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Microbiology > Other Gram-negative Rods > Flashcards

Other Gram-negative Rods Flashcards

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1
Q

What do all gram negative rods have in common❓

A
  • Gram -ve cell envelop
  • Lipopolysaccharides LPS (virulence factor)
  • Aerobic- cause infection in sites of high oxygen tension eg lungs
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2
Q

Mention one way gram negative rods can be classified

A 
1. 
Primary pathogens of human respiratory tract: 
Haemophilus 
Bordetella 
Legionella
  1. Opportunistic pathogen:
    Pseudomonas
3. 
Primary pathogens of animals:
Brucella 
Francisella 
Pasteurella
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3
Q

What do you know about haemophilus influenza❓

A

It is pleomorphic

It has a capsule (virulence factor)

Pathogen of young children

Illnesses are sporadic in occurrence

Normal component of upper respiratory tract flora (conjunctiva, genital tract)

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4
Q

Haemophilus influenza…

  1. Is transmitted by❓
  2. Can cause which diseases❓
A
  1. Respiratory droplets
2. 
If colonization occurs in respiratory tract: 
Otitis media 
Sinusitis 
Epiglottitis 
Bronchopneumonia

If it invades the bloodstream and localizes in other areas of the body:
Meningitis
Septic arthritis
Cellulitis

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5
Q

Haemophilus influenza is the leading cause of bacterial meningitis

True or false❓

A

True

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6
Q

Clinically H. influenza meningitis is indistinguishable from other purulent meningitides

True or false

A

True

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7
Q

How would you diagnose an infection caused by H.influenza❓

A

Culture on chocolate agar

Isolation from sterile sites eg blood, CSF, synovial fluid

In meningitis:
gram staining of CSF reveals:
Pleomorphic
Gram -ve coccobacilli 
Capsule (capsular swelling/quellung rxn/immunoflourescence staining)

Capsular antigen may be detected using:
Latex agglutination
Countercurrent immunoelectrophoresis
Radioimmune assay

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8
Q

While diagnosing a case of H. influenza infection, isolation from pharyngeal cultures may be inconclusive

True or false❓
Why❓

A

True

H. influenza is found normally around the respiratory tract

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9
Q

How can you prevent an infection caused by H.influenza❓

A

Immunization <2yrs (type B)

Rifampin for individuals in close with infected pt

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10
Q

Bordetella pertussis causes which disease❓

A

Small
Encapsulated coccobaccili
Grow singly or in pairs

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11
Q
  1. What disease does bordetella pertussis cause❓
  2. How is transmitted❓
  3. In the absence of Immunization, it is most common in which age group❓
  4. What is the incubation period of B. pertussis❓
A

Whooping cough

Droplets via coughing

Ages 1-5

1-3weeks

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12
Q

Describe the pathogenesis of infections caused by bordetella pertussis

A 
Binds to ciliated epithelium in URT
⬇️
Production of toxins and other virulent factors 
⬇️
Interference with ciliary activity 
⬇️
Death of cells
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13
Q

The disease can be divided into phases, what are they❓

A 
Catarrhal Phase:
Fever/Malaise 
Rhinorrhea
Mild conjunctivitis 
Dry/non-productive cough

Paroxysmal Phase:
Exacerbated cough followed by whoop w large mucus production

Convalesce Phase (3-4weeks, severe in infants)

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14
Q

How can an infection by B. pertussis be

  1. Prevented❓
  2. Diagnosed❓
  3. Treated❓
A
  1. Vaccine (DPT) at 2months old

2.
Clinical presentation

Culture from nasopharynx in a selective agar medium (pinpoint colonies in 3-6 days) has

Direct fluorescent antibody test

Serologic antibody test

2. 
Erythromycin 
🚫
⬇️
Trimethoprim-Sulfamethoxazole
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15
Q

Describe the legionella genus

A

*Cells are unencapsulated
Coccobacillary in shape

Facultative intracellular species

Aerobic and fastidious

*Require L-cysteine

Cause primarily respiratory tract infections

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16
Q

An infection by Legionella is an atypical, acute lobar pneumonia with multisystem symptoms.

  1. How can it be acquired❓
  2. What are it’s two distinct presentations❓
  3. Has an incubation period of❓
  4. Can be diagnosed by❓
  5. Can be treated using❓
A
  1. Aspiration of water containing legionella

Inhalation of contaminated aerosol

  1. Legionnaires diseases
    Pontiac Fever

2-10days

  1. Culture:
    Respiratory secretions using buffered charcoal yeast (pH 6.9), L-cysteine and iron
    Visible colonies in 3-5days

Urinary antigen test

  1. Erythromycin/Azithromycin
    Fluoroquinolones

🚫antibiotics for Pontiac fever

17
Q

Describe pseudomonas aeruginosa

A

Motile (polar flagella)
Encapsulated
Obligate aerobe
⬇️Nutritional requirements

Ubiquitous

Opportunistic pathogen (found in immunocompromised pt)

Causes nosocomial: 
Pneumonia, 
UTI, 
Surgical site infections, 
Severe burn infections, 
Infection of chemotherapy/antibiotics therapy patients
18
Q

Describe the pathogenesis of infections caused by pseudomonas aeruginosa

A

Attachment to tissue (pili)
⬇️
Colonization of tissue (capsule prevents removal by normal clearance mechanisms)
⬇️
Damage (toxins promote invasion and dissemination)

19
Q

Infections reflecting systemic spread of P. aeruginosa include❓

Why is there a complication in choice of therapy for P. aeruginosa infections❓

A

1.
Bacteremia

Secondary pneumonia

Bone and joint infections

Endocarditis

CNS/Skin/Soft tissue infections

  1. It is often antibiotic resistant
20
Q

How can infection by pseudomonas aeruginosa be identified❓

How can it be treated❓

A

1.
Fruity odor at bedside/lab

Isolation in blood/MacConkey agar

Serologic typing

  1. Aggressive antimicrobial therapy
21
Q

Describe the brucella genus

A

Zoonosis; B. ovis causes disease in man

Unencapsulated*
Small coccobacilli
Arranged singly or in pairs
LPS (virulence factor)

Aerobic
Facultative
Intracellular parasites

22
Q

How can infection by B. ovis be identified❓

How can it be treated❓

A
  1. •Detailed history/Patients occupation/Exposure to animals/Food intake

•Culture (examine for up to one month)
Plated materials: colonies in 4-5days Blood: relatively longer

  1. Doxycycline and Gentamycin/Streptomycin

Prolonged treatment (6 weeks) to prevent relapse

23
Q

Describe the pathogenesis of B. Ovis infection

A

Gain of entry (cuts/abrasions in skin/GI)
⬇️
Transport via lymphatic system
⬇️
Multiplication in regional lymph nodes
⬇️
Transmission to organs of reticuloendothelial system

24
Q
  1. What disease does B. ovis cause❓
  2. How is transmitted❓
  3. What is the incubation period of B. pertussis❓
A

1.
Undulant Fever

2.
Contact with infected tissue
Ingestion of unpasteurized milk
Inhalation of infected aerosols

5 days to several months

25
Q

Drugs that decrease gastric acidity may increase the likelihood of transmission of B. ovis via the GI route

True or false

A

True

26
Q

What do you know Francisella Tularensis infection

A

Zoonosis

Small
Pleomorphic coccobacilli
Lipid-rich capsule

Obligate aerobes
Facultative intracellular parasites

27
Q
  1. What disease does Francisella Tularensis cause❓
  2. How is transmitted❓
  3. What are the symptoms associated with its infection❓
A

1.
Contact w infected animal tissue (birds/household pets)

Bite of an infected antropod

2.
Fever/Malaise/Headache/Anorexia/Fatigue

28
Q

What are the risk factors associated with Francisella Tularensis❓

A

Summer months

> Males

Occupational risk for veterinarians, domestic livestock workers, hunters

Recreational activities w increased exposure to ticks/biting flies

29
Q

Why is Francisella Tularensis a potential biological weapon❓

A

It’s one of the most infectious pathogenic bacteria known; requires inoculation of as few as ten organisms to cause disease

30
Q

Describe the pathogenesis of a Francisella Tularensis infection

A 
Cutaneous inoculation
⬇️
Multiplication for 3-5days
⬇️
Spread to local lymph node
⬇️
Spread to various organs or tissues
31
Q

How can infection by Francisella Tularensis be diagnosed❓

How can it be treated❓

A
  1. No specific test for turalemia

Clinical presentation

History

Culture:
🚫blood
Nutritional requirement of sulfhydryl (cysteine)

  1. Streptomycin
    Gentamycin
32
Q

Describe the genus Bartonella

A

Facultative

Intracellular parasites

33
Q

Bartonella quintana…

  1. Causes what disease❓
  2. Is spread through what vector❓
  3. Is diagnosed using❓
  4. Is treated using❓
A
  1. Trench Fever (Mild, relapsing fever with maculopapular rash
  2. Human body louse
    * associated with poor hygiene
  3. Culture and serological tests
  4. Broad spectrum antibiotics
34
Q

Bartonella henselae…

  1. Causes what disease❓
  2. Is treated using❓
A
  1. Small abscesses at sources of scratch or bite

Fever
Localized lymphadenopathy

Bacillary angiomatosis

  1. Rifampin and doxycycline in immunocompromised pts
35
Q

Pasteurella multocida…

  1. Can be described as❓
  2. Is transmitted by❓
  3. Can cause which diseases❓
  4. Is diagnosed using❓
  5. Is treated using❓
A
  1. Coccobacilli/rods

Exhibit bipolar staining

With some encapsulated strains

Aerobes/Facultative aerobes

Capsule and endotoxins (virulence factors)

2.
Infected animal linking a wound
Cat scratch
Animal bite

3. 
Fever
Acute, painful cellularitis 
Soft tissue infections 
Lymphangitis
Lymphadenitis 
Osteomyelitis/Arthritis
  1. Clinical history
    Culture on blood agar
  2. Wounds should be cleaned, irrigated and debrided

Surgical drainage for deep-seated infections

Prolonged antibiotic Rx using Penicillin

Microbiology (11 decks)

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