Pathogenic Bacteria Flashcards

1
Q

Staph aureus? Characteristics?

A

Gram positive cocci:
- abscess-forming bacteria
- can also cause internal infection at joints, discs, pneumonia and infective endocarditis
- can also live harmoniously
- sticks well to prostheses
Coagulase enzyme +ve:
- converts fibrinogen to fibrin (clotting - camouflage)
- resistant to penicillin due to beta-lactamase presence

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2
Q

Common shapes of bacteria? Description?

A

Cocci:
+ve; circular with peptidoglycan layer
-ve; circular with lipopolysaccaride layer

Rod:
+ve; long rod-shaped peptidoglycan later
-ve; long rod-shaped lipopolysaccardie layer

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3
Q

Cocci? Gram classifications? Examples?

A

+ve: strep and staphy

-ve: neisseria meningitidis/gonorrhea and moraxella catarrhalis

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4
Q

Rods? Gram classifications? Examples?

A

+ve: listeria, clostridium difficile/botulinium/perfringens/tetani and bacillus anthracis
-ve: salmonella, E.coli, campylobacter, shigella, pseudomonas, haemophilus influenza and bacteriodetes

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5
Q

Antibiotics? Ranges? Examples?

A

Broad spectrum: eliminates all bacteria (good and bad)
Narrow spectrum: eliminates a specific type of bacteria

Gentamycin: -ve rods
Coamoxiclav: +ve cocci and -ve rods
Amoxicillin: +ve cocci

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6
Q

Streptococci? subtypes?

A

alpha-haemolytica: (turn blood agar green) pneumoniae; causes infective endocarditis
beta-haemolytica: (urn blood agar clear) A-G

Strep throat: can cause rtheumatic/scarlet fever
- abs cross react with the tissue causing problems

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7
Q

Beta-haemolytic streptococci? subtypes, characteristics and examples?

A

A: pyogenes; sore throat and necrotising fasciitis
B: agalactiae; neonatal sepsis (meningitis), carried in genital tract
D: enterococcus faecalis; non-haemolytic in gut but can cause UTI

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8
Q

Clostridium difficile? Characteristics?

A
  • Present in healthy gut (+ve)
  • causes of diarrhoea (toxin production)
  • increased risk with antibiotic use (disrupt gut flora)
  • detect by ELISA
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9
Q

Clostridium perfringens? Characteristics?

A
  • present in soild and commensal in human gut and faeces
  • pathogenic in food casuing food-poisoning (enterotoxin)
  • cause gangrene
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10
Q

Clostridium tetani? Characteristics?

A
  • toxins cause tetanus (uncontrolled msucle spams due to loss of inhib at NMJ
  • modified toxin used for immunisation
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11
Q

Neisseria meningococcus? Characteristcs?

A
  • causes meningitis (inflammed meninges)
  • important when isolated from a sterile site (CSF)
  • PCR available
  • ve
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12
Q

Neisseria gonorrhoeae/ Characteristics?

A
  • causes urethritis (men) and pelvic inflam (women)
  • sexual contact
  • ve
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13
Q

Moraxella catarrhalis? Characteristics?

A
  • cause resp tract infect
  • especially in underlying lung pathology
  • ve
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14
Q

E.coli? Characteristics?

A
  • human and animal reservoirs
  • virulence mech via pili, capsule, endo.exotoxins produced
  • ferments lactose
  • 160 serotypes
  • cause UTIs
  • Enterotoxogenic: traveller’s diarrhoea
  • Enterohaemorrhagic: bloody diarrhoea
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15
Q

Salmonella enterica? Characteristics?

A
  • self limiting enterocolitis with or without diarrhoea

- 2nd most common cause of bacteria diarrhoea

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16
Q

Salmonella typhi? Characteristics?

A
  • causes typhoid fever
  • fever and constipation
  • vaccine available
17
Q

Shigella? Characteristics?

A
  • causes diarrhoea and dysentery

- travel related

18
Q

Campylobacter? Characteristics?

A
  • microaerophilic (low o2)
  • source from domesticated animals and chickens
  • faecal-oral route
  • foul smelling then bloody diarrhoea
19
Q

Helicobacter pylori? Characteristics?

A
  • normal commensal in human gut

- damages mucosa and causes ulcers

20
Q

Haemophilus infleunzae? Characteristics?

A
  • cocco-bacilli apperance
  • resp tract infection
  • capsulate form
21
Q

Pseudomonas? Characteristics?

A
  • water and soil organisms
  • contaminate medical equipment
  • hospital acquired causes of sepsis
  • resp infection in CF
  • sensitive to limited range of antibiotics
22
Q

Oral anaerobes? Examples?

A
  • Prevotella
  • Porphyromonas
  • Pasteurella
  • Capnocytophyga
23
Q

Mycobacterium tuberculosis? Characteristics?

A
  • TB
  • link HIV
  • non and TB version of mycobacterium
24
Q

Leprosy? Characteristics?

A
  • Mycobacterium leprae

- attacks peripheral nerves

25
Q

Spirochaetes? Characteristics?

A
  • long spiral shaped bacteria
  • not easily culturable
  • diagnosed by serology
26
Q

Syphilis? Characteristics?

A
  • Primary syphilis: non-painful skin lesion (chancre) at the site of infection (skin or mucous membranes)
  • Secondary syphilis (6-8 weeks after primary symptoms): generalised systemic illness and rash
  • Latent phase: symptomatic episodes may occur
  • Tertiary syphilis (years after primary symptoms): central nervous system
  • Congenital syphilis: stillbirth, neonatal death or disease
  • Diagnosis – serology, nucleic acid amplification tests (NAAT)
  • Management – antibiotics, contact tracing and screening, antenatal screening
27
Q

Lyme disease? Characteristics?

A

Transmitted by ticks

  • Stage 1: Skin rash (erythema chronicum migrans) appears at the site of the tick bite
  • Stage 2: Systemic illness occurs in some patients weeks or months later when patients suffer cardiac or neurological and musculoskeletal symptoms
  • Stage 3: Chronic disease, occurring years later when patients present with chronic skin, nervous system or joint abnormalities
  • Diagnosed by clinical assessment and serology (antibody detection)
28
Q

Leptospirosis? Characteristics?

A
  • Infects animals and concentrates largely in the kidneys
  • Spread is via infected urine and other body fluids and tissues
  • At-risk groups:
    sewerage workers
    watersports
  • Range of clinical presentations:
    Weil’s disease – febrile illness with systemic upset, liver and renal failure, aseptic meningitis, 10 % mortality
29
Q

Chlamydia? Characteristics?

A
  • Obligate intracellular bacteria
  • Culture only in cell lines (do not grow on agar)
  • Respiratory Infection:
    Chlamydophila pneumoniae
    Chlamydophila psittaci (psittacosis)

Ophthalmic and genital tract infection
Chlamydia trachomatis:
- Trachoma (tropical eye infections)
- Genital and neonatal infection

Diagnosis of Chlamydia trachomatis:
- nucleic acid amplification tests (NAAT) on first void urine or vulval/vaginal swabs