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Sem 3 Mini 3 Micro
Ross University School of Medicine - Semester 3 - Microbiology - Mini 3
| Question | Answer |
|---|---|
| What is the most common baceteria of STDs? | Chlamydia Tracomatis. Second most common is Neisseria gonorrhaeae |
| Compare the presentation/effects of botulin toxin vs a tetanus toxin | Botulin toxin --> flacid paralysis / Tetanus toxin --> spastic paralysis |
| What conditions are associated with Clostridium perfringens infxon? | Gas gangrene (wound infxon, etc) and diarrhea/food poisening (from ingestion)GI infxon is normally self-limitting and will resolve in 12-24 hours |
| Describe the causative agent and features of TRACHOMA | Trachoma is caused by Chlamydia trachomatis (serovars a-c). It is an occular disease most commonly seen in areas of poverty. THE WORLDS LEADING CAUSE OF PREVENTATIVE BLINDNESS. It is caused by the host immune response to the infxon |
| What is the rx for trichoma | Azithromycin, doxycycline or ofloxacin |
| What is the cause of lymphogranuloma venerum? | C. trichomatis infxon (L1 L2 or L3 serotype)commonly spread by anal intercourse or lymphatic spread |
| Wha is the presentation of lymphogranuloma venerum | Marked inflammation and swelling of lymph nodes draining the inguinal region (most commonly) Fever, chills, anorrhexia, HA, proctitus, and myalgia. |
| What are the three major members of the chlamydiae family | C. trachomatis --> STDC. Pneumoniae --> walking pneumoniaC. psittaci --> bird transmitted form |
| What disease is associated with Chlamydiae psitacci | Psittacosis (aka ornithosis) - the bird transmittable form of chlamydia |
| What is psittacosis treated? | Tetracycline or doxycycline (for bird: give bird chlortetracycline for 45 days) |
| What are the names and features of the 2 major toxins produced by C. diff? | Toxin A - fluid production and damage to large bowel. Toxin B - causes rounding of tissue culture cells... working in conjunction with toxin A to cause symptoms |
| What is the tx for pt with tetanus ? | Metronadozole. This is the DOC for anaerobic infxons. Pencillin G would also work but since it also inhibits GABA, it will also aggrevate the symptoms, so metronadazole is used. |
| List the major virulent strains of e.coli | EHEC (shiga toxin producing, O157:H7), EPEC , ETEC (traveler's diarrhea), EAEC (seen freq in AIDS pt), DAEC, EIEC |
| Describe the method by whic each of the major types of Chlamydiae exit the cell following infxon.... | C. Trichomatis and C. pneumoniae exist by reverse endocytosis while C. psittaci exists by lysing the cell. |
| What is the best lab technique for determining if a gene is present and actively expressed? | Reverse transcriptase PCR |
| What is impetigo and what causes it? | Impetigo is a small area that is similar in appearance to erythema that progresses to form a bullae. It is cause by S. aureua. It's chacteristic feature is the formation of a honey colored crust that forms as the lesions heal. |
| What is a bullae | Blister like lesions filled with a cloudy fluid that forms as bullus impetigo progresses. (S. aureus causes this) |
| What are the 4 major infxons of Streptococcus pneumoniae | Meningitis, Otitis media, Pneumonia, Sinusitis (M.O.P.S.) |
| Lecethinase is used by what bacteria? | C. perfringens produces this toxin, it causes gas gangrine. |
| What is the result of exposing chlamydiae-infected cells to INF-gamma | Induces an altered state in the reticular bodies known as PERSISTANCE. |
| What is persistence? What bacteria is this seen in? | Persistence is a state in which the reticular bodies of a chlamydiae-infected cell are morpholgically enlarged and transcriptionally active, but have a slowed metabolic rate. These cells do not form the infectious elementary bodies. |
| What is the purpose of the state of persistence seen in chlamydiae | To avoid immune response and linger in tissues. This is a possible mechanism of chronic disease with chlamydiae |
| What are major serotypes of chlamydiae and the features of each. | A,B, and C: blindness. Commonly seen in africa.D-K: Urethritis/PID/ and reiter disease/ everything else.L1-L3: neonatal via birth canal and lymphogranuloma venerum. |
| What is the causative bacteria and toxin of gas gangrene? | C. perfringens. Lecethinase. |
| What are the major encapsulated pathogens? | Strept. pneumoniae, Klebsiella, Heomopholus influenza, Pseudomonas aeruginosa, Neisseria meningitidus, cryptococcus neoformans |
| What are the key features of Clostridium? | Gram +, anaerobic, spore forming. These are the most clinically important anaerobes and include C. perfringens (gas gangrene), C. tetani, C. botulinum, and C. difficile. |
| What are the key features of mycobacterium? | Obligate aerobes, slow growing, and acid fast (alpha alkyl B hydroxyl fatty acids in cell wall) |
| What is the differential test for species of staph. | Coagulase test. S. aureus = Coag +, S. epidermis = Coag - |
| What is a radiologic finding of strep pneumoniae? | Infiltrate / consolidation in the lungs. |
| What is the most common cause / source of S. aureus infxon. | post-op nosocomial infxon. |
| In what type of bacterial infxon would tx with abx lead to exotoxin release? | EHEC O157:H7 infxon (shiga like toxin)abx is c/i |
| What is a toxoid? | a vaccination against a disease caused by exotoxin production. It is made by treating purified exotoxin with formalin, I, pepsin, etc |
| Compare the origin (site of encoding) of shigella dysenteria toxin (shiga toxin) vs E. coli shiga-life toxin. | Shiga toxin is encoded on the bacterial chromosome, while shiga like toxin is encoded by bacteriophage. |
| What secretion system mediates the secretion of exotoxin through the INNER MEMBRANE of bacteria? | SecYeg secretion system. Additional sytems are used in bacteria that have an outer membrane. |
| What bacteria is associated with Pott's disease? | Mycobacterium tuberculosis. This disease is an osteomyelitis of the vertebrae. |
| What mediates the attachment of Staphylococci to mucoal surfaces and what structure does it actually attach to? | Leipoteichoic acid mediates its attachment to Fibronectin on the mucosal surface. |
| What two bacteria possess the virulence factor IgA protease? | Strep. pnemoniae and N. meningitidus |
| Describe the key feature of N. meningitidus... | encapsulated, gram -, diplococcus. |
| What are the virulence factors of N. meningitidus? | LPS, IgA protease, and polysaccharide capsule (resists phagocytosis) |
| Describe the effects of endotoxin on. 1) Kuppfer cells. 2) Neutrophils. 3) B-lymphs, and 4) compliment. | Kupfer cells: causes the releas of TNF-alpha and IL-1 to mediate fever. Neutrophils: kinin release-> Vasodilation. B-lymphs: Activation to produce antibody. Compliment: inflammation |
| What are the key gram + pyogenic bacteria | Gram + = ****staph aureus***(also epidermis and saprophyticus)Gram - = Neisseria, E.coli, P. aeruginosa, Bacteroides fragillis, and klebsiella pneumoniae. (mnemonic = "never expect professors to behavor kindly" |
| What the the general features of strep pneumoniae. (gram, motility, morphology, virulence factors, catalase test?) | Gram positive/ENCAPSULATED, non-motile, diplococci, a-hemolytic/IgA protease, catalase negative. BILE SOLUBLE! |
| What virulence factor inhibits the phagocytosis of Strep pneumoniae? | its capsule. The capsule also prevents C3b bining (preventing opsonization), activation of alternative pathway, as well as resistance to dessication (drying out) |
| What is optochin used for? | It is used in disc assay as a differential test for Strep. veridens and Strep. pneumoniae. Veridens can grow in the presence of optochin while pneumoniae cannot. |
| What are some abx commonly associated with causing c.diff? | cephalosporin, ampicillin and clindamycin. |
| How is s. pneumoniae diff'd from s. veridens | Opthican test. growth in the presence of opthican = veridans. |
| What is myenecrosis? | Gas gangrene. Cause by C. perfringens / lecithinase toxin |
| How does s. pneumoniae kill cilliated cells? | By the release of pneumolysin (triggered by host autolysin release). Pneumolysin perforates the cell membrane causing the formation of pores. |
| What is pneumolysin? | A cytotoxin who's release is stimulated by host mediated release of autolysin. It perforates the host cell membrane by binding to cholesterol... forming pores and causing lysis. |
| Pneumolysin is found in what bacetria. | S. pneumoniae. |
| What cell wall component facilitates invasion into alveolar cells? What is the mechanism? | Choline. It binds to the platelet activating factor (PAF) receptors and enters the cell via endocytic vacules. This also activates teh compliment pathway to induce IL-1 and TNF-A. |
| What are the two major alpha-hemolytic bacteria? | Strep. veridans and Strep. pneumoniae |
| Tx of EHEC? | Rehydrdation. NO ANTIBIOTICS! |
| Bundle forming pili are a feature of what type of E. coli? | EPEC. This protein causes actin filament condendation |
| How is EHEC differentiated from other types of E. coli? | EHEC cannot ferment sorbitol.... the other types can. |
| What is the mechanism of EHEC | Production of shiga toxin which is injected into the cell while the bacteria remains extra cellular. This is accomplished by attachment via intimin. Adhesion and Effacement leion and RBC b/d with enterohemolysin leads to bloody diarrhea and edema. |
| Renal failure due to binding at glomerular GBS receptor is a feature of what toxin/bacteria combo | Shiga-like toxin in EHEC O157:H7 |
| EHEC vs EPEC with regard to pt presentation/clinical features. | EHEC does not produce a fever, EPEC does. Also, EPEC does not produce a toxin... instead it used bundle forming pili to adhere to cell and cause A/E lesions. |
| What is the only type of invasive E. coli... what symptoms does it's infxon yield? | EIEC. Watery diarrhea with a + fecal WBC test |
| What is a common cause of persistant baceterial diarrhea in AIDS pts and infants. | EAEC (enteraggregative E. coli) |
| Common cause of neonatal meningitis? | E.coli infxon from mother. |
| What media is selective for gram negative bacteria and differential for lactose fermenters? | MCconkey agar. |
| What are the 3 antigens of e.coli? | O-antigen: capsular. K-antigen: fimbriae, H-antigen: flagella (motile bacteria only) |
| What is a ghon complex? | A TB granuloma with lobal/perihilar node involvement. It reflect a primary infxon or exposure to TB |
| What is the most common site in the lungs where reactivation of TB occurs? | In the apices. |
| What is the most common site of primary TB infexion? | Middle lobe of lungs |
| What is the primary cause of tissue damage in TB? | Host immune response |
| What is the biggest consequence of lymphohematogenous dissemination of TB? | Seeding the lung apices. Primary or secondary lung disease can occur. |
| What is the mos important case of reactivation of TB leading to 2ary TB? | HIV coninfxon |
| What is the major complication of a hypersensitivity to TB | Pulmonmary TB/ tissue damage in apical cavities. This is the most common manifestation of adult TB. |
| What 2 cytokines contribute most to TB symptoms? | TNF-alpha and IL-1? |
| What stain is used for mycobacterium? | Fuschin or flurochrome |
| A strong CMI with weak humoral immununity is characteristic of what type of leprosy? | Tuberculoid leprosy |
| Weak CMI with strong humoral immunity is characteristic of what type of leprosy? | Lepromatous leprosy |
| Bone resorption is a feature of _________ leprosy. | Lepromatous. |
| What is the gold standard for dx of TB. | Sputum culture. |
| What is the tx for TB | Isoniazid, rifampin, pyrazinamide, ethambutol. |
| What is the role of antibodies in TB? | None. TB requires a cellular immune respone, which doesn't occur until several weeks following exposure. |
| How do mycobacteria increase their chances of survival once inside of a macrophage. | They inhibit the acidification of the phagolysosome. |
| Disseminated/milliary TB is most common in what individuals? | Immunocompromised. The absence of cell mediated immunity allows for dissemination and manifesation into a systemic disease. Muiltiorgan failure. |
| What hepatitis virus is enveloped? | Hep B |
| What hepatitis virus is naked? | Hep A |
| What is the difference between a positive and a negative virus? | A positive virus can be directly translated into a amino acid, while a negative virus must first be copied to it's codon form |
| What feature is characteristic for all (-)RNA viruses except for retroviruses? | They are all enveoped and carry their own RNA dependent RNA pol. |
| What is the viral cause of hepatocellular carcinoma? | Chronic hepatitis infxon |
| Hep B is counteracted by what immune response type? | Cell mediated. |
| Who are at highest risk for Hep B infxon | alcoholics and neonates. |
| What is a faruncle and what is a carbuncle? | A carbuncle a collection of faruncles. A faruncle is a large pus contrailing lesion in the dermis that exudes perulent material f/ a single opening. Faruncle = boil. |
| Osteomyelitis is commonly caused by what type of bacteria? | S. aureus. |
| What is the function of coagulase? | Formation of a fibrin capsule in S. aureus. |
| Coagulase is a virulence factor of what bacteria | S. aureus |
| What is the most common cause of meningitis? | Strep. pneumoniae |
| What is the function of protein A in staph. aureus. | binds to the H chain of antibody and inhibits Ab mediated opsonization and phagocytosis |
| By what mechanism does S. aureus avoid getting phagocytosed. | By the release of protein A, which prevents opsonization by Ab, and also by coagulase, which form a fibrin capsule around the bacteria. |
| What toxins are produced by S. aureus. | Hemolysin, Leukocidin, entertoxin, exfolliative toxin, TSST-1, and protein A + Coagulase |
| Exfolliative toxin is a virulence factor of what bacteria? | S. aureus. |
| TSS is caused by what bacteria? | S. Aureus (via TSS toxin) |
| Diffeentiate the CSF findings if a funal mengingitis vs a bacterial meningitis? | Fungal = Increase in lymphocytes, bacterial = increase in PMNs |
| Asplencic individuals are most likely at risk for what type of infxon? | Encapsulated bacterial infxon. (ie; S. pneumoniae in an older sickle cell patient) |
| What virulence factor mediates the formation of a fibrin capsule around the infectious loci of s. aureus? | Coagulase |
| Describe the structure of exotoxin and the key role of each component? | A domain: delivered into host cell. Posseses enzymatic activity to induce the toxin. B domain: binds hos cell membrane to deliver the A domain. |
| How are exotoxins activated? | By cleaving the disulphide bond between the A and B domain. |
| How do exotoxins enter the host cell? | The A domain is transported across the membrane by the B domain. |
| Botulinum toxin and tetanus toxin are both what kind of toxins? | Zinc proteases / neurotoxins |
| Hemiagglutination inhibition involed IgG or IgM? | IgG - late phase infxon / 2ry immune response |
| What type of microscopy requires staining? What kind does not ? | Bright field microscopy requires staining. Phase contrast does not. |
| What kind of microscopy is used for parasites? | Phase contrast |
| Where is a francisella tularensis infxon commonly aquired? | Working in a lab setting. This bacteria can penetrated intact skin (no wound required) because of its small size. |
| Early phase antibody response is mediated by: | IgM |
| Late phase antibody response is mediated by: | IgG |
| Hemiagglutination inhibition test with a positive result means? | A positive result means that antiboduy against the antigen in question is present and patient has been exposed to the agent (hemoagglutination is inhibited). |
| In the presence of O2, a methlyene blue strip is what color? | Blue |
| Describe the basic flow of lab diagnosis? | 1)Microscopy is performed on specimen. 2) the sample is cultured 3) cultivated organisms are analyzed and ID'd / tested for susceptability |
| In order for a microbial susceptabiity test o be | |
| What stain is used for mycobacterium? | Fuschin or flurochrome |
| A strong CMI with weak humoral immununity is characteristic of what type of leprosy? | Tuberculoid leprosy |
| Weak CMI with strong humoral immunity is characteristic of what type of leprosy? | Lepromatous leprosy |
| Bone resorption is a feature of _________ leprosy. | Lepromatous. |
| What is the gold standard for dx of TB. | Sputum culture. |
| What is the tx for TB | Isoniazid, rifampin, pyrazinamide, ethambutol. |
| What is the role of antibodies in TB? | None. TB requires a cellular immune respone, which doesn't occur until several weeks following exposure. |
| How do mycobacteria increase their chances of survival once inside of a macrophage. | They inhibit the acidification of the phagolysosome. |
| Disseminated/milliary TB is most common in what individuals? | Immunocompromised. The absence of cell mediated immunity allows for dissemination and manifesation into a systemic disease. Muiltiorgan failure. |
| What hepatitis virus is enveloped? | Hep B |
| What hepatitis virus is naked? | Hep A |
| What is the difference between a positive and a negative virus? | A positive virus can be directly translated into a amino acid, while a negative virus must first be copied to it's codon form |
| What feature is characteristic for all (-)RNA viruses except for retroviruses? | They are all enveoped and carry their own RNA dependent RNA pol. |
| What is the viral cause of hepatocellular carcinoma? | Chronic hepatitis infxon |
| Hep B is counteracted by what immune response type? | Cell mediated. |
| Who are at highest risk for Hep B infxon | alcoholics and neonates. |
| What is a faruncle and what is a carbuncle? | A carbuncle a collection of faruncles. A faruncle is a large pus contrailing lesion in the dermis that exudes perulent material f/ a single opening. Faruncle = boil. |
| Osteomyelitis is commonly caused by what type of bacteria? | S. aureus. |
| What is the function of coagulase? | Formation of a fibrin capsule in S. aureus. |
| Coagulase is a virulence factor of what bacteria | S. aureus |
| What is the most common cause of meningitis? | Strep. pneumoniae |
| What is the function of protein A in staph. aureus. | binds to the H chain of antibody and inhibits Ab mediated opsonization and phagocytosis |
| By what mechanism does S. aureus avoid getting phagocytosed. | By the release of protein A, which prevents opsonization by Ab, and also by coagulase, which form a fibrin capsule around the bacteria. |
| What toxins are produced by S. aureus. | Hemolysin, Leukocidin, entertoxin, exfolliative toxin, TSST-1, and protein A + Coagulase |
| Exfolliative toxin is a virulence factor of what bacteria? | S. aureus. |
| TSS is caused by what bacteria? | S. Aureus (via TSS toxin) |
| Diffeentiate the CSF findings if a funal mengingitis vs a bacterial meningitis? | Fungal = Increase in lymphocytes, bacterial = increase in PMNs |
| Asplencic individuals are most likely at risk for what type of infxon? | Encapsulated bacterial infxon. (ie; S. pneumoniae in an older sickle cell patient) |
| What virulence factor mediates the formation of a fibrin capsule around the infectious loci of s. aureus? | Coagulase |
| Describe the structure of exotoxin and the key role of each component? | A domain: delivered into host cell. Posseses enzymatic activity to induce the toxin. B domain: binds hos cell membrane to deliver the A domain. |
| How are exotoxins activated? | By cleaving the disulphide bond between the A and B domain. |
| How do exotoxins enter the host cell? | The A domain is transported across the membrane by the B domain. |
| Botulinum toxin and tetanus toxin are both what kind of toxins? | Zinc proteases / neurotoxins |
| Hemiagglutination inhibition involed IgG or IgM? | IgG - late phase infxon / 2ry immune response |
| What type of microscopy requires staining? What kind does not ? | Bright field microscopy requires staining. Phase contrast does not. |
| What kind of microscopy is used for parasites? | Phase contrast |
| Where is a francisella tularensis infxon commonly aquired? | Working in a lab setting. This bacteria can penetrated intact skin (no wound required) because of its small size. |
| Early phase antibody response is mediated by: | IgM |
| Late phase antibody response is mediated by: | IgG |
| Hemiagglutination inhibition test with a positive result means? | A positive result means that antiboduy against the antigen in question is present and patient has been exposed to the agent (hemoagglutination is inhibited). |
| In the presence of O2, a methlyene blue strip is what color? | Blue |
| Describe the basic flow of lab diagnosis? | 1)Microscopy is performed on specimen. 2) the sample is cultured 3) cultivated organisms are analyzed and ID'd / tested for susceptability |
| In order for a microbial susceptabiity test to be run, what MUST be true. | The organism in question must be know to be th causative agent of the condition. |
| During endotoxin induced innate immune system activation, what is the cell type and effector that is responsible for fever? | Cytokine C5a from mononuc. phagocytes lead to TNF-a and IL-1 release |
| How does endotoxin act as an immunological adjuvent? | By causing B-cell proliferation via the induction if IL-1 release |
| How does endotoxin induce B-cell proliferation. | Via its induction of IL-1 |
| What two bacteria release endotoxin by "blebbing" | N. Meningitidus and N. gonorrhea |
| What acts as a notification to the immune system that a gram negative bacteria is present? | Endotoxin. |
| Lipooligsaccharide (LOS) is a feature what bacteria? | Endotoxin found in membrane of N. meningitidus. |
| What bacteria has LOS as a virulence factor? | N. meningitidus! |
| Productive cough with rust colored sputum may be indicative of what bacteria? | Strep. pneumoniae (typical pneumonia) |
| Most bacterial cause of pneumonia? | Strep pnemoniae. Most commoly by direct extension (ie otitis media-->pneumoniae) |
| What are the virulence factors of S. aureus. | Capsule, coagulase, protein A, leukocidin (kills leukocytes) |
| Coagulase negative staph infxon is associated with what risk factors? | indwelling medical devices |
| What bacteria is very common in pastries, cream, etc? | S. aureus |
| Lipoteichoic acid is associated with gram ___ bacteria | gram + |
| what is the most important virulence factor of S. pneumoniae | Its polysaccharide capsule which prevents opsonization by C3b and inhibits activation of alternative pathway. |
| How do endotoxins differ from exotoxins? | Endotoxins are normal components of the cell membrane of the bacterium while exotoxins are secreted or attached to cell exterior. Endotoxins are only made in Gram neg bacteria. |
| Why is there no immnune response to the endotoxins of the natural flora of our GI tract? | Because we do not possess the toll-like receptors (TLRs) to response to those endotoxins. Diseases such as Chron's and IBS involve the recruitment of extra-GI macrophages, which are sensitive to these toxins. |
| What is the gram + equivalent to endotoxin? | Lipoteichoic acid. |
| Following the injection of endotoxin, what is the order of cytokines release? | TNF-a----> IL-1 (IL-6 slowly rises and is released at same time as IL-1) |
| What is the most toxic portion of LPS | Lipid A |
| What is LPS | Lipopolysaccharide - Endotoxin |
Created by:
rkirchoff
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