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Clinical Microbio > Respiratory Pathogens > Flashcards

Respiratory Pathogens Flashcards

1
Q

What about the alveolar epithelium makes it particularly susceptible to infection?

A
  • Continuously exposed to inhaled contaminants
  • blood flow thru lung —> incr risk for bacteremia
  • Thus, need for multilayered system of defense against infectious agents
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2
Q

Describe nasal-associated lymphoid tissue (NALT)

A
  • lymphoid follicles and loose aggregates of mononuclear cells in lamina propria
  • local immune response
  • microfold (M) cells and specialized follicle-associated epithelial cells transfer antigen to underlying lymphoid follicles
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3
Q

What are some defense mechanisms of the upper respiratory tract?

A
  • resident microbes
  • vibrissae (hair)
  • nasal chonchae (incr turbulence)
  • Mucous lining (antimicrobial properties)
    • lysozyme, b-defensins, NO, Ig, IFN
  • pharyngeal lymphoid tissue
  • sneeze reflex
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4
Q

What are some defense mechanisms of the tracheobronchial region?

A
  • mucociliary apparatus
  • cough reflex
  • BALT - cellular and humoral responses
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5
Q

What are some defense mechanisms of the pulmonary region?

A
  • mucus
  • pulmonary alveolar macrophages (PAMs)
  • other lymphocytes in blood
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6
Q

What are some defense mechanisms of the lung?

A
  • Alveolar macrophages
    • ​recognize foreign invaders (esp. w/ opsonins)
    • engulf and kill microbes without inducing inflammation
  • Pulmonary immune response
    • ​Ag presentation by airway epithelial dendritic cells that migrate to bronchial lymph nodes (BALT)
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7
Q

Why is it so important that alveolar macrophages kill off microbes without inducing inflammation?

A
  • inflamm exudates impair gas exchange
  • leukocyte-derived enzymes and oxygen radicals cause injury to lung tissue
  • repair processes —> alveolar exudates or fibrosis of alveolar septa —> permanently decreased lung compliance and thickens blood-gas barrier
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8
Q

What are some microbial flora of the URT (nasal cavity and pharynx) in dogs and cats?

A
  • Coag-neg and coag-pos Staph
  • alpha- and non-hemolytic Strep
  • Corynebacterium
  • E.coli
  • Pasteurella
  • Pseudomonas
  • Klebsiella
  • Bordetella
  • Mycoplasma
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9
Q

What are some microbial flora of the URT (nasal cavity and pharynx) More common in dogs?

A
  • Bacillus
  • Neisseria
  • Enterobacter
  • Moraxella
  • Proteus
  • Alcaligenes
  • Clostridium
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10
Q

What are some microbial flora of the URT (nasal cavity and pharynx) more common in cats?

A
  • Micrococcus
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11
Q

Who are most at risk for respiratory tract infections, and why?

A
  • Young - immune system not completely developed
  • Geriatric - Chronic degen changes disrupt normal mucociliary clearance, increased vulnerability to airborne/toxic particulates
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12
Q

What are some examples of URT infections?

A
  • Bacterial rhinitis
  • chronic sinusitis
  • tonislitis
  • pharyngitis
  • laryngitis
  • URI
  • feline upper resp tract infection = URTD
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13
Q

What are the clinical signs of URT disease?

A
  • Sneezing
  • stertor (snorting/snoring)
  • stridor
  • nasal d/c
  • voice change
  • facial deformity
  • nosebleed (epistaxis)
  • coughing, gagging, choking, open-mouthed breathing
  • inspiratory dyspnea
  • halitosis
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14
Q

Bacterial rhinitis is almost always secondary to what?

A
  • Nasal trauma
  • foreign material
  • reflux
  • oronasal fistula
  • neoplasia
  • Dental dz
  • viral, fungal, parasitic infection
  • bacterial bronchopneumonia
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15
Q

Describe feline chronic rhinitis/sinusitis

A
  • Suspected to be d/t viral RT infection (FHV-1) + impaired/deranged immune response causing mucosal and turbinate damage
  • get secondary bacterial infections
  • Prognosis: guarded, can alleviate signs but likely not cure
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16
Q

How do you treat feline chronic rhinitis/sinusitis?

A
  • Treatment aimed to reduce frequency and severity of episodes
    • ​mucolytics or decongestants
    • antiviral (IFN, famciclovir, lysine)
    • broad spectrum abx for 2-4 mo
    • Repeated short courses of antibacterial may select for Pseudomonas sp.
  • Severe cases may require perforation or excision of turbinate
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17
Q

What are some potentially pathogenic bacteria of feline chronic rhinitis/sinusitis?

A
  • Pseudomonas aeruginosa
  • E. Coli
  • Strep viridans
  • Staph pseudintermedius
  • Pasteurella
  • Corynebacterium
  • Actinomyces
  • Bordetella
  • Mycoplasma
  • All anaerobes
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18
Q

Marked lethargy, sneezing, ocular and nasal discharge are all clinical signs associated with which feline URTD?

A

FHV-1

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19
Q

Marked oral ulceration is associated with which feline URTD?

A

Feline calicivirus

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20
Q

Moderate sneezing, coughing, and nasal discharge are associated with which feline URTD?

A

Bordetella

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21
Q

Marked (often persistent) conjunctivitis and ocular discharge are associated with which feline URTD?

A

Chlamydophila felis

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22
Q

What are the primary feline URTD?

A
  • Feline calicivirus
  • FHV-1
  • Chlamydophila felis
  • Mycoplasma
  • Reovirus
  • Fungal rhinitis (Cryptococcus)
  • FeLV/FIV associated
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23
Q

True or False: Feline calicivirus can replicate in only the nasal cavity

A

False; it can replicate in the conjunctiva, lung, and joints, as well as the nasal and oral cavity

24
Q

Where does FHV-1 replicate?

A
  • nasal mucosa
  • trachea
  • conjunctiva
25
Q

FHV-1 is _____ virulent than Calicivirus, but it is ____ environmentally stable

A

more; less (FHV-1 only stable in environment for 24 hours, calicivirus for 8-10d)

26
Q

Describe Cryptococcus neoformans

A
  • Most common fungal infection of cats
  • ubiquitous saprophyte (pigeon droppings)
  • FeLV/FIV predispose
  • Disseminates to eyes, CNS, skin of dorsal head
  • treatment: long term antifungals (2-6mo), fluconazole/ketoconazole/itraconazole, +/- abx for secondary bacterial infections
27
Q

What are some microbes of the lower respiratory tract?

A
  • Pasteurella
  • Moraxella
  • Klebsiella
  • Enterobacter
  • Corynebacterium

*source = generally aspiration from URT, esp. pharyngeal flora

28
Q

What are some LRT infections?

A
  • Tracheobronchitis (Dog) - multiple agents, cough
  • Chronic bronchial dz (cat) - coughing, wheezing, dyspnea, open mouth breathing
29
Q

What are the clinical signs of LRTD?

A

LRTD - intrathoracic trachea, bronchial tree, pulm parenchyma

  • Coughing, gagging, panting, tachypnea, exercise, intolerance, open mouth breathing
  • Expiratory dyspnea​
30
Q

What are the clinical signs of pleural disease?

A
  • Inspiratiory dyspnea - generally w/o stridor
  • coughing, gagging, panting, tachypnea, exercise intolerance, open mouthed breathing
31
Q

What are some examples of LRT infections?

A
  • Canine infectious respiratory disease complex (CIRDC)
  • chronic bronchitis
  • bacterial pneumonia
32
Q

Name an example of a pleural infection

A

Pyothorax

33
Q

Describe CIRDC

A
  • acute onset of cough with or without sneezing
  • nasal and ocular d/c may be present
  • fever is uncommon, may be present
  • common in large populations
34
Q

What are the primary viral pathogens of CIRDC?

A
  • Canine adenovirus 2
  • canine distemper virus
  • canine resp coronavirus
  • canine influenza
  • canine herpesvirus
  • canine pneumovirus
  • canine parainfluenza virus
35
Q

What are the primary bacterial pathogens of CIRDC?

A
  • Bordetella
  • S. Equi subspecies zooepidemicus
  • Mycoplasma
36
Q

How do you diagnose CIRDC?

A
  • Uncomplicated - PE, exposure to other dogs, response to empiric antibacterial/antitussive therapy
  • Complicated -
    • TTW w/ culture/sensitivity
    • CBC/chem
    • radiographs (interstitial pneumonia, segmental atelectasis)
    • acute/convalescent serology for viral agents
  • Single agent infections - probably rare, would be mild, self-limiting
37
Q

True or false: if patient exhibits typical clinical presentation, no evidence of pneumonia, and if high-risk populations (e.g. breeding kennels) are not involved, antibiotic treatment is recommended

A

False

38
Q

When would molecular assays with cultures and sensitivities be recommended for CIRDC?

A
  • high-risk populations
  • poor response to treatment or severe clinical disease
39
Q

How is CIRDC transmitted?

A

direct contact, indirect via fomites, aerosols

40
Q

How do you prevent CIRDC?

A
  • Parenteral and intranasal vaccines
    • generally decr dz severity, vaccinate at least 5d prior to exposure, IN evokes local mucosal immunity
  • Duration of immunity
    • viruses - 3 year
    • bordetella - 3-10 mon
41
Q

Bordetella bronchiseptica has zoonotic potential to what demographic?

A

immunosuppressed children

42
Q

Describe bacterial bronchitis

A
  • C/S: cough +/- resp distress
  • Dx: resp auscultation, thoracic rads, fluoroscopy
  • R/O other causes of bronchial inflammation (D. Immitis, parasites)
    • BAL for Mycoplasma
    • PCR (less helpful than culture)
    • Bronchoscopy = best sample
    • TTW or brush
43
Q

Describe bacterial pneumonia

A
  • More common in dogs than cats
    • young dogs - viral infection followed by secondary bacterial
    • older dogs - aspiration pneumonia/FB
  • C/S can be acute or chronic
  • Definitive diagnosis: culture/detection microbe & relevant clinical hx/signs
  • Tx: ID underlying cause, abx, control airway secretions
44
Q

What are some host factors that predispose to bacterial pneumonia?

A
  • Age
  • metabolic dz
  • poor nutrition
  • neuromuscular dz
  • anatomic abnormalities
  • anesthesia/surgery (decr host defenses)
45
Q

What are some environmental factors that can predispose to bacterial pneumonia?

A
  • High animal density
  • unsanitary conditions
  • poor ventilation
  • presence of your/unvaccinated animals
  • presence of animals w/ URTD
  • stress
  • **concurrent viral infection
46
Q

What are some common pathogens that cause bacterial pneumonia?

A
  • Gram +: Staph (coag +), Strep, Enterococcus
  • Gram -: E. Coli, Pseudomonas, Bordetella, Pasteurella, Klebsiella, Actinobacillius
  • Anaerobes: Bacteroides, Clostridium, Fusobacterium
47
Q

Describe canine viral pneumonia

A
  • Usually cause URTD
  • Pneumonitis - uncomplicated, minimal exudate in distal airways
  • rare unless immunocompromised, high virulence, concurrent bacterial infection, stress—EXCEPT CDV, influenza
48
Q

What is the pathogenicity of canine viral pneumonia?

A
  • bacterial-viral synergism: virus decr pulm antibacterial defenses
    • ​loss of ciliated epithelial cells, cellular desquamation, decr surfactant production/macrophage chemotaxis
  • can lead to chronic interstitial pneumonia —> pulm fibrosis —> asthma/COPD
49
Q

What are some other types of pneumonia in dogs and cats?

A
  • Fungal pneumonia - systemic mycoses
    • Histo, Blasto, Coccidiod, Crypto, Penicillum, Pneumocystis
  • Rickettsial pnemonia
    • Erhlichia canis, Rickettsia rickettsii
  • Protozoal pneumonia
    • Acanthamoeba
    • Neospora
    • Toxoplasma
50
Q

What are some lower respiratory pathogens of cats?

A
  • Pasteurella
  • E. Coli
  • Staph
  • Strep
  • Pseudomonas
  • Bordetella
  • Mycoplasam
51
Q

What infectious agents can cause serofibrinous pleural effusions?

A
  • Infectious canine hepatitis
  • lepto
  • CDV
  • tuberculosis
  • other canine/feline viral URD
52
Q

What infectious agents can cause granulomatous/pyogranulomatous pleural effusions?

A
  • FIP
  • Fungal
53
Q

What can result in bacterial or fungal pleural effusions?

A
  • Penetrating thoracic wounds
  • extension from pneumonia
  • migrating FB
  • esophageal perf
  • extensions of cervical lumbar or mediastinal infections
  • hematogenous
54
Q

What types of bacteria most often are found in pyothoraxes of dogs vs. cats?

A
  • Dogs: anaerobic bacteria (Fusobacterium, Nocardia asteroids, Actinomyces - suggestive of FB)
  • Cats: Pasteurella multocide, anaerobes

**fungal infections (rare) = Blasto, Candida, Aspergillus, Crypto

55
Q

How do you diagnose a pyothorax?

A
  • Thoracic rads
  • Pleural fluid for:
    • cytology, aerobic/anaerobic culture/sens
  • Gram stain/acid-fast stain
  • Actinomycetes and Mycoplasma - require specialized growth conditions/prolonged incubation
56
Q

How do you treat pyothorax? What is the prognosis?

A
  • thoracostomy tube (drainage and lavage)
  • supportive care (FB removal)

Px: guarded over short term; long term outcome good if survive initial period; FIP, lepto, ICH, TB, CDV - all poor

Clinical Microbio (11 decks)

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