Quiz on Upper Respiratory Tract Infections

Mircobiology II (Test 2)

Small beta hemolytic colonies are seen on the blood agar plate for a throat culture (performed to identify the cause of pharyngitis).  They are transparent with large zones of beta hemolysis.  They are susceptible to bacitracin (positive) and PYR hydrolysis positive.  These colonies are most likely –

Streptococcus pyogenes (gp A)

After 18-24 hours of growth, catalase negative, gram positive, cocci are isolated from a throat culture. On the blood agar plate the organisms produce mucoid, convex colonies surrounded by a zone of alpha hemolysis. On the following day the colonies were umbilicate (depressed centers). The organism was susceptible to optochin (a zone of inhibition around the disc) and bile soluble. This organism is most likely

Streptococcus pneumoniae

Infection of the buccal (cheek) mucosa, tongue, or oropharynx by Candida spp. is:

thrush.

Enterococci can be described as:

able to hydrolyze bile esculin.

The development of glomerulonephritis is a problem that may be encountered by patients infected with:

S. pyogenes.

Which of the following must be placed in a CO₂ incubator (5-10% CO2) or candle jar because it requires increased CO₂ for best growth (organisms exhibiting this behavior are referred to as being capnophilic)?

S. pneumoniae

Numerous large, gray, non-hemolytic, translucent colonies are isolated from the blood agar plate of a urine culture.  Biochemical tests performed on these catalase negative, gram positive cocci give the following results:

Hippurate hydrolysis = positive Esculin hydrolysis = positive PYR hydrolysis = positive

Voges-Proskauer = positive Arginine dihydrolase = positive Ribose fermentation = positive

This organism is most likely -

Enterococcus faecalis

The major etiologic agent of bacterial endocarditis in the United States is:

Viridans streptococci.

A gram-positive bacillus, which grew on Tinsdale agar, is esculin hydrolysis–negative, urease-positive, and nonlipophilic. The organism can be identified as:

Corynebacterium ulcerans.

A pharyngeal specimen is inoculated on cystine-tellurite blood agar, modified Tinsdale agar, and MacConkey agar. After 48 hours of incubation, black colonies with a brown halo are observed on the Tinsdale agar and gray colonies are isolated from the cystine-tellurite agar. However, no growth is observed on the MacConkey agar. Which one of the following statements explains this discrepancy?

No discrepancy is present; this organism does not grow on MacConkey agar.

Bacteria described as being coryneform have which of the following morphologic features?

Resemble and are often referred to as Chinese letters

Performance of the “factor requirement test” for Haemophilus involves the:

inoculation of unsupplemented media with a light suspension of the organism and placement of X and V factor disks on the agar surface.

Which of the following Haemophilus species is a primary pathogen found in the upper respiratory tract? This organism requires both X and V factors. Therefore it grows on the chocolate agar plate but not the sheep blood agar plate unless it is modified.

H. influenzae

During the catarrhal stage of pertussis, symptoms are:

runny nose and mild cough.

If real-time polymerase chain reaction (PCR) is performed on a Bordetella isolate, then it must be noted that this type of swab is unacceptable for collection because of the presence of which of the following inhibitory factors?

Calcium alginate

A diabetic patient has developed gas gangrene of the right foot. The most likely anaerobe causing this infection is:

Clostridium perfringens.

The most likely identification of an anaerobic gram-positive bacillus that produces spores is:

Clostridium.

Which Clostridium species is most often recovered from a wound infection with gas gangrene?

C. perfringens

A 37 y/o patient suffering from acute lymphocytic leukemia complains of pain and tenderness of the tongue and soft palate. Upon examining the patient the admitting physician finds a white coating covering the mucous membranes of the oral cavity. She sends a skin scraping to the lab and receives a report stating that budding yeast with psuedohyphae are present. A germ tube test and sucrose assimilation test is performed and both are positive. Examination of the cornmeal agar plate reveals the presence of blastoconidia, pseudohyphae, true hyphae, and chlamydospores. The causative agent is most likely:

Candida albicans

The most commonly isolated yeast in clinical specimens is:

Candida albicans.

Which yeast identification system uses chromogenic substrates to assess specific enzyme activity usually detected within 4 hours?

Microscan

A patient indicates that he has not brushed his teeth in over 20 years. He has significant dental calculi and advanced periodontal disease. Scrapings are collected from the infected areas of the gums for evaluation. Which parasite is most likely to be associated with colonization of the oral cavity in this patient?

T.tenax

The major cause of the common cold during the fall and spring are –

rhinoviruses

Most viruses are shed from the respiratory or gastrointestinal tracts but the specimen of choice to diagnose cytomegalovirus (CMV) infection is/are –

urine

Tests to demonstrate antibodies to EBV using the Davidsohn differential absorption test for heterophil antibody is negative.  Serologic testing for Epstein-Barr virus (EBV) specific antibodies is performed.  The following results are obtained:
VCA – IgM = negative early antigen-diffuse (EA-D) antibody = negative
VCA – IgG = positive   EBV nuclear antigen (EBNA) antibody = positive
Based on these results the diagnosis should be -

past infection with EBV

Which organism is not a normal inhabitant of the respiratory tract?

N. gonorrhoeae

Inflammation of the larynx that is usually associated with the common cold or influenza syndromes and that is caused almost exclusively by viruses is:

laryngitis.

An infection of the epiglottis and other soft tissues above the vocal cords, whose presentation typically includes fever and difficulty in swallowing because of the pain, drooling, and respiratory obstruction with inspiratory stridor, is:

epiglottitis.

Which of the following is a life-threatening, non-suppurative (no pus production) and non-invasive condition associated with S. pyogenes infection which can lead to kidney failure?

acute glomerulonephritis      

Small alpha hemolytic colonies are seen on the blood agar plate for a throat culture.  These organisms commonly colonize the upper respiratory tract.  Some species are associated with dental caries and can be a significant cause of subacute bacterial endocarditis following oral surgery.  These organisms are most likely –

iridans streptococci

The most commonly encountered, life threatening, disease state caused by group B streptocococci is -

neonatal sepsis

Which species of bacteria is responsible for causing diseases such as rheumatic fever, glomerulonephritis, and exudative pharyngitis?

S. pyogenes

What morphologic feature is a major consideration in determining an identification scheme for streptococci?

Hemolytic pattern

A catalase-positive, gram-positive bacillus that is not acid-fast, does not branch, and does not form spores could possibly belong to which group of bacteria?

Corynebacterium

Bacteria described as being coryneform have which of the following morphologic features?

Resemble and are often referred to as Chinese letters

After 48 hours of incubation, black colonies with a dark brown halo are observed on Tinsdale agar. What type of toxin does this organism produce?

Exotoxin

In a phenomenon known as satelliting, tiny colonies of Haemophilus spp. may be observed growing on sheep blood agar close to colonies of:

Staphylococcus aureus.

A 6-year-old boy was diagnosed with purulent conjunctivitis caused by a species of Haemophilus. What would the biochemical profile of the organism be?

Growth requirements require both X and V factors; the organism is hemolytic on rabbit blood.

The mode of transmission of B. pertussis can best be described as:

person-to-person contact.

Which of the following toxins contributes to the virulence of B. pertussis and works by hemolyzing red cells and activating cyclic adenosine monophosphate, which inactivates several types of host immune cells?

Adenylate cyclase toxin

The most likely identification of an anaerobic gram-positive bacillus that is a very large fusiform bacillus with one pointed end and one blunt end is:

Leptotrichia.

The most likely identification of a bile-resistant, kanamycin-resistant, colistin-resistant, and vancomycin-resistant anaerobic gram-negative bacilli is:

B. fragilis group.

A strict anaerobe that produces terminal spores “tennis racquet” is:

Clostridium tetani

A patient with leukemia is diagnosed with a Candida infection after receiving several doses of chemotherapy. The most likely yeast causing the infection is:

C. tropicalis.

This organism is larger than a human leukocyte making phagocytosis impossible. This organism is also able to stimulate a Type IV hypersensitivity reaction?

B. mandrillaris

The etiologic agent of herpangina is –

coxsackie A virus

Adenoviruses are responsible for causing diseases such as keratoconjunctivitis, pneumonia, hemorrhagic cystitis, and gastroenteritis in children. Transmission is usually via:

respiratory secretions.

The etiologic agent of exanthum subitum ( or roseola infantum, an acute, self-limited disease of infants characterized by high fever and a maculopapular rash) and possibly multiple sclerosis as well, is –

human herpes virus 6

With ________________, viral DNA is incorporated into the DNA of infected B lymphocytes.  Viral antigen is then expressed on the surface of the infected cells stimulating T lymphocytes to divide.  These activated T lymphocytes appear on the peripheral blood smear as atypical lymphocytes or “Downey cells”.

infectious mononucleosis

Adenoviruses are associated with respiratory infections and there are 85 different serotypes, and 33 have distinct genotypes. It is not necessary to classify the viruses based on the specific serotypes in the diagnostic laboratory because:

genotype and serotype do not need to be differentiated unless there is an identifiable clinically significant property associated with the virus.

In general, yeast reproduces asexually by the formation of:

blastoconidia.

A patient with diabetes is experiencing creamy patches on his tongue and mucous membranes. Cultures are performed, and yeast is recovered. His diagnosis is most likely:

thrush.

A strict anaerobe that produces terminal spores “tennis racquet” is:

Clostridium tetani

The most likely identification of an anaerobic gram-positive bacillus that produces spores is:

Clostridium

The most likely identification of an anaerobic gram-positive coccus that is resistant to metronidazole is:

Streptococcus.

During the paroxysmal stage of pertussis, symptoms are:

severe and violent coughing.

If real-time polymerase chain reaction (PCR) is performed on a Bordetella isolate, then it must be noted that this type of swab is unacceptable for collection because of the presence of which of the following inhibitory factors?

Calcium alginate

Although a useful test in the past, the particle agglutination assay for the detection of H. influenzae, type b, capsular polysaccharide antigen is no longer reliable because of:

the increased use of H. influenzae, type b, vaccination.

To increase the sensitivity of direct Gram-stain examination of body fluid specimens, the specimens are usually:

centrifuged before staining.

On which of the following media does Corynebacterium diphtheriae produce black colonies with brown halos?  Diphtheroids may produce black colonies but they do not produce brown halos.

Tinsdale 

Numerous pus cells and gram positive cocci in pairs, chains, and clusters are seen on the gram stain of pus from an abdominal wound.

After 18-24 hours at 37 ̊C, the organisms on the blood agar plate produce large, gray, translucent, non-hemolytic colonies.

The following biochemical characteristics are obtained:

catalase = negative
PYR hydrolysis = positive
esculin hydrolysis = positive
Voges-Proskauer = positive
Growth in 6.5% NaCl = positive
Arginine dehydrolase = positive

The identification of this organism is -

Enterococcus faecalis (group D)

Rheumatic fever is a poststreptococcal sequelae typically associated with:

Pharyngitis associated with group A streptococci

Which organism produces the CAMP factor enhancing beta-hemolysis in the presence of the S. aureus beta-lysin?

Group B streptococci

Enterococci can be described as:

able to hydrolyze bile esculin.

An infection of the pharynx that is normally called sore throat, whose presentation includes erythematous and swollen tissue and which is characterized by inflammatory exudates, vesicles, and mucosal ulceration or by nasopharyngeal lymphoid hyperplasia, is:

pharyngitis.

An inflammation of the mucous membranes of the oral cavity caused mostly by herpes simplex virus is:

stomatitis.

Also called acute necrotizing ulcerative gingivitis or trench mouth, which condition is a mixed bacterial spirochetal infection of the gingival edge?

Vincent angina

The presence of Koplick’s spots (bright red spots with a blue-white central speck on the mucosa of the lips and oral cavity) is diagnostic for –

rubeola (measles)

What family of viruses is the causative agent of self-limited, respiratory, ocular, and gastrointestinal diseases in infants less than 4 years of age and military recruits?

adenoviruses

Which yeast identification system uses chromogenic substrates to assess specific enzyme activity usually detected within 4 hours?

MicroScan

The primary plating medium used to select out Clostridia spp. would be:

phenylethyl alcohol agar (PEA).

Because of its longer shelf life, the medium of choice to cultivate Bordetella spp. is:

Regan-Lowe agar.

The best medium for culture of Bordetella pertussis is:

Regan-Lowe agar

Of the following media, which provides the NAD necessary for the growth of Haemophilus spp.?

Chocolate agar

Growth of most Haemophilus species in culture is enhanced by:

5% to 10% carbon dioxide (CO₂).

A 13-year-old girl presented to her physician complaining of being tired, having a mild sore throat and fever. She appears to have a grey coating on her tonsils when examined by the physician. The most logical etiologic agent associated with the patient’s illness is:

diphtheriae.

Generally speaking, nutritionally variant streptococci require what ingredient not found in most conventional media?

Vitamin B₆

Which of the following is an important cause of neonatal sepsis (as a result of colonization of the vaginal tract of pregnant women)?

S. agalactiae (group B)   

What is the antibiotic of choice for beta-hemolytic Streptococcus ?

Penicillin

A patient has repeated presented to their primary care provider with recurrent chronic laryngitis. Antibiotic treatment has not resolved the condition. The primary care provider requested a culture and sensitivity. The laboratory reported growth of normal oropharyngeal bacterial flora and a few creamy white, raised, star-like non-hemolytic colonies on blood agar. The primary care physician should consider:

consider treating for chronic fungal laryngitis, as it may be associated with Candida spp.

Which of the following is a life-threatening, non-suppurative (no pus production) and non-invasive condition associated with S. pyogenes infection which can lead to kidney failure?

acute glomerulonephritis    

A relatively common illness in young children, primarily those younger than 3 years of age, whose presentation includes variable fever, inspiratory stridor (difficulty in moving enough air through the larynx), hoarseness, and a harsh, barking, nonproductive cough, is:

laryngotracheobronchitis.