Microbiology Flashcards
Asymptomatic bacteriuria: Diagnosis in catheterized urine.
Requires isolation of 10² colony-forming units per mL of the same species.
Only one sample is required.
Asymptomatic bacteriuria: Who needs treatment?
Those who are pregnant or who will undergo urological instrumentation.
UTI pathogen: Most common.
E. coli.
UTI pathogen: Older male with obstructive uropathy.
Enterococcus.
UTI pathogens: Culture-negative (3).
Mycoplasma hominis.
Ureaplasma urealyticum.
Chlamydia trachomatis.
UTI pathogen: Fungal.
Candida spp.
Hemorrhagic cystitis:
A. Pathogen.
B. Clinical background.
A. Adenovirus, esp. types 11 and 21.
B. Bone-marrow transplant.
Sensitivity and specificity of urine-dipstick tests:
A. Leukocyte esterase.
B. Nitrite.
A. SN: 70-95%; SP: 70%.
B. SN: 50%; SP: 95%.
Viral agents of diarrhea:
A. In winter.
B. Foodborne and infective with small inoculum.
A. Rotavirus.
B. Norwalk-like viruses.
Bacterial agents of diarrhea:
A. Traveler’s diarrhea.
B. Hemolytic-uremic syndrome.
A. Enterotoxigenic E. coli.
B. Enterohemorrhagic E. coli (O157:H7).
Enterohemorrhagic E. coli: Toxin.
Shiga toxin.
Salmonella bacteremia: Who is at risk (2)?
Those with sickle-cell disease or indwelling prostheses.
Bacterial enteritis: Leading agent in the U.S.
Campylobacter jejuni.
Campylobacter jejuni: Diseases other than enteritis.
Guillain-Barré syndrome.
Reactive arthritis.
Most virulent strain of Clostridium difficile:
A. Name.
B. Basis of virulence.
A. B1/NAP1/027.
B. Mutation in tcdC leads to increased production of toxins A and B.
Clostridium difficile: Reference method of testing for infection.
Cytotoxicity assay.
Clostridium difficile: Genes implicated in pathogenesis.
tcdA: Toxin A.
tcdB: Toxin B.
tcdC: Regulator of the toxins.
Another bacterial agent of antibiotic-associated colitis.
Klebsiella oxytoca.
Entamoeba histolytica: Preferred test.
Enzymatic immunoassay of stool.
Non-microscopic test for neutrophils in stool.
Stool lactoferrin.
Bacterial agents of pneumonia: Community-acquired, single most common.
Streptococcus pneumoniae.
Bacterial agents of pneumonia: In patients with COPD (3).
Haemophilus influenzae.
Moraxella catarrhalis.
Legionella pneumophila.
Bacterial agents of pneumonia: Alcoholics (3).
S. pneumoniae.
K. pneumoniae.
Gram-negative aerobic bacilli.
Bacterial agents of pneumonia: Bird handlers.
Chlamydophila psittaci.
Bacterial agents of pneumonia: Bronchiectasis (3).
Pseudomonas aeruginosa.
Burkholderia cepacia.
Staphylococcus aureus.
Bacterial agents of pneumonia: Atypical pneumonia.
Mycoplasma pneumoniae.
Chlamydophila pneumoniae.
Bacterial agents of pneumonia: Necrotizing (2).
S. aureus.
Ps. aeruginosa.
Bacterial agents of pneumonia: Hospital-acquired, single most common.
S. aureus.
Legionella pneumophila: Environmental associations (3).
Hot tubs.
Cooling towers.
Construction sites (dust).
Legionella pneumophila: Clinical manifestations (5).
High fever.
Hyponatremia.
Renal dysfunction.
Diarrhea.
Neurological abnormalities.
Coronaviruses that cause pneumonia (3).
SARS coronavirus.
NL63.
HKU1.
Human papillomaviruses that cause pneumonia.
K1, WU.
Hantavirus: Animal vector.
The deer mouse.
Hantavirus: Findings on peripheral smear (4).
Thrombocytopenia.
Neutrophilia without toxic granules.
Erythrocytosis.
Immunoblastic lymphocytosis.
Agents of endocarditis: Native valves (most common).
S. aureus.
Agents of endocarditis: Diseased valves, most common.
Streptococci, esp. viridans streptococci.
Agents of endocarditis: Prosthetic valves, very early, most common (3).
S. aureus.
S. epidermidis.
Gram-negative bacilli.
Agents of endocarditis: Prosthetic valves, early, most common (2).
S. epidermidis.
S. aureus.
Agents of endocarditis: Prosthetic valves, late, most common.
Streptococci.
Culture-negative endocarditis: Bacterial causes (5).
Coxiella burnetii.
Bartonella.
Legionella.
Chlamydia.
Tropheryma whippeli.
Culture-negative endocarditis: Noninfectious causes (3).
Libman-Sacks endocarditis.
Marantic endocarditis.
Carcinoid heart syndrome.
Culture-negative endocarditis: A third cause.
Previous antibiotic therapy.
Viral agents of encephalitis: Most common (2).
California encephalitis.
St. Louis encephalitis.
Viral agents of encephalitis: Herpesviridae (2).
HSV1, HHV6.
Amoebic agents of encephalitis (3).
Acanthamoeba spp.
Naegleria fowleri.
Balamuthia mandrillaris.
Agents of aseptic meningitis:
A. Most common.
B. Others (4).
A. Enteroviruses.
B. HSV-2, LCM virus, mumps virus, HIV.
Agents of aseptic meningitis: Seasonal variation.
Summer and fall: Enteroviruses.
Winter and spring: LCM virus.
Bacterial agents of meningitis: Neonates (3).
Group-B streptococci.
Gram-negative bacilli.
Listeria monocytogenes.
Bacterial agents of meningitis: Populations most affected by Listeria monocytogenes.
Neonates.
Elderly.
Immunocompromised.
Iron-overloaded.
Bacterial agents of meningitis: Infants, young children, young adults.
N. meningitidis.
S. pneumoniae.
H. influenzae.
Who is at highest risk of serious infections by N. meningitidis?
Those with a deficiency of C5-C9.
Bacterial agents of meningitis: Adults.
S. pneumoniae.
N. meningitidis.
Bacterial agents of meningitis: Southeast Asia.
Streptococcus suis.
HSV encephalitis: Unique findings in CSF (3).
Very high protein.
Blood.
Low glucose.
Most common agents of infections of prosthetic joints at:
A. Less than 3 months (2).
B. 3-24 months (2).
C. Beyond 24 months.
A. S. aureus, Gram-negative bacilli.
B. S. epidermidis, P. acnes.
C. S. epidermidis.
Infections of prosthetic valves: Cutoffs for leukocyte count and percentage of neutrophils in synovial fluid (2).
A. Knee: 1700/mL, >65% neutrophils.
B. Hip: 4200/mL, >80% neutrophils.
Severe sepsis: Definition.
Sepsis with organ dysfunction.
Septic shock: Definition.
Sepsis with refractory hypotension.
Sepsis vs. the systemic inflammatory-response syndrome: Theoretical difference.
SIRS is sepsis with no infectious source.
Sepsis vs. SIRS: Distinguishing test.
Procalcitonin: Elevated in sepsis.
Indicators of catheter-related sepsis (3).
Culture of catheter tip yields 5 times as many colonies as the blood culture.
Culture of catheter tip becomes positive at least 2 hours before the blood culture.
Cultures of catheter tip and blood yield the same organism.
Neonatal sepsis: Most common agents (2).
E. coli.
Group-B streptococci.
Agents of bacteremia in patients with colon cancer (2).
Streptococcus bovis.
Clostridium septicum.
Agent of fungal meningitis: Most common.
Cryptococcus.
Agent: Erythrasma.
Corynebacterium diphtheriae.
Agent: Juvenile periodontitis.
Aggregatibacter actinomycetemcomitans.
Agent: Glanders.
Burkholderia mallei.
Agent: Meliodosis.
Burkholderia pseudomallei.
Agent: Rocky Mountain spotted fever.
Rickettsia rickettsii.
Agents: Visceral larva migrans.
Toxocara canis, Toxocara cati.
Agent: Erysipelas.
Streptococcus pyogenes.
Agent: Erysipeloid.
Erysipelothrix rhusiopathiae.
Agent: Freshwater cellulitis.
Aeromonas hydrophilia.
Agent: Saltwater cellulitis.
Vibrio vulnificus.
Agent: Lymphogranuloma venereum.
Chlamydia trachomatis.
Agent: Acute epiglottitis.
Haemophylus influenzae.
Agents: Monoarticular arthritis (2).
Staphylococcus aureus.
Streptococci.
Agent: Arthritis in abusers of intravenous drugs.
Pseudomonas aeruginosa.
Agent: Polyarthritis in the sexually active.
Neisseria gonorrhoeae.
Agent: Croup.
Parainfluenza viruses 1-3.
Agents: Otitis media (3).
Streptococcus pneumoniae.
Haemophilus influenzae.
Moraxella catarrhalis.
Agent: Carrión’s disease.
Bartonella bacilliformis.
Agent: Verruga peruana.
Bartonella bacilliformis.
Agent: Uterine infection following septic abortion.
Clostridium perfringens.
Agent: Rat-bite fever.
Streptobacillus moniliformis.
Agent: Black piedra.
Piedraia hortae.
Agent: White piedra.
Trichosporon beigelii.
Agent: Tinea versicolor.
Malessezia furfur.
Agent: Tinea nigra.
Hortaea werneckii.
Agents: Chromoblastomycosis (3).
Phialophora verrucosa.
Cladophialophora spp.
Fonsecaea pedrosoi.
Agent: Lobomycosis.
Lacazia loboi.
Agents: Phaeohyphomycosis (3).
Phialophora verrucosa.
Exophiala jeanselmi.
Alterneria spp.
Agents: Eumyotic mycetoma (3).
Exophiala jeanselmi.
Madurella spp.
Pseudallescheria boydii.
Agents: Actinomycotic mycetoma (3).
Actinomyces spp.
Nocardia spp.
Streptomyces.
Agent: Rhinosporidiosis.
Rhinosporidium seeberi.
Agent: Rhinoscleroma.
Klebsiella rhinoscleromatis.
Agent: Roseola infantum (exanthem subitum).
HHV6.
Agent: Fifth disease.
Parvovirus B19.
Agent: African sleeping sickness.
Trypanosoma brucei.
Agent: Adiaspiromycosis.
Emmonsia parva.
Agent: Fungal otitis media.
Aspergillus niger.
Agent: Hand-foot-mouth disease.
Coxsackie A virus.
Agent: Viral myocarditis.
Coxsackie B virus.
Agent: Dog heartworm.
Dirofilaria immitis.
Agent: Tickborne encephalitis.
Tickborne-encephalitis virus.
Agent: Murine typhus.
Rickettsia typhi.
Agent: Epidemic typhus.
Rickettsia prowazekii.
Agent: Rickettsialpox.
Rickettsia akari.
Agent: Relapsing fever.
Borrelia recurrentis.
Agent: Trench fever.
Bartonella quintana.
Vector: Dog heartworm.
Anopheles spp.
Vectors: Lymphatic filariasis (2).
Anopheles spp.
Culex spp.
Vector: Yellow fever.
Aedes spp.
Vectors: Lyme disease (3).
Eastern U.S.: Ixodes scapularis.
Western U.S.: I. pacificus.
Europe: I. ricinus.
Vector: Babesia.
Ixodes spp.
Vector: Anaplasmosis.
Ixodes spp.
Diseases of which Amblyomma americanum is the vector (3).
Ehrichliosis.
Tularemia.
Southern tick-associated illness.
Dermacentor spp.: Diseases of which it is a vector (3).
Rocky Mountain spotted fever.
Tularemia.
Colorado tick fever.
Vector: Trachoma.
Musca sorbens.
Vector: Onchocercosis.
Simulium spp.
Vector: Rickettsialpox.
Mite.
Viral cytopathic effect: Tear-shaped cells.
Enteroviruses.
Viral cytopathic effect: Focal plaques in human diploid fibroblasts.
CMV.
Viral cytopathic effect: Grapelike clusters.
Adenoviruses.
Viral cytopathic effect: Syncytia.
Respiratory syncytial virus.
Viral cytopathic effect: Sweeping, with globular cells.
HSV-1, HSV-2.
Viral cytopathic effect: Minimal or none.
Influenza viruses.
Parainfluenza viruses.
Adenovirus infection: Histology.
Smudgy intranuclear inclusion.
CMV infection: Location of inclusions.
Nuclear and cytoplasmic.
Measles infection: Location of inclusions.
Cytoplasmic and nuclear.
RSV infection: Location of inclusions.
Cytoplasmic only.
DNA viruses: Those with envelopes.
Herpesviridae.
Hepadnaviridae.
Poxviridae.
DNA viruses: Those with single-stranded DNA.
Parvoviridae.
Bocavirus.
DNA viruses: Those with circular DNA.
Papillomaviridae.
Polyomaviridae.
DNA viruses: Families.
Adenoviridae. Bocavirus. Herpesviridae. Hepadnaviridae. Poxviridae. Parvoviridae. Papillomaviridae. Polyomaviridae.
RNA viruses: Helical.
Paramyxoviridae. Orthomyxoviridae. Rhabdoviridae. Bunyaviridae. Filoviridae. Deltavirus. Coronaviridae. Arenaviridae.
RNA viruses: Those with negative-sense RNA.
Paramyxoviridae. Orthomyxoviridae. Rhabdoviridae. Bunyaviridae. Filoviridae. Deltavirus. Arenaviridae.
RNA viruses: Which have double-stranded RNA?
Reoviridae.
RNA viruses: Which have circular RNA?
Bunyaviridae.
Arenaviridae.
Deltaviridae.
RNA viruses: Which have no envelope?
Astroviridae.
Picornaviridae.
Reoviridae.
Caliciviridae.
Herpes encephalitis: Classic gross finding.
Hemorrhagic necrosis of the anterior pole of both temporal lobes.
Neonatal herpes: Feared complications (3).
Encephalitis.
Chorioretinitis.
Sepsis.
HSV infection: Definitive method of diagnosis.
Cell culture.
Varicella: Risk factors for serious disseminated infection in adults (2).
Pregnancy.
Immunocompromise.
Varicella, congenital: Diagnosis (3).
Maternal history of infection, or
Characteristic skin lesions on neonate, or
Serological evidence of infection in neonate.
Varicella, congenital: Period of highest risk of transplacental infection.
During the third trimester.
Varicella: Reactivation syndromes.
Herpes zoster.
Ramsey Hunt syndrome.
Varicella: Time to cytopathic effect in culture.
About 2 weeks.
Varicella: Other diagnostic methods (3).
Serology (present of IgM or a 4-fold rise in IgG).
PCR.
DFA of skin scrapings.
Congenital CMV infection: Clinical manifestations (10).
Low birthweight.
Microcephaly.
Intracerebral calcifications.
Chorioretinitis.
Hepatosplenomegaly. Jaundice. Thrombocytopenia. Petechiae. Purpura.
Sensorineural hearing loss.
CMV colitis: Clinical presentation.
Can mimic exacerbation of idiopathic inflammatory bowel disease.
CMV infection: Antigen used in DFA.
pp65.
EBV: Associated neoplasms (7).
Burkitt's lymphoma. Hodgkin's lymphoma. Primary effusion lymphoma. Post-transplant lymphoproliferative disorder. Lymphomatoid granulomatosis. Oral hairy leukoplakia. Nasopharyngeal carcinoma.
EBV:
A. Cell that it infects.
B. Cell that proliferates in response to infection.
A. The B cell.
B. The CD8-positive T cell.
Duncan’s disease: Definition.
X-linked immunoproliferative disorder with predisposition to fulminant infection by EBV.
Duncan’s disease: Typical mechanism of death.
Hepatic necrosis.
Duncan’s disease: Abnormal gene.
SH2D1A, which encodes a subunit of the SLAP-associated protein.
Duncan’s disease: Immunological defect resulting from the abnormal gene.
Uncontrolled activation of T/NK cells during infection by EBV.
EBV serology: The basic tests (5).
Monospot.
IgM anti-VCA.
IgG anti-VCA.
IgG anti-EA.
Anti-EBNA.
EBV serology: Pattern in one who has never been infected.
All results are negative.
EBV serology: Early acute infection.
Positive: IgM and IgG anti-VCA.
Negative: IgG-anti-EA.
Monospot may be positive.
EBV serology: Acute infection.
Positive: IgM and IgG anti-VCA, anti-EA, Monospot.
Anti-EBNA may also be positive.
EBV serology: Convalescence.
Positive: IgG anti-VCA, anti-EA, anti-EBNA.
Negative: IgM anti-VCA, Monospot.
EBV serology: Remote infection.
Positive: Anti-EA, anti-EBNA.
Negative: IgM anti-VCA, Monospot.
IgG anti-VCA may be undetectable.
Monospot: How it works.
EBV induces heterophile antibodies that react with horse erythrocytes in the presence of guinea-pig kidney but not in the presence of bovine-erythrocyte stroma.
Monospot: Relevance of sensitivity to patient’s age.
Less sensitive in patients under age 4.
EBV: Antigen used in immunochemistry.
LMP1.
HHV6:
A. Disease.
B. Cell of latency.
A. Roseola infantum (exanthem subitum).
B. T cells.
HHV7:
A. Disease.
B. Cell of latency.
A. Roseola infantum.
B. Lymphocyte.
HHV8: Associated neoplasms (3).
Multicentric Castleman’s disease.
Primary effusion lymphoma.
Kaposi’s sarcoma.
HHV8: Antigen used in immunochemistry.
LANA1.
Types of adenovirus that cause
A. Respiratory infections.
B. Hemorrhagic cystitis.
C. Gastroenteritis in children.
A. 1-14 and 21.
B. 11 and 21.
C. 40 and 41.
Parvovirus B19: Histology.
Smudgy nuclear inclusions.
Bocavirus:
A. Definition.
B. How detected.
A. A respiratory virus.
B. By PCR only.
JC and BK viruses:
A. When acquired.
B. Clinical presentation of acute infection.
A. In childhood.
B. Asymptomatic.
Reactivation of JC virus:
A. Disease.
B. Affected cell.
C. Histology.
A. Progressive multifocal leukoencephalopathy.
B. Oligodendroglia.
C. Smudgy nuclear inclusions.
Reactivation of BK virus: Diseases (2).
Hemorrhagic cystitis.
Polyomaviral nephropathy.
Merkel-cell polyomavirus: Associated diseases (2).
Merkel-cell carcinoma.
CLL.
HPV types: Plantar wart.
1, 2.
HPV types: Common wart.
2, 1, 4.
HPV types: Plane wart.
3, 10.
HPV types: Oral focal epithelial hyperplasia.
13, 32.
HPV types: Epidermodysplasia verruciformis.
2, 3, 10, 5, 8.
Epidermodysplasia verruciformis:
A. Inheritance.
B. Time of expression.
C. Significance.
A. Autosomal recessive.
B. In the first decade.
C. May progress to SCC.
HPV types: Condyloma acuminatum.
6, 11.
HPV types: LSIL.
6, 11.
HPV types: HSIL (7).
16, 18, 31, 33, 35, 39, 45, others.
HPV types: Cervical adenocarcinoma.
16, 18.
HPV types: Bowenoid papulosis.
16, 18.
Recurrent respiratory papillomatosis: Types (2) and how they are acquired.
Adult: Sexual contact.
Juvenile: Passage through the birth canal.
Agents of bioterrorism: CDC category A (6).
Smallpox.
Hemorrhagic-fever viruses.
Bacillus anthracis.
Yersinia pestis.
Clostridium botulinum.
Francisella tularensis.
Hepatitis A: Incubation.
15-30 days.
The presence of HBsAg can mean what?
Acute hepatitis B.
Chronic carrier state.
Presence of HBeAg indicates what?
Active viral replication.
Presence of anti-HBc indicates what?
Exposure to HBV at some point in life.
Presence of anti-HBe means what?
Chronic carrier state without active viral replication.
Early serologic markers of HBV infection:
A. Order of appearance.
B. Relevance to clinical manifestations.
A. HBsAg, HBeAg, anti-HBc.
B. Emergence of antibodies coincides with appearance of symptoms.
Chronic hepatitis B: Definition.
Persistence of HBsAg for >6 months.
Population at greatest risk for chronic hepatitis B.
Neonatals infected transplacentally.
Rheumatological disease associated with chronic hepatitis B.
Polyarteritis nodosa.
When does HBV DNA become detectable in the serum?
Before HBsAg.
Chronic hepatitis B without detectable HBeAg:
A. Clinical significance.
B. Cause.
A. Can progress to fulminant hepatic failure.
B. Stop codon in C region or pre-C region of genome of HBV.
Replicative hepatitis B: Definition.
Presence of >10⁵ copies of HBV DNA per mL.
Expected serology: Resolved hepatitis B.
Anti-HBs.
Anti-HBc.
Expected serology: Immunization against HBV.
Anti-HBs only.
Expected serology: Acute hepatitis B.
HBsAg, IgM anti-HBc.
Expected serology: Chronic hepatitis B.
HBsAg, anti-HBc.
Hepatitis C: How many patients develop a chronic infection?
About 60%.
Hepatitis C: How many patients with chronic infection develop cirrhosis?
About 15%.
Hepatitis C: Extrahepatic manifestations.
Cryoglobulinemia with its attendant complications, e.g. anemia, glomerulonephritis.
Hepatitis C: Expected test results in a very early infection.
HCV RNA only.
Hepatitis C: Expected test results in acute infection.
HCV RNA.
Enzymatic immunoassay for anti-HCV.
RIBA.
Hepatitis C: Expected test results in chronic infection.
HCV RNA.
Enzymatic immunoassay for anti-HCV.
RIBA.
Hepatitis C: Expected test results in resolved infection.
Enzymatic immunoassay for anti-HCV.
RIBA.
Hepatitis C: What do these results mean?
EIA for anti-HCV: Positive.
RIBA: Negative.
HCV RNA: Negative.
False-positive result for anti-HCV.
Hepatitis C: Endpoint of antiviral therapy.
When HCV RNA has remained undetectable for >24 months after completion of therapy.
Hepatitis C genotypes:
A. Most common in the United States.
B. Most likely to develop resistance to antiviral therapy.
A. Genotype 1.
B. Genotype 1a.
Hepatitis E: Approximate mortality in pregnant women.
30%.
“Non-hepatitis” viruses that can cause hepatitis (6).
HSV1, HSV2.
VZV.
EBV.
CMV.
Yellow-fever virus.
Influenza A: Mechanism of antigenic drift bzw. antigenic shift.
Drift: Point mutations in genes for hemagglutinin or neuraminidase.
Shift: Genetic reassortment between strains.
Hemagglutinin: Role in pathogenesis of influenza.
Binds to sialic-acid-containing receptors on respiratory epithelial cells.
Hemagglutinin: Role in diagnosis.
The expression of hemagglutinin on infected cells is the basis of the hemadsorption test.
Rapid test for influenza:
A. Method.
B. Sensitivity.
C. Specificity.
A. Direct immunofluorescence.
B. 50-80%.
C. Highly specific.
Hemagglutinin inhibition: Uses.
Serologic diagnoses of infection.
Determination of viral subtype and strain.
Parainfluenza virus: How to diagnose infection (3).
PCR.
Immunofluorescence.
Hemadsorption.
Measles virus: Diseases (3).
Measles.
Atypical measles.
Subacute sclerosing panencephalitis.
Measles: Prodrome.
Cough, coryza, conjunctivitis.
Atypical measles: Typical patient.
Teenager who has received only one vaccination.
Subacute sclerosing panencephalitis:
A. Risk.
B. Period of incubation.
A. About 0.001%.
B. About 7 years.
Virus that can cause pancreatitis.
Mumps virus.
Respiratory syncytial virus:
A. Infectivity.
B. Host immunity.
A. Infects nearly all exposed children.
B. Short-lived; recurrent infection is the rule.
Respiratory syncytial virus: Detection (3).
PCR.
Immunofluorescence.
Cell culture.
Human metapneumovirus: Disease.
Lower respiratory infection.
Coxsackie A virus: Diseases.
Hand-foot-mouth disease.
Herpangina.
Coxsackie B virus: Diseases (3).
Myocarditis.
Pericarditis.
Epidemic pleurodynia.
Rhinovirus: Special condition of culture.
Incubation at 32 degrees.
Bunyaviridae: Examples (4).
Bunyavirus.
Hantavirus.
Nairovirus.
Rift Valley fever virus.
Rubella virus: Family.
Togaviridae.
Rubella during pregnancy:
A. When the fetus is most vulnerable.
B. How to prevent it.
A. During the first trimester.
B. Measure titers in women who intend to become pregnant.
Congenital rubella: Affected organs (3).
Ears: Sensorineural deafness.
Eyes: Cataracts, glaucoma, microphthalmia.
Heart: Patent ductus arteriosus.
Yellow fever: Histology (4).
Mid-zonal necrosis.
Microvesicular steatosis.
Apoptotic bodies.
No inflammation.
Flaviviridae: Examples (5).
Yellow-fever virus.
Dengue-fever virus.
St. Louis encephalitis virus.
West Nile virus.
Hepatitis C virus.
West Nile virus: Usual host.
Birds.
Rabies virus:
A. How does it get to the CNS?
B. How does it become transmissible to other animals?
A. Through retrograde fast axonal transport from the site of the bite.
B. It travels along the peripheral nerves to the salivary glands.
Rabies: Diagnostic histologic findings (2) and the location of each.
Negri bodies: Purkinje cells.
Babeș nodules: Microglia.
Rabies: How to diagnose histologically without doing a brain biopsy.
Biopsy of skin, including hair follicles.
Arenaviridae: Origin of name.
Incorporation of the host’s ribosomes imparts a sandy (granular) appearance.
Lymphocytic choriomeningitis virus:
A. Family.
B. Natural hosts.
A. Arenaviridae.
B. Rodents, esp. house mice and hamsters.
HTLV-1:
A. Transmission.
B. Affected cell.
A. Parenteral.
B. CD4-positive T lymphocyte.
HTLV-1:
A. Family.
B. Diagnosis of infection.
A. Retroviridae.
B. Screening ELISA, confirmatory western blot or PCR.
HTLV-1: Late sequelae of infection (2).
Tropical spastic paraparesis.
Adult T-cell leukemia/lymphoma.
Tropical spastic paraparesis: Histology.
Demyelination of the upper thoracic and lower cervical spinal cord.
Adult T-cell leukemia/lymphoma:
A. Lifetime risk.
B. Incubation.
A. About 5% for those infected before age 20.
B. 20-30 years.
Adult T-cell leukemia/lymphoma: Clinical presentation (3).
Jaundice.
Hepatosplenomegaly.
Weight loss.
Adult T-cell leukemia/lymphoma: Other possible clinical features (4).
Rash.
Increased thirst.
Hypercalcemia.
Increased circulating IL-2 receptors.
How long after infection does ___ become detectable?
A. anti-HIV antibody
B. p24 protein
A. 6-8 weeks.
B. 2-3 weeks.
Definition of a positive western blot for HIV.
Presence of band for any 2 of the following:
p24.
gp41.
gp120/160.
A western blot show bands but not in a combination that is considered positive.
A. Interpretation.
B. How to proceed.
A. Indeterminate.
B. If a repeat test at 6 months is indeterminate and there are no risk factors for HIV, then the result is called negative. If there are risk factors, then nucleic-acid testing must be done.
CD4 counts: Guidelines (2).
Measure the CD4 counts at consistent times of day.
Use age-specific reference intervals.
Preferred test for monitoring response to antiretroviral therapy.
HIV RNA.
Proviral DNA:
A. Definition.
B. Application.
A. DNA derived from viral RNA by reverse transcriptase.
B. May be used to confirm infection by HIV.
CD4 count: How often should it be performed?
Every 6 months while the disease is stable.
Viral load vs. CD4 count as predictors of outcomes.
Long term (10 years): Viral load is better.
Short term (6 months): CD4 count is better.
Viral load:
A. How reported.
B. Significant change.
A. As log units (for example, 1000 = 3 log units).
B. 0.5 log units.
Viral load: Relevance to HAART (2).
Viral load determines
- When to start HAART.
- The efficacy of HAART.
Use of HIV RNA to diagnose infection by HIV.
A positive result should be confirmed as soon as possible by ELISA and western blot.
Neonatal infection by HIV: Preferred test.
PCR for proviral DNA, although HIV RNA may be just as good.
Examination of stool for parasites: Number and timing of specimens.
Three specimens, at least 24 hours apart.
Fresh stool: When to examine for parasites.
Within an hour if possible; otherwise, preserve the stool in formalin or alcohol.
Parasites that may be missed by routine stains for ova and parasites (3).
Cryptosporidium.
Cyclospora cayetanensis.
Cystoisospora belli.
How to identify those parasites that may be missed by routine stains (2).
Modified stain for acid-fast bacilli.
Modified saffranin stain.
Culture medium: Free-living amoebae.
Tap-water agar on a bed of E. coli.
Culture medium: Leishmania and Trypanosoma.
Novy-MacNeal-Nicolle medium.
Culture medium: Trichomonas vaginalis.
Diamond’s medium.
Morphologically indistinguishable amoebae.
Entamoeba histolytica.
Entamoeba dispar (albeit without ingested RBCs).
Trophozoite of E. histolytica / E. dispar:
A. Size.
B. Motility.
A. 15-20 μm.
B. Unidirectional.
Trophozoite of E. histolytica / E. dispar:
A. Size and location of karyosome.
B. Distribution of chromatin.
A. Small and central.
B. Fine and even along the nuclear membrane.
Cyst of E. histolytica / E. dispar:
A. Number of nuclei.
B. Chromatoidal bars.
A. Never more than 4.
B. Rounded ends.
Trophozoite of Entamoeba coli.
A. Size.
B. Motility.
A. 20-25 μm.
B. Nondirectional.
Trophozoite of Entamoeba coli:
A. Size and location of karyosome.
B. Distribution of nuclear chromatin.
A. Large and eccentric.
B. Clumped along the nuclear membrane.
Cyst of Entamoeba coli.
A. Number of nuclei.
B. Chromatoidal bars.
A. Up to 8.
B. Frayed ends.
Trophozoite of Entamoeba hartmanni.
A. Size.
B. Motility.
A. 5-10 μm.
B. Nondirectional.
Trophozoite of Entamoeba hartmanni:
A. Size and location of karyosome.
B. Distribution of nuclear chromatin.
A. Small and central.
B. Fine and even along the nuclear membrane.
Cyst of Entamoeba hartmanni:
A. Number of nuclei.
B. Chromatoidal bars.
A. Never more than 4.
B. Rounded ends.
Entamoeba histolytica: A better method than morphology for detection in stool.
Enzymatic immunoassay.
Entamoeba histolytica: Most common location of ulcer.
Cecum.
Non-pathogenic amoebae (2).
Iodamoeba bütschlii.
Endolimax nana.
Endolimax nana: Distinguishing morphologic features (2).
Small size of trophozoite: 5-10 μm.
“Ball-in-socket” karyosome.
Iodamoeba bütschlii: Distinguishing morphologic features (2).
Large vacuole that takes up the iodine stain.
“Ball-in-socket” karyosome.
Pathogenic free-living amoebae: Major genera.
Acanthamoeba.
Naegleria.
Balamuthia.
Naegleria fowleri: Disease.
Primary amoebic meningoencephalitis.
Trophozoite of Naegleria fowleri:
A. Size.
B. Morphology of nucleus and karyosome.
A. 10-35 μm.
B. Small nucleus; large, dense, central karyosome.
Naegleria fowleri: Treatment of CSF specimens that may contain it.
Do not refrigerate.
Acanthamoeba spp. and Balamuthia mandrillaris:
A. Disease.
B. How they enter the body.
A. Granulomatous amoebic encephalitis.
B. Through skin or lungs.
Acanthamoeba spp. and Balamuthia mandrillaris: Histology.
Found around vessels.
Acanthamoeba spp.: Another disease.
Amoebic keratitis.
Trophozoite of Acanthamoeba spp.:
A. Nucleus.
B. Karyosome.
A. Small.
B. Large, central.
Cyst of Acanthamoeba:
A. Number of nuclei.
B. Size of karyosome.
C. Another distinguishing feature.
A. One.
B. Large.
C. Double wall.
Leading cause of protozoal diarrhea.
Giardia intestinalis.
Giardia intestinalis: Motility in wet preparation.
“Falling-leaf” motility.
Cyst of Giardia intestinalis:
A. Shape.
B. Nuclei.
A. Oval.
B. Four, arranged along a central axoneme.
Giardia intestinalis: Preferred method of identification.
Enzymatic immunoassay.
Chilomastix mensili: Disease.
None.
Chilomastix mensili: Differences from G. intestinalis (4).
Rotary motility.
No axoneme.
Lemon-shaped cyst.
Cyst has one nucleus.
Trophozoite of Dientamoeba fragilis: Distinguishing features (4).
Round.
Binucleate.
Each nucleus contains a central, “fractured” karyosome.
Internalized flagellum.
Cyst of Dientamoeba fragilis: Distinguishing feature.
No cyst form has been described.
Dientamoeba fragilis: Diseases (2).
Diarrhea.
Pruritus ani.
Dientamoeba fragilis: Concomitant pathogen.
Enterobius vermicularis.
Trichomonas vaginalis:
A. Number of nuclei.
B. Motility.
A. One.
B. Jerky and nondirectional.
Leishmania spp.:
A. Characteristic organelle.
B. Another genus of protozoans that possess this organelle.
A. Kinetoplast.
B. Trypanosoma.
Leishmania spp.: Genera of vectors (2).
The sandflies
− Phlebotomus.
− Lutzomyia.
Leishmania: Important species (4) and disease caused by each.
L. brasiliensis, L. mexicana: Cutaneous, mucocutaneous.
L. major, L. tropica: Cutaneous, visceral (also affects marrow).
Trypanosomes: Important species (2) and how to distinguish them.
T. cruzi: Large kinetoplast.
T. brucei: Small kinetoplast.
Trypanosomes: How best to find them in the peripheral blood.
Look in the buffy coat.
Chagas’ disease: Most common site of inoculation.
The face.
Romaña’s sign.
Periorbital and palpebral swelling as a sign of inoculation by the reduviid bug.
Trypanosoma brucei: Vector.
Glossina spp.
The one ciliated protozoon known to infect humans.
Balantidium coli.
Balantidium coli: Morphology of trophozoite (4).
Large: 100 μm.
Circumferential cilia.
Rod- or horseshoe-shaped macronucleus.
Micronucleus.
Microsporidia: Important genera (2).
Enterocytozoon.
Encephalitozoon.
Microsporidia: Where to find them on biopsies.
In the apical aspect of enterocytes.
Microsporidia: How to find them in stool samples.
Use a modified trichrome stain.
Cryptosporidium: Important species (2).
Cryptosporidium parvum.
Cryptosporidium hominis.
Cryptosporidium spp.: Where to look for them in a biopsy.
Attached to the brush border of enterocytes.
Cryptosporidium spp.: How to find them on a stool sample.
Use a modified acid-fast stain.
Cyclospora cayetanensis: Where to look for them on a biopsy.
Within the cytoplasm of enterocytes, where different developmental forms of the organism can be seen.
Cystoisospora belli: Distinction from C. cayetanensis (2).
Larger size: 25-30 μm rather than 8-10 μm.
Elliptical rather than circular.
Oocyst of Sarcocystis spp.:
A. Size.
B. Number of nuclei.
A. 15-20 μm.
B. Two.
Sarcocystis spp.: Affected tissues.
Muscle, intestine.
Sarcocystis spp.: Unique property that aids in identification.
Auto-fluorescence in ultraviolet light.
Toxoplasma gondii: Two forms.
Tachyzoite.
Bradyzoite.
Tachyzoite of Toxoplasma gondii: Size and shape.
3-5 μm; bow-shaped (τοξον); large, eccentric nucleus.
Toxoplasma gondii: How acquired (4).
Ingestion of cat feces.
Ingestion of infected meat.
Transfusion of blood; transplantation of tissues.
Transplacental transmission.
Toxoplasma gondii: Interpretation of IgG titers.
Very high or rising: Acute infection.
Low: Resolved infection.
Toxoplasma gondii: Effects on the fetus (2).
Early in gestation: Death.
Late: CNS disease.