Unit 1: Chapter 2 Basic Concepts of Infectious Disease Flashcards
Is E. Coli a disease causing organism?
Yes and no.
- E. Coli k12*- Part of your normal microbiome
- E. Coli 0157-* Pathogenic (disease causing)
It basically depends where on your body it is. If K12 were to get in your digestive tract or urinary tract, then it can be bad despite is always be a part of your normal microbiome. On the latter end, despite 0157 being pathogenic, if it were to be on your hands, then it is not bad, but as soon as it gets somewhere its not supposed to be, then it can be bad.
What is a collection of prokaryotic and eukaryotic microbes usually colonizing our bodies, but not causing any harm?
Normal Microbiota
T or F: Most of our body is human cells
False; most of our body is microbial
What is mutualism?
A relationship in which both the community members and host benefit
What is a pathogen?
Any bacterium, virus, fungus, protozoan, or worm (helminth) that causes disease
Pathogenicity is the ability of an organism to cause disease.
What does this depend on?
- genetic makeup of host and pathogen
- location in/ on the host’s body
- host immune response
Primary Pathogens
Due to their structures in them, they are able to breach defenses of a completly healthy host
Ex. E. Coli 0157
Opportunistic Pathogens
Are able to cause disease only in a compromised host
Like your microbiome; if it ends up in the wrong place or your immune system is compromised, then it can cause disease
Latent State
Organism is within the host, but cannot be detected by culture; its hiding in your body until your immune system is compromised
Ex. Herpes Virus
Parasite
Any organism that colonizes and harms its host
Ectoparasite
A parasite living outside the body of the host
Ex. bedbugs, lice, fleas, ticks, etc
Endoparasite
Parasites living on the inside of the body of the host
Infection
A pathogen or parasite that enters or begins to grow in/on a host.
Do all infections cause disease?
No. The virulence of the pathogen determies whether it’ll cause disease or not.
- It does not imply overt disease
- May go unnoticed
- Is often temporary
Virulence
a measure of the degree of severity of disease
The smaller the # of virus particles it takes for a lethal dose/infectious dose, the more virulent it is.
Lethal Dose 50% (LD50)
The number of bacteria or virus particles required to kill 50% of an experimental group of animal hosts
Infectious Dose 50% (ID50)
The number of bacteria virus particles needed to cause disease symptoms in 50% of an experimental group of hosts
Invasion
The ability of some pathogens to actually enter and live inside a host CELL
Invasiveness
The ability of a bacterial pathogen to rapidly spread through tissue
What are the steps to cause disease?
- Entry
- Attachment
- Evade immune system
- Obtain nutrients
What are the portals of entry of a pathogen?
- Fecal-oral
- Skin
- Respiratory
- Irogenital
- Parenteral
Portals of Entry for Pathogen: Fecal-Oral
Through musosal surfaces of GI tract
Has to survive HCL in stomach, but it still fairly common
Portals of Entry for Pathogen: Skin
Through epithelial surfaces
Very hard to enter on good health skin and is the least common way a pathogen enters
Once the skin is compromised, a pathogen can enter
Portals of Entry for Pathogen: Respiratory
Through mucosal surfaces of respiratory tract
The most common entry for pathogens
Portals of Entry for Pathogen: Urogenital
Through mucosal surfaces of genital and urinary tracts
Portals of Entry for Pathogen: Parenteral
Through injection into the bloodstream
Enters though compromised skin
Ex. insect bites; wounds/needle sticks
Attachment of a pathogen to a host
Pathogens attach via ADHESIONS; looks for weak points on or in cells to attach
Pathogens have adhesions that bind to specific host cell receptors that allow them to stay with the host; if there is a lack of receptors, then pathogens cannot attach; where you get infected depends where the receptors are
Colonization
Refers to the ability of the microbe to stay attached to the body surface and replicate
Determine Host Range
Ability of the pathogen to infect as few (narrow host range) or as many (broad host range) and produce disease
Immune Avoidance; Evade the immune system
Altered surface antigens; change the shape to confuse the immune system
Secreation of “all is well”
Signals apoptosis; secreate proteins that convince the immune system cells to kill themselves
This is when the pathogens tries to avoid the immune system so that it can cause infection or disease
What nutrient is the pathogen wanting to obtain from the host?
Iron (Fe)
What does a pathogen have that helps it obtain iron?
Sideophorso
This has a higher affinity for Fe and allows for it to steal iron from the host
How does the host hide iron from the pathogen?
Hidden in hemoglobin; transferrin; binds free Fe to keep away from pathogens
Lactoferrin; found in breast milk; binds fee Fe to keep away from pathogens
Anything that ends with _________ helps keep iron (Fe) away from the pathogen
-ferrin
Disease
Disruption of the normal structure or function of any body part, organ, or system that can be recognized by a characteristic set of symptoms and signs
Ex. Diabetes, cancer, CHF, Alzheimer’s, etc
Infectious Disease
A disease caused by a microorganism that can be transferred from one host to another
Something caused by a pathogen
Ex. Flu, COVID, measles, strep throat, etc
Stages of an Infectious disease
- Incubation phase
- Prodromal phase
- Illness phase
- Decline phase
- Convalescent phase
- Long term
Stages of an Infectious disease: Incubation Period
Time after the microbe first infects a host, but before the signs of a disease
At this point, you and your immune system doesn’t know you are sick yet
Stages of an Infectious disease: Prodromal Phase
The short period of vague symptoms and malaise; can serve as a warning of more symptoms to come, but may not be noticed
At this point, you begin to not “feel right”; this phase doesn’t always happen with all diseases
Stages of an Infectious disease: Illness Phase
Typical symptoms and signs of the disease appear and fever may be present
What is acme?
This is the point where the disease is most severe
The PEAK of the illness
Stages of an Infectious disease: Decline
Symptoms begin to subside; fever is resolved
Host factors in disease
- Age; very young or very old most susceptible
- Host Genetic Makeup; host receptos to which bacteria and virus bind
- Host Hygiene and Behavior
- Nutrition and Exercise
- Underlying Non-Infectious Diseases or Conditions; genetic defects in immune system, chronic infections, diabetes, alcohol use, cancer, etc
- Occupation; healthcare works, lab personnel, hunters, etc
- Immune Status and Immunopathogenesis; immune respnse to pathogen, immunosuppressant drugs
Stages of an Infectious disease: Convalescence
Period after symptoms disappear and the patient recovers
The pathogen is not completely out of the hosts system, but the body begins do more repairing than anything
Stages of an Infectious disease: Long Term
Adaptive immune system fights off that same pathogen if it enters again in the future
Sign vs. Symptom
A SIGN is something that can be observed by a person examining a patient (ie. running nose, rash, etc)
A SYMPTOM is something that can only be felt by the patient (ie. pain, fatigue, etc)
What is a syndrome?
A collection of signs and symptoms that occur together and signify a particular disease or infection
What is the infection cycle?
The route of transmission an organism takes to infect additional hosts
Direct Contact Transmission of a Disease
Organisms that spread from person to person
What are the 2 types of direct contact transmission?
- Horizontal; from person to person via droplets, sexual intercourse, etc or from animal to person
- Vertical; from mother to child
What is indirect transmission?
It is when organisms spread indirectly through intermediary, which may be living or non-living
What are the two types of non-living (vehicle) ways of indirect transmission?
- Formite; any inanimate object (ie. you sneeze on your hand, then touch a door knob and spread)
- Medium; food, water, air
What is the living way that microbes may be spread indirectly?
Vector
This is things like ticks, mosquitos, etc (insects)
What is a mechanical vector?
It is an indirect way to transmit disease by landing on contaminated material and then carrying any pathogens present to a living host such as a human, animal, or food
What is the reservoir of infection?
Any environment (living or non-living) where you can find the pathogen
What is a carrier?
A person who harbors a potential disease agent, but does not have any signs or symptoms of disease; can transmit
Zoonotic Diseases
Infections that normalt afflict animals, but can be transmitted to humans; can affect humans through accidental transmission
Typically contracted after encountering the animal reservoir (ex. bubonic plague, Lyme disease, rabies, etc)
What is an endemic?
A disease that is always present in a community and seen at a low rate; often harbored in an animal reservoir
Seen all the time, but in low numbers
What is an epidemic?
When there are many cases developing in a short time
Big spike for a short period of time
What is a pandemic?
An epidemic that spreads worldwide
Ex. flu, bubonic plague, HIV, covid
Biosafety Groups
Groups ranked by the severity of the diseases and ease of transmission
Biosafety Groups: Group I
Little to no pathogenic potential
Generally doesn’t cause disease unless you were to be severely immune compromised
Standard sterile techniques and lab practices
Biosafety Groups: Group II
Greater pathogenic portional, but vaccines and treatments are readily available
Can be severe especially in immunocomporused people, but there is treatment for it
Use biolaminar flow cabinets during experiments and try to limit access in and out of the lab
Biosafety Groups: Group III
Serious or lethal human disease for which vaccines and treatments may be available
Use of negative pressure rooms (only air can flow in), regulated access in the lab and may use double door air locks
Biosafety Groups: Group IV
Extremely dangerous pathogens for which no treatments or vaccines are available
There is a whole separate facility for level 4 pathogens. Positive pressure suits are used so that contaminates are blown away from the person and are unable to get in.
Are all infectious diseases known to us?
No; there are new diseases which are continually emerging or re-emerging
What is an emerging diseases?
Any pathogen that has not been seen in the past, or might have been seen in the past, but in very small populations
Ex. ebola, covid, etc.
What is a re-emerging disease?
A pathogen that has been seen in the past, numbers went down, and then it comes backs.
Ex. measles, whooping cough, etc
What is deforestation and urban sprawl doing?
It is creating breeding areas for mosquitos and is bringing humans closer to disease reservoirs and vectors
How does temperature changes and/or drought or excessive rain further the spread of certain pathogens?
It further the spread of certain pathogens bu affecting the geographic distribution of insect and other animal vectors.
Morbidity
The existence of a disease state and the rate of incidence of the disease
Incidence
The new cases of the disease that develops during the course of the year
Mortality
A measure of how many patients have died from disease
