Enterobacter

Question 1

Overt Pathogens

4

Answer 1

• Salmonella
• Shigella
• Yersinia
• E. coli

Question 2

Subtypes of E. Coli

2

Answer 2

• Enterotoxigenic (ETEC)
• Enterohemorrhagic (EHEC)

Question 3

General Characteristics of Overt Pathogens

Type and virulence

Answer 3

Type: rapid growers, facultative anaerobes
Virulence: lipopolysaccharides

Question 4

Major Lipopolysaccharides

3

Answer 4

Outermost somatic O polysaccharide: epidemiologic classification of strains within species
Core polysaccharide: commen antigen
Lipid A: endotoxin

Question 5

Epidemiologic Classification

3

Answer 5

• Somatic O polysaccharide
• Capsular K/Vi antigen: heat labile, interferes with O detection
• Flagellar H antigen: heat labile

Question 6

Common Virulence Factors

5

Answer 6

• Capsule: protects from phagocytes
• Antimicrobial resistance
• Endotoxin, lipid A
• Antigenic phase variation
• Type III secretion systems: molecular syringe, delivers virulence factors to target cells

Question 7

Escherichia Coli Basics

Trans, clinical, virulence

Answer 7

Transmission: endogenous, gastroenteritis is from exogenous
Clinical: UTI, extraintestinal, GI tract infections
Virulence: general ones, adhesions, exotoxins

Question 8

Escherichia Coli (ESCO) Infection: UTI

how does it infect, main symptom, establishment

Answer 8

Most common cause
- Adheres to epi cells, doesn’t wash away when you pee

Symptoms: delirium is a big one

Establishment: catheters, pregnancy, hemolysin promotes cell lysis and forms biofilms, gender (longer urethra)

Question 9

ESCO Infection: Extraintestinal

2 types

Answer 9

Neonatal meningitis: major cause of CNS infections in infants <1 y/o
- K capsular antigen
- Common GI commensal

Septicemia
- Originate from UTI or GI infection

Question 10

E. Coli: Enterotoxigenic Infection

Disease, symptoms,treatment

Answer 10

Traveler’s diarrhea: most common cause
- Foodborne outbreaks
- Children at risk

Symptoms: nausea, fever, diarrhea, maybe vomiting
- 3-5 days

Treat with supportive care without antibiotics

Question 11

E. Coli: Enterhemorrhagic (EHEC) Basics

Trans, clinical, virulence

Answer 11

Transmission: eating undercooked ground beef, raw milk, animal fecal contam.
Clinical: hemorrhagic colitis, hemolytic uremic syndrome
Virulence: toxins like Shiga toxin

Question 12

E. Coli: Enterohemorrhagic (EHEC) Infection

2 diseases, antibiotics?

Answer 12

Hemorrhagic colitis: stomach cramps, bloody diarrhea
Hemolytic uremic syndrome: kidney damage

Antibiotics don’t always help, can increase HUS risk

Question 13

E. Coli Enterohemorrhagic Serotypes

Answer 13

Major O serotype: O157

Question 14

Establishment of GI Infections

4

Answer 14

Anatomic alterations: obstruction of secretion flow, stuff gets stuck

Changes in stomach acidity: shigella and escherichia are acid resistant

Normal flora alterations: broad spectrum antibiotics

Encounter with specific pathogenic agents: infectious dose must be reached

Question 15

Citrobacter, Enterbacter, Klebsiella, Morganella, Proteus, Serratia: Basics

Where, trans, clinical

Answer 15

Where: normal GI flora
Tranmission: endogenous, person to person
Clinical: opportunistic and nosocomial infections

Question 16

Other Infections: Klebsiella Pneumoniae

Answer 16

Community/nosocomial: pneumonia
- Capsule, adhesins

Question 17

Other Infections: Proteus spp.

Answer 17

UTI with or without kidney stones
- Biofilm, adhesins, proteases

Question 18

Other Infections: Citrobacter Koseri

Answer 18

Meningitis, brain abscesses in neonates

Question 19

Other Infections: Enterobacter/Cronobacter

For both

Answer 19

Enterobacter: various nosocomial like UTI
Cronobacter: meningitis/sepsis in newborns

Question 20

Other Infections: Serratia, Morganella

Answer 20

Both cause various nosocomial infections

Question 21

Salmonella Basics

where, trans, clinical

Answer 21

Where: typhi and paratyphi in humans, not normal flora
Transmission: person to person, fecal oral, contaminated food
Clinical: gastroenteritis, typhoid fever

Question 22

Salmonella Virulence

and pathogenesis

Answer 22

Can traverse intestinal mucosa

Pathogenesis:
- Ingest microbe, absorb into epi cells in intestines
- Penetrates cells and multiply
- Stimulation of cAMP and fluid secretion from host immune response

Question 23

Salmonella Infections

two, treatment

Answer 23

Gastroenteritis: acid sensitive, vomiting, nausea, diarrhea, can recover without treatment, caused by foods, 4-7 day duration

Enteric fever: typhi or paratyphi, typhoid fever, pain and diarrhea, 4 week duration w some relapse

S. typhi has a vaccine

Question 24

Shigella: Basics

where, trans, clinical, virulence

Answer 24

Where: human host specific, not normal flora
Transmission: fecal oral
Clinical: diarrhea, pediatric disease
Virulence: traverse intestinal mucosa
- S. dysenteriae has an exotoxin

Question 25

Shigella: Species ## Footnote 4 and grouping

Answer 25

1. S. sonnei, Group D, most common 2. S. flexneri, Group B, more severe 3. S. boydii, Group C, more severe 4. S. dysenteriae, Group A, most serious

Question 26

Shigella: Infections ## Footnote symptoms, recovery, risks

Answer 26

**Shigellosis** - Short incubation - Low dose - Watery diarrhea, becomes bloody/mucus, cramps, fever - 1 week duration **Recovery:** often without treatment, immunocompromised may get antimicrobials **Risk:** poor hygiene, child care, janitors, mlm

Question 27

Yersinia: Basics ## Footnote 3 species, where for each, trans, significance

Answer 27

**Y. pestis:** rats, rodents, flea vector | ingestion or inhalation of tissue or airborne droplets | bubonic plague, pneumonic plague **Y. enterocolitica:** dogs, cats, rodents, rabbits, pigs, cattle | consumptopn of contaminated food, contact with contam. animal | enterocolitis, pseudoappendicitis **Y. psudotuberculosis:** birds, deer, rodents: same as above

Question 28

Yersinia Pestis: Virulence Factors

Answer 28

**Plasmids that encounde virulence genes**' - **pPCP1:** **bacteriocin** **that kills other bacteria** and activates plasminogen, degrades complement and prevents opsonization and phagocytic migration - ***allows for deep tissue invasion*** - **pMT1:** murine toxin that **enhances survival in the flea gut**, F1 capsular antigen

Question 29

Yersinia Pestis: Infections ## Footnote 2 of them

Answer 29

**Bubonic plague** - 1 wk incubation - Fever, swelling of lymph node, bacteremia without treatment, 75% mortality **Pneumonic plague** - 2-3 day incubation - Fever, malaise, pulmonary symptoms - Person to person spread possible, highly infectious - Mortality rate 90% without treatment

Question 30

Other Yersinia Infections

Answer 30

**Enterocolitis** - Fever, pain, diarrhea (maybe bloody), vomiting - Lasts up to 2 weeks - Meats, oysters, fish, raw milk **Pseudoappendicitis:** from abdominal pain of lower right quadrant, thinks its appendix problem **Extraintestinal:** arthritis

Question 31

Plesiomonas Shigelloides: Basics ## Footnote where, trans, clinical

Answer 31

,**Where:** soil, freshwater, warm and cold blood animals **Transmission:** contaminated food or water, reptile exposure **Clinical:** **gastroenteritis** (watery or secretory diarrhea, can be chronic for months even) or **opportunistic sytemic** (meningitis, bacteremia)

Question 32

Salmonella: Serotyping

Answer 32

- Somatic O - Surface Vi - Phase 1 or phase 2 flagellar (H antigen)