Midterm Flashcards
Some characteristics of Microbes include:
microscopic, phylogenetic diverse, metabolic diverse, can be beneficial, and can live in a symbiotic relationship with us
Microbiota means
collection of microbes colonizing our bodies without normally causing disease
Microbiome means
total number of microbial genomes in a defined environment
Resident Microbiota:
part of the normal microbiota throughout life; mostly commensal
Transient microbiota:
remain in/on the body for short period (in competition from other organisms, and is eliminated by the body’s defense cells)
Mutualism/Syntropy
all members benefit from the relationship
Commensalism
one member benefits, the other is unaffected
Amensalism
one member is harmed, the other is unaffected
Parasitism
one member benefits, the other is harmed
The two classes of microbes are:
1) Cellular microbes; 2) Acellular microbes
Characteristics of Acellular Microbes
Without a cell (Viruses, viroid, prions)
Require other organism to reproduce
Simple structures
Wide variety of shapes
Are ultramicroscopic
Characteristics of Cellular Microbes - Prokaryotes
Archaea and Bacteria
Common shapes (spheres, rods, spirillum, spirochete, vibrio)
Lack nucleus and membrane-bound organelles
<1.0 um in diameter
Key organelles of the Prokaryotic cell (7)
- Flagellum
- Ribosome
- Nucleoid
- Plasma membrane
- Cell wall
- Cytoplasm
- Glycocalyx
Characteristics of Cellular microbes - Eukaryotes
Algae, Protozoa, Fungi
Wide variety of morphology
5-100 um in diameter
Have a nucleus and internal membrane-bound organelles
Often multiple chromosomes
Key organelles of the Eukaryotic cell (13)
- Nucleolus
- Nuclear envelope with pores
- Ribosome
- Lysosome
- Mitochondrion
- Centriole
- Golgi
- Rough ER
- Smooth ER
- Cytoplasmic membrane
- Cytoskeleton
- Vesicles
- Cilium
Primary Pathogens …
cause a disease in healthy people; infection get worse by a weak or immature immune system
Opportunistic Pathogens …
only cause diseases when given opportunity
Obligate Pathogens …
require a host to fulfil their cycle
Facultative Pathogens …
host is only one of the niches they can exploit to reproduce
What are the two categories for the Host Range of pathogens?
Narrow (can only effect one); Broad (can infect many)
Pathogenicity:
pathogens potential to cause infection or disease
Virulence:
degree or severity of disease
Highly virulent pathogens…
always lead to a disease state
Pathogens with low virulence …
more likely to result in mild disease states
Continuum:
from avirulent to highly virulent
Fatality rates =
Number of deaths
The measures of Virulence are…
Medium Lethal Dose (LD50); Medium infectious dose (ID50)
LD50:
number of pathogens required to kill 50% of an experimental group of animals hosts
ID50:
number of pathogens needed to cause disease signs in 50% of an experimental group of hosts
Disease:
disruption of the normal structure or function of any body part, organ or system
Infectious disease:
disease caused by a pathogen that caused a disruption of the normal structure of function
Infection:
condition of a successful multiplication/colonization of a host by a microorganism
Sign:
something that can be observed by a person examining a patient
Symptom:
something that can be felt only by the patient
Syndrome:
collection of signs and symptoms that signify a particular disease
Asymptomatic/Subclinical
infections lack symptoms but may still have signs of infection
Stages of Pathogenesis
Exposure, Adhesion, Damage or invading of host cells, infection, transmission
Invasion:
ability of pathogens to enter (invade) host cells
Invasiveness:
ability of a bacterial pathogen to rapidly spread through tissue
Koch’s postulates (1884):
systemic approach to confirm causative relationships between a disease and a pathogen
Molecular Koch’s postulates (1988)
inactivation of genetic factors results in diminishing virulence of the pathogen
Adapting Koch’s postulates (2016)
disease causation must take microbial interactions into account
Diseases can be classified in a number of ways (4)
Contraction of Disease
Pattern of infection and body spread
Longevity and severity of the developed disease
Outcome of the disease - mortality and morbidity
Communicable diseases:
infection spread between persons by direct or indirect mechanisms
Contagious diseases:
communicable diseases that is easily spread
Non-communicable diseases:
infection not spread between persons
Iatrogenic diseases;
infection contracted via a medical procedure
Nosocomial disease
infection acquired during a hospital stay
Zoonotic disease
infection is transmitted from animals to humans
Pattern of infection - Localized
infection confined to a body area
Pattern of infection - systemic
widespread infection in many body systems
Pattern of infection - Focal
infection site serves as source of the pathogen for a disease at another body site
Pattern of infection - mixed
multiple species contribute to infection
Pattern of infection: primary-secondary
Primary: infection in a previously healthy individual
Secondary: successive infection which can occur due to weakened immunity
Bacteremia
presence of bacteria in blood, usually transient, no replication
Septicemia
presence and replication of bacteria in blood
Viremia
presence of viruses in the blood
Toxemia
presence of toxins in the blood
Acute
pathological changes develop rapidly over hours or days
Chronic
pathological changes develop gradually over months or years and are slow to resolve
sub-acute
pathological changes take longer to develop than acute but arise more quickly than chronic
Latent
pathological changes appear a long time after infection, pathogen dormant
Morbidity
existence of a disease state and the rate of incidence of the disease
Mortality
measure of how many patients have died from a disease
5 stages of infection (in order)
Incubation Period
Prodromal Period
Illness
Decline
Convalescence
Viruses are
Obligate pathogens and can infect every organism
Narrow host range
most viruses infect only particular host’s cells
Broad host range
Generalists infect many kinds of cells or many different hosts
Non-enveloped viruses enclose by …
the capsid
enveloped viruses are wrapped in
hosts plasma membrane
Prokaryotic host infections via . . .
bacteriophages
Virulent phages trigger . . .
bacterial lysis (lytic cycle)
Temperate phages integrate into . . .
host genome
Life cycle of viruses (5 steps)
Attachment
Penetration
Uncoating
Replication
Assembly and release
Virion abundance in lytic life cycle (3 steps)
Inoculation
Eclipse
Burst
Burst size
number of virions
Viral titer
number of virions per volume
Latency
animal viruses remain dormant in host cells
Hantavirus pulmonary syndrome
rodent-borne disease infecting the lower respiratory system
Rapid mutation leads to antigenic drift … what is antigenic drift?
a population of viruses no longer recognized by host antibodies
Epidemiology examines what?
infectious diseases
Population-centered analyses focused on …
morbidity
total morbidity is
the number of diseased individuals
Incidence is
the number of new cases of a disease in that location over a specific time
Prevalence is
the total number of cases of a disease in a given location regardless of when the first case developed
Sporadic disease…
few cases within an area
endemic disease …
constant presence in a community
epidemic disease…
development of many cases in a community in a short time (outbreak)
pandemic disease …
worldwide spread of disease
Reproduction number (R0) defines…
contagiousness
when R0 <1, what happens?
disease will disappear
when R0 = 1, what happens?
endemic
when R0 > 1, what happens?
disease will spread
Spread can be modified by measures leading to the _______ __________ ________
Effective reproduction number (R)
5 Types of Pandemics discussed in class…
Black death
Smallpox
Spanish Flu
HIV/AIDS
COVID-19
Who is the father of Epidemiology?
John Snow (1813-1858)
Common source spread is a
single-source for all of the individuals infected