CAP Flashcards
Microorganisms gain access to the lower respiratory tract in several ways. The most common is
Aspiration
inflammatory mediators that results in fever
interleukin 1 and tumor necrosis factor
stimulate the release of neutrophils and their attraction to the lung, producing both peripheral leukocytosis and increased purulent secretions
interleukin 8 and granulocyte colony-stimulating factor
What phase represents the presence of a proteinaceous exudate—and often of bacteria—in the alveoli
Initial phase-edema
presence of erythrocytes in the cellular intra-alveolar exudate. neutrophil influx is more important with regard to host defense.
Second stage red hepatization
no new erythrocytes are extravasating, and those already present have been lysed and degraded. The neutrophil is the predominant cell, fibrin deposition is abundant, and bacteria have disappeared
Third stage gray hepatization
This phase corresponds with successful containment of the infection and improvement in gas exchange
Gray hepatization
macrophage reappears as the dominant cell type in the alveolar space, and the debris of neutrophils, bacteria, and fibrin has been cleared, as has the inflammatory response
Resolution
most common pattern in nosocomial pneumonias
Bronchopneumonia pattern
Most common pattern bacterial CAP
Lobar pneumonia
Major risk factor for anaerobic pneumonia
combination of an unprotected airway (e.g., in patients with alcohol or drug overdose or a seizure disorder) and significant gingivitis
Possible etiology
Risk factor: Travel to Ohio or St. Lawrence river valley
Histoplasma capsulatum
infect patients who have recently been hospitalized and/or received antibiotic therapy or who have comorbidities such as alcoholism, heart failure, or renal failure
Enterobacteriaceae
Tend to infect patients with severe structural lung disease, such as bronchiectasis, cystic fibrosis, or severe COPD
P aeruginosa
Risk factors for this infection include diabetes, hematologic malignancy, cancer, severe renal disease, HIV infection, smoking, male gender, and a recent hotel stay or ship cruise.
Legionella
sensitivity and specificity of the findings on physical examination
58% 67%
To be adequate for culture, a sputum sample must have
> 25 neutrophils and <10 squamous epithelial cells per low-power field
Percentage of cultures of blood from patients hospitalized with CAP are positive
5-14%
sensitivity and specificity of the Legionella urine antigen test are as high as
70, 99%
The pneumococcal urine antigen test is also quite sensitive and specific
70, >90%
The standard for diagnosis of respiratory viral infection
PCR of nasopharyngeal swabs
may be of use in the identification of worsening disease or treatment failure
C reactive protein
may play a role in distinguishing bacterial from viral infection, determining the need for antibacterial therapy, or deciding when to discontinue treatment
Procalcitonin
prognostic model used to identify patients at low risk of dying
Pneumonia Severity Index PSI
severity-of-illness score
CURB 65 criteria
CURB-65 criteria include five variables
confusion (C) urea >7 mmol/L (U) respiratory rate ≥30/min (R) blood pressure, systolic ≤90 mmHg or diastolic ≤60 mmHg (B) age ≥65 years
Pneumococcal resistance to β-lactam drugs is due solely to
low-affinity penicillin-binding proteins
Resistance to Macrolide that results in high level resistance
arget-site modification caused by ribosomal methylation in 23S rRNA encoded by the ermB gene
Resistance to macrolide that results in low level resistance
efflux mechanism encoded by the mef gene (M phenotype)
Gene responsible for flouroquinolone resistance
topoisomerases II and IV from mutations in the gyrA and parC genes, respectively
Mycoplasma resistance to macrolides is on the rise as a result of binding-site mutation in
domain V of 23S rRNA
Methicillin resistance in S. aureus is determined by a gene which encodes for resistance to all β-lactam drugs.
mecA gene
typical hospital-acquired strain usually has what type of staphylococcal chromosomal cassette mec (SCCmec)
Tyep II or III
CA-MRSA usually has what type of staphylococcal chromosomal cassette mec (SCCmec)
Type IV
membrane-tropic toxin that can create cytolytic pores in polymorphonuclear neutrophils, monocytes, and macrophages
Panton-Valentine leukocidin
