Part 1: Enterobacterales

What characteristics are associated with Enterobacterales?

• gram negative bacilli

• oxidase negative

• facultative

• ferment glucose

• motile

• reduce nitrate - nitrite

What Enterobacterales are NOT MOTILE

• Klebsiella

• Shigella

What Enterobacteriales is the ONLY ONE that is OXIDASE +?

• Plesiomonas

What Antigen is a heat stable oligosaccharide located on the cell wall?

• Somatic O Antigen

What antigen is a heat-labile antigen found on the surface of the flagella?

• H antigen

What antigen is heat labile polysaccaride found only on encapsulated species?

• K antigen

Which E. coli is primarily found in children in developing countries and is the most common cause of travelers diarrhea?

• Enterotoxigenic E. coli

  • spread by food and water

What toxins are produced from Enterotoxigenic E.coli?

• LT (Labile)

  • A fragment: increases cAMP with causes increased secretion

  • B fragment: binds to intestinal mucosa

• ST (Stable)

  • increases cGMP which causes hypersecretion

What symptoms are associated with Enterotoxigenic E.coli?

• watery diarrhea and abdominal cramping

  • treated with hydration

What E.coli invades the epithelial cells lining the intestinal mucosa and is transmitted from contaminated salads and produce?

• Enteroinvasive E. coli

A selected species of E. coli is nonmotile and does not ferment lactose. What kind is it?

• Enteroinvasive

What symptoms are associated with Enteroinvasive E. coli?

• fever

• severe abdominal cramps

• malaise

• watery diarrhea

Trimethoprim-sulfamethoxazole or oral Ciprofloxacin/Levofloxacin are used to treat what illness?

• Enteroinvasive E. coli

What E. coli has attaching and effacing lesions that adhere to erythrocytes and are most commonly seen in children or in hospital nurseries/daycare centers?

• Enteropathogenic E. coli

What symptoms are associated with Enteropathogenic E. coli?

• fever

• malaise

• vomiting

• diarrhea with prominent amount of mucus

  • not bloody

What E.coli is associated with the O157:H7 antigen?

• Enterohemorrhagic (EHEC)

What E.coli causes hemorrhagic diarrhea, and colitis?

• Enterohemorrhagic

What toxins are produced by Enterohemorrhagic E. coli?

• Shiga Toxin (Stx 2)

  • different phage but same action against eukaryotic ribosomes

• Shiga toxin (Stx 1)

  • B subunit: binding to cell

  • A: damages eukaryotic ribosomes

antibody will not neutralize toxin

What E.coli causes Hemolytic uremic symdrome?

• Enterohemorrhagic

How is EHEC spread?

• undercooked hamburger meat

• produce

• processed foods

• unpasteurized dairy

• petting zoos

• fecal -oral

What media definitively identifies EHEC?

• SMAC (MacConkey agar with sorbitol)

  • clear colorless colonies because it does NOT FERMENT SORBITOL

What diagnosis methods are used for EHEC?

• stool culture

  • SMAC

  • MUG testing

  • serotyping for 0157

• molecular detection for stx 1 and stx 2

What is the correct treatment for EHEC?

• supportive only

What E.coli is associated with persistent diarrhea in children and adheres in the intestinal mucosa and has a stacked brick pattern on and between host cells?

• Enteroaggregative E. coli

What E. coli is associated with chronic UTIs and watery diarrhea?

• Diffusely adherent E. coli

What Extraintestinal Infections can occur due to E. coli

• UTIs

  • most common pathogenic clinical isolate recovered from human specimen

• Septicemia

• Meningitis

• Pneumonia

• Wounds

What media selects for E. coli

Eosin methylene Blue

• colonies will be dark green

• colored because it FERMENTS LACTOSE

MacConkey

• pink colonies

• colored because it FERMENTS LACTOSE

Identify this gram negative rod: LF + , ONPG + , Indole + , VP -, and Cit -

• E. coli

A CLSI test that is beta hemolytic, oxidase - , and spot idole + will indicate?

• E. coli

What are the two species of Salmonella?

• S. enterica

• S. bongori

What salmonella is a rare human pathogen isolated from reptiles?

• S. bongori

What are the most common types of Salmonella in the US?

• S. Typhimurium

• S. Enteritidis

How does one acquire salmonella?

• poultry

• eggs

• produce

• cereals

• corn snacks

• pet turtles

What can Salmonella cause?

• gastroenteritis

• Typhoid (enteric) fever

• Septicemia

How does Salmonella cause gastroenteritis

• large dose is needed

• fimbriae are used to adhere and invade intestinal mucosa

• LT-like toxin can cause watery diarrhea

How is gastroenteritis caused by salmonella treated?

• self limiting infection that can be treated with rehydration

What form of salmonella are humans the only known resevoir?

• S. Typhi

What type of salmonella causes typhoid fever?

• S. Typhi

How does one obtain Typhoid fever?

• contaminated food or individuals who are carriers

• organism invades intestin the bloodstream

• gallbladder can serve as long term carrier for organism

What symptoms are associated with Typhoid Fever?

• Initial

  • fever, malaise, lethargy, bacteremia

• Later

  • pneumonia, bowel perforation, meningitis, abscesses, endocarditis

What types of salmonella cause septicemia?

• S. Typhimurium

• S. Choleraesuis

• S. Dublin

What is the only type of Salmonella enterica that does not produce gas from glucose?

• S. Typhi

What stool culture media are used to test for Salmonella?

• HE

• XLD

If a specimen is Salmonella, what will it look like on an HE plate?

• black colonies

  • will utilize the sugar in the agar

If a specimen is Salmonella, what will it look like on an XLD plate?

• red colonies with black center

  • will utilize sugar

What species match these results: ONPG - H2S + LDC + Cit +

• salmonella

How do you differentiate between Shigella and E.coli

• Shigella is nonmotile

How is Shigella transmitted

• humans and primates are only reservoir

• contaminated food or fecal-oral route

What are the four species and serogroups of Shigella?

• A S. dysenteriae

• B S. flexneri

• C S. boydii

• D S. sonnei

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What results indicate Shigella. dysenteriae

Serogroup:A

ONPG: V-

ODC: -

Mannitol: -

What results indicate Shigella. flexerni

Serogroup: B

ONPG: -

ODC: -

Mannitol: +

What results indicate Shigella. boydii

Serogroup: C

ONPG: -

ODC: -

Mannitol: +

What results indicate Shigella. sonnei

Serogroup: D

ONPG: +

ODC: +

Mannitol: +

What type of Shigella is the most severe and can also cause hemolytic uremic syndrome?

• S. dysenteriae type 1

If a Shigella stool culture is plated on an HE plate, what will it look like?

• clear colorless colonies

  • non fermenter so they should be the same color as the plate

If a Shigella stool culture is plated on an XLD, what will it look like?

• colonies should match agar color

  • non fermenter

What type of Yersinia is caused by consuming contaminated pork, causes enterocolitis, resembles appendicitis, and is associated with blood transfusions?

• Y. enterocolitica

What Yersinia is a rare human pathogen caused by close contact with infected animals , infected water or food and causes mesenteric lymphadenitis?

• Y. pseudotuberculosis

What form of Yersinia caused the black death?

• Y. pestis

What type of Yersinia is transmitted to humans by flea bites but has pathogenesis via zoonosis from rats/rodents?

• Y. pestis

What physical symptoms are associated with Y. pestis?

• skin hemorrhage

• lymphadenopathy

• necrosis in extremities

What virulence mechanisms are associated with V. pestis?

• capsule and F1 antigen

  • inhibits phagocytosis

• FIP

• endotoxin

What agar is used to identify Yersinia species?

• cefsulodin-irgasan-novobiocin (CIN) agar with mannitol

What do Yersinia species look like on CIN agar

• colorless colonies with hot pink center

  • colored colonies because of mannitol fermentation

    • incubate at room temp

What strains of Yersinia can be recovered using cold enrichment?

• Y. enterocolitica

• Y. pseudotuberculosis

What features help identify Y. enterocolitica and Y. pseudotuberculosis?

• cold enrichment

  • more active at 25 than 37 C

• motility at RT

• usrease +

What Yersinia is a Tier 1 select antigen?

• Y. pestis

What tests identify Y. pestis?

• Urease -

• indole -

• oxidase -

• nonmotile at RT