Denise - Curved Gram Negative Rods (Campylobacter, Helicobacter, Vibrio) Flashcards
What are the three curved gram negative rods
Campylobacter
Helicobacter
Vibrio
Write about campylobacter species
Gram-negative curved, S shaped or spiral rods
Non-spore forming
Oxidase positive
Catalase positive
Motile (uni or bi-polar flagella)
Micrroaerophilic
Some are thermophilic
Do not oxidise or ferment Carbohydrates
What is the main Campylobacter species studied
C. jejuni
C. coli
C. fetus
C. cinaedia
C. lari
What are the reservoirs of Campylobacter jejuni
Animals
- Poultry up to 98% of carcasses
Undercooked poultry main source
Cross contamination during poultry processing
- unchlorinated water
- milk (raw milk)
What is the incubation time for C. jejuni and C. coli
2-7 days
What are the symptoms of C. jejuni and C. coli infection
Gastrointestinal infection
- diarrhoea (bloody)
- abdominal pain
- self limiting
Rarely accompanied by systemic disease
Write about C. fetus, C. cinaedi and C. lari infections
Systemic infections in the immunocompromised (HIV patients)
Symptoms: fever and headache
What sequelae infections does Campylobacter cause
Reactive arthritis (1% of patients after 1-2 weeks)
Bursitis
Endocarditis
Neonatal sepsis
Peripheral polyneuropathy
Write about peripheral polyneuropathy in Campylobacter infection
Guillain-Barre syndrome
Paralysis related to nerve demyelination
Molecular mimicry
Cross-reactive antibodies against gangliosides in human peripheral nerves
Write about the isolation of Campylobacter species
Difficult
Fastidious growth requirements
Biochemical inertness ( doesnt ferment carbs)
Complex taxonomy
Molecular detection used for screening faeces
What is done on day 1 campylobacter infection
Direct Molecular Detection of the SsrA gene
Selective culture
What molecular detection is carried out for the SsrA gene on campylobacter
Real time PCR
Enteric BIO
BD Max
Syndromic Testing
BioFire GI Panel
What is done on day 2 investigation of Campylobacter
Selective media -> CCDA or chromagar
Writea bout CCDA agar
Modified CCDA
Charcoal, cefoperazone, deoxycholate amphericin agar
How does C. jejuni appear on CCDA
Grey moist flat spreading colonies
How does C. coli appear on CCDA
Creamy grey moist slightly raised
What are the limitations of CCDA
Background flora
Media Performance
Slow growth
What are the growth requirements for Campylobacter
Strictly microaerophilic
(5-19% O2 with added CO2)
Thermophilic
What are the basic characteristics of Campylobacter
Gram negative spiral (gull wing) shaped cells
Small and thin
Coccoid after O2 exposure
Oxidase positive
Catalase positive
What confirmatory tests are carried out for Campylobacter
Motile
Hippurate hydrolysis positive
Susceptibility to antimicrobiala
Write about the identification of C. jejuni and C. coli
Grow at 42 degrees but not 25 degrees
Susceptible to nalidixic acid
Resistant to cephalothin
H2S positive
What is an important ID of C. jejuni
Hydrolyses hippurate
What is an important ID of C. fetus
Will grow at 25 degrees, some at 42 degrees
Nalidixic acid resistant
Cephalothin suscpetible
Write about the treatment of Campylobacter
Fluid and electrolytes (bloody diarrhoea)
Ciprofloxacin
Eryhromycin
Write about the antimicrobial resistance seen in Campylobacter
Fluoroquinolone and Macrolides treatment
Resistance via gene mutations and efflux pump
How is Campylobacter prevented
Thorough cooking
Pasteutisation
Write about Helicobacter species
Campylobacter-like organisms found in the stomachs of patients with type B gastritis
Curved spiral organisms
Helicobacter pylori (human pathogen no animal reservoir)
Write about Helicobacter Pylori
(5)
Infectious agent associated with peptic ulcer disease
Treatable with antibiotics
Triggers MALT malignancies
Prevalence 50% globally
80% developing countries
Write about the pathogenesis of H. pylori
(3)
H. pylori penetrates the mucous layer lining the stomach’s epithelium, attracted to the chemotactic substances haemin and urea
H. pylori recruits and activates inflammatory cells. They also release urease that cleaves urea, producing NH3 that neutralises stomach acid in its vicinity
H. pylori cytotoxin and ammonia produced by its urease cause destruction of mucous-producing cells, exposing underlying connective tissue to stomach acid
What are the virulence factors of H. pylori
Flagella
Urease
Exotoxins
Secretory enzymes
Lipopolysaccharides
Outer proteins
Type IV secretion system
Effectors
What do the H, pylori flagella do?
Bacterial mobility and chemotaxis to colonise under mucosa
What do the H, pylori exotoxins do
vacA - vacuolating toxin
Causes gastric mucosal injury
What do the H, pylori secretory enzymes do
Mucinase, protease and lipase
Gastric mucosal injury
What do the H, pylori Type IV secretion system do
Pilli-like structure for injection of effectors
What do the H, pylori urease do
Neutralises gastric acid
Gastric mucosal injuria by ammonia
What do the H, pylori lipopolysaccharides do
Adhere to host cells
Inflammation
What do the H, pylori outer proteins do
Adhere to host cells
What do the H, pylori effectors do
cagA
Actin remodelling
IL-8 induction, host cell growth and apoptosis inhibition
How do we detect H. pylori
Invasive techniques to examine stomach
Gastric biopsies taken at endoscopy
Real time PCR on faeces
Serology
Urea breath tests
Faecal antigen tests
Write about the sampling for H. pylori
H, pylori is a fragile organism
- dessiccation
- contact with oxygen
- room temperature
Grinding of biopsy specimens
Isolation of the organism: fastidious
Agar base, blood supplement, antimicrobicals
Microaerophilic capnophilic 37degrees for 3-7 days
What is important to note about the staining of H. pylori
Young cultures grown in vitro frequently stain gram-positive
What are the basic characteristics of H. pylori
Gram negative spiral
Oxidase positive
Catalase positive
What confirmatory tests are done for H. pylori
Urease test - positive
Molecular detection for ure cagA targets
How is H. pylori treated
Triple therapy with:
- amoxicillin
- clarithromycin
- proton pump inhibitor
Write about the vibrio species
Closely related to enterobacterales
Motile single motile flagella
Natural constituents of freshwater, estuarine and marine environments
Seasonal distribution warmer months
2 chromosomes
Recombination and horizontal gene transfer
O antigens in GN Outer Membrane are useful for ID
What are the reservoirs for Vibrio
Faecal contamination of water and food
Closely linked to poor sanitation and lack of clean drinking water
At risk areas: slums, camps for refugees
Disruption of water/sanitation systems
Seasonal warming of coastal water increase risk
Write about cholera infection
3-5 million cases a year
100,000 deaths a year (50% in children <5)
Acute secretory diarrheal illness
Rapidly dehydrating
Endemic, epidemic, or a pandemic disease
Write about the epidemiology of Cholera
Endemic to 50 countries
Epidemics in africe, asia, middle east, south america etc
Haiti epidemic of 2010
Yemen epidemic of 2017 -> 330,000 cases
What are the two main cholera toxins
Cholera toxin (CT)
Toxin-coregulated pilus (TCP)
Write about the cholera toxin pathogenesis
AB toxin
AB5 family - ADP ribosyltransferase
Fluid loss via CAMP-mediated activation of anion secretion
Inhibition of electoneutral NaCl absorption
Massive Cl- secretion leads to severe diarrhea
Encoded on filamentous phage CTXO
Write about the toxin-coregulated pilus (TCP)
Type IV pilus
Mediates adherence and microcolony formation
Required for intestinal colonisation
Encoded on V, cholerae pathogenicity island (VPI)
TCP is the receptor for CTXO
What is done on the day 1 investigation of cholera
Direct detection for V. cholera gene
- Real time PCR
- EntericBIO DX
- Syndromic testing
- Biofire GI panel
What is done on day 2 investigation of cholera
Selective enrichment
- alkaline peptone water
What is done on day 3 investigation of cholera
Selective culture
- TCBS/Chromagar
What is done on day 4 investigation of cholera
Biochemical ID
Ref lab serotyping
Ref lab toxin detection
Write about the basic characterisitics of cholera
Curved GNB
Oxidase-positive
What are the biochemical results of cholera
Non lactose fermenter
Sucrose positive
How is cholera enriched
Alkaline peptone water
How is cholera selectively isolated
Thiosulfate citrate bile salts sucrose agar - sucrose positive
MacConkey - NLF
How is cholera treated
Fluid and electrolytes
Doxycycline
Ciprofloxacin
How is cholera prevented
Vaccination
Public Health
Faecal contamination of water supplies
What is done on day 3 investigation of campylobacter
Biochemical ID
Ref lab
