Ch. 19 Enterobacteriaceae

Question 1

General Characteristics

Answer 1

• Gram Neg bacilli
• ferment glucose
• oxidase -
• reduce nitrate to nitrite
• colonies = large, gray, wet
• One member is oxidase +
  
  • plesiomonas

Question 2

CRE

Answer 2

• Carbapenum Resistant Enterobacterias
• highly resistant strains
• “super bug”

Question 3

Causes

Answer 3

Common members of GI flora, except primary pathogens

Question 4

Media

Answer 4

• MAC
  
  • lactose fermenters = pink
  • non lactose fermenters = colorless
• HEK
  
  • green
  • blue-green
• EMB
• XLD

Question 5

Primary Pathogens

Answer 5

Salmonella, shigella, yersinia

Question 6

E. coli characteristics

Answer 6

• most common cause of UTI
• common throughout lab
• member of GI flora
• IMVC = ++–

Question 7

Enteropathogenic (EPEC)

Answer 7

• infant diarrhea
• stools have mucous, no blood

Question 8

Enterotoxigenic (ETEC)

Answer 8

• Travelers diarrhea
• stools are watery, no blood

Question 9

Enteroinvasive (EIEC)

Answer 9

• Large outbreaks
• fecal oral route
• stools are watery with blood, WBCs and mucous
• similar to shigella in symptoms

Question 10

Enterohemorrhagic (EHEC)

Answer 10

• serotype O157:H7
• watery, bloody stool, without WBCs
• can be fatal
  
  • esp in children/elderly
• intestinal lining sloughs off
  
  • leaving ulcers
• transmitted by undercooked meats, veggies contaminated with feces
• produce shiga toxins

Question 11

Enteroadherent (EAEC)

Answer 11

• adheres to mucosal surface
• watery diarrhea lasting 2+ weeks

Question 12

Klebsiella characteristics

Answer 12

• K. pneumoniae, K. oxytoca are most common
• colonies = large, gray, mucoid
• has capsule
• K. pneumo from respiratory sites, wounds, UTIs
• IMVC = –++

Question 13

CRK

Answer 13

• Carbapenum resistant klebsiella
• highly resistant strains of klebsiella

Question 14

Proteus characteristics

Answer 14

• P. mirabilis
  
  • indole -
  • ODC +
• P. vulgaris
  
  • indole +
  • ODC -
• hyperflagella allows swarming
• UTIs, wounds, blood

Question 15

Enterobacter

Answer 15

• E. cloacae
• appears similar to kleb

Question 16

Serratia

Answer 16

• S. marcescens
• red pigment
• nosocomial UTIs, nurseries, burn units

Question 17

Providencia

Answer 17

• P. stuartii
• nosocomial in burn units

Question 18

Citrobacter

Answer 18

• C. freundi
• nosocomial UTIs, pneumonias

Question 19

Salmonella General

Answer 19

• produces enterotoxins that cause
  
  • gastroenteritis
  • vomiting
  • diarrhea
  • nausea

Question 20

Salmonella Causes

Answer 20

• undercooked poultry
• meat
• eggs
• turtles
• reptile pets

Question 21

Salmonella disease course

Answer 21

• invades intestinal lining cells
• spreads to lymph nodes
• blood stream
  
  • causing enteric fever
• spleen
• liver
• bone marrow
• causes rose spots on abdomen
• can reach gallbladder and develop carrier state
  
  • “typhoid mary”

Question 22

Salmonella Testing

Answer 22

• H and O antigens used for serotyping
• produces H2S
  
  • black colonies on HEK, TSI
• produces gas
• S. typhi
  
  • causes typoid fever
  • posesses Vi antigen
• S. paratyphi
• S. choleraesuis

Question 23

Shigella Characteristics

Answer 23

• causes dysentery with fever, chills
• invades mucosal lining cells
  
  • then sheds lining with ulcers forming
• stools are bloody with mucous
• no animal reservoir
  
  • only infects humans
• spread person to person by 4 F’s
  
  • fingers, food, flies, feces
• produce Shiga toxin

Question 24

Shigella Testing

Answer 24

• No H2S
• No gas
• Use latex antigen tests for serotyping
• S. dysenteriae
  
  • most serious
• S. sonnei
  
  • most common type in US
• S. felxneri
  
  • second most common

Question 25

Yersinia General

Answer 25

CIN agar selects for yersinia

Question 26

Y. pestis characteristics

Answer 26

* causes black plague * transmitted by flea bits * usually on rodents * found recently in "four corners" area in SW US

Question 27

**Y. pestis** : Bubonic

Answer 27

* from direct flea bite * from blood stream infects lymph nodes and causes buboes * redended or black pustules * 60% mortality rate if untreated * killed around 60% of europe in middle ages

Question 28

**Y. pestis** : Pneumonic

Answer 28

* form is secondary to bubonic * goes from blood to lungs * spread by droplets * about 90-95% fatal if untreated * antibiotics do work if treated in time

Question 29

**Y. pestis** : Septicemic

Answer 29

* form is rare * 99-100 % fatal if untreated * considered class A bioterrorism weapon * first bioweapon used in ancient times * gram stain shows intense bipolar staining * "safety pin"

Question 30

Y. enterocolitica

Answer 30

* most common species * enteritis with fever, nausea, abdominal pain, diarrhea may be bloody * arthritis may follow * may see red nodules under skin, esp on shins, with itching and burning * from pigs, pork, pets * survives refrigeration * motile at room temp

Question 31

Y. pseudotuberculosis

Answer 31

* from rodents, guinea pigs, turkeys, geese, pigeons * rare in humans but causes lymphadenopathy, septicemia