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Microorganisms + Disease > Gram negative bacterial pathogens L3 > Flashcards

Gram negative bacterial pathogens L3 Flashcards

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1
Q

what are the three layers of gram negative cell wall

A

outer membrane
periplasmic space
cytoplasmic membrane

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2
Q

what colour are gram positive strains in dye

A

blue

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3
Q

what colour are gram negative strains in dye

A

pink/red

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4
Q

what shape is Neisseria meningitidis and Neisseria gonorrhoeae

A

Gram-negative diplococci

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5
Q

what does Neisseria meningitidis and Neisseria gonorrhoeae

require for growth

A

Fastidious – grow well on supplemented chocolate agar at 37°C in 5% CO2 in air

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6
Q

what are Neisseria meningitidis and Neisseria gonorrhoeae

colonies like

A

Colonies transparent, non-haemolytic, 1-5 mm in diameter

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7
Q

what oxidase is Neisseria meningitidis and Neisseria gonorrhoeae

A

oxidase positive

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8
Q

what does Neisseria meningitidis and Neisseria gonorrhoeae

do to glucose

A

Metabolize glucose (meningococcus also utilises maltose) to acid

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9
Q

what is Neisseria meningitidis

A

Obligate human pathogen

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10
Q

where is Neisseria meningitidis found

A

Asymptomatic nasopharyngeal carriage in c. 10% population

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11
Q

when does Neisseria meningitidis cause disease

A

bacterium enters the bloodstream and crosses the blood/brain barrier

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12
Q

how are meningococci segregated

A

13 serogroups – serogroups A, B, C, W135 and Y cause most infections

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13
Q

what causes bacterial meningitis in children & young adults – may cause epidemics

A

Neisseria meningitidis

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14
Q

what does Neisseria meningitidis cause

A

sepsis, septic arthritis, endophthalmitis, conjunctivitis etc.

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15
Q

what vaccines are available for Neisseria meningitidis

A

C and B

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16
Q

what are symptoms of Meningococcal meningitis

A

marked neck
stiffness
photophobia
purpuric non-blanching rash

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17
Q

what is CSF

A

Cerebrospinal fluid

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18
Q

what is gonorrhoea and an example of a bacteria that causes it

A

Gonorrhoea is a common bacterial infection transmitted by sexual contact or perinatally
Neisseria gonorrhoeae

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19
Q

what are gonococci like

A

do not tolerate drying, hence samples should be inoculated onto appropriate media immediately

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20
Q

what does Neisseria gonorrhoeae cause

A

acute urethritis in men and cervicitis (predominantly) in women
in neonates – causes eye infection (ophthalmia neonatorum)

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21
Q

what is Gram-stain of urethral discharge

made of

A

Numerous polymorphonuclear cells

Intra-cellular gram-negative diplococci

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22
Q

what can Ophthalmia neonatorum

cause

A

Purulent ocular discharge

May cause blindness if untreated

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23
Q

what is Moraxella catarrhalis

A

Gram-negative diplococcus indistinguishable from Neisseria by Gram staining

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24
Q

where does Moraxella catarrhalis colonise

A

Colonises upper respiratory tract in c. 5% of adults

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25
what does Moraxella catarrhalis cause
Otitis media, Sinusitis, pneumonia in the elderly and in patients with Chronic Obstructive Pulmonary Disease (COPD)
26
what are examples of Enterobacteriaceae
``` Escherichia Klebsiella Proteus / Morganella Salmonella Serratia Shigella Yersinia ```
27
what is an increasing problem with Enterobacteriaceae
antibiotic resistance is an increasing problem in these organisms many produce enzymes that degrade commonly used antibiotics enzymes are called Extended Spectrum Beta lactamases – ESBLs)
28
what is Escherichia coli and where does it colonise
Commensal flora in human and other animals GI tract where they do not normally cause any problems survive in soil and water
29
what is Escherichia coli like
Facultatively anaerobic Bacilli Motile
30
what does Escherichia coli do to lactose
Most strains ferment lactose and are indole positive
31
what can Escherichia coli cause
UTI Neonatal meningitis Wound infection Intra-abdominal abscess Sepsis – bacteria enter the bloodstream
32
how does a UTI form due to Escherichia coli
persons own gut flora due to contamination of the urethra - ascends to the bladder and may reach the kidneys in some cases
33
what does Escherichia coli cause
Some strains of E.coli cause diarrhoea
34
how does Escherichia coli lead to disease
Disease follows ingestion of contaminated/uncooked food or contact with faeces - sources of contamination : animals or environmental contamination
35
how are Escherichia coli grouped
Based on biochemical/serological properties and the types of pathogenic mechanism used, strains are placed into different groups
36
what bacteria causes the commonest food poisoning
Campylobacter | then salmonella
37
what is Campylobacter associated with
Most cases sporadic, associated with poultry and raw milk Contamination of chicken – where they naturally live When slaughter they get contaminated with the faecal material
38
what is Campylobacter like
Spiral bacterium, micro-aerophilic, grows at 42°C
39
oxidase test on Campylobacter
oxidase positive
40
what does Campylobacter jejuni cause
Prodromal fever (fever before they see any symptoms), headache Diarrhoea vomiting Abdominal pain Rare systemic infections – fever & positive blood cultures
41
why can there be blood in diarrhoea if infected with Campylobacter jejuni
move from the gut and get into the blood – due to the damage of the mucus lining
42
what is Helicobacter pylori like
Pleomorphic rod – microaerophilic (doesn’t like too much oxygen) many spiral shaped
43
what does Helicobacter pylori cause
infection in the stomach (gastric acid in stomach usually kills everything, but this organism has evolved to survive) and duodenum Powerful urease enzyme, colonise gastric mucosa
44
what does Helicobacter pylori need for growth
Selective media for culture from tissue biopsies
45
what is the most common bacteria to cause infection
Helicobacter pylori
46
what can be used for diagnosis from biopsies
helicobacter pylori produces a powerful urease enzyme allowing colonisation of the gastric mucosa – used in diagnosis from biopsies
47
what is the effect of Helicobacter pylori | making urease
Urease breaks down urea produces ammonia, it neutralizes gastric acid around organism
48
what are Pseudomonads and non-fermenters associated with
Associated with moist environments | P. aeruginosa most associated with human disease
49
what are Pseudomonads and non-fermenters like
``` Non-sporing Non-capsulate (no capsule) Usually motile Strictly aerobic (under most conditions will only grow when there is oxygen around) Thin GNB (gram negative bacillus) ```
50
what do many strains ofPseudomonads and non-fermenters produce
produce pigments (thought to be part of virulence mechanism) e.g. pyocyanin
51
what is the Pseudomonads and non-fermenters metabolism
Oxidative metabolism (compared to the Enterobacteriaceae-fermentative)
52
where does Pseudomonas aeruginosa commonly colonise
colonises wounds
53
what can Pseudomonas aeruginosa cause
outer (otitis externa) and inner (malignant otitis) ear infections eye infections sepsis
54
what can Pseudomonas aeruginosa cause in cystic fibrosis patients
pneumonia
55
what are non-fermenters
Heterogeneous group including Acinetobacter it is biochemically inert and resistant to many antibiotics
56
what are vibrionaceae like
Short, comma-shaped bacilli Actively motile Fermentative
57
what oxidase are Vibrionaceae
oxidase positive
58
what is halophilic and and example
Halophilic live in salt water (eg. V. vulnificus)
59
what is non halophilic and an example
non-halophilic live in non salt water (eg. V. cholera)
60
how does Vibrionaceae cause infection
occurs through ingestion of contaminated food or water
61
what agar is Vibrionaceae grown on
thiosulphate, citrate, bile-salt, sucrose (TCBS) agar or in alkaline peptone-water
62
what does Vibrionaceae cholerae need for growth and what does it produce
grown on TCBS – ferments sucrose and produces yellow colonies
63
what is Vibrionaceae cholerae like
has a flagellum so is motile | Gram-negative bacilli

Microorganisms + Disease (16 decks)

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