Lower Respiratory Tract Infections

Lower Respiratory Tract Infections
By: Divya Ahuja, M.D.

Lower respiratory infections: anatomic classification
* Tracheitis; bronchitis; tracheobronchitis
* Bronchiolitis
* Bronchopneumonia
* Segmental pneumonia
* Lobar pneumonia
* Interstitial pneumonia

Case #1
* 40-year-old man
* no underlying lung disease
* 7-day history of mild shortness of breath with exertion, and a productive cough.
* Temperature = 37°C, pulse 84 beats/min, and his respiratory rate 17 breaths per minute.
* no rales are heard; scattered wheezes are heard in the lung bases.

Acute bronchitis (“chest cold”)
* Usually of viral etiology(influenza, rhinovirus, parainfluenza, RSV, human metapneumovirus)
* A common cause for overuse of antibiotics
* Bacteria implicated are
o Bordetella pertussis (whooping cough)
o Mycoplasma pneumoniae
o Chlamydia pneumoniae

Acute bronchitis
* Similar to URIs but more prolonged
* Cough persists > 5 days (upto 40 days)
* 40% will have reduction in pulmonary function
* Main differential includes
o Asthma/ bronchiolitis
o Bronchiectasis
o Chronic bronchitis (cough and sputum for 3 months during 2 years

Acute Bronchitis

* Cough in the absence of fever, tachycardia, and tachypnea suggests bronchitis, rather than pneumonia
* Antimicrobial agents are not recommended in most cases of acute bronchitis
* Antimicrobial therapy is indicated when a treatable pathogen is identified (influenza, Bordetella pertussis )

Acute exacerbations of chronic bronchitis

* Chronic bronchitis is associated with cigarette smoking and COPD
* Extent to which specific bacterial pathogens explain exacerbations is controversial.
* However, repeated bacterial infections (especially H. influenzae) contribute to deterioration of lung function.

Case # 2

* 54 year male, chronic cough x 1 year. no hemoptysis. Denies fevers, shakes, chills. No sick contacts

Bronchiectasis
* Abnormal dilatation of bronchi with chronic productive cough.
* Can be clue to cystic fibrosis in younger patients (associated with S. aureus and Pseudomonas species)
* Uncommon associations: immunodeficiency disorders, dyskinetic cilia syndrome

Case # 3
* 54 year old male
* Flu like illness 2 weeks ago
* 5 day history of chills, fever, difficulty breathing, right sided pleuritic chest pain, cough and yellow sputum

Pneumonia
* 6th leading cause of death in U.S.A.
* About 3 million cases per year; > 500,000 hospital admissions
* About 50% of cases and the majority of deaths are due to bacteria
* Precise diagnosis is usually desirable but difficult to obtain

Acute pneumonia

* History
* Symptoms-cough, sputum, fever, malaise
* Clinical setting-community acquired, nosocomial
* Defects in host defense- HIV, neutropenia
* Possible exposures

Organisms in community acquired pneumonia

Organisms:
S pneumoniae
H influenzae
o P aeruginosa
o S aureus
o Atypicals
+ Chlamydia, Legionella
+ Mycoplasma, Bordetella

Pneumonia (2)
* Streptococcus pneumoniae the most common cause of community-acquired pneumonia requiring hospitalization
* Haemophilus influenzae and Moraxella catarrhalis are increasing in frequency
* Legionella species and Chlamydia pneumoniae have emerged
* Pneumocystis carinii (HIV disease)

Pneumonia: pathogenesis
* Endogenous vs. exogenous (inhalation)
* Bronchogenous vs. lymphohematogenous
* “Pulmonary clearance”: mucociliary blanket, alveolar macrophages
* Factors that impair pulmonary clearance: viral URI; smoking; alcohol; uremia; bronchial obstruction; 100% oxygen; others

“Typical” versus “atypical” pneumonia

* “Typical” (virulent bacteria): abrupt onset; productive cough with purulent sputum; pleuritic chest pain; impressive physical findings; leukocytosis or leukopenia
* “Atypical” (viral, Mycoplasma pneumoniae, others): gradual onset, nonproductive cough; substernal chest pain; unimpressive physical exam; white blood count normal

Typical versus atypical pneumonia

Classic pneumococcal pneumonia

* Antecedent upper respiratory infection
* Sudden onset with single violent chill, then fever
* Pleuritic chest pain
* Signs of lobar consolidation on exam
* If untreated, terminates gradually by “lysis” or suddenly by “crisis”

Atypical pneumococcal pneumonia

* Caught early: signs of consolidation may be absent
* Elderly: fever, classic history may be absent
* COPD: CXR and physical findings are distorted
* Ethanolism: blunted history; prostration, leukopenia
* Epilepsy: lack of history; fever and tachycardia may be attributed to seizures; anaerobes may co-exist
* Recurrent pneumonia: In same area, suggests obstruction or bronchiectasis

Some current problems with pneumococcal disease

* Failure of antibiotic therapy to improve survival during first 3 days
* Vaccine efficacy and distribution
* Resistance to penicillin G
* Overwhelming sepsis in asplenic persons
* Need for developing better diagnostic techniques

Group A streptococcal pneumonia

* Rare, except during influenza epidemics
* Large empyema (“pus in the chest”) is characteristic

Hemophilus influenzae pneumonia

* 2% to 18% of community-acquired pneumonias;
* Predisposition: underlying lung disease, alcoholism, recent URI, advanced age
* Often a patchy segmental pneumonia or bronchopneumonia
* Virtually-diagnostic Gram’s stain: small, pleomorphic gram-negative coccobacilli

Moraxella catarrhalis pneumonia

* AKA: Neisseria catarrhalis; Branhamella catarrhalis
* A large gram-negative diplococcus
* Causes pneumonia and bronchitis especially in persons with chronic lung disease
* Often a patchy bronchopneumonia

Mycoplasma pneumoniae pneumonia

* The classic “primary atypical pneumonia”
* Typically occurs in younger adults, often the parents of young children
* Subtle presentation
* Favors lower lobes
* Pleural effusion may occur (up to 20%)

Some nonrespiratory manifestations of Mycoplasma pneumoniae pneumonia

* Myringitis (sometimes bullous)
* Hemolytic anemia
* Arthritis, arthralgias, myalgias
* Pericarditis, myocarditis
* Hepatitis (mild)
* Erythema multiforme, other rashes
* Meningitis, meningoencephalitis, neuropathy

Chlamydia pneumoniae pneumonia

* Accounts for <5% of community-acquired pneumonias
* C. pneumoniae more commonly causes pharyngitis and hoarseness
* Bronchitis is often insidious
* Pneumonia usually mild and localized but difficult to eradicate

Legionella pneumophila pneumonia

* Up to 23% of community-acquired pneumonias but with wide geographic distribution
* L. pneumophila is not part of the normal flora; a true inhalation disorder
* CXR: patchy or nodular infiltrates that may progress rapidly; up to 50% are bilateral

Legionella pneumophila pneumonia (2)

* Relative bradycardia in 65%
* Neurologic findings in 26%
* Gram’s stain may show purulence without a predominant microorganism
* Laboratory: may have hyponatremia; elevations of AST (SGOT), alkaline phosphatase, and bilirubin; proteinuria, hematuria, and renal failure

Treatment

* S. pneumoniae resistance is increasing
* Options are cephalosporins, amox/clvulanic acid, macrolides, doxycycline, a respiratory fluoroquinolone
* All atypicals are covered by the macrolides , doxycycline and the fuoroquinolones
* Judge the severity to see if outpatient treatment will suffice

Aspiration (“mouth flora”) pneumonia

* usually presents as a subacute illness in patients with some combination of alcoholism, malnutrition, homelessness, and poor dentition
* sputum often has foul odor
* Necrotizing pneumonia; lung abscess(es) with air-fluid levels; empyema

Pneumonia: some clues
* Tularemia: rabbits and hares; ticks and fleas; inhalation (e.g., after mowing over carcasses)
* Psittacosis: birds
* Plague: ground squirrels, chipmunks, rabbits, prairie dogs, rats
* Legionnaire’s disease: contaminated aerosols (air coolers; hospital water supplies)
* Histoplasmosis: dust from soil enriched with bird or bat droppings; Mississippi and Ohio River valleys
* Coccidiodomycosis: southern California (esp.. San Joachin Valley); southwest Texas, Arizona, N Mexico
* Pneumocystis carinii: HIV risk factors
* Relative bradycardia: viral infection; Mycoplasma pneumoniae; Psittacosis; Tularemia; Legionella
* Q fever (Coxiella burnetii): goats, cattle, sheep
* Meliodosis: travel to S.E. Asia, East Indies, Australia, Guam, South or Central America
* Brucellosis: cattle; goats; pigs; abattoir works and veterinarians
* Anthrax: cattle, swine, horses; goat hair, wool, or hides

Pneumococcal pneumonia: Predisposing factors
* Sickle cell disease
* Asplenia
* IgG disorders: agammaglobulinemia, myeloma, chronic lymphocytic leukemia
* Nephrotic syndrome
* Cirrhosis
* Alcoholism

Case # 4
* RA 57 year Caucasian male
* Cough , dyspnea, diarrhea for weeks
* No response to cephalexin
* CT sinuses - normal
* Progressive malaise and presented to ER
* pO2 on 100% NRB- 90, Creatinine 1.8, WBC: 12
* CXR-read as normal, HIV positive

Pneumonia in AIDS patients
* When in doubt, respiratory isolation for Tb
* S. pneumoniae is the number 1 cause
* Investigations
o Obtain sputum for gram stain and culture
o Other serology and antigen testing as indicated (histoplasma, cryptococcus, PCP, coccidio, etc.
o AFB stain if indicated(sensitivity with 3 specimens is about 60%)

PCP: Diagnosis (Imaging)
Chest x ray: PCP pneumonia with bilateral, diffuse granular opacities.
Credit: L, Huang, MD, HIV InSite

Chest x ray: PCP pneumonia with bilateral perihilar opacities, interstitial prominence, hyperlucent cystic lesions. Credit: HIV Web Study, www.hivwebstudy. org, © 2006 University of Washington

PCP
* PCP is a SUBACUTE pneumonia, CD4 usually <200
* Dyspnea, dry cough, chest discomfort
* In 30% patients
o CD4 > 200
o CXR normal
* TMP/SMX and steroids if hypoxic

Tuberculosis in HIV patients
* Occurs at any CD4 count
* Primary TB
o Occurs especially in people with advanced HIV infection
o Comprises about 1/3 of TB cases in HIV patients
* Reactivation of latent TB
o More likely in HIV-infected patients
o 7-10% annual risk in HIV-infected patients with positive tuberculin skin test (TST)
+ In HIV uninfected, 5-10% lifetime risk
* Patients with TB have HIV viral loads and faster progression of HIV

Case # 5
* 45 year female
* Intubated in the ICU for 7 days
* Now has worsening fever, leukocytosis and increased oxygen requirement

Nosocomial pneumonia
* Role of oropharyngeal colonization, especially of gram-negative rods (Pseudomonas, acinetobacter, etc.) : by end of one week, 45% of ICU patients are colonized; pneumonia develops in 23% of colonized patients versus 3.3% of non-colonized patients
* Risk factors to colonization: more advanced illness, longer duration in the hospital, antibiotics, intubation, azotemia, underlying pulmonary disease

Case # 6
* 23 year male, acute leukemia and bone marrow transplant
* Is severely neutropenic due to chemotherapy

Cavitary pneumonia
* Tuberculosis
Actinomyces
Nocardia
Klebsiella
Staphylococcus aureus
Anaerobic organisms
* Fungal infection Histoplasmosis
Coccidiomycosis, aspergillus

Complications of pneumonia
* Pleuropulmonary: lung abscess; adult respiratory distress syndrome (ARDS); pleural effusion; empyema; bronchopleural fistula; bronchiectasis; fibrosis; slow resolution
* Extrapulmonary: meningitis; brain abscess; endocarditis; pericarditis; arthritis; osteomyelitis

Lung Abscess
* Lung abscesses are usually caused by mouth flora(viridans strep, anaerobes, etc.)
* They need prolonged courses of antibiotics
* Options are the clindamycin, amox/clavulanic acid, pip/tazo, carbapenems

Pneumonia: Summary
* 6th leading cause of death and most common nosocomial infection causing death
* Precise diagnosis desirable but all-too-often not obtained
* Bronchoalveolar lavage and endobronchial sampling are now standard in nosocomial or difficult to diagnose pneumonia


Lower Respiratory Tract Infections.ppt