Exam 3: relevant lab tests and how patients present

Question 1

infectivity vs pathogenicity

Answer 1

• infectivity: ability to infect

- pathogenicity: ability to cause disease

Question 2

Virulence

Answer 2

• measure of severity of disease

Question 3

Colateral damage effect

Answer 3

• using broad spectrum too long causes effects elsewhere such as microbiome
• want to switch to more specific

Question 4

Empiric Treatment

Answer 4

• broad spectrum, want to cover everything

Question 5

Non-specific signs of infection (4)

Answer 5

• leukocytosis (increased WBC count)
• elevated immunoglobulins (non-specific antibodies)
• physical evidence: pain, swelling, inflammation
• radiological evidence

Question 6

agranular WBC

Answer 6

• lymphocytes

- monocytes

Question 7

granular WBC

Answer 7

• basophils, neutrophils, eosinophils

Question 8

Macrophage

Answer 8

• bone-marrow derived phagocytic cell

- process and present antigens to lymphocytes

Question 9

Eosinophils can/cannot phagocytose?

Answer 9

• no

Question 10

T-lymphocytes

Answer 10

thymus derived lymphocytes involved in cell-mediated immunity

Question 11

Get excessive what in sepsis?

Answer 11

• inflammation

- causes dilation of blood vessels w/ release of NO

Question 12

Desguamation

Answer 12

• epithelial cell turnover at body surfaces removes large # of adhering microbes

Question 13

What is a fever?

Answer 13

• > 100.4

- hypothalamus reaction to IL-1, tumor necrosis factor, alpha-interferon

Question 14

Inflammatory mediators of infections and response (3)

Answer 14

• C reactive protein (CRP)
• Erythrocyte sedimentation rate (ESR)
• Procalcitonin

Question 15

C-reactive protein (CRP)

Answer 15

• inflammatory mediator of infection and response
• non-specific, acute-phase reactant
• binds to pathogen polysaccharides, activates classical complement pathway
• rapid half life

Question 16

What is problem with CRP being non-specific?

Answer 16

• do not truly know if infection-mediated event, need to measure in combo with other symptoms

Question 17

Erythrocyte Sedimentation Rate (ESR)

Answer 17

• inflammatory mediator of infections and response
• non-specific measure of inflammation
• rate at which RBCs settle in 1 hour
• slow response to infection

Question 18

Pro-calcitonin

Answer 18

• inflammatory mediators of infections and response
• precursor of hormone calcitonin
• rapid response to bacterial infection
• currently used to guide need for antibiotics in septic patients
• way to tell when can switch to less potent antibiotic or stop treatment

Question 19

B-lymphocytes

Answer 19

• derived from bone marrow

- produce immunoglobulins IgG, IgA, IgM, IgD, IgE

Question 20

specific immune system defense: immunoglobulins

Answer 20

• bind and fix complement: activates host defense
• neutrophil activation
• celll-free lysis
• develop specific antibodies
• neutralize toxins
• virus neutralization

Question 21

Making the diagnosis (broad)

Answer 21

• clinical signs and symptoms (fever, WBC, HR, BP)

- site-specific (imaging, localized inflammatory response i.e. sputum, puss, redness)

Question 22

Fever and hypothermia

Answer 22

• <95 degrees just as bad as >104 with community acquired pneumonia -
• fever pattern not diagnostic but suggestive

Question 23

WBC

Answer 23

• normal 5-10.5 ^3
• < 3 poor pronosis
• elevated WBC normal immune response (may exceed 40)
• lower in elderly and malnourished
• included phagocytes and lymphocytes

Question 24

Dramatically increased WBC could say what?

Answer 24

• may be functionally immunocompromised

- myeloproliferative states (bone marrow making too much)

Question 25

Blood Culture

Answer 25

- two sets 4 bottles total - each set one aerobic one anaerobic - sterilize site of collection - greater sensitivity with greater volume of blood - draw from two sites to distinguish contaminants - grow in 24-48 hours - ID and sensitivity in ADDITIONAL 24 hours - significant results: potentially any organism.. ESP gram negative - about 3% contamination rate usually with skin flora (esp staph epidermidis) - may be true pathogen if in multiple bottles, patient is symptomatic, and foreign device in place

Question 26

Urine Culture- clean catch (4 things)

Answer 26

- Bacteriuria - Pyuria - Leukocyte Esterase - Nitrite

Question 27

Bacteriuria in urine culture

Answer 27

- 100,000 cfu/mL is significant for Enterobacteriaceae (usually E. coli) in asymptomatic women - lower threshold w/ other bugs, men, w/ symptoms

Question 28

Pyuria in urine culture

Answer 28

- presence of pus in urine - >5-10 WBC/HPF = to 50-100 cells/ mm3

Question 29

Leukocyte esterase in urine culture

Answer 29

- released by WBC in event of inflammatory processes - Neg or Trace - trace categorized as small medium or large - dipstick 75-96% sensitive for Pyuria

Question 30

Nitrite in urine culture

Answer 30

- bacterial metabolism byproduct - positive in presence of enteriobacteriaceae - present when UTI due to gram - (usually E. coli)

Question 31

CSF fluid culture

Answer 31

- Bacterial Meningitis * high WBC * high protein * low glucose * gram stain positive usually * culture usually positive * bacterial antigen detected 50-100% of tiem i. e. latex agglutination

Question 32

Respiratory Culture: Sputum

Answer 32

- Sputum: highly controversial - good sample if >25 PMN cells, < 10 squamous cells, >10 WBC/Squamous - Yield 29-90% for hospitalized patients - >80% specificity for pneumococcal pneumonia - trachea aspirate slightly better but invasive

Question 33

Respiratory Culture: Bronchial Alveolar Lavage

Answer 33

- Bronchial-Alveolar Lavage (BAL) - INVASIVE - wash then brush cells - very high sensitivity - specificity 78-100%

Question 34

Outcomes in pneumonia invasive vs non-invasive culture methods

Answer 34

- no significant difference