Respiratory Tract Bacteria

Front 1

What is a capsule and what is the significance of having one?

Back 1

A capsule is a lipopolysaccharide (LPS) barrier surround certain bacteria that confers immune resistance through various mechanisms, one being the hiding of classic antigens on the bacterial surface. Also inhibits complement attachment and phagocytosis, allowing for survival in blood stream.

Front 2

What are the common encapsulated respiratory tract pathogens?

Back 2

- Streptococcus pneumoniae
- Haemophilus influenza
- Neisseria meningitidis

Front 3

Streptococcus pneumoniae: Characteristics

Back 3

- gram positive
- diplococcus
- alpha hemolytic
- catalase negative

Front 4

Pathology

Back 4

- Colonizes URT in over 50% of children
- Becomes virulent when transmitted to normally sterile spaces
- pneumonia
- otitis media
- sepsis (blood)
- meningitis

Front 5

Resistance mechanisms

Back 5

- Capsule (over 90 unique types)
- Altered penicillin-binding proteins (PBPs) reduce affinity for penicillins
- We tend to overuse antibiotics against pneumococcus.

Front 6

Haemophilus influenzae: characteristics

Back 6

- gram negative
- coccobacillus
- Most isolates are unencapsulated (non-typeable). Type B encapsulated isolate causes more serious infections

Front 7

Diseases Caused by both non-typeable and Type B (Hib):

Back 7

Otitis media
Sinusitis
Chronic bronchitis
Pneumonia

Front 8

Diseases caused by (Hib):

Back 8

Bacteremia
Cellulitis
Epiglottitis
Meningitis

Front 9

When does H. influenzae most commonly cause infection (what age)?

Back 9

Early childhood (< 2 yrs) due to lack of immune system development

Front 10

Treatment of H influenzae:

Back 10

penicillins

Front 11

Neisseria meningitidis: Common Characteristics

Back 11

- Gram negative
- bean shaped diplococcus
- prominent antiphagocytic polysaccharide capsule

Front 12

Pathology

Back 12

- Carriage in URT is common (>20%)
- Causes 2 distinct syndromes: meningococcemia (sepsis) and meningitis
- Does NOT cause pneumonia
- Invasive disease is infrequent but can occur in outbreaks

Front 13

Treatment

Back 13

penicillins or third generation cephalosporin

Front 14

Conjugate vaccines against encapsulated respiratory pathogens

Back 14

- polysaccharide antigens conjugated to protein carriers
- Vaccines against:
- Hib
- S. pneumoniae (13-valent)
- N. meningitidis (4-valent)

Front 15

Other pathogens of the human respiratory tract:
(not encapsulated)
(not part of normal resp. tract flora)

Back 15

- Bordetella pertussis
- Mycoplasma pneumoniae
- Pseudomonas aeruginosa
- Legionella pneumophilia

Front 16

Bordetella pertussis: Characteristics

Back 16

- gram-negative
- coccobacillus
- aerobic

Front 17

Pathology

Back 17

- infects upper respiratory tract
- Whooping cough
- pertussis toxin: promotes respiratory secretions and reduced phagocytic activity
- tracheal cytotoxin: inhibits ciliary beating
- highly contagious
- Can last up to three months: "the hundred day cough"
- high mortality in first 6 months of life

Front 18

Diagnosis

Back 18

Culture from nasopharyngeal swab

Front 19

Treatment

Back 19

Erythromycin or macrolides.
- Usually treatment is too late because toxin-mediated damage has already occurred. Still, treatment is important to prevent spread.

Front 20

Mycoplasma pneumoniae: characteristics

Back 20

- lacks a cell wall (won't take up gram stain)
- not killed by Beta lactams

Front 21

Pathology

Back 21

- Causes "atypical" pneumonia that is called "walking pneumonia" to due lesser degree of severity
- Interstitial infiltrates in multiple lobes

Front 22

pseuomonas aeruginosa: characteristics

Back 22

- gram negative rod
- aerobic, motile with flagella

Front 23

pathology

Back 23

- ubiquitous and opportunistic
- takes advantage of host compromise

- pulmonary: pneumonia, lung infection in CF patients
- skin infections: hot tub folliculitis, burn infection
- otitis externa (swimmer's ear)
- bacteremia: vascular catheter infections

Front 24

Resistance mechanisms

Back 24

Resistance is MAJOR problem:
- forms biofilms
- Beta lactamases
- porin mutation reduces uptake

Front 25

Treatment

Back 25

- Combinations of anti-biotics
- 4th generation cephalosporins, fluoroquinolones

Front 26

Legionella pneumophila: characteristics

Back 26

- gram negative small coccobacilli
- motile (flagella)
- does not grow on routine media
- parasite of aquatic protozoa (amoebae)
- falsely recognize lung macrophages for its natural host
- intracellular parasite

Front 27

Pathology

Back 27

- Outbreaks associated with water systems
- 2 distict forms of disease:
- Legionnaires' disease: cough, high fever, pneumonia, multi-system complications, 15% mortality
- Pontiac fever: acute flu-like illness

Front 28

Diagnosis

Back 28

- fluorescent antibody stain
- urine antigen test

Front 29

Treatment

Back 29

- macrolides, fluoroquinolones
- antibiotics must be able to penetrate host cell