Infectious Diseases

Question 1

2 types of UTIs

Answer 1

Bladder infection (cystitis, confined to bladder/urethra).
Pyelonephritis (kidney).

Question 2

Major pathogen of pyelonepritis

Answer 2

E.coli (ambulant patients)
> UPEC (uropathogenic)

> > ascending infections

Question 3

Pyelonephritis course of infection

Answer 3

Contamination of periutheral area with UPEC that has colonized bowel > ascension into bladder > adherence to uroepithelial cells by type 1 and P fimbriae > some can invade epithelial cells

• Some strains further ascend up urether into kidney (P fimbriae strains) > inflammation

Question 4

Pathogenicity factors of E.coli

Answer 4

LPS (O-ag), 
capsule (K-ag), flagella (H-ag), 
pili/non-fimbriae 
adhesins, 
hemolyins

Question 5

Causes of diarrhea?

Answer 5

viruses (noro/rota),
bacteria (campylobacter, salmonella, e.coli),
parasites (giardia)

Question 6

Which enterobacteriacae cause diarrhea?

Answer 6

Salmonella, Shigella, Yersinia, E.coli

Question 7

Characteristics of enterobacteriacae?

Answer 7

Gram-neg rods, facultatively anaerobic ( intestine), carbohydrate catabolism, catalase-pos, often motile (flagella),
cause diarrhea but also UTIs, sepsis etc

Question 8

3 types of parthenogenesis of infectious diarrhea

Answer 8

1. Enterotoxin-mediated
2. Cytotoxin-mediated
3. Invasion-mediated

Question 9

Example for cytotoxin-mediated diarrhea

Answer 9

E.coli (EHEC: obligatory pathogenic, Shiga toxin)

and Shigella (Shiga toxin, enters M cells, survival in phagocytes)

Question 10

Example for Enterotoxin-mediated diarrhea?

Answer 10

Vibrio cholerae.

AB-toxin cholera toxin (activates adenylate cyclase > electrolyte and water loss into intestine).

Question 11

Comparison Enterotoxin and Cytotoxin.

Answer 11

Entero: alters physiology of cell, loss of electrolytes/water but no damage/fever, watery stool
Cytotoxin: destroys host cell, inflammation/fever/loss of electrolytes and water, stooly mostly with mucus and blood

Question 12

Example invasion-mediated diarrhea

Answer 12

Salmonella: uptake into enterocytes > into macrophages > inflammatory responce, diarrhea

Question 13

Transmission of skin/wound infections

Answer 13

Contamination with bacteria from environment or endogenous smear infection with transient skin flora or smear infection wiht pathogens from other body sites.
Then: locally confined or dissemination

Question 14

Common cause of abscesses and wound infections?

Answer 14

Staphylococcus aureus (gram-pos cocci, transient skin/mucose flora, mostly endogenous infections, often resistant to antibiotics)

Question 15

Virulence factors of S.aureus

Answer 15

cell-surface ass.: Protein A (binds Fc receptors of ab), clumping factor
secreted: plasmakoagulases, staphylokinase, hemolysins, exfoliative toxins, TSST-1, etc

Question 16

Abscess formation by S.aureus

Answer 16

coagulases convert prothrombin to staphylothrombin > cleaves off fibrinopeptides from fibrinogen > fibrin dimers associate to fibrin threads > fibrin wall around skin is formed > are isolated from immune cells

(SSL10 peptides inhibit Thrombin formation that would attract neutrophils)

Question 17

Syndrome caused by S.aureus

Answer 17

Staphylococcal scalded skin syndrome (SSSS)

Exfoliative toxins: serine proteases that cleave desmoglein (required for association of skin cells > cleavage disrupts intergrity of skin) > destruction of epidermis

Question 18

Types of infections of respiratory tract

Answer 18

1. upper tract (S.pyogenes, H.influenzae)

2. lower tract (S.pneumoniae, C.pneumoniae)

Question 19

VFs of Streptococcus pyogenes

Answer 19

adhesion/colonization: lipoteichonic acid, hyaluronic acid

invasion/spread: capsule, streptokinase, streptolysins,

immune evasion: M proteins, capsule, pyrogenic exotoxins

Question 20

Pneumonia types

Answer 20

1. alveolar pneumiae/bronchopneuminae

2. atypical pneumoniae (infection of connective tissue of the lungs)

Question 21

Most common pathogen of pneumoniae in ambulant patients

alveolar/broncho-p.

Answer 21

Streptococcus pneumoniae (40-70% healthy carriers)

Question 22

VF of Streptococcus pneumoniae

Answer 22

Adhesion/colonization: phosphorylcholine, pili, CbpA
Invasion/dissemination to lungs: hyaluronidase, PavA
Growth/replication: lipoproteins PiaA and PiuA
Immunevasion: capsule, pneumolysin, IgA-protease

Question 23

Cause of atypical pneumoniae

Answer 23

Chlamydia pneumoniae: elementary bodies are taken up by host cells > transform to primary reticulate bodies (metabolically active) > diff into elementary bodies, can infect new cells

Question 24

Characteristics of meningitis, transmission

Answer 24

Infection of meninges (membranes that envelop brain/spinal cord) and liquor cerebrospinales

air-borne transmission > colonization of nasopharyngeal tract > translocation across epithelial layer > dissemination via blood stream > translocation across BBB > replication in cerebrospinal fluid > inflammation

pathogens alter spinal fluid

Question 25

Cause of meningitis, clinical signs

Answer 25

Neisseria meningitides

Stiff neck, fever, headache

Question 26

Signs of inflammation

Answer 26

fever, vasodilation and tissue perfusion (elevated haert beat and breath frequency), edema (damaged epithelial walls), pain, loss of function

Question 27

septiceamia

Answer 27

disseminated generalised inflamamtion (not locally confined) > overwhelm in inflammatory response

Question 28

Cause of septicaemia

Answer 28

Staphylococcus epidermidis (normal skin flora, adheres to plastic > catheters)
Recognition via TLR4

Question 29

Common themes of virulence factors

Answer 29

adhesion, invasion, spread, growth, immune evasion, toxins, (host response)

Question 30

What can appearance of spinal fluid tell you about the pathogens leading to meningitidis?

Answer 30

Bacteria: many cells (neutrophils), high protein and lactate concentration
Virus: fewer cells (granulocytes), low protein and lactate content, high glc levels