Download Gram Negative Bacteria

CLASS: 10:00 – 11:00
DATE: October 25, 2010
PROFESSOR: Benjamin
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Gram-Negative Bacteria
Scribe: Adam Baird
Proof:
Page 1 of 8
MEDICAL MICROBIOLOGY: ENTEROBACTERIACEAE AND OTHER GRAM-NEGATIVE BACILLI [S1]
E. COLI O157:H7 SPINACH [S2]
a. 8/2006 – 10/2006
1. 26 states nationwide
2. 204 cases
3. 103 hospitalizations
4. 31 HUS
5. 3 Deaths
b. Since 1995, there have been 19 outbreaks of food borne E. coli O157:H7 presumably found in lettuce and
leafy greens; found in cattle (the normal host of E. Coli O157:H7) one mile away and feral swine in the area.
c. Very infectious organism; can cause symptoms with very few organisms (as little as 1- 10 organisms).
SALMONELLA ON RESTAURANT TOMATOES [S3]
a. 9/14/2008 – 10/2/2008
1. 21 states nationwide
a. Highest reporting states: MA (50), CT (28), KY (19), MN (14), NH (14)
2. 183 cases
3. 22 hospitalizations
b. Salmonella enterica Typhimurium
c. Raw serrano and jalapeño peppers
d. Takes a higher dose of organisms to infect a host than E. Coli O157:H7
CABURY CHOCOLATE: SALMONELLA ENTERICA MONTEVIDEO [S4]
a. 65 cases of salmonella enterica Montevideo in Great Britain
b. Salmonella can survive in chocolate for a long period of time
c. 6 months before cases occurred, Cadbury has a salmonella enterica Montevideo isolate from an ingredient
d. Leaking pipe at one of Cadbury’s main factories
e. Cadbury’s rational for not acting on the original isolate is that the numbers identified did not reach a recall
“threshold”; the amount of possible salmonella in each chocolate was presumably low enough to not cause
any harm. The waxy chocolate, though, acts as a protective barrier for the salmonella, so the salmonella
wasn’t destroyed by stomach acid. Even a low dose of salmonella could cause symptoms.
COMMON CHARACTERISTICS OF ENTEROBACTERIACEAE [S5]
a. Both E. coli and salmonella are forms of enterobacteriaceae
b. Physiological characteristics of enterobacteriaceae:
1. Gram-negative rods
2. Rounded ends and straight parallel side
3. Colony morphology on sheep blood agar
a. ~2mm colonies (relatively large growth)
b. Usually dull gray
c. Other characteristics that might be present: hemoysis, mucoid, swarming, pigmented
colonies, etc.
PICTURE: SPUTUM GRAM STAIN [S6]
a. Notice the red gram-negative rods. (Blue would indicate gram-positive bacteria.)
b. However, just looking at this slide, it is not possible to identify which strain of enterobacteriaceae it is.
PICTURE: E. COLI [S7]
a. Notice the nice, large colonies.
FIGURE: GRAM-POSITIVE CELL WALL VS. GRAM-NEGATIVE CELL WALL AND OUTER MEMBRANE [S8]
a. Left Figure: Gram-negative cell wall.
1. Relatively complex cell wall
2. Notice: Small peptidoglycan layer, outer membrane with lipopolysaccharide (the endotoxin, which is
very important for gram-negative cells).
b. Right Figure: Gram-positive cell wall.
1. Relatively simple cell wall
2. Notice: Plasma membrane with outer peptidoglycan. Recall that the peptidoglycan is the structure
that retains the blue coloration of gram staining, which is why gram-positive cells remain blue.
FIGURE: NO TITLE [S9]
a. Gram-negative description of lipopolysaccharide function:
1. The lipopolysaccharide (endotoxin) stimulates a large number of the host’s cells (like granulocytes,
macrophages, monocytes, vascular cells, B-cells, T-cells, and stem cells). The stimulation of these
cells fires off defenses and triggers recruitment of additional mediators (like complement factors,
CLASS: 10:00 – 11:00
Scribe: Adam Baird
DATE: October 25, 2010
Proof:
PROFESSOR: Benjamin
Gram-Negative Bacteria
Page 2 of 8
clotting cascade, etc.) in the host in hopes to destroy the bacteria. This reaction, however, can also
harm the host, leading to fever, hypotension, tachycardia, tachypnea, neutropenia, or potential multiorgan failure and death.
X.
ENDOTOXIN RESISTANT MICE [S10]
a. Endotoxin resistant mice (lpsd): mice that spontaneously occurred during research; these mice, when given
large doses of endotoxin, did not get sick (even though usually lethal doses up to 1 mg of lipopolysaccharide
were given),
b. However, these endotoxin resistance mice (lpsd) were more susceptible to infection by salmonella (because
their bodies didn’t recognize the infection and didn’t respond to it).
c. Two different spontaneous mutations seen:
1. One mutation seen in a single base pair mutation
2. One mutation seen in a large deletion
d. The endotoxin resistant mice (lpsd) mutation is “tlr4” (“toll-like receptor 4”, an endotoxin receptor gene that
detects the lipopolysaccharide of gram-negative bacteria in mice)
XI.
FIGURE: ANTIGENIC STRUCTURE OF ENTEROBACTERIACEAE [S11]
a. The antigenic structure is used to identify the organism (especially salmonella and shigella).
b. The lipopolysaccharide is made up of the o-antigen, the o-polysaccharide, and the lipid-a portion (which is
common in all gram-negative bacteria). A host might be immune to one of the components of the
lipopolysaccharide, but it won’t be immune to all of the components. The antigenic structure is very important.
XII.
ANTIGENIC FORMULA OF ENTEROBACTERIACEAE [S12]
a. Escherichia coli typing
1. Example: E. Coli O157:H7 – The “O” portion of the disease results from the 157th o-antigen. The “H”
portion of the disease results from the flagella (the motility organism of the bacteria).
2. Example: O75:K100:H5 – The “O” portion of the disease results from the 75th o-antigen. The “K”
portion of the disease results from the capsule. The “H” portion of the disease results from the
flagella.
b. Salmonella enterica serovar Typhi
1. O9, 12(Vi):Hdc. Salmonella enterica serovar Typhimrium
1. O1,4,512:Hi:1,2
d. There are 2400 different salmonella types.
e. Note: Dr. Benjamin did not discuss the antigenic formula for salmonella.
XIII.
PHYSIOLOGY OF ENTEROBACTERIACEAE [S13]
a. Physiological characteristics of enterobacteriaceae:
1. Facultative anaerobes – They can grow aerobically or anaerobically, although they prefer to grow
aerobically because they can get energy from sugar sources.
2. Ferment glucose
3. Oxidase negative
4. Nitrate positive
5. Catalase positive – For example, if peroxide drops were placed on enterobacteriaceae, it would be
broken down to oxygen and hydrogen (displayed by bubbles).
6. Peritrichous flagella (multiple flagella) for motility
XIV.
PICTURE: OXIDATION FERMENTATION TEST [S14]
a. Oxidation Fermentation Test determines if bacteria are facultative anaerobes.
b. Tubes contain glucose. If yellow = acid produced.
c. A plug can be added to the tube to exclude oxygen.
XV.
IDENTIFICATION OF SPECIES AND GENERA [S15]
a. How are species and genera identified?
1. Biochemical Reactions
a. Fermentation of carbohydrates pH change
b. Decarboxylation of amino acids
c. Deamination of amino acids
2. Genetic Relatedness – Relatively expensive; might be more useful in future.
a. 16s RNA
b. DNA hybridization
XVI.
PICTURE: MICROSCAN WALKAWAY [S16]
a. Microscan Walkaway holds 96 plates. Bacteria can be placed on plates in chamber overnight. The Microscan
Walkaway will monitor each plate, recognize which chemical are broken down in each bacterial plate,
compare it to a database, and record the name of the bacteria. It’s usually fairly accurate.
CLASS: 10:00 – 11:00
Scribe: Adam Baird
DATE: October 25, 2010
Proof:
PROFESSOR: Benjamin
Gram-Negative Bacteria
Page 3 of 8
XVII. PICTURE: GRAM-NEGATIVE MICROSCAN PANEL [S17]
a. This is the plate that is used in the Microscan Walkaway.
b. Helps identify various drug resistances of bacteria
XVIII. ENTEROBACTERIACEAE HOST INTERACTIONS [S18]
a. Enterobacteriaceae interacts with:
1. Normal Flora – Which is nutritionally beneficial for humans. Normal flora provides competition and
immunological stimulation in humans as well.
b. Enterobacteriaceae can lead to:
1. Opportunistic Infections (In Immunologically Compromised Individuals)
2. Infections (In Healthy Individuals)
a. Non-inflammatory diarrhea
b. Inflammatory invasive diarrhea
c. Invasive systemic infections (like typhoid and sepsis)
XIX.
ESCHERICHIA COLI [S19]
a. E. Coli is normal flora found in mammals and birds
b. E. Coli is the most common enterobacteriaceae in the gut (although amount of E. Coli may fluctuate in the
gut)
c. E. Coli coliform counts are used as an index of fecal pollution for food or water. If water, for example, has a
high E. Coli coliform count, fecal matter may be the source of contamination, making it unsafe to drink.
d. Physiological Characteristics:
1. E. Coli is lactose positive.
2. E. Coli is indole positive.
XX.
PICTURE: MACCONKEY AGAG PLATE [S20]
a. Picture showing lactose fermentation of E. Coli.
b. The E. Coli reacts with the lactose in the plate medium, producing acid. (Note the pink/purple color change of
the active E. Coli and the lack of color change in the inactive E. Coli.)
XXI.
PREDISPOSING FACTORS FOR URINARY TRACT INFECTIONS [S21]
a. E. Coli can cause urinary tract infections (URI). Predisposing factors for URI:
1. Female anatomy – Because females have a short urethra, E. Coli can easily get into the bladder.
2. Honeymoon cystitis in females – Cystitis is urinary bladder inflammation; can be caused by sexual
intercourse, where the normal flora from female’s vagina and gut can pushed E. coli into the bladder.
3. Pregnancy and childbirth – Can cause bladder insufficiency and bladder problems, leading to cystitis.
4. Male prostatic hypertrophy – Enlarged prostate gland (typically in older males), which inhibits
emptying of the bladder, allows bacteria to set up and potentially cause infection.
5. Catheterization or other mechanical manipulations
6. Failure to empty the bladder
XXII. OTHER OPPORTUNISTIC INFECTIONS [S22]
a. Other opportunistic infections that E. Coli causes:
1. Peritonitis (inflammation of the peritoneum) from ruptured gut
2. Septicemia (whole body inflammation) secondary to UTI or pneumonia
3. Wound infections
XXIII. ESCHERICHIA COLI [S23]
a. E. Coli can specifically cause diarrhea:
1. E. Coli causes an estimated 4% of diarrhea in US
2. Even higher percentages of diarrhea cause by E. Coli in developing countries
3. E. Coli causes diarrhea in 30-40% of visitors to Mexico (called “Travelers Diarrhea”)
XXIV. E. COLI ENTERIC PATHOGENS [S24]
a. E. Coli Pathogens:
1. Enteropathogenic E. Coli (EPEC) – Infantile diarrhea
2. Enteroaggregative E. Coli (EAEC) – Traveler’s diarrhea
3. Enterotoxigenic E. Coli (ETEC) – Traveler’s diarrhea
4. Enterohemorrhagic E. Coli (EHEC) – Hemolytic Uremic Syndrome
5. Enteroinvasive E. Coli – Bacillary dysentery
b. (It is not necessary to memorize these, but it’s important to be aware of the different types of E. Coli that can
cause diarrhea)
XXV. KLEBSIELLA PNEUMONIAE [S25]
a. Another very common enterobacteriaceae.
b. Characteristics
1. Lactose positive
CLASS: 10:00 – 11:00
Scribe: Adam Baird
DATE: October 25, 2010
Proof:
PROFESSOR: Benjamin
Gram-Negative Bacteria
Page 4 of 8
2. Does not cause diarrhea
3. Non-motile
4. Large capsule (77K antigens)
5. Beta-lactamase (resistant to ampicillin and carbenicillin; sensitive to cephalosporins)
XXVI. PICTURE: LACTOSE POSITIVE KLEBSIELLA SP [S26]
a. Klebsiella can cause large mucoid, slimy colonies.
b. Pink coloration (because it is lactose positive).
XXVII. PICTURE: KLEBSIELLA PNEUMONIAE PNEUMONIA [S27]
a. Gram stain of kelbsiella pneumoniae.
b. Notice the pink, gram-negative rods with large capsules (made of “sugary slime”)
XXVIII. PREDISPOSING FACTORS FOR ENTEROBACTERIACEAE PNEUMONIA [S28]
a. Predisposing factors for enterobacteriaceae pneumonia:
1. Hospitalization
2. Respirator
3. Increased age
4. Aspiration of oral secrections
5. Alcoholism
6. Diabetes mellitus
7. Chronic bronchopulmonary disease
XXIX. KLEBSIELLA PNEUMONIAE DISEASE [S29]
a. Klebsiella pneumoniae can cause various diseases:
1. Pneumonia (25-50% mortality rate; characteristics include thick non-purulent bloody sputum and
necrosis and abscess formation)
2. Septicemia (Whole body inflammation)
3. Urinary Tract Infection (URI)
4. Meningitis
XXX. ENTEROBACTER CLOACAE E. AEROGENES [S30]
a. Physiological characteristics of enterobacter cloacae:
1. Lactose positive
2. Non-motile
3. UTI (often nosocomial, meaning that it results from hospitalization or other healthcare services)
4. Cephalosporinase (breaks down beta-lactam drugs; ampicillin and cephalothin resistant)
XXXI. PICTURE: DISC DIFFUSION ANTIMICROIAL SUSCEPTIBILITY TESTING [S31]
a. Sample organism spread all over the plate. Antibiotics discs are added to the plate. Each drug has a different
zone size.
XXXII. PORTEUS MIRABILIS, P. VULAGRIS [S32]
a. Physiological characteristics of porteus mirabilis:
1. Urease positive
2. Highly motile (and will swarm on plate)
3. Bad smelling odor
4. H2S positive
b. Disease characteristics of porteus mirabilis:
1. Can lead to infections:
a. UTI (commonly aquired)
b. Wound infections
c. Pneumonia
d. Septicemia (whole body inflammation)
2. Tetracycline resistant (tetracycline is rarely used clinically though)
3. Ampicillin resistant
4. Cephalosporin resistant
XXXIII. PICTURE: UREASE TEST [S33]
a. Negative = no pH increase, no color change
b. Positive = ammonia is produced, pink color change
XXXIV. PICTURE: FOOD BORNE ILLNESS [S34]
XXXV. NORMAL ADULT [S35]
a. Normal adults have:
1. 9.0 liters of fluid entering the duodenum every day (saliva recirculation)
2. 1.5 liters crossing the ileocecal valve
3. 0.1 liters passed by the anal sphincter
CLASS: 10:00 – 11:00
Scribe: Adam Baird
DATE: October 25, 2010
Proof:
PROFESSOR: Benjamin
Gram-Negative Bacteria
Page 5 of 8
b. Volume of diarrhea can help determine which level of the gut is infected.
XXXVI. OSMOTIC DIARRHEA [S36]
a. Osmotic diarrhea causes:
1. Increased intra-luminal osmotic pressure
2. Decreased absorption of fluid and solutes
3. Causes of osmotic diarrhea (may be caused by lactose intolerance, giardia lamblia)
4. Fasting stops osmotic diarrhea
XXXVII. SECRETORY DIARRHEA [S37]
a. Secretory diarrhea causes:
1. Malfunction of sodium absorption
2. Increased chlorine secretion
3. Mucosal cAMP increases as a result of the malfunction of sodium absorption and the subsequent
increase of chlorine secretions
4. Bacterial toxins cause increases of cyclic nucleotides in mucosal ells
5. Fasting does not stop secretory diarrhea
XXXVIII. VIBRIO CHOLERAE [S38]
a. One of the most common causes of secretory diarrhea is vibrioi cholerae. (Currently, there is a cholera
outbreak in Haiti.)
b. Physiological characteristics of vibrio cholerae:
1. Not an enterobacteriaceae.
2. Curved rod.
3. Oxidase positive.
c. Disease characteristics of vibrio cholerae:
1. 1-5 day incubation period
2. Profuse water diarrhea (about 20L a day)
3. Spread by contaminated water
4. Stomach acid offers protection (high dose is needed for infection; infection dose is 10 7 FCU)
5. Cholera toxin
a. B subunit binds intestinal cells
b. A subunit irreversibly activates adenyl cyclase
c. Results in water and electrolyte secretion
d. Treatment for vibrio cholerae:
1. Fluid rehydration (oral)
2. Electrolyte replacement
XXXIX. PICTURE: NO TITLE [S39]
a. Cholera cot in Lusaka Zambia
b. 5-gallon bucket placed under the hole in the cot. This helps determine how much fluid rehydration is needed
XL.
ENTEROTOXIGENIC E. COLI (ETEC) [S40]
a. Can’t be identified in the lab.
b. Physiological characteristics of ETEC:
1. Labile toxin (related to cholera toxin)
a. Activates adenylate cyclase (cAMP)
b. Increased permeability to sodium and chlorine
2. Stabile toxin
a. Activates guanylate cyclcase (cGMP)
b. Decreases absorption of sodium and chlorine
3. Note: Toxins are coded by plasmid DNA
c. Disease characteristics of ETEC:
1. Watery diarrhea (secretory diarrhea)
XLI.
BACILLARY DYSENTERY [S41]
a. Bacillary dysentery is caused by bacterial invasion of colonic muscosa
b. Disease Characteristics:
1. Frequent small volume stools (often containing blood and mucus)
2. Severe abdominal cramps
XLII.
INCIDENCE OF FOOD BORNE ILLNESS IN THE US [S42]
a. About 76 million cases of food borne illnesses annually
b. 80,000 hospitalizations annually
c. 5,000 deaths annually
d. Food borne illnesses in the US don’t cause more disruptive symptoms than anything else
CLASS: 10:00 – 11:00
Scribe: Adam Baird
DATE: October 25, 2010
Proof:
PROFESSOR: Benjamin
Gram-Negative Bacteria
Page 6 of 8
e. $7 billion - $17 billion in medical and social costs
XLIII. THE RISK OF FOOD BORNE DISEASE PER MEAL FOR SELECTED ANIMAL-DERIVED FOODS [S43]
a. Seafood (1/5,000,000 chance)
b. Beef (1/200,000 chance)
c. Poultry (1/20,000 chance)
d. Raw molluscan shellfish (1/250 chance)
XLIV. CHART: FOOD BORNE OUTBREAKS ETIOLOGY KNOWN [S44]
a. Many food borne illnesses have an unknown cause.
XLV. TABLE: BACTERIAL FOODBORNE OUTBREAKS IN US 1997-2003 [S45]
a. Breakdown of bacterial causes of diarrhea.
b. Notice that salmonella has the largest amount of outbreaks.
XLVI. BACTERIAL FOOD POISONING [S46]
a. Invasive causes of food poisoning:
1. Salmonella enterica serotypes
2. Salmonella typhi (cause of typhoid fever; rare in the US, yet common elsewhere)
3. Campylobacter jejuni (normal flora in pigs and chicken)
4. Shigella sp
5. Enteroinvasive E. Coli
6. Yersinia enterocolitica (pig borne bacteria)
7. Enterohemorrhagic E. Coli (HUS and O157:H7; found in beef products and some vegetables)
8. Listeria monocytogenes
XLVII. SALMONELLA ENTERIA [S47]
a. There are 2,400 named serotypes of salmonella enterica
b. Physiological characteristics of salmonella:
1. Lactose negative
2. Most H2S positive
c. Salmonella causes three sydromes:
1. Enteric fever – Typhoid fever
a. Systemic disease
b. Gets inside liver and spleen, survives in white blood cells
c. Causes septicimia, blood infections, etc.
d. High mortality rate of 10%
e. Relatively uncommon in the US
2. Enterocolitis – Food poisoning
a. Self-limiting disease
b. Relatively common in the US
3. Bacteremia – Complication of enterocolitis
a. More severe; may lead to death
XLVIII. SALMONELLA ENTEROCOLITIS [S48]
a. Salmonella enterocolitis has 500,000 – 2 million cases/year in the US
b. 2,000 deaths/year
c. $5 million - $1 billion in medical costs in the US
d. Common serotypes of salmonella:
1. S. enterica Typhimurium (found in many “food animals”, like cattle, chicken, etc.)
2. S. enterica Enteritidis (found in eggs)
3. S. enterica Newport (found in cows)
e. Source of infection for salmonella:
1. Water
2. Meat
3. Dairy products
4. Eggs
5. Human carriers working as food handlers
f. Disease characteristics of salmonella:
1. Vomiting (8-48) hours
2. Profuse diarrhea (8-48 hours)
3. Usually resolves in 3-10 days
XLIX. XLD (XYLOSE LYSINE DECARBOXYLASE) PLATE [S49]
a. This picture shows what salmonella looks like on a XLD (xylose lysince decarboxylase) plate
b. Salmonella forms a black colony (sows H2S)
CLASS: 10:00 – 11:00
Scribe: Adam Baird
DATE: October 25, 2010
Proof:
PROFESSOR: Benjamin
Gram-Negative Bacteria
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c. Clear colonies indicates lactose negative
L.
ENTERIC FEVER (TYPHOIC FEVER) [S50]
a. Salmonella enterica Typhi, S. Paratyphi
b. Humans are the only host
c. 200 – 500 cases/year in the US
d. Millions of cases/year worldwide though
e. Mortality
1. <5% in US
2. 10% in third world countries
3. Antibiotic resistance is common in some countries
LI.
TYPHOID VACCINE [S51]
a. There are two typhoid vaccines:
1. Killed Whole S. Typhi
a. Side effects are localized (site of injection swells up, feels warm)
b. Systemic symptoms occur mostly because of lipopolysaccharide
c. 50-94% effective depending on exposure and personal history
2. Live vaccine Ty21a
a. Chemically mutagenized strain
b. Mixed results
c. 60-70% protection
d. Some studies support that there is no protection with this vaccine
b. There is a pill form of this too, which is a capsule with live, dried organisms. Doses taken every other day for
three days. Side effects can vary, just like with the vaccines.
LII.
CAMPYLOBACTER JEJUNI AND C. COLI [S52]
a. Physiological characteristics of campylobacter jejuni and C. Coli:
1. Gram negative
2. Curved rods
3. Oxidase positive
b. Disease characteristics of campylobacter jejuni and C. Coli:
1. 1 – 7 day incubation
2. Fever
3. Bloody diarrhea
4. Abdominal pain
c. More common than salmonella
d. Less severe than salmonella
e. Transmission of campylobacter jejuni and C. Coli:
1. Carried by animals (food animals and pets)
2. Most human infections are from contaminated food or water
3. Raw milk and eggs may be a source of transmission
f. Treatment for campylobacter jejuni and C. Coli:
1. Fluid rehydration
g. Prevention for campylobacter jejuni and C. Coli:
1. Properly preparing and cooking meals
2. Cleanliness
3. Note: College students who may be cooking on their own for the first time may be more susceptible
to campylobacter jejuni and C. coli, simply because they don’t understand the proper ways to
prepare and cook meals.
LIII.
ENTEROHEMORRHAGIC E. COLI (EHEC) [S53]
a. The most common outbreak strain (O157:H7, sorbitol negative)
b. At least 100 other strains have the toxin, but seems to be less virulent
c. Disease characteristics of EHEC:
1. Diarrhea (usually mild)
a. 5 – 10% have hemorrhagic colitis
b. Hemolytic uremic syndrome (HUS)
LIV.
HEMOLYTIC UREMIC SYNDROME (HUS) [S54]
a. Shiga-like toxin, AB5 type of toxin
1. A subunit enzymatic activity that removes an adenosine from 28s rRNA
2. B Subunit targets Gb3, or PK antigen CD77 (activates apoptosis in target cells, endothelial cells, B
cells)
CLASS: 10:00 – 11:00
DATE: October 25, 2010
PROFESSOR: Benjamin
Gram-Negative Bacteria
3. Renal glomeruli contain a high density of Gb3 in infants
b. Disease characteristics of HUS:
1. Acute renal failure
2. Hemolytic anemia
3. Thrombocytopenia (low presence of platelets in blood)
4. 3% mortality rate
c. Not very common, but can be dangerous
LV.
SHIGELLA SPECIES [S55]
a. Closely related to E. Coli
b. Four named “species”
c. Physiological characteristics of shigella:
1. Lactose negative
2. Non-motile
3. No gas formed from glucose
LVI.
BACILLARY DYSENTERY [S56]
a. Oral inoculation
b. 1 – 3 days
c. Disease characteristics of bacillary dysentery:
1. Invades colon epithelium
2. High volume water diarrhea
3. Dysentery (small volume bloody-mucoid stool)
4. Resolves in 2 – 7 days in healthy adults
d. Treatment (supportive) for bacillary dysentery:
1. Ampicillin
2. Bactrim
LVII.
SHIGELLA EPIDEMIOLOGY [S57]
a. Humans are the only host
b. Epidemics occur where sanitation is unsatisfactory:
1. Wars
2. Day care centers
3. Institutions
4. Cruise ships
c. Low infectious dose (200 organisms are considered an infectious dose)
d. 108 CFU/gram of infected stool
e. Causes 15% of pediatric diarrhea in the US
f. 4 F of shigella transmission (mainly fecal-oral)
1. Feces
2. Fingers
3. Food
4. Flies
5. Water
g. Prevention of shigella:
1. Modern sanitary facilitates
2. Hand washing
LVIII. INCIDENCE OF SHIGELLA SPECIES [S58]
a. Chart showing the incidence of shigella species in the US and Mexico.
b. Notice that shigella sonnei is the most common shigella species in the US.
[End 54:57 mins]
Scribe: Adam Baird
Proof:
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