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79 Cards in this Set
- Front
- Back
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Pathogenicity:
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The ability of an organism to cause disease in a host
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Pathogen:
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A species able to cause disease
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Virulence:
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Degree of pathogenicity
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Commensal organism:
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These bacteria live w/in us and on us but do not normally cause disease
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Opportunistic pathogens:
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Bacteria that do not normally cause disease but if innate immune barriers are broken, they will take advantage of the opportunity.
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Primary pathogen:
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Bacteria that are never normally found in or on us and regularly causes disease
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How do pathogens attach to host cells?
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Through an adhesin on the microbe and a receptor on the host
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Describe the two domains on an endotoxin:
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1. A-domain is the active part
2. B-domain is the binding part |
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How do exotoxins kill a cell?
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By forming pores in the cell
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Antibiotic:
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Antimicrobial compound of microbial origin
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Antimicrobial or antimicrobic:
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Anything that can be used to treat an infectious disease
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Bactericidal:
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Something that kills bacteria
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Bacteriostatic:
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Inhibits growth but does not directly kill bacteria
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MIC (minimal inhibitory concentration):
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Lowest dose of something that will inhibit growth
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Spectrum:
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What range of organisms will be affected
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How do good antibiotics work?
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They target things microbes have but we do not
Some block the activity of topoisomerase |
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Mechanisms of antibiotic resistance:
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- Exclusion of the antibiotic
- Alterations of the target - Inactivation of the antimicrobial |
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Stapholococci:
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- Gram-positive cocci
- Non-motile and live best in an aerobic environment - Makes alpha toxin, TSST-1, and staph enterotoxin - Scalded skin syndrome |
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What does the alpha toxin produced by staph do?
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It forms pores in the host cell membrane causing lysis of the cell
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When is TSST-1 produced?
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By bacteria in late-log phase of growth in response to low Mg, aerobic conditions, high CO2, and neutral pH
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Staph. diagnosis:
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- Gram-positive cluster of cocci from a wound with many PMN's present
- Coagulase test |
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Streptococci:
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- Divide in one plane only. As a result, they form chains of cocci
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Beta hemolytic:
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The bacteria that (when on a blood agar plate), lyse the cells and leave a clear zone around the colonies
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Alpha hemolytic:
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The bacteria that (when on a blood agar plate) leave a greenish zone
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Gamma hemolytic:
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The bacteria that (when on a blood agar plate) leave no zone
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S. Pyogenes
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- Also known as group A streptococcus
- Causes strep throat, rheumatic fever, scarlet fever, acute glomerulonephritis, and necrotizing faciitis - Streptococcal pharyngitis (strep throat) -- fever, sore throat, large lymph nodes |
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How does streptococci hurt you?
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- Streptolysin S and streptolysin O -- these toxins form pores in cell membrenae
- Releases superantigens -- ex. scarlet fever |
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Scarlet fever:
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- Caused by streptococci superantigens
- "strawberry tongue" - Begins w/ fever and sore throat, bacteria remain in throat, toxin goings to blood stream - Rash first appears on the neck and chest then spreads over the body |
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Impetigo
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- Contagious skin infection that is caused by streptococci
- Appears as red sores on face, especially around nose and mouth - Clears on its own in 2-3 weeks - Can be treated with antibiotic ointment or oral antibiotics |
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Necrotizing faciitis:
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- Flesh-eating streptococcus
- Infection of deeper layers of skin and subcutaneous tissues - Causes destruction of skin and muscle by releasing toxins |
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Immunity to strep...
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- M protein - your body makes antibodies to a specific M protein
- However, there are 80 antigenic variants of M protein...so, you can get 80 new strep infections |
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Strep mutans:
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- Primary cause of dental cavities
- Metabolizes sugars into acids - Sticky, extracellular polysaccharide is adhered to teeth |
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Group B strep:
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- Found in lower GI tract and vagina
- During child birth, bacteria may colonize the newborn, so pre-emptive antibiotics (penicillin) are given |
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Treatment of Group A strep:
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- Penicillin
- Vaccines are in the development |
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Post streptococcal disease:
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- Acute rheumatic fever -- not common due to antibiotics to treat initial strep infection (this is why you should not tough out a strep infection)
- Acute lomerulonephritis -- infection of skin and throat and leads to kidney damage due to immune complexes becoming lodged in the glomerular basement membrane |
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Diptheria
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- Caused by cornebacterium diphtheriae, a gram positive rod-shaped bacteria
- Now, it's almost nonexistent in US due to efficient vaccination - Commonly infects throat and tonsils - Disease caused is a result of toxin production - Diphtheria toxin (DT) is an A-B toxin |
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DT toxin...
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- Inhibits protein synthesis
- Targets elongation factor 2 (EF-2) - Circulates through body and affects cells distant from throat such as heart cells |
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Effects of DT toxin:
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- Inflammation due to necrosis
- Pseudomembrane composed of fibrin leukocytes and debris is formed - Pseudomembrane can become so large that breathing is difficult - If you survive, after 5-10 days, you cough up the membrane and get better |
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Prevention of DT
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- Immunization
- If someone is infected, they can be treated w/ antitoxin. But once the toxin binds to cells, the antitoxin cannot bind or inactivate the toxin |
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What is a vaccine?
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A suspension of infectious agents of some part of them given for the purpose of establishing resistance to an infectious disease
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Explain immunization:
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- Exposes you to some part of a potential pathogen
- Allows your immune system to generate a memory response so you are able to respond quickly and efficiently if/when you are later exposed |
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Attenuated vaccine:
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- Live, weakened organisms
- Tuberculosis - Influenza nasal spray - Results in long-lasting immunity, but they may also revert to their pathogenic form causing disease (polio vaccine caused paralytic polio in a very small percentage of cases) |
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Inactivated vaccine:
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- Inactivated (killed organisms)
- Rabies, Hep A, Influenza in arm, cholera, polio |
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Purified macromolecules as vaccines:
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- Composed of polysaccharides -- have no protein and therefore do not stimulate T cells
- Low affinity IgM antibodies - Diptheria and tetanus, Hep A |
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DNA vaccines:
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- DNA encoding for a protein antigen is injected into muscle
- DNA is taken up and protein is expressed - Includes humoral and cell-mediated immunity - Prolonged exposure produces good memory responses - Easy to mass produce |
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Edible vaccines:
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- Enterotoxin of E. Coli has been produced in potatoes
- Hope is a multi-subunit vaccine, which could be eaten - This would be cheap and easy to produce |
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Helicobacter pylori
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- Associated with gastric ulcers
- Live in gastric mucus - Produce large amounts of urease (breaks down urea to CO2 and ammonia. The ammonia neutralizes gastric acid. - Considered a carcinogen - 50-66% of the world's population is infected with H. pylori |
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Treatment of helicobacter pylori:
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- Antiboitic therapy
- Previously, treatment was antacids, decrease stress, and avoid spicy foods |
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Clostridium
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- Gram-positive anaerobes
- Rod-shaped - Produce endospores - Growth accompanied by gas production (causes gas gangrene) - Produces several endotoxins |
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Describe the endotoxin produced by clostridium:
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The alpha toxin disrupts cell membranes of human cells, they destroy tissue and generate gas at the same time
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Endospores
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- Dormant form of the bacteria
- Formation is triggered by a lack of nutrients - Enable bacteria to lie dormant for long periods of time - Can survive without nutrients and are resistant to radiation, chemicals, and extreme freezing |
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Treatment of clostridium:
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- Debridement (cutting away necrotic tissue)
- Antibiotics are not enough alone -- don't penetrate blood-starved muscles - Hyperbaric oxygen therapy to inhibit growth of and kill the anaerobic bacteria |
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What are some anaerobic areas in the human body?
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Sebaceous glands, crevices on gums, lumen of GI tract
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Describe clostridial food poisoning:
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- Third most common cause of food-borne illness
- Caused by growth of bacteria in foods -- endospores can survive temps of 100 degrees C - Incubation is 10-12 hours after ingesting - Symptoms: abdominal cramping and diarrhea - You usually get better within 24 hours |
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Clostridium botulism
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- Most toxic compound known to mankind
- Less than 1 microgram can kill an adult - Acts to prevent the release of acetylcholine at the neuromuscular junction - Leads to inhibition of neurotransmission - Results in flacid paralysis - Found in home-canned foods with low acid content |
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Why can babies get botulism much more easily than adults?
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- Because commensal bacteria in the adult gut already covers all surfaces
- The baby's gut still has lots of space for the botulism to take |
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Explain the carcass-maggot cycle of avian botulism:
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- Toxic production takes place in decaying carcasses
- Maggots feed upon carcasses and concentrate the toxin - Toxic maggots are ingested by birds - The birds die and their toxic carcasses are eaten by maggots |
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Treatment of botulism:
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- Antitoxin neutralizes unbound toxin (once toxin in bound, it's irreversible)
- Ventilation because death can come by suffocation due to paralyzed breathing muscles - No current vaccine because an effective vaccine must take 7 serotypes into account |
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Clostridium tetani:
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- Produces neurotoxic exotoxin that causes tetanus
- Opposite of botulism toxin because it causes overactivity in the muscles from the smallest stimulus - Take a few days to several years to develop |
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Tetanus therapy:
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- Neutralize any unbound toxin
- Administer antitoxin - Sedation - Recovery requires regeneration of axon terminals |
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Clostridium difficile:
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- Present in normal flora of many people
- Connected to antibiotic-associated diarrhea (with extensive use of antibiotics, normal flora dies and C. diff overgrows it, causing a pseudomembrane and diarrhea) |
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Mycobacterium Tuberculosis (MTB)
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- 1/3 of world's pop has been infected with M. Tuberculoisis
- New infections occur at rate of 1/second - 2-4% will develop disease w/in 1 year. 33% of HIV patients develop TB w/in 5 months - Bacteria grow very slowly - Disease develops slowly - Do not produce exotoxins or endotoxins - As few as 10 bacteria can cause disease |
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Pathway of TB bacterium:
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- Breathed into lungs where it must avoid being killed by phagocyte
- Then, it is free to multiply in macrophage - Macrophage infected with MTB travels through blood and seed tissues such as spleen, liver, and brain |
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How does the TB bacterium avoid being killed by a phagocyte?
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By interfering with the acidification of the phagosome
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Immune response to TB:
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- Macrophages and dendritic cells release cytokines which attract T cells
- Strong Th1 response to DTH type response - If T cell response is successful, you get better. If not, infection continues and a granuloma is formed |
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When does a granuloma form?
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- When immune system attempts to wall off substances that it perceives as foreign but is unable to eliminate it
- Bacteria within the granuloma live but do not thrive - As granuloma develops, necrosis occurs in the center of the lesion. |
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Immunity to TB:
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- Primarily a result of CD4 T cells
- A function of successful activation of your infected macrophages with IFN |
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Symptoms of TB:
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- Cough (initially dry, progresses with sputum and eventually bloody sputum)
- Fever - Malaise - Fatigue - Sweating - Weight Loss |
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TB Treatment:
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- Antibiotic coctail
- In 1-2 weeks, patient is no longer infectious - All bacteria is killed in 6-9 months - If you stop taking your antibiotics before infection is resolved, you can develop antibiotic-resistant strains - Prevention: BCG vaccine is about 80% effective |
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Enterobacteriaceae:
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- Gram negative rod-shaped bacteria
- O antigen: outer membrane. It's specificity is determined by sugars that form side chains - K antigen: cell surface polysaccharides for capsule) - H angigen: flagella that some motile strains have - Have LPS (endotoxin) |
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Toxins produced by Enterobacteria:
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- Alpha hemolysin - causes leakage of cell and cell death
- Shiga toxin - blocks protein synthesis and kills cell - Labile toxin - secretion of water and electrolytes into bowel lumen (diarrhea) - Stable toxin - similar to labile toxin |
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Diarrhea:
Dysentery: |
Diarrhea: three or more loose or liquid bowel movements per day
Dysentery: severe diarrhea containing mucus and/or blood in the feces |
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Type III secretion systems:
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- Contain a needle-like structure used as sensory probe
- Detect eukaryotic cells and secrete proteins that help bacteria infect them - These proteins are secreted directly from the bacterial cell into the eukaryotic cell |
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Escherichia coli diseases:
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- Sepsis
- UTI - Meningitis - Gastroenteritis - Mastitis |
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E. Coli:
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- Pili plays key role in virulence: they mediate the attachment of bacteria to host cell
- 90% of cases of UTI and kidney infections - Meningitis is similar to group B strep in how it is transferred from mother to baby during birth |
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ETEC
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Enterotoxigenic E. Coli
Travelers diarrhea Rare in breast-fed infants due to IgA antibodies transferred |
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EPEC
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Enterpathogenic E. Coli
Attach to small intestine cells Form pedestal-like lesions |
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EHEC
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Enterohemorrhagic E. Coli
Transmitted through food, animal contact, or direct person to person contact |
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E. Coli Symptoms:
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- Start w/ watery diarrhea 2-4 days after infection
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