Infectious Disease Flashcards
What are the 3 types of microorganisms?
1) bacteria
2) viruses
3) fungi
What is the broad name/category for most bacteria in the body? What does this mean?
commensal bacteria
It lives symbiotically with you and causes no harm, its your own natural flora in gut, skin, vagina, etc.
Specifically, what type of bacteria is in our flora?
lactobacillus “good” bacteria
What do commensal bacteria secrete?
commensal bacteria secretes toll-like receptor (TLR) ligands which bind to TLR on the surface of normal intestinal tissue
Where does commensal bacteria bind to and what does this allow?
binds to the epithelium of the gut and allows signaling for repair, protection of injury, etc.
What does it mean for the body if TLR signaling is intact?
TLR ligands will bind to TLR and cause basal signaling
this leads to homeostasis of the intestinal surface and robust repair in response to injury
Describe what happens if TLR signaling is disrupted
TLR ligands will bind to TLR, but no signaling will occur/no activation of signaling
this will cause enhanced sensitivity to injury and diminished capacity to induce repair
What does it mean if there is no TLR signaling in the gut?
There are no ligands binding to TLR, so basal signaling is inactive and does not occur
this will lead to enhanced sensitivity to injury and diminished capacity to induce repair
What does basal signaling do in simplest terms?
protects against cellular injury
What is an example that may disrupt TLR signaling?
antibiotics can eradicate commensal bacteria which results in compromised ability of the intestinal epithelium to withstand injury and repair cell damage
What happens to the body if antibiotics disrupt your natural flora?
body will be more susceptible to bacterial infections, such as C. diff
What does C. diff cause?
Hint: think in terms of when the natural flora is disrupted through antibiotics
pseudomembranous colitis and candida overgrowth
Where in the body is it sterile (no commensal bacteria)?
blood, CSF, kidneys, bladder, female fallopian tubes/ovaries
How is infection typically transmitted?
through direct contact, such as touch or sex
or through fomites (inanimate objects such as medical instruments, bed linens, etc.
List at least 3 ways infections are spread
in no specific order:
1) needle or injury (direct access to blood)
2) bites, stings or worms (direct access to blood)
3) animals (vector-borne)
4) sexual intercourse
5) ingestion (contaminated soil/water, poultry, eggs, oral/nasal secretions, etc)
6) inhalation (oral/nasal secretions)
What is an example of infection that inhales microbes through nasal/oral secretions?
TB
What is an example of infection that uses a vector, or in other words animal/insect intermediate?
malaria
What is an example of a microorganism that can cross the placenta? What infection does it cause?
Treponema pallidum causes Syphilis
this can really infect the fetus and cause neuro damage or fetus can even die in utero
What are nosocomial infections?
any infection acquired within a hospital or medical facility
What is the most common nosocomial infection? What are the secondary infections that are also fairly common?
most common= staph causes UTIs
secondary= wound infections, pneumonia, or diarrhea
What is the most common serious nosocomial infection? Secondary infection?
most common= MRSA (Methicillin-resistant staphylococcus aureus)
second most common= C. diff
How easy is it for C. diff to enter the body? What happens once a pt has C. diff?
once the bacteria gets in the body, it’s very easy to get through the stomach (entrance is easy if pt is susceptible to infection)
C. diff causes pseudomembranous colitis, which results in diarrhea, abdominal pain, and high fever
What are the 3 ways bacteria can infect you?
1) secrete toxins
2) secrete enzymes
3) become spores
some bacteria can do more than 1 of these options
What are the toxins that bacteria secrete?
exotoxins or endotoxins
What type of bacteria typically secretes exotoxins?
Hint: it is either gram pos or neg
gram positive bacteria
How are exotoxins released/distributed into body?
they diffuse through tissues and in body fluids
What is an example of an exotoxin?
neurotoxins
What is an example of a neurotoxic bacteria?
Clostridium tetani (C. tetani)
What does C. tetani cause?
causes tetanus
it does not kill any cells, but rather enters the cells and disrupts metabolism
It inhibits neurons (this is called opposed neurons), where one neuron is fired off and the opposite neuron is inhibited
What is a classic sign of tetanus?
lock jaw which is caused from muscular rigidity because neurons are being inhibited and this impacts the muscles
What type of bacteria typically secretes endotoxins?
Hint: it is either gram pos or neg
gram negative bacteria
How are endotoxins released into body?
they are only released once/if the bacteria dies
What can release of endotoxins lead to?
minor symptoms such as fever, weakness, etc.
huge inflammatory response (release of lots of cytokines)
What happens if the body doesn’t take care of endotoxins right away?
the endotoxins will make it to the bloodstream and due to its huge inflammatory response, this can lead to septic shock
What are 2 examples of an enzyme that some bacteria can secrete?
collagenases (which break down collagen in the body)
hemolysins (break down RBCs)
What is a bacteria we learned in class that can secrete collagenases?
C. histolytieum
collagenases break down collagen, so in this case it will cause gas gangrene
Are bacteria spores hard to destroy?
YES!!!!! unfortunately
What are 2 examples of bacteria that can become spores?
C. tetani and C. botulinum
What bacteria did we learn in class that has multiple infectious routes?
C. tetani can secrete exotoxins (specifically neurotoxins) or become a spore, depends on the environment
Where does C. tetani typically form spores?
the soil
we can get infected by this through ingestion
What does C. botulinum cause? Where does it typically form spores?
causes botulism which can occur from eating expired canned foods or damaged/seal broken canned foods
Clostridium is just sitting there and eventually will cause illness because it can protect itself since it is a spore and it’s hard to destroy
What are viruses?
Hint: think in terms of microbiology
obligate intracellular parasites (have to get into your cells to infect you, viruses are not alive)
What are two types of infections viruses can cause?
chronic and latent infections
What is an example of a chronic viral infection?
Hep B
What is an example of a latent viral infection?
Varicella zoster (causes chicken pox and the latent infection you can get afterwards is shingles)
This is because it sits in the dorsal root ganglia and something must trigger the inactive virus to become active again after having chicken pox, and so this trigger can cause shingles
What is an example of a viral infection that has multiple strains?
the flu
T/F:
In some cases, viruses can change the DNA of cells in order to become malignant
True!
What is an example of a viral infection that can lead to change in DNA and malignancy? List a few cancers that it causes
HPV (human papillomavirus) most often leads to cervical cancer
It can also cause throat or oral cancer and this is common in both genders
What are the stages of infection?
1) incubation period
1A) prodromal period (only some pt)
2) acute phase
3 outcomes:
3A) full recovery or short convalescent period
3B) chronic infection
3C) death
What is the incubation period of infection?
it is the time from the pathogen entering the body to first sign/symptom onset
this is when the pathogen enters the body, colonizes, and multiplies
What is the prodromal phase of infection?
this is the stage after incubation period where SOME patients (not all) will experience mild symptoms of “not feeling well” or “coming down with something” but cannot actually pinpoint symptoms
What is the acute phase of infection?
this is when all signs and symptoms have manifested and its becoming evident that the pt has some type of infection
What are the 3 possible outcomes after the acute phase of infection?
3A) total recovery or a short convalescent period
3B) develops into chronic infection
3C) pt dies from infection
How long is the incubation period of infection?
anywhere from a couple days to weeks
How long is the prodromal phase of infection?
typically lasts only a few days
What does the acute phase of infection duration depend on?
pt immune system and/or medical intervention
acute phase length varies among each pt
What is the medical term for death from infection?
septicemia
If a pt has an acute infection and they begin to show signs of recovery what does this mean for the pathogen?
decreased reproduction and death of pathogen
host defenses take effect
nutrient supply decreases
wastes and cell debris increase
antibacterial drug
If a pt comes into your office with an infection, how are you going to correctly diagnose this?
Ex: you suspect pt has a wound infection, throat, or oral infection
options:
1) C&S (culture and sensitivity)
2) send pt home w/ broad spectrum antibiotics while C&S is being processed (or guess and give them something more specific)
3) blood culture
4) blood test (CBC w/ diff)
5) X-ray
What is a C&S?
take culture in office and send it to lab so they can test sensitivity
this will tell you what infection the pt has, what microorganism it is and what medication it is susceptible to
depending on microorganism it may take a few days to grow- (what should you do in this case? Send pt home with broad spectrum antibiotics or guess on microorganism if you have enough experience)
When should you do a blood culture if you suspect a pt has an infection?
only do a blood culture if you think the microorganism has entered the bloodstream
What blood tests should you be doing if your suspect a pt has an infection? What should you be looking out for?
do a full CBC panel w/ diff (this means WBCs, RBCs, and platelet count, as well as differential for each WBC type)
look out for:
- leukocytosis
-elevated neutrophils, lymphocytes, monocytes, CRP and SED rate, etc.
-leukopenia
-Abs
What is leukocytosis?
increase in WBCs, so if its elevated = infection
What do elevated neutrophil count mean?
acute infection
What do elevated lymphocytes/monocytes mean?
chronic infection
What is leukopenia?
decrease in WBCs/ WBC deficiency
What does CRP stand for?
C- reactive protein
What is another name for SED rate?
ESR- erythrocyte sedimentation rate
What does elevated CRP and SED rate mean?
some kind of inflammatory process
What are X-rays typically used for in terms of infection diagnosis?
pneumonia or TB
T/F:
only some microbes can infect the GI tract
FALSE
any microbe can infect GI tract
How long do most infectious diarrhea cases last? Does anything help it?
most last 2-3 days, OTC meds should help w/ N/V and diarrhea
What happens if you have infectious diarrhea for over a week? What is a major complication that can arise if left untreated?
leads to dehydration and electrolyte imbalance
complication: cardiac failure
Who is most vulnerable to infectious diarrhea?
elderly, young children, or immunocompromised
What are the 4 broad categories for GI tract infections?
1) environment
2) agent
3) host
4) site
What are the 3 environmental categories for GI tract infections (mode of transmission)?
1) water-borne
2) food borne
3) person to person (fecal oral spread)
What are the 3 agent categories for GI tract infections?
1) bacterial
2) viral
3) parasitic
What are the 3 sites for GI tract infections?
stomach, small intestine, large intestine
What type of diarrhea is produced through the small intestine if it is infected?
very copious amounts of watery diarrhea
ex bacteria that would cause this: V. cholerae
What type of diarrhea is produced through the large intestine if it is infected?
inflammatory or hemorrhagic diarrhea
Give an example on a bacteria that will cause diarrheal disease
Escherichia coli (E. coli)
name this bacteria:
a part of your bacterial flora, and if it overgrows it can cause diarrhea
Escherichia coli (E. coli)
How does gastroenteritis differ from E. coli diarrheal disease?
gastroenteritis also causes diarrhea but it is an infection of the stomach and upper portion of the small intestine
w/ gastroenteritis you will still have nausea and abdominal pain, but it can be treated quicker than infections in the lower GI tract
What is the most common cause of diarrheal disease in the world?
Escherichia coli (E. coli)
What is the most common cause of gastroenteritis in the US?
norovirus or rotavirus on cruise ships
What are the 3 types of infectious diarrhea? Where is this infection?
infection in small or large intestine
1) hemorrhagic diarrhea
2) secretory diarrhea
3) inflammatory diarrhea
T/F:
hemorrhagic diarrhea is actually a subcategory of inflammatory diarrhea
true
Hemorrhagic diarrhea is usually from an infection where?
large intestine
What bacteria usually causes hemorrhagic diarrhea?
Escherichia coli (E. coli)
How many toxins does E. coli produce? What do these toxins do?
E. coli produces 2 different types of toxins
these toxins can cleave your RNA and disrupt protein synthesis which ultimately kills the cells
What is the primary function of large intestine?
to absorb water
What happens to the toxins secreted from E. coli?
they will get into bloodstream and will undergo phagocytosis by neutrophils
for some unknown reason, neutrophils will also undergo endocytosis by the endothelial cells in the blood vessels
What happens once the toxins secreted from E. coli get into the walls of blood vessels?
it will start to destroy the walls of blood vessels
this will cause an inflammatory process called vasculitis
this is where bleeding comes from and why its called hemorrhagic diarrhea
Secretory diarrhea can be caused by….
1) bacteria (ex: V. cholerae)
2) viruses (ex: norovirus)
3) protozoa (ex: giardia)
What is giardia?
tiny parasite (germ) that causes the diarrheal disease giardiasis
If you drink/ingest contaminated water, you will most likely develop a _______ infection
hint: bacterial, viral, or protozoan
protozoan
if you drink/ingest contaminated water, you will most likely develop a protozoan infection
Vibrio cholerae (V. cholerae) and enterotoxigenic E. coli (ETEC) toxins have how many subunits? What are they called?
2 subunits: A and B
What two bacterias share a similar pathogenetic mechanism in causing diarrheal illness?
Vibrio cholerae (V. cholerae) and enterotoxigenic E. coli (ETEC)
How does Vibrio cholerae (V. cholerae) and enterotoxigenic E. coli (ETEC) bacteria gain entry into the body? How do they attack?
through ingestion of contaminated food and moves down the GI tract where it “attacks” in the small intestinal lumen
they release an enterotoxin that is composed of one A subunit and 5 B subunits
Describe process of A/B subunits in Vibrio cholerae (V. cholerae) and enterotoxigenic E. coli (ETEC) bacteria releasing enterotoxins?
The B subunits bind to the intestinal cell membrane and facilitate entry of part of the A subunit
this results in a prolonged activation of adenylyl cyclase and the formation of cyclic adenosine monophosphate (cAMP), which stimulates water and electrolyte secretion by intestinal endothelial cells
Where are GPCR typically found?
gut tissue
List the 5 textbook steps for GPCR-adenylyl cyclase signal transduction and amplification
1) signal molecule binds to GPCR, which activates the G protein
2) G protein turns on adenylyl cyclase, an amplifier enzyme
3) adenylyl cyclase converts ATP to cyclic AMP
4) cAMP activates protein kinase A
5) protein kinase A phosphorylates other proteins, leading ultimately to a cellular response
What does Vibrio cholerae (V. cholerae) and enterotoxigenic E. coli (ETEC) bacteria do to GPCR?
normal cell process (last step of normal GPCR)= once you activate the G protein, the A subunit is released and binds to something else
in bacteria= the toxin will signal to the subunit to bind to GPCR, GDP falls off and the subunit binds to adenylyl cyclase, but never leaves (it stays on continuously)
the toxin never releases itself from receptor, so then adenylyl cyclase converts ATP to cAMP
cAMP activates protein kinase A and carries out cell response, which in this case would be continuous activation of adenylyl cyclase, breakdown of ATP to cAMP, production of kinases and phosphorylations
this all keeps cystic fibrosis transmembrane regulator (CFTR) protein channels open continuously (obviously not good)
What is NKCC2?
its a normal pump within the body, stands for sodium potassium 2 chloride pumps
What are the 4 textbook steps for NKCC2 system in the lumen/intestinal cells?
1) Na+, K+, and Cl- enter by cotransport
2) Cl- enters lumen through CFTR channel
3) Na+ is reabsorbed
4) Negative Cl- in lumen attracts Na+ by paracellular pathway, water follows
How did we discuss NKCC2 system in class? Normal process only
chloride travels from interstitial fluid through the cell and out to the lumen, potassium enters cell from interstitial fluid and then back out to fluid
sodium pumps from fluid into cell, back out to fluid and then between cells (paracellular method=between)
there are so many anions leaving that Na+ follows, so water does too (because water always follows sodium)
What happens once the NKCC2 system is done?
hint: all chloride that was needed to be removed was a removed, now what?
the channels close and stop
How does Vibrio cholerae (V. cholerae) and enterotoxigenic E. coli (ETEC) bacteria affect the NKCC2 system? What does this lead to?
they keep the CFTR channels open continuously (Cl- always leaving, Na+ leaving and water always following)
copious amounts of water leads to an incredible amount of secretory diarrhea which destroys the cells and does not allow them to absorb water (hijacks the system)
this leads to volume/electrolyte depletion and dehydration, additionally, blood is primarily water, so when water is being depleted, blood is too and this causes a decrease in BP, in severe cases a pt can die from this
What is it called when there is lots of water loss with Vibrio cholerae (V. cholerae) and enterotoxigenic E. coli (ETEC) bacteria
hint: SECRETORY DIARRHEA
this is known as rice water stools because the diarrhea is so watery and white
What is the easiest treatment for secretory diarrhea caused from Vibrio cholerae (V. cholerae) and enterotoxigenic E. coli (ETEC) bacteria?
saline solution (IV bag)