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2.2 Microbiology > Denise - Curved Gram Negative Rods (Campylobacter, Helicobacter, Vibrio) > Flashcards

Denise - Curved Gram Negative Rods (Campylobacter, Helicobacter, Vibrio) Flashcards

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1
Q

What are the three curved gram negative rods

A

Campylobacter
Helicobacter
Vibrio

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2
Q

Write about campylobacter species

A

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

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3
Q

What is the main Campylobacter species studied

A

C. jejuni
C. coli
C. fetus
C. cinaedia
C. lari

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4
Q

What are the reservoirs of Campylobacter jejuni

A

Animals
- Poultry up to 98% of carcasses
Undercooked poultry main source
Cross contamination during poultry processing
- unchlorinated water
- milk (raw milk)

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5
Q

What is the incubation time for C. jejuni and C. coli

A

2-7 days

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6
Q

What are the symptoms of C. jejuni and C. coli infection

A

Gastrointestinal infection
- diarrhoea (bloody)
- abdominal pain
- self limiting

Rarely accompanied by systemic disease

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7
Q

Write about C. fetus, C. cinaedi and C. lari infections

A

Systemic infections in the immunocompromised (HIV patients)

Symptoms: fever and headache

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8
Q

What sequelae infections does Campylobacter cause

A

Reactive arthritis (1% of patients after 1-2 weeks)
Bursitis
Endocarditis
Neonatal sepsis
Peripheral polyneuropathy

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9
Q

Write about peripheral polyneuropathy in Campylobacter infection

A

Guillain-Barre syndrome
Paralysis related to nerve demyelination
Molecular mimicry
Cross-reactive antibodies against gangliosides in human peripheral nerves

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10
Q

Write about the isolation of Campylobacter species

A

Difficult
Fastidious growth requirements
Biochemical inertness ( doesnt ferment carbs)
Complex taxonomy

Molecular detection used for screening faeces

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11
Q

What is done on day 1 campylobacter infection

A

Direct Molecular Detection of the SsrA gene

Selective culture

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12
Q

What molecular detection is carried out for the SsrA gene on campylobacter

A

Real time PCR
Enteric BIO
BD Max
Syndromic Testing
BioFire GI Panel

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13
Q

What is done on day 2 investigation of Campylobacter

A

Selective media -> CCDA or chromagar

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14
Q

Writea bout CCDA agar

A

Modified CCDA
Charcoal, cefoperazone, deoxycholate amphericin agar

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15
Q

How does C. jejuni appear on CCDA

A

Grey moist flat spreading colonies

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16
Q

How does C. coli appear on CCDA

A

Creamy grey moist slightly raised

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17
Q

What are the limitations of CCDA

A

Background flora
Media Performance
Slow growth

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18
Q

What are the growth requirements for Campylobacter

A

Strictly microaerophilic
(5-19% O2 with added CO2)
Thermophilic

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19
Q

What are the basic characteristics of Campylobacter

A

Gram negative spiral (gull wing) shaped cells
Small and thin
Coccoid after O2 exposure
Oxidase positive
Catalase positive

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20
Q

What confirmatory tests are carried out for Campylobacter

A

Motile
Hippurate hydrolysis positive
Susceptibility to antimicrobiala

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21
Q

Write about the identification of C. jejuni and C. coli

A

Grow at 42 degrees but not 25 degrees
Susceptible to nalidixic acid
Resistant to cephalothin
H2S positive

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22
Q

What is an important ID of C. jejuni

A

Hydrolyses hippurate

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23
Q

What is an important ID of C. fetus

A

Will grow at 25 degrees, some at 42 degrees
Nalidixic acid resistant
Cephalothin suscpetible

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24
Q

Write about the treatment of Campylobacter

A

Fluid and electrolytes (bloody diarrhoea)
Ciprofloxacin
Eryhromycin

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25
Q

Write about the antimicrobial resistance seen in Campylobacter

A

Fluoroquinolone and Macrolides treatment
Resistance via gene mutations and efflux pump

26
Q

How is Campylobacter prevented

A

Thorough cooking
Pasteutisation

27
Q

Write about Helicobacter species

A

Campylobacter-like organisms found in the stomachs of patients with type B gastritis
Curved spiral organisms
Helicobacter pylori (human pathogen no animal reservoir)

28
Q

Write about Helicobacter Pylori
(5)

A

Infectious agent associated with peptic ulcer disease
Treatable with antibiotics
Triggers MALT malignancies
Prevalence 50% globally
80% developing countries

29
Q

Write about the pathogenesis of H. pylori
(3)

A

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

30
Q

What are the virulence factors of H. pylori

A

Flagella
Urease
Exotoxins
Secretory enzymes
Lipopolysaccharides
Outer proteins
Type IV secretion system
Effectors

31
Q

What do the H, pylori flagella do?

A

Bacterial mobility and chemotaxis to colonise under mucosa

32
Q

What do the H, pylori exotoxins do

A

vacA - vacuolating toxin

Causes gastric mucosal injury

33
Q

What do the H, pylori secretory enzymes do

A

Mucinase, protease and lipase

Gastric mucosal injury

34
Q

What do the H, pylori Type IV secretion system do

A

Pilli-like structure for injection of effectors

35
Q

What do the H, pylori urease do

A

Neutralises gastric acid
Gastric mucosal injuria by ammonia

36
Q

What do the H, pylori lipopolysaccharides do

A

Adhere to host cells
Inflammation

37
Q

What do the H, pylori outer proteins do

A

Adhere to host cells

38
Q

What do the H, pylori effectors do

A

cagA
Actin remodelling
IL-8 induction, host cell growth and apoptosis inhibition

39
Q

How do we detect H. pylori

A

Invasive techniques to examine stomach
Gastric biopsies taken at endoscopy

Real time PCR on faeces

Serology
Urea breath tests
Faecal antigen tests

40
Q

Write about the sampling for H. pylori

A

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

41
Q

What is important to note about the staining of H. pylori

A

Young cultures grown in vitro frequently stain gram-positive

42
Q

What are the basic characteristics of H. pylori

A

Gram negative spiral
Oxidase positive
Catalase positive

43
Q

What confirmatory tests are done for H. pylori

A

Urease test - positive
Molecular detection for ure cagA targets

44
Q

How is H. pylori treated

A

Triple therapy with:
- amoxicillin
- clarithromycin
- proton pump inhibitor

45
Q

Write about the vibrio species

A

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

46
Q

What are the reservoirs for Vibrio

A

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

47
Q

Write about cholera infection

A

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

48
Q

Write about the epidemiology of Cholera

A

Endemic to 50 countries
Epidemics in africe, asia, middle east, south america etc
Haiti epidemic of 2010
Yemen epidemic of 2017 -> 330,000 cases

49
Q

What are the two main cholera toxins

A

Cholera toxin (CT)

Toxin-coregulated pilus (TCP)

50
Q

Write about the cholera toxin pathogenesis

A

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

51
Q

Write about the toxin-coregulated pilus (TCP)

A

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

52
Q

What is done on the day 1 investigation of cholera

A

Direct detection for V. cholera gene
- Real time PCR
- EntericBIO DX
- Syndromic testing
- Biofire GI panel

53
Q

What is done on day 2 investigation of cholera

A

Selective enrichment
- alkaline peptone water

54
Q

What is done on day 3 investigation of cholera

A

Selective culture
- TCBS/Chromagar

55
Q

What is done on day 4 investigation of cholera

A

Biochemical ID
Ref lab serotyping
Ref lab toxin detection

56
Q

Write about the basic characterisitics of cholera

A

Curved GNB
Oxidase-positive

57
Q

What are the biochemical results of cholera

A

Non lactose fermenter
Sucrose positive

58
Q

How is cholera enriched

A

Alkaline peptone water

59
Q

How is cholera selectively isolated

A

Thiosulfate citrate bile salts sucrose agar - sucrose positive

MacConkey - NLF

60
Q

How is cholera treated

A

Fluid and electrolytes
Doxycycline
Ciprofloxacin

61
Q

How is cholera prevented

A

Vaccination
Public Health
Faecal contamination of water supplies

62
Q

What is done on day 3 investigation of campylobacter

A

Biochemical ID
Ref lab

2.2 Microbiology (60 decks)

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