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FUN2: 10:00-11:00
Scribe: Andrew Richardson
Monday, November 10, 2008
Proof: Joan-Marie Manolakis
Dr. Benjamin
Microbiology
Page 1 of 5
SBA=sheep blood agar
Medical Microbiology
I. Outbreaks of bacterial infection [S2,3,4]:
a. E. Coli O157:H7 in spinach – in 2006 there were 204 cases in which 31 cases resulted in hemolytic
uremic syndrome and a need for kidney transplants, cattle with this strain of E. coli were found a mile
away but the disease was transmitted by feral swine that were going from the cattle to the spinach and
back, spinach got mixed into other spinach at a packing house causing an outbreak, there have been 19
outbreaks since 1995, kids and elderly are more at risk. Is a normal flora of cattle
b. Salmonella on tomatoes – in restaurants, the strain Salmonella enterica Thyphimurium came from raw
Serrano and jalapeno peppers in Mexico. Is a normal flora for cattle, pigs, and chicken but they also get
on our vegetables.
II. Salmonella enterica Montevideo in Cadbury chocolate – in the UK, the original isolate did not reach a recall
threshold so no recall was issued, the waxy chocolate carried the organism to the duodenum where it was
able to spread
III. Common characteristics of Enterobacteriaceae [S5]
a. Gram negative rods
b. Rounded ends and straight parallel sides
c. Colony morphology on SBA
i. 2mm colonies (fairly large) of a dull gray color
ii. Some cause a β Hemolysis but others cause an alpha hemolysis (it’s not that important), mucoid,
swarming, and pigmented colonies are other characteristics
d. while it does exhibit a gram neg. stain that is not indicative of enterobacter., other bacteria stain gram
neg. as well like pseudomonas
IV. Gram + v. gram – cell wall and outer membrane [S8]
a. Gram + cell wall has peptidoglycan with crosslinking that forms and hold the cell’s shape
b. Gram – cell wall has smaller PG layer and an outer hydrophobic membrane of proteins and LPS, the
outer membrane has anti-antibiotic properties, all gram – cells have a similar structure
V. LPS and endotoxin [S9, 10, 11]
a. LPS has an O Ag attached, this O Ag differentiates the different strains of E. coli Salmonella and
Shigella
b. LPS/endotoxin are the same thing, our cells detect this and signal that the is a bacterial infection,
however the reaction to LPS can be fatal if there is a considerable amount in our bodies because our
bodies overreact
c. LPS is detected by TLR-4 on cells causing the release of these various cell products which ramp up our
immune response and kill us. LPS does not cause any damage, rather our immune cells do.
FUN2: 10:00-11:00
Scribe: Andrew Richardson
Monday, November 10, 2008
Proof: Joan-Marie Manolakis
Dr. Benjamin
Microbiology
Page 2 of 5
d. Endotoxin resistant (lpsd) mice can be injected with 20x the lethal dose of LPS and not die but are more
susceptible to bacterial infections because they cannot detect the infection
VI. Antigenic structure of enterobacteriaceae [S12]
a. 2400 species of Salmonella based on the variations of the O Ag and flagella (H) Ag combinations
b. The test is done by mixing the Ag and exposed rabbit blood to see if agglutination occurs
c. K Ag is the capsule Ag but is not used that often
d. Antigenic formula: E. coli O157:H7 means that this is the 157th O Ag recognized and the 7th H Ag
recognized (H=flagella), Salmonella enterica serovar typhi ( O9, 12 (Vi):Hd) causes typhoid fever and has
2 O Ag, the Vi is for the capsule and is important for virulence, Hd is for the flagella
VII. Physiology of enterobacteriaceae [S14]
a. Facultative anaerobes which can grow with or without O2 and ferment glucose
b. Oxidase neg.
c. Nitrate pos. meaning they reduce nitrate to nitrite
d. Catalase pos.
e. Motile by way of peritrichous flagella (more than one flagella around the bacteria)
VIII. Oxidation fermentation test [S15, 16, 17]
a. Separates gram neg., contains glucose and acid indicator in a test tube, in the case of a methyl red
indicator if the bacteria produces acid it will turn yellow, put a plug on test tube to see if the bacteria is
anaerobic.
b. Use microscan walkaway to identify organisms in lab, inoculate whole plate with susceptibilities in the
bottom of the plate and identify in the top half of the plate, if the organism grows on it-shows that it’s
resistant on that level, the machine can identify what bacteria it is based on the results in the plate
IX. Identification of species and genera [S18]
a. Biochemical reactions– whether the bacteria can utilize certain sugars, decarboxylate or deaminate
amino acids
b. Can also determine their genetic relatedness by looking at the 16s RNA, not useful for enterobacter.
because they are so close genetically
X. Enterobac. – host interactions [S19]
a. Normal flora that are beneficial, E. coli is an example, helps nutritionally when eating a starchy diet for
example klebsiella fixes nitrogen allowing the proteins the organism makes to be used by the host,
helps in competition against pathogens in gut can enhance with probiotics, and in immunological
stimulation this is seen in bacteria free individuals who have problems combating pathogens in gut
b. Causes opportunistic diseases, sick individuals get disease from their own flora
c. Cause infections in healthy individuals, non-inflammatory diarrhea is caused by E. coli other than the
O157 type, inflammatory diarrhea is caused by Salmonella and Shigella invading the gut causing WBCs
to be in the stool, invasion beyond the gut causes typhoid fever
XI. Escherichia coli
a. Normal flora of mammals and birds
b. Most common enterobacter. in gut
c. Used as an index for fecal pollution in food or water, done by coliform counts that tell if there is gut
contamination but cannot tell if human or not or if it is pathogenic
d. Lactose positive whereas Shigella and Salmonella are not, done on MacConkey agar plate, a positive
test turns pink-the organism used lactose and fermented and produced acid (causing it to turn pink)
e. Salmonella and Shigella are lactose negative!
f. Indole positive
XII. Opportunistic infections of E. coli[S22, 23]
a. UTIs – most common infection of E. coli, predisposition because of female anatomy and a shorter
urethra, E. coli causes cystitis, sexual activity can allow the organism to get into bladder (honeymoon
cystitis), pregnancy and childbirth also causes UTIs, males get UTIs at an older age because of prostatic
hypertrophy. Catheterizations can cause UTIs as well as failure to empty bladder
b. Peritonitis from ruptured gut
c. Septicemia secondary to UTIs or pneumonia which causes organisms to grow in blood
d. Wound infections on the lower of the body more susceptible to fecal contamination
XIII. E. coli enteric pathogens [S24, 25]
a. 4% of diarrhea is caused by E. coli, only O157 E. coli is detectable in the lab
b. EPEC – enteropathogenic E. coli causes infantile diarrhea
c. EAEC – enteroaggregative E. coli causes traveler’s diarrhea in 30-40% of visitors to Mexico
d. EHEC – enterohemorrhagic E. coli causes hemolytic uremic syndrome and is the one we can detect
(this is the important one)
FUN2: 10:00-11:00
Scribe: Andrew Richardson
Monday, November 10, 2008
Proof: Joan-Marie Manolakis
Dr. Benjamin
Microbiology
Page 3 of 5
e. Enteroinvasive E. coli causes bacillary dysentery
XIV.
Klebsiella pneumoniae [S26-30]
a. Lactose pos., produces pink colonies and non-colored background on a MacConkey plate
b. No flagella so nonmotile and H Ag neg.
c. Large capsule, 77 K Ags
d. Β-lactamase production makes them resistant to ampicillin and carbenicillin but sensitive to
cephalosporins
e. Gram neg. with a capsule which is a virulence factor that allows them to survive
f. Klebsiella pneumonia: causes pneumonia which has a 25-50% mortality rate, mainly
immunocompromised individuals contract this disease, thick non-purulent (lacking WBCs) bloody
sputum, necrosis and abscess formation, can cause septicemia, sometimes urinary tract infections and
meningitis-it’s an opportunistic bacteria that’s not necessarily common in people
g. Predisposing factors for enterobacter pneumonia: hospitalization and nosocomial infections, on a
respirator, old age, aspiration of oral secretions, alcoholism, diabetes mellitus by suppressing the
immune response and having more glucose available, chronic bronchopulmonary disease by not being
able to cough well
XV. Enterobacter cloacae / E. aerogenes [S31]
a. Lactose pos.
b. nonmotile
c. causes UTIs through nosocomial infections
d. have cephalosporinase (the gene is ampC) which make it ampicillin and cephalothin resistant
e. Test susceptibility by disc diffusion antimicrobial test which has discs with antibiotics placed
throughout dish with organism growing. The effective antibiotics cause a ring of death that is measured
to test resistance
XVI.
Proteus mirabilis / P. vulgaris [S33]
a. Urease pos. enterobacter, turns test tube pink
b. Highly motile, smells bad
c. H2S positive which is important because Salmonella is also positive and can be mistaken for Salmonella
d. Cause UTIs, wound infections, pneumonia, septicemia
e. Tetracycline, ampicillin and cephalosporin resistant
XVII. Food borne illness [S35-39]
a. Normal adult – 9 liters of fluid enters duodenum, 1.5 liters crosses the ileocecal valve, .1 liters is passed
by the anal sphincter
b. Osmotic diarrhea – increased intra-luminal osmotic pressure due to lack of absorption of fluids and
solutes in gut, lactose intolerance and giardia lamblia cause this type of diarrhea, fasting stops diarrhea
c. Secretory diarrhea – malfunction of Na absorption mechanism and increased Cl secretion caused by an
increased mucosal cAMP that is caused by bacterial toxins, fasting does not stop diarrhea
d. Bacillary dystentery – caused by a Shigella invasion of colonic mucosa, have frequent small volume
stools with blood and mucus in it along with abdominal cramps
XVIII. Incidence of food borne illness [S40-42]
a. 76 million cases annually in the U.S.
b. 80,000 hospitalizations
c. 5,000 deaths
d.
FUN2: 10:00-11:00
Scribe: Andrew Richardson
Monday, November 10, 2008
Proof: Joan-Marie Manolakis
Dr. Benjamin
Microbiology
Page 4 of 5
e. Most food borne outbreak etiology is not known, but out of those known Salmonella is the most
common
XIX.
Vibrio cholerae [S44]
a. Non-enterobacter.
b. 1-5 day incubation period
c. Profuse watery diarrhea, spread by contaminated water, takes 107 CFUs to cause infection
d. Cholera toxin
i. B subunit binds intestinal cells
ii. A subunit activates adenyl cyclase irreversibly which results in water and electrolyte secretion
e. Treatment is to hydrate orally and replace the electrolytes in the same amount that it is released
XX. Enterotoxigenic E. coli (ETEC) [S46]
a. Watery diarrhea is a secretory diarrhea related to cholera
b. Is a labile toxin which means it is heat inactivated
c. Can also produce a stable toxin that activates cGMP
d. Toxins are coded by plasmid DNA
XXI.
Bacterial food poisoning [S47, 48, 49]
a. Invasive causes of food poisoning from Salmonella, Campylobacter, Shigella, EIEC, Yersinia, and EHEC
b. Salmonella enterica– 2400 serotypes named by O and H Ag, lactose neg. and H2S pos.( black colony),
common serotypes are enteric typhimurium enteric enteritidis and enteric newport, causes enteric fever
where the organism gets into the blood and grows in the liver and spleen, causes enterocolitis and
diarrhea, also causes bacteremia where it gets into the blood
c. Source of Salmonella infection is water, meat, diary, and human carriers
XXII. Enteric Fever/ Tyhpoid fever [S54-56]
a. Caused by S. enteric typhi/paratyphi
b. Humans are the only host
c. Rare in the U.S.
d. Pathogenesis of typhoid fever
e. Grows inside macrophages of liver and spleen
f. Vaccine – whole killed organisms with LPS that causes injection site irritation, not effective and lasts for
a year, live vaccine of a mutagenized strain that is not very effective either
XXIII. Campylobacter jejuni [S57]
a. Non-enterobacter., gram neg. rod, carried by animals
b. 1-7 day incubation period, common cause of food borne illness
c. Symptoms are fever, bloody diarrhea and abdominal pain
d. Most infections are from contaminated water and food, college age students tend to get this due to lack
of cooking knowledge (second weaning), cooking and microwaving kills organism
XXIV. EIEC
a. Causes bacillary dysentery
b. Large virulence plasmid related to Shigella
FUN2: 10:00-11:00
Scribe: Andrew Richardson
Monday, November 10, 2008
Proof: Joan-Marie Manolakis
Dr. Benjamin
Microbiology
Page 5 of 5
c. O Ag and adhesions are coded on virulence plasmid
XXV. EHEC
a. Mild diarrhea and hemolytic uremic syndrome
b. Most common outbreak strain – O157:H7
XXVI. Hemolytic uremic syndrome (HUS)
a. A Toxin that targets the 28s ribosome and destroys it by removing adenosine
b. B toxin that targets Gb3 or Pk Ag CD77 which activates apoptosis
c. Renal glomeruli contain lots of Gb3 so HUS causes renal failure and hemolytic anemia
XXVII. Shigella
a. Related to E. coli
b. 4 named species, lactose neg., non-motile
XXVIII. Bacillary dysentery
a. Oral inoculation in 1-3 days, high numbers in small bowel
b. Humans are the only normal host, only need 200 organisms to infect
c. Jthe 4 F’s of Shigella transmission are feces, fingers, flies, and food
d. High volume diarrhea
e. Invades colon epithelium
f. Dystentery – small volume bloody mucoid stool
g. Treat with ampicillin and bactrim
h. Epidemics occur where sanitation breaks down
XXIX. Yersinia enterocolitica
a. Enteric infection
b. Mucosal ulcerations in terminal ilium, inflamed mesenteric nodes
c. Virulence depends on invasion of intestinal cells
d. Can have RBCs and WBCs in stool
e. Symptoms are abdominal pain and diarrhea, can be confused with appendicitis, transmitted by food
XXX. Y. pestis
a. Causes bubonic and pneumonic plague
b. Bubonic is from a bite from an infected flea
c. Pneumonic is from person to person or person to animal