3.6.2. Bacteria Upper Respiratory Infections

Question 1

How can you tell the difference between a bacterial and viral infection?

Answer 1

With a viral infection:

• there is more nasal discharge
• less likely to have a fever
• paucity of clinical findings but notable discomfort

With a bacterial infection:

• More erythema, swelling, exudates
• Temperature ≥100.9 °F
• Tender anterior cervical lymph nodes
• Absence of conjunctivitis, cough, and rhinorrhea (those features suggest viral)

Question 2

What kind of infections are found in the nasopharynx?

Answer 2

Mainly viruses, i.e. rhinoviruses, coronaviruses, and other respiratory viruses,

Question 3

What kind of infections are found in the oropharynx?

Answer 3

Streptococcus pyogenes (group A streptococci), Corynebacterium diphtheriae, Epstein-Barr virus, adenovirus, enterovirus.

Question 4

What kind of infections are found in the middle ear and parasinuses?

Answer 4

Most often: Streptococcus pneumoniae, Haemophilus influenzae non-typeable, also Moraxella catarrhalis, group A streptococci

Question 5

What kind of infections are found in the epiglottis?

Answer 5

Haemophilus influenzae type b

Question 6

What are some key features of Streptococcus pyogenes (group A streptococci)?

Answer 6

• Gram Positive
• cocci occur in chains
• Catalase negative
• Beta-hemolytic (lyse blood cells entirely)
• Bacitracin sensitive

Question 7

List some clinical presentations of Group A Strep.

Answer 7

Suppurative streptococcal diseases
Impetigo
Erysipelas
Cellulitis
Necrotizing fasciitis
Rheumatic Heart Disease

Question 8

How should you diagnose for Strep A?

Answer 8

If you get a negative rapid test for Strep, get a bacterial culture to test for GAS, because many cases were found to be missed diagnoses when the rapid test was negative but the culture would have been positive. If the rapid test is positive, this is definitive and no culture.

Question 9

What are some characterisitcs of Haemophilus influenzae?

Answer 9

Gram-negative
Coccobacilli
Need chocolate agar to grow (heat blood agar plate to make it into chocolate agar (breaks blood cells, they turn brown, looks like chocolate)

Question 10

What strains of H. influenzae are primarily responsible for systemic disease in humans?

Answer 10

Capsular type b.

Question 11

Describe the H. influenzae type B capsule.

Answer 11

• polyribose-ribitol phosphate (abbreviated PRP or Hib)
• antiphagocytic
• antibody against the capsular polysaccharide is protective against invasive infections by H. influenzae

Question 12

Where are non-encapsulated forms of H. Influenzae found?

Answer 12

They are normal flora in the URT and are often isolated from patients with otitis media.

Question 13

What are some diseases caused by type B H. Influenzae?

Answer 13

• Meningitis
• Epiglottitis
• Pneumonia
• bacteremia
• cellulitis
• septic arthritis

Question 14

Describe an innate line of defense against Hib.

Answer 14

Phagocytosis is important in protection. Anti-capsular antibodies act as opsonins that mediate complement-dependent phagocytosis of the organisms. Antibodies plus complement can also lead to bacterial lysis.

Question 15

How should you treat against Hib?

Answer 15

Cephalosporin and if organism proves susceptible to ampicillin switch to tha

Question 16

Who is susceptible to infections against Corynebacterium jeikeium?

Answer 16

Immunosuppressed patients and is frequently resistant to multiple antibiotics.

Question 17

What are some characteristics of Diphtheroids (Corynebacterium diphtheriae)?

Answer 17

• Part of the normal flora of mucous membranes
• Catalase positive
• Gamma hemolytic
• Turns black on blood agar plate with tellurite salte

Question 18

How is corynebacterium diphtheriae classified?

Answer 18

Based on site of infection:
–Anterior nasal
–Tonsillar and pharyngeal
–Laryngeal
–Cutaneous
–Ocular
–Genital

Question 19

What’s the pathophysiology of corynebacterium diphtheriae?

Answer 19

1. Organisms enter the URT
2. Colonize mucosa
3. Produce dipthera toxin
   a. Necrosis
   i. Pseudomembrane
   ii. Death by obstructon
   b. Myocarditis
   c. Neuritis

Question 20

Describe the biochemical pathology of corynebacterium diptheriae.

Answer 20

-It is an AB toxin
Has A and B sites (as well as a transmembrane domain)
A = Active site
B = binding site
-This toxin places an ADP-ribose onto Elongation Factor 2 (involved in elongating new polypeptides), shutting down protein synthesis.

Question 21

What are two treatments for corynebacterium diptheriae?

Answer 21

1. Antitoxin
   –Horse origin: test for sensitivity
   possible serum sickness
   –Earlier Rx better prognosis
2. Antibiotic Rx
   –Eradicate organisms; do not prevent intoxication