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64 Cards in this Set
- Front
- Back
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5 Microbes that cause infectious disease: |
Fungi Bacteria Protozoa Helminthes (worms) Virus |
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Bacteria Drug resistance |
Inactivate the drug Modify the drug target Reduce permeability of the drug Export the drug out (efflux pumps) |
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Antibiotic targeting |
Inhibit cell wall synthesis Disrupt cell membranes Inhibit DNA or RNA Synthesis Inhibit protein synthesis in 70s ribosome |
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India Ink |
Has a negative charge- Forms “halo” around negative organisms Ex. Cryptococcus neoformans found in pigeon droppings |
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Gram Stain |
Gram positive- thick peptidoglycan = purple Gram Negative- thin peptidoglycan= counterstain safranin (pink)
Steps: Fixation— crystal violet— iodine treatment wash— decolorization— Counter stain safranin |
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Lugols iodine |
Finds cysts in parasitic samples Yellow/orange |
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Acid fast stain |
For mycobacterium- surface coated with mycolic acid and arabinoglycan
Carbol Fuschin and phenol Methylene blue counter stain |
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Fluorescent Stain |
Direct - looks for antigen Indirect- looks for antibody |
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Wright’s stain |
Looks for plasmodium and flagellates in blood (CBC) |
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Sterile Body Sites |
Blood CSF Joint fluid Bladder Amniotic Fluid Proximal 2/3 of urethra Bone Internal organs that do not have contact with outside environment Urine |
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Importance of Normal Flora |
Develop immune system Interfere with colonization of pathogenic bacteria Contribute to nutrition and health Synthesize and secret vitamins (b12,k) |
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Staphylococcus epidermidis |
Most abundant on the skin-moist areas Gram positive Facultative Anaerobe Tendency to stick to prosthetic joints and valves |
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Propionibacterium |
Gram positive Settle in oil glands- Acne Breaks down skin lipids into fatty acids |
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Staphylococcus aureus |
Most common in the nose Gram positive, thick peptidoglycan layer, cocci clusters Causes: Conjunctivitis, sty, boils, pneumonia, endocarditis, impetigo, food poisoning, scalded skin syndrome, toxic shock syndrome, UTI, osteomyelitis PUS = staph aureus
Converts H peroxide to H20 and bubbles (catalase positive- like all staphylococcus species) Coagulase positive (to differentiate aureus from other staph species) Mannitol fermentation positive (differentiates from staph epidermidus) |
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Helicobacter pylori |
Most common in stomach Urease protects it from acids Causes: Gastric ulcers and gastric cancers |
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2 major areas for colonization of bacteria |
Terminal Ileum Colon |
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Large intestinal flora |
90% anaerobes Rich in coliform bacteria (gram negative- Ex E. coli (most common to cause UTI) Bacterial imbalance here affects obesity and inflammatory bowel diseases |
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Lactobacilli |
Most common in vagina when estrogen levels high Keeps vaginal pH low - acidic |
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Candida Albicans |
Yeast Infection |
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A baby is born sterile, and is then colonized In what order? |
Skin Throat GI tract Mucous membranes |
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Transmission of Disease occurs how? |
Horizontal transmission- human to human Iatrogenic Fomites Soil Water Animals Vertical transmission- mother to fetus, breast feeding |
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Which bacteria love water? |
Pseudomonas (Otitis externa) -particularly affects immunocompromised patients on respirators and pt with Cystic Fibrosis who have problems clearing mucous Legionella pneumophila aka legionnaires disease- a typical pneumonia |
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Virulence |
Quantitative measure of pathogenicity- measured by # of organisms needed to cause disease/infection LD50 lethal dose (#of organisms needed to kill half the host population) ID50 infectious dose (#of organisms needed to infect half the host population) Infectious dose depends on virulence factors |
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Infection |
Organism enters the body and begins to multiply |
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Disease |
Signs and symptoms appear- cells in body are damaged The bacteria has colonized the area that it likes (salmonella likes bile salts, so it will colonize the gallbladder) |
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Carrier State |
Individual has become colonized with potential pathogen, and can be a source of infection to others, even if asymptomatic |
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Endotoxins |
Lipopolysaccharides In cell walls of gram negative bacteria Not secreted, weakly antigenic so no antitoxins or vaccines Induces overproduction of cytokines- fever, inflammation, septic shock, DIC (disseminated intravascular coagulation- overactive clotting and bleeding in vessels) |
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Exotoxins |
Secreted A and B subunits Used as antitoxins and vaccines |
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Clostridium Difficile |
Most Common Hospitalized Infection Exotoxin A- watery diarrhea Exotoxin B- pseudomembrane In colon Causes: Bloody diarrhea, gastroenteritis, pseudo membrane in the colon |
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Corynebacterium Diphtheriae |
Gram positive aerobe (Chinese letters) Serious infection of nose and throat Causes thick covering in the back of the throat (pseudomembrane), bull’s neck, difficulty breathing, heart failure, paralysis |
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Cholera |
Vibrio cholera exotoxin allows a lot of fluid to pass through the bowels Causes rice water stool, constant diarrhea |
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Tetanus |
Gram positive Exotoxin blocks the release of inhibitory neurotransmitters, producing muscular spasms Spores on rusty nails |
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Invasins |
Bacterial surface proteins and receptors that are necessary for invasion, help bacteria get through the body Ex: Hyaluronidase- breaks down acids Collagenase Streptokinase, coagulase- lysis of fibrin Hemolysins- break blood clots Phospholipases, Lecithinases- lyse cell membranes
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Periods of infectious disease |
Infection— incubation(can be infectious)— prodrome— specific disease— recovery(latent)— good health (latent)
Latent- host may seem better, but the illness can reactivate at a later time (Ex. Mono) |
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Host resistance to bacteria |
Normal flora- protect against invaders Desquamination- shedding skin to rid bacteria Keratin and sebum on skin - low carbon source and antimicrobial effects Mucociliary apparatus Lysozyme- In tears, breaks down peptidoglycan in cell walls Peristalsis- moves pathogens quickly through the body to prevent colonization Acidity in stomach and urine |
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Adhesins/Ligands |
Allow bacteria to bind to surface receptors on certain host cells |
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Quorum sensing |
Bacteria can sense how many other organisms are around them and form a biofilm |
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Proper specimen collection |
Site- normal flora at site Timing- sample right before temperature spike, when the organism is being released into the blood stream Transport- ASAP bc sample can replicate quickly. Store sample in unfavorable conditions to slow growth and replication |
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Enriched agar |
Nutrients that support growth of fastidious microbes |
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Selective agar |
Promotes growth of one type, inhibits growth of the other |
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Differential |
Distinguishes between organisms |
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Blood agar |
General- everything usually plated on blood agar Differential- A hemolytic- partial (pneumoniae) B hemolytic- complete (pyogenes) Y hemolytic- none (enterococcus) Special Cases: Pseudomonas creates a Green sheen and grape odor Proteus mirabilis - nightmare bc it grows over everything |
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Columbia agar plate |
Selective for Gram Positive Useful for differentiating a pathogenic gram positive microbe from the normal gram negative bacteria in stool |
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Chocolate agar |
Enriched Promotes growth of fastidious organisms (Ex. Haemophilus and Neisseria) |
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Thayer Martin agar |
Selective for pathogenic Neisseria gonorrhea |
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Macconkey agar |
Selective for gram negative Differential- Lactose positive - pink Lactose negative- clear
Mucoid appearance = capsule |
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Hektoan agar |
Selective for gram negative Differential- Lactose positive -yellow (coliform bacteria) Lactose negative - clear/bluish green H2S positive - black center (salmonella) |
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Capsule |
Glycoprotein or glycolipid that protects the organism Virulence- negative charge Used as antigens in vaccines |
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Pyogenic response to pathogens |
Pus producing Antibody, complement, neutrophils Pyogenic bacteria are extracellular pathogens |
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Granulomatous response to pathogens |
Macrophages and Th cells Intracellular pathogens that Invade and survive in cells |
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Types of vaginal discharge Observe under wet mount (saline prep) |
Frothy, foamy, fish odor = Trichomonas Cottage cheese = yeast infection Musty odor, runny, voluminous = gardinella |
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KOH prep |
Cuts down background mucus to view cells better |
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Peptidoglycan synonyms |
Murein and mucopeptide |
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Periplasmic space |
Only in gram negative Invasins are stored here = more damaging effects than gram positive bacteria |
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Teichoic acids |
Only in gram positive peptidoglycan walls Similar to LPS endotoxins in gram negative bacteria. Induce fever, hypotension, etc |
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Streptococcus pneumoniae |
Diplococcus in chains, intracellular Gram positive Causes fluid accumulation in the lungs, we hear Rales on auscultation |
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Haemophilus |
Gram negative rods, intracellular Fastidious- needs enriched agar Likes to grow around staph Conjunctivitis |
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Neisseria gonorrhea |
Gram negative diplococci (coffee beans) Fastidious- needs enriched agar Intracellular Signs: perfuse amounts of discharge |
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Campylobacter |
Gram negative spirochete Causes watery diarrhea |
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Catalase |
Staphylococcus convert hydrogen peroxide to water and 02 (catalase positive) Streptococcus does not (catalase negative) |
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Minimum inhibitory concentration |
Smallest amount of agent needed to inhibit growth of an organism |
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Sensitivity test |
Dilution of different amounts and types of antibiotic with organism to see which are most effective in killing
Kirby Bauer(disks) and E Test(strip) |
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Antibiograms |
Chart that displays Antibiotic resistance of patient populations in a certain area |
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Streptococcus pyogenes |
Gram positive Commonly in throat and skin B hemolytic Catalase negative M protein binds factor H and fibri Scarlet fever, pharyngitis, impetigo, acute glomularnephritis(sequelae), acute rheumatic fever. Associated with Tourette’s syndrome and ADD |
