Community Acquired Pneumonia

Pneumonia in Different Patient Groups

Patient group	Bug	Mortality/ therapy
Age < 60 without coexisting illness	Strep pneumonia, Mycoplasma pneumoniae, respiratory viruses, Chlamydia pneumoniae, H. influenzae	Low (1-5%), outpatient management
Age > 60 with coexisting illness	S. pneumoniae, respiratory viruses, H. influenzae, Staph aureus	Low, 20% require hospitilization
Hospitalized patients with CAP	S. pneumoniae, H. flu, anaerobes, aerobic gram – bacilli, Legionella, S. aureus, respiratory viruses	5-25%, most deaths occur within first 7 days
Severe CAP (respiratory failure)	S. pneumoniae, Legionella, aerobic gram – bacilli, respiratory viruses	50%

Presentation

Presentation	Bug
Atypical pneumoniae	Legionella, Chylamydia, mycoplasma (20-25%), Staph aureus (infrequent cause)
Gram – pneumoniae	very very unusual
Iatrogenic pneumoniae:	Up to 50% of time don’t know etiologic agent. Hence, imperic treatment of CAP. Therefore, treatment includes treatment for pneumococcus and atypical.
Alcoholism	anaerobic, gram -, pneumococcus, Klebsiella
COPD	pneumococcus, h flu, moraxella catarallha
Post –Influenza	Staph aureus, pneumococcus
Nursing home	gram negative, s.aureus
HIV:	PCP
CNS disease	mycoplasma pneumoniae – bullous myringitis
Skin rash: erythema multiforme, nodosum	mycoplasma, fungi

Causative Agents of Pneumonia

(1) Streptococcus pneumoniae (pneumococcus)

Prevalence: MOST common pathogen of CAP

Susceptibility to infection: any defect in g globulin synthesis (IgG antibody): CLL, multiple myeloma, HIV, IgG deficiencies

Polysaccharide capsule: Antiphagocytic – inhibits neutrophil, therefore immune system needs help from IgG which sticks to the capsule. If you can’t produce it you are predisposed infection by encapsulated organisms. Therefore, difficulty in producing IgG: predisposes patients to strep pneumoniae

If anyone presents with recurring pneumococcus disease: think they may have a g globulin production problem

Pathogenesis: aspiration of infected mucus or inhalation from colonized nasopharynx Þ lobar pneumoniae. 4 stages

(1) Engorgement: engorgement of alveolar capillaries, edema, organism multiplication

(2) Red hepatization: diapedesis of erythrocytes (gross appearance resembles liver)

(3) Gray hepatization: Ý exudate, Ý leukocyte, capillary compression

Surface phagocytosis: PMN’s compress bacteria against alveolar surface to facilitate ingestion, enhanced by antibody

(4) Resolution: macrophages with cellular debris inside, no necrosis of alveolar walls or interstium, architecture remains intact

Clinical manifestations: lobar pneumoniae, minor UR symptoms for a few days, following by the herald rigor, pleuritic chest pain (Ý in intensity with aspiration or cough), accompanied with cough and rust colored sputum, shaking chills. Frequently can tell you when it hits them – very abrupt onset.

Physical exam: acutely ill patient with chest pain, splints on one side of thorax, consolidation present: flatness to percussion, egophony, bronchophony, whespered pectoriloquy, bronchial breathing

Lab findings: leukocytosis, leukopenia (with overwhelming infection): poor prognostic factor

CXR: dense homogenous shadows involving all or part of one or more lobes

Sputum study: gram positive diplococci Lancet shaped

Treatment: Ý dosage penicillin G (now resistant – 30%, mechanism alteration of penicillin binding protein can’t use b -lactamase antibiotics), 2^nd or 3^rd generation cephalosporin, vancomycin

Poor prognostic factors: alcoholic, malnourished, elderly, presence of bacteremia, leukopeia, involvement of 2 or 3 lobes (10% mortality)

Complications: empyema, meningitis

Immunization: >65, chronic lung or heart disease, no spleen, deficiency of IgG production, children with chronic disease

(2) Staphlococcal pneumonia

Prevalence: Typically follows Viral Influenza, or in elderly, chronically ill (but pneumococcus is still #1 pathogen post flu),

Clinical manifestations: sudden onset, fever, pleuritic chest pain, shaking chills, productive cough (sputum usually purulent or occasionally blood-streaked)

Physical exam: extremely ill, tachypnea, tachycardia, pleuritic pain

Lab: Gram + cocci in clusters, not a subtle finding on Gram stain, very prevalent organism during infection. PMN’s with intracellular and extracellular large, round cocci arranged in clusters

CXR: bronchopneumoniae Þ cavitations Þ abcess

Treatment: pencillinase-resistant semisynthetic penicillin (methicillin, nafcillin, cloxacillin, oxacillin) or 1rst generation cephalosporin, MRSA (vancomycin), treatment takes weeks

Complications: empyema, large abcesses

(3) Haemophilus influenza

What: pleomorphic, gram-negative coccobacillary organism. Polysaccharide capsule

Prevalence: Ý incidence in patients with disorders of g globulin synthesis

Clinical presentation: 2 groups

(1) Infants, alcoholics, immunodeficient: onset abrupt with chills, productive cough, pleural pain. Bacteremia common
(2) Chronic lung disease: gradual onset with low-grade fever, cough, sputum production, dyspnea, myalgias-arthralgias

CXR: lobar consolidation, patchy bronchopneumonia with multilobular infiltrates possible

Treatment: ampicillin-sulbactam, chloramphenicol, 2 or 3^rd generation cephalosporin, TMP-SMX

Prevention: immunization with purivied type b polysaccharide (PRP)

(4) Morzxella (Branhamella) Catarrhalis

Incidence: Chronic Bronchitis

What: gram negative kidney bean-shaped diplococcus, long axes paired side-to-side. Produces b lactamase

Clinical Manifestations: Seen with COPD patients, mean age > 60, or underlying disease (corticosteroid usage, diabetes, malignancy) chills, pleuritic chest pain, bacteremia, high fever, myalgias, effusion, empyema

CXR: patchy bronchopneumonia

Treatment: 3^rd generation cephalasporin, tetracyclin, erythromycin, TMP-SMX, fluorinated quinolines

(5) Neisseria meningitidis – Meningococcal disease

When: before influenza or adenoviral infection

Clinical presentation: nothing distincitive, may be sudden or indolent

CXR: patchy, lobular, lobar infiltrates

(6) Klebsiella pneumoniiae (friedlander’s pneumonia)

What: pleomorphic, encapsulated, fat, gram-negative rod, grows aerobically

Clinical manifestations: sudden onset fever, cough, pleuritic chest pain

On admission: seriously ill, severe dyspnea, tachypnea, striking cyanosis, hyopotension

P exam: classic signs of consolidation

Lab findings: PMN’s with myuriad of short, fat, gram negative heavily encapsulated rods

CXR: massive consolidation

Treatment: immediate and intensive, cephalosprin plus an aminoglycoside

(7) Escherichia coli

When: GI or GU bacteremia

Who: middle aged to elderly with underlying disease (diabetes, cirrhosis, cardiac or chronic lung disease), alcoholics

CXR: patchy lower lobe bronchopneumonia, lobar consolidation with abcess also seen

(8) Legionellosis

What: pleomorphic bacillus stains faintly gram-negative

How: Water transmission, natural habitat is aquatic environments

Risk factors: smoking, ETOH, COPD, age, immunosuppression,

Clinical manifestations: Pontiac fever: acute, self-limited influenza like illness, Legionaire’s disease: fulminant pneumonia syndrome with high mortality. VERY AGGRESSIVE: patient dies in front of your face

Extrapulmonary manifestations: liver dysfunction, hypophosphatemia, diarrhea, abdominal pain, splenomegaly, renal dysfunction, pericarditis, myocarditis, aseptic meningitis.

Diagnosis: charcoal yeast extract agar, direct flourescent anitbody, urine serology, acute and convalescent serology

Sputum: variable

CXR: Infiltrates on periphery, bilateral Þ ARDS

Treatment: treat empirically, macrolide (erythromycin, azithromycin, clazithromycin), quinolone, rifampin (synergistic benefit)

(9) Mycoplasma pneumonia (atypical pneumonia)

Presentation: bad sore throatÞ ear aches, headache (viral presentation)Þ cough (dry, hacking, non-productive, incessant)

PE: moderately ill, paroxysms of nonproductive cough (severe) Bullous myringitis: inflamed tympanic membrane

Fine to medium rales

CXR: nodular, patchy, or perihilar infiltrates. 1 or 2 lobe involvement

Cold agglutinis: appears 1 to 4 weeks after onset

Serology: growth inhibition, ELISA, radoiprecipitation, complement fixation

Course: variable corse but recovery is the rule

Treatment: tetracyclines or erythromycin

(10) Chlamydia pneumoniae

TWAR agent: obligate intracellular gram-negative bacterium

Clinical manifestations: Mimics illnes due to mycoplasma. generally mild, protracted course, pharyngitis, hoarseness, URI, fever cough. RALES almost always rpesent

Who: Adult onset asthma

CXR: small foci of patchy bronchopneumonia, bibasilar interstitial infiltrates

Diagnosis: complement fixation, microimmunofluorescence

Treatment: tetracyclines, erythromycin, fluoroquinolones

(11) Ornithosis (psittacosis)

Defn: an acute pulmonary infection by Chlamydia psittaci:

Transmission: BIRDS!. Infection follows inhalation of dried excreta

Who: people who take care of birds

Clinical manifestations: 7-15 incubation period. Acutely ill Þ mild to moderate cough Þ sputum production

Pleural friction rub, jaundice, meningoencephalitis, splenomegaly, severe lymphadenopathy, pharyngitis

CXR: peribronchial peripheral infiltrates

Sputum: few PMN’s rarely evidence of secondary infection

Treatment: tetracycline

(12) Influenza pneumoniae

Presentation: Fulminant, severe, life threatening pneumoniae

Respiratory tract secretions: MONOCYTES, no polys, loaded with ciliated cells (influenza, adeno – shear off cells)

Hemorrhagic alveolitis

3 presentations: Feel bad – get better a day later

(1) primary influenza pneumonia
(2) Post influenza bacterial pneumoniae: acute rigor, pleurisy, cough
(3) Can’t find time when they were better

Complications: secondary bacterial pneumonia

Treatment: amantadine, vaccination

(13) Varicella zoster pneumoniae

Presentation: Always presents after rash: no rash Þ no pneumonia

Bilateral lower lung pneumoniae

Diagnosis: respiratory multinucleated giant cell (typical of herpes), cerebriform nucleus

Treatment: acyclovir (IV)

(14) Adenovirus

When: winter

Transmission: intimate contact or aerosolization of infected secretions

Presentation: fever, headache, nasal congestion, haorseness and paroxysms of cough

PE: cervical lymphadenopathy, laryngitis, rlases

(15) Hantavirus

Presentation: fever and unexplained adult respiratory distress syndrome

Reservoir: rodents