Flashcards in 3.6.2. Bacteria Upper Respiratory Infections Deck (21)
How can you tell the difference between a bacterial and viral infection?
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)
What kind of infections are found in the nasopharynx?
Mainly viruses, i.e. rhinoviruses, coronaviruses, and other respiratory viruses,
What kind of infections are found in the oropharynx?
Streptococcus pyogenes (group A streptococci), Corynebacterium diphtheriae, Epstein-Barr virus, adenovirus, enterovirus.
What kind of infections are found in the middle ear and parasinuses?
Most often: Streptococcus pneumoniae, Haemophilus influenzae non-typeable, also Moraxella catarrhalis, group A streptococci
What kind of infections are found in the epiglottis?
Haemophilus influenzae type b
What are some key features of Streptococcus pyogenes (group A streptococci)?
-cocci occur in chains
-Beta-hemolytic (lyse blood cells entirely)
List some clinical presentations of Group A Strep.
Suppurative streptococcal diseases
Rheumatic Heart Disease
How should you diagnose for Strep A?
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.
What are some characterisitcs of Haemophilus influenzae?
Need chocolate agar to grow (heat blood agar plate to make it into chocolate agar (breaks blood cells, they turn brown, looks like chocolate)
What strains of H. influenzae are primarily responsible for systemic disease in humans?
Capsular type b.
Describe the H. influenzae type B capsule.
-polyribose-ribitol phosphate (abbreviated PRP or Hib)
-antibody against the capsular polysaccharide is protective against invasive infections by H. influenzae
Where are non-encapsulated forms of H. Influenzae found?
They are normal flora in the URT and are often isolated from patients with otitis media.
What are some diseases caused by type B H. Influenzae?
Describe an innate line of defense against Hib.
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.
How should you treat against Hib?
Cephalosporin and if organism proves susceptible to ampicillin switch to tha
Who is susceptible to infections against Corynebacterium jeikeium?
Immunosuppressed patients and is frequently resistant to multiple antibiotics.
What are some characteristics of Diphtheroids (Corynebacterium diphtheriae)?
-Part of the normal flora of mucous membranes
-Turns black on blood agar plate with tellurite salte
How is corynebacterium diphtheriae classified?
Based on site of infection:
–Tonsillar and pharyngeal
What's the pathophysiology of corynebacterium diphtheriae?
1. Organisms enter the URT
2. Colonize mucosa
3. Produce dipthera toxin
ii. Death by obstructon
Describe the biochemical pathology of corynebacterium diptheriae.
-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.