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101 Cards in this Set
- Front
- Back
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how do you distinguish between Salmonella and Shigella induced diarrhea?
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Shigella is more likely to cause vomitting
you need to culture to actually know |
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what is the difference between diarrhea and dysentery?
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dysentery is in the colon: mucoid diarrhea
dysentery: more severe, >20 stools/day of low volume |
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ExPEC are found in people with what diseases?
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11% commensal flora
extraintestinal diseases |
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how are EIEC different from other E. Coli?
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they are non-motile, NLF
they are more like Shigella! Infections with EIEC are indistinguishable from Shigellosis |
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how is EIEC different than Shigella?
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Shigella Infectious dose: >10 org
EIEC infectious dose: >10^8 org otherwise they are indistinguishable |
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what is the specific virulence factor of ETEC?
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Heat Labile Enterotoxin (LT)
and/or Heat Stabile Enterotoxin (ST) both produce increased ion/water secretion! |
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how is the intracellular mechanism of ST different than LT
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Heat Stabile Enterotoxin (ST):
activates guanyl cyclase => increased cGMP heat labile enterotoxin (LT): activates adenyl cyclase=> increased cAMP both lead to fluid/electrolyte secretion |
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what strain contains LEE and what genes are contained in LEE?
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EPEC
a pathogenicity island that contains Intimin gene and Translocated Intimin Receptor (Tir) it translocates its own receptors into the epithelial cell |
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how is EHEC transmitted?
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it is located in the intestinal tracts of cows, pigs, and sheep. undercooked/raw meet
low infectious dose >100 org |
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why does O157:H7 cause HUS more than Shigella?
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they both can cause HUS because they both have Stx
O157:H7 is an EHEC so it also has LEE allowing it to infect more often |
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how does Stx cause HUS? What strain causes it?
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when Stx is in the systemic circulation, it damages renal endothelial cells
also leads to hemolysis |
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what types of diseases does UPEC cause?
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cystitis (bladder infection)
pyelonephritis (kidney infection) |
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what are the 3 regions of LPS? which are constant and which are variable?
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Fatty acids (embed in membrane)
Core of unusual sugars (KDO in LPS). Constant among most GNBac O-Antigen (Chain of repeated 3-5 sugar units) |
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what is Lipid A?
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the fatty acid component of LPS that is responsible for toxicity but is NOT immunogenic
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what are the 4 biologic (cell level) effects of LPS?
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1. pyrogenic (IL-1)
2. blocks corticosteroid receptors 3. activates cytokine release 4. activates alternative complement pathway |
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what 2 cytokines are responsible for LPS induced pyrogenesis?
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IL-1 and TNF-alpha
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what are the systemic responses to LPS?
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1. fever
2. endothelial cell damage 3. DIC 4. hypotension |
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how does LPS bind to host cells?
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LPS (or LOS) binds Lipopolysaccharide Binding Protein (LBP) which binds to CD14 on macrophages leading to cytokine release
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how are endotoxins and exotoxins different?
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endotoxins: gram negative
lipopolysaccharide complex heat stable bound to membrane constituitively secreted exotoxins: mostly Gram positive proteins heat labile secreted in regulated fashion |
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what are the 3 main types of exotoxins?
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Membrane disrupting
A-B toxins (B portion for deliver of A, A for enzyme inhibition) Superantigens |
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what are the common characteristics of the Neisseria?
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Gram Negative Diplococci
LOS Aerobic (best in enriched CO2) catalase positive oxidase positive |
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where do Neisseria grow on humans?
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on mucosal surfaces
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do Neisseria produce endotoxins or exotoxins?
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ONLY endotoxins
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What serotypes of Neisseria are endemic in developing countries vs. in the US?
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developing countries: A and C serotypes
USA: B, C, and sometimes Y |
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what are the symptoms of meningitis?
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fever, stiff neck, rash, headache
light sensitivity Kurnig and Brudzinski's sign |
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what is waterhouse-friderichsen syndrome?
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adrenal gland failure due to meningococcemia induced bleeding
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how do you treat invasive meningococcal infection?
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with Beta-lactams (penicillin, somehow it can cross the outer membrane!) or cephalosporin if resistant to Lactams
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the immunogenic component of the meningococcal vaccine is the...
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capsule
BUT, there is no vaccine against the B group because the sialated capsule is too simmilar to human |
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which gender is more symptomatic during N. Gonnorhea infections?
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males!
male to female transmission much more effective |
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why do 2ndary complications of N. Gonorrhea occur more frequently in women than men?
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because women are usually asymptomatic
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how can you diagnose gonococcal infection?
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any gram negative diplococci in males
females: complicated by diverse flora. streak cervical specimen to "Thayer-Martin agar" with Abx against normal flora OR new DNA amplification assay |
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what co-infection is common with gonorrhea?
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chlamydia
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what are the 8 defining characteristics of the Enterobacteriaceae?
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1. gram negative bacilli
2. ox positive 3. cat positive 4. facultative anaerobes 5. nitrate reducers (sign of anaerobes) 6. glucose fermenters 7. grow in presence of bile 8. normal inhabitants of GI of mammals, birds, reptiles |
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what are the 5 LF Enterobacteriaceae?
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1. E. Coli
2. Citrobacter freundii and diversus 3. Klebsiella pneumoniae 4. Enterobacter cloacae 5. Serratia marcescens |
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what are the 5 NLF Enterobacteriaceae?
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1. Salmonella
2. Shigella 3. Proteus mirabilis and vulgaris 4. Providencia stuartii 5. morganella morganii |
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gram negative enterobacteriaciae elicit an exuberant _____ response when they are where?
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elicit an exuberant PMN response when they replicate in the SUB-EPITHELIAL space in response to their LOS
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what do Salmonella colonies look like on Hektoen Enteric agar?
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blue colonies with black centers
this is how you differentiate salmonella from shigella! |
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"O-antigen" refers to
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the saccharide portion of LPS
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"H-Antigen" refers to
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flagella
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"K or Vi antigen" refers to
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capsular antigen
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"F antigen" refers to
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fimbrae
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what causes induction of Salmonella PI-1 genes in the small intestine?
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low fluid shear environment (zero gravity)
this allows for invasion of the epithelium |
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why are antibiotics often contraindicated in people with salmonellosis?
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Abx can increase shedding of the organism...more infected people!
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what is the one Vibrio species that CAN grow without salt?
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V. Cholerae
all others require salt |
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what serotypes of Cholera were responsible for pandemics?
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O1 responsible for the first 6
O1-"El Tor" responsible for number 7 O139 responsible for the alleged "8th" |
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heat labile toxin (LT) is very similar to...
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cholera toxin
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what is the risk if your immune system responds too vigorously to Campylobacter jejuni?
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you could get Giuliann-Barre syndrome where your immune system attacks your peripheral nervous system
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what infection can be clinical indistinguishable from salmonellosis?
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Gastroenteritis due to Campylobacter infection
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H. Pylori infection leads to what immunologic reactions?
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increased gastric acid secretion
IL-8 secretion PMN and lymphocyte infiltration into submucosa |
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what is the least invasive way to diagnose H. Pylori infection?
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detection of H. Pylori antigens in stool
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what is the culture medium specifically designed for Legionella?
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Buffered Charcoal Yeast Extract (BCYE)
comes with and without selective antibiotics |
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who is at risk for legionella infection, and who is NOT at risk?
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elderly, alcohol, smoking
healthy children and adults RARELY get legionella |
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where is the environmental reservoir of legionella?
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inside protozoa which live in ANY moist environment
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how can you diagnose legionella infection?
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immunoassay specific to Serotype-1
Buffered Charcoal Yeast Extract (BCYE) for all serotypes (longer) |
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what is Burkholderia cepacia?
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the exact same as P. Aeruginosa without the pigmented siderophores
an opportunistic pathogen |
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what organism is just like P. Aeruginosa without the pigment siderophores?
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burkholderia cepacia
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what is Stenotrophomonas Maltophilia?
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the exact same as P. Aeruginosa without oxidase
an opportunistic pathogen |
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what organism is the same as P. Aeruginosa except it lacks oxidase?
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Stenotrophomonas Maltophilia
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Acinetobacter Baumannii is referred to as...
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gram negative MRSA
just like P. Aeruginosa, without oxidase, and it is a coccobacilli |
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what is ecythema gangrenosum?
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a very black skin infection secondary to a wound
opportunistic gram neg infection by P. Aeruginosa (also B. capecia, S. maltophilia, and A. Baumannii) |
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what is the current worldwide prevalance of TB?
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1/3 of worlds population!
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what diseases can be caused by m. tubercolosis?
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pulmonary disease (including pleuritis)
meningitis (<5yo in endemic region) miliary (everywhere else: musculoskeletal, CNS, UTI, lymphatic) |
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how does M. tuberculosis seed an infection in human lung?
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low infective dose inhaled deep into lung
phagocytosed by macrophage granuloma forms years of latency, breaks out of granuloma when immunocompromised |
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what two things can cause a false positive mantoux test?
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bcg vaccination
exposure to non-tuberculosis mycobacterium |
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what can cause a false negative mantoux test?
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a non-reactor (10-20% of M. Tuberculosis infections)
immunosuppression recent infection very young |
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what are the 2 main weaknesses of the AFB test?
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50% of people with TB are AFB negative
can't tell non-tuberculous-myco from TB-myco |
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are people with latent TB infectious?
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NO
only infectious when TB is active |
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what is the standard treatment for TB?
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rifampin, pyraziamide, ethambutol, isoniazid for 4 months
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what are the protective benefits of the BCG vaccine?
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the bacillus Calmette Guerin vaccine is protective against TB meningitis but probably not against pulmonary TB
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what is the important host cytokine for TB killing?
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IFN-gamma
can test for TB infection by measuring IFN-gamma response to TB antigen |
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how is TB different in people with HIV/AIDS?
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they are more likely to have drug resistant TB (MDR and XDR)
their presentation is more likely to be less severe, less reliable acid fast sputum results |
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what mycobacterial infection is not more risky when you have HIV/AIDS?
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m. leprae
leprosy |
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what is the main reservoir for m. leprae?
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armadillos
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how do you treat m. leprae?
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multi-drug-treament
rifampin, dapson, clofazamine for a couple months |
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what is the spectrum of m. leprae infections and what causes you to get one or the other?
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there is a tuberculoid pole (granuloma formation) and a leprosy pole (Ab mediated)
if you have bad cell-mediated immunity, m. leprae survies in macrophages and you are more likely to get the leprosy pole |
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why does m. ulcerans create such big ulcers?
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even though it is slow growing, it is usually painless unless there is a secondary infection
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what is the reservoir for m. ulcerans?
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water. people who are in water alot are at risk
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what are scotochromogens, photochromogens, and nonphotochromogens
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scotochromogens: make pigments in dark
photochromogens: make pigments in presence of light nonphotochromogens: never make pigments |
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why kind of infection does m. avium complex cause?
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pulmonary infection in immunocompromised patients...
subcutaneous and lymph node infections |
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histologically, what will M. avium complex infection look like
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macrophages FILLED with AFB
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what is the defining histological feature of nocardia?
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filamentous (looks like mold) and moderately acid fast
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why hasn't vaccination eradicated Bordatella pertussis?
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because vaccinated people can still get a mild form of disease, infecting susceptible, unvaccinated populations
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what are the 4 stages of B. pertussis infection?
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incubation (asymptomatic)
catarrhal (runny nose, conjunctivitis) paroxysmal (whooping cough) convalescent |
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what is the most common cause of cough more than 3 weeks duration?
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B. pertussis
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what VF of B. pertussis is not included in the DTP vaccine?
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the ENDOtoxin
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what disease does Haemophilus ducreyi cause?
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very painful genital ulcers
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how often are people colonized by H. influenzae
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everybody is at some point
at any one point, 25% of people are colonized |
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what is absolutely necessary for diptheria, and how does the pathogen get this gene?
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diptheria toxin (A-B toxin)
gets it from the Beta-phage |
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where is the reservoir of B. Anthracis?
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in the guts of grazing animals
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why is there no human-human transmission of B. anthracis?
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because spores do not form during infection, only infected by endospores
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what is the main source of Listeria monocytogenes?
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unpasteurized milk and cheese
(the only gram positive rod with endotoxin) |
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how are listeria monocytogenes infections controlled?
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a cocktail of 6 phages specific to l. monocytogenes are sprayed on ready eat meats and cheeses
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what are the 3 scenarios where anaerobes are able to cause disease?
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1. GI contents contaminate other organs
2. large wound with low blood supply 3. traumatic imjury with necrotic tissue |
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what is the one pathogenic spore forming anaerobe?
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clostridium
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what is the only pathogenic gram negative cocci anaerobe?
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veillonella
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what are the clues that you may have an anaerobic infection?
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aerobic culture not growing
foul smelling produces gas |
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how does C. tetani infection begin?
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spores land in a wound
germinate slowly under low O2 conditions |
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how is Botulinum toxin released?
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it is released out of lysed C. Botulinum cells in an inactive form, must be cleaved to become active
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from what are people likely to get botulism?
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honey (infants)
home canned foods baked potatoes |
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how do you treat botulism?
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give a trivalent ani-toxin (because it is a toxin mediated disease)
respiratory support |
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presence of what microbe indicates either insignificant baccteremia or sample contamination?
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Proprionibacterium
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