Intro to Bacteriology: Flora and Pathogenesis Flashcards
Initial Colonization of Host
Wjere do microbes come from in the womb?
- Uterus is usually sterile
- Fetal membranes break, and fetus is exposed to vaginal flora during birth
- 8-10 hours after deliver, newborn is colonized by many microbes
Indigenous Flora Characteristics
Two types of flora
Microbes commonly found on or in the body of a healthy person
Resident flora: colonize the site for months/years
Transient flora: temporary colonizers, which are eliminated
Human Microbiota
3 times more bacterial cells than human cells
Microbiota includes viruses, fungi, archaea, single-celled eukaryotes.
Gut Microbiome and Health and Disease
Host-microbial interactions maintain health, if disrupted > illness
Gut microbiome changes induced by diet, antibiotics, immune, genetics
Dysbiosis: influence bioavailabilty/efficacy of therapeutic drugs
What Influences Microbiota Type and Number on the Body
6 things
- Oxygen availability
- Receptor sites for attachment
- pH
- Nutrient availability
- Influence of other microbes at thte site
- Immunological response of host to the microbe
Role of Normal Flora
3 things
- Immune stimulation
- Keep out invaders
- Human nutrition/metabolism (gut flora)
How Gut Flora Benefit Human Hosts
5 ways
- Synthesize essential metabolites
- Break down plant fibers
- Inactivate toxic substances in food or made by pathogens
- Prevent pathogens from benefiting from the resources of the human gut
- Interact with epithelium to trigger development of secondary lymphoid tissue
Koch’s Postulates
Diseased organism can be cultured, and that culture can be inoculated into a healthy organism, and that organism will get the disease
Course of Infectious Disease
5 steps
Incubation: time from eposure to onset of symptoms, dependent on infection
Prodromal: incubation period and before the characteristic symptoms of infection, can transmit to other people, mild and nonspecific response
Illness: displaying symptoms of infection, dependent of type, dose, and host immune response
Decline: immune system successfully defends, symptoms improve, secondary infections may occur
Convalescence: symptoms resolve, normal functions or damage
True Pathogen
Primary pathogen
Causes disease in a healthy person
Opportunistic Pathogen
Typically part of normal flora
Causes disease when:
- Immune system weakened
- New microbe introduced and disrupts flora
- Breakdown of defense barriers (catheters)
Timing of Infections
3 timings
Acute infections: develop quickly
Subacute: more suddenly than chronic but less than acute
Chronic: insidious onset, maybe even years, lasts a long time
Latent: silent or dormant stage, go from symptomatic to asymptomatic back to symptomatic
How Infectious Diseases Take Place
Four steps
Encounter/acquisition: agent meets and colonizes host surface
Attachment: agent multiplies and breaches defenses
Dissemination: agent penetrates deeper and comes in contact with immune response
Outcome: agent or host wins during infection, or coexist
Outcome depends on host health or pathogenicity of agent
Types of Acquisition
2 types
Endogenous: caused by agents in or on the body
Exogenous: agents in the environment
Contact Transmission
Direct skin to skin, mucous membrane to mucous membrane, fecal-oral, transfusion
