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Gram Negative Rods - Fastidious Flashcards

1
Q

Feature of fastidious GNRs

A
  1. Does not grow well on blood agar, requires more nutritious media eg Chocolate agar
  2. Usually sensitive to carbapenems, quinolones & 3G cephalosporins
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2
Q

Examples of fastidious GNRs

A
  1. Haemophilus spp
    - Haemophilus influenzae
    - Haemophilus ducreyi
  2. Legionella pneumophilia
  3. Klebsiella granulomatis
  4. Bordetella spp (B. pertussis, B. parapertussis)
  5. Brucella spp
  6. Pasteurella multocida
  7. Francisella tularensis
  8. Bartonella spp (B. bacilliformis, B. quintana, B. henselae & clarridgeiae)
  9. Yersinia spp
    - Yersinia pestis
    - Y. enterocolitica & pseudotuberculosis)
  10. Acinetobacter baumannii
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3
Q

Transmission of H. influenzae

A

Carried in the throat (esp non-encapsulated strains)

  1. Respiratory droplets
  2. Close contact
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4
Q

Virulence factors of H. influenzae

A
  1. Capsule (some strains)
    - types a-f, antigenically distinct polysacchardie capsules
    - H. influenzae type b (Hib) is the commonest cause of invasive disease
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5
Q

Clinical presentations of H. influenzae (3)

A
  1. Encapsulated infections (mostly young children w immunological immaturity)
    - meningitis, acute epiglottitis (breathing difficulty), septicaemia, cellulitis, pneumonia, osteomyelitis, septic arthritis
  2. Non-capsulated infections
    - invasive: meningitis & septicaemia (neonates), pneumonia
    - non-invasive: URTI (otitis media, sinusitis), acute exacerbation of COPD, conjunctivitis
  3. Brazilian purpuric fever (conjunctivitis - septicaemia resembling meningococcal disease)
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6
Q

Diagnosis of H. influenzae

A
  1. Culture
  2. Microscopy (CSF, joint fluid)
  3. Serotyping (less reliable)
  4. Molecular (less available)
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7
Q

Treatment of H. influenzae

A
  1. Ceftriaxone

2. Ampicillin/amoxycillin resistant as many strains produce beta lactamase

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8
Q

Prevention of H. influenzae (2)

A
  1. Conjugate vaccine (children, other at risk groups eg asplenia)
  2. Chemoprophylaxis (rifampicin) & Hib vaccine for prevention of secondary cases
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9
Q

Transmission of H. ducreyi

A

Sexually transmitted disease

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10
Q

Clinical presentations of H. ducreyi

A
  1. Chancroid (painful genital ulcers + enlarged inguinal lymph nodes that may suppurate & ulcerate)
    - anaerobic secondary infection of lesions may lead to gangrene & extensive destruction of genitalia
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11
Q

Diagnosis of H. ducreyi

A
  1. Culture - 70% sensitivity, special media req, ‘shoal of fish’ appearance
  2. PCR
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12
Q

Features of haemophilus spp

A
  • H. influenzae requires both X & V factors to grow, H. ducreyi only requires X factor
  • other Haemophilus species (found in upp resp tract flora) - occasionally cause bacterial endocarditis
  • part of HACEK group (fastidious GNRs associated with endocarditis) - H. parainfluenzae, aphrophilus - Actinobacillus actinomycetemcomitans - Cardiobacterium hominis - Eikenella corrodens - Kingella kingae
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13
Q

Transmission of legionella pneumophilus

A

Infectious aerosols from water source dispensers (cooling towers, hot water supplies, warm water in nebulisers & oxygen line humidifiers, whirlpool spa baths & showers)

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14
Q

Clinical presentations of legionella pneumophilus (2)

A
  1. Legionnaires’ Disease - severe pneumonia often accompanied by confusion & other extra pulmonary manifestations, mortality 10%, higher in hospital patients
  2. Pontiac fever - brief influenza-like illness, much less dangerous
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15
Q

Diagnosis of legionella pneumophilus (4)

A
  1. Immunofluorescent stain (sputum/broncheoalveolar lavage)
  2. Culture on B-CYE agar
  3. Urine antigen detection (only serogroup 1)
  4. Serology (only serogroup 1)
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16
Q

Treatment of legionella pneumophilus

A
  1. High dose IV erythromycin +/- rifampicin

2. Alternatively: fluoroquinolones, azithromycin

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17
Q

Transmission of klebsiella granulomatis

A

Sexually transmitted disease

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18
Q

Clinical presentations of klebsiella granulomatis

A
  1. Granuloma Inguinale/Donovanosis (STD)
    - subcutaneous nodules break down to painless ulcers
    - slow enlargement of ulcers w prominent granulation tissue, tissue loss & scarring
    - spread to inguinal region, causing periadenitis (pseudobubo) & pelvic fibrosis
19
Q

Diagnosis of klebsiella granulomatis

A
  • Tissue smears - “Donovan bodies” within macrophages

- do not culture, does not grow easily

20
Q

Transmission of bordetella

A

Respiratory droplets

21
Q

Clinical presentations of bordetella

A
  1. Whooping cough
    - Catarrhal stage: initially resembles other resp inf
    - Paroxysmal cough: lungs emptied in a series of coughs before finally dragging in a fresh breath through a narrowed throat (producing the whoop)
    - Paroxysmal stage may continue for several months
    - complications: subconjunctival hemorrhage
22
Q

Diagnosis of bordetella

A
  1. Perinasal swab (nasopharynx) for culture on Bordet-Gengou medium - mercury droplet colonies
  2. PCR
23
Q

Treatment of bordetella

A
  1. Erythromycin - reduces severity of illness if given before paroxysmal stage begins
  2. Long course of antibiotic - makes pt less infectious/prevent infection in contacts
24
Q

Prevention of bordetella

A
  1. Vaccines - both whole killed cell & acellular type vaccines available
    - acellular - less side effects but short lived immunity
    - reimmunise family members to prevent carriage in close contacts before birth
25
Q

Transmission of brucella

A

Zoonosis, direct contact/by consuming infected meat, milk, milk products - infects a variety of farm & wild animals

26
Q

Clinical presentations of brucella

A
  1. Brucellosis
    - acute febrile illness, PUO
    - chronic brucellosis - low grade fever + malaise
    - bone & joint symptoms, other focal infections
27
Q

Diagnosis of brucella (2)

A
  1. Blood cultures

2. Serology (rising antibody titre)

28
Q

Treatment of brucella

A

Doxycycline + streptomycin

+ rifampicin for osteomyelitis

29
Q

Prevention of brucella (2)

A
  1. Selective slaughter & vaccination - eliminate infection from farm animals
  2. Pasteurise milk
30
Q

Transmission of pasteurella multocida

A

Animal bites (found in mouth & throat of man species of animals)

31
Q

Clinical presentations & treatment of pasteurella multocida

A
  1. Local infections
  2. Penicillin
  3. Co-amoxiclav (anti-anaerobe) - many infected bites are polymicrobial so wider spectrum antibiotic cover is needed
32
Q

Transmission of francisella tularensis

A

Naturally infects animals like rabbits, rodents, sporadically infects man

Handling infected animal carcasses, arthropoda bites eg in hunters

33
Q

Clinical presentations of francisella tularensis

A
  1. Tularaemia - local infection of skin/eye/lymph nodes, septicaemia, pneumonia
34
Q

Transmission & clinical presentations of Bartonella bacilliformis

A
  • spread by sandflies in mountainous regions of South America
  • Oroya fever (high fever + severe anemia, often fatal), verruca peruana (a characteristic skin rash)
35
Q

Transmission & clinical presentations of Bartonella quintana (3)

A
  • spread by body louse
  • Trench fever (fever, chills, malaise, myalgia, rash, shin pain)
  • AIDS related conditions (bacillary angiomatosis, bacillary peliosis - lesions in liver & spleen)
  • Endocarditis - unusual
36
Q

Clinical presentations of Bartonella henselae (2)

A
  • Cat scratch disease (fever + local lymphadenopathy) (also in B. clarridgeiae)
  • AIDS related conditions, endocarditis
37
Q

Diagnosis of bartonella

A
  1. PCR
  2. Serology
  3. Histology
  4. Culture
38
Q

Transmission of yersinia pestis

A
  1. Zoonosis (bite of rat flea)

2. Droplet spread (infection of rodents)

39
Q

Clinical presentation of yersinia pestis

A
  1. Plague
    - local lymph node infected - develops painful swelling = bubo formation - invasion of bloodstream - septicaemia
    - spread to lungs - pneumonic plague (fatal & infectious)
40
Q

Diagnosis of yersinia pestis (2)

A
  1. Microscopy

2. Culture of sputum/pus/blood - safety pin appearance

41
Q

Clinical presentations of Y. enterocolitica & Y. pseudotuberculosis (3)

A
  1. Gastroenteritis
  2. Mesenteric lymphadenitis, terminal ileitis
  3. Septicaemia (sometimes fatal)
42
Q

Diagnosis of Y. enterocolitica & Y. pseudotuberculosis (2)

A
  1. Culture from stool/tissue samples/blood

2. Serology

43
Q

Features of acinetobacter baumannii

A
  • environmental, part of normal skin flora, opportunistic pathogen
  • nosocomial pneumonia
  • ICU patients at high risk
  • often MDR - untreatable, CRABs (completely resistant acinetobacter)
44
Q

Features of bacterial vaginosis (4)

A

Disturbance to flora

  1. pH > 4.5
  2. smell
  3. clue cells
  4. Treat with metronidazole

microb - bacteria (11 decks)

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