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71 Cards in this Set
- Front
- Back
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Components of MAC agar
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-crystal violet and bile salts (inhibit growth of Gram positive organisms)
-neutral red (pH indicator) -lactose |
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Red colony on MAC agar means?
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bacteria ferments lactose
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Components of EMB
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-lactose
-Eosin -methylene blue |
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Positive/negative result on EMB = ?
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Lactose fermenters precipitate dyes
purple centers OR green metallic sheen Lactose non fermenter: Light pink, translucent |
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Components of HEK agar
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lactose, sucrose, salicin
bromthymol blue pH indicator bile salts |
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Result on HEK
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fermentation causes yellow, salmon or orange color otherwise translucent green
ferric ammonium citrate black ppt if H2S producer |
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Component of Triple sugar iron agar
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Sugars
-glucose (1 part) -lactose (10 parts) -sucrose (10 parts) Phenol red -pH indicator acid fermentation -red to yellow Ferrous sulfate -turns black in presence of H2S Proteins: Beef and yeast extract |
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Enterotoxigenic E. coli Physiology and structure
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Gram negative rod
lactose fermentation |
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Enterotoxigenic E. coli Virulence factors
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heat labile toxin (LT)
-structure-mechanism (cholera) heat stable toxin (ST) -stimulation of guanylate cyclase attachment pili -Able to attach to epithelium |
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Enterotoxigenic E. coli entry?
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ingestion of contaminated food or water
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Enterotoxigenic E. coli Establishment
& Mechanism of disease |
attachment to small intestinal epithelial cells
-bacteria do not invade secretion and uptake of toxin -heat labile -heat stable |
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Enterohemorrhagic E. coli antigens
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O & H
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Enterohemorrhagic E. coli Virulence factors
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Shiga like toxin
-phage encoded |
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Enterohemorrhagic E. coli agar speciality?
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Grows on sorbitol plate
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E. coli O157:H7 Epidemiology
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undercooked meats
Fecally contaminated water foods (coleslaw, cheese, unpasteurized apple juice) Very few organisms needed for infection |
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E.coli O157:H7 Clinical syndromes
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Secretory diarrhea
-inucubation period of 2-3 days -Non-bloody -Most patients will not get other symptoms severe abdominal pain, bloody diarrhea -If bacteria get to colon only -Can be accompanied by fever hemorrhagic colitis hemolytic uremic syndrome (HUS) -Triad of acute renal failure, thrombocytopenia & hemolytic anemia -10% of patients who get bloody diarrhea will get this |
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Salmonella enterica Physiology and structure
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Gram negative rod
motile does not ferment lactose |
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Salmonella enterica Epidemiology
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food contamination
fecal oral spread |
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antacids increase susceptibility to Salmonella enterica True or False?
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True
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Salmonella enterica Pathogenesis
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attachment to epithelial cells
uptake by epithelial cell replication in endosome penetration to subepithelial tissue inflammatory response |
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Salmonella typhi Clinical syndromes
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incubation period 7-21 days
can start out as diarrhea fever, malaise, anorexia, headache, myalgia long term fever 3-4 week course without treatment (typhoidal) complications: infection of bone, heart valves, brain |
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Salmonella typhi Virulence factors
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Vi polysaccharide - capsule
endotoxin |
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Salmonella typhi Mechanism of disease
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invasion of M cells in Peyer’s patches in terminal ilieum
Replication and transport to subepithelial survival in macrophages entry into blood and lymphatics replicate in liver and spleen prolonged release of endotoxin gall bladder colonization- shed in bile |
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Shigella Physiology and structure
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Gram negative rod
non motile classified by “O” antigens no “H” antigens does not ferment lactose Relatively biochemically inactive |
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Shigella Virulence factors
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Shigatoxin
virulence plasmid |
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Shigella Establishment
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attachment to “M” cells
bacterial directed endocytosis -virulence plasmid escape from endosome replication in cell lysis and spread to adjacent cells (basal and lateral) |
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Dysentery symptoms
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blood and pus
fever, abdominal pain, cramps acute and self limiting 2-7 days |
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Dysentery causative agents
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EIEC
EHEC - O157:H7 Salmonella enterica (typhimurium) Shigella sp. Campylobacter jejuni Clostridium difficile Yersinia entercolitica |
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Yersinia entercolitica Physiology and structure
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Gram negative bacillus
motile (conditional on temperature) Non-motile @ body temperature, but motile @ cold T flagella produced at 22C not 37C Growth at 4C |
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Yersinia entercolitica Epidemiology
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fecal oral spread
transmission through milk, food and water Common in Scandinavia and cold areas of North America increased metabolic activity at lowered temp |
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Yersinia entercolitica Clinical syndromes
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diarrhea, fever, abdominal pain in right lower quadrant Due to necrosis of the lymph nodes
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Yersinia entercolitica post infective sequelae
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reactive arthritis
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Yersinia entercolitica Pathogenesis and immunity
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invasive
heat stable enterotoxin similar to E.coli ST |
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Campylobacter jejuni Physiology and structure
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Gram negative rod
small - 0.3 u S or comma shaped motile single polar flagella darting corkscrew motility |
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Campylobacter jejuni special growth requirements
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reduced oxygen
increased CO2 elevated temperature |
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most common cause of bacterial gastroenteritis?
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Campylobacter jejuni
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Campylobacter jejuni Transmission
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animal reservoirs
chickens #1 cattle swine dogs and cats contaminated foods chicken, turkey, beef, pork, fish, milk, raw seafood, mushrooms contaminated water fecal contamination from animals |
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rare complication of Campylobacter jejuni?
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Guillain-Barre syndrome
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Campylobacter jejuni Virulence factors
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flagella
adhesin (attachment) endotoxin enterotoxin cytopathic toxin |
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Helicobacter pylori Physiology and structure
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Gram negative spiral shaped rod
corkscrew motility hard to grow |
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Helicobacter pylori Virulence factors
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urease
motility and mucinase adherence factors endotoxin cytotoxin |
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General Properties of Anaerobic Bacteria
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growth inhibited or killed by oxygen
reduced levels of catalase and superoxide dismutases considerable variation in oxygen sensitivity pH and redox potentials (Eh) are important factors too |
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Obligate anaerobe
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bacteria that fail to grow in the presence of any oxygen. Often lack superoxide dismutase, catalse and cytochrome systems
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Facultative
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bacteria that grow in the presence or absence of oxygen; these are the predominant pathogens
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Microaerophilic
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aerortolerant bacteria that tolerate small amounts of air
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fecal anaerobes are typically resistant to penicillins while oral anaerobes respond to penicillins... True or False?
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True
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Bacteroides fragilis Physiology and Structure
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pleomorphic, gram(-) rod, capsulate, no spores, weak LPS endotoxin
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Bacteroides fragilis Establishment
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agglutinins, IgA protease; IgM mediates phagocytosis by neutrophils
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Clostridium perfringens Physiology and Structure
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Gram(+)rod ; spores; aerotolerant
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Clostridium perfringens Clinical Syndromes
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Bacteremia, myonecrosis (gas gangrene)
Cellulitis, fasciitis Food poisoning Enteritis necroticans (Type C linked to rare and lethal food poisoning in malnourished children). |
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aseptic Meningitis is due to?
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viruses, TB, fungi
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septic or purulent Meningitis is due to?
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Bacteria
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Meningitis is an Inflammatory disease characterized by?
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infiltration of neutrophils (and mononuclear cells)
-obstruction -block reabsorption of CSF -increased intracranial pressure -herniation of temporal lobe or cerebellum -compression of midbrain -respiratory arrest |
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Common clinical symptoms of Meningitis
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fever, headache, stiff neck, vomiting, photophobia, lethargy, confusion, coma
Infants - jaundice, diarrhea, irritability, convulsions |
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Causative Agents of Meningitis -bacteria
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Neisseria meningitidis
Haemophilus influenzae Streptococcus pneumoniae Staphylococci Escherichia coli Group B Streptococcus Listeria monocytogenes |
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Causes of Meningitis in neonates?
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Group B Streptococcus
-Streptococcus agalactiae Gram negative rods -E. coli Listeria monocytogenes |
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Causes of Meningitis in children?
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Neisseria meningitidis
Streptococcus pneumoniae Haemophilus influenzae |
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Causes of Meningitis in adults?
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Streptococcus pneumoniae
Neisseria meningitidis Staphylococci -S. aureus -S. epidermidis Listeria monocytogenes |
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Neisseria meningiditis (Gram negative diplococcus) Virulence factors
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capsule
endotoxin IgA protease attachment pili |
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Haemophilus influenzae Virulence factors
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capsule
endotoxin IgA protease attachment pili |
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Haemophilus influenzae media requirements
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X and V factors
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Streptococcus pneumoniae (Gram positive, Alpha hemolytic, Catalase negative, Lancet shaped diplococci)
Virulence factors |
polysaccharide capsule
IgA protease |
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Staphylococcus Virulence factors
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toxins, coagulase, capsule (some), protein A (binds Fc), others
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Escherichia coli Virulence factors
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K1 surface polysaccharide capsule + endotoxin
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Listeria monocytogenes (Gram positive rod, Growth at low temperatures) Virulence factors
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internalin
listeriolysin O |
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UTI: Escheria Coli virulence factor
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P pili (fimbriae)
-Binds galactose-containing receptors on uroepithelial cells Capsular K antigens (pyelonephritis) Human serum resistence Hemolysins (cytotoxins) LPS |
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UTI: Proteus Mirabilis
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Produces urease (Urea Ammonia)
Raises urine pH (Toxic to renal cells) causes massive renal cell destruction Promotes renal stones (Nidus for infections) |
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Treponema - Virulence Factors
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Outer Membrane Proteins - adherence to host cell
Hyaluronidase - facilitates perivascular invasion Fibronectin - from the host cell. Protection against phagocytosis Can survive in phagocytic cell |
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Vibrio vulnificus is associated with?
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raw shellfish
95% of all seafood related deaths seawater infections of wounds |
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Watery Diarrhea is associated with which organisms?
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Vibrio cholerae
Escherichia coli -ETEC -EPEC -EAggEC Clostridium perfringens Clostridium difficile Staphylococcus aureus Bacillus cereus |
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M. pneumoniae Virulence factors
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terminal adhesion protein (P1, base of cilia), stimulation of cytokine release
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