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Gram Stain Procedure
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Step 1 - Crystal violet
Step 2 - Gram iodine
Step 3 - Decolorizer (Alcohol or Acetone)
Step 4 - Safranin red
Gram positive will be purple and gram negative will be pink/red.
Step 2 - Gram iodine
Step 3 - Decolorizer (Alcohol or Acetone)
Step 4 - Safranin red
Gram positive will be purple and gram negative will be pink/red.
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Cell walls of gram-positive bacteria contain?
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A thick peptidoglycan layer and lipoteichoic acid.
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Cell walls of gram-negative bacteria contain?
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A thin peptidoglycan layer and an outer membrane containing LPS and proteins for transport/cell wall synthesis.
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Mycobacterial Cell Wall Features
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Very thick cell wall that is hydrophobic, waxy, and rich in mycolic acids. It does contain a peptidoglycan layer.
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The capsule is 99% _______.
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Water
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Chemotaxis
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Movement of a motile cell or organism in a direction corresponding to a gradient of increasing or decreasing concentration of a substance.
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Vesicles
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Secretory vehicles for proteins and lipids of both gram negative and gram positive bacteria.
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What is the S layer?
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It is a layer made up of one or more S layer proteins (SLP) present in both gram negative and gram positive bacteria. It helps to resist phagocytosis/serum killing, maintain integrity, form biofilms, and uptake iron.
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Nucleoid
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The location of DNA. (No membrane)
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Endospore
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A highly resistant structure found in Bacillus and Clostridium. (Gram positive only) Used for persistence and not reproduction.
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Inclusion body
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Stored nutrients for later use.
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Sialic acid mimicry
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The surface of human cells are coated by sialic acid so that immune cells can distinguish self cells. Some bacteria like N. meningitidis cover their outer surface with sialic acid residues to hide.
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Transformation
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DNA is taken up as "naked DNA"
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Conjugation
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DNA is transferred from one bacterium to another when cells are in contact. AKA bacterial mating.
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Transduction
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Bacterial DNA is transferred by a bacterial virus.
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Frederic Griffith's Experiment
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Rough and smooth colonies of Streptococcus pneumoniae were utilized on rats to prove that DNA is the genetic material. Heat killed strains had the live strain added before being introduced to rats.
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Generalized Transduction
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Defective phage particles incorporate random fragments of the host cell's chromosome with low efficiency. After replication the host cell with undergo the lytic cycle and die.
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Specialized Transduction
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Temperate phages excise incorrectly and takes adjacent host genes along with it with high efficiency. The cell will undergo the lytic cycle.
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Biosafety levels
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Biosafety levels 1-4 are the least dangerous at 1 and the most dangerous at 4.
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Why is molecular diagnosis useful?
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It is fast, accurate, and specific. Old methods of growing in defined media takes days, are limited, and 99% of organisms are non-cultivable. Old methods are much less expensive and require less skill.
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Koch's Postulates
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The microorganism or other pathogen must be present in all cases of the disease
The pathogen can be isolated from the diseased host and grown in pure culture
The pathogen from the pure culture must cause the disease when inoculated into a healthy, susceptible laboratory animal
The pathogen must be reisolated from the new host and shown to be the same as the originally inoculated pathogen
The pathogen can be isolated from the diseased host and grown in pure culture
The pathogen from the pure culture must cause the disease when inoculated into a healthy, susceptible laboratory animal
The pathogen must be reisolated from the new host and shown to be the same as the originally inoculated pathogen
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Koch's Molecular Postulates
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The gene should be found only in the virulent strain
Should be isolated by cloning
Disruption of the gene should reduce virulence
Should be isolated by cloning
Disruption of the gene should reduce virulence
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Disinfection
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The destruction or removal of vegetative pathogens but not bacterial endospores. Used on inanimate objects.
Ex/Bleach, iodine, and boiling.
Ex/Bleach, iodine, and boiling.
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Sterilization
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The complete removal or destruction of all viable microorganisms. Used only on inanimate objects.
Ex/Autoclave and sterilants.
Ex/Autoclave and sterilants.
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Antisepsis/Degermation
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Chemicals applied to body surfaces to destroy or inhibit vegetative pathogens.
Ex/Alcohol and surgical hand scrubs.
Ex/Alcohol and surgical hand scrubs.
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Decontamination/Sanitization
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The mechanical removal of most microbes.
Ex/Soap, detergents, and dish washers.
Ex/Soap, detergents, and dish washers.
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Kirby-Bauer Test
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Determining the efficacy of antibiotics using a zone of inhibition approach.
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Isoniazid inhibits?
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Mycolic acid synthesis. (Mycobacterial cell wall inhibitor)
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Polymyxins disrupt?
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The outer membrane. Last resort drug in some severe Gram negative infections as it is very toxic.
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Cell Membrane inhibitor
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Amphoteracin B binds to the fungal membrane component and causes leakage. Has toxicity problems but can be used to treat thrush and other systemic fungal infections.
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DNA gyrase Function
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Reduces strain on DNA while unwound.
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DNA gyrase inhibitor
answer
Fluoroquinolones (Ex/Ciprofloxacin)
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RNA synthesis inhibitors
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Rifampin and rifadin.
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DNA fragmentation inhibitor
answer
Metronidazole
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DNA cross-linking inhibitor
answer
Mitomycin C
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Rifampin is used to treat:
answer
Tuberculosis (TB) and meningitis.
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Metronidazole is used to treat:
answer
Anaerobes, H. pylori, and Giardia lamblia.
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Transcription inhibitors
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Rifampin and actinomycin.
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Translation inhibitors
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Aminoglycosides, tetracycline, erythromycin, spectinomycin, and chloramphenicol.
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Protein assembly inhibitor
answer
Griseofulvin.
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Folic acid biosynthesis inhibitors
answer
Trimethoprim and bactrim.
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Quorum signal inhibitor
answer
Azithromycin, hamamelitannin, and brominated furanones.
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Biofilm resistance mechanisms
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Antibiotic may fail to penetrate beyond the surface layers of the biofilm.
Some of the bacteria may differentiate into a protected phenotypic state.
In zones of nutrient depletion or waste accumulation the antibiotic may be inhibited.
Some of the bacteria may differentiate into a protected phenotypic state.
In zones of nutrient depletion or waste accumulation the antibiotic may be inhibited.
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Quorum Signaling in Gram negative
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AHL is used with homologs of Luxl and LuxR. AI-2 is considered to be a universal signal molecule.
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Quorum Signaling in Gram positive
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Gram positive signals are small peptides.
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Advantage of Biofilm Dispersion
answer
Planktonic organisms are more susceptible to drugs.
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Disadvantage of Biofilm Dispersion
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Release of biofilm clumps.
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Innate defense components
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Non-specific.
Neutrophils, dendritic cells, natural killer cells, and mactrophages.
Neutrophils, dendritic cells, natural killer cells, and mactrophages.
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Adaptive defense components
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Specific.
Antibodies and T-cells.
Antibodies and T-cells.
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Natural barriers
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Skin, mucus, ciliated epithelium, gastric acid, and normal microflora.
question
First line of Defense
answer
Physical and chemical barriers that keep microbes from penetrating sterile body compartments. (Innate/nonspecific)
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Second line of Defense
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Cellular and chemical systems that immediately activate if infections agents make it past the surface defenses. (Ex/Fever) (Innate/nonspecific)
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Third line of Defense
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Specific host defenses that must be developed uniquely for each microbe through specialized white blood cells. (Acquired/specific)
question
The skin is an ______ environment.
answer
Acidic
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Opsonization
answer
The coating of foreign pathogens with opsonins to enhance phagocytosis.
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LPS triggers ______ release.
answer
Cytokine
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Septic Shock results in _____ and _____.
answer
Hypotension/Decreased Blood Pressure
Hemorrhages
Leads to organ failure.
Hemorrhages
Leads to organ failure.
question
Immunogen
answer
A substance capable of inducing an immune response
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Antigen
answer
a toxin or other foreign substance that induces an immune response in the body, especially the production of antibodies.
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Superantigen
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An antigen that yields an exaggerated response.
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Epitope
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Small, accessible portion of an antigen that can be recognized.
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Haptens
answer
Antigens too small to provoke immune response but can attach to carrier molecules to provoke a response.
question
Adjuvants
answer
Chemical additives added to vaccines to improve effectiveness.
question
Titer
answer
Number of infectious units per volume of fluid.
question
Lymphocyte differentiation
answer
B and T cells arise from the same stem cell type. B cells are generated in the bone marrow, however, while T cells are generated in the thymus.
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Dendritic cell
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Antigen-presenting cell. Shows T and B cells what to attack.
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T-cell
answer
A lymphocyte that identifies pathogens and distinguishes one pathogen from another.
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B-Cell
answer
A lymphocyte that produces proteins that help destroy pathogens.
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Full immune response development takes ____ years from birth.
answer
1-2
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Four types of Acquired immunity
answer
Natural
- Active (After Infection)
- Passive (Mother to Infant)
Artificial
- Active (Vaccination)
- Passive (Immunotherapy)
- Active (After Infection)
- Passive (Mother to Infant)
Artificial
- Active (Vaccination)
- Passive (Immunotherapy)
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Toxoid
answer
Inactivated toxin used in a vaccine.
question
Conjugate Vaccine
answer
Antigens like polysaccharide attached with a protein antigen to elicit long term immune response.
question
subunit vaccines
answer
...
question
Normal Flora of the Skin and Hair
answer
S. aureus, S. epidermidis, Micrococcus, P. acnes, diptheroids, and yeasts.
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Normal Flora of the Conjunctivae (Eyes)
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S. epidermidis and diptheroids.
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Normal Flora of the Mouth
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A large variety of organisms.
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Normal Flora of the Stomach and Small Intestine
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Lactobacillus, Streptococcus, Enterococcus, yeasts, Veillonella, Enterobacteriaceae.
question
Normal Flora of the Circulatory System
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Sterile save brief periods of transient bacteremia.
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Normal Flora of the Nervous System
answer
Sterile.
question
Microbial succession begins at _____.
answer
Birth
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Microbial Forensics use bacterial communities of the _______ to identify individuals.
answer
Skin
question
Gastric Ulcer cause
answer
H. pylori
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Gastric Cancer cause
answer
H. pylori
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Cerebral palsy cause
answer
Placental infection.
question
Rheumatoid arthritis cause
answer
Intestinal anaerobic bacteria and B. burgdorferi (Lyme disease)
question
What gut microbe stops peanut allergies?
answer
Clostridia
question
LD50
answer
The lethal dose (of a toxin) for 50% of the test population.
question
ID50
answer
Infectious dose for 50% of the test population.
question
Nosocomial Infection
answer
Hospital acquired infection.
question
Endogenous Infection
answer
Normal microbiota becoming an opportunistic pathogen.
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Iatrogenic Infection
answer
Doctor induced infection by surgery or antibiotic therapy.
question
Fomite
answer
An object or substance capable of carrying infectious organisms. (Ex/Hair)
question
Subclinical Infection
answer
Individuals who show no symptoms or only mild symptoms.
question
Incidence
answer
Number of new cases of a disease in an area during a period of time.
question
Prevalence
answer
Number of total cases of a disease in an area during a period of time.
question
Staphylococcus Laboratory Characteristics
answer
Gram Positive, catalase positive, non-motile.
Cocci arranged in clusters.
Cocci arranged in clusters.
question
What test is used to differentiate between S. aureus and other Staphylococcus species.
answer
Coagulase Test.
S. aureus is coagulase positive while other species are negative.
S. aureus is coagulase positive while other species are negative.
question
Staphylococcus Characteristics
answer
Normal flora of the skin and upper respiratory tract.
Opportunistic infection.
Opportunistic infection.
question
Staphylococcus Symptoms
answer
Abscesses and pus.
question
Staphylococcus aureus Virulence
answer
MSCRAMMS - Binds to connective tissue.
Capsule - Adhesion and biofilm formation
Coagulase - Clots blood
Protein A - Binds Fc portion of antibodies
Hyaluronidase - Penetration into connective tissue
Fibrinolysin - Dissolve fibrin clots
Capsule - Adhesion and biofilm formation
Coagulase - Clots blood
Protein A - Binds Fc portion of antibodies
Hyaluronidase - Penetration into connective tissue
Fibrinolysin - Dissolve fibrin clots
question
What is the second leading cause of UTIs behind uropathogenic E. coli?
answer
Staphylococcus saprophyticus
question
Staphylococcus Diagnosis
answer
Microscopy and a culture of S/D media supplemented with sheep blood.
question
Staphylococcus Treatment
answer
Drainage of abscesses followed by antibiotics such as Vancomycin.
question
Streptococcus Laboratory Characteristics
answer
Gram positive, catalase and coagulase negative, non-motile, cocci shaped chains.
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