17 Sal/Vib Flashcards by Katelynn Davis

Why are vibrio organisms separated from enterobacteriaciae?

They display positive oxidase and have polar flagella

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What type of flagella do E. Coli have?

peritrichous

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Is Ecoli oxidase positive?

no, negative

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Out of the 60 vibrio species, what are the 3 important ones?

V. cholerae
V. parahaemolyticus
V. vulnificus

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Which vibrio species is the cause of great human morbidity and mortality through pandemic disease?

cholerae

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What vibrio species causes gastroenteritis, wound infection, and bacteremia?

parahaemolyticus

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What is the more invasive vibrio species?

vulnificus

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What does v. vulnificus cause? 4

severe diarrhea
septicemia
life threatening cellulitis
wound infection

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Who are at risk to v. vulnificus?

renal insufficiency
liver disease
alcoholism

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Vibrio growth on what plate distinguishes vibrios?
Why is cholerae different? color?
What are the other colors?

Thiosulfate Citrate Bile Sucrose - TCBS
Cholerae ferments sucrose and forms yellow colonies.

parahaemolyticus and vulnificus are green

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How does vibrio appear on blood agar? (initially and later)

Initially surrounded by zone go greening, later the zone is clear due to hemodigestion

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What vibrio has enzymes to digest shellfish shell? When do we see this?

V. cholerae

Warm weather–> algal blooms–>copepods–> disease

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Which vibrio can grow in +/- salt?

V. Cholerae

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True or false– vibrio pathogens die in salt?

False–they are halophilic and require salt

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What is responsible for inserting the enterotoxin gene into v cholerae and is responsible for cholera?

a phage called CTX

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How many o type antigens for v. cholerae?

Which ones are associated with cholera toxin pandemics?

2. Only O1 and O139

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What are the 3 serotypes and 2 biotypes of the O1 serogroup?

sero-Inaba, Ogawa and Hikojima

bio-Classical and El Tor

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What biotype was responsible for first 6 cholera pandemics? What about 7? What about the current epidemic 8 ?

1-6=Classical
7= El Tor
8=O139

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Why is no protected immunity conferred in cholera?

adults pref. infected with O1 are now infected with O139

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T-F–O1 - classical biotype is extinct?

True- this is why people have cholera today are infected with O139 or El Tor

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How long after ingestion of bacteria does abrupt onset of watery diarrhea and vomiting in cholera? what happens after more fluid is lost? How much fluid can they lose?

2-3 days
stool becomes odorless, colorless, free of protein and speckled with mucous
1 liter of fluid per hour (50% weight loss)

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Why isn’t cholerae flushed out with all the diarrhea?

TCP–adheres to mucosal cell layer by means of the toxin co-regulated pious (TCP)

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T-F–cholera disease can progress to severe dehydration, muscle cramps, and metabolic alkalosis?

False–metabolic acidosis but others are correct

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T-F–cholera disease progresses to hypokalemia, hypovolemic shock and renal failure?

True

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What are good signs of dehydration in cholera?

sunken eyes, flaccid skin, washerwoman's hands

What type of fever and WBC in stool do we see in cholera?

No fever | No WBC in stool

What is the mortality rate in untreated cholera patients? how is it decreased?

60%--fluid and electrolytes

What type of exotoxin is cholera toxin?

A-B type exotoxin

What receptor does the cholera toxin bind to?

GM1 ganglioside

The A subunit of cholera toxin does what?

interacts with and ADP-ribosylates host G proteins-->act. adenylate cyclase-->high cAMP--> promote secretion of fluid in epithelium

What is the best prevention of cholera?

drinking water that is free of V. cholerae

What is the drug of choice for cholera?

azithromycin-can reduce toxin production

What belongs to the same family as vibrio, found in fresh and brackish water, causes two types of gastroenteritis (one like cholera and one like dysentery)? Does it produce cholera toxin?

1. Aeromonas hydrophila | 2. Does not produce cholera toxin (little known about virulence factors)

does Enterobacteriaceae only cause intestinal infections?

No, intestinal and extra-intestinal

Enterobacteriaceae causes what % of septicemia cases, % of UTIs?

30-35% | 70%-(Ecoli is major here)

What are the traits shared by enterobacteriaceae-- | 1. gram?, 2. anaerobe or aerobe?, 3. catalase? 4. oxidase? 5. ferment? 6. bile growth on MacConkey?

1. gram neg rods 2. facultatively anaerobic 3. catalase positive 4. oxidase negative 5. ferment glucose 6. growth in bile

What is the key to identifying enterobacteriaceae class?

fermenting lactose-- known as coliforms

True-False-- salmonella, shigella, and proteus are lactose positive?

False

Is serratia marcescens lactose postive?

yes

Is enterobacter cloacae lactose postive?

Yes

How is transmission of the enterobacteriaceae conferred? 3

1. fecal oral 2. consumption of contaminated food/H2O 3. Direct contact

H antigens come from what on enterics?

Flagella, protein..only on motile strains!

K antigens come from what on enterics>

capsule, polysaccharides

What are the 4 possible surface characteristics for identifying enterics?

O, H and K antigens | Pili

T-F-- if a bacterium has all 4 antigens and variability exists in each there is only a single serotype?

False- an enormous serotype diversity

What are the 3 general types of virulence factors of enterobacteriaceae?

1. organism associated (LPS, capsule, pili) 2. extracellular (exotoxins, siderophores) 3. secreted effector proteins (alter host metal)

T-F-- Klebsiella and proteus are opportunistic pathogens?

True

T-F--salmonella and shigella are opportunistic pathogens?

False- primary human pathogens

What is the difference between exogenous and endogenous infections?

exogenous is not derived from the normal gut flora and endogenous is derived from the normal gut flora

What are the 3 exogenously acquired diseases caused by enterobacteriaceae?

1. disease due to infection of small intestine 2. disease of large intestine 3. disease of the kidney following bacterial expression of toxins in large intestine 4. extraintestinal infection (UTI, neonate meningitis)

What does salmonella look like on MacConkey lactose agar? what about Hektoen-Enteric Agar?

1. pale on macconkey | 2. Blue colonies with black centers

T-F--salmonella has polar flagella?

False-peritrichously

Is salmonella resistant to bile salts? | What does salmonella produce?

Yes | H2S

How many serotypes for salmonella? How many species?

>2500 | 1 species- Salmonella enterica

What is the main salmonella reservoir for infection?

poultry products (most common isolations from reptiles, birds, and various mammals)

What salmonella strain is a strict human pathogen and healthy carriers are the only reservoir for this type?

S. enterica serovar Typhi

What are the 3 diseases due to salmonella enterica?

1. gastroenteritis 2. Septicemia (following gastroenteritis in predisposed) 3. Enteric Fever (typhoid and paratypohoid)

Where is asymptomatic carriage of enteric fever (typhoid) found?

gall bladder

Invasion of what is necessary to all diseases of salmonella?

small intestines through M cells

Where does the salmonella bacteria reproduce?

intracellularly in endocytic vesicles

Invasion of salmonella causes what in intestinal epithelium? leads to what?

necrosis--> severe non-bloody diarrhea, nause and vomiting

Is salmonellosis self limiting? why?

Yes after 3-5 days, due to production of phagocytes (host recovers in 2-7 days)

21.5 million S. typhi cases and 600,000 deaths worldwide occur…how many in US?

400 and 70% of those are from travel

What is the incubation period of S. typhi? Invasion through GI and lymphatics leads to what? Symptoms?

1. 14 days 2. systemic infection 3. high fever, malaise, myalgias

T-F--the S. typhi bacteria invade the GI tract, but not killed by phagocytes?

True- leads to dissemination

What is the only salmonella serotype to produce a capsule?

S. typhi (Vi antigen)

T-F--genes allowing invasion of S. typhi bacteria in the GI and in the blood are very close together on chromosome?

False- 2 distinct regions

What are the 3 virulence factors of S. typhi?

LPS pili invasiveness

Salmonella pathogenicity island I (SPI1) does what? SPI2?

``` SPI1= allow invasion in non-phagocytes SPI2= allow replication in phagocytes ```

Antibiotics therapy is only appropriate for S. enteric infections in what 2 incidences?

1. populations at risk for disseminated salmonella subsequent to gastroenteritis (young children) 2. typhoid fever infections

Vaccines of salmonella enterica are of what type?

live attenuated or Vi capsule vaccine | other prevention method is sanitation and proper cooking