Infectious Disease

Question 1

What features of the skin provide protection against invaders?

Answer 1

production of antimicrobial fatty acids and defensins Lower pH of the skin protects from overgrowth of bacteria and fungi
Constant replenishing of epithelial cells also protects from wear and tear stress

Question 2

Most microbes gain entry via

Answer 2

Mechanical injury to the epidermis

Changes to its natural environment (ex. change in normal flora)

Question 3

Urinary tract is protected from microbes via

Answer 3

sterile urine and frequent micturition

Question 4

Urinary tract infections (UTI) spread in retrograde fashion

Answer 4

From urine contaminated with pathogens from the urethra (more common in females due to anatomy - perineum)
Obstruction or reflux (vesicoureteral reflux) of urine also compromises normal defenses

Question 5

The female genitalia is protected from pathogens via

Answer 5

via normal vaginal flora (lactobacilli), causing lower pH in the vagina
The uterine cervix is also resistant to infections secondary to protective properties of the squamous mucosa that covers it
Cell constantly replenishing from wear and tear stress, as well an menses

Question 6

Pathogens gain entry via sexual contact or local changes that alter natural defenses of the squamous epithelium . Examples?

Answer 6

1. Antibiotics kill normal protective flora, allowing overgrowth of yeast
2. Changes in pH can alter balance of normal flora, allowing for bacteria overgrowth (STIs, inflammation, trauma)
3. Some viruses cause proliferation of immature epithelial cells that are susceptible to infections
4. Organisms that cause STIs commonly adhere to the surface epithelium and proliferate

Question 7

respiratory tract protection

Answer 7

mucociliary blanket lining

resident macrophages or recruited neutrophils

Question 8

Pathogens gain entry via inhalation, and with associated changes that alter natural defenses. Examples?

Answer 8

1. Aspiration
2. Chronic damage to mucocilia (ex. smoking, CF)
3. Bacterial toxins that impair ciliary action (ex. Mycobacterium, Bordetella, Haemophilus)
4. Immunodeficient states
5. Organisms that evade phagocytosis and clearing - TB
6. Direct trauma related to mechanical ventilation and intubation (trauma to epithelial lining causes lacerations and associated inflammation)

Question 9

GI defenses:

Answer 9

Very tight cellular junctions of the epithelium 
Normal gut flora 
Mucosal antimicrobial defensins
Viscous mucosal layer
Gastric acid secretions
Peristalsis
Pancreatic enzymes 
Bile detergents
MALT / GALT (M cells and Peyer’s patches)

IgA antibodies produced by plasma cells within Peyer’s patchesPancreatic enzymes have proteases that keep the intestines free of bacteria, yeast, and parasites like protozoa

Bile has potent antimicrobial activity, primarily through the dissolution of bacterial membranes
This reduces bacteria flora found in the small intestine and biliary tract
PP and M cells are part of MALT system that traps Ag and transports them to lymph system for removal
M cells line mucosal surfaces and traps Ag to present them to underlying macrophages  then to lymph
Peyer’s patches are clusters of lymphoid cells (nodules) that are located in the submucosa lining the small intestines (most abundant in the ileum)
M cells act like a mucociliary blanket, feed antigen to the peyer patches

Question 10

Staph

Answer 10

Secretes enterotoxins without multiplying, causing enteritis

Question 11

E. coli, V. cholera

Answer 11

Adhere to mucosa and locally proliferate, Exotoxin release causes large amounts of fluid release

Question 12

Shigella, Salmonella, Campylobacter, Entamoeba

Answer 12

Adhere to and invade mucosa causing inflammation, ulceration, and hemorrhaging = dysentery

Question 13

polio virus

Answer 13

“Hijacks” immune system through lymphoid channels causing lymphadenopathy and systemic manifestations via Payer’s patches and M cells

Question 14

What are the three types of vertical transmission?

Answer 14

placental-fetal - affect the baby according to trimester and developmental stages
delivery - most common with STIs
postnatal - nursing, CMV, HBV, HIV

Question 15

mechanism of microbial damage to host cells

Answer 15

1. Microbes release toxins that degrade local tissues, damages blood vessels, or cause tissue ischemia
2. Secrete lytic enzymes that cause death to host cells, destroy local tissue and/or allows local tissue invasion
3. Ensuing immune response directed towards the invading organism may also cause further local damage to host cells and tissues - super antigens
4. Local bacteria may disseminate to distant sites by traveling within host cells or within extracellular fluid like blood and lymph - sepsis!

Question 16

A patient presents will abnormal gait and coordination. HIs wife says his personality has changed, as well as losing some core memories. A CT/MRI and EEG is performed and spongiform tissue is seen on the radiograph. A lumbar puncture also is performed and PrPsc is found. What’s up? He has also recently had a dura graft. What is his life expectancy now? Also, he ate a human while in Guinea.

Answer 16

prion disease
CJD is very rare, 1 in 1000000. vCJD comes from eating infected beef (Bovine spongiform encephalitis).
Could also be random, iatrogenic, or familial.
Iatrogenic causes are procedures dealing with brain or nervous tissue, human derived pituitary growth hormone, organ transplants (particulary dura grafts or cornea transplant).
He was a cannibal. Kuru
Normal PrPc is transformed into pathologic PrPsc when they meet. Amyloids are formed and spongiform tissue ensues.

Also
EEG is electroencephalogram

7 month life expectancy after diagnosis.

Spongiform tissue is formed in the cerebral cortex (personality changes), basal ganglia (gait problems), an I’m guessing the internal gray is where memories are stored?

Question 17

Three ways to test for a viral infection

Answer 17

cell culture
antibody serum test
PCR of viral nucleic acid amplificaiton test

Question 18

Pediatric patient presents will symptoms after saying his friend sneezed on him while he was very sick. What other symptoms will he show?

Answer 18

transmitted airborne
respiratory -> epithelia & lymphoid
Koplik spots
maculopapular rash - spreads from the head down
(rash is the t-cell mediated response)
temp rises with the rash, then fades
infective 14 days before and after
Three C's of Measles: cough, coryza, conjunctivitis
high fever

Question 19

A patients mother is worried her child might have mumps since she was never vaccinated. What leads you to belive this is not the case?

Answer 19

Mumps presents with a low grade fever, malaise, and enlarged parotid glands, and a headache. Transmittd similarly as measles is. Causes desquamation of the parotid epithelia

Question 20

What are six examples of latent viruses?

Answer 20

CMV, HIV, HSV1, hsv2, EBV, VZV

Question 21

So we know HSV-1 in the mouth, and HSV-2 in the genitalia, but what’s going on?

Answer 21

replication, both can live either space, goes and lives in the spinal ganglion near the infective site,

Question 22

VSV infective means?

Answer 22

nasal shedding, respiratory droplet, contact with the lesions

Question 23

What makes bacteria pathogenic?

Answer 23

endotoxins or exotoxins
endotoxin - integral parts of the bacterial cell membrane that are released upon the death of the cell. cause a non-helpful immune response and possibly DIC
exotoxin - bacterial intracellular proteins that are bad for the host cell

Question 24

Two exmples of gram positive bacteria

Answer 24

staph and strep

Question 25

staph bacteria toxins

Answer 25

alpha toxin - pore forming, exfoliative toxin - scalded skin syndrome, superantigens

Question 26

alpha-hemolytic strep

Answer 26

s. pneumo, green hemolysis

Question 27

s. pneumo

Answer 27

alpha-hemolytic, community-acquired pneumonia, otitis media, meningitis

Question 28

Beta-hemolytic strep - group A

Answer 28

Causes strep throat, PSGN – post strep glomerularnephritis, scarlet fever, rheumatic fever, impetigo, cellulitis, toxic shock syndrome, necrotizing fasciitis

Question 29

Beta-hemolytic strep - group B

Answer 29

neonatal strep, clear hemolysis (same with group A)

Question 30

What is a carbuncle?

Answer 30

a cluster of furuncles that have spread beneath the skin, heal by second intention

Question 31

What is a faruncle?

Answer 31

a deeper folliculitis, the entire pilosobaceous shaft is infected

Question 32

Small pimple or pustule is better termed as

Answer 32

folliculitis

Question 33

Hot tub folliculitis is caused by

Answer 33

gram negative pseudomonas aueriginosa

Question 34

chronic infection of the apocrine sweat glands

Answer 34

hidradenitis suppurativa
Chronic suppurative infection of the apocrine sweat glands
Most often seen in the axilla, inner thighs, groin, buttocks, and under breasts
Presents as a tender, painful, nodular area of inflammation
Progresses to open wounds and sinus tracks with sudden drainage of purulent exudate
Frequently difficult to heal, often leading to significant scarring

Question 35

Scalded skin syndrome

Answer 35

Induced by exfoliative toxins A & B
Severe complication seen in children with a primary staph cellulitis or nasopharyngeal infection
Skin desquamation causes a sunburn-like rash that spreads over the entire body and evolves into fragile bullae with associated partial or total skin loss