Infectious Disease Flashcards
What features of the skin provide protection against invaders?
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
Most microbes gain entry via
Mechanical injury to the epidermis
Changes to its natural environment (ex. change in normal flora)
Urinary tract is protected from microbes via
sterile urine and frequent micturition
Urinary tract infections (UTI) spread in retrograde fashion
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
The female genitalia is protected from pathogens via
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
Pathogens gain entry via sexual contact or local changes that alter natural defenses of the squamous epithelium . Examples?
- Antibiotics kill normal protective flora, allowing overgrowth of yeast
- Changes in pH can alter balance of normal flora, allowing for bacteria overgrowth (STIs, inflammation, trauma)
- Some viruses cause proliferation of immature epithelial cells that are susceptible to infections
- Organisms that cause STIs commonly adhere to the surface epithelium and proliferate
respiratory tract protection
mucociliary blanket lining
resident macrophages or recruited neutrophils
Pathogens gain entry via inhalation, and with associated changes that alter natural defenses. Examples?
- Aspiration
- Chronic damage to mucocilia (ex. smoking, CF)
- Bacterial toxins that impair ciliary action (ex. Mycobacterium, Bordetella, Haemophilus)
- Immunodeficient states
- Organisms that evade phagocytosis and clearing - TB
- Direct trauma related to mechanical ventilation and intubation (trauma to epithelial lining causes lacerations and associated inflammation)
GI defenses:
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
Staph
Secretes enterotoxins without multiplying, causing enteritis
E. coli, V. cholera
Adhere to mucosa and locally proliferate, Exotoxin release causes large amounts of fluid release
Shigella, Salmonella, Campylobacter, Entamoeba
Adhere to and invade mucosa causing inflammation, ulceration, and hemorrhaging = dysentery
polio virus
“Hijacks” immune system through lymphoid channels causing lymphadenopathy and systemic manifestations via Payer’s patches and M cells
What are the three types of vertical transmission?
placental-fetal - affect the baby according to trimester and developmental stages
delivery - most common with STIs
postnatal - nursing, CMV, HBV, HIV
mechanism of microbial damage to host cells
- Microbes release toxins that degrade local tissues, damages blood vessels, or cause tissue ischemia
- Secrete lytic enzymes that cause death to host cells, destroy local tissue and/or allows local tissue invasion
- Ensuing immune response directed towards the invading organism may also cause further local damage to host cells and tissues - super antigens
- Local bacteria may disseminate to distant sites by traveling within host cells or within extracellular fluid like blood and lymph - sepsis!
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.
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?
Three ways to test for a viral infection
cell culture
antibody serum test
PCR of viral nucleic acid amplificaiton test
Pediatric patient presents will symptoms after saying his friend sneezed on him while he was very sick. What other symptoms will he show?
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
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?
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
What are six examples of latent viruses?
CMV, HIV, HSV1, hsv2, EBV, VZV
So we know HSV-1 in the mouth, and HSV-2 in the genitalia, but what’s going on?
replication, both can live either space, goes and lives in the spinal ganglion near the infective site,
VSV infective means?
nasal shedding, respiratory droplet, contact with the lesions
What makes bacteria pathogenic?
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
Two exmples of gram positive bacteria
staph and strep
staph bacteria toxins
alpha toxin - pore forming, exfoliative toxin - scalded skin syndrome, superantigens
alpha-hemolytic strep
s. pneumo, green hemolysis
s. pneumo
alpha-hemolytic, community-acquired pneumonia, otitis media, meningitis
Beta-hemolytic strep - group A
Causes strep throat, PSGN – post strep glomerularnephritis, scarlet fever, rheumatic fever, impetigo, cellulitis, toxic shock syndrome, necrotizing fasciitis
Beta-hemolytic strep - group B
neonatal strep, clear hemolysis (same with group A)
What is a carbuncle?
a cluster of furuncles that have spread beneath the skin, heal by second intention
What is a faruncle?
a deeper folliculitis, the entire pilosobaceous shaft is infected
Small pimple or pustule is better termed as
folliculitis
Hot tub folliculitis is caused by
gram negative pseudomonas aueriginosa
chronic infection of the apocrine sweat glands
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
Scalded skin syndrome
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
