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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
FHV-1 is _____ virulent than Calicivirus, but it is ____ environmentally stable
more; less (FHV-1 only stable in environment for 24 hours, calicivirus for 8-10d)
26
Describe Cryptococcus neoformans
* 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
What are some microbes of the lower respiratory tract?
* Pasteurella * Moraxella * Klebsiella * Enterobacter * Corynebacterium \*source = generally aspiration from URT, esp. pharyngeal flora
28
What are some LRT infections?
* Tracheobronchitis (Dog) - multiple agents, **cough** * Chronic bronchial dz (cat) - coughing, wheezing, dyspnea, open mouth breathing
29
What are the clinical signs of LRTD?
LRTD - intrathoracic trachea, bronchial tree, pulm parenchyma * Coughing, gagging, panting, tachypnea, exercise, intolerance, open mouth breathing * **Expiratory dyspnea****​**
30
What are the clinical signs of pleural disease?
* **Inspiratiory dyspnea** - **generally w/o stridor** * coughing, gagging, panting, tachypnea, exercise intolerance, open mouthed breathing
31
What are some examples of LRT infections?
* Canine infectious respiratory disease complex (CIRDC) * chronic bronchitis * bacterial pneumonia
32
Name an example of a pleural infection
Pyothorax
33
Describe CIRDC
* 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
What are the primary viral pathogens of CIRDC?
* Canine adenovirus 2 * canine distemper virus * canine resp coronavirus * canine influenza * canine herpesvirus * canine pneumovirus * canine parainfluenza virus
35
What are the primary bacterial pathogens of CIRDC?
* Bordetella * S. Equi subspecies zooepidemicus * Mycoplasma
36
How do you diagnose CIRDC?
* 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
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
False
38
When would molecular assays with cultures and sensitivities be recommended for CIRDC?
* high-risk populations * poor response to treatment or severe clinical disease
39
How is CIRDC transmitted?
direct contact, indirect via fomites, aerosols
40
How do you prevent CIRDC?
* 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
Bordetella bronchiseptica has zoonotic potential to what demographic?
immunosuppressed children
42
Describe bacterial bronchitis
* 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
Describe bacterial pneumonia
* 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
What are some host factors that predispose to bacterial pneumonia?
* Age * metabolic dz * poor nutrition * neuromuscular dz * anatomic abnormalities * anesthesia/surgery (decr host defenses)
45
What are some environmental factors that can predispose to bacterial pneumonia?
* High animal density * unsanitary conditions * poor ventilation * presence of your/unvaccinated animals * presence of animals w/ URTD * stress * \*\*concurrent viral infection
46
What are some common pathogens that cause bacterial pneumonia?
* Gram +: Staph (coag +), Strep, Enterococcus * Gram -: E. Coli, Pseudomonas, Bordetella, Pasteurella, Klebsiella, Actinobacillius * Anaerobes: Bacteroides, Clostridium, Fusobacterium
47
Describe canine viral pneumonia
* **Usually cause URTD** * Pneumonitis - uncomplicated, minimal exudate in distal airways * rare unless immunocompromised, high virulence, concurrent bacterial infection, stress—EXCEPT CDV, influenza
48
What is the pathogenicity of canine viral pneumonia?
* **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
What are some other types of pneumonia in dogs and cats?
* Fungal pneumonia - systemic mycoses * Histo, Blasto, Coccidiod, Crypto, Penicillum, Pneumocystis * Rickettsial pnemonia * Erhlichia canis, Rickettsia rickettsii * Protozoal pneumonia * Acanthamoeba * Neospora * Toxoplasma
50
What are some lower respiratory pathogens of cats?
* Pasteurella * E. Coli * Staph * Strep * Pseudomonas * Bordetella * Mycoplasam
51
What infectious agents can cause serofibrinous pleural effusions?
* Infectious canine hepatitis * lepto * CDV * tuberculosis * other canine/feline viral URD
52
What infectious agents can cause granulomatous/pyogranulomatous pleural effusions?
* FIP * Fungal
53
What can result in bacterial or fungal pleural effusions?
* Penetrating thoracic wounds * extension from pneumonia * migrating FB * esophageal perf * extensions of cervical lumbar or mediastinal infections * hematogenous
54
What types of bacteria most often are found in pyothoraxes of dogs vs. cats?
* Dogs: anaerobic bacteria (Fusobacterium, **Nocardia asteroids, Actinomyces - suggestive of FB)** * Cats: Pasteurella multocide, anaerobes \*\*fungal infections (rare) = Blasto, Candida, Aspergillus, Crypto
55
How do you diagnose a pyothorax?
* 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
How do you treat pyothorax? What is the prognosis?
* 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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