Chain of Infection - ANSWER 1)Infectious agent= organism with ability to cause disease;
greater virulence, invasiveness, and pathogenicity => increased odds of infection
2) Reservoir: place where microbes can persist and reproduce
3) Portal of Exit: way for microbe to leave the reservoir
4) Mode of transmission: method of microbe transfer from one place to another
5) Portal of entry: opening that allows microbe to enter host
6) Susceptible host: Lacks immunity or physical resistance to prevent invasion by microbe
Is a circle; each link must be present in sequential order for infection to occur
Virulence - ANSWER Measure of microbe's ability to invade and create disease
Depends on ability to:
Survive in environment between hosts
Transmit between hosts (moving; adherence)
Proliferate
IgM - ANSWER Pentamer; primary response, short-lived (<6 months); best at fixing com-
plement
IgG - ANSWER Monomer; main blood antibody, secondary response; longer lived. opsoni-
zation and toxin neutralization. 4 subclasses
Physical barriers - ANSWER Skin; fever; secreted antimicrobials; innate immunity
1
,Complement system - ANSWER 11=protein cascade; classically activate by ab:ag com-
plexes; alternate by pathogen surfaces
Skin defects; examples and associated pathogens - ANSWER Wounds, burns, trauma, se-
rious derm problems, indwelling devices, injections. Skin flora- S. aureus, CNS, strep pyo,
corynebacteria, malassezia furfur
Mucous membrane barrier defects; examples and associated pathogens - ANSWER
chemo-induced mucositosis, head/neck trauma, smoking, inhalational injury, antacids/PPIs.
Resident flora- anaerobes, aerobic GNR, candida, enteroccus, bovis
Body passage obstruction; examples and associated pathogens - ANSWER Tumors, for-
eign bodies, stones, cystic fibrosis. Resident flora overgrow or invade; site-specific.
Abnormal number or function of granulocytes - ANSWER Leukemia, chemo, congenital
disorders, diabetes. If short term (< 2 wks) then aerobic GNR, Sa, CoNS. IF long term, add
fungi (candida, t. glabrata, aspergillus)
Abnormalities of cell-mediated immunity - ANSWER BMT, HIV, steroids, malnutrition, 3rd
tri pregnancy. Bacteria: Intracellular pathogens (listeria, salmonella, mycobacteria, nocardia,
legionella).
Fungi: candida, Cryptococcus, coccidioides, histoplasma. Virus: Herpes group
Also toxoplasma and strongyloides.
abnormalities of humoral immunity - ANSWER BMT, HIV, some cancers, aging. Strep
pneumo, encapsulated H. flu, Neisseria meningitidis
Preventing infection for immunocompromised patients - ANSWER Take thorough patient
history. Prepare before starting with all vaccines, procedures, line placement, screening.
Support gastric acidity. Prevent exposures with awesome hygiene, approp food and water
precautions, visitor education, no flowers or plants, and possible abx prophy (for infections
that might reactivate or high-risk for pneumocystis)
2
,Mycoplasma spp. - ANSWER No cell wall --> limited abx choices. Cause atypical pneumo-
nia. Usually diagnosed by serology
Chlamydiae - ANSWER obligate intracellular parasites. Elementary body=infectious, retic-
ulated= intracellular. DFA or ELISA for detection of antigen is most common. Can also detect
antibodies.
Rickettsiae - ANSWER obligate intracellular parasites. arthropod vectors. Rarely culturing;
detected by serology using ELISA for antibodies.
Textbook viral replication cycle - ANSWER 1. Attachment 2. penetration/entry 3. replica-
tion 4. maturation/assembly 5. release
Sensitivity - ANSWER % of true + who test +; inherent to test
Specificity - ANSWER % of true neg who test neg; inherent to test
PPV - ANSWER Likelihood that a + test represents a true case (% T+/all+); depends on the
test and on prevalence of disease in population
NPV - ANSWER Likelihood that a negative test result is a true non-case (%TN/allN); de-
pends on test and population prevalence
CSF analysis- bacterial mening - ANSWER 1000-5000 WBCs, mostly PMNs. Increased pres-
sure. Increased protein . Decreased glucose. Bacteria seen on smears.
CSF analysis- viral mening - ANSWER Pressure, glucose normal. Lymphocytes seen, but
few WBC in general. Protein normal-elevated. Nothing on smears.
3
, CSF analysis- fungus mening - ANSWER Pressure variable. Glucose low, protein high.
WBCs vary, but lymphocytes predominate. India ink smear +.
CSF analysis- TB mening - ANSWER Pressure variable. Glucose low to megalow. WBCs
vary, mostly lymphocytes. Protein elevated. AFB stain +
Cold Agglutinins test - ANSWER Used to detect antibodies for Mycoplasma pneumoniae
or mononucleosis. Positive test is high titer, with resp Sx indicates M. pneumo infection, viral
pneumo, or primary atypical pneumo
CRP test - ANSWER Serum sample looking for the CR protein; normal value is none or low
CRP. Indicates current acute inflammation
Liver Function Tests - ANSWER chemistry assays on blood; looking for various things in-
cluding enzymes, bilirubin, ammonia, and albumin. Generally higher is worse. Helps detect
liver problems, differentiate among liver problems, measure liver damage, and follow re-
sponse to Tx.
Arterial Blood Gas (ABG) - ANSWER blood from artery, measures oxygen and CO2 ten-
sion, pH. Assesses gas exchange, which is helpful in recognizing pneumonia
Sedimentation rate - ANSWER Measures rate of RBCs sinking; faster indicates acute infec-
tion/inflammation (among other things, is not very specific)
Toxin production tests - ANSWER Many ways of doing, including EIA and HPLC. limulus
amebocyte lysate tests for endotoxin.
Weil-Felix agglutination - ANSWER Serum, test for rickettsial antibodies. High titer or 4x
rise in titer indicates rickettsial infection.
4
greater virulence, invasiveness, and pathogenicity => increased odds of infection
2) Reservoir: place where microbes can persist and reproduce
3) Portal of Exit: way for microbe to leave the reservoir
4) Mode of transmission: method of microbe transfer from one place to another
5) Portal of entry: opening that allows microbe to enter host
6) Susceptible host: Lacks immunity or physical resistance to prevent invasion by microbe
Is a circle; each link must be present in sequential order for infection to occur
Virulence - ANSWER Measure of microbe's ability to invade and create disease
Depends on ability to:
Survive in environment between hosts
Transmit between hosts (moving; adherence)
Proliferate
IgM - ANSWER Pentamer; primary response, short-lived (<6 months); best at fixing com-
plement
IgG - ANSWER Monomer; main blood antibody, secondary response; longer lived. opsoni-
zation and toxin neutralization. 4 subclasses
Physical barriers - ANSWER Skin; fever; secreted antimicrobials; innate immunity
1
,Complement system - ANSWER 11=protein cascade; classically activate by ab:ag com-
plexes; alternate by pathogen surfaces
Skin defects; examples and associated pathogens - ANSWER Wounds, burns, trauma, se-
rious derm problems, indwelling devices, injections. Skin flora- S. aureus, CNS, strep pyo,
corynebacteria, malassezia furfur
Mucous membrane barrier defects; examples and associated pathogens - ANSWER
chemo-induced mucositosis, head/neck trauma, smoking, inhalational injury, antacids/PPIs.
Resident flora- anaerobes, aerobic GNR, candida, enteroccus, bovis
Body passage obstruction; examples and associated pathogens - ANSWER Tumors, for-
eign bodies, stones, cystic fibrosis. Resident flora overgrow or invade; site-specific.
Abnormal number or function of granulocytes - ANSWER Leukemia, chemo, congenital
disorders, diabetes. If short term (< 2 wks) then aerobic GNR, Sa, CoNS. IF long term, add
fungi (candida, t. glabrata, aspergillus)
Abnormalities of cell-mediated immunity - ANSWER BMT, HIV, steroids, malnutrition, 3rd
tri pregnancy. Bacteria: Intracellular pathogens (listeria, salmonella, mycobacteria, nocardia,
legionella).
Fungi: candida, Cryptococcus, coccidioides, histoplasma. Virus: Herpes group
Also toxoplasma and strongyloides.
abnormalities of humoral immunity - ANSWER BMT, HIV, some cancers, aging. Strep
pneumo, encapsulated H. flu, Neisseria meningitidis
Preventing infection for immunocompromised patients - ANSWER Take thorough patient
history. Prepare before starting with all vaccines, procedures, line placement, screening.
Support gastric acidity. Prevent exposures with awesome hygiene, approp food and water
precautions, visitor education, no flowers or plants, and possible abx prophy (for infections
that might reactivate or high-risk for pneumocystis)
2
,Mycoplasma spp. - ANSWER No cell wall --> limited abx choices. Cause atypical pneumo-
nia. Usually diagnosed by serology
Chlamydiae - ANSWER obligate intracellular parasites. Elementary body=infectious, retic-
ulated= intracellular. DFA or ELISA for detection of antigen is most common. Can also detect
antibodies.
Rickettsiae - ANSWER obligate intracellular parasites. arthropod vectors. Rarely culturing;
detected by serology using ELISA for antibodies.
Textbook viral replication cycle - ANSWER 1. Attachment 2. penetration/entry 3. replica-
tion 4. maturation/assembly 5. release
Sensitivity - ANSWER % of true + who test +; inherent to test
Specificity - ANSWER % of true neg who test neg; inherent to test
PPV - ANSWER Likelihood that a + test represents a true case (% T+/all+); depends on the
test and on prevalence of disease in population
NPV - ANSWER Likelihood that a negative test result is a true non-case (%TN/allN); de-
pends on test and population prevalence
CSF analysis- bacterial mening - ANSWER 1000-5000 WBCs, mostly PMNs. Increased pres-
sure. Increased protein . Decreased glucose. Bacteria seen on smears.
CSF analysis- viral mening - ANSWER Pressure, glucose normal. Lymphocytes seen, but
few WBC in general. Protein normal-elevated. Nothing on smears.
3
, CSF analysis- fungus mening - ANSWER Pressure variable. Glucose low, protein high.
WBCs vary, but lymphocytes predominate. India ink smear +.
CSF analysis- TB mening - ANSWER Pressure variable. Glucose low to megalow. WBCs
vary, mostly lymphocytes. Protein elevated. AFB stain +
Cold Agglutinins test - ANSWER Used to detect antibodies for Mycoplasma pneumoniae
or mononucleosis. Positive test is high titer, with resp Sx indicates M. pneumo infection, viral
pneumo, or primary atypical pneumo
CRP test - ANSWER Serum sample looking for the CR protein; normal value is none or low
CRP. Indicates current acute inflammation
Liver Function Tests - ANSWER chemistry assays on blood; looking for various things in-
cluding enzymes, bilirubin, ammonia, and albumin. Generally higher is worse. Helps detect
liver problems, differentiate among liver problems, measure liver damage, and follow re-
sponse to Tx.
Arterial Blood Gas (ABG) - ANSWER blood from artery, measures oxygen and CO2 ten-
sion, pH. Assesses gas exchange, which is helpful in recognizing pneumonia
Sedimentation rate - ANSWER Measures rate of RBCs sinking; faster indicates acute infec-
tion/inflammation (among other things, is not very specific)
Toxin production tests - ANSWER Many ways of doing, including EIA and HPLC. limulus
amebocyte lysate tests for endotoxin.
Weil-Felix agglutination - ANSWER Serum, test for rickettsial antibodies. High titer or 4x
rise in titer indicates rickettsial infection.
4
