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Antimicrobial and chemotherapy > Gram negative organisms of clinical significance > Flashcards

Gram negative organisms of clinical significance Flashcards

1
Q

GI G-ve rods characteristics

A

Found in soil and water
Gi tract Commensals of human and other animals
often sensitive to drying (like water)
Facultative anaerobes
Contain LPS(Lipopolysaccharide)
*Antigenic
*potential endotoxin
Diverse taxonomy and only a fraction are G-ve rod
Can cause disease in both the body and GIT
Faecal-oral is the route of transmission

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2
Q

where is E.coli found

A

In the colon of humans and animals

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3
Q

Characteristics of E.coli

A
  • Pathogenic within and outside the GIT
  • Fimbriae/pili adhere to the mucosal surfaces
  • Can be motile or non-motile
  • Ferment lactose
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4
Q

What type of antigen do E.coli have?

A

3 structural antigens
O, H, K
The serotypes are associated with different diseases

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5
Q

Where are the E.coli antigens located?

A

O antigens: On cell wall
H antigens: Flagellae
K antigens: Capsule / mucoid layer

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6
Q

What are the different intestinal pathogenic types?

A

Enterotoxigenic
Enteropathogenic
Enterohaemorrhagic
Enteroinvasive

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7
Q

What is Enterotoxigenic (ETEC) Known as

A

Known as travelers diarrhoea

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8
Q

What are the common causes of enterotoxigenic?

A

Food/water, human waste, person-to-person

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9
Q

What are the two enterotoxins and what are the results of that?

A

Hypersecretion of Chloride and water
Inhibition of sodium reabsorption

Lead to watery diarrhoea

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10
Q

Enteropathogenic (EPEC)

A
  • Diarrhoea in infants (poor sanitation)
  • Newborns infected during birth
  • Attach to small intestine
  • Shiga-like (named after Kiyoshi Shiga) toxins
  • Destruction of microvilli, development of lesions
  • Watery diarrhoea (chronic)
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11
Q

Enterohaemorrhagic (EHEC)

A
  • Most notorious strain O157:H7
  • Binds to cells in large intestine
  • Verotoxins in large amounts
  • These affect host cell protein synthesis
  • Severe copious bloody diarrhoea (haemorrhagic colitis)
  • may progress to haemolytic uraemic syndrome (HUS)
    • Fever, acute renal failure, anaemia
    • Common in children 5-10yrs (still under 10% of cases)
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12
Q

Why are antibiotic avoided in EHEC/STEC

A

This is because the death of E.coli will lead to rapid release of the toxins which would lead to worsening of the condition.

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13
Q

Enteroinvasive (EIEC)

A

No toxins but cause direct mucosal damage due to invasive infection
Dysentery-like syndrome
Fever and bloody stools

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14
Q

What steps are taken to avoid and treat E.coli enteritis

A
  • Care in selection, preparation and consumption of food and water
  • Maintain fluid and electrolyte balance
  • Antibiotics can shorten duration(probably avoid if enterohaemorrhagic)
  • Resistance is widespread and readily spread
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15
Q

What are some Extraintestinal diseases caused by E.coli

A
  • UTI caused by cystitis, pyelonephritis
    • Fimbriae (adhesion), haemolysin, resistance to immune system activity (capsule)

-Neonatal meningitis: K antigen is the major virulent factor on the capsule
Major cause of infection with the first month of life
These Nosocomial infection which can result in sepsis and bacteremia

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16
Q

Treatment for extraintestinal E.coli infections?

A

Antibiotic required expect for EGHEC

  • Beta-lactams: Penicillin V and G No amoxicillin
  • 2nd gen cephalosporins and upwards
  • ESBL strains: carbapenems
  • nitrofurantoin, ciprofloxacin, trimethoprim +/- sulphamethoxazole, fosfomycin, …
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17
Q

What is salmonella?

A

An infection that leads to various diseases; gastroenteritis, typhoid fever
All strains grouped as Salmonella enterica

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18
Q

What are the specific serotypes/subtypes of samlonella

A

Typhi

Typhimurium

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19
Q

Salmonella characteristic

A
  • Widely distributed in nature
  • Do not ferment lactose (Lac-)
  • Typhi – exclusively human pathogen
  • Others – other animals and foods
  • Epidemics in crowded situations
  • Invade epithelial cells of the small intestine
  • Disease may become systemic
  • Intracellular, survive in phagocytes
20
Q

Gastroenteritis symptoms

A

Nausea, vomiting, non-bloody diarrhoea
Develops within 48hrs
Fever and abdominal cramping

21
Q

what serotypes is Gastroenteritis

A

Typically non-typhi

22
Q

What is serotype of typhoid fever

A

Typhi

23
Q

Symptoms of typhoid fever

A

Severe, life-threatening, systemic illness
Fever and abdominal symptoms
Also: headache, chills, sweats, weakness, sore throat, cough, myalgia

24
Q

Treatment of Gastroenteritis

A

Antibiotics may not be useful so supportive treatment should be used alone

25
Q

Treatment of enteric fever (typhoid)

A

fluoroquinolones, b-lactams, macrolides

26
Q

Characteristics of campylobacter

A

Curved, spiral or S-shaped rods
• Single flagellum (motile)
• Microaerophilic
• Don’t ferment carbohydrates
• Infect intestine (jejunun, ileum, colon)
• Bacteraemia possible though rare (extremes
of age, co-morbidity)

27
Q

Where are campylobacters found and how is it transmitted

A

Widely distributed in nature
– Fowl (major reservoir) and Mammals
• Faecal / oral route transmission

28
Q

What does campylobacter cause

A

Cause intestinal disease – rarely extra-intestinal

Acute enteritis

29
Q

Which species of campylobacter causes the most disease

A

By the C.jejuni species -99%

30
Q

Properties of acute enteritis

A

1-7 days incubation
– Self-limiting (but several weeks)
– Systemic symptoms: Fever, headache, myalgia
– Intestinal symptoms: cramps, diarrhoea

31
Q

What is used to treat acute enteritis caused by Campylobacter jejuni

A

Thorough cooking (esp BBQ chicken),
milk pasteurisation, disinfect surfaces
– Fluid and electrolyte balance often sufficient
– Antibiotics if needed (start early & if severe):
• erythromycin / clarithromycin (resistance?)
• ciprofloxacin
• 3rd generation cephalosporin if very severe

32
Q

What is shigella

A

Shigellosis (bacterial bacillary dysentery

It is intestinal

33
Q

Properties/characteristics of Shigella

A 
Non-motile, unencapsulated,
does not ferment lactose (Lac-)
Person-to-person, contaminated stools
Also: flies, food, water
Low infectious dose (10 - 200 organisms)
34
Q

What are the 2 of 4 groups of shigella and how do they operate

A

Group A: S. dysenteriae (most severe)
Group D: S. sonnei

  • Invade and destroy mucosa of large intestine
  • Shigatoxin – enterotoxic, cytotoxic
35
Q

What are the symptoms Group A: S. dysenteriae

A 
-Diarrhoea with blood, mucous and painful
abdominal cramps
-Severe in children and elderly
-Malnourished: dehydration and death
-Resolves in 1 week (if survived)
36
Q

Treatment for group A shigella

A

ciprofloxacin, ceftriaxone or azithromycin

– Antibiotics reduce duration and shedding
– But Widespread resistance
– Vaccine in development

37
Q

What is vibrio Cholerae what is it shaped like

A

Short, curved rod-shaped with Single polar flagellum

38
Q

What are the properties of vibrio cholerea

A 
Facultative anaerobes
Require NaCl – waterborne organisms, so
seawater / estuaries 
Transmitted via food and water
No known animal reservoirs or vectors
Carriage in humans uncommon
Associated with raw seafood
Outbreaks – poor sanitation of water supplies
39
Q

Vibrio cholerae infection

A

Infects small intestine
• Incubation, few hrs up to 1-2 days
• Adhesion factors (colonisation and virulence)
• Enterotoxin causes massive fluid and electrolyte
loss (secretory diarrhoea)
• “Rice-water” stools

40
Q

Treatment options for vibrio cholera includes:

A

Tetracyclines, macrolides, quinolones
-Severe disease occurs in about 5% of cases:
• If untreated: 50% death within hrs
• Treatment: <1% death
– Aggressive replacement of fluid & electrolytes
– Antibiotics decrease duration and shedding

41
Q

List the 3 Yersinia species

A

Y. enterocolitica (enterocolitis)
– Y. pseudotuberculosis (enterocolitis, despite name)
– (Y. pestis – bubonic plague)

42
Q

Properties of Yersinia enterocolitica

A

Contaminated food (abattoirs, raw meat)
• Lesions in ileum, enlargement of lymph nodes
• Enterocolitis: fever, abdominal pain, diarrhoea,
right lower quadrant tenderness
(pseudoappendicitis)
– Resolves in 2-3 weeks
• May → Polyarthritis, pharyngitis, septicaemia

43
Q

Treatment of yersinia enterocolitica

A

ciprofloxacin,

trimethoprim-sulphamethoxazole

44
Q

what is helicobacter pylori

A

Curved or spiral organisms,
closely related to Campylobacter

Multiple polar flagellae (corkscrew motility)

– Produces urease (urea to ammonia, protects
against acid)
– Causes sub-acute gastritis, leading to
duodenal and gastric ulcers

45
Q

Helicobacter pylori properties

A
  • World-wide distribution, very common
  • Person-to-person transmission
  • “Never” isolated from food or water
  • Untreated: chronic life-long condition
  • Colonises stomach, duodenum, oesophagus
  • Survives in mucus layer coating epithelium
46
Q

Infections caused by helicobater pylori

A 
Initial infection
– 1 week
– Gastritis, diarrhoea
Chronic
– Superficial gastritis, ulcers
– Risk of carcinoma, B-cell lymphoma
Elimination requires combination therapy
– Readily develops resistance,
always multiple agents
47
Q

Treatment of helicobater

A

– Proton pump inhibitor,
–amoxicillin,
–clarithromycin,
–metronidazole,

Antimicrobial and chemotherapy (4 decks)

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