Week 3 Block 1: MIHO

Question 1

(1) Normal CD4+ lymphocyte range (2) Most common cause of community-acquired pneumonia in immunocompetent (3) AIDS CD4+ lymphocyte count (4) Likely cause of pneumonia in AIDS patient

Answer 1

(1) 400-1400 cells/uL (2) Streptococcus pneumoniae (3) < 200 cells/uL (4) Pneumocystis jirovecii

Question 2

(1) Dx: Smoker, very high fever, diarrhea, headache, confusion, hyponatremia (2) Gram stain

Answer 2

(1) Legionella pneumophila - Legionnaires’ disease (2) Gram-negative rod often not detected on Gram stain

Question 3

Strongyloides stercoralis: (1) Transmission (2) Diagnosis (3) Complication of infection & mechanism

Answer 3

(1) Skin penetration by filariform (infectious) larva (2) Diagnosed by finding rhabditiform (noninfectious) larvae in stool (3) Hyperinfection syndrome - Rhabditiform larvae can mature into filariform lavae in human GI tract, precipitating an autoinfection cycle that occurs entirely within affected individual… can result in hyperinfection syndrome, characterized by massive dissemination of organism, leading to multiorgan dysfunction and septic shock

Question 4

(1) Toxic component of LPS (2) Mechanism and effects

Answer 4

(1) Lipid A (2) Activation of macs leading to widespread release of IL1 and TNFa, which causes signs and sx of septic shock: fever, hypotension, diarrhea, oliguria, vascular compromise, and DIC

Question 5

Dx/Explain: Diarrhea followed 2 weeks later by progressive difficulty walking over last 2 days with tingling in feet, decreased muscular strength in bilateral lower extremities with absent deep tendon reflexes

Answer 5

Campylobacter jejuni can lead to Guillain-Barre syndrome (GBS) in rare instances. GBS is demyelinating syndrome of peripheral nerves characterized by ascending muscle weakness and paralysis.

Question 6

CMV diseases in: (1) Immunocompetent (2) Immunocompromised

Answer 6

(1) Mononucleosis (Monospot negative), subclinical (2) Severe retinitis, pneumonia, esophagitis, colitis, and/or hepatitis

Question 7

Appropriate prevention measure, given rise of neonatal tetanus incidence in a developing country, & why

Answer 7

Illness caused by Clostridium tetani (tetanus) can be prevented by proper immunization with a childhood series and a booster immunization every 10 years thereafter in adulthood. An immunized mother will be able to pass IgG through the placenta to the fetus and provide passive immunity against neonatal tetanus until the child receives first tetanus vaccination at 2 months of age. Neonatal tetanus usually results from C. tetani colonization of the umbilical stump.

Question 8

Explain: (1) Special protease activity, viruses use for generating several functional viral proteins from single, large virally coded precursor polypeptide (2) Example of such virus

Answer 8

(1) Because viruses must use eukaryotic ribosomes for protein synthesis, they must convert their polycistronic genome into monocistronic mRNA. Some viruses accomplish this through production of polyprotein product from single mRNA transcript. This product is later cleaved by viral protease to generate complete set of functional, individual viral proteins. (2) Single-stranded, positive-sense, linear, nonsegmented RNA viruses such as echovirus (Picornaviridae family)

Question 9

Dx/Type: HBeAg persists for several months and host anti-HBeAg remain at low or undetectable levels

Answer 9

Suspect chronic hepatitis B infection with high infectivity

Question 10

(1) Tx for genital herpes (2) Its mechanism

Answer 10

(1) Antiviral drugs currently recommend for treatment of primary genital herpes include nucleoside analogs (e.g., acyclovir) (2) Incorporated into newly replicated viral DNA and ultimately terminate viral DNA chain synthesis

Question 11

Mechanism of Rheumatic fever

Answer 11

Autoimmune reaction occurs following untreated GAS pharyngitis. Antigenic similarity between antibacterial antigens and normal “self” antigens in heart and CNS are believe to cause formation of anti-self antibodies resulting in RF.

Question 12

Most common causes of septic arthritis: (1) in sexually active young adults (2) in children and non-sexually active adults

Answer 12

(1) N. gonorrhoeae (2) S. aureus

Question 13

(1) Likely Dx: facial pain, headache, and black necrotic eschar in nasal cavity in a patient with diabetic ketoacidosis (2) Next step to confirm Dx (3) Findings/Resuls of that step (4) Tx

Answer 13

(1) Mucormycosis (2) Histologic examination of affected tissue is necessary to confirm dx. (3) These fungi show broad nonseptate hyphae with right angle branching. (4) Surgical debridement & amphotericin B

Question 14

(1) Immune response to Mycoplasma pneumoniae & its clinically relevant effects (2) Name of major immune component involved

Answer 14

M. pneumoniae shares antigens with human erythrocytes, and when body mounts a response against these antigens it also lyses red blood cells leading to anemia. The antibodies causing this RBC destruction are referred to as cold agglutinins.

Question 15

Group B strep: (1) Prenatal screening protocol (2) Prophylaxis

Answer 15

Universal prenatal screening for group B strep colonization by vaginal-rectal culture at 35-37 weeks gestation recommended to identify colonized women who require (2) INTRAPARTUM antibiotics, most frequently with penicillin or ampicillin, to prevent neonatal GBS sepsis, pneumonia, and meningitis

Question 16

(1) Dx: subacute headache, fever, and neck stiffness in presence of lymphocytic CSF pleocytosis, modestly elevated CSF protein level, and otherwise normal CSF parameters (2) Most common causes

Answer 16

(1) Points to dx of Aseptic meningitis (2) Enteroviruses, including coxsackievirus and echovirus, are the most common causes of aseptic meningitis

Question 17

Reason for genetic instability of HCV

Answer 17

Its RNA-dependent RNA-polymerase lacks proofreading 3’ to 5’ exonuclease activity and its envelope glycoprotein contains hypervariable region prone to frequent genetic mutation

Question 18

(1) Dx: new onset genital vesicular rash, positive Tzanck smear in previously asymptomatic patient (2) Tx to prevent recurrence & why

Answer 18

(1) Primary genital herpes due to HSV-2 (2) Recurrences of genital herpes can be reduced through daily treatment with oral valacyclovir, acyclovir, or famciclovir; these drugs suppress reactivation of latent HSV infection. Condom use can help prevent a primary genital HSV infection, but does not prevent reactivation of latent infection.

Question 19

Anal carcinoma: (1) Associated virus(es) (2) Factors increasing risk

Answer 19

(1) Human papilloma virus (HPV) types 16, 18, and 31 strongly associated with anal and cervical squamous cell carcinoma (2) HIV infection increases prevalence of HPV infection and risk of anal carcinoma; this risk is further augmented in men who have sex with men.

Question 20

Changes in host range due to what mutation in virus

Answer 20

Mutation in viral encoded surface glycoprotein that mediates virion attachment to target host cell plasmalemma receptors

Question 21

Requirement for hepatitis D to infect hepatocytes

Answer 21

HBsAg of hepatitis B must coat the HDAg of hepatitis D before it can infect hepatocytes and multipy

Question 22

(1) Dx: AIDS patient with radiographic finding of ring-enhancing lesions in both cerebral hemispheres is most often indicative of toxoplasmosis (2) Tx

Answer 22

(1) Toxoplasmosis gondii (2) Pyrimethamine and sulfadiazine

Question 23

Mechanism of Diphtheria toxoid vaccine

Answer 23

Production of circulating IgG against exotoxin B subunit, effectively preventing disease