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Microbiology Unit II > 1 Otitis Sinusitis Dip And Whoop > Flashcards

1 Otitis Sinusitis Dip And Whoop Flashcards

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1
Q

Inflammation of the external auditory canal

A

Otitis Externa

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2
Q

Predisposing factors for otitis externa

A

Moisture (swimmer’s ear)

Insertion of foreign objects

Trauma

Chronic skin diseases

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3
Q

Characteristic SSx of otitis externa

A

Otalgia and otorrhea

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4
Q

A fever of > 38.3˚C accompanying otitis externa indicates…

A

More than localized involvement

If it’s only otitis externa, you won’t typically see a fever

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5
Q

Most common bacterial causes of otitis externa

A

Pseudomonas aeruginosa
Staphylococcus aureus

Both are predominant parts of normal skin flora

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6
Q

Characteristic of pseudomonas that protects it from ID by the immune system

A

SLIME LAYER

It’s encapsulated and glycocalyx gives the immune system the slip

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7
Q

Describe pseudomonas

A

Gram-negative bacilli

Encapsulated

Pigment producer

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8
Q

What are these pigments that pseudomonas makes?

A

Pyocyanin - non-fluorescent bluish; it’s a virulence factor (generates ROSs to kill off its competition and body tissue with it)

Pyoverdin - fluorescent green; not really a virulence factor but makes it easier to ID (sequesters iron - a siderophore)

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9
Q

What does pseudomonas smell like?

A

Very distinct fruity odor (no other organism smells like it)

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10
Q

Describe staphylococcus aureus

A

Gram-positive cocci in graphlike clusters

Encapsulated

Coagulate positive

ß-hemolytic version leads to complete lysis of RBCs
• Quick test - can cause blood clots via enzyme - other staph orgs don’t

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11
Q

How do you diagnose otitis externa?

A

Examination of the ear

Gram stain

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12
Q

Treatment of otitis externa

A

Removal of debris from the ear canal

Topical treatments: acidifying agents, topical corticosteroids, topical antimicrobial agents

Oral abx if fever is present or extension of disease has occurred

Systemic analgesics

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13
Q

Inflammation of the middle ear, including the tympanic membrane and usually associated with a buildup of fluid in the middle ear space

A

Otitis media

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14
Q

Inflammation within the paranasal sinuses; may or may not be purulent

A

Sinusitis

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15
Q

Most common bacterial causes of otitis media and sinusitis

A

Streptococcus pneumoniae (~50%)

Haemophilus influenzae (~20%)

Mortadella catarrhalis (~10%)

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16
Q

Streptococcus pneumoniae has what shape/stain?

A

Gram-positive, lancet-shaped diplococci

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17
Q

Virulent strains of strep pneumo are _______

A

Encapsulated

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18
Q

Alpha-hemolysis on blood agar is indicative of what bacterium?

A

Strep pneumo

Can lyse RBCs but not completely like ß-hemolytic bacteria

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19
Q

Bacterium that is sensitive to optochin

A

Strep pneumo

Optochin is an abx used for Dx only (too toxic for therapeutic use)

Optochin helps us differentiate strep pneumo from other strains of strep

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20
Q

What does Haemophilus influenzae look like?

A

Gram-negative coccobacilli

Some non-typeable strains

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21
Q

What does Moraxella catarrhalis look like?

A

Gram-negative diplococci

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22
Q

Moraxella catarrhalis virulence factors

A

Oxidase positive

ß-lactamase producer

23
Q

How is Otitis Media diagnosed?

A

Clinical presentation

Tympanocentesis to aspirate fluid from middle ear CAN be done but usually reserved for restricted patient populations

24
Q

DOC for AOM

A

Amoxicillin

However, several antibiotics are available - choice depends on several factors

In chronic cases, may insert tympanostomy tubes

25
Q

How is sinusitis diagnosed?

A

Clinical presentation and history most common

Can also do nasal cytology (biopsy), CT scan, allergy testing (but usually not necessary)

26
Q

Treatment of sinusitis

A

Varies depending on the type of sinusitis and the offending agent

Nasal irrigation
Analgesics
OTC decongestants
Abx
Nasal steroids
Nasal surgery
27
Q

Causative agent of Diphtheria

A

Corynebacterium

Gram-positive, pleomorphic bacilli (shape different depending on where it’s growing)

28
Q

Special features of corynebacterium

A

Palisades or “V” appearance

Metachromatic volition granules (polar ends)

Grows aerobically on blood agar but usually cultured on selective media

29
Q

Toxigenic strains of corynebacterium have…

A

A phage-encoded exotoxin (diphtheria toxin)

30
Q

What stimulates the production of diphtheria toxin?

A

Low iron concentration

31
Q

How does Diphtheria toxin function?

A

Low iron concentration stimulates production of diphtheria toxin, which is an A-B exotoxin

Exotoxin binds to a heparin-binding EGF receptor, exotoxin is endocytosed, vesicle acidified, releasing the A subunit and allowing it to move into the cytoskeleton, where it inactivates EF-2 via ADP-ribosylation —> halting protein synthesis

32
Q

Cutaneous diphtheria is characterized by…

A

Chronic, non-healing sores or ulcers

Most cases are due to nontoxigenic strains of corynebacterium

33
Q

Respiratory diphtheria is characterized by…

A

Pharyngeal colonization

Sudden onset of malaise, exudative pharyngitis, low-grade fever, and lymphadenitis

Formation of PSEUDOMEMBRANE (network of fibrin+bacteria+WBCs+necrotic epithelial cells) —> local tissue destruction

“Bull neck” in serious disease

Systemic complications

34
Q

Pathogenesis of diphtheria

A

Adherence and proliferation + 2-6 days

Localized damage due to exotoxin

Continued exotoxin production

Systemic toxicity (myocarditis and demyelination)

Local necrosis and edema (pseudomembrane and bull neck)

35
Q

Diphtheria is found worldwide but especially in…

A

Poor urban areas where vaccine-induced immunity is low

Maintained in the population by asymptomatic carriage in immune individuals

Person-to-person spread via respiratory droplets or skin contact

36
Q

Is diphtheria a reportable disease?

A

Yes (respiratory is anyway)

Vaccines have made it uncommon in developed countries these days

37
Q

How is diphtheria diagnosed?

A

Clinical examination is most important for early diagnosis to allow initiation of appropriate treatment

PSEUDOMEMBRANE

BULL NECK

38
Q

What culture media are used to diagnose diphtheria?

A

Loeffler’s medium (supports growth and enhances formation of volutin granules)

Cysteine-tellurite agar (distinctive black to tellurite reduction, isolates tested for toxin production)

39
Q

How does diphtheria stain?

A

Gram-positive bacilli with metachromatic volutin granules

40
Q

What is the Elek test?

A

Immunodiffusion assay to secretion of diphtheria exotoxin

41
Q

What other methods are used to diagnose diphtheria

A

Various methods for isolating toxin production

Elek test

PCR (expensive) - detects tox gene

ELISA (also $$) - detects diphtheria exotoxin

Immunochromatographic strip assay - detects diphtheria exotoxin

42
Q

Treatment of diphtheria is focused on …

A

Neutralizing exotoxin

Administration of diphtheria antitoxin requires rapid diagnosis and treatment

43
Q

What antibiotic is used against diphtheria?

A

DOC = erythromycin (alternative = penicillin)

Isolation to minimize secondary spread

44
Q

Causative agent of pertussis

A

Bordatella pertussis

Small, gram-negative coccobacilli

Grows aerobically on enriched agar

45
Q

Virulence factors for bordatella pertussis

A

Several in addition to endotoxins

Adhesins mediate attachment of integrity’s and subsequent colonization of the ciliated respiratory epithelium

4 exotoxins:
Pertussis toxin (A-B exotoxin)
Dermonecrotic toxin (vasoconstriction —> ischemic necrosis)
Adenylate cyclase toxin (decreases chemostasis)
Tracheal cytotoxic (kills ciliated respiratory epithelial cells, stimulates IL-1 release)

46
Q

Pathogenesis of pertussis

A

Inhalation of aerosol droplets

Bacterial attachment to ciliated airway epithelium and production of toxins

Bacterial multiplication, influx of neutrophils, damage to ciliated epithelium by TCT and LPS, music hypersecretion

Compromises the small airways and predisposes patients to atelectasis, cough, cyanosis, and PNA

47
Q

Average incubation period for pertussis

A

7-10 days

48
Q

Most highly contagious stage of pertussis

A

Catarrhal stage (1-2 weeks after incubation)

Inflammation of the mucous membranes, presents as nonspecific upper respiratory tract syndrome with insidious onset

49
Q

Second stage of pertussis

A

Paroxysmal stage (2-4 weeks)

Attacks or spasms of paroxysmal coughing often with posttussive emesis

This is when you’ll hear the characteristic “whoop” due to labored inspiration

50
Q

Third stage of pertussis

A

Convalescent stage - paroxysms decrease in number and severity with gradual recovery over several weeks

Serious complications can develop (PNA, encephalopathy, seizures, death)

51
Q

Presumptive diagnosis of pertussis is via

A

Serology

ELISA to detect Ig to pertussis toxins or adhesins

4-fold increase in paired sera or a high initial titer is indicative of a recent infection

52
Q

Definitive diagnosis of pertussis is via…

A

Culture on an enriched medium:
• Bordet-Gengou agar
• Regan-Lowe agar

Can also use PCR (highly sensitive)

53
Q

Treatment of pertussis

A

DOC = erythromycin or other macrolide

Alternative: TMP-SMX

Can also give prophylaxis for nonimmunized contacts

Prevention via immunization (DTaP or Tdap booster)

Microbiology Unit II (7 decks)

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