L9: GNB 2 - Salmonella, Shigella, Helicobacter Flashcards
List some of the characteristics of the salmonella species
gram negative bacilli NON-lactose fermenter BLACK colonies on XLD (due to hydrogen sulphide - H2S - production) facultative anaerobes peritrichous flagellae
What is the tranmission methods for enteric fever (typhoidal fever)?
faecal-oral route
person to person (by chronic carrier)
What is the incubation period for enteric fever?
7-21 days (up to 30 days)
What occurs in the 1st stage/1st week of enteric fever (typhoidal fever)?
- body temp. rises gradually
- headache
- relative bradycardia
- constipation OR diarrhea
What occurs in the 2nd stage/2nd week of enteric fever (typhoidal fever)?
- fever persists
- abdominal distension/splenomegaly
- “pea-soup” diarrhea
- confusion/altered mental state
- Rose Spots
What are Rose Spots?
- occur in 2nd stage/2nd week of enteric fever
- salmon-coloured, blanching, maculopapules
- resolves within 2-5 days
- bacterial emboli to the dermis
What occurs in the 3rd stage/3rd week of enteric fever (typhoidal fever)?
hepatic, renal + bone marrow dysfunction
abdominal distension/perforation/peritonitis/secondary bacteraemia
osteomyelitis
relapse (esp. if treatment inadequate)
What occurs in the 4th stage/4th week of enteric fever (typhoidal fever)?
fever, mental state + abdominal distension improves
intestinal complications
weight loss + debilitating weakness for months
A person may be a chronic carrier of S. typhi. What is the definition of chronic carriage? What does this mean?
positive stool cultures 12 months AFTER overcoming the disease
- potential to transmit S. typhi indefinitely
- usually asymptomatic
What is the treatment for an individual that is a chronic carrier of S. typhi?
Ciprofloxacin (for at least 1 month)
How does Paratyphoid A typically present?
similar to typhoid but less severe
rarely see rose spots
How does Paratyphoid B typically present?
usually a diarrheal illness
How can enteric fever be diagnosed in the 1ST WEEK?
via blood culture (80% in 1st week)
How can enteric fever be diagnosed in the 2ND WEEK onward?
via faeces culture
How can enteric fever be diagnosed in the 3RD WEEK onward?
via urine culture
What is the treatment for enteric fever?
- Fluid & Electrolyte Replacement + Supportive Management
- Antibiotics (for 10-14 days)
- - Ceftriaxone is the empiric treatment
What is the empiric antibiotic given to treat enteric fever?
Ceftriaxone (after susceptibilities - Ciprofloxacin, Azithromycin)
What vaccines maay be given to individuals to prevent enteric fever?
- Subunit Vacine (Vi polysaccharide)
- Live attenuated oral vaccine
What is the source/reservoir of salmonella gastoenteritis?
reptiles and environment (e.g. turtles, hedgehogs…)
What are the main transmission methods for salmonella gastroenteritis?
foodborne (chicken, beef, unpasteurized milk…)
faecal-oral
What is the incubation period for salmonella gastroenteritis?
18 to 72 hours
Virulent strains of salmonella can induce multiple host inflammatory responses and cytokines - this is mediated by what?
the lipopolysaccharide in the cell wall
What is the clinical features/presentation of salmonella gastroenteritis?
self-limiting (usually lasts 3-7 days)
diarrhea, nausea, headache, malaise
dehydration* (in extremes of age, immunocompromised)
Salmonella gastroenteritis may be chronically excreted for up to 4 weeks. What 4 things may increase and prolong excretion?
- antibiotics
- HIV
- inflammatory bowel disease
- diverticulosis
List the complications of non-typhoidal salmonella (salmonella gastroenteritis)
BSI
systemic disease (osteomyelitis, meningitis)
reactive arthritis
What is the treatment for salmonella gastroenteritis?
- Fluid & Electrolyte Replacement + Supportive Management
- NO Antibiotics (unless <12 months, >50, immunocompromised or have cardiac, valvular, endovascular abnormalities or joint disease)
What is the Vi antigen?
a/w Salmonella serotyping
is the virulence antigen
a specialized K antigen primarily found in strains of salmonella causing typhoid fever
List some of the characteristics of the Shigella species
gram negative bacilli
NON-lactose fermenter
COLOURLESS colonies on XLD agar
List the 4 serological groups of shigella and name it
Group A - S. dysenteriae
Group B - S. flexneri
Group C - S. boydii
Group D - S. sonnei
Which serological group of shigella is most common in tropical countries? (hint: also most severe form)
Group A - S. dysenteriae
What is the most commony serological group of shigella in the UK/Ireland?
Group D - S. sonnei
Which strain of shigella expresses the shiga toxin?
S. dysenteriae serotype 1
What are the 2 types of toxins a/w shigella?
- Enterotoxins
2. Shiga Toxin
What are the main transmission methods of Shigella?
faecal-oral
foodborne
contaminated water
What is the incubation period of Shigella?
24 to 72 hours (relatively slow)
What are the 2 main clinical features/presentations of Shigella dependent on what type of shigella strain is involved?
- Profuse, Watery Diarrhea
2. Dysentery
List the complications of Shigella
- intestinal complications (toxic megacolon, perforation, obstruction)
- BSI
- convulsions
- reactive arthritis
- HUS
What sample may be taken to help in the diagnosis of shigella? What investigation/test can be done?
Faeces Sample
- PCR or Culture
What is the treatment/management plan for shigella?
- Fluid & Electrolyte Replacement + Supportive Management
- Rarely Antibiotics (unless S. dysenteriae)
- - Ceftriaxone/Ciprofloxacin
If antibiotics are required for a shigella infection, which ones would be given empirically?
Ceftriaxone or Ciprofloxacin
List some of the characteristics of H. pylori
curved gram negative bacilli
asymptomatic coloniser of stomach
causes gastrititis + duodenal ulcers
What are the virulence factors for H. pylori?
- urease production
- motility (spiral shape, flagella, mucolytic enzymes)
- adheres to gastric epithelium
Cancer may be a complication of H. pylori infection and gastritis that consequently arises. What specific cancer may occur?
Gastric Cancer - Adenocarcinoma**
also MALT lymphoma and other GI cancers
How may H. pylori be detected? What investigations/tests may be done?
- Laboratory Testing - Faecal Antigen Testing, Serology…
- Endoscopy Biopsy - CLO Test, Histology…
- Urea Breath Test
