gram – – Chemistry – Flashcards
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| what does the gram - cell well consist of? what is in the outer membrane? |
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| a cytoplasmic membrane, followed by a periplasmic space with a thin layer of peptidoglycan, followed by an outer membrane with LPS in it. |
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| what is the general structure of LPS? which portion is responsible for toxic shock? is there much variation in LPS among the bacteria that express it? |
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| there is a lipid A moiety, (part responsible for toxic shock), followed by an O region, followed by an antigenic portion that is out in the extracellular environment. clinically the lipid A is the same in all gram - bacteria, though the O antigen portion is made up of different sugars and undergoes antigenic variation |
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| what do gram - cocci express if they do not have LPS? |
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| lipooligosaccharide, (LOS) |
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| does LPS undergo phase variations? |
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| no, because it is an integral part of the cell wall |
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| what is septic shock? what are its symptoms? what is the most important pathology related to lipid A? |
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| if a pt has a systemic infection of gram - bacteria w/LPS, it will stimulate TNF and IL-1, causing HTN, fever, shock, and intravascular coagulation, (DIC). HTN is the most clinically important pathology, causing a decreased blood flow, decreased O2, and tissue degradation. |
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| what is the difference between aerobes and facultative anerobes? |
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| aerobes need O2, while facultative anaerobes can ferment in the presence of O2 and can respire in the presences of O2, (some can undergo anerobic respiration). |
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| what are enterobacteriacae? where are they found? what are associated clinical diseases? |
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| a family of gram - rod shaped bacteria that can be found in the environment, skin, gut, etc. they can cause sepsis, UTIs, GI infections, and pulmonary infections. they include both primary and oppotunistic pathogens. |
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| what is the definition of a primary pathogen? |
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| organisms that cause exogenous infections, (not from within), can cause disease in healthy people |
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| what defines opportunistic pathogens? |
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| bacteria that require an opportunity such as immunosuppression/weakness to infect, (elderly, post sx etc) |
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| what are general properties of enterobacteriaceae? what do they use for energy? are they mobile? what might they contaminate? |
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| all ferment glucose, all facultative organisms, they are oxidase negative, (separates them from pseudomonas aeruginas), some have flagella, some ferment lactose, many contaminate soil+water(fecal/oral route), look similar under a microscope |
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| what is the main thing that separates enterobacteriaceae from pseudomonas aeruginas? |
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| these organisms look similar, but enterobacteriaceae are oxidase negative, meaning they lack cytochrome C oxidase |
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| what causes 95% of community/60% hospital UTIs? |
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| e. coli/Escherichia |
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| what have strains of escherichia aquired if they are causing diarrhea? |
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| plasmids, transposons or phages |
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| are escherichia that cause UTIs part of normal flora? are escherichia that cause GI problems part of the normal flora? |
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| escherichia that cause UTIs are a part of normal flora, while escherichia that cause GI problems are not |
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| what is another name for escherichia? |
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| e. coli |
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| what can group B strep and esherichia both cause? |
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| neonatal meningitis |
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| what do shigella cause? where is this common? |
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| dysentery, (bloody diarrhea),common w/young children in daycares or abroad. |
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| what does salmonella cause? are there related bacteria? |
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| gastroenteritis/typhoid fever. citrobacteria & edwardsiela cause similar problems, but only in immunocompromised individuals. |
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| what enterobacteriaceae cause necrotizing pneumonia? what population is this often seen in, what is the sputum that comes out called? can this organism cause other infections? is it associated with any other enterobacteriaceae? |
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| klebsiella causes necrotizing pneumonia, often seen in alcoholics and the sputum is called currant jelly. klebsiella can also cause UTIs and is associated with enterobacter and serratia |
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| what does proteus cause? is it associated with any other bacteria? |
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| UTIs. proteus can also be associated with morganella and providencia |
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| what dose yersinia cause? |
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| yersinia can cause the plague and enterocolitis in zoonotic infection |
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| what are all the enterobacteriaceae we need to know and major associated diseases? |
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| escherichia - UTIs, shigella - dystentery, salmonella - gastroenteritis/typhoid fever, klebsiella - necrotizing pneumonia/UTT, proteus - UTI and yersinia - plague/enterocolitis |
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| how are the enterobacteriacaea differentiated from each other serologically? |
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| O,H,K antigens. O are side chains on LPS, H are flagellar antigens, and K are capsular antigens |
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| how are enterobacteriaceae differentiated biochemically? |
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| by the substrates or metabolites they secrete. whether or not they can ferment lactose is an important factor |
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| what enteric bacteria are lactose fermenters? |
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| escherichia, enterobacter, and klebsiella, (EEK!) |
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| what enteric bacteria are non-lactose fermenters? |
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| salmonella, shigella, proteus, (PSS!) |
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| what enteric bacteria are slow lactose fermenters? |
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| serratia |
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| what does it mean to use selective screening? |
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| you select for the growth of one organism while depressing the growth of another organism |
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| what does it mean to do a differential screening? |
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| this allows you to differentiate between one organism and another based on metabolic capability, (lactose fermentation) |
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| is macconkey agar selective or differential? |
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| macconkey agar is both a selective and differential screening. it is selective in that it has bile salts that don't allow the growth of gram +. it is differential in that lactose fermenters appear pink and non-lactose fermenters appear colorless |
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| is the EMB test selective or differential? |
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| both. the bacteriostatic dyes will inhibity gram +. escheria are dyed green-black w/a metallic sheen, klebisiella are pink/purple, and non lactose fermenters are colorless. |
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| what is the triple sugar iron, (TSI slant), agar for? |
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| it is a screening test for gram - enteric organisms that ferment glucose, lactose or sucrose and iron sulfide, (black) appears if gas or H2S is formed |
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| what are some characteristics of escherichia coli? what does it ferment? can it cause UTIs? what is a virulence factor it has? what is problem it can cause in young children? |
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| it is a lactose fermenter, indole positive and motile. nonpathogenic strains are normal flora in the colon, which are a common cause of UTIs. its PILLI are an important virulence factor that allows this organism to bind in the gut, against peristalsis. K1 strains are associated wtih neonatal meningitis, (K is for the capsule) |
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| what do ETEC and EHEC have in common, how are they different? |
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| this is an example of horizontal gene transfer. ETEC, (enterotoxigenic e. coli) have a toxin that causes travelers diarrhea, (no blood). EHEC (enterohemorrhagic e coli) cause bloody diarrhea, (aquired this property from shigella via phage/plasmid). |
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| what is the common form of shigella in the US? does this kind create inflammatory diarrhea? does it ferment lactose? does it cause inflammatory diarrhea? are they motile? what kind is found abroad? |
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| shigella sonnei & flexneri are the most common kinds found in the US (transmitted in daycares), they produces non-inflammatory diarrhea as well as being non-lactose fermenters, and non motile. S. dysenteriae and boydii are found abroad and can cause bloody diarrhea. |
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| how does shigella protect itself from macrophages? |
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| shigella invades and destroys cells, and hides from macrophages in this fashion. |
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| what are the 3 most common causes of gastroenteritis in the US? |
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| shigella, salmonella, and campylobacter |
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| where is salmonella found? does it ferment lactose? what are its antigens called? |
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| salmonella can be found in human and animal reservoirs, it is a non-lactose fermenter and motile. its capsuar antigens are called Vi, (for virulence instead of K antigens) |
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| what diseases can salmonella cause? are there local and systemic diseases? is it flagellated? |
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| enterocolitis, (localized inflammatory diarrhea caused by S. typhimurium/enteridis), and typhoid/enteric fever which is a systemic disease caused by S. typhi and paratyphi -> a disease only in humans, which can be carried in the gall bladder, (blood->liver->gall bladder->back to gut). it is flagellated |
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| what does klebsiella pnuemoniae cause? |
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| caused pneumonia, particularly in immunocompromised alcholics. it makes copious capsules, seen as a slime in gram stains |
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| what does proteus mirabilis cause? is it motile? |
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| UTIs. it makes urease which breaks up urea, creating stones. it is highly motile, allowing it to "SWARM" |
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| what is yersinia? |
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| zoonotic disease, uncommon in the US. Y. enterocolitica causes gastroenteritis similar to shigella/salmonella. Y. pestis was responsible for the bubonic plague. |
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| what is a problem with enterobacter cloacae? |
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| high antibiotic resistance |
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| what is providencia rettgeri associated with? |
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| providencia rettgeri is associated with patients in long term healthcare facilities |
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| what are non-enteric gram - rods? what do they have in common? are they normally in the gut? |
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| vibrio, campylobacter, helicobacter, are all onligate pathogens that cause GI tract disease. they are all primary pathogens, (not normal flora) |
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| how do vibrinaceae appear? what kind of disease to they cause? what toxin do they have? what other bacteria make toxin like these organisms? what do they have that makes them virulent? what version of this organism caused death during katrina? |
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| they are curved rods, they cause a really watery diarrhea, cholera toxin similar to LT toxin created by cholera, (rice-water stool). their pili gives them virulence. V. parahaemolyticus caused death in a few katrina victims |
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| what does campylobacteriaceae cause? what is its shape? what food is it associated with? |
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| campylobacteriaceae commonly cause gastroenteritis, they appear as curved rods or S shaped, they have darting motility, and are oxidase +. they are associated with undercooked chicken and unpasteurized milk. |
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| what is a certain kind of campylobacteria that is associated with gastric ulcers, peptic ulcers, and stomach cancer? |
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| helicobacter pylori colonizes the gastric mucosa and produces urease which allows it to live in the stomach, (ammonia produced by urease neutralizes the acidic pH of the stomach) |
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| what shape are fastidious small gram - rods? what are some examples? |
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| these coccbaccili shaped organisms have complex nutritional requirement, and are often involved in respiratory dissease. haemophilius used to be involved in meningitis, bordetella causes whooping cough, and legionella is responsible for legionaires disease |
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| what are pseudomonas aeruginosa? why are they very important clinically? what pts is this seen in often? how do people from this usually die? are they antibiotic resistant? |
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| pseudomonas aeruginosa are OXIDASE POSITIVE, which is a good way to separate them from other organisms. it is the quinessential opportunistic pathogen, (not seen in healthy people, but can infect any body part if immunocompromised). infection of pseudomonas aeruginosa are seen often in CF pts. pts that die from this usually are infected by this, and then staph comes in and they die. there is a problem with antibiotic resistance with pseudomona aeruginosa. |
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| what is important about burkholderia? |
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| they are very resistant to antibiotics and will usually kill their host |
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| who do stenotrophomonas infect? |
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| lungs of CF pts |
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| what does acinetobacter look like? |
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| neisseria, it is an opportunistic pathogen that is seen in harrisons and cause UTIs -> can lead to sepsis |
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| where are a lot of anerobes found? |
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| in the gut |
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| what are the two important neisseria? what shape do they take? do they have oxidase? |
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| N. gonorrhoeae and N. meningitis. they are kidney shaped, (usually in diploid form), and oxidase positive |
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| what differentiates nonpathogenic strains of neisseria? |
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| non-pathogenic normal flora strains do not have a capsule |
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| what endotoxin do neisseria have? what can they do to IgA? how do they attach to host cells? do they undergo antigenic and phase variation? |
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| LOS, lipooligosaccharide, instead of LPS. they have an IgA protease. they have pili and surface proteins, (Opa), that mediate attachment to host cells. they can undergo antigenic and phase variation, making it hard to create vaccines. |
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| what shape do N. gonorrhoeae have? what problem can they cause in women? |
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| they are gram - diplococci. in women, pelvic inflammatory disease can result in sterility |
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| what is the difference between N. meningitis and gonorrhea? is there a vaccine? what is important about the B serotype |
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| N. meningitis does have a capsule, while gonorrhea does not. it makes several serotypes, B is too similar to our own blood sugars, while the rest: A,C,Y, and W135 can be immunized against |
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| can N. meningitis cause meningitis with or without meningococcemia? does this organism have to die to get into the blood? how well does it grow in blood? how is it tranmitted? |
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| yes N. meningitis can cause meningitis with or without meningococcemia. it can send out membrane blebs with the LOS in it, thus avoiding cell lysis. it can grow quite well in blood. it is transmitted via respiration. |
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| what is the characteristic rash of meningitis? |
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| broken blood vessels |
