital Acquired Pneumonia (HAP) and Ventilator-Associated Pneumonia (VAP). High mortality (50%). In patients with impaired host defenses

Question 11

Staph aureus Toxic Shock Syndrome

Answer 11

Generally have a LOCALIZED infection. The bacterial toxins enter circulation, causing high fever, low blood pressure, malaise, confusion, eventually coma and multiple organ failure. O2 increased, neutral pH, Protein increased.

Question 12

Staph aureus Scalded Skin Syndrome

Answer 12

Localized infection, but skin affects can be all over body. Adult cases normally localized to feet, infants all over. Epidermis sloughs off.

Question 13

Staph aureus Antibiotic Resistance

Answer 13

Resistance to penicillins, methicillin, and emerging resistance to vancomycin.

Question 14

Staphylococcus epidermidis

Answer 14

Normal skin flora and relatively non-pathogenic. Can contaminate blood draws. Can be associated with localized infection. Infections associated with foreign bodies. COAGULASE NEGATIVE. Associated with a “slime” of extracellular glycocalyx.

Question 15

Streptocuccus and relatives

Answer 15

Streptococcus pyogenes, Streptococcus pneumoniae, Viridans streptococci, Enterococcus faecalis/Enterococcus facecium

Question 16

Streptococcus pyogenes

Answer 16

Gram positive cocci. Group A strep. Strep Throat. Virulence factor is M-protein, which inhibits phagocytosis and killing by PMNs. M-protein also enhances adherence to epithilial cells. Over 70 different serotypes of Strep pyogenes based on antigenic M-protein differences.

Question 17

Post-Streptococcal diseases

Answer 17

Glomerulonephritis, Rheumatic fever

Question 18

Glomerulonehritis

Answer 18

Immune complex disease that may follow skin or pharyngeal infection by Group A strep. Strep antigen-antibody complexes are deposited in the kidney and accumulate at the basement membrane. Self-limiting, complement-mediated kidney damage.

Question 19

Rheumatic fever

Answer 19

Autoimmmune inflammatory disease that may follow strep throat. Fever and inflammation of the heart, joints and other tissues. Result from the production of self-reactive ANTIBODIES (tissue is not colonized by the bacteria)

Question 20

Streptococcus pneumoniae

Answer 20

Gram positive cocci in pairs. Normal flora in UR tract. Evades host defense by Antiphagocytic polysaccharide CAPSULE. Can cause: pneumonia, sinusitis, otitis media, bronchitis. Pneumovax in adults, Prevnar in children. Emerging penicillin resistance.

Question 21

Viridan streptococci

Answer 21

Either alpha-hemolytic (green on blood agar) or non-hemolytic. Associated with dental caries. May gain access to blood stream with dental work, causing endocarditis.

Question 22

Enterococcus facecalis and faecium

Answer 22

Normal flora in intestines. Infection caused by surgical would, colon nick, etc. Commonly infects urinary tract, surgical wounds, biliary tract, and endocarditis. Often seen in mixed infections, including anaerobes. Antimicrobial resistance is becoming a problem (bye by vancomycin)

Question 23

Clostridium difficile

Answer 23

Can be normal flora is 10% of people. Hospital-acquired. Horrible diarrhea, psuedomembranous colitis. Resistant to most antibiotics. Spores are NOT killed by alcohol-based hand-sanitziers. Secrete and entrotoxin and a potent cytotoxin. Diagnosed by ELISA test of stool, or by PCR-based detection.

Question 24

Clostridium tetani

Answer 24

Common in soil and GI tracts of animals (spores). Local, anaerobic infection and toxin production. Transport toxin to CNS and blocks inhibitory inter-neurons of CNS = SPASTIC paralysis.

Question 25

Clostridium botulinum

Answer 25

Common in soil and GI tracts of animals (spores). Spores are activated with warmth and anaerobic conditions (ie home canned goods). Toxin blocks acetylcholine transmission at neruo-muscular junctions = FLACCID paralysis.

Question 26

Clostridium perfringens

Answer 26

Wound infections and food poisoning. Wounds: crushing type injuries and others that lead to low blood flow (low oxygen) environment. Bacterium produces alpha-toxin. Can range from cellulitis to gas gangrene. Food poisoning: enterotoxin which disrupts tight junctions between endothelial cells in ilium

Question 27

Clostridia bacteria

Answer 27

Gram positive rod. STRICT anaerobe. Forms Endospores, which are very difficult to kill and the spores are largely insensitive to oxygen. Causes diseases like: hospital acquired diarrhea, tetnus, botulism, and gangrene

Question 28

E. coli

Answer 28

Gram negative bacteria. Normal flora in intestine. Disease caused by endogenous organisms or ingestion. Most common organism to acquire resistance through plasmids. Causes GI disease, UTIs, and abdominal infections.

Question 29

E. coli GI disease

Answer 29

Many strains. From contaminated food and water. Typical travelers diarrhea (enterotoxigenic). Pili adhere to intestinal mucosa. Toxins disrupts electrolyte balance in gut.

Question 30

E. coli UTI

Answer 30

Isolates endogenous from GI tract. Adherence to bladder epithelium. UTI strains typically hemolytic.

Question 31

E. coli abdominal infections

Answer 31

Release/escape of toxins of colon from surgical wounds, traumatic wounds, or colon cancer. Often bacterially mixed cultures. Often associated with anaerobic bacteria in anaerobic abscesses

Question 32

Pseudomonas aeruginosa

Answer 32

Very common environmental bacterium, most people are very resistant to infection. Common infection of BURNS (opportunistic pathogen). Often chronic lung infection for patients with CYSTIC FIBROSIS. Also hospital-acquired infections.

Question 33

Pseduomonas aeruginoisa and CF

Answer 33

Nearly all CF patients are infected with P. aeruginosa by age 15-20. Bacteria are protected from phagocytosis by the patient’s viscus lung secretions. Progressive lung damage is due to action of the toxins and host immune response.

Question 34

Neisseria gonorrhoeae

Answer 34

Gram-negative diplo-cocci. Causative agent of gonorrhea and conjunctivitis leading to blinding. Pilus is required for virulence and antibody against pilis is protective (there are a TON of different strains of pili, so patients can be reinfected with different strains). Females: cervix, urethra, often asymptomatic. Males: uretritis, less asymptomatic. Resistant to penicillin

Question 35

Bacteroides fragilis

Answer 35

Prototypical endogenous anaerobic pathogen. Makes up 1-2% of total bacteria in colon, but associated wtih 80% abdominal infections. Relatively AEROTOLERANT. Produces tissue-destructive enzymes, an anti-phagocytic capsule and production of superoxide dismutase.

Question 36

Rickettsia

Answer 36

Obligate Intracellular bacteria- cannot make own ATP. Causes Rocky Mountain Spotted Fever.

Question 37

Chlamydia trachomatis

Answer 37

Obligate intracellular bacteria- cannot make own ATP. Genital infection, causes non-gonococcal urethritis is men, and urethritis, cervicitis, and PID. Chronic infection of conjunctiva for infants born to infected mothers, leading to scarring and blindness. Can also cause neonatal pneumonia

Question 38

Mycoplasma pneumoniae

Answer 38

Bacteria without a cell well. One of the most common of pneumoniae in ages 5-20. Shape is highly pleomorphin. Penicillin is NOT effective (no wall!). Does not stain with common Gram-stain, often diagnosed with serological tests or PCR. The bacteria produces hydrogen peroxide and superoxide radicals which damages the host tissues