Normal Flora Versus Pathogens Flashcards
What are the 3 components of the DISEASE TRIAD?
- Host (interactions with microbes)
- Pathogen (microbial interactions)
- Environment
Name 4 Natural Microbial Habitats
- Soil
- Water
- Air
- Animals and Animal Products
Name 4 Host- Microbe Interactions
- Symbiosis
- Mutualism
- Commensalism
- Parasitism
Symbiosis
- Neutral, antagonistic or synergistic relationship between two dissimilar organisms (Symbiotes, Symbionts) living in close association with each other
Mutualism
- Mutually beneficial relationship between two species
Commensalism
- Relationship between two species in which one is benefitted and the other is not affected, neither negatively or positively
Parasitism
- Relationship between two species in which one benefits (the parasite) from the other (the host)
- Usually involves detriment to the host- NOT ALWAYS
Flora or Microbiota
- Microorganisms present in or characteristic of a special location
- FLORA usually refers to PLANTS
- FAUNA usually refers to ANIMALS
INDIGENOUS (Resident) Microbiota
- Microbial flora typically occupying a particular niche
due to diversity of environmental conditions, organisms tend to segregate
TRANSIENT Flora
-Microbial flora only temporarily occupying a given niche
NICHE
- Place of an organism within its community (ecosystem)
- Unique position occupied by a particular species
- Actual physical space occupied and function performed within an ecosystem
OPPORTUNISTIC
- Microbes which cause little clinical or pathological disturbances to the normal bodily state
- Can become invasive and cause disease when defenses are disturbed/ compromised
RESIDENT Flora
- Bacteria
- Fungi
- Protozoa
- Viruses
- Arthropods
What part of the body has the highest number of resident bacteria?
LARGE INTESTINE
How do RESIDENT FLORA protect their HOSTS?
Prevent the growth of harmful bacteria
Does the body have more cells or bacteria?
BACTERIA !!! (10^14)
versus
cells (10^13)
Locations of the Normal Animal Body that contain Microbial Flora
Skin Respiratory Tract Eye (Conjunctiva) Outer Ear Intestinal Tract** Genitourinary Tract
Sterile Sites in the Host
- Brain
- Blood, Tissues, Organ Systems
- Lower Respiratory Tract (Larynx, Trachea, Bronchioles, Bronchi, Lungs, Alveoli)
- Kidneys, ureters, urinary bladder, posterior urethra
- Uterus, Endometrium, Fallopian Tubes, Cervix, and Endocervix
Resident Flora of SKIN
- Colonize the epidermis
- Mainly Staphylococcus species
Resident Flora of ORAL CAVITY
- Colonize cheeks, gums, teeth
- Aerobic AND anaerobic
- Mainly Streptococcus species
Resident Flora of the STOMACH AND INTESTINE
- Stomach: Helicobacter pylori
- Large Intestine: mostly anaerobic bacteria
- 10- 30% of fecal volume
- E.coli, Lactobacillus
Resident Flora of the UPPER RESPIRATORY TRACT
- Microbes often from skin or oral cavity
- Steptococcus and Staphylococcus
Resident Flora of the GENITAL TRACT
- Vaginal flora influenced by hormones
- Flora changes before and after puberty
- Microbes like Lactobacillus
Resident Flora of the URETHRA
- Microbes often from skin near urethral orifice
- Many opportunistic bacteria
Role of NORMAL FLORA
- Common source of infection (ex: e coli causing UTI)
- Immune stimulation (ex: blood type)
- Keep out invaders
- Role in nutrition and metabolism (ex: E coli synthesize Vit K)
Factors Controlling Growth of Microorganisms
- Nutrient Availability
- Physico/environmental Parameters
- Competition
- Host Immune System
Nutrient Availability
- Accessibility of a necessary resource, substance or compound providing nourishment to maintain life
- (FASTIDIOUS organisms- have complex nutritional or cultural requirements, making isolation and culture more difficult)
Physico/Environmental Parameters
1) Water activity/ osmotic pressure
2) Oxygen: metabolic oxygen requirements
- Obligate or Facultative
- Anerobic or aerobic
- Microaerophilic (in between aerobic and anerobic)
3) pH of environment
4) Temperature
- Psycrophile ( growth at 15 - 20 deg C)
- Mesophile (growth at 20 - 45 deg C)
- Thermophile (growth at 50 - 70 deg C)
Competition
- Silmultaneous demand by 2 or more organisms or species for a necessary, common resource or physical space that is limited or potentially limited supply
- Results in struggle for survival
Host Immune System
- Cells and tissues involved in recognizing and attacking foreign substances in the body
Acquiring Infectious Agents
- Portal of Entry
- Colonization
- Invasion
- Multiplication
Portals of Entry
- Ingestion
- Inhalation
- Direct Penetration (trauma, surgical procedure, needle stick, arthropod bite, sexual transmission, transplacental)
Colonization
- Successful occupation of a new habitat by a species not normally found in this niche
- Damage can be from none to great
- Usually no invasion
How does colonization occur?
- Adherence (attachment): close association of bacterial cells and host cells generally characterized by RECEPTORS on TARGET sites
- ADHESIN: structure or macromolecule located on the surface of a cell or extracellularly that FACILITATES ADHERENCE of a cell to a surface or to another cell
- Site of attachment is often a SPECIFIC RECEPTOR
- Adherence may be NON SPECIFIC
Invasion
- Entry and spread throughout cells and/or tissues of host
- Specific recognition of receptor sites on target cells enhances pathogenic advantage
- INVASIN: structures or macromolecules that facilitate invasion by a pathogenic microorganism
Multiplication
- Ability of a microorganism to reproduce during an infection
What is MULTIPLICATION influenced by?
Underlying disease Immunologic status Antibiotic treatment Nutrient availability
Transmission of Disease
1) Entrance
2) Colonization
3) Penetration
4) Vector
What are entrance, colonization and penetration dependent on?
- Age
- Nutrition
- Immunologic state
- General Health of Host
- Virulence Factors
What is a vector?
- A carrier
- Transfers an infectious disease from one host to another
- Usually an arthropod
What is a CARRIER?
- Symptomless individual who is host to a pathogenic microorganism with the potential to pass the pathogen to others
(usually w/i the same species)
What is a NOSOCOMIAL INFECTION?
- Infection acquired in a hospital setting that was not present in the host prior to admission
- Generally occurs within 72 hours
PATHOGENICITY
- Quality of PRODUCING DISEASE or ability to produce pathologic changes or disease
VIRULENCE
- MEASURE OF PATHOGENICITY
- Measurement of degree of disease producing ability of a microorganism
- Indicated by severity of disease produced
DOSAGE
Number of pathogenic microorganisms entering a host
TRUE PATHOGEN
- Any microorganism capable of causing disease
- An infecting agent
OPPORTUNISTIC PATHOGEN
- A usually harmless
microorganism that becomes pathogenic under favorable
conditions causing an
opportunistic infection
INFECTION
Colonization and/or
invasion and multiplication
of pathogenic microorganisms in a host with or without
manifestation of disease
DISEASE
- Abnormal condition of body function(s) or structure that is considered harmful to the affected individual (host)
- Any deviation from or interruption of normal
structure or function of any part, organ, or body system
CONTAGIOUS
- Capable of being transmitted from one host to another
- Communicable
- Infectious
INFECTIOUS DOSE
Number of pathogenic organisms required to cause disease in a given host
- DOSAGE
EPIDEMIC
-Disease occurring suddenly in numbers clearly
in excess of normal expectancy
ENDEMIC
- Disease present or usually prevalent in a population or geographic area at all times
PANDEMIC
- A widespread epidemic distributed or occuring
widely throughout a region, country, continent, or globally
