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10-28-b Pneumonia in the abnormal host
- Pathophysiology: aspiration of oral content into lung
- Occurs frequently in many adults – as many as ½ adults aspirate small amounts of oral contents during sleep
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Healthcare-Associated Pneumonia
- Conversion of normal flora
- Within 48-72 hours ill patients converted their normal predominantly anaerobic flora to gram-negative aerobic bacilli:
- One mechanism may involve the decrease in production of fibronectin in illness, which promotes colonization by the normal flora that bind to the fibronectin:
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Definition:
- >/= 48 hours after admission and excluding infection incubating at time of admission:
- Indidence 5-10 cases/100 admissions
- Increased with mechanical ventilation in the ICU setting
- Duration of ICU stay and mechanical ventilation are major risk factors:
- Ventilator-Associated Pneumonia (VAP)
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Clinical, Radiologic and Lab findings
- Common things as you’d see with community acquired:
- Fever
- Cough
- Purulent sputum
- New or progressive pulmonary infiltrate
- Leukocytosis
- Gram’s stain, and growth of bacteria in cultures of sputum, tracheal aspirate, pleural fluid, or blood
- The problem is in the hospital: the symptoms might not be necessarily fro pneumonia, so have confounding factors
- Sequelae of healthcare associated pneumonia
- Healthcare associated pneumonia increases!:
- More likely to die FROM pneumonia rather that WITH pneumonia
- Much higher mortality than other common hospital infections
- You can die from pneumonia even if you kill all the bacteria – because of damage to the lungs
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Pathophysiology
- Selection of resistant organisms:
- Use of antibiotics in hospitals sets the epidemiologic stage for multiply-resistant gram negative pathogens and possibility of spread from patient to patient to staff, to patient, and medical instruments
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Aspiration pneumonia vs. pneumonitis
- Not all aspiration are pneumonia:
- Episodes of aspirations pneumonitis generally resolve within 48-72 hrs unless they become infected
- Greater risk >/= years of age, obesity, COPD, etc.
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Risk Factors for Aspiration
- Almost always because of anesthesia
- Surgery
- Instrumentation of the respiratory tract
- Anesthesia
- Use of narcotics and sedative
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Microbiology of healthcare associated pneumonia
- Early healthcare associated pneumonia
- S. pneumoniae, H. Influenzae and oxacilin sensitive, S. aureus and the gram-negative pathogens - e.coli, klebsiella spp and proteus spp
- Many of these see in community, not that much resistance
- Don’t want to treat because risk leaving resistant bacteria, will resolve
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Late onset healthcare associated pneumonia
- P. aeruginosa, oxacillin-resistant S. aureus, and Acinetobacter spp.:
- Other gram negative strans that are usually multi-antibiotic-resistant
- Anaerobes are not routinely seen
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Pseudomonas aeruginosa
- Oxydase positive and a non-lactose fermenting:
- Small, thin Gram negative rods
- Ubiquitous in soil and water
- Generally considered an aerobic GNR but will grow anaerobically if NO3 is present as an electron receptor
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Pseudomonas pneumonia
- Pseudomonas aeruginosa is predominantly a healthcare-associated pathogen or immunocompromised host:
- Primary pneumonia results from aspiration of colonized secretions
- Progression to pneumonia may be rapid with severe illness and life-threatening infection
- CXR typically show bronchopneumonia either unilateral or bilateral
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Chronic pseudomonas infection
- Chronic infection of the lower respiratory tract is generally caused by alginate-producing, mucoid strains of P. aeruginosa:
- Most frequently with cystic fibrosis and also some patients with AIDS
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Treatment of pseudomonas
- Antipseudomonal beta-lactam (piperacillin, aztreonam, imipenem, cefepime, or ceftazidime):
- AND:
- Aminoglycoside – such as gentamicin, tobramycin, or amikacin:
- Aminoglycosides have poor penetration into pulmonary secretions and are less effective in acidic environment of purulent secretions
- Quinolones – ciprofloxacin have excellent activity and may be added to the regimen or replace the aminoglycosides:
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Burkholderia
- Used to be B. cepacia:
- Seen in patients with cystic fibrosis near the end stage of disease: and after multiple antibiotic treatment
- HIGHLY RESISTANT
- Also need always a travel history
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Strenotrophomonas Maltophilia
- Seen in patients treated with multiple antibiotics:
- Intrinsically resistant to the carbapenems like imipenem because of the zinc metallo-beta-lactamase:
- Frequently only sensitive to trimethoprim-sulfamethoxazole:
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Acinetobacter
- Another in the line of highly resistant gram-negative pathogens:
- May be sensitive to only one or nor antibiotics
- Seen in troops in Iraq, especially in wounds. Unclear why it is so common there:
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Treatment recommendations: early hospital acquired pneumonia
Therapy similar to community acquired therapy, with a little bit more gram negative activity
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Treatment Recommendations: early hospital acquired pneumonia
- Consder highly resistant bacteria.
- Cephalosporin, carbipenem,
- An anti-beta lactam
- And aminoglycoside
- AND if have MRSA, then Vancomycin
- Want to have something that covers pseudomonas: an anti-pseudomonas beta lactam + aminoglycoside or a quinolone
- To cover legionella: respiratory fluoroquinolone or a macrolide
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