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Foundation 2 > Medically Important Bacteria > Flashcards

Medically Important Bacteria Flashcards

1
Q

Staphylococcus aureus properties

A
  • Gram + cocci that occur in clusters
  • Golden yellow colonies on agar
  • Catalase and coagulase positive
  • Anaerobe
  • Normal flora of humans found in nasal passages, skin and mucous membranes
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2
Q

Staphylococcus aureus diseases

A
  • skin infections, such as pimples, impetigo, boils, cellulitis, folliculitis, scalded skin syndrome and abscesses
  • life threatening diseases like pneumonia, meningitis, osteomyelitis, endocarditis, TSS, septicaemia, food poisoning
  • Post surgical wound infections
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3
Q

Staphylococcus aureus virulence factors

A
  • Coagulase: causes clots
  • Invasins: promote bacterial spread in tissues (eg. Hyaluronidase, leucocidin, kinases)
  • Haemolysins
  • Exotoxins: exfoliative toxin, toxic shock syndrome toxin, entrotoxin
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4
Q

Streptococcus pyogenes properties

A
  • Gram + cocci that occurs in chains

* Produces large zones of beta haemolysis on blood agar

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5
Q

Streptococcus pyogenes infections

A
  • Sore throats, tonsillitis
  • Cellulitis, impetigo
  • Bactremia
  • Endocarditis
  • Toxin mediated scarlet fever and toxic shock syndrome
  • Immune mediated/post streptococcal disease - rheumatic fever, rheumatic heart disease, glomerulonephritis
  • Sinusitis
  • Necrotising fasciitis
  • Poststreptococcal glomerulonephritis
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6
Q

Streptococcus pyogenes virulence factors

A
  • Hyaluronidase: breaks down hyaluronic acid, enabling bacterial spread
  • Cell wall antigens: capsular polysaccharide, peptidoglycan, lipoteichoic acid
  • Streptokinase: digests clots
  • Streptolysins: cause beta hemolysis
  • DNAses: liquefaction of pus, generate substrate for growth
  • M protein (in fimbriae) : facilitate attachment to various host cells
  • Erythrogenic toxin: scarlet fever
  • Pyrogenic toxin: STSS (streptococcal toxic shock syndrome)
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7
Q

Streptococcus pneumoniae properties

A
  • Gram + cocci that occurs in pairs
  • Often capsulate
  • Aerobic, anaerobic respiration
  • Alpha haemolytic on blood agar
  • Produce draughtsman colonies
  • Catalase negative
  • Bile soluble
  • Susceptible to optochin
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8
Q

Streptococcus pneumoniae infections

A
  • Bronchopneumonia
  • Lobar pneumoniae
  • Meningitis
  • Bacteraemia
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9
Q

Streptococcus pneumoniae virulence factors

A
  • Capsule
  • Pili: colonisation of upper respiratory tract
  • PspA surface protein: inhibits complement activation, binds lactoferrin, inhibits uptake to phagocytes
  • LytA, B, C: autolysins
  • CbpA: adhesin, which is choline-binding protein
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10
Q

Gram positive bacilli (aerobes) examples

A
  • Bacillus anthracis

* Bacillus cereus

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11
Q

Bacillus anthracis properties

A
  • Spore forming
  • Causative form of anthrax (infection affecting skin, lungs, intestines, injection)
  • Soil organisms
  • Humans acquire infection when spores enter skin or when inhaled
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12
Q

Bacillus cereus properties

A
  • Spore forming
  • Causes food poisoning (reheated rice, pulses)
  • Cause Bacteraemia in immunocompromised
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13
Q

Gram positive bacilli (anaerobes) examples

A
  • Clostridium tetani (tetanus)
  • Clostridium botulinum (botulism)
  • Clostridium difficile (colitis)
  • Clostridium perfringes (gas gangrene)
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14
Q

Clostridium tetani properties

A
  • Spore forming with terminal spore (drumstick)
  • Humans acquire infection by contaminated soil entering wound
  • Grows on blood agar under anaerobic conditions, giving ground glass appearance
  • Causes tetanus, convulsive contractions of voluntary muscles
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15
Q

Clostridium perfringes properties

A
  • Gas gangrene resulting from dirty wounds

* Food poisoning following ingestion of food contaminated with enterotoxin producing strains

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16
Q

Clostridium perfringes virulence factors

A
  • Toxins

* Tissue destroying enzymes

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17
Q

Clostridium difficile properties

A
  • Component of gut flora
  • Flourishes under selective pressure of antibiotics
  • Pseudomembranous colitis or antibiotic associated diarrhoea
  • Fatal in the immunocompromised
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18
Q

Corynebacterium diphtheriae properties

A
  • Gram + bacilli
  • Non spore forming
  • Cells arranged as Chinese letters or pallisades
  • Causes diphtheria
  • Caused by toxigenic strains only
  • Infects throat and skin
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19
Q

Corynebacterium diphtheriae virulence factors

A
  • Diphtheria toxin: inhibits protein synthesis by inactivating elongation factor
  • Pili
20
Q

Diphtheria condition properties

A
  • Upper respiratory tract illness
  • Sore throat, Low fever
  • Adherent membrane (pseudomembrane on tonsils, pharynx)
  • Diphtheria toxin: myocarditis, polyneuritis
21
Q

Lab diagnosis for diphtheria

A
  • Gram staining
  • Blood tellurite medium
  • ELEK test
  • PCR to detect DNA seq encoding toxin
22
Q

ELEK test

A
  • Production of diphtheria toxin detected within 18 to 48 hours
  • Formation of toxin-antitoxin precipitin band on agar
23
Q

Gram negative diplococci examples

A
  • Neisseria gonorrhoea (gonorrhoea)

* Neisseria meningitidis (meningitis)

24
Q

Neisseria gonorrhoea properties

A
  • Kidney shaped, diplococci
  • Causes gonorrhoea
  • In females: pelvic inflammatory disease, salpingitis
  • In infants: ophthalmia neonaturm (neonatal conjunctivitis)
  • Can be carried in anus, nasopharyngeal tract, genital tract
25
Q

Gonorrhoea treatment

A
  • Beta-lactamase stable cephalosporin
  • Amoxycillin
  • Ampicillin
26
Q

Gonorrhoea prevention

A
  • Condoms
  • Education
  • Contact tracing
  • Treatment
27
Q

Gram negative bacilli main examples

A
  • Salmonella typhi (typhoid fever)
  • Salmonella paratyphi A, B, C (paratyphoid fever)
  • Shigella dysentriae, Shigella sonnei, Shigella flexneri, Shigella boyii (bacillary dysentery)
28
Q

Gram negative bacilli other examples

A
  • Eschericha coli
  • Klebsiella pneumoniae
  • Proteus sp
  • Pseudomonas aeruginosa
29
Q

Escherichia coli properties

A
  • Gram negative rod
  • Motile
  • Most strains are harmless
  • Live in gut of man and animals
  • Spread by fecal oral route
  • Grows on MacConkey agar, produce pink colonies indicating that it is lactose fermenter
30
Q

Escherichia coli virulence factors

A
  • Adhesins: P fimbriae, S fimbriae, Type 1 fimbriae
  • Invasins: haemolysins, shigella like Invasins
  • Toxins: endotoxins (LPS), shigella like toxins, cytotoxins, ST toxin, LT toxin
  • Antiphagocytic and defence against immune responses: capsules, K-antigen, LPS
31
Q

Salmonella properties

A
  • Predominantly motile
  • Can survive for weeks outside the body
  • May cause bacteraemia
32
Q

Salmonella transmission

A
  • Humans to animals and vice versa
  • Encountered in food chain
  • Acquired by ingestion of contaminated food via fecal oral route
33
Q

Gram negative comma shaped bacteria examples

A
  • Vibrio cholerae (cholera)
  • Vibrio parahaemolyticus (haemolyses RBCs)
  • Vibrio vulnificus (wound infections, bacteraemia)
34
Q

Vibrio cholerae properties

A
  • Highly motile using single flagellum

* Virulence factors: mucinase, adhesins, enterotoxin

35
Q

Gram negative curved or spiral shaped bacteria examples

A
  • Campylobacter foetus: bacteraemia

* Helicobacter pylori: gastritis, gastric ulcer, gastric carcinoma

36
Q

Helicobacter pylori virulence factors

A
  • Protease which affects stomach mucosa

* Urease which produces ammonia, buffers stomach acid

37
Q

Gram negative bacilli examples (2)

A
  • Bordetella pertussis (whooping cough)
  • Haemophilus influenza (meningitis, sinusitis, upper respiratory infections)
  • Yersinia pestis (plague)
  • Legionella pneumophila (pneumonia)
38
Q

Mycoplasma properties

A
  • Lacks a cell wall

* Cannot be acted on by beta lactam antibiotics

39
Q

Mycoplasma examples

A
  • Mycoplasma pneumoniae (pneumonia)
  • Mycoplasma genitalum (pelvic inflammatory disease)
  • Mycoplasma hominis (pelvic inflammatory disease)
40
Q

Mycoplasma hominis properties

A

• Growth of “fried egg” colonies on glucose agar medium within 24-48 hours

41
Q

Mycoplasma pneumoniae virulence factors

A
  • Produce Community Acquired Respiratory Distress Syndrome (CARDS) toxin
  • Aids in colonisation and pathogenic pathways leading to inflammation and airway dysfunction
42
Q

Mycobacterium properties

A
  • Gram stain with difficulty because of mycolic acids

* Ziehl-Neelsen stain

43
Q

Mycobacteria examples

A
  • Mycobacterium tuberculosis (tuberculosis)
  • Mycobacterium leprae (leprosy)
  • Mycobacterium other than tuberculosis MOTT: range of illnesses in the immunocompromised (M. Avium)
44
Q

Mycobacterium tuberculosis properties

A
  • Infects lung
  • Causes lesion in lung called Ghon’s complex
  • Transmission: droplet infection
45
Q

Mycobacterium tuberculosis virulence factors

A
  • Grow intracellularly
  • Antigen 85 complex: bind fibronectin, aid in walling bacteria off from immune system and facilitate tubercle formation
  • Mycolic acids: prevent Attack of mycobacterium by phagocytes
  • High lipid conc in cell wall: resistance to antibiotics
  • Cord factor (glycolipid found in cell walls of mycobacteria): toxic to mammalian cells
46
Q

Treponema pallidum properties

A
  • Spirochaete (spiral-shaped bacteria)
  • Viewed by dark ground microscopy or immunoflourescence microscopy
  • Causative agent of syphilis
47
Q

Leptospira interrogans properties

A
  • Finely coiled spirochetes with hooked ends
  • Causes leptospirosis, kidney disease
  • Viewed by dark ground microscopy, immunoflourescence, light microscope

Foundation 2 (11 decks)

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