L9: GNB 2 - Salmonella, Shigella, Helicobacter

Question 1

List some of the characteristics of the salmonella species

Answer 1

gram negative bacilli
NON-lactose fermenter
BLACK colonies on XLD (due to hydrogen sulphide - H2S - production) 
facultative anaerobes
peritrichous flagellae

Question 2

What is the tranmission methods for enteric fever (typhoidal fever)?

Answer 2

faecal-oral route

person to person (by chronic carrier)

Question 3

What is the incubation period for enteric fever?

Answer 3

7-21 days (up to 30 days)

Question 4

What occurs in the 1st stage/1st week of enteric fever (typhoidal fever)?

Answer 4

• body temp. rises gradually
• headache
• relative bradycardia
• constipation OR diarrhea

Question 5

What occurs in the 2nd stage/2nd week of enteric fever (typhoidal fever)?

Answer 5

• fever persists
• abdominal distension/splenomegaly
• “pea-soup” diarrhea
• confusion/altered mental state
• Rose Spots

Question 6

What are Rose Spots?

Answer 6

• occur in 2nd stage/2nd week of enteric fever
• salmon-coloured, blanching, maculopapules
• resolves within 2-5 days
• bacterial emboli to the dermis

Question 7

What occurs in the 3rd stage/3rd week of enteric fever (typhoidal fever)?

Answer 7

hepatic, renal + bone marrow dysfunction
abdominal distension/perforation/peritonitis/secondary bacteraemia
osteomyelitis
relapse (esp. if treatment inadequate)

Question 8

What occurs in the 4th stage/4th week of enteric fever (typhoidal fever)?

Answer 8

fever, mental state + abdominal distension improves
intestinal complications
weight loss + debilitating weakness for months

Question 9

A person may be a chronic carrier of S. typhi. What is the definition of chronic carriage? What does this mean?

Answer 9

positive stool cultures 12 months AFTER overcoming the disease

• potential to transmit S. typhi indefinitely
• usually asymptomatic

Question 10

What is the treatment for an individual that is a chronic carrier of S. typhi?

Answer 10

Ciprofloxacin (for at least 1 month)

Question 11

How does Paratyphoid A typically present?

Answer 11

similar to typhoid but less severe

rarely see rose spots

Question 12

How does Paratyphoid B typically present?

Answer 12

usually a diarrheal illness

Question 13

How can enteric fever be diagnosed in the 1ST WEEK?

Answer 13

via blood culture (80% in 1st week)

Question 14

How can enteric fever be diagnosed in the 2ND WEEK onward?

Answer 14

via faeces culture

Question 15

How can enteric fever be diagnosed in the 3RD WEEK onward?

Answer 15

via urine culture

Question 16

What is the treatment for enteric fever?

Answer 16

1. Fluid & Electrolyte Replacement + Supportive Management
2. Antibiotics (for 10-14 days)
   - - Ceftriaxone is the empiric treatment

Question 17

What is the empiric antibiotic given to treat enteric fever?

Answer 17

Ceftriaxone (after susceptibilities - Ciprofloxacin, Azithromycin)

Question 18

What vaccines maay be given to individuals to prevent enteric fever?

Answer 18

• Subunit Vacine (Vi polysaccharide)

- Live attenuated oral vaccine

Question 19

What is the source/reservoir of salmonella gastoenteritis?

Answer 19

reptiles and environment (e.g. turtles, hedgehogs…)

Question 20

What are the main transmission methods for salmonella gastroenteritis?

Answer 20

foodborne (chicken, beef, unpasteurized milk…)

faecal-oral

Question 21

What is the incubation period for salmonella gastroenteritis?

Answer 21

18 to 72 hours

Question 22

Virulent strains of salmonella can induce multiple host inflammatory responses and cytokines - this is mediated by what?

Answer 22

the lipopolysaccharide in the cell wall

Question 23

What is the clinical features/presentation of salmonella gastroenteritis?

Answer 23

self-limiting (usually lasts 3-7 days)
diarrhea, nausea, headache, malaise
dehydration* (in extremes of age, immunocompromised)

Question 24

Salmonella gastroenteritis may be chronically excreted for up to 4 weeks. What 4 things may increase and prolong excretion?

Answer 24

• antibiotics
• HIV
• inflammatory bowel disease
• diverticulosis

Question 25

List the complications of non-typhoidal salmonella (salmonella gastroenteritis)

Answer 25

BSI systemic disease (osteomyelitis, meningitis) reactive arthritis

Question 26

What is the treatment for salmonella gastroenteritis?

Answer 26

1. Fluid & Electrolyte Replacement + Supportive Management 2. NO Antibiotics (unless <12 months, >50, immunocompromised or have cardiac, valvular, endovascular abnormalities or joint disease)

Question 27

What is the Vi antigen?

Answer 27

a/w Salmonella serotyping is the virulence antigen a specialized K antigen primarily found in strains of salmonella causing typhoid fever

Question 28

List some of the characteristics of the Shigella species

Answer 28

gram negative bacilli NON-lactose fermenter COLOURLESS colonies on XLD agar

Question 29

List the 4 serological groups of shigella and name it

Answer 29

Group A - S. dysenteriae Group B - S. flexneri Group C - S. boydii Group D - S. sonnei

Question 30

Which serological group of shigella is most common in tropical countries? (hint: also most severe form)

Answer 30

Group A - S. dysenteriae

Question 31

What is the most commony serological group of shigella in the UK/Ireland?

Answer 31

Group D - S. sonnei

Question 32

Which strain of shigella expresses the shiga toxin?

Answer 32

S. dysenteriae serotype 1

Question 33

What are the 2 types of toxins a/w shigella?

Answer 33

1. Enterotoxins | 2. Shiga Toxin

Question 34

What are the main transmission methods of Shigella?

Answer 34

faecal-oral foodborne contaminated water

Question 35

What is the incubation period of Shigella?

Answer 35

24 to 72 hours (relatively slow)

Question 36

What are the 2 main clinical features/presentations of Shigella dependent on what type of shigella strain is involved?

Answer 36

1. Profuse, Watery Diarrhea | 2. Dysentery

Question 37

List the complications of Shigella

Answer 37

- intestinal complications (toxic megacolon, perforation, obstruction) - BSI - convulsions - reactive arthritis - HUS

Question 38

What sample may be taken to help in the diagnosis of shigella? What investigation/test can be done?

Answer 38

Faeces Sample | - PCR or Culture

Question 39

What is the treatment/management plan for shigella?

Answer 39

1. Fluid & Electrolyte Replacement + Supportive Management 2. Rarely Antibiotics (unless S. dysenteriae) - - Ceftriaxone/Ciprofloxacin

Question 40

If antibiotics are required for a shigella infection, which ones would be given empirically?

Answer 40

Ceftriaxone or Ciprofloxacin

Question 41

List some of the characteristics of H. pylori

Answer 41

curved gram negative bacilli asymptomatic coloniser of stomach causes gastrititis + duodenal ulcers

Question 42

What are the virulence factors for H. pylori?

Answer 42

- urease production - motility (spiral shape, flagella, mucolytic enzymes) - adheres to gastric epithelium

Question 43

Cancer may be a complication of H. pylori infection and gastritis that consequently arises. What specific cancer may occur?

Answer 43

Gastric Cancer - Adenocarcinoma** | also MALT lymphoma and other GI cancers

Question 44

How may H. pylori be detected? What investigations/tests may be done?

Answer 44

1. Laboratory Testing - Faecal Antigen Testing, Serology... 2. Endoscopy Biopsy - CLO Test, Histology... 3. Urea Breath Test