Enterbacteriaecea

Question 1

What type of bacteria are all members of Enterobacterales?

Answer 1

Gram negative bacilli

Question 2

Are Enterobacterales anaerobic or aerobic?

Answer 2

Facultatively anaerobic

Question 3

What are the common characteristics shared by all species in Enterobacterales?

Answer 3

• All ferment glucose
• All reduce nitrates to nitrites
• Oxidase negative
• All except Klebsiella, Shigella, and Yersinia are motile

Question 4

What types of media are used for the presumptive identification of Enterobacterales?

Answer 4

• MacConkey agar
• Hektoen enteric (HE) agar
• XLD (xylose-lysine deoxycholate agar)

Question 5

What antigenic factors are useful for identifying different serogroups of Enterobacterales?

Answer 5

• O antigen
• H antigen
• K antigen

Question 6

Where are Enterobacterales commonly found in nature?

Answer 6

In the gastrointestinal tract of humans and animals as normal flora

Question 7

How are Enterobacterales classified in terms of pathogenicity?

Answer 7

• Opportunistic pathogens
• Primary intestinal pathogens

Question 8

Which organisms are considered true intestinal pathogens in the Enterobacterales family?

Answer 8

• Salmonella spp.
• Shigella spp.
• Yersinia enterocolitica

Question 9

Which Klebsiella species is known for causing urinary tract infections and respiratory infections in hospitals?

Answer 9

Klebsiella oxytoca

Question 10

What key characteristic differentiates Klebsiella species from other Enterobacteriaceae?

Answer 10

Absence of motility

Question 11

What is the significance of the polysaccharide capsule in Klebsiella pneumoniae?

Answer 11

Contributes to the virulence of the organism

Question 12

What genera are included in the Enterobacterales opportunistic members of the family?

Answer 12

• Klebsiella
• Enterobacter
• Serratia

Question 13

What unique feature do Serratia species possess compared to other Enterobacteriaceae?

Answer 13

Produce extracellular DNase

Question 14

What infections are associated with Serratia marcescens?

Answer 14

• Hospital-acquired UTIs
• Respiratory infections

Question 15

What distinguishes Proteus species in Enterobacterales?

Answer 15

Ability to deaminate phenylalanine

Question 16

What is a common characteristic feature of Proteus mirabilis and Proteus vulgaris on media?

Answer 16

Distinctive swarming colonies

Question 17

What is the clinical significance of Morganella morganii?

Answer 17

Causes nosocomial infections and UTIs

Question 18

Which species of Providencia is known for causing UTIs and outbreaks in burn units?

Answer 18

Providencia stuartii

Question 19

What is a key differentiating feature of Citrobacter species?

Answer 19

Most hydrolyze urea slowly and ferment lactose

Question 20

What are the distinguishing tests for Salmonella and Citrobacter?

Answer 20

Lysine decarboxylase test

Question 21

Fill in the blank: Klebsiella pneumoniae is a common cause of ______ in hospitalized patients.

Answer 21

lower respiratory tract infections

Question 22

True or False: All Enterobacterales are lactose fermenters.

Answer 22

False

Question 23

What is the typical odor produced by Proteus mirabilis and Proteus vulgaris?

Answer 23

Burned chocolate

Question 24

What are the common sources of Salmonella infection?

Answer 24

Contaminated animal products, undercooked poultry, milk, eggs, dairy products

Ingestion is the primary route of infection.

Question 25

What are the biochemical features of Salmonella?

Answer 25

* Do not ferment lactose * Negative for indole * Negative for Vogues-Proskauer test * Negative for phenylalanine * Negative for urease * Most produce H2S on TSI * Positive for methyl red and citrate ## Footnote These characteristics help in identification.

Question 26

What are the main antigens used for the serologic diagnosis of Salmonella?

Answer 26

Somatic O antigen and flagellar H antigen ## Footnote Serologic grouping of the Vi antigen is used to identify S. typhi.

Question 27

What are the two forms of plague caused by Yersinia pestis?

Answer 27

* Bubonic plague * Pneumonic plague ## Footnote Bubonic plague is the primary illness; pneumonic is a secondary disease.

Question 28

What is the main characteristic of Shigella species?

Answer 28

Causes bacillary dysentery ## Footnote All species are not part of the normal bowel flora.

Question 29

What are the four species of Shigella?

Answer 29

* Shigella dysenteriae (group A) * Shigella flexneri (group B) * Shigella boydii (group C) * Shigella sonnei (group D) ## Footnote Different O antigens are used for serologic identification.

Question 30

What is a key characteristic of Escherichia coli?

Answer 30

Commonly isolated from the normal bowel flora ## Footnote Recognized as an important human pathogen.

Question 31

What infections can E. coli cause?

Answer 31

* Meningitis (particularly in newborns) * Gastrointestinal infections ## Footnote Some strains have virulence factors that can cause diarrhea.

Question 32

What is a significant biochemical test result for E. coli?

Answer 32

Positive indole and methyl red tests ## Footnote E. coli does not produce H2S, DNase, urease, or phenylalanine deaminase.

Question 33

Fill in the blank: The causative agent of the bubonic plague is ______.

Answer 33

[Yersinia pestis]

Question 34

True or False: Salmonella species can ferment lactose.

Answer 34

False ## Footnote Salmonella species do not ferment lactose.

Question 35

What types of infections can Escherichia coli cause?

Answer 35

* Meningitis * Gastrointestinal illness * Urinary tract infections (UTI) * Wound infections * Bacteremia ## Footnote Particularly notable in newborns for meningitis and in adults for UTIs.

Question 36

What are the different types of diarrheagenic E. coli?

Answer 36

* Enteropathogenic (EPEC) * Enterotoxigenic (ETEC) * Enteroinvasive (EIEC) * Enterohemorrhagic (EHEC) * Enteroaggregative (EaggEC) ## Footnote Each type is associated with different clinical presentations and mechanisms of infection.

Question 37

Where is Enterotoxigenic E. coli (ETEC) commonly acquired?

Answer 37

Via ingestion of contaminated food or water ## Footnote ETEC is particularly prevalent in tropical and subtropical climates.

Question 38

What characterizes the diarrhea caused by Enteroinvasive E. coli (EIEC)?

Answer 38

It is similar to dysentery caused by Shigella ## Footnote Symptoms include fever, severe abdominal cramps, and diarrhea that may contain pus, mucus, and blood.

Question 39

What is the primary strain of Enterohemorrhagic E. coli (EHEC) responsible for serious infections?

Answer 39

E. coli O157:H7 ## Footnote This strain can cause hemorrhagic colitis and hemolytic uremic syndrome.

Question 40

How can E. coli O157:H7 be identified in the laboratory?

Answer 40

* Stool culture on MacConkey agar containing sorbitol * Latex agglutination test * MUG assay ## Footnote E. coli O157:H7 does not ferment sorbitol, resulting in colorless colonies on specific agar.

Question 41

What is the most common cause of urinary tract infections (UTI)?

Answer 41

Escherichia coli ## Footnote These strains are often resident or transient members of the normal colon flora.

Question 42

What is the significance of fecal leukocytes in diagnosing bacterial infections?

Answer 42

As few as 3 neutrophils per high-power field may indicate an invasive bacterial infection ## Footnote This can differentiate from intoxication or parasitic infections.

Question 43

What is the procedure for serogrouping Salmonella?

Answer 43

* Emulsify a pure culture in saline * Add antisera and bacterial emulsion * Heat and test for agglutination ## Footnote This process helps confirm the biochemical test identification.