Lecture 1 & 2 Flashcards
What are the three points of the triangle of conflicts?
- patient
- microbes
- drug
A disease causing microbe can most commonly be acquired by a susceptible individual from what exogenous sources?
- animals
- food/water
- humans
- air/soil
What does exogenous mean?
An outside source
Colonization is the presence of microbes on the human body and does not contribute to disease. What class of microbe predominantly colonizes in humans?
Bacteria
What are the events that occur in the establishment of infectious diseases?
- encounter
- entry
- spread
- multiplication
- damage
- outcome
What does each event require?
It requires a breach of host defenses (gate keepers)
If there is a breach, what happens?
You’ll have microbes multiplying and spreading.
What is the cause of typhoid fever?
Salmonella typhi
Can Salmonella typhi be life threatening?
Yes
How many cases of S. typhi occur in the US per year? In the developing world?
5700 cases (21.5 million in the developing world)
How do sick people carry S. typhi?
They carry the organism in blood and the intestinal tract.
Describe S. typhi carriers.
They are asymptomatic, but still carry S. typhi bacteria.
How does S. typhi spread?
Via contaminated water and sewage; and by infected persons.
What is the typical incubation period of S. typhi?
60 to 90 days
What symptoms occur from S. typhi?
- fever
- malaise
- anorexia
- abdominal pain
- diarrhea
- enlarged spleen
- septicemia
- rash (in some)
Describe the carrier state of S. typhi.
Asymptomatic excretion of S. typhi in feces for over 1 year (3% of infected)
Who was Typhoid Mary?
Mary Mallon–a cook who infected 47 people; 3 died. She was forced to live on a NY island for 28 years until she passed away.
What is the infection flow chart for no transmission?
exposure –> incubation period –> no illness/illness –> infection clears –> no transmission
What is the infection flow chart for asymptomatic transmission?
exposure –> incubation period –> no illness/illness –> colonization or carrier state develops –> asymptomatic transmission
What is the infection flow chart for symptomatic transmission?
exposure –> incubation period –> illness –> symptomatic transmission
What is the relationship from patient to microbes?
host defenses
What is the relationship from microbes to patient?
morbidity
What are supportive measures?
Treatments other than drugs
What supportive measures can be done in the case of an S. typhi infection?
- oral/IV hydration
- anti-pyretics
- appropriate nutrition
- blood transfusions
What anti-microbial therapy can be done in the case of S. typhi infection?
*fluroquinolones (ciprofloxacin, perfloxacin) ; more effective than ampicillin, amoxicillin, and bactrim
What is encounter?
Sterile existence in the mother’s womb
What protection is there in encounter?
- placenta (fetal membrane)
* blood is sterile
When is the first encounter with microbes at birth?
- vaginal canal (during birthing)
* contact with mother/family care
What does the mother’s circulation provide to the fetus?
Passive protection of immunological for 6 months. After that, humans are on their own.
Describe an endogenous encounter.
Some microbes are normally found on our skin or mucous membranes (normal flora)
Why is it good for microbes to colonize humans?
Some species are good and that is great. However, there are some bad microbes.
How do you make a distinction between colonization versus infection?
- no clear distinction
* pathogens vs opportunists (commensals/breaching)
What is exogenous?
external factors that originate outside the organism
What is endogenous?
growing or originating from within an organism
What various ways can disease causing microbes be acquired from the environment (exogenous)?
- food
- water
- air
- insect bites
- animals
- humans
Infection is predominantly acquired from…
…an infected person (symptomatic) or a carrier (asymptomatic) through inhalation or contact (ingestion or sexual).
Are most body sites sterile?
Yes
What body sites are not sterile?
- digestive tract
* lower genitourinary system
What is ingress?
entry to mucosa occurs from a portal of entry (mouth, nose, or genitalia)
What is penetration?
microbes gain direct access to a sterile site, crossing an epithelial barrier and go into blood–an example is sharing dirty needles
What are some examples of ingress?
- respiratory or salivary spread (not readily controllable)
- fecal-oral spread (controllable by public health measures)
- venereal spread (genital to genital contact) – difficult to control as social factors are involved
What are some examples of penetration?
- vector (biting arthropod) – examples are malaria, sandfly fever, and typhus
- vertebrate reservoir (dog to human or farmers with sheep) – examples are rabies and Q fever
- vector-vertebrate reservoir (flea to mouse to human) –examples are plague and yellow fever
Describe ingress inhalation.
Inhalation of infective droplets either large or small can arrive in lower reaches of the respiratory tract.
What host defense mechanisms are there against ingress inhalation?
- cough reflex
* upward sweeping action of ciliary epithelium and upward flow of mucus
What is the chemical disinfect chamber in humans?
The stomach–it is host defense I–the acid in the stomach
When microbes escape the stomach, where do they go?
They enter the duodenum, but in reduced numbers. This is where host defense II is–pancreatic enzymes and bile salts in the duodenum and the sweeping force of peristalsis.
What are the different host defenses of ingress ingestion?
#1--acid in the stomach #2--pancreatic enzymes and bile salts in the duodenum and the sweeping force of peristalsis
How can penetration happen?
- Microbes pass directly through multi-layered skin epithelia (insect bites)
- Deeper invasion into the bloodstream via organ transplants and blood transfusions.
What happens during spread/dissemination?
Microbes use a variety of arsenals to penetrate into the deeper tissues (mucosa –> lymphatics –> blood stream –> end organs (liver))
What is multiplication?
Microbes multiply to a large number that can overwhelm the immunological defense system. (very few microbes survive initial host barriers, chemical and immunological onslaughts to make it to this point)
What are the two types of damage microbes can do?
- direct
* in direct (inflammation)
Describe direct damage.
- caused by microbial toxins
* inflicts cell death through: direct action of toxins or programmed cell death (apoptosis)
Describe indirect damage.
- meant to control infection via a local response to cellular injury
- serves as a mechanism initiating the elimination of microbes and of damaged tissue
What is inflammation useful for?
- wounds
* wound healing
Describe systemic inflammation.
It can be life threatening.
