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mcq في الميكرو

مُساهمة من طرف ....ابن العرب.... في الأربعاء أكتوبر 29, 2008 2:54 pm

Choose the ONE best answer
35.1 Which one of the following is the most common cause of infections associated with prosthetic heart valves, intravenous catheters, and intracranial shunts?
A. Escherichia coli
B. Streptococcus pyogenes
C. Pseudomonas aeruginosa
D. Staphylococcus epidermidis
E. Actinomyces israelii
View Answer

Correct answer = D. Staphylococcus epidermidis is a gram-positive, coagulase-negative, novobiocin-sensitive bacterium. It is the most common cause of infections involving prosthetic devices. Other infections caused by Staphylococcus epidermidis include infective endocarditis in intravenous drug users, infection of intravenous peritoneal dialysis catheters and intracranial shunts, and urinary tract infections. Escherichia coli, Pseudomonas aeruginosa, Actinomyces israelii, and Streptococcus pyogenes are not commonly associated with any of the above infections.
35.2 The most common bacterial infection associated with intravenous drug abuse is
A. skin and soft tissue infections
B. osteomyelitis
C. infective endocarditis
D. embolic strokes that produce cerebral abscesses
E. pneumonia
View Answer

Correct answer = A. The high incidence of skin and soft tissue infections is caused by many factors, including “skin poppingâ€‌ (injecting drugs subcutaneously); escape of drugs into soft tissue intravenous injection by extravasation; presence of adulterants in the injection material; sharing contaminated needles; and the presence of pathogenic organisms on the skin. Group A streptococci and Staphylococcus aureus are the most commonly isolated organisms.
35.3 Which of the following is more likely a feature of atypical pneumonia rather than a pneumonia caused by Streptococcus pneumoniae?
A. High fever
B. Nonproductive cough
C. Gram-positive sputum stain
D Sudden onset
E. Rust-colored sputum
View Answer

Correct answer is B. Mycoplasma pneumoniae is the most common cause of atypical pneumonia. Atypical pneumonia is characterized by low-grade fever; an insidious onset; constitutional symptoms such as malaise, headache, and anorexia; a nonproductive cough; a gram-negative sputum stain; a patchy, interstitial infiltrate on a chest radiograph; and myalgias and arthralgias. Streptococcus pneumoniae (Pneumococcus) pneumonia would most likely present with sudden onset; chills and high fever; a gram-positive sputum stain; a parenchymal or lobar consolidation on a chest radiograph; and a cough that produces rust-colored sputum. Pneumococcus is the most common cause of community acquired pneumonia.
35.4 Bacteria with tumbling “end-over-endâ€‌ motility are isolated from the cerebrospinal fluid of a 2-day-old infant with meningitis. This organism is likely to be
A. Escherichia coli
B. خ²-Hemolytic streptococcus
C. Listeria monocytogenes
D. Haemophilus influenzae
E. Neisseria meningitidis
View Answer

Correct answer = C. Listeria monocytogenes, a short, gram-positive rod, has an unusual tumbling “end-over-endâ€‌ motility at 22آ°C, but not at 37آ°C. This property is useful in laboratory diagnosis because it rapidly differentiates the organism from all other gram-positive rods. In addition, the organisms produce a small zone of خ²-hemolysis around and under colonies grown on blood agar. Listeria monocytogenes can cause perinatal listeriosis. When symptoms are manifested early, the organisms are thought to have been transmitted in utero. In the early-onset syndrome, the infants are either born dead or die shortly after delivery. The late-onset syndrome is manifested as meningitis within the first 3 weeks after delivery. Adults, especially those who are immunocompromised, can occasionally develop meningoencephalitis and bacteremia caused by the organisms. The organisms are believed to be acquired primarily by ingestion of contaminated foods. Recent outbreaks of listeriosis have been linked to raw vegetables, raw and pasteurized milk (the milk was contaminated after pasteurization), and cole slaw. The organisms can invade and multiply within intestinal epithelial cells, as well as in phagocytes. The presence of neutrophils, low glucose, and increased protein in cerebrospinal fluid is suggestive of a bacterial etiology.
35.5 Dysphonia (changes in the voice) in a 2-year-old child with a grayish exudate in the posterior pharynx and massive, tender cervical lymphadenitis is most likely caused by
A. Corynebacterium diphteriae
B. Neisseria meningitidis
C. Group A streptococcus
D. Propionibacterium species
E. Erysipelothrix rhusiopathiae
View Answer

Correct answer = A. Corynebacterium diphteriae, an aerobic gram-positive rod, is the cause of diphtheria. A hallmark feature of the disease is the development of a grayish “pseudomembraneâ€‌ over the tonsils, larynx, and pharynx, which can obstruct breathing and cause cyanosis (a bluish color of skin and mucous membranes due to excessive concentration of deoxygenated haemoglobin in the blood). The membrane is not a true membrane. It consists of fibrin, red and white blood cells, and the organisms. It is deeply embedded and attempts to remove it may cause extensive bleeding. Intubation or tracheostomy may be required to prevent suffocation. Children with the disease often have dysphonia or difficulty in speaking. Corynebacterium diphtheriae secretes a potent toxin, which is absorbed into the mucous membranes of the respiratory tract. This toxin causes inflammation, sore throat, and fever. Difficulty in breathing (dyspnea) and prostration follow shortly thereafter. Damage to the heart may occur, leading to cardiac arrhythmia. It may also cause problems with vision, speech, and swallowing. Some individuals may experience difficulty in moving arms or legs. These manifestation generally subside spontaneously.
35.6 An 8-year-old girl presents to the emergency room with high fever, nuchal rigidity (stiff neck), widespread ecchymoses (effusion of blood beneath the skin) scattered over her body, and clinical evidence of hypovolemic shock. A spinal tap reveals increased neutrophils, increased protein, and low glucose. The patient has diffuse bleeding from all venipuncture and intravenous sites. She dies 24 hours later. An autopsy reveals bilateral adrenal hemorrhage and a purulent meningitis. Which of the following results would be expected from the Gram stain of cerebrospinal fluid collected in the emergency room?
A. Gram-positive diplococci
B. Gram-negative rods
C. Gram-negative cocci in clumps
D. Gram-positive rods
E. Gram-negative diplococci
View Answer

Correct answer = E. هذه بعض الاسئلة أقدمها لطلبة الثالثة بشري والباقي عندي محبكم في الله ابن العرب lol!
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....ابن العرب....
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تاريخ التسجيل : 08/10/2008

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رد: mcq في الميكرو

مُساهمة من طرف alwarphaly في السبت نوفمبر 01, 2008 3:59 am

study study study

Thank very much

really you are amazing
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alwarphaly
نائب مدير New Libya

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تاريخ التسجيل : 10/08/2008

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