Medical Microbiology: Bacteriology I

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Macroscopic (classification)
colony morphology, color, smell
Microscopic (classification)
shapes, Gram +, Gram -, Endospores, capsule, flagellum, staining
Phenotypic (classification)
aerobic vs anaerobic, biochemical characteristics, selective growth conditions (temperate, growth media)
Antigenic (classification)
Direct detection, indirect detection, immunofluorescence, enzyme-linked immunosorbent assay (ELISA), Wester Blot
Molecular (classification)
polymerase chain reaction (PCR)
Gram +
thick layer of peptidoglycan
Gram -
thin layer of peptidoglycan, outermembrane
only gram +, vegetative state, needs signaling to get out
direct detection
use conjugated anti-target antibody
indirect detection
use conjugated secondary antibody
microscopic detection of antigens
enzyme-linked immunosorbent assay (ELISA)
detect pathogen--> active infection Capture --> detect presence of particular antigen antibody detection --> start with antigen to detect antibody quick test
Western Blot
each band represents a different viral protein often used to confirm ELISA results if you have known antibodies --> use to detect virus look at immune responses
Polymerase chain reaction (PCR)
amplify particular sequence of DNA mimicking primer and DNA replication can use for detection, sequencing (mutations), and RFLP analysis
If sequence is present in PCR...
If sequence is NOT present...
no amplification
Restriction fragment length polymorphisms (RFLP)
enzymes come from bacteria and recognize and cut DNA sequences to get particular patterns DNA only (can be PCR product DNA) DNA digestion with restriction enzymes producing DNA patterns
Transformations (mechanism)
[Acquisition of foreign DNA] donor cells --> cell lysis --> DNA enters the recipient cell and integrates into DNA
Transductions (mechanism)
[Acquisition of foreign DNA] transducing phage containing donor genomic DNA --> cell lysis --> phage infects recipient cell; donor integrates into recipient DNA
Transpositions (mechanism)
[Acquisition of foreign DNA] moving and relocating in genome uses transposon with inverted repeats
Conjugation (mechanism)
[Acquisition of foreign DNA] free plasmid moves from donor to recipient cell via sex (F) pilus integrated plasmid (episome) promotes transfer of genomic DNA, which integrates into recipient DNA
produced outside cell; slippery so things can't bind or penetrate no opsonization, no MAC, no phagocytosis
grow into giant, multicellular structure that surrounds pathogen
inert object is protected from the immune system and antibiotics until signaled almost impossible to get rid of
destroy host proteins
variable surface proteins
antigenic variation
bind to receptors (proteins, sugars) on the surface of target cell
part of the pathogen structure Ex: LPS on Gram -
product produced and released by the pathogen Ex: A-B
trigger over release of cytokines by CD4+ T cells
large quantity of toxin taken in; immediate effects
accumulation of toxin in infected individual; slower effects
Bacteriostatic agent
prevent growth (put in stasis) Ex: fridge/freezer
Bactericidal agents
destroy bacteria Ex: cleaning wipes, bleach, detergents
Step 1 of Koch's Postulate
Bacteria must be present in every case of the disease
Step 2 of Koch's Postulate
Bacteria must be isolated from host with disease and grown in pure culture
Step 3 of Koch's Postulate
specific disease must be reproduced when a pure culture of the bacteria is inoculated into a health susceptible host
Step 4 of Koch's Postulate
bacteria must be recoverable from the experimentally infected host
disruption of cell wall; inhibition of protein synthesis; inhibition of nucleic acid synthesis; antimetabolite
CD8+ T cells
Capsules cannot protect bacteria from which of the following? -CD8+ T cells -Opsonization via antibodies -Opsonization via complement proteins -Destruction via the membrane attack complex
Which of the following would not be an example of a bacterial static process? -Freezing -Refrigeration -Detergents -Using antibiotics that prevent the synthesis of new cell walls
All of the other answers can be used to protect a bacterial pathogen from
Which of the following are mechanisms by which bacteria can protect themselves from immune responses? -Biofilm formation -Spore formation -Encapsulation -All of the other answers can be used to protect a bacterial pathogen from immune responses.
Which of the following is not a mechanisms that allows bacteria to take in foreign DNA? -Transduction -Conjugation -Operons -Transformation
All of the other answers can be used to help identify a bacterial pathogen.
Which of the following observations can be used to help identify a bacterial pathogen? -Antigenic -Phenotypic -Molecular -Microscopic -All of the other answers can be used to help identify a bacterial pathogen.
Antibodies can be used to help identify a bacterial pathogen in which methods? -PCR -ELISA -RFLP analysis -All of the other answers use antibodies to help identify a bacterial pathogen.
The use of DNA as the genetic material**??
Which of the following is not different between human and bacterial cells? -The composition of the ribosomes -The average size of a cell -The use of a cell wall -The use of DNA as the genetic material
All of the other answers can be used to help identify a bacterial pathogen.
Which of the following can be used to help identify a bacterial pathogen? -All of the other answers can be used to help identify a bacterial pathogen. -Selective growth -Enzymatic activity -Aerobic vs anaerobic growth
normal flora and environment
Where is Staphylococcus found?
Staphylococcus: Transmission
person to person; fomite
Often observed with Staphylococcus
disruption of normal flora (makes spaces for new things to grow) insertion of foreign bodies half-life: days to weeks
Staphylococcus: Immune Avoidance
capsule, biofilm, slime layer, Protein A
Staphylococcus: Virulence Factor
adhesions (slime layer)
Staphylococcus: Toxins
cytotoxins endotoxins superantigens
Staphylococcus: Treatment
Antibiotics --> resistance
Methicillin-resistant Staphylococcus aureus (MRSA)
What is an example of an antibiotic-resistant form of Staphylococcus?
Staphylococcus: Control
ubiquitous clean/sterilize medical equipment minimize exposure
Streptococcus A (S. pyogenes)
strep throat, cellulitis, scarlet fever, necrotizing fasciitis
Strep A: Transmission
person to person, fomite
Strep A: immune avoidance
capsule M proteins: Block C3b binding C5a peptidase (S. pyogenes): block inflammation
Strep A: M&F proteins
adhesion cell invasion (disruption of tight junctions)
Strep A: exotoxins
enterotoxins (A-B toxins) Superantigens [Ex: streptolysin (lyse RBS) --> hemolytic]
Strep A: Treatment
Streptococcus B (S. agalactiae)
neonatal infections, normal flora getting in the wrong place
Strep B: Transmission
normal flora of vaginal tract (birth) location is the issue
Strep B: Pathogenesis
In newborns: bacteremia (bacteria in blood) pneumonia meningitis (in brain)
Strep B: Treatment
antibiotics test women for it
Strep B: Control
minimize exposure and treatment
S. pneumonia (pneumonia)
causes infection in the lungs diplococci Control: vaccine against capsule
normal flora of GI tract
Where is Enterococcus found?
Enterococcus: Transmission
person to person, fomite
disruption of normal flora
Enterococcus is often observed...
Enterococcus: Virulence factors
wide range of growth: aerobic and anaerobic, high salt, broad pH biofilm antibiotic resistance
Enterococcus: Treatment
antibiotics --> resistance
Bacillus: Epidemiology
spore forming stable in environment aerosol transmission (anthracis)
Anthracis (anthrax): Transmission
ingestion (livestock) cutaneous- most common (skin) inhalation
Anthracis (anthrax): immune avoidance
Anthracis (anthrax): toxins
Exotoxin: plasmid encoding 3 genes
edema toxin
PA + LF = ?
lethal toxin
LF + EF = ?
Anthracis (anthrax): Treatment
antibiotics --> resistance vaccination --> toxoid (animals)
bigger problem --> seen in humans a lot
Cereus: Transmission
ingestion (food born pathogen)
Cereus: Virulence Factors
Cereus: heat stable form
emeric (vomiting)
Cereus: heat liable
Bacillus cereus
food poisoning
Cereus: Treatment
Pepto-Bismol for symptoms antibiotics --> resistance
Cereus: Prevention
minimize exposure: cook/store food properly
Emeric Form: Disease onset
~2 hours
Emeric Form: Disease Duration
8-10 hours
Diarrheal Form: Disease onset
~9 hours
Diarrheal Form: Disease duration
20-36 hours
Listeria: Epidemiology
grows @ 4 C, high salt concentration, and wide pH range facultative intracellular pathogen (can exist outside of cell) lives inside macrophage --> pt of immune response doesn't work
Listeria: Transmission
contaminated food/dairy
Listeria: Virulence factors
cell invasion escapes lysosome
Listeria: Disease
can cause spontaneous abortions diarrhea meningitis (rare)
Listeria: Treatment
self-limiting antibiotics --> resistance (for severe cases)
Listeria: Prevention
minimize exposure: cook food properly; avoid raw dairy (soft cheeses and milk), raw vegetables, undercooked meat, etc.
Corynebacterium diphtheriae
a species of bacterium that causes *diphtheria*
Diphtheria: Epidemiology
normal flora facultative anaerobes
Diphtheria: Exotoxin (virulence factor)
result of transduction regulated expression "A" blocks eukaryotic translation --> no protein synthesis
Diphtheria: Treatment
antibiotics passive immunization against exotoxin
Diphtheria: Prevention
vaccination: Diphtheria toxoid --> DPT vaccine
Gram + rod Genus: difficile, perfinges, tetani, botulinum Environmental: soil, water, sewage, normal flora Spore forming --> stability Exotoxins --> neuro toxins obligate anaerobes
obligate anaerobes
only live in the absence of oxygen
Clostridium difficile: Transmission
Growing: normal flora (spread with antibiotic usage) Spores: hospital acquisition
Clostridium perfinges: Transmission
Growing: contaminated food (meat) [growth at 4-60 C] Spores: cutaneous
Clostridium tetani: Transmission
Spores: cutaneous
Clostridium botulinum: Transmission
Spores: contaminated food (canned food, infant formula, dairy)
Clostridium: Which has A-B exotoxin
perfinges, tetani, and botulinum
Clostridium: Which has neurotoxin
Clostridium tetani: Virulence factors
interferes with the ability to communicate with muscles
Clostridium botulinum: Virulence factors
interfere with receptors
botox only has toxin and cannot reproduce
Botulinum vs botox
Clostridium difficile: Disease
Mild: diarrhea Severe: Colitis
Clostridium perfinges: Disease
Mild: cellulitis Severe: Myonecrosis (necrosis of muscle)
Clostridium tetani: Disease
Mild: tetanus (muscle spasms) {localized} Severe: tetanus (muscle spasms) {systemic or neonatal}
Clostridium botulinum: Disease
Severe: botulism {paralysis and respiratory arrest}
Clostridium difficile: Treatment
antibiotics fecal transplant
Clostridium perfinges: Treatment
antibiotics debridement
Clostridium tetani: Treatment
antibiotics debridement passive immunization (toxin)
Clostridium botulinum: Treatment
antibiotics passive immunization (toxin)
Clostridium difficile: Prevention
proper antibiotic usage hygiene
Clostridium perfinges: Prevention
Cooking of food
Clostridium tetani: Prevention
toxoid: DTaP
Clostridium botulinum: Prevention
proper canning food preparation (heat)
rods weakly gram + --> Gram Neutral Acid fast lipid rich cell wall
Acid Fast
test that you can run to see if it has outer membrane structure
lipid rich cell wall
slow growth resistant to many disinfectants (don't have structures) resistant to some antibiotics
Tuberculosis: Epidemiology
~1/3 of the world population is infected restricted to human
Tuberculosis: virulence factors
intracellular pathogen
Intracellular Pathogen (tuberculosis)
prevents fusion to lysosome resistant to nitric oxide-mediated killing immune-mediated control but not clearance (chronic infection) Granuloma
little prison cells; how it is contained and sealed up, but not destroyed formed in lungs
Tuberculosis: Disease
respiratory infection: blood in sputum
Those people don't have the ability to form granulomas
Why is the respiratory infection of tuberculosis systemic in immunocompromised people?
Tuberculosis: Treatment
controlled in most healthy individuals antibiotics --> very complex because of slow growth and multiple drug resistance
Tuberculosis: Transmission
Tuberculosis: Prevention
screening: TB test Vaccination (BCG live attenuated)
Tuberculosis vaccination...
is not in the U.S. or with HIV positive individuals
Immunocompromised Populations
Transplant recipients Age Immunosuppressant infractions (i.e. AIDS) or genetics Immunotherapies
Transplant recipients
immunosuppressants block organ rejection
Age: very young
developing immune system
Age: old
declining immune system
not a global decline, compromised specific parts of the immune system