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microb - bacteria > Gram Positive Rods - Aerobic > Flashcards

Gram Positive Rods - Aerobic Flashcards

1
Q

Examples of aerobic GPRs

A
  1. Corynebacterium spp
    - Corynebacterium diphtheriae
    - Corynebacterium ulcerans, jeikeium & minutissimum
  2. Bacillus spp
    - Bacillus anthracis
    - Bacillus cereus
  3. Listeria monocytogenes
  4. Nocardia asteroides
  5. Others (lactobacillus, arcanobacterium haemolyticum, rhodococcus equi, erysipelothrix rhusopathiae)
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2
Q

Transmission of C. diphtheriae

A
  1. Respiratory droplets
  2. Aided by asymptomatic carriers
  • infects upp resp tract (throat, nasal mucosa, larynx, trachea), and skin (part of normal flora)
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3
Q

Clinical presentations of C. diphtheriae

A

Diphtheria

  1. Local effects
    - pseudomembrane formation (dirty white, becomes darker with time)
    - infected area becomes red & swollen, may result in airway obstruction & suffocation, or “bull neck” - swollen neck tissue
    - sternocleidomastoid & collapsing ribcage - sign of intense effort to draw in air
  2. Distant effects (toxin is absorbed)
    - myocarditis (arrhythmias, heart damage)
    - nerve damage (peripheral neuritis) resulting in muscle weakness incl resp muscles
  3. Non toxigenic strains cause pharyngitis, skin abscesses, invasive infections
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4
Q

Diagnosis of C. diphtheriae (2)

A
  1. Clinical - need for early treatment
  2. Culture, throat swabs on selective medium (Tinsdale’s) which suppresses normal flora
    - suspect colonies confirmed via sugar fermentation reactions
    - Elek plate test to check for toxigenicity (toxin production, indicated by precipitin line)
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5
Q

Treatment of C. diphtheriae (3)

A
  1. IV antiserum - Abs neutralize toxin before it can bind to & neutralise cells
  2. Erythromycin
  3. Supportive/symptomatic treatment for other complications, heart & resp failure
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6
Q

Prevention of C. diphtheriae (2)

A
  1. Vaccine: diphtheria toxin chemically modified - toxoid
    - immunization programmes effectively eliminate disease in the community
    - secondary cases occur in older patients whose immunity has declined with time
  2. Protect contacts: administer diphtheria toxoid & prophylactic antibiotic
    - erythromycin clears throat colonisation in carriers
    - isolate pt until they are non infectious + immunise them
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7
Q

Clinical presentations of corynebacterium ulcerans

A
  1. Throat lesions resembling diphtheria

2. Diphtheria-like systemic illness

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8
Q

Features of corynebacterium jeikeium

A
  • often multiresistant, opportunistic, nosocomial infection

- can cause wound infections, infect implanted devices like replacement heart valves, IV lines

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9
Q

Clinical presentations of corynebacterium minutissimum

A
  • Causes erythrasma - fluoresces coral pink using Wood’s lamp
  • Sometimes invasive infections
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10
Q

Transmission of B. anthracis

A
  • Zoonosis, spores can be carried with animal products like bone meal & hides
  • infects animals
  • spores often visible within bacterium, resistant & can survive long
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11
Q

Virulence factors of B. anthracis (3)

A
  1. Antiphagocytic capsule (protein, not saccharide)
  2. Toxins
  3. Soluble factors - Protective antigen, edema factor, lethal factor (lyses macrophages)
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12
Q

Clinical presentations of B. anthracis (4)

A
  1. Cutaneous anthrax
    - spores introduced into the skin
    - forms eschars (central dark area) surrounded by a ring of vesicles & an area of edema which may spread
  2. Respiratory anthrax
    - spores inhaled, causes severe infection with hemorrhage
  3. Intestinal anthrax
    - eating meat of an infected animal
    - causes hemorrhagic diarrhea
  4. Septicaemia & death
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13
Q

Diagnosis of B. anthracis

A
  1. Culture - blood, vesicle fluid, sputum
    - grows well on blood agar aerobically
    - pink stained capsule (McFadyean’s stain)
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14
Q

Treatment of B. anthracis (2)

A
  1. Penicillin
  2. Ciprofloxacin
    - worry that a MDR strain may be used as biological warfare weapons (aerosol delivery is easy)
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15
Q

Transmission of B. cereus

A

Food poisoning - often from fried rice

  • bacterial spores survive boiling
  • contaminated cooked rice allowed to stand at room temp allows for spores to germinate & bacteria to grow & secrete toxin
  • preformed toxin is heat stable
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16
Q

Clinical presentations of B. cereus (2)

A
  1. Food poisoning
    - rapid onset - within 6h, due to pre-formed toxin, vomiting
    - slower onset - 8-24h, by enterotoxins formed in intestine, diarrhea & abdominal pain
  2. Wound & invasive infection eg post traumatic ophthalmitis
17
Q

Diagnosis of B. cereus

A

Culture from food/stool - grows well on blood agar aerobically

18
Q

Prevention of B. cereus

A
  1. Store cooked rice in refrigerator

2. Cook thoroughly

19
Q

Transmission of listeria monocytogenes

A
  • replicates in cold (even 4C)
  • GIT flora of animals
  1. Food borne (chilled foods, meat contaminated at slaughter)
20
Q

Clinical presentations of L. monocytogenes (3)

A
  1. Febrile gastroenteritis
  2. Infections in pregnancy & neonates
    - mother is usually asymptomatic/has flu-like illness
    - foetus may be aborted/induced premature labour/still birth/severely ill with multi system infection (granulomatosis infantisepticum) or go on to develop early onset neonatal listeriosis or late onset meningitis (acquired by cross infection in hospitals)
  3. Infections in other patients (usually immunosuppressed)
    - meningitis, febrile bacteremic sepsis, endocarditis
21
Q

Diagnosis of L. monocytogenes (3)

A
  1. Pregnancy/neonatal infections: Culture (blood, high vaginal swab, amniotic fluid, baby skin swabs)
  2. Meningitis: Culture (CSF, blood), CSF (changes in white cell count & chemistry)
  3. Beta hemolytic colonies grow aerobically on blood agar
22
Q

Treatment of L. monocytogenes

A
  1. Ampicillin +/- genatmicin

2. Resistant to all cephalosporins

23
Q

Features of nocardia asteroides

A
  1. Branching beaded filaments

2. Found in soil & other environmental sources

24
Q

Clinical presentations of nocardia asteroides (2)

A
  1. Nosocomial infections (developed countries)
    - usually opportunistic, in immunosuppressed, AIDS
    - lung infection followed by disseminated infection with abscesses in many organs including the brain + primary skin infections
  2. Non-opportunistic infections (tropical countries)
    - Madura foot: chronic destructive infection of bone & soft tissue following inoculation into the skin
25
Q

Diagnosis of nocardia asteroides

A
  1. Culture
    - sputum, pus - appears beaded as stain is not taken up so well
    - blood - slow growth
26
Q

Treatment of nocardia asteroides

A

Co-trimoxazole, long course of treatment

27
Q

Features of lactobacillus

A
  1. Normal flora of mouth, gut, vagina (more at puberty, low pH, protects)
  2. Dental caries (but S. mutans more crucial)
  3. possibly probiotic, helps in prevention & treatment of GI infections
28
Q

Clinical presentations of arcanobacterium haemolyticum

A
  1. Unusual cause of sore throat

2. May be accompanied by skin rash resembling scarlet fever

29
Q

Features of rhodococcus equi

A
  1. Opportunistic lung infection - in immunocompromised

2. From animals

30
Q

Features of erysipelothrix rhysopathiae

A
  1. Causes erysipeloid (a form of cellulitis with a blue-red discolouration of the skin)
  2. Typically in those who handle meat/fish

microb - bacteria (11 decks)

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