Identification of Infectious Disease Processes

Ready…Set…Go!Carolyn Fiutem, MT(ASCP), CIC

Infection Prevention Officer, TriHealthOctober 10, 2012

Objectives:

Recognize epidemiologically significant organismsInterpret results of lab testsIdentify indications for biologic monitoring

Fundamental Principles of Infection and Immunity

Colonization – organisms in or on a host; growth but no tissue invasion or damageInfection – entry of an infectious agent in tissues of a host; growth and create symptomsContamination – presence of microorganisms on inanimate objects, skin, or in substances

INFECTIOUS AGENT /Causative AgentA 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.

RESERVOIRA place within which microorganisms can thrive and reproduce.

PORTAL OF EXITA place of exit providing a way for a microorganism to leave the reservoir.

MODE OF TRANSMISSIONMethod of transfer by which the organism moves or is carried from one place to another.

PORTAL OF ENTRYAn opening allowing the microorganism to enter the host.

SUSCEPTIBLE HOSTA 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.

Components of the Infectious Disease Process

Mechanisms of Microbe PathogenicityVirulence

Environmental survival in transitBBP in blood outside the body, Protection against drying, Vectors

Effective mechanism for transmission

Vectors, Motility, Airborne, Fomites

Ability to attachElectrostatic charge, Adhesion

Reproduction/ProliferationEnzymes, Endotoxins, Capsules, Biofilms

Invasion and DisseminationRigid cell wall, Cell surface components, ability to alter cell surface, Deterrents to intracellular killing after phagocytosis

Bacterial ToxinsExotoxins – potent toxin secreted by a bacterial cell

Excreted in environmentGram-positive bacteriaMore susceptible to heatNeutralized by antibodiesEnzymatic activityPVL of MRSA, and Toxins A/B of C. diff

Endotoxin – heat-stable toxin in cell wall; pyrogenic; increase capillary permeability

Surface of GNRsPartially neutralized by antibodiesProduce physiologic changes in hostCholera toxin – fluid in the GI tractE. coli 0157

Cellular ImmunityT-lymphocytes & mononuclear phagocytesOriginate in bone marrowMigrate to thymus fetus/infancyT-cells from spleen, lymph nodes, bone marrowReceptors on surface of T-lymphocytesReview cellular immune response

Cellular Immunity cont.Cytokines

Interleukin – 1: pyrogen, stimulate macrophage chemotaxisInterleukin – 2: made by CD4, enhance NK cell activityInterleukin – 4: made by T-cells and mast cells, stimulate growthInterleukin – 6: pyrogen, B-cell/T-cell differentiationInterferon: made by WBCs & fibroblasts; inhibit virus growth; α, β, γTumor Necrosis Factorcause protein catabolism in host w/ loss of muscle massLymphotoxin: promotes inflammation; stimulates neutrophilsGranulocyte and Monocyte Stimulating Factors - reproduction

T-lymphocytesCD3 surface marker – IDs themCD4 marker – helper lymphocytes for phagocytosis, release cytokines, long-term memory (vaccines)CD8 cells – cytotoxic and suppressor lymphocytesNatural killer cells – lyse tumor & virus infected cells

Humoral Immunity – B-lymphocytesCellular Sources of

AntibodiesPrecursors from fetal liver

and bone marrow to spleen and lymph nodes

Antibody producing plasma cells

Classes of ImmunoglobulinIgG – 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 membranesIgD – surface of lymphocytes – antigen specificityIgE – allergy inducing; histamine & inflammatory substances; mucous membranes

Non-specific Host Defenses

Genetic ConstitutionCaucasians, African-Americans, Asians, Alaskan/Hawaiian natives

Mechanical BarriersSkin, mucous membranes, normal flora

Physiological BarriersFever, secretions, motility

Vascular Circulating DefensesNatural/cross-reactive antibodies, fibronectin, estrogens, circulating WBCs

•Activated by contact with IgG or IgM or certain microorganisms•Genetic deficiencies 10

Phagocytic Cell SystemNeutrophils (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 RatiosDegenerative 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 CountsRelative Number = percentageAbsolute Count = Percentage X Total WBC Ct.Can have normal WBC count yet be neutropenicNeed to look at WBC count and differentialNormal WBC ranges:

1. Adults ~ 3.5-10, 0002. Newborns ~ 9-30,0003. 2 weeks ~ 5-20,0004. 1 yr ~ 6-18,0005. 4 yr ~ 5500-17,0006. 10 yr ~ 4500 – 13,500

Basophils0-1% of WBCsMast Cells are tissue basophilsSecrete histamine, seratonin, & prostaglandins – increase blood flow to areaHodgkin’s DiseaseParasitic infectionsInflammationAllergySinusitisAfter splenectomyTBSmallpox, ChickenpoxInfluenza

Eosinophils

1-4% of WBCsAre cytotoxicNAACP….NeoplasmAsthma/AllergyAddison’s DiseaseCollagen/Vascular DiseaseParasitic Infections

Lymphocytes

25-40% of WBCsFight viral infectionsPertussisChronic granulomatous diseases, i.e., TBCrohn’s diseaseUlcerative ColitisAddison’s DiseaseBrucellosis

Lymphopenia

ChemotherapyAfter administration of cortisoneObstruction of lymphatic drainage, Whipple’s disease or tumorsHodgkin’s diseaseHIV/AIDSTrauma

Monocytes

Fight severe infection via phagocytosis3-7% of WBCsBacterial infectionsTBSBESyphilisParasitic, fungal, rickettsial diseases

20

Knowledge Check…

Which of the following is not a mechanical barrier?

a. Intact skinb. Mucous membranesc. Secretionsd. 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 wallb. Biofilmc. Sludged. 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 typhi2. Bacteroides fragilis3. Listeria monocytogenes4. Staphylococcus aureus

a. 2,3b. 1,3c. 1,2d. 3,4

Knowledge Check…

Which organism found in food poisoning causes the most rapid onset of symptoms?

a. Salmonella enteritidisb. Shigella sonneic. Staphylococcus aureusd. 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. Monocyteb. Eosinophilc. Neutrophild. Lymphocyte

Knowledge Check…Your patient has a low absolute neutrophil count. Of the following choices, which is true of your patient?

1. They are especially susceptible to disease.2. You can determine the absolute neutrophil count by

multiplying the total WBC count by the percentage of mature and immature neutrophils.

3. The patient’s WBC count is between 4000 & 10,000.4. The patient’s complement system will only be

activated through the alternate pathwaya. 1b. 1 & 2c. 3d. 1, 2, & 4

Microbiology and the LaboratoryBacteria

Internal structures – familiarityExternal structures – cell wall, glycocalyx, flagella, fimbriae and piliSize/Shape – 0.2-2 u X 2-8 u; cocci, rods, spiralsReplication – cell division every 15-24 hoursGenetic variation

Plasmids found in cytoplasm, circular pieces of DNATransformation – free DNA in cellTransduction – DNA carried by bacteriophage (virus)Conjugation – direct sharing of DNA

Mutations – random base pair substitutionSubmicroscopic bacteria – Mycoplasma, Chlamydiae, Rickettsiae

Fungi

YeastsSingle-celled, budding or fission2-60 uSmooth, creamy coloniesCandida, Cryptococcus

MoldsMultinucleated network of filaments (hyphae)Can reproduce asexually or sexuallyCan reproduce via sporesAspergillus, Rhizopus

Dimorphic fungiGrow as yeast or fungi depending on conditionsMold form at room temp (25°C)Yeast form at body temp (37°C)Histoplasma, Coccidioides, Blastomyces, Paracoccidioides

Viruses, Parasites, PrionsViruses

Replicate only in cells of host/reservoirRNA or DNA in a protein coatClassified using genome, number of strands and presence or absence of envelope

ParasitesBlood - PlasmodiumProtozoa - GiardiaHelminths – pinwormEctoparasites – scabies, lice, bedbugs

PrionsInfectious pieces of proteinsOnly replicate in cells of living organismsNeurotropic Untreatable and universally fatalCreutzfeld- Jakob disease (CJD, vCJD) – transmissible spongiform encephalopathy (TSE) 30

Laboratory TechniquesMicroscopy – light & electronSpecimen Preparation – direct/wet prep, stainsCulture – agar, broth, biphasic, tissueAntimicrobial Susceptibility Testing (AST)Enzyme Immunoassay (EIA)Latex AgglutinationDNA ProbesPolymerase Chain Reaction (PCR)SerologicAnatomic PathologyGeneral Laboratory

Identification of…Bacteria – stains, culture, serology, molecularFungi: yeasts, molds – direct preps, culture, biochemical tests, direct antigen tests, serologyViruses – direct antigen tests, antibody tests, tissue cultureParasites – microscopy, serologyMycobacteria – culture, molecular, direct detection Mycoplasma - serologyChlamydiae – direct antigen testsRickettsiae/Other Tick-borne Microbes – serology, ELISA

Antimicrobial Susceptibility TestsDisk Diffusion – Kirby BauerBroth Dilution – Minimum Inhibitory Concentration (MIC); manual or automatedE-TestBeta-lactamase – penicillins resistanceDisk Approximation – inducible clindamycin resistanceSynergy Test – combinations of antibioticsHodge Test – Extended Spectrum Beta-lactamase in gnrsMinimal Bacteriocidal Concentration (MBC)

Types of ß – lactamases

produced by Enterobacter-

iaceae

Examples Hydrolyzes Inhib by CA

BasicPens

Cephalosporins Cepha-mycins

(FOX, CTE)

Carba-penems

(IMI, MERO)

AZT

I II III IV

Broad Spectrum TEM-1TEM-2SHV-1

Y Y Y/N N N N N N +/+++

Extended Spectrum Beta-

Lactamase

TEM familySHV family

Y Y Y Y Y N N Y ++++

Amp-C ACCCMYCFEDHA

Y Y Y Y Y Y N Y N

Carbapen-Emases(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 +

Gram Negative Beta-lactamases

Courtesy of Dr. Larry Gray

Measures to control resistant organisms

Antibiotic StewardshipSurveillanceAntibiogramsAppropriate use of vaccinesAppropriate transmission-based precautionsHand HygieneBarriers

Antimicrobial Therapy - Susceptibility ReportsTherapy/TreatmentProphylactic TherapyEmpiric Therapy

Susceptible (S)Intermediate (I)Resistant (R)

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

Staphylococcus aureus

Spectrum of Coverage…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*TetracyclinesChloramphenicol (causes aplastic anemia so rarely used)Other: Linezolid, Synercid (VRE)

Gram negative coverage:Broad spectrum penicillins (Ticarcillin-clavulanate, piperacillin-tazobactam)*Cephalosporins (2nd, 3rd, and 4th generation)*Aminoglycosides (Gentamicin; nephrotoxic)*Macrolides (Azithromycin)*Quinolones (Ciprofloxacin)*Monobactams (Azetreonam)*Sulfonamide/trimethoprim*Carbapenems (Imipenem)ChloramphenicolPseudomonas coverage:Ciprofloxacin*Aminoglycosides*Some 3rd generation cephalosporins4th generation cephalosporinsBroad spectrum penicillins*Carbapenem

Spectrum of Coverage…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)CarbapenemsChloramphenicol

Antifungal spectrum of activity against common fungi.

Ashley E S D et al. Clin Infect Dis. 2006;43:S28-S39© 2006 by the Infectious Diseases Society of America

Factors that affect outcome in AST…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 antimicrobialsProblems with administration – timeliness, storage, deterioration, patient compliance, absorption failureRenal/Liver Failure

40

Specimen Collection: Garbage In = Garbage Out!

Specimen quality is keyNeed 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 necessaryUse preservatives when applicableTissues/Body fluids, Anaerobic cultures, CSF – stat specimensLabel all specimens at the bedside/where collected with 2 patient identifiers and pertinent specimen information (D/T coll, source/site, abx, who coll)

Cerebrospinal Fluid InterpretationCSF should be clear & colorlessGlucose 40-70 mg/dlProtein 15-45 mg/dlCSF Glucose = ~2/3 serum glucoseBacterial Meningitis:

1. WBC = increased2. Diff – neutrophils3. Protein = marked

increase4. Glucose =markedly

decreased

Viral (Aseptic) Meningitis:1. WBC = increased2. Diff – lymphs3. Protein = moderate

increase4. Glucose = Normal

TB/Fungal Meningitis:1. WBC = increased2. Diff – Lymphs and Monos3. Protein = moderate to

marked increase4. Glucose = Normal to

decreased

Knowledge Check…

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 polysc. > 10 epithelial cells/lpf and many Pseudomonas

in cultured. Many WBCs and organisms on low power field

Knowledge Check…

To increase recovery of AFB from expectorated or induced sputum, specimens should be collected:

a. Once a week for 3 consecutive weeksb. Every day for 1 weekc. First morning specimen for 3 consecutive daysd. Three specimens 1 hour apart on the same day

Knowledge Check…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.

1. Differential2. Enrichment3. Selective4. Nutrient broth5. Synthetic sheep blood agar

a. 1, 3 c. 3, 4b. 2, 3 d. 5, 1

Knowledge Check…

Gram stains classify an organism as gram-positive or gram-negative. The determinant factors for Gram stains are cell wall component of:

a. Peptidoglycansb. Lipidsc. Polysaccharidesd. Mycolic acids

Knowledge Check…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.

Knowledge Check…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. Carbenicillinb. Oxacillinc. Gentamicind. Amikacin

Knowledge Check…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. Minimum inhibitory concentration (MIC)b. Kirby-Bauer disk diffusionc. Minimum bacteriocidal concentrationd. Serum-cidal levels

Microbiological Environmental Sampling

Not recommendedCostlyRequires special proceduresNo standards for comparisonMay have adverse intervention implementedWhen investigation suggests a source or reservoirUse quantitative methods

Routine monitoringBiological monitoring of sterilization processesMonth culture colony counts and endotoxin testing of water and dialysate in HDUsShort term evaluations of interventions implemented as anew process or to stop an outbreak

50

Microbial PathogenesisNormal Flora – commonly found on healthy human body surfaces (endogenous source)Colonization – microorganisms in the absence of symptoms or deep tissue invasionAsymptomatic Infection – viable organisms without causing any obvious symptoms (latent TB)Opportunistic Infections – cause disease primarily in immunodeficient hostsPathogenic Organisms – causes tissue damageInfection – invasion by and multiplication of organisms causing tissue damage and disease

Epidemiologically Significant Pathogens

Etiology (Organism)Pathogenesis (Life cycle understanding)Identification (S/S)Diagnostic TestingIncubation PeriodTransmission-based PrecautionsTreatmentCase Fatality

Selected Infectious DiseasesAnthrax (Class A)Aspergillosis: environmentalChicken pox/Herpes zosterConjunctivitisCryptosporidiosisDengue – Flaviviruses 1, 2, 3, 4Foodborne DiseasesHanta virusHepatitis – A, B, C, D, EHIVInfluenza LegionellosisMeaslesMeningitis – bacterial vs viral

MumpsPediculosis/Phthiriasis – licePertussis – Bordatella pertussisPlague (Class A) – Y. pestisRabiesRSV (pediatric/geriatric)RubellaSARSScabies – Sarcoptes scabeiTB – M. tuberculosisTyphoid Fever (Salmonella typhi)Typhus Fever - RickettsiaWest Nile VirusYellow Fever - Flavivirus

Knowledge Check…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

prophylaxisc. Tell the staff that no one should be treated until the

culture report is finald. Ensure that staff understand which organisms are

treated and which are not.

Knowledge Check…

A gram negative bacterium responsible for chronic antral disease and a major factor in peptic ulcer disease is:

a. H. pyogenesb. S. typhic. C. difficiled. H. pylori

Knowledge Check…

An example of an obligate intracellular parasitic bacterium would an organism responsible for:

1. Hepatitis a. 2, 32. Q Fever b. 2, 43. Malaria c. 3, 44. Epidemic typhus d. 1, 2

Knowledge Check…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:

1. Notify the head nurse and medical director of the unit.2. Set up a meeting with engineering to discuss the air

handling system.3. Ask micro to do a retrospective review of Aspergillus

cultures.4. Notify administration of the outbreak.

a. 1, 3 b. 1, 2 c. 3, 4 d. 1, 4

Knowledge Check…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.

Knowledge Check…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:

1. Staff props the outside doors open when they go outside.2. Pigeons roost on the unit’s windowsill.3. The air intake system on the roof faces the construction.4. The unit’s utility room has an open window.

a. 1, 3 c. 1, 4b. 2, 4 d. None, construction is too

far away.

Knowledge Check…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

Knowledge Check…

A patient has a perirectal swab positive for VRE. This is an example of:

a. Normal florab. Colonizationc. Asymptomatic infectiond. Symptomatic infection

Knowledge Check…

Of the following viruses, which is the most common healthcare-associated pathogen in pediatric wards?

a. Respiratory syncytial virus (RSV)b. Adenovirusc. Herpes simplex virusd. Cytomegalovirus

Knowledge Check…

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. Providencia alcalificiensb. Providencia stuartiic. Yersinia enterocoliticad. 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. Yersinia enterocoliticab. Escherichia colic. Salmonella typhid. Shigella dysenteriae

Which disease requires a very small inoculum of organisms to cause disease?

a. Dysentery (Shigella)b. Salmonellac. Campylobacterd. Giardia

Which organism found in food poisoning causes the most rapid onset of symptoms?

a. Salmonella enteritidisb. Shigella sonneic. Staphylococcus aureusd. Escherichia coli

Knowledge Check…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. Tickb. Mosquitoc. Flead. Louse

Knowledge Check…

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

Knowledge Check…

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. Acute HSV infectionb. Indeterminate infectionc. Chronic infectiond. Immunity to HSV

70

Knowledge Check…

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. Immunity the HSVb. Confirmation of acute HSV infectionc. Presumptive identification of HSV infectiond. Immunity to CMS and EBV

Knowledge Check…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. Confirmed diagnosis of TBb. Presumptive mycobacterial infectionc. Presumptive diagnosis of TBd. No conclusion is possible from this information.

Thank you!