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microorganisms > properties of bacteria > Flashcards

properties of bacteria Flashcards

1
Q

Staphylococcus aureus

A

Gram Positive

  • main coagulase positive species
  • stains golden on a blood agar plate
  • produces pus-forming soft tissue infections that are carried in the bloodstream
  • eg. MRSA
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2
Q

where does Staph aureus invade?

A 
axilla
anterior nares
throat
perineum
GI tract
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3
Q

virulence factors of Staph aureus

A
  • protein A on cell wall helps it to evade phagocytosis by immune cells
  • coagulase enzyme produces a fibrin capsule to protect against phagocytosis
  • hyalurorindase enzyme breaks down host tissue
  • haemolysins (exotoxin) produces pores in RBCs
  • toxins cause toxic shock, boils, pneumonia
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4
Q

conditions caused by Staph aureus

A 
Skin and soft tissue infections
Pneumonia 
Bone and joint infections 
Endocardits - Discitis 
Toxin mediated diseases: 
- Scalded skin syndrome
- Toxic shock syndrome 
- Gastroenteritis
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5
Q

Gram positive

coagulase negative

A

S. epidermis
S. capitis
S. saphrophyticus

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6
Q

action of…
S. epidermis
S. capitis
S. saphrophyticus

A
  • normal commensal flora of the skin

- can cause infection in the presence of prosthetic material

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7
Q

alpha haemolytic streptococci

A

S. pneumoniae
S. oralis
S. salivaris

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8
Q

diseases of S. pneumoniae

A 
- most common cause of community acquired pneumonia
linked to...
- meningitis
- sinusitis
- otitis media 
- infective endocarditis
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9
Q

virulence of S. pneumoniae

A
  • Produces pneumolysin which causes – α-haemolysis
  • Peptidoglycan and theicoic acid are the main components of cell wall
  • Has ability to form a capsule which stops phagocytosis by PMN
  • Colonises the nasopharynx of 5 to 10% healthy adults and 20-40% of healthy children
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10
Q

S. oralis, S. salivarius

A

normal mucosal flora, can cause endocarditis if they infect heart valves

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11
Q

gram positive, beta haemolytic Group A

A

S. pyogenes

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12
Q

gram positive, beta haemolytic Group B

A

S. agalactiae

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13
Q

Streptococcus pyogenes causes…

A
  • pharyngitis
  • scarlet fever
  • rheumatic fever
  • post-streptococcal glomerulonephritis
  • bacteraemia
  • necrotising faciitis
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14
Q

virulence factor of S. pyogenes

A

protein M

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15
Q

S. agalactiae

A
  • normal vaginal/rectal flora

- can cause neonatal meningitis, bacteraemia, pneumonia, fever in labour

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16
Q

enterococci

A

invade the gut to produce UTIs and intra-abdonimal sepsis

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17
Q

gram positive bacilli

A

Bacillus anthracis
Listeria monocytogenes
Corynebacterium diphtheriae

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18
Q

Bacillus anthracis

A
  • found in soil
  • disease of herbivores
  • multiple toxins and virulence factors - high mortality
  • humans infected by cutaneous inoculation or inhalation
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19
Q

L. monocytogenes

A

Gram positive, aerobic, bacillus

  • from soft cheese
  • causes intrauterine/neonatal septicaemia or meningitis in pregnany
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20
Q

C. diphtheriae

A

Gram positive, aerobic, bacillus

  • Corynebacterium
  • most pathogenic of normal skin commenals
  • transmitted via respiratory droplets
  • inflammation of the throat pseudomembrane - suffocation and bull neck
  • exotoxins inhibit protein synthesis - cell death in host
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21
Q

gram positive anaerobes

A

C. tetani
C. botulinum
C. difficile
C. perfringens

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22
Q

clostridium

A
  • gram positive rods
  • large, pleomorphic
  • obligate anaerobes
  • highly toxigenic
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23
Q

C. tetani

A
  • causes tetanus
  • ubiquitous in soil
  • neurotoxin - blocks GABA
  • causes spastic paralysis, hyper-sympathetic state, death
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24
Q

C. difficile

A
  • caused by ingestion of spores in (hospital) environment
  • enterotoxin causes diarrhoea and cell death of colonic epithelium
  • causes severe watery diarrhoea
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25
Q

C. perfringens

A
  • found in soil and human gut
  • a-toxin lecithinase - damages cell membranes and causes haemolysis
  • causes gas gangrene and soft tissue infections
  • food poisoning
26
Q

gram negative cocci

A

Neisseria meningitidis
Neisseria gonorrhoeae
Moraxella catarrhalis

27
Q

Neisseria meningitidis

A
  • some people carry it in their nasopharynx without any symptoms (commensal)
  • transmitted ny inhalation, direct contact
  • causes meningitis, bacteraemia, pneumonia
  • 6 groups: A, B, C, W, X, Y
    • characterised by polysaccharide capsule
    • effective vaccine available for most groups
28
Q

Neisseria gonorrhoeae

A
  • causal agent of gonorrhoea
  • transmitted sexually or perinatally (mother to child)
  • causes…
    • urithritis, cervicitis, pharyngitis, conjunctivitis
    • rectal infection
    • pelvic inflammatory disease
    • perihepatitis
    • disseminated infection
  • concerns about drug resistance means prevention is more realistic / a better option than cure
29
Q

Moraxella catarrhalis

A
  • common commensal of the human upper respiratory tract
  • opportunistic pathogen - altered flora causes commensal to become pathogen
  • in children, causes otitis media
  • in adults with COPD, causes lower respiratory tract infection
30
Q

gram negative fastidious bacilli

A

Haemophilus influenzae
Helicobacter pylori
Legionella pneumophilia

31
Q

Haemophilus influenzae

A
  • uncapsulated - pneumonia
  • capsulated - meningitis
  • otitis media
32
Q

Helicobacter pylori

A
  • produces buffers to allow it to survive stomach acid
  • causes gastritis, ulceration
  • linked to stomach cancer
33
Q

Legionella pneumophilia

A
  • carried by amoebae in water

- causes severe pneumonia

34
Q

non-fastitious sugar fermenters

A 
(aka enterobacteriae)
Escherichia coli
Klebisella
Shigella
Salmonella
35
Q

features of enterobacteriae

A
  • non-fastitious sugar fermenters
  • motile by polar flagella
  • have fimbriae for adhesion
36
Q

Escherichia coli

A
  • commonly found in human/animal guts

causes. ..
- diarrhoea
- UTIs
- bacteraemia
- intra-abdominal and biliary tract infection
- neonatal meningitis
- hospital acquired infections

37
Q

pathotypes of E. coli

A

enteropathogenic EPEC

enterotoxigenic ETEC

shiga-toxin producing STEC (aka. enterohaemorrhagic EHEC / verocytotoxin producing VTEC)

  • most common
  • causes bloody diarrhoea
  • comes from cattle

enteroinvasive EIEC

enteroaggregative EAEC

diffusively aggregative DAEC

38
Q

Klebisella

A
  • causes UTI, bacteraemia, pneumonia, liver abscesses

- important in hospitals due to antibiotic resistance and the need for infection control

39
Q

Shigella

A
  • found in unclean water and contaminated food
  • causes dynentery (bloody, low volume diarrhoea), abdominal pain, fever
  • can survive transit through stomach (acid resistant)
40
Q

types of Shigella

A
  • Shigella flexneri
  • Shigella sonnei
    from travelling:
  • Shigella dysenteriae
  • Shigella boydii
41
Q

Salmonella

A

Salmonella typhi:

  • traveller’s diarrhoea
  • typhoid fever

non typhoidal
- gastroenteritis

there are carriers of salmonella (typhoid carriers)
- salmonella excreted in stool and persists in the gall bladder

42
Q

gram negative non fastidious non fermenters

A

Campylobacter
Pseudomonas aeruginosa
Burholderia cepacian
Vibrido cholerae

43
Q

Campylobacter

A
  • microaerophilic - grows at sub atmospheric levels of oxygen
  • causes food poisoning
  • usually self limiting
  • from raw meat, unpasteurised milk, untreated water
  • C. fetus - causes severe infection in neonates
44
Q

Pseudomonas aeruginosa

A
  • huge range of virulence factors and AB resistance mechanisms
  • found widely in soil and water, has few nutritional requirements
  • opportunistic pathogens
  • Leads to cystic fibrosis complications and ventilator penumonia and bacteraemia in immunocompromised
  • resistant to many antibiotics
  • produces extracellular pigments eg. pyocyanin
45
Q

Burholderia cepacia

A

poor prognosis for CF patients

46
Q

Vibrido cholerae

A

causes bacterial gastroenteritis, self limiting diarrhoea

47
Q

gram negative anaerobes

A

Bacteroides fragilis

Fusobacterium necrophorum

48
Q

Bacteroides fragilis

A

associated with intra-abdominal and skin/soft tissue infections below the waist. highly penicillin resistant.

49
Q

Fusobacterium necrophorum

A

long filamentous rods which cause sore throat, peritonsillar abscess, Lemierre’s syndrome (infectious thrombophlebitis of the internal jugular vein)

50
Q

small, virus-like bacteria

A 
Mycoplasma pneumoniae
Chlamydia trachomatis
C. penumonia and C. psittaci
Rickettsia 
Mycobacterium tuberculosis
51
Q

acid fast bacteria

A

Mycobacterium tuberculosis

52
Q

features of acid fast bacteria

A

These bacteria are strict aerobic bacilli. Their cell wall is composed of a very thick layer of wax and lipid called mycolic acid. It is a very slow growing bacterium.

53
Q

acid fast test

A

Ziehl-Neelsen staining

  1. carbol-fuchsin and heat
  2. then decolorized with an acid alcohol
  3. counter stained with methylene blue

acid fast = red
non acid fast = blue

54
Q

Mycoplasma pneumoniae

A
  • walking pneumonia
  • haemolytic anaemia
  • rash, erythema
  • cervical lymphadenopathy
  • diagnosed by PCR, serology
  • causes penicillin resistant pneumonia
  • treated with clarithromycin
55
Q

Chlamydia trachomatis

A
  • intracellular
  • causes trachoma
  • STI
  • lyphogranuloma vereum
  • diagnosed by PCR
  • treated with macrolides
56
Q

Rickettsia

A

transmitted by parasites, present as spotted fever or typhus

57
Q

Mycobacterium tuberculosis

A

causes pneumonia with latency, requires intense combination treatment

58
Q

features of non culturable bacteria

A
  • no cell wall
  • limited metabolic activity
  • replicate intracellularly
  • resistance to many antibiotics
  • cannot be cultured by standard methods
59
Q

atypical pneumonia is caused by…

A
  • Mycoplasma pneumonia
  • Legionella pneumophillia
  • Chlamydophila pneumoniae
  • Chlamydophila psittaci
  • Coxiella burnetii
60
Q

how are anaerobes treated?

A

metronidazole

61
Q

C. botulinum

A
  • causes botulism
  • usually food-bourne, from improper storage
  • neurotoxin - prevents release of ACh
  • causes symmetrical flaccid descending paralysis
  • oculomotor muscles - dysphagia, respiratory depression
  • clinical use in BOTOX

microorganisms (1 decks)

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