Please enable JavaScript.
Coggle requires JavaScript to display documents.
Introduction to Microbiology (Lectures #33 and #34) and (#45 and #46),…
Introduction to Microbiology (Lectures #33 and #34) and (#45 and #46)
Types of Pathogens
Bacteria
Structure (not all bacteria have all of these structures)
Capsule
4 Functions
Attachment (to host, surfaces, or other bacteria)
Avoid activating Complement system
Form biofilms (especially on implants)
Resists phagocytosis (by macro/neutrophils)
Cell Wall
Found in all bacteria except
Myocoplasma
Mycoplasma
are stained via
acid-fast
staining
Ziehl-Neelsen stain
Drives
carbofuschin
into impermeable cell, requires lots of heat, dye, and experience so no longer used in clinical labs
Auramine-Rhodamine stain
Faster, requires less time and experience (more reproducible), lower magnification, but need a fluorescent scope
MUST
confirm stain with culture, but cultures take 18 hours for one division and patients cannot wait that long
Protects bacterium from
osmotic pressure
Useful for
gram stain
identification
Stains the
peptidoglycan layer
of the cell wall
Positive = Purple
Thick
(up to 30 layers) peptidoglycan layer holds on to Crystal Violet stain and prevents it from being washed out and counterstained with Safarin
Negative = Pink
Thin
(single layer) peptidoglycan layer does not hold Crystal violet, thus it is washed out and the wall is counter-stained with Safarin
:red_flag: Sequence: Crystal violet, Gram's iodine, ethanol (to decolorize), safarin (counterstain)
:red_cross:Some bacteria cannot be gram stained well
mycobacteria
(+)
mycoplasma
(no cell wall)
Treponema
(-)
Legionella (-), Rickettsia (-), Chlamydia (-), Bartonella (-), Ehrlichia (-), Anaplasma (-)
Are called gram +/- based on thickness of cell wall on EM
Differentiates +/-, morphology, and pattern
NAG-NAM glycan chains connected by tetrapeptide chains and peptide interbridge (in + cells) or covalent bonds (- cells)
Fimbriae (pili)
Used for attachment
To host
To other bacteria (sex/conjugation pili)
Conjugation
Donor cells connects to recipient cell via conjugation pilus, extrachromosomal
plasmid
is transferred to recipient from donor (one strand transferred, recipient then synthesized complementary strand to have a complete copy)
Transformation
Common in
Neisseria, S. Pneumoniae, H. Influenzae
Donor cell takes up "naked" donor DNA (perhaps from a dead bacterium), and thru recombination incorporates it into its chromosomal DNA
1 more item...
Transduction
Bacteriophage infects host cell, incorporates some of the host DNA into its viral DNA, phage infects a new cell and DNA from cell 1 is given to second cell to create a recombinant cell
Flagella
Used for motility
Spore (endospores - made in cell)
Used for longevity when essential nutrients are missing (essentially a
dormant stage
)
Viable (technically still alive)
Metabolically dormant (avoid antibiotic activity)
Highly resistant (killed by autoclave or long boil)
Spore wall/cortex/exosporium prevents degredation by
chemicals
Small acid soluble proteins (SASPs) prevent permanent
UV damage
Binds to DNA and changes it to "A" conformation
In this form, all radiation damage makes "spore photoproduct" thymine dimers
1 more item...
Dipicolinic acid (DPA) prevents degredation by
dry conditions
Can be terminal (at end of cell) or internal (in middle of cell)
Common in
Bacillis
(aerobic)
anthracis
causes Anthrax disease
Cutaneous, GI, or inhalation
cereus
causes food poisoning
Common in
Clostridia
(STRICT anaerobes)
botulinum
causes flaccid paralysis
From improper canninng, honey in infants, block Acetylcholine
at CNS
tetani
causes tetanic paralysis
blocks acetylcholine
at NMJ
perfringens
causes gas gangrene
difficile
causes C-Diff (deadly diarrhea)
Normal in gut flora,
overuse of antibiotics
causes overgrowth
Lipopolysaccharide (LPS/Endotoxin)
Found only in
gram negative
bacteria
Associated with causing
septic shock
3 parts
: Lipid A, oligosaccharide core, and O-specific antigen
Lipid A
activates up to 1% of total body lymphocyte population
Causes catastrophic immune response
TLR4 (macrophage) activation
Complement activation
Tissue factor activation (leads to coagulation and DIC)
Diseases caused by bacteria (some examples)
Pneumonia
Most common - Streptococcus pneumoniae (+ dipplococci)
Klebsiella pneumoniae (- rod)
Legionella pneumophila (- rod)
Chlamydophila pneumoniae (- obligate intraceullular cocci)
Haemophilus influenzae (- rod)
Mycoplasma pneumoniae (Acid-fast rods)
Typhoid Fever
Caused by
Salmonella Typhi
(- rod)
Fecal-oral transmission
GI discomfort followed by systemic symptoms (fever, malaise, rash)
Then travels to gallbladder and establishes a
carrier state
Endemic
in underdeveloped Africa and Asia
UTIs and STIs
Gonnorhea (
Neisseria gonorrhoeae
) (- diplococci)
Syphilis (
Treponema Pallidum)
(cannot gram stain - spirochetes)
Urethritis and PID (
Chlamydia
species) (- obligate intracellular cocci)
IMPORTANT TO NOTE
: Obligate intracellular pathogens (will not grow outside a host cell or on cell-less culture)
Chlamydia/Chlamydophila
Pelvic Inflammatory Disease
Psittacosis (pneumonia from parrots)
Rickettsia
Rocky Mountain Spotted Fever
Replicate by
binary fission
- creating 2 identical clones
Growth requirements
Oxygen
Strict aerobes (ex-
bacillus
)
Facultative aerobes (ex -
E. Coli
)
Microaerophiles (ex -
H. Pylori or Neisseria
)
Aerotolerant anaerobes (fermenters)
Strict anaerobes (ex -
clostridia
)
To be aerobic need catalase (to digest H2O2) and Superoxide dysmutase (to digest superoxidase)
pH
Extreme acidophiles, acidophiles, neutrohiles, alkalophiles, extreme alkalophiles
Temperature
Directly related to enzyme activity
Bacteria that affect humans are
mesophiles
(~15-45 degrees celcius)
Viruses
Can only be seen on electron microscope
Consists of DNA or RNA and protein, but no organelles
Fungi
"Plantlike" Yeasts and Molds
Candida Albicans
- oral thrush/vaginitis
Histoplasma capsulatum
- histoplasmosis (lung infection from bird feces) - dimorphic
Cryptococcus Neoformans
(Meningitis and pneumonia from bird feces)
Commonly identified with
India Ink Stain
Some fungi are
dimorphic
and can be either yeasts or molds depending on temperature
Parasites
Helminths
Enterobiasis vermicularis
(Pinworms)
Trichinella spiralis
(Trichinosis)
Taenia solium
(Pork tapeworm)
Ascaris lumbercoides
(Ascariasis)
Schistosomiasis (caused by several species of schistosomes) - oval shaped with lateral spine
Protozoans
Toxoplasma gondii
(Toxoplasmosis)
Cryptosporidium parvum
(Cryptosporidiosis)
Plasmodia
species (Malaria)
Entamoeba histolytica
(Amebiasis)
Vector-transmitted infections
Lyme disease – deer tick (small)
Rocky Mountain spotted fever – dog tick (big)
Malaria – mosquito
West Nile infection - mosquito
The plague – flea
Leishmaniasis – sand fly
Chagas disease – reduviid bug
Epidemiology
Communicable diseases
Spread person-to-person, animal-to-person, or vector-to-person
Examples: STDs, Influenza, Common Cold, West Nile, Malaria, RMSF
Non-communicable diseases
Caused by patients' normal flora, organisms common in nature, or ingestion of toxins
Examples: Botulism or Staph food poisoning, peritonitis or endocarditis from normal flora
Not passed person-to-animal or person-to-person
Terms
Endemic:
A disease is present at a low but fairly constant level in a population
Infection
: The multiplication of an organism within a host
Disease
: A clinically apparent response of the host to infection (with typical or atypical disease manifestations)
Subclinical infection
: Inapparent infection (asymptomatic)
Carrier State
: Infectious agent establishes itself as
part of the normal flora
or causes low-grade chronic disease after an acute infection
Example: Typhoid Mary was a
carrier
for years, periodically secreting bacteria in fecal matter and transmitting it to others
Reservoirs:
mammalian
carrier of disease (humans or animals)
Zoonoses
: diseases that occur primarily in animals and can be passed to people
Epidemic:
Level of infection above that usually found in a population
Pandemic:
Widespread disease in a region, or worldwide with a high attack rate
Infectivity:
frequency at which an infection is transmitted from an infected individual to a susceptible individual (how many people in the room with an infected person are subsequently infected)
Pathogenicity:
The number of persons who develop disease/the total number of people infected
Virulence:
the number of fatal or sever cases/total number of cases
Incidence:
the number of new cases within a specified period, OR the number of new cases/by the size of the population under surveillance
Prevalence:
the total number of cases existing in a given population at risk at a given point in time or during a defined period
Epi/Pandemic Examples
"Black Plague" -
yersinia pestis
gram (-) bacillus, rat to flea to human, possible bioterrorism agent
Measles: caused by Measles virus, one of the most highly communicable viruses, vaccinated against in MMR (vaccination rates declining, only 95% effective), infection confers life-long immunity
Influenza: orthomyxovirus, segmented RNA virus, has Neuraminidase and Hemagglutinin surface factors (killed massive number of people in 1918)
Lyme disease:
Borrelia burgdorferi
spirochete bacteria, transmitted by ticks
AIDS: caused by Human Immunodeficiency Virus (HIV), a retrovirus, replicates in and destroys T-cells, treatable with antiretroviral regimen, untreated patients susceptible to secondary infections and death
MERS: Middle East Respiratory Syndrome, caused by a coronavirus, led to epidemic in 2014