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lower respiratory tract Flashcards

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1
Q

Lower Respiratory Tract (LRT) consists of

A 
 The LRT Consists of the following
> Trachea
> Bronchi
> Bronchioles
> Lung Alveoli
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2
Q

LRT bacteria

A

 Typically, the lower respiratory tract is sterile
 Areas below the larynx do not contain “normal flora”
 Exceptions:
> Patients with
- Chronic Pulmonary Disease
- Endotracheal Tubes
- Tracheostomies

 LRT infections usually occur when infecting organisms reach the
lower airways or pulmonary parenchyma via bypassing the
mechanical and other nonspecific barriers of the URT
 Infections may result from
- inhalation of infectious aerosols
- aspiration of oral or gastric contents
- hematogenous spread

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3
Q

LRT Progression of viral

A

 In order for a LRT infection to establish itself, a series of host
defenses must be overcome
> Different sequence of events for respiratory viruses as
opposed to bacterial pathogens
 Progression of viral pathogens
> Involves spread among adjacent cells and distant inoculation
of susceptible cells by aspiration of infectious secretions
> To a lesser extent, hematogenous transmission of the virus
 Lung infections by bacterial pathogens occur via direct
inoculation of organisms through aspiration from the URT

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4
Q

Bronchitis

A

> Infection and inflammation of the bronchi without
involvement of the lung parenchyma (pneumonia)
Peak season is the winter months
- Coincides with the period of peak incidence of infections

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5
Q

Bronchiolitis

A

> Infection and inflammation of the smaller bronchioles

> Most common LRT infection in children younger than 2 years

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6
Q

BRONCHITIS AND BRONCHIOLITIS causes

A

> During seasons when influenza is epidemic in the community, it is
the most common cause of acute bronchitis in the general population
During non-epidemic periods, viral pathogens include
- Rhinovirus
- Coronavirus
- Human Metapneumovirus (hMPV)
- Parainfluenza Virus

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7
Q

BRONCHITIS AND BRONCHIOLITIS Non-viral respiratory tract pathogens

A
  • Mycoplasma pneumoniae
  • Chlamydophila pneumoniae
  • Bordetella pertussis
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8
Q

Predominate cause of bronchiolitis

A

RSV - Respiratory Syncytial Virus

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9
Q

BRONCHITIS AND BRONCHIOLITIS Pathogensis

A

> Evidence almost always exists of an antecedent or coexistent
URT infection in patients with acute bronchitis
- Begins with fever and cough
- Destruction of respiratory epithelium varies with pathogen present
- Infection and damage to the airway
- Inflammatory response, necrotic debris, and edema cause
symptoms

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10
Q

BRONCHITIS AND BRONCHIOLITIS

 Clinical Manifestations

A

> Chronic Bronchitis - requires 3 months of symptoms for at least 2 years
- Linked to long-term cigarette smoking leading to worsening of symptoms
Acute Bronchitis - from an infectious process
Acute Bronchiolitis
- Infectious disease of infants
- Usually from RSV
-Wheezing, respiratory distress and air trapping

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11
Q

BRONCHITIS AND BRONCHIOLITIS

 Complications

A

> Secondary Bacterial Infections

  • Bacterial bronchitis or pneumonia
  • Example pathogens - S. pneumonia, H. influenzae, M. catarrhalis
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12
Q

BRONCHITIS AND BRONCHIOLITIS Diagnosis

A

> Based on history and physical examination
Secondary infections usually easy to obtain from purulent sputum
RSV PCR testing may be done for infection control purposes during outbreaks

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13
Q

BRONCHITIS AND BRONCHIOLITIS treatment

A

> Mainly control symptoms

> Antibiotics in select cases

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14
Q

INFLUENZA

 Epidemiology

A

> Late fall and early winter and persist into the spring; pandemics can occur
outside of typical season

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15
Q

Influenza causes

A

> Influenza A and B
Influenza A - Categorized into subtypes on the basis of two surface antigens
- Hemagglutinin (H)
- Neuraminidase (N)
Influenza B - Categorized into lineages

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16
Q

influenza pathogenesis

A 
> Antigenic shift 
- Production of new virus
- May prevent detection with kits in use
> Pandemics in 1957 and 1968
- Caused by genetic re-assortment between influenza viruses from humans 
and birds
> Pandemic in 2009 - H1N1 
- Caused of re-assortment of genetic elements of human, swine and avian 
strains
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17
Q

Influenza clinical manifestation

A

> Fever, muscle pain and fatigue

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18
Q

influenza complications

A

> Populations at increased risk for severe disease
-Young children, pregnant women, patients with underlying health
conditions
Secondary bacterial pneumonias
- S. pneumoniae, S. aureus (including community-associated strains of
MRSA) and H. influenzae

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19
Q

influenza diagnosis

A

> In the setting of an influenza outbreak, acute febrile
respiratory illnesses can be diagnosed with relative certainty by
clinical criteria alone
Detection of virus, viral antigen, or viral nucleic acid
- Pharyngeal swabs, nasal washes, sputum or
bronchoalveolar lavage/washings

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20
Q

influenza treatment & prevention

A

> Antiviral drugs
- Neuraminidase inhibitors and M2 inhibitors
- Choice of treatment depends on the susceptibility of
currently circulating influenza strains along with patient
characteristics

prevention: Annual vaccination in the fall of each year (Flu Vaccine)

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21
Q

emerging viral RT infections

A

 Highly pathogenic avian influenza (HPAI)
> H5N1 avian influenza
> H7N9 avian in origin

 Pandemic H1N1 influenza A and other swine influenza variants
> H1N1 influenza A pandemic
> H3N2 influenza A

 Severe Acute Respiratory Syndrome (SARS) caused by a coronavirus
(SARS-CoV)

 Middle East Respiratory Syndrome (MERS) caused by a coronavirus
(MERS-CoV)

 The Novel Coronavirus known as SARS-CoV-2 that caused coronavirus
disease (COVID-19) – The Current Pandemic!

 Adenovirus Infections

  • Re-emergence in military and civilian populations
  • Serotypes 4 and 7, group B serotype 14
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22
Q

acute pneumonia

A

 Distinction between acute bronchitis and acute pneumonia
may be subtle
> Depends on the extent of involvement of the LRT with the
infectious process
> Patients who have bronchitis do not exhibit the physical,
radiographic, and pathologic findings of pulmonary
parenchymal involvement outside of the airways - this type of
involvement with the infectious process defines pneumonia

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23
Q

community aquired pneumonia ( CAP) definition

A

> The onset of symptoms is in the community or within the first two days
after admission to the hospital

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24
Q

CAP epidemiology

A

> CAP is one of the most common infections encountered in clinical practice
Leading cause of death from infection in persons over the age of 65
Vaccination against S. pneumonia (Most common bacterial pathogen in
children and adults)
- Resulted in decreases in invasive pneumococcal disease
- Despite advances in diagnostics and therapeutics in recent years,
mortality rates have remained unacceptably high

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25
CAP causes
> Linked to viral infections during winter > Summer months - atypical pneumonia > Most cases are older adults or patients with underlying disease  Example Causes > RSV: children - especially in infants > Influenzae - most common virus isolated in adults > S. pneumoniae, Hib, M. pneumonia - adults > M. pneumoniae and Legionella pneumophila - atypical pneumonia
26
CAP pathogenesis
> In most cases, defense mechanisms of the lung, including the ciliated epithelial cells and innate immune system phagocytic cells can clear aspirated bacteria before infection is established > LRT infections can occur when the - bacteria involved are particularly virulent - high inoculation of microorganisms - immune system is compromised
27
CAP clinical manifestations
> Varies with the age and immunologic status of the host > Most infected patients experience - Fever associated with chills - Cough with blood-tinged, purulent sputum - Left shift WBC count (increased WBC and immature neutrophils) - Localized area of the lung involvement (lobar consolidation) that may be associated with hypoxia or reduced oxygenation
28
CAP complications
> Varies with the age and immunologic status of the host > Most infected patients experience - Fever associated with chills - Cough with blood-tinged, purulent sputum - Left shift WBC count (increased WBC and immature neutrophils) - Localized area of the lung involvement (lobar consolidation) that may be associated with hypoxia or reduced oxygenation > Respiratory Failure - Including the need for mechanical ventilation > Acute Respiratory Distress Syndrome (ARDS) > Septic shock with multisystem organ failure > Encephalitis may occur - In a minority of atypical pneumonia cases - Inflammation of the brain
29
CAP lab diagnosis ( outpatients & hospitalized patients)
> Outpatients with mild disease – diagnostic tests not general > Hospitalized patients - Blood cultures and sputum specimens collected - Molecular tests such as PCR - Antigen tests - Direct examination of sputum > 10 or fewer squamous epithelial cells/LPF
30
CAP lab diagnosis ( tracheal needle aspiration )
- Rarely used due to invasiveness, risk of complications and patient unacceptability
31
CAP lab diagnosis ( bronchoscopic methods)
- For patients who require mechanical ventilation - Also used in cases of refractory or recurrent pneumonia when empiric therapy is in doubt Note: Legionella cases challenging to diagnose from sputum or bronchial aspirates (Requires special media, Organisms do not stain well with Gram stain)
32
CAP lab diagnosis ( molecular diagnostic tools )
> Molecular diagnostic tools - PCR assays - Have been used to identify pathogens in cases otherwise negative for culture - Have been used to provide rapid test results to allow better targeting of therapy - Sensitivities have significantly improved - Specificity problems do exist and as such results must be interpreted in context (True pathogen or asymptomatic colonization?)
33
CAP lab diagnosis ( pneumococal pneumonia )
- S. pneumoniae - α-Hemolytic colonies on blood agar - Biochemical tests - Bile solubility and optochin sensitivity (Used to distinguish S. pneumoniae from other streptococci) - Cultures from blood and pleural fluid may also contain the S. Pneumonia and can be used for diagnosis
34
CAP treatment
> Treatment varies with each patient and a number of factors must be taken into consideration > The potential of drug-resistant pneumococcal infection must be considered > In cases of comorbidities or recent antimicrobial use, among other risk factors: - Respiratory fluoroquinolone alone or, - β-lactam antibiotic plus a macrolide is recommended
35
HOSPITAL ACQUIRED (HAP) AND VENTILATOR ASSOCIATED PNEUMONIA (VAP)
 HAP - Pneumonia acquired 48 hours or more after hospital admission and not associated with mechanical ventilation  VAP - Pneumonia episode diagnosed at least 48 hours after airway intubation and initiation of mechanical ventilation  Nosocomial - Originating in a hospital/hospital environment HAP
36
HAP AND VAP |  Epidemiology
> VAP occurs in ~20% of patients requiring mechanical | ventilation more than 48 hours
37
HAP & VAP causes
> Greater risk of multidrug-resistant pathogens (MDRs) > Ex. Pseudomonas aeruginosa Klebsiella pneumoniae, Acinetobacter baumannii MRSA Klebsiella spp. Enterobacter spp. E. coli
38
HAP & VAP pathogenesis
> Acquired from patient’s own respiratory flora, GI tract or hospital flora - Aspiration of bacteria > Intubation of the lower airway - Bypasses the normal mechanical defenses provided by the glottis and cough reflex > Nasogastric intubation - Interferes with glottic function - Increased reflux of gastric secretions into the oropharynx
39
HAP & VAP clinical manifestations
``` > A new or persistent infiltrate on chest imaging that is accompanied by at least two of the following - Fever - Elevated or depressed WBC count - Production of purulent sputum ```
40
HAP & VAP complications
> Rapidly progressing pneumonia requires ventilators due to overwhelming infection or lung injury > Bacteremia - If gram-negative, can lead to shock
41
HAP & VAP laboratory diagnosis
> Same principles for microbiological diagnosis apply as discussed for CAP > Noninvasive semi-quantitative sampling for diagnosis of the potential pathogen (ie. Expectorated sputum, endotracheal aspiration) > Must be a quality specimen that is not contaminated from the oropharynx > Culture - SBA, MAC, and CHOC agar - If no contamination, can perform anaerobic cultures > Blood Cultures can be used in severe cases and/or sepsis > Legionella culture included if Legionella spp. is a possible cause
42
HAP & VAP treatment
> Antibiotic treatment with modification based on culture data and clinical response > Consider institution’s antibiogram and patient’s previous resistance patterns > VAP bundles/measures - Elevating the head of the bed to prevent aspiration - Weaning sedation daily to decrease time on the ventilator and prevent complete suppression of the protective cough reflex - Oral care with chlorhexidine to decrease oral colonization
43
Empyema
Collection of purulent fluid in the pleural cavity
44
Empyema epidemiology
> Most empyemas occur in association with concurrent community-acquired acute pneumonia > Risk factors - Advanced or very young age, male gender, debilitation, comorbid disease(s), and longer duration of symptoms prior to receiving appropriate therapy - Increased incidence in children noted after seasonal and pandemic influenza epidemics
45
Empyema causes
> Most common pathogen isolated from empyemas in children - S. pneumonia > Other common causes in patients with CAP - S. pyogenes - Other streptococcal species - S. aureus > Main cause in hospitalized patients empyemas - aerobic gram-negative bacilli
46
Empyema pathogenesis
> May complicate chest surgery or chest trauma > May limit the motion and function of the lung > Resistant to antimicrobials - due to low blood flow and low pH in the area
47
Empyema clinical manifestations
> Collection of fluid in lung and chest wall > Fever, chills, night sweats > Sepsis may develop
48
Empyema complications
> Persistent empyema is difficult to eliminate. > Unresolved sepsis > Thick encapsulation of the lung, resulting in loss of function
49
Empyema lab diagnosis
> Aspirates of pleural fluid > Evacuate the air in syringe to help isolate anaerobes > Save aliquot for special studies if needed
50
Empyema treatment
> Drainage of infected fluid | > Treatment with antimicrobials
51
TUBERCULOSIS AND OTHER CHRONIC | PNEUMONIAS
 Bacterial pneumonias usually resolve completely over a period of weeks  On occasion, resolution is delayed > Radiographic lung abnormalities that persist beyond the improvement of symptoms  Necrotizing processes in the lung may occur  Some pneumonias are inherently slow in progression and chronic in nature > Mycobacterial and fungal infections of the lung
52
TUBERCULOSIS AND OTHER CHRONIC | PNEUMONIAS causes
> Mycobacteria - In immunocompetent patients > Nontuberculous mycobacteria (NTM) - Immunocompromised and socially disadvantaged - M. avium complex, M. kansasii, and M. chelonae/abscessus > Opportunistic fungal pathogens - Aspergillus, Cryptococcus, Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioides immitis
53
TUBERCULOSIS AND OTHER CHRONIC PNEUMONIAS  Pathogenesis
> Granulomatous response in the lung > Cell-Mediated Immunity (CMI) is involved in both protective and destructive aspects of these illnesses
54
TUBERCULOSIS AND OTHER CHRONIC PNEUMONIAS clinical manifestations
Symptoms vary by responsible microorganism present > Less acute symptoms appear gradually > Localized or disseminated infection > Immunocompromised patients may have severe infections
55
TUBERCULOSIS AND OTHER CHRONIC PNEUMONIAS complications
> Respiratory insufficiency > Lung fibrosis > Dissemination to other vital organs
56
TUBERCULOSIS AND OTHER CHRONIC PNEUMONIAS lab diagnosis
> Mycobacteria require specific culture media and have ong growth times > Proper respiratory isolation - Highly infectious > Specimen collection - Sputum - Bronchoscopic specimens - Lung biopsies
57
TUBERCULOSIS AND OTHER CHRONIC PNEUMONIAS diagnosis ( direct examination & others)
``` > Direct Examination - Acid-fast or other special stains (i.e., Ziehl-Neelsen) - Fungal agent preps > Other Tests - Nucleic acid testing - Serologic tests - Skin tests - Purified protein derivative (PPD) for tuberculosis - Interferon-gamma release assays (IGRA) ```
58
TUBERCULOSIS AND OTHER CHRONIC PNEUMONIAS treatment
> Pansusceptible Tuberculosis - Isoniazid (INH), rifampin, pyrazinamide, and ethambutol for an initial 2 months, followed by isoniazid and rifampin for an additional 4 months > Multidrug-Resistant Tuberculosis - Treatment based on antibiotic susceptibility testing results and consultation with an expert in tuberculosis therapy > Fungal Infections - IV amphotericin B preparation and then followed with an oral agent for prolonged treatment (12 to 24 months)
59
ASPIRATION PNEUMONIA
 Aspiration - occurs when gastric or oropharyngeal contents are inhaled into the larynx or LRT
60
ASPIRATION PNEUMONIA | epidemiology
> Associated with frequency of aspiration, material aspirated and host defenses > Increased risk associated with periodontal disease > Occurs in children and adults and more common in hospitalized patients
61
ASPIRATION PNEUMONIA | causes
> Community Acquired - S. pneumoniae, H. influenzae, Staphylococci and Enterobacteriaceae > Nosocomial Acquired - Predominantly gram-negative pathogens including P. aeruginosa > Possible anaerobic causes - Bacteroides spp., Prevotella, Peptostreptococci, Fusobacterium spp.
62
ASPIRATION PNEUMONIA | pathogenesis
> Factors of disease - Frequency of aspiration - Quality and quantity of material aspirated - Host defenses - Underlying disease > Immunocompromised patients - Increased risk of infection after aspiration of a bacterial inoculum > Chemical aspiration - Occurs when inhaled gastric acid causes injury - Severe inflammatory response, edema, decreased lung capacity, hypoxia
63
ASPIRATION PNEUMONIA | clinical manifestations
> Aspiration event with increased coughing, wheezing, hypoxia > Abscesses have a longer history of illness (weeks) than acute pneumonia > Putrid sputum and halitosis (bad breath) - Due to anaerobes
64
ASPIRATION PNEUMONIA | complications
> If treatment fails - Progression to a necrotizing pneumonia and lung abscess possible > Patients with lung abscesses usually have a longer history of illness, more subtle onset of symptoms, have a putrid sputum and complain of bad breath
65
ASPIRATION PNEUMONIA diagnosis
> Specimen collection methods are similar to those for CAP and nosocomial infections > Difficulty lies in determining whether or not therapy is warranted
66
ASPIRATION PNEUMONIA | treatment
> Broad-spectrum antibiotics that provide coverage for aerobic, gram-negative organisms > Anaerobic bacteria should be empirically treated if implicated`

Microbiology 2 (22 decks)

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