uPPER rESPIRATORY
The infectious diseases listed below are listed with the most commonly associated bacterium, EXCEPT:
Aspergillus niger - "Black lung"
An aerobic Gram negative coccobacillus was isolated from a nasopharyngeal swab 48 hours after culture from a 6-month-old with the following culture characteristics on Bordet-Gengou agar: Small zones of beta-hemolysis Urease: positive (24 hours) Oxidase: negative Motility: negative The MOST probable identification of this isolate is:
Bordetella parapertussis
An autopsy of a 1-year-old female admitted to the emergency room 4 hours prior to her death revealed Waterhouse-Friderichsen syndrome. Blood and nasopharyngeal cultures taken prior to her death should reveal an oxidase-positive, Gram-negative diplococcus with the following biochemical reactions:
Glucose positive, Maltose positive, Lactose negative and Sucrose negative
An eleven-year-old girl was seen in the emergency room with sudden onset of sore throat, fever and dysphagia, the latter accompanied by an intermittent sensation of choking. The bacterial species shown in the upper photograph of a chocolate agar plate was recovered from a throat culture. The most likely bacterial species based on the test shown in the lower photograph is:
Haemophilus influenzae
Satellitism observed in cultures is most commonly associated with which of the following bacteria?
Haemophilus influenzae
The colonies growing on blood agar (upper image) were recovered from a sinus aspirate from a patient with acute sinusitis. The large, Staphylococcus colonies are obvious; however, note the satellite growth of small colonies. Small, Gram negative coccobacilli are observed in Gram stains. The pattern of bacterial growth around the X and V filter paper strips in the image to the right confirms these satellite colonies are Factor X and V dependent. From the list of multiple choices, select the name of this isolate.
Haemophilus influenzae
Which of the following organisms has been isolated from nasal secretions and causes atrophic rhinitis, a tissue-destructive disorder in the nose?
Klebsiella pneumoniae subsp. ozaenae
The bacterial species, a typical colony of which is illustrated in this photograph, and a common bacterial cause of otitis externa, also known as "swimmer's ear", can be identified as:
Pseudomonas aeruginosa
A gram-negative coccobacillus produces small gray colonies surrounded by a zone of hemolysis on potato-blood-glycerol agar. The organism also grew on chocolate agar, but NOT on sheep blood agar. This is MOST likely to be which organism?
Bordetella pertussis
Which of the following growth factor(s) is necessary for the proper culture of Haemophilus influenzae?
Both X and V factors
Illustrated in this photograph is a blood agar plate inoculated with a beta hemolytic streptococcus obtained from a throat culture of a patient with acute pharyngitis. A 0.04 µg bacitracin (left) disk and a SXT disk (right) had been placed in the areas of streaking. The reactions observed allow the most likely presumptive identification of a streptococcus belonging to Lancefield group:
Group A
Acute obstructive epiglottitis, both in adults and children, is most commonly caused by a specific bacterial species that can be recovered on chocolate agar and requires both hematin and NAD. The most likely identification is:
Haemophilus influenzae
The small, transparent, gray-yellow 48 hour colonies incubated at 37°C. as illustrated in the upper photograph, are surrounded by wide zones of beta hemolysis. This culture was obtained from a throat swab of a patient with pharyngitis. The lower photograph demonstrates susceptibility of this isolate to the bacitracin "A" disc. What is the presumptive identification of this isolate?
Streptococcus pyogenes (Group A)
Which of the following substances produced by Group A Streptococci is responsible for producing type specific immunity?
M antigen
A patient with an upper respiratory infection submits a sputum for culture. A gram stain performed on the sputum specimen reveals gram-negative diplococci. Oxidase testing is positive and carbohydrate degradation tests are inactive. What is the MOST likely identification?
Moraxella catarrhalis
The 48-hour growth of small pinpoint gray-white, smooth colonies on chocolate agar (right plate) are most commonly recovered as normal upper respiratory flora but may cause otitis media and sinusitis. There was no growth on Thayer Martin media (left plate). Growth on MacConkey agar is also absent. Short, plump, Gram negative cocci lying singly and in loose clusters are seen in Gram stain, as illustrated in the lower photomicrograph. This non-fermenter is non-motile, oxidase positive, and does not utilize carbohydrates (assacharolytic). Nitrates are reduced and DNAse is positive. From these observations, select from the multiple choices the presumptive identification of this isolate.
Moraxella catarrhalis
A patient shows signs of conjunctivitis including itching of the eyes, reddening of the conjunctiva, purulent secretion and lid edema. A culture was taken of the secretion and a Gram negative coccobacilli was seen on both the Sheep's blood and chocolate agars. There was no growth observed on the MacConkey agar. Additionally, the colonies were oxidase positive, catalase positive, reduced nitrate to nitrite, and liquefied gelatin. The identification of this organism is:
Moraxella lacunata
Growing on the surface of the anaerobic blood agar plate illustrated in the upper image are indistinct small, gray, convex, translucent colonies free of beta hemolysis. Gram negative cocci lying singly and in clusters are seen on Gram stain, as illustrated in the lower photomicrograph. Nitrates are reduced, indole is negative, and carbohydrates are not utilized (asaccharolytic). This isolate being part of the microbiota of the mouth, upper respiratory tract and intestine. What is this organism?
Veillonella parvula
Which organism is associated with sinusitis and otitis and is also considered a leading cause of meningitis with or without bacteremia?
Streptococcus pneumoniae
A nasopharyngeal specimen is processed and fixed onto a microscope slide. Next, fluorescein-conjugated antibody is added to the slide. The specimen is incubated with the labeled antibody, washed, and then observed for fluorescence. Which of the following techniques best describes this process?
Direct immunofluorescence
Which one of the following organisms is sensitive to bacitracin:
Group A Streptococcus
Which two of the following tests are helpful for documenting previous streptococcal throat and skin infections?
ASO titer & anti-DNase B
The colonies illustrated in the upper photograph were recovered from the aspiration of nasal secretion from a patient with acute sinusitis. The 48 hour colonies on blood agar are relatively small, entire, white, and non-hemolytic. Colonies growing on chocolate agar are also small, smooth and entire with a light yellow pigmentation. On Gram stain, pale-staining, Gram negative coccobacilli are observed, with a tendency to form long, narrow filaments. The lower photograph reveals tube reactions with a KIA: Acid/Acid and the oxidative utilization of several carbohydrates except xylose and mannose. Nitrate reduction is positive and ornithine and arginine decarboxylases are negative. From the observations, select from the multiple choices the genus/species name of this isolate.
Aggregatibacter aphrophilus
In patients who present with a classic "strep throat", the beta-hemolytic, catalase negative, Gram positive bacillus that must be included in the differential diagnosis is:
Arcanobacterium haemolyticum
The colonies growing on the surface of this 5% sheep blood agar plate, with ß-hemolysis, were recovered from a throat swab of a 19-year-old girl with acute pharyngitis. Gram stain revealed club-shaped Gram positive bacilli with rudimentary branching. What is this species?
Arcanobacterium hemolyticum
Which of the following is a presumptive test for the identification of Lancefield group A Streptococcus:
Bacitracin susceptibility
All of the following are usually associated with Group A Beta Streptococci, EXCEPT?
Bacteremia
A beta-hemolytic Streptococcus was isolated from a throat culture. It gave the following biochemical reactions: Bacitracin - Susceptible Bile esculin - Negative 6.5% NaCl - No growth CAMP - Negative SXT - Resistant What is the presumptive identification?
Beta hemolytic Streptococcus, Group A
An uncommon laboratory isolate, the colonies on blood agar, as seen in the top upper frame of the composite image were cultured from the throat swab of a 10 year old girl presenting with a red throat and mucosal pseudomembrane. These tiny gray-white, non hemolytic colonies are non-descriptive. Distinctive are the black pigmented colonies as observed on Tinsdale agar (lower image in the top composite photograph). Illustrated in the lower composite photomicrograph (upper image) are slender gram positive bacilli. Bacilli with meta-chromatic granules are observed in a methylene blue stained microscopic mount (lower image). From these observations, select from the multiple choices the presumptive identification of this isolate
Corynebacterium diphtheriae
This micrograph is most consistent with the cell morphology of:
Corynebacterium diphtheriae
Which one of the following organisms is commonly cultured from the nasopharynx of healthy people but is RARELY pathogenic?
Corynebacterium species
The diagnosis of diphtheria must be confirmed by:
Determining that a culture isolate is a toxin producing strain
The colonies illustrated on the blood and chocolate agar plates represent a slow-growing bacterial species that is endogenous in the oral cavity and upper respiratory tract. It may be recovered from human bite skin infections incurred during fist fights. Note the pitting of the agar surrounding the colonies growing in the chocolate agar plate. The Alk/Alk non fermentative reaction seen in the Kligler Iron Agar tube to the left in the lower photograph indicates the non-fermentation of glucose, also indicated by the lack of carbohydrate assimilation in the individual carbohydrate reaction tubes to the right of the KIA tube. A reduction of nitrate is seen and decarboxylation of ornithine is also positive. Based on these observations, select from the multiple choices listed the correct identification of this bacterial isolate:
Eikenella corrodens
Loeffler's medium is useful in making the presumptive identification of isolates suspicious for Corynebacterium diphtheriae recovered from oropharyngeal cultures because it:
Enhances granule formation as seen in methylene blue stains
The colonies illustrated in the top photograph are 48-hour-old colonies growing on the surface of blood agar that had been incubated anaerobically. The colonies are small, gray-white and convex with irregular borders and internal flecking. Long, slender fusiform Gram negative bacilli with tapered ends are seen in the Gram stain as observed in the bottom photomicrograph. The indole reaction is strongly positive and glucose fermentation is variable; other biochemical reactions are negative except for H2S production by some strains. This isolate is commensal in the upper respiratory tract and has been associated with hospital acquired aspiration pneumonia, lung abscesses, and empyema in hospitalized patients. Based on these observations, select from the multiple choices the name of this isolate.
Fusobacterium nucleatum
Procedures that may enhance the recovery of Streptococcus pyogenes from throat cultures include:
Incorporation of sulfamethoxazole and trimethoprim in the culture media
A gram-negative diplococcus is isolated from a throat culture. The isolate grows on Thayer-Martin agar, produces acid from maltose, lactose, and glucose and is ONPG positive. What is the most likely identification of this isolate?
Neisseria lactamica
Some strains of Group F Strep can carry the group A antigen, potentially leading to a false positive identification of group A, Streptococcus pyogenes. A spot test that is helpful in differentiating these two species and thus preventing a false report is:
Pyrrolidonyl-b-naphthylamide (PYR)
What virulence factor is not inherent to bacterium?
Production of opsonins
What bacterial species is rarely part of normal microbiota of healthy humans?
Pseudomonas aeruginosa
On sheep blood agar, Haemophilus influenzae may exhibit satellitism around all of the following bacteria, EXCEPT:
Pseudomonas spp.
All of the following are usually associated with Group A Beta Strep, EXCEPT?
Scalded Skin Syndrome
The photograph on the right is of a 5% sheep blood agar plate inoculated with a throat culture. It is common practice to stab the agar with the inoculating needle, as seen at the tip of the arrow, in order to detect or accentuate the reaction of:
Streptolysin O
