Identification of Infectious Disease Processes

Report
Ready…Set…Go!
Carolyn Fiutem, MT(ASCP), CIC
Infection Prevention Officer, TriHealth
October 10, 2012
Recognize epidemiologically
significant organisms
Interpret results of lab tests
Identify indications for biologic
monitoring
Fundamental Principles of Infection and
Immunity
Colonization – organisms in or on a host; growth
but no tissue invasion or damage
Infection – entry of an infectious agent in
tissues of a host; growth and create symptoms
Contamination – presence of microorganisms
on inanimate objects, skin, or in substances
Components of the Infectious Disease Process
SUSCEPTIBLE HOST
A person who cannot
resist a
microorganism
invading the body,
multiplying, and
resulting in infection.
The host is
susceptible to the
disease, lacking
immunity or physical
resistance to
overcome the
invasion by the
pathogenic
microorganism.
INFECTIOUS AGENT /Causative Agent
A microbial organism with the ability to cause disease. The greater the organism's virulence
(ability to grow and multiply), invasiveness (ability to enter tissue) and pathogenicity (ability
to cause disease), the greater the possibility that the organism will cause an infection.
RESERVOIR
A place within which
microorganisms can thrive and
reproduce.
PORTAL OF EXIT
A place of exit providing a
way for a microorganism
to leave the reservoir.
PORTAL OF ENTRY
An opening allowing
the microorganism to
enter the host.
MODE OF TRANSMISSION
Method of transfer by which the organism moves or is carried from one place to another.
Virulence
Environmental survival in transit
BBP in blood outside the body,
Protection against drying, Vectors
Effective mechanism for
transmission
Vectors, Motility, Airborne, Fomites
Ability to attach
Electrostatic charge, Adhesion
Reproduction/Proliferation
Enzymes, Endotoxins, Capsules, Biofilms
Invasion and Dissemination
Rigid cell wall, Cell surface components,
ability to alter cell surface, Deterrents to
intracellular killing after phagocytosis
Bacterial Toxins
Exotoxins – potent toxin
secreted by a bacterial cell
Excreted in environment
Gram-positive bacteria
More susceptible to heat
Neutralized by antibodies
Enzymatic activity
PVL of MRSA, and Toxins A/B of C. diff
Endotoxin – heat-stable toxin in
cell wall; pyrogenic; increase
capillary permeability
Surface of GNRs
Partially neutralized by antibodies
Produce physiologic changes in host
Cholera toxin – fluid in the GI tract
E. coli 0157
T-lymphocytes &
mononuclear phagocytes
Originate in bone marrow
Migrate to thymus
fetus/infancy
T-cells from spleen, lymph
nodes, bone marrow
Receptors on surface of Tlymphocytes
Review cellular immune
response
Cytokines
Interleukin – 1: pyrogen, stimulate macrophage chemotaxis
Interleukin – 2: made by CD4, enhance NK cell activity
Interleukin – 4: made by T-cells and mast cells, stimulate growth
Interleukin – 6: pyrogen, B-cell/T-cell differentiation
Interferon: made by WBCs & fibroblasts; inhibit virus growth; α, β, γ
Tumor Necrosis Factorcause protein catabolism in host w/ loss of
muscle mass
Lymphotoxin: promotes inflammation; stimulates neutrophils
Granulocyte and Monocyte Stimulating Factors - reproduction
T-lymphocytes
CD3 surface marker – IDs them
CD4 marker – helper lymphocytes for phagocytosis, release cytokines,
long-term memory (vaccines)
CD8 cells – cytotoxic and suppressor lymphocytes
Natural killer cells – lyse tumor & virus infected cells
Cellular Sources of
Antibodies
Precursors from fetal liver
and bone marrow to spleen
and lymph nodes
Antibody producing
plasma cells
Classes of Immunoglobulin
IgG – late occurring in
Immune response (I’ve got
it and it’s gone)
IgM – first reacting , present for only ~ 6 months (I’m mopping it up)
IgA – secretory antibody, plasma cells in mucous membranes
IgD – surface of lymphocytes – antigen specificity
IgE – allergy inducing; histamine & inflammatory substances; mucous
membranes
Genetic Constitution
Caucasians, African-Americans, Asians,
Alaskan/Hawaiian natives
Mechanical Barriers
Skin, mucous membranes, normal flora
Physiological Barriers
Fever, secretions, motility
Vascular Circulating Defenses
Natural/cross-reactive antibodies, fibronectin,
estrogens, circulating WBCs
•Activated by contact with IgG or IgM or certain microorganisms
•Genetic deficiencies
10
Neutrophils (Polys)
• Most dominant WBC (40-70%)
• “First Responder”
• Acts against pyogenic (pus-forming)
bacteria
• Life expectancy ~ 7 hours in
circulatory system
• Large reserve in bone marrow
• Leukopenia – can be poor
prognostic indicator
• Hypersegmentation – suggest B12
or folate deficiency
Neutrophil Ratios
Degenerative Left Shift – increase in bands with no
leukocytosis; poor prognosis
Regenerative Left Shift – increase in bands with
leukocytosis; good prognosis
Right Shift – few bands with increase in segmented
neutrophil seen in liver disease, hemolysis, drugs,
cancers, allergies, or megaloblastic anemia
Hypersegmentation – with no bands is seen in
megaloblastic anemia and chronic morphine addiction
Myeloid Left Shift – Bands, Metamyelocytes (Metas),
Myelocytes, Promyelocytes (Pros), Blasts
Neutropenia
• Acute overwhelming bacterial infections – poor
prognosis
• Viral infections
• Rickettsial and some parasitic diseases
• Drugs, chemicals, radiation, toxic chemicals
• Anaphylactic shock
• Severe renal disease
• Sepsis due to E. coli – reduced survival of polys
• Hormonal Disorders
Neutropenia in Neonates
• Maternal neutropenia
• Maternal drug ingestion
• Maternal isoimmunization to fetal WBCs
• Inborn errors of metabolism (i.e., maple syrup
urine disease)
• Immune deficits
• Myeloid disorders
• Defective intrinsic factor secretion
Absolute WBC Counts
1.
2.
3.
4.
5.
6.
Relative Number = percentage
Absolute Count = Percentage X Total WBC Ct.
Can have normal WBC count yet be neutropenic
Need to look at WBC count and differential
Normal WBC ranges:
Adults ~ 3.5-10, 000
Newborns ~ 9-30,000
2 weeks ~ 5-20,000
1 yr ~ 6-18,000
4 yr ~ 5500-17,000
10 yr ~ 4500 – 13,500
Basophils
0-1% of WBCs
Mast Cells are tissue basophils
Secrete histamine, seratonin,
& prostaglandins – increase
blood flow to area
Hodgkin’s Disease
Parasitic infections
Inflammation
Allergy
Sinusitis
After splenectomy
TB
Smallpox, Chickenpox
Influenza
Eosinophils
1-4% of WBCs
Are cytotoxic
NAACP….
Neoplasm
Asthma/Allergy
Addison’s Disease
Collagen/Vascular Disease
Parasitic Infections
Lymphocytes
25-40% of WBCs
Fight viral infections
Pertussis
Chronic granulomatous
diseases, i.e., TB
Crohn’s disease
Ulcerative Colitis
Addison’s Disease
Brucellosis
Lymphopenia
Chemotherapy
After administration of cortisone
Obstruction of lymphatic drainage, Whipple’s
disease or tumors
Hodgkin’s disease
HIV/AIDS
Trauma
Monocytes
Fight severe infection
via phagocytosis
3-7% of WBCs
Bacterial infections
TB
SBE
Syphilis
Parasitic, fungal,
rickettsial diseases
20
Which of the following is not a mechanical
barrier?
a. Intact skin
b. Mucous membranes
c. Secretions
d. Normal bacterial flora
Knowledge Check…
What is the name for a substance that prevents
water-soluble elements such as antibiotics and
disinfectants form reaching pathogens?
a. Cell wall
b. Biofilm
c. Sludge
d. Biocarbon
Knowledge Check…
Patients with cell-mediated immunity dysfunction
are susceptible to infections attributed to
pathogenic intracelluar bacteria. Examples of
these organisms include:
1. Salmonella typhi
2. Bacteroides fragilis
3. Listeria monocytogenes
4. Staphylococcus aureus
a.
b.
c.
d.
2,3
1,3
1,2
3,4
Knowledge Check…
Which organism found in food poisoning causes
the most rapid onset of symptoms?
a. Salmonella enteritidis
b. Shigella sonnei
c. Staphylococcus aureus
d. Escherichia coli
Knowledge check…
The IP is teaching nurses how to assess infection
risks in patients. Depletion of what cell type
provides the BEST indication of susceptibility to
most bacterial infections?
a. Monocyte
b. Eosinophil
c. Neutrophil
d. Lymphocyte
Knowledge Check…
1.
2.
3.
4.
a.
b.
c.
d.
Your patient has a low absolute neutrophil count. Of
the following choices, which is true of your patient?
They are especially susceptible to disease.
You can determine the absolute neutrophil count by
multiplying the total WBC count by the percentage of
mature and immature neutrophils.
The patient’s WBC count is between 4000 & 10,000.
The patient’s complement system will only be
activated through the alternate pathway
1
1&2
3
1, 2, & 4
Bacteria
Internal structures – familiarity
External structures – cell wall, glycocalyx, flagella, fimbriae
and pili
Size/Shape – 0.2-2 u X 2-8 u; cocci, rods, spirals
Replication – cell division every 15-24 hours
Genetic variation
Plasmids found in cytoplasm, circular pieces of DNA
Transformation – free DNA in cell
Transduction – DNA carried by bacteriophage (virus)
Conjugation – direct sharing of DNA
Mutations – random base pair substitution
Submicroscopic bacteria – Mycoplasma, Chlamydiae,
Rickettsiae
Yeasts
Single-celled, budding or
fission
2-60 u
Smooth, creamy colonies
Candida, Cryptococcus
Molds
Multinucleated network of
filaments (hyphae)
Can reproduce asexually or
sexually
Can reproduce via spores
Aspergillus, Rhizopus
Dimorphic fungi
Grow as yeast or fungi depending on conditions
Mold form at room temp (25°C)
Yeast form at body temp (37°C)
Histoplasma, Coccidioides, Blastomyces, Paracoccidioides
Viruses
Replicate only in cells of
host/reservoir
RNA or DNA in a protein
coat
Classified using genome,
number of strands and
presence or absence of
envelope
Parasites
Blood - Plasmodium
Protozoa - Giardia
Helminths – pinworm
Ectoparasites – scabies,
lice, bedbugs
Prions
Infectious pieces of proteins
Only replicate in cells of living organisms
Neurotropic
Untreatable and universally fatal
Creutzfeld- Jakob disease (CJD, vCJD) – transmissible spongiform
encephalopathy (TSE)
30
Microscopy – light & electron
Specimen Preparation – direct/wet prep, stains
Culture – agar, broth, biphasic, tissue
Antimicrobial Susceptibility Testing (AST)
Enzyme Immunoassay (EIA)
Latex Agglutination
DNA Probes
Polymerase Chain Reaction (PCR)
Serologic
Anatomic Pathology
General Laboratory
Bacteria – stains, culture, serology, molecular
Fungi: yeasts, molds – direct preps, culture,
biochemical tests, direct antigen tests, serology
Viruses – direct antigen tests, antibody tests,
tissue culture
Parasites – microscopy, serology
Mycobacteria – culture, molecular, direct
detection
Mycoplasma - serology
Chlamydiae – direct antigen tests
Rickettsiae/Other Tick-borne Microbes –
serology, ELISA
Disk Diffusion – Kirby Bauer
Broth Dilution – Minimum Inhibitory
Concentration (MIC); manual or automated
E-Test
Beta-lactamase – penicillins resistance
Disk Approximation – inducible clindamycin
resistance
Synergy Test – combinations of antibiotics
Hodge Test – Extended Spectrum Betalactamase in gnrs
Minimal Bacteriocidal Concentration (MBC)
Types of
ß – lactamases
produced by
Enterobacteriaceae
Examples
Broad Spectrum
TEM-1
TEM-2
SHV-1
Extended
Spectrum BetaLactamase
Hydrolyzes
Basic
Pens
Cephalosporins
Inhib by
CA
I
II
III
IV
Cephamycins
(FOX, CTE)
Carbapenems
(IMI, MERO)
AZT
Y
Y
Y/N
N
N
N
N
N
+/+++
TEM family
SHV family
Y
Y
Y
Y
Y
N
N
Y
++++
Amp-C
ACC
CMY
CFE
DHA
Y
Y
Y
Y
Y
Y
N
Y
N
CarbapenEmases
(NDM-1)
KPC
Y
Y
Y
Y
Y
Y
Y
Y
+++
IMP, GIM
Y
Y
Y
Y
Y
Y
Y
Y
++
OXA
Y
Y
Y
Y
Y
Y
Y
Y
+
Courtesy of Dr. Larry Gray
Antibiotic Stewardship
Surveillance
Antibiograms
Appropriate use of vaccines
Appropriate transmission-based precautions
Hand Hygiene
Barriers
Susceptible (S)
Intermediate (I)
Resistant (R)
Therapy/Treatment
Prophylactic Therapy
Empiric Therapy
Staphylococcus aureus
Ciprofloxacin
>=8
R
Clindamycin
>=8
R
Erythromycin
>=8
R
Gentamycin
<=5
S
Levofloxacin
>=8
R
Linezolid
2
S
Oxacillin
>=4
R
Penicillin G
>=0.5
R
Rifampin
<=0.5
S
Tetracycline
<=1
S
Tigecycline
<=0.12
S
Sulfa/Tri
<=10
S
Vancomycin
<=0.5
S
Gram positive coverage:
Penicillins (ampicillin, amoxicillin)
penicillinase resistant (Dicloxacillin,
Oxacillin)*
Cephalosporins (1st and 2nd
generation)*
Macrolides (Erythromycin,
Clarithromycin, Azithromycin)*
Quinolones (gatifloxacin, moxifloxacin,
and less so levofloxacin)*
Vancomycin* (MRSA)
Sulfonamide/trimethoprim*(Increasing
resistance limits use, very inexpensive)
Clindamycin*
Tetracyclines
Chloramphenicol (causes aplastic
anemia so rarely used)
Other: Linezolid, Synercid (VRE)
Gram negative coverage:
Broad spectrum penicillins (Ticarcillinclavulanate, piperacillin-tazobactam)*
Cephalosporins (2nd, 3rd, and 4th
generation)*
Aminoglycosides (Gentamicin;
nephrotoxic)*
Macrolides (Azithromycin)*
Quinolones (Ciprofloxacin)*
Monobactams (Azetreonam)*
Sulfonamide/trimethoprim*
Carbapenems (Imipenem)
Chloramphenicol
Pseudomonas coverage:
Ciprofloxacin*
Aminoglycosides*
Some 3rd generation cephalosporins
4th generation cephalosporins
Broad spectrum penicillins*
Carbapenem
Atypical coverage:
Macrolides (Legionella,
Mycoplasma,
chlamydiae)*
Tetracyclines (rickettsiae,
chlamydiae)*
Quinolones (Legionella,
Mycoplasma,
Chlamydia)*
Chloramphenicol
(rickettsiae, chlamydiae,
mycoplasma)
Ampicillin (Listeria)
Anaerobic coverage:
Metronidazole*
Clindamycin*
Broad spectrum
penicillins*
Quinolones (Gatifloxacin,
Moxifloxacin)
Carbapenems
Chloramphenicol
Antifungal spectrum of activity against common fungi.
© 2006 by the Infectious Diseases Society of AmericaAshley
E S D et al. Clin Infect Dis. 2006;43:S28-S39
Prompt institution of treatment
“Bug Factor” – virulence and susceptibility
“Drug Factor” – Activity of site of infection
“Host Factor” – co-morbids and
immunocompetence
“Site Factor” – easily accessible site by
antimicrobials
Problems with administration – timeliness,
storage, deterioration, patient compliance,
absorption failure
Renal/Liver Failure
40
Specimen quality is key
Need to reduce colonizing bacteria prior to
specimen collection – If you can touch the site
with your finger, the specimen will be
contaminated!
Refrigerate/keep cold when necessary
Use preservatives when applicable
Tissues/Body fluids, Anaerobic cultures, CSF – stat
specimens
Label all specimens at the bedside/where collected
with 2 patient identifiers and pertinent specimen
information (D/T coll, source/site, abx, who coll)
1.
2.
3.
4.
CSF should be clear &
colorless
Glucose 40-70 mg/dl
Protein 15-45 mg/dl
CSF Glucose = ~2/3
serum glucose
Bacterial Meningitis:
WBC = increased
Diff – neutrophils
Protein = marked
increase
Glucose =markedly
decreased
1.
2.
3.
4.
1.
2.
3.
4.
Viral (Aseptic) Meningitis:
WBC = increased
Diff – lymphs
Protein = moderate
increase
Glucose = Normal
TB/Fungal Meningitis:
WBC = increased
Diff – Lymphs and Monos
Protein = moderate to
marked increase
Glucose = Normal to
decreased
The validity of a culture report is dependent on
the quality of the specimen sent. To determine
if an expectorated sputum specimen is sputum
and not saliva, the gram stain should show:
a. < 10 epithelial cells per low power field (lpf)
b. > 10 epithelial cells/lpf and moderate polys
c. > 10 epithelial cells/lpf and many Pseudomonas
in culture
d. Many WBCs and organisms on low power field
To increase recovery of AFB from expectorated
or induced sputum, specimens should be
collected:
a.
b.
c.
d.
Once a week for 3 consecutive weeks
Every day for 1 week
First morning specimen for 3 consecutive days
Three specimens 1 hour apart on the same day
1.
2.
3.
4.
5.
Microorganisms are grown on culture media made of
an agar base. Additives to media vary according to
growth requirements of organisms and/or the desire to
select out a specific organism. Fastidious organisms
require______ media, and ______ media is used to
inhibit normal commensals.
Differential
Enrichment
Selective
Nutrient broth
Synthetic sheep blood agar
a. 1, 3
c. 3, 4
b. 2, 3
d. 5, 1
Gram stains classify an organism as grampositive or gram-negative. The determinant
factors for Gram stains are cell wall component
of:
a.
b.
c.
d.
Peptidoglycans
Lipids
Polysaccharides
Mycolic acids
A liquid stool specimen is collected from a 10 yo
boy at 9 p.m. The physician has ordered a
culture and O&P. The specimen is refrigerated
until 9 a.m. the following day, when the
physician calls and requests the laboratory to
look for amoebic trophozoites. The best course
of action is:
a. Request a fresh specimen.
b. Perform a concentration on the specimen.
c. Perform a trichrome stain on the specimen.
d. Perform a saline wet mount on the specimen.
When reviewing microbiology data looking for
isolates of MRSA, the laboratory does not use
methicillin for testing. Which of the following
antimicrobial agents is the MOST similar to
methicillin and is most commonly used in AST?
a.
b.
c.
d.
Carbenicillin
Oxacillin
Gentamicin
Amikacin
An IP is asked to review with a group of staff
nurses how to interpret ASTs. The susceptibility
test that allows a determination of the least
amount of antibiotic per milliliter that impedes
the growth of an organism is know as a:
a.
b.
c.
d.
Minimum inhibitory concentration (MIC)
Kirby-Bauer disk diffusion
Minimum bacteriocidal concentration
Serum-cidal levels
Not recommended
Costly
Requires special
procedures
No standards for
comparison
May have adverse
intervention implemented
When investigation
suggests a source or
reservoir
Use quantitative methods
Routine monitoring
Biological monitoring of
sterilization processes
Month culture colony
counts and endotoxin
testing of water and
dialysate in HDUs
Short term evaluations of
interventions implemented
as anew process or to stop
an outbreak
50
Normal Flora – commonly found on healthy
human body surfaces (endogenous source)
Colonization – microorganisms in the absence of
symptoms or deep tissue invasion
Asymptomatic Infection – viable organisms
without causing any obvious symptoms (latent
TB)
Opportunistic Infections – cause disease
primarily in immunodeficient hosts
Pathogenic Organisms – causes tissue damage
Infection – invasion by and multiplication of
organisms causing tissue damage and disease
Etiology (Organism)
Pathogenesis (Life cycle understanding)
Identification (S/S)
Diagnostic Testing
Incubation Period
Transmission-based Precautions
Treatment
Case Fatality
Anthrax (Class A)
Aspergillosis: environmental
Chicken pox/Herpes zoster
Conjunctivitis
Cryptosporidiosis
Dengue – Flaviviruses 1, 2, 3, 4
Foodborne Diseases
Hanta virus
Hepatitis – A, B, C, D, E
HIV
Influenza
Legionellosis
Measles
Meningitis – bacterial vs viral
Mumps
Pediculosis/Phthiriasis – lice
Pertussis – Bordatella pertussis
Plague (Class A) – Y. pestis
Rabies
RSV (pediatric/geriatric)
Rubella
SARS
Scabies – Sarcoptes scabei
TB – M. tuberculosis
Typhoid Fever (Salmonella
typhi)
Typhus Fever - Rickettsia
West Nile Virus
Yellow Fever - Flavivirus
A 27 yo man is admitted with symptoms suggestive of
meningitis. The patient has a history of head trauma
from MVA. The lab calls to report that a g+c is noted
on the gram stain. What is your next action?
a. Have the charge nurse compile a list of exposed staff.
b. Notify EH that several employees will need
prophylaxis
c. Tell the staff that no one should be treated until the
culture report is final
d. Ensure that staff understand which organisms are
treated and which are not.
A gram negative bacterium responsible for
chronic antral disease and a major factor in
peptic ulcer disease is:
a.
b.
c.
d.
H. pyogenes
S. typhi
C. difficile
H. pylori
An example of an obligate intracellular parasitic
bacterium would an organism responsible for:
1.
2.
3.
4.
Hepatitis
Q Fever
Malaria
Epidemic typhus
a.
b.
c.
d.
2, 3
2, 4
3, 4
1, 2
1.
2.
3.
4.
You are notified by the lab that 3 patients on the oncology
ward have cultures (2-BAL, 1-sinus) positive for Aspergillus
fumigatus and chart review indicates invasive disease. All
3 cultures were taken on the same day. Your FIRST course
of action is:
Notify the head nurse and medical director of the unit.
Set up a meeting with engineering to discuss the air
handling system.
Ask micro to do a retrospective review of Aspergillus
cultures.
Notify administration of the outbreak.
a. 1, 3
b. 1, 2
c. 3, 4
d. 1, 4
Review of micro logs revealed 4 more +Aspergillus
cultures in the last 6 months. Chart review
indicate the patients were from different units and
were community-associated colonization. Based
on this, you:
a. Decide no follow-up is necessary since oncology
patients are high-risk for Aspergillus.
b. Look for a common factor in all 7 patients.
c. Look for a common factor among the 3 oncology
patients only.
d. Continue investigating all 7 patients via phone
interview.
1.
2.
3.
4.
While touring the oncology unit and outside perimeter of
the hospital, you observe road construction one block
form the hospital. (The oncology is a street level, facing
the construction.) You decide this could be the source of
the Aspergillus. Possible factors include:
Staff props the outside doors open when they go outside.
Pigeons roost on the unit’s windowsill.
The air intake system on the roof faces the construction.
The unit’s utility room has an open window.
a. 1, 3
b. 2, 4
c. 1, 4
d. None, construction is too
far away.
A meeting was called with the head nurse, medical
director, and vice president of engineering. Proposed
interventions included adding an alarm to sound when
the outside door was open longer than 30 sec., placing
a positive airflow vent over the door way, and locking
the utility room window. To determine whether these
measures were effective, you will:
1. Monitor every patient on the unit for the next 6 mo.
2. Have the micro lab notify you immediately in the
event of another + culture.
3. Tour the unit daily to ensure the engineering controls
are in place.
4. Consider the problem solved and move on.
60
A patient has a perirectal swab positive for VRE.
This is an example of:
a.
b.
c.
d.
Normal flora
Colonization
Asymptomatic infection
Symptomatic infection
Of the following viruses, which is the most
common healthcare-associated pathogen in
pediatric wards?
a.
b.
c.
d.
Respiratory syncytial virus (RSV)
Adenovirus
Herpes simplex virus
Cytomegalovirus
A 10 - yo boy is admitted to the hospital with a
3 day history of fever, abdominal pain, diarrhea,
and vomiting. He and his family have just
returned from a week long camping trip in the
mountains that included trips to the seashore.
The next 4 questions refer to this scenario.
A stool culture is reported with many lactose
negative colonies. The most probable causing
organism is:
a.
b.
c.
d.
Providencia alcalificiens
Providencia stuartii
Yersinia enterocolitica
Providencia rettgeri
Which of the following organisms can grow in
the small bowel and cause diarrhea in children
and traveler’s diarrhea through the production
of enterotoxins?
a.
b.
c.
d.
Yersinia enterocolitica
Escherichia coli
Salmonella typhi
Shigella dysenteriae
Which disease requires a very small inoculum of
organisms to cause disease?
a.
b.
c.
d.
Dysentery (Shigella)
Salmonella
Campylobacter
Giardia
Which organism found in food poisoning causes
the most rapid onset of symptoms?
a.
b.
c.
d.
Salmonella enteritidis
Shigella sonnei
Staphylococcus aureus
Escherichia coli
A 14 uo boy form rural Maryland was seen in
the ED with fever, fatigue, chills, headache and a
large annular lesion on his left thigh which the
patient described as burning and itching. What
is the most probable vector of this child’s
illness?
a.
b.
c.
d.
Tick
Mosquito
Flea
Louse
You receive a call from a young man who thinks
he was exposed to HIV. His baseline HIV test
(ELISA) was negative. At what time period after
the exposure would we be most likely to detect
HIV antibodies?
a. 6 months
b. 1-3 months
c. 12 months
d. 3 weeks
A preadmission serum sample and a current
sample from a patient is used for antibody
testing for HSV. ELISA is performed on paired
sera with the following titers: previous = 1:8,
current = 1:128. The results indicate:
a.
b.
c.
d.
Acute HSV infection
Indeterminate infection
Chronic infection
Immunity to HSV
70
A single serum sample is sent for ELISA antibody
testing. The following titers are reported:
HSV titer = 1:128, CMV = <1:8, EBV = <1:8.
These results indicate:
a.
b.
c.
d.
Immunity the HSV
Confirmation of acute HSV infection
Presumptive identification of HSV infection
Immunity to CMS and EBV
An emaciated homeless person is admitted with
suspicion of TB. He had an upper lobe cavitary
lesion and a +PPD of 10 mm. He is placed in
Airborne precautions in negative pressure. The
lab indicates 3 +AFB smears. This indicates:
a.
b.
c.
d.
Confirmed diagnosis of TB
Presumptive mycobacterial infection
Presumptive diagnosis of TB
No conclusion is possible from this information.

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