Microbe Human Interaction Flashcards
how much more microbial cells in/on bodies than in human cells in body?
3x
human body conditions favorable for microbes
source of nutrients, environment, moisture, stable pH, temperature, different surfaces
how can microflora change?
vary with age, diet, health, hygiene practices, hormones, drug therapy
resident microflora
microbes which are present and permanent in some areas of the body (eg. skin and large intestine)
transient microbes
microflora that can only remain for a short period of time
transient v resident microflora
transient must compete in order to stay on/in but resident microflora are better adapted
how do resident microflora compete?
they compete with space nutrients and release toxins to kill transient microbes
infection
microorganism invades the host and bypasses the host defense mechanisms
how does an infection occur?
first initial contact and then microorganisms invade our tissues and grow in it
disease
overall organismal health is suffering a cost
amniotic sac
fetal membranes
microbe introduction during natural birth
lactobacilli streptococci and staphylococci when passing through birth canal
what does breast milk contain
oligosaccharides
what digests oligosaccharides?
bifidobacterium invantis
what does bifidobacterium invantis ensure?
baby’s digestive tract is seeded by healthy microbes and does not acquire pathogenic microbes
why does microflora change in mouth when getting teeth?
there is additional surface area in the mouth for different microbial growth and new consumption of foods
microbe introduction through c section
breast milk and human-skin interactions
what organ bacteria is the most unique?
skin bacteria
microbes on skin
staphylococcus corny bacterium. propionibacterium, yeast
where does normal flora reside on skin?
dead cell layers on surafce to dermal layer in follicles/glands
microbes common in sebaceous glands
mycobacterium, staphyococcus
digestive tract is considered
a tube within a tube which separate it from the the body cavity; Microbes residing within the digestive tract are therefore technically outside the body’s internal environment
Peristalsis
wave-like muscle contractions which pushes microbes downward, preventing colonization in the esophagus
Exceptions of microbial growth in the stomach
Lactobacilli and Helicobacter pylori
lactobacilli
ferments lactose, producing lactic acid
Helicobacter pylori
can cause ulcers under stress
The acidity of the stomach
is analogous to a highly concentrated cleaning solution that kills most bacteria.
what limits microbial growth in the small intestine?
Enzymes and digestive molecules, along with peristalsis
most common genus in oral cavity/mouth
streptococcus
What kind of microbes contribute to cavities?
Anaerobic microbes through acid production from fermentation
are mouthwashes generally ineffective against the diverse microbial population of the mouth?
yes
what does dry mouth cause?
increases microbial growth and halitosis
highest concentration of microbes in the body
anaerobic bacteria
what bacterias aid in aid digestion, produce vitamins and contribute to intestinal odor
Bacteroides, Bifidobacterium, Fusobacterium, Clostridium
vitamins produced by microbes Bacteroides, Bifidobacterium, Fusobacterium, Clostridium
B12, K, riboflavin, thiamine
intestinal odor
flatulence
The large intestine’s microbial community is essential for
nutrient absorption and overall gut health
Upper Respiratory Tract
Colonized by resident microflora: oral streptococci, Staphylococcus aureus (nose), and Neisseria species (mucous membranes)
Lower Respiratory Tract (Lungs)
Mucus and cilia trap and remove inhaled microbes; microbe free in healthy individuals
why is lower respiratory tract’s environment is unfavorable for microbial growth?
efficient clearance mechanisms
internal Reproductive Organs include
uterus, fallopian tubes, ovaries
Internal Reproductive Organs are
Generally sterile. The closed cervix prevents microbial ascent from the vagina.
Vagina microbe environment
Low diversity, low microbial count, but resident microbes
what do resident microbes do in vagina
maintain an acidic pH, inhibiting pathogenic growth
microbes in vagina
lactobacilli
Estrogen stimulates
glycogen production: fueling Lactobacilli growth and acid production.
menopausal
and prepubescent vaginal infections
lower estrogen levels, have a more neutral vaginal pH, increasing susceptibility to infections
External Genitourinary Organs microbes
Colonized by streptococci, staphylococci, corynebacteria, and some coliforms
Virulence
A measure of how severe a disease it causes
True Pathogens
Cause disease in healthy individuals with normal immune systems
Eg of true pathogens
influenza, malaria, bubonic plague
Opportunistic Pathogens
Cause disease when the host’s immune system is compromised
Eg of opportunistic pathogens
Pseudomonas, Candida albicans
stages of infection
- entry 2. adhesion 3. invasion 4. multiplication 5. exit/egress
entry
microbe enters the body
adhesion
microbe attaches to host tissues
invasion
The microbe spreads to other tissues
Multiplication
The microbe grows and reproduces
Egress (Exit)
The microbe leaves the host, enabling transmission to new hosts.
Portals of entry
endogenous, exogenous
Types of portals of entry
skin, GI tract, respiratory tract, urogenital tract, placenta
BSL
biosafety level
BSL-1
Low risk; microbes not known to cause disease in humans
BSL-2
Moderate risk; not easily contagious (HIV)
BSL-3
High risk; contagious, often via respiratory transmission, and potentially fatal (yellow fever)
BSL-4
Highest risk; highly contagious, highly virulent, and extremely dangerous (ebola)
what does BSL determine?
safety measures required when handling microbes in a laboratory setting
what portals of entry can Staphylococcus aureus enter through?
skin, respiratory tract, or GI tract
Infectious Dose
The minimum number of microbes required to cause an infection. A smaller ID indicates higher virulence.
adhesion of microbes
pili, flagella, fimbriae, glycocalyx, viral spikes
Virulence factors
molecules produced by microbes that enhance their ability to cause disease
Virulence factors include
Exoenzymes, Toxins, Anti-phagocytic Factors
Exoenzymes
Extracellular enzymes that break down host tissues
Eg exoenzymes
muconase, keratinase
Toxins
Poisons that damage host cells
Types of toxins
Exotoxins, endotoxins
Exotoxins
Secreted by microbes; often A-B toxins
eg. exotoxin
botulinum toxin
Endotoxins
Part of the microbial cell; released upon cell lysis
eg. endotoxins
lipopolysaccharide in Gram-negative bacteria
Anti-phagocytic Factors
Prevent destruction by white blood cells
Direct killing of phagocytes
Some pathogens produce toxins, like leukocidins, that directly kill white blood cells.
Capsule formation
A polysaccharide capsule surrounding the bacterial cell hinders phagocyte binding and engulfment.
what does the capsule formation act as?
physical barrier, preventing the phagocyte from making contact with the bacterial cell surface.
Intracellular survival and multiplication
Certain pathogens can survive and even replicate within phagocytes, effect
stages of infections/diseases
- incubation period 2. prodromal stage 3. invasion period 4. convalescent period
incubation period
time between initial exposure to the pathogen and the appearance of the first symptoms; symptom free
Eg. of incubation periods
common cold: 24-72 hours; plague: a few hours; leprosy: years
prodromal stage
The onset of initial, often non-specific symptoms
Eg. prodromal stage
Feeling tired, experiencing headaches or muscle aches are common prodromal symptoms for many infections.
invasion period
This is the period when symptoms are most severe and specific to the infection; pathogen multiplies rapidly, becoming well-established in the body
invasion period effected by
host health and pathogen virulence
convalescent period
The recovery phase, where the body returns to normal health.
Transmission of the pathogen is most likely during what period
invasion period due to high pathogen loads
type of infections
localized, systemic, focal, mixed, primary, secondary, acute, chronic
localized infection
pathogen remains confined to a specific area of the body
eg. localized infection
Boils, athlete’s foot, and warts
systemic infection
pathogen spreads throughout the body, affecting multiple tissues and organs.
eg. systemic infection
Influenza
focal infection
infection begins in a localized area but then spreads to other parts of the body, either through dissemination of the pathogen or release of toxins.
mixed infection
two or more microbes to cause infection
eg. mixed infection
dental carriers (anaerobic and aerobic) microbes)
primary infection
weakens the host defenses
primary/secondary infection
two infections occur one after the other
eg. primary/secondary infection
UTI to vaginal yeast infection
acute infection
rapid short lived infection
chronic infection
long lasting and (more commonly) less severe
signs
objective evidence
eg. signs
fever, redness, swelling
symptoms
Subjective evidence of disease reported by the patient
eg. symptoms
headaches, fatigue
signs of blood infection
Leukocytosis, Leukopenia, Septicemia, Bacteremia/Viremia
Leukocytosis
increased white cell count
Leukopenia
decreased white cell count
Septicemia
high numbers of microbes in the blood
Bacteremia/Viremia
low number of bacteria/viruses in the blood
portals of exit
Respiratory Tract, skin, digestive tract, urinary tract, blood feeding insects, persistence in the host
eg. bloodfeeding insects
malaria from mosquitos
portal of exit vs method of transmission
portal of exit: location
method of transmission: how it gets to host
reservoirs
where pathogens persist
living reservoirs
human carriers
human carriers
people who are carrying the microbe
active
infected with microbe and the microbe is growing inside them
passive
not infected with the microbe but have on the surface
Asymptomatic
infected with the microbe and transmitting, but not showing
incubation carriers
HIV
convalescent carriers
diphtheria
chronic carriers
typhoid
Vectors
animals that transmit microbes from person to person
Biological vector
involved in the life cycle
eg. biological vector
Fleas, tics, kissing bugs
mechanical vector
on the surface on their body
eg. mechanical vector
flies, cockroaches
zoonotic infections
Diseases transmitted from animals to humans (rabies)
Non-living Reservoirs
Environmental sources like soil and water
Communicable
Transmitted from one host to another.
Contagious
Highly communicable.
modes of transmission
direct and indirect
direct tranmission
person to person
indirect transmission (vechiles)
Requires an intermediate source; surfaces, animal to people, surface droplets
Nosocomical infections/HAIs (hospital acquired infections)
Infections acquired in a healthcare setting
causes of HAI
surgery/lowered defences, infection from surfaces, passive carriers/hospital workers
Epidemiology
study of tracing the patterns of disease
CDC
Centers for Disease Control and Prevention
where is the CDC located?
atlanta, georgia
WHO
World Health Orginization
where is WHO located
Geneva, Switzerland
reportable
required by law
notifiable
recommended to report
epidiemology statistics
prevalence, incidence, mortality, case fatality rate
prevalence
total number of existing cases in respect to population
incidence
number of new cases (time frame)
mortality
chance to die from a given disease
Case fatality rate
chances of dying from disease once infected
endemic
disease that has known predictable infection in population (seasonal flu)
epidemic
above expected levels in localized area
sporadic
random occurrence (rabies, bubonic plague)
pandemic
epidemic that has gotten to 2+ continents
Koch’s postulates for determining disease
- find the microbe 2. isolate and cultivate 3. inoculate and observe 4. re-isolate
problems with koch’s posulates
detect microbe that only infects humans, viable but nonculturable, mixed infections
