5.12.2015 Uworld Notes Flashcards
Wool processing, fever, chest pain, hemoptysis, widened mediastinum, gram positive rods form medusa head colonies on standard media. The bacteria most likely produce?
Antiphagocytic D glutamate gapsule
Pulmonary anthrax–>Hemorrhagic mediastinitis
Spores–>Cells–>Three part anthrax toxin
Antiphagocytic capsule is required for pathogenicity. Capsule contains D glutamate instead of polysaccharide.
B. anthracis is aerobic organism that can be grown on standard culture media and forms nonhemolyzing colonies. Forms chains=Serpetine or medusa head colonies.
Other virulence factors:
Protein A=Staph aureus (binds Fc portion of IgG and prevents opsonization and complement killing of bacteria)
Polyphosphate granules=Corynebacterium diptheriae can be seen on Loeffler medium and stained with methylene blue.
Peritrichous flagella: Flagella distributed uniformly over entire surface of bacterial cell. Characteristic of motile organisms like Proteus mirabilis.
Crohn’s disease: Patient overexpresses transcription factor NF-KB which stimulates:
Cytokine production
Genetics:
Crohn’s=HLA-DR1/DQw5
Ulcerative colitis=HLA-DR2
NOD2=Nucleotide binding oligomerization domain. Acts as intracellular microbial receptor that triggers NF-kB pathway. NF-kB is responsible for cytokine production. Causes chronic inflammation in GI tract.
5 yo boy with severe recurrent respiratory infections (infected by specific type of bacteria every time). Patient’s T lymphocytes lack IL-12 receptor. Supplementation with which substances would improve patient’s condition?
No IL12 receptor=Helper T cells can’t differentiate into Th1 population. Synthesis of IFN-gamma doesn’t occur which is required to activate macrophages.
Macrophages req. for delayed hypersensitivity reactions and cytotoxicity against intracellular organisms such as mycobacteria. Individuals with IL12 receptor deficiency suffer from severe mycobaterial infections. IFN-gamma administration is needed.
Formation of TH2 helper T cells is induced by IL-4 and B cell differention into palsma cells and secretion of Ig is dependent on cytokines produced by TH2 cells. Administration of Ig or IL-4 would improve response to extracellular viruses or bacteria.
Tetrology of Fallot: What does squatting do?
Increases SVR and decreases right to left shunting thereby increasing pulmonary blood flow.
Intellectual disability, 47 chromosomes, what is likely on further evaluation?
Tall stature, gynecomastia, azoospermia, cryptochidism, infertility. Klinefelter Syndrome (47, XXY) Meitoic nondisjunction during parental gametogenesis that resutls in 47, XXY. Variants include 46XY/47XXy mosaicism and 48, XXXY. Higher number of X chromosomes=WORSE manifestations.
Features:
- Primary testicular failure due to fibrosis of seminiferous tubules. Small firm testes. Tesosterone deficiency from leydig cell dysfunction. Gonadotropin levels increased secondary to gonadal failure.
- Eunuchoid body habitus: Gynecomastia, absent facial/body hair, decreased muscle mass, tall.
- Intellectual disability/psychosocial problems.
Other conditions: Marfan=Aortic root dilation, scoliosis, arachnodactyly, inherited defect of extracelluar matrix protein fibrillin. Fragile X syndrome: Macroorchidism, large jaw, intellectual disability. Mutations in Fragile X mental retardation 1 gene. Turner syndrome (45, XO): Short stature, broad chest, primary amenorrhea. Prader Willi syndrome: Short stature, hypotonia, ID, obesity. Microdeletion affecting paternal chromosome 15q11-13 region.
6 month old male recurrent infections: Defective Ig isotype switching. Large tonsils and palpable lymph nodes. Which of the following Ig most likely overproduced?
IgM
Genes coding for constant regions of heavy Ig chains lie next to each other in order: IgM, IgD, IgG, IgE, IgA. No modification=IgM will be only Ig expressed by B lymphocytes. This is initial Ig synthesized by all B lymphoctyes prior to class switching. Modification of Ig genome during class switching happens by DNA recombinase enzyme.
Clinical effects of hyper IgM=recurrent sinus and airway infections (deficient IgA). Treatment is with IV gamma globulin. Results most commonly from genetic absence of CD-40 ligand on T lymphocytes or from genetic deficiency in enzymes responsible for DNA modification that takes place during isotype switching.
IgA class switching is induced by B lymphocyte stimulation with Transforming Growth Factor-beta. IgE responsible for atopic disease: Allergic rhinitis, asthma, atopic dermatitis. Defnse against helminth parasites. IgE isotype switching initiated by IL-4 stimulation. When two IgE bound to mast cell or basophil attach to Ag they signal release of granular contents. IgG: Provides passive immunity to infants for up to 6 months. IgG is able to fix complement. IgG is most effective opsonin. Immunity against bacterial toxins. IgD: Concurrently expressed with IgM on membranes of B lymphocytes. Acts as cell surface Ag receptor for these cells.
10 yo boy brought to ER after fevers and chills. Dull pain above left knee. Tenderness 3 cm above kneecap. Radiographs show soft tissue swelling and periosteal reaction over lower end of femur. What organism caused this?
Staph aureus. Childhood. Hematogenous seeding during episode of bacteremia. Long bones.
Sickle cell: Hematogenous seeding to infarcted bone. Salmonella. Staph aureus. Long bones.
Pott disease: Hematogenous seeding from lungs. Mycobacterium tuberculosis. Vertebrae.
Diabetes: Spread from infected foot ulcer. Polymicrobial. Bones of feet.
Patients with impaired mobility: Spread from pressure sores. Polymicrobial. Sacrum and heels.
Recent trauma or surgery: Direct inoculation. Polymicrobial.
Enterococcus faecalis-Endocarditis, meningitis, UTI, vertebral osteomyelitis after recent UTI via bacteremic spread.
Morazella catarrhalis: Part of normal flora of URI. Otitis media and sinusitis. Exacerbation of COPD.
Staphylococcus epidermidis: Colonize IV catheters and prosthetic heart valves, orthopedic hardware. Bacteremia and sepsis.
Streptococcus agalactiae: GI and UG tract. Infants=sepsis, pneumonia, meningitis.
Streptococcus pneumoniae: Most common etiologic agent of community acquired pneumonia. Can cause otitis media in kids, sinusitis, meningitis, sepsis.
Strep pyogenes: Second most common cause of hematogenous osteomyelitis. Pharyngitis and skin infections=impetigio and necrotizing fascitis.
Ulnar nerve course
Posteromedially in upper arm and enters forearm after passing posterior to medial epicondyle of humerus. Funny bony=ulnar nerve injury.
Can be injured where it passes between hook of hamate and pisiform bone.
Radial nerve injury causes wrist drop, sensation loss to posterior arm, posterior forearm, part of dorsal thumb.
Musculocutaneous nerve injury: Loss of sensation over lateral forearm and paralysis of forearm flexors at elbow.
Axillary nerve injury: Results from fracture of surgical neck of humerus or other shoulder trauma. Lose sensation over lateral upper arm.
52 yo male: Chronic cough with hemoptysis for past three weeks.
PE: Right sided face and right arm swelling. Engorgement of subcutaneous veins on right side of neck. Which vein is obstructed?
Brachiocephalic
Formed by union of right subclavian vein and right internal jugular vein.
External jugular vein drains into right subclavian. Obstruction of right brachiocephalic will cause venous congestion of structures drained by external jugular. Right brachiocephalic vein also drains lymph from right UE, right face and neck, right hemithorax, right upper quadrant of abdomen. BRACHIOCEPHALIC VEIN DRAINS IPSILATERAL JUGULAR AND SUBCLAVIAN VEINS. Bilateral brachiocephalic come together to form SVC.
Internal jugular vein drains brain and superficial face and neck. Obstruction of internal jugular would not cause arm swelling.
External jugular vein drains scalp and portions of lateral face.
Subclavian vein is continuation of axillary vein: Both drain blood from UE.
SVC obstruction: BOTH sides of face, neck, and chest, and BOTH ARMS.
Fractured 12th rib may injure?
Parietal pleura medially
Kidney laterally.
11th and 12th ribs are floating (not bound to anterior rib cage by cartilage. Distal tip of 12th rib can be displaced into retroperitoneum and lacerate kidney.
Left 9th, 10th, 11th ribs overlie spleen.
8th, 9th, 10th, 11th ribs overlie liver.
Inferior margin of left lung is at 10th rib. 1sth through 6th rib fractures have greatest chance of damaging visceral pleura.
Tachycardia, fast and irregular heart beat, consumed large amount of alcohol. Which EKG finding?
Absent P waves.
Atrial fibrillation: Precipitating factors=binge alcohol consumption, increased cardiac sympathetic tone, pericarditis.
QT prolongation predisposes to torsades de pointes where heart rate is usually regular.
High QRS voltage=sign of ventricular hypertrophy. Most commonly results from prolonged untreated HTN. No irregular rhythm.
QRS prolongation=BBB; regular heart rate; ventricular dyssynchrony or slowed impulse conduction.
ST elevation=transmural MI.
Idiopathic thrombocyotopenic purpura
Formation of autoantibodies against platelets. Petechiae, ecchymoses, bleeding after minor trauma. May follow viral infection or immunization.
Shaken baby syndrome: Subdural hematoma with bilateral retinal hemorrhages.
Increased AG metabolic acidosis. Mental status improves with treatment and increase in serum bicarb and sodium levels, decrease in serum osmolality and drop in serum potassium. Which was given to the patient?
Insulin and N.S.
Patient is suffering from diabetic ketoacidosis: Pts present with AMS, dehydration, abdominal pan, tachypnea, fruity odor to breath.
Insulin and hydration are primary treatments for DKA.
Insulin allows cells to use glucose as energy and decreases lipolysis and production of ketone bodies. Decrease in production of ketone bodies will rise plasma bicarb since ketone bodies are principal acid produced in DKA. Insulin causes shift in K+ resulting in decrease in K+ in serum.
Metabolic acidosis may develop in hypoaldosteronism which is treated with mineralocorticoids. However, acidosis is typically mild and without increased AG. Mineralocorticoids act by causing retention of sodium, water, and increases excretion of K+ and H+ ions. AMS is not characteristic. Treatment with mineralocorticoids would increase serum osmolality too.
Loop diuretics would decrease potassium concentration and increase serum bicarb. But decrease sodium concentration and increase serum osmolality due to increase in free water excretion.
Prokaryotic ribosomes contain three types of rRNA and >50 proteins. What is function of 16S rRNA in prokaryotic ribosomes?
Contains nucleotide sequence complementary to mRNA sequence.
16S has sequence complementary to Shine-Dalgarno sequence in all prokaryotic mRNA (10 bases upstream from AUG start codon on prokarytoic mRNA).
Complementary sequences allow mRNA and 30S ribosomal subunit to bind in preparation for protein translation. Once mRNA bound to 30S subunit, protein synthesis starts.
Peptidyltransferase=Function of 23S rRNA found in 50S ribosomal subunit facilitates peptide bond formation in protein translation.
Aminoacyl-tRNA synthetases present in cytosol facilitate formation of aminoacyl tRNAs.
Translocation: ribosome advanced to next mRNA codon to be translated. Facilitated by elecongation factor G with energy from GTP.
During translation: mRNA codon in ribosomal A site binds income aminoacyl tRNA. Occurs over and over until stop codon enters A site. Release factors bind ribosome terminating translation and causing separation of ribosomal complex.
Gradual thinning of epidermis happens in aging.
Aesthetic impact: Decrease in dermal collagen and elastic fibers. Inelastic skin sags and demonstrates fine wrinkles.
Proline hydroxylatoin would decrease indirectly during aging because collagen created decrease. Most direct cause of wrinkling is reduced synthesis of collagen fibrils.
Fibrillin 1 aids in development of extracellular matrix microfibirls: Create scaffolding for deposition of elastic fibers. MARFAN.
