Block 11 - Week 12 -bacterial Upper Respiratory Tract Infection

1.

A 2-year-old boy with fever and earache has a red bulging tympanic membrane on the left. Audiometry shows partial hearing loss on the left. What is the cause of hearing loss in this patient?

A.

Pressure on the tympanic membrane due to fluid in the middle ear
B.

Perforation of the tympanic membrane due to fluid in the middle ear
C.

Bacterial inflammatory damage to auditory ossicles
D.

Obstruction of the left Eustachian tube due to a viral upper respiratory infection
E.

Viral inflammation of the 8th nerve

Correct Answer
A. Pressure on the tympanic membrane due to fluid in the middle ear

Explanation
The red bulging tympanic membrane and partial hearing loss on the left suggest that there is fluid buildup in the middle ear, causing pressure on the tympanic membrane. This is a common condition known as otitis media with effusion, which occurs when the Eustachian tube becomes blocked, usually due to a viral upper respiratory infection. The fluid buildup can cause the tympanic membrane to bulge and affect hearing.

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2.

A 16-year-old boy was seen in the clinic for fever and painful swelling of his finger joints, wrists, and knees during the past week. He had a sore throat 3 weeks earlier that wasn’t treated. His doctor heard a heart murmur and ordered an anti-streptolysin O (ASO) antibody titer, which was elevated. What caused this illness?

A.

ASO antibodies cross-reacted with his joints and heart valve
B.

Group A streptococci disseminated from his throat to his joints and heart valve
C.

M protein disseminated from his throat to his joints and heart valve
D.

Anti-M protein antibodies cross- reacted with his joints and heart valve
E.

M protein bound to complement factor H to inhibit phagocytosis

Correct Answer
D. Anti-M protein antibodies cross- reacted with his joints and heart valve

Explanation
The correct answer is "Anti-M protein antibodies cross-reacted with his joints and heart valve". This is because the patient had a previous streptococcal infection, which led to the production of antibodies against the M protein on the surface of the bacteria. These antibodies can cross-react with proteins in the joints and heart valve, causing an immune response and inflammation in these areas. This condition is known as rheumatic fever.

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3.

What do otitis media and acute sinusitis have in common in respect to pathogenesis and therapy?

A.

Both result from obstruction of air passageways leading to fluid collections in air spaces
B.

Both are mostly caused by bacteria including genera of Streptococcus, Haemophilus, and Moraxella.
C.

Both are mostly caused by viruses including rhinoviruses, influenza viruses, and coronaviruses.
D.

Both are effectively treated with antibiotics like amoxicillin
E.

Both are effectively treated with decongestants like ephedrine and antihistamines like benedryl.

Correct Answer
A. Both result from obstruction of air passageways leading to fluid collections in air spaces

Explanation
Both otitis media and acute sinusitis have in common the fact that they both result from obstruction of air passageways leading to fluid collections in air spaces. This obstruction can be caused by various factors such as inflammation or infection. Therefore, both conditions share a similar pathogenesis. In terms of therapy, both may be effectively treated with antibiotics like amoxicillin, which suggests that bacterial infection can be a common cause for both conditions.

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4.

A 4-month-old child presents with a 3-day history of irritability and fever. Otoscopic examination demonstrates a bulging left eardrum. A significant proportion of this condition in young children can be prevented by immunization. What does this vaccine contain?

A.

Haemophilus influenzae type b capsular polysaccharide conjugated with bacterial proteins
B.

Bordetella pertussis components conjugated with other modified bacterial proteins
C.

Streptococcus pneumoniae capsular polysaccharide conjugated with bacterial proteins
D.

Haemophilus influenzae type b conjugated with streptococcal proteins
E.

Streptococcus pneumoniae capsular polysaccharide

Correct Answer
C. Streptococcus pneumoniae capsular polysaccharide conjugated with bacterial proteins

Explanation
The correct answer is Streptococcus pneumoniae capsular polysaccharide conjugated with bacterial proteins. This vaccine contains the capsular polysaccharide from Streptococcus pneumoniae, which is the bacteria commonly associated with causing ear infections in young children. The polysaccharide is conjugated with bacterial proteins to enhance the immune response and provide protection against the bacteria. Immunization with this vaccine can help prevent a significant proportion of ear infections in young children.

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5.

A 12-year-old boy recently arrived from Haiti presents with fever, difficulty swallowing, and the presence of a tough, adherent membrane in the pharynx. He is quickly given organism-specific antitoxin. A throat swab is submitted for culture and sensitivity testing. Which of the following best describes the morphologic and cultural characteristics of the most likely causative organism?

A.

Gram-positive, pleomorphic bacilli from growth on tellurite media
B.

Gram-negative bacilli from growth on MacConkey agar
C.

Gram-positive cocci in clusters from growth on blood agar
D.

Gram-negative bacilli from growth on chocolate agar
E.

Gram-positive cocci in chains from growth on blood agar

Correct Answer
A. Gram-positive, pleomorpHic bacilli from growth on tellurite media

Explanation
The presence of a tough, adherent membrane in the pharynx suggests a bacterial infection known as diphtheria. The most likely causative organism is Corynebacterium diphtheriae, which is a gram-positive, pleomorphic bacilli. The growth on tellurite media is a characteristic feature of this organism, as it produces black colonies on this type of agar.

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6.

A 15-year-old girl came to the clinic with a 2-day history of sore throat and fever. You discover enlarged erythematous tonsils with white exudates. Lymph nodes in the neck were enlarged and tender. A rapid antigen detection test for group A Streptococcus pyogenes was negative. What should you do?

A.

Suspect it is caused by Neisseria gonorrhoeae
B.

Give penicillin for presumed streptococcal sore throat
C.

Carry out a throat culture for Streptococcus pyogenes group A
D.

Suspect it is mononucleosis caused by Epstein-Barr virus

Correct Answer
C. Carry out a throat culture for Streptococcus pyogenes group A

Explanation
Based on the patient's symptoms of sore throat, fever, enlarged erythematous tonsils with white exudates, and enlarged and tender lymph nodes in the neck, along with a negative rapid antigen detection test for group A Streptococcus pyogenes, it is important to further investigate the possibility of a streptococcal infection. The most appropriate next step would be to carry out a throat culture for Streptococcus pyogenes group A. This will help confirm the presence of the bacteria and guide appropriate treatment with antibiotics if necessary. The other options, such as suspecting Neisseria gonorrhoeae or Epstein-Barr virus as the cause, or giving penicillin without confirmation, are not supported by the given information.

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7.

A 6-year-old boy in rural Indonesia, who had not been immunized, presented to the clinic with a 3-day history of fever, sore throat, cough, and respiratory stridor (noisy breathing). The doctor sees pharyngeal erythema as well as a gray membrane at the back of his tongue and over his tonsils. He is admitted to intensive care because of which immediate threat to his life?

A.

Toxin-mediated cardiac damage
B.

Toxin-mediated neuropathy
C.

Obstruction to his airway
D.

Aspiration pneumonia

Correct Answer
C. Obstruction to his airway

Explanation
The immediate threat to the boy's life is obstruction to his airway. The symptoms of fever, sore throat, cough, and respiratory stridor indicate that there is a blockage in his airway, which is causing difficulty in breathing. The presence of pharyngeal erythema and a gray membrane suggest that he may have diphtheria, a bacterial infection that can lead to the formation of a thick membrane in the throat, causing obstruction. Immediate medical attention and admission to intensive care are necessary to ensure that his airway remains open and he can breathe properly.

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