July 2020 Flashcards
Which one of the following is a large gram-positive rod that causes necrosis of tissue by producing an exotoxin that degrades lecithin resulting in the lysis of cell membranes? A.) Bacillus anthracis B.) Bacillus cereus C.) Clostridium perfringens D.) Clostridium tetani E.) Clostridium botulinum
C.) Clostridium perfringens. This is the etiological agent of gas gangrene. These organisms grow in traumatized tissues and produce alpha toxin (lecithinase) which damages cell membranes. Degradative enzymes produce gas in tissue.
A 14 y.o. girl who was sent home from school because she had fever of 38 degrees C, a severe headache and was falling asleep in class. When her fever rose to 39.5 degrees C, her mother took her to the emergency room, where her BP of 60/20 and several petechial hemorrhages were found. Gram negative diplococci were seen under Gram stain of the spinal fluid. Which one of the following is most likely to cause the fever, hypotension and petechial hemorrhage? A.) Endotoxin B.) IgA Protease C.) Oxidase D.) Pilus Protein E.) Superantigen
A.) Endotoxin. The causative agent in this case is Neisseria meningitidis. which caused the Meningoccocemia N. meningitidis has three important virulence factors:
- Polysaccharride Capsule: resisting phagocytosis
- Endotoxin: causes fever, shock, and other pathophysiologcal changes
- IgA Protease: helps the bacterial attachment to the membranes of the upper respiratory tract
3. Your patient a 75 y.o. woman with a 110 pack-year history of cigarette smoking who has now a fever of 39 degrees C and a cough productive of yellowish sputum. Gram staining of the sputum show small gram negative rods. There is no growth on blood agar, but colonies grow on chocolate agar supplemented with hemin and NAD. Which of the following bacteria is the most likely cause of her pneumonia? A.) Bordatella pertussis B.) Haemophilus influenzae C.) Klebisiella pneumoniae D.) Legionella pneumophilia E.) Pseudomonas aeruginosa
B.) Haemophilus influenzae. This is a very fastidious gram negative organism that’s why it will not grow on a blood agar plate. Growth of this organism in a laboratory setting requires Factors V (NAD) and X (heme) which is often found in chocolate agar.
The reagent used to distinguish staphylococci from streptococci is A.) Fibrinogen B.) Fibrin C.) Catalase D.) Hydrogen Peroxide E.) Fibronectin
D.) Hydrogen Peroxide. The staphylococci are aerobic while the streptococci are aerotolerant anaerobes. Streptococci ferment even in the presence of full oxygen and lack catalase. A standard quick test is the test mixing staphylococci with hydrogen peroxide. The generation of oxygen bubbles indicates that a Gram-positive coccus is a Staphylococcus rather than a Streptococcus. A coagulase test using serum to see if fibrinogen is clotted is used to distinguish the coagulasepositive staphylococci from coagulase-negative staphylococci.
Remember! Catalase is the enzyme while H2O2 is the reagent used in Catalase Test.
One effect of diabetic neuropathy is increase in glomerular capillary pressure which damages the glomeruli. ACE inhibitors help with a small drop in the GFR. What is not a way to decrease GFR? A.) Efferent arteriole constriction B.) Afferent arteriole constriction C.) Increase plasma concentration D.) Ureter constriction
A.) Efferent arteriole constriction. Efferent arteriole increases the GFR.
Vanders
A 53-year-old woman is found, by arteriography, to have 50% narrowing of her left renal artery. What is the expected change in blood flow through the stenotic artery? A.) Decrease to 1⁄2 B.) Decrease to 1⁄4 C.) Decrease to 1⁄8 D.) Decrease to 1⁄16 E.) No change
D.) If the radius of the artery decreased by 50% (1/2), then resistance would increase by 24, or 16 (R = 8ηl/πr4). Because blood flow is inversely proportional to resistance (Q = ΔP/R), flow will decrease to 1/16 of the original value.
A 46-year-old woman has hirsutism, hyperglycemia, obesity, muscle wasting, and increased circulating levels of adrenocorticotropic hormone (ACTH). The most likely cause of her symptoms is
A.) Primary Adrenocortical Insufficiency (Addison Disease)
B.) Pheochromocytoma
C.) Primary Overproduction of ACTH (Cushing Disease)
D.) Treatment with Exogenous Glucocorticoids
E.) Hypophysectomy
C.) Primary Overproduction of ACTH (Cushing Disease). This woman has the classic symptoms of a primary elevation of adrenocorticotropic hormone (ACTH) (Cushing disease). Elevation of ACTH stimulates overproduction of glucocorticoids and androgens. Treatment with pharmacologic doses of glucocorticoids would produce similar symptoms, except that circulating levels of ACTH would be low because of negative feedback suppression at both the hypothalamic (corticotropin-releasing hormone [CRH]) and anterior pituitary (ACTH) levels. Addison disease is caused by primary adrenocortical insufficiency. Although a patient with Addison disease would have increased levels of ACTH (because of the loss of negative feedback inhibition), the symptoms would be of glucocorticoid deficit, not excess. Hypophysectomy would remove the source of ACTH. A pheochromocytoma is a tumor of the adrenal medulla that secretes catecholamines.
If you are suspecting a patient is suffering from atherosclerosis, what kind of artery is it usually seen in? A.) Elastic artery B.) Muscular artery C.) Arterioles D.) A and B E.) B and C
D.) Atherosclerosis is a disease of elastic and muscular arteries which are the common types affected by atherosclerosis because these are the types of arteries that are needed for pumping blood and distributing blood throughout the body. Coronary artery is an example of a muscular artery while the aorta is an example of an elastic artery.
After an automobile accident, a back muscle that forms the boundaries of the triangle of auscultation and the lumbar triangle receives no blood. Which of the following muscles might be ischemic? A.) Levator scapulae B.) Rhomboid minor C.) Latissimus dorsi D.) Trapezius E.) Splenius capitis
C.) The latissimus dorsi forms boundaries of the auscultation and lumbar triangles and receives blood from the thoracodorsal artery. The levator scapulae, rhomboid minor, and splenius capitis muscles do not form boundaries of these two triangles. The trapezius muscle forms a boundary of the auscultation triangle but not the lumbar triangle. The levator scapulae, rhomboid minor, and trapezius muscles receive blood from the transverse cervical artery. The splenius capitis muscle receives blood from the occipital and transverse cervical arteries.
A 21 y.o. man sustained a laceration wound to his upper lip from a fall he had while celebrating his 21st birthday. After suboptimal care for the cut, the wound became infected as evidenced by redness, warm to touch, and swelling around the area of the cut. The patient believed it was a minor infection and neglected to seek medical attention. Several days following the infection, the patient presented to the emergency department demonstrating symptoms of cavernous sinus syndrome. In your assessment, you surmise that a retrograde infection had spread from his facial laceration to his cavernous sinus. Through which of the following structures did the infection likely spread to this patient’s cavernous sinus? A) Inferior Ophthalmic Vein B) Maxillary Vein C) Inferior Sagittal Sinus D) Ophthalmic Artery
A) Inferior Ophthalmic Vein. The inferior ophthalmic vein receives a small fraction of the drainage from the facial vein and superior labial vein. The ophthalmic vein drains into the cavernous sinus, and therefore the inferior ophthalmic vein can allow the transport of a retrograde infection originating in the superior labial vein region into the cavernous sinus.
