Blood & Bone Marrow (Microbiology) Flashcards
Three sets of blood cultures were obtained from an adult patient with fever and suspected endocarditis. The aerobic bottle of one set had growth of Staphylococcus epidermidis at 5 days of incubation. This indicates that:
A) there was low grade bacteremia
B) the organisms is most likely a contaminant
C) the patient has a line infection
D) the blood culture bottles are defective
B) the organisms is most likely a contaminant
The Gram stain from a blood culture shows gram-positive cocci in chains. The subculture plates from the blood culture bottle show no growth. Additional testing should be done to detect the presence of:
A) Staphylococcus saprophyticus
B) Aerococcus urinae
C) Abiotrophia defectiva
D) Streptococcus pneumoniae
C) Abiotrophia defectiva
Gram stain examination from a blood culture bottle shows dark blue, spherical organisms in clusters, Growth on sheep blood agar shows small, round, pale yellow colonies. Further tests should include:
A) catalase production and agglutination test for protein A
B) bacitracin susceptibility and latex grouping
C) oxidase and indole reactions
D) Voges-Proskauer and methyl red reactions
A) catalase production and agglutination test for protein A
Gram-positive cocci in chains are seen on a Gram stain from a blood culture. The organism grows as a beta-hemolytic colony. Further tests that could be performed include:
A) PYR, bacitracin, and hippurate
B) catalase and agglutination tests for Protein A
C) oxidase and mass spectrometry
D) Voges-Proskauer and methyl red
A) PYR, bacitracin, and hippurate
“Nutritionally variant” streptococci are:
A) enterococci
B) group D enterococci
C) beta hemolytic streptococci
D) in the genera Granulicatella and Abiotrophia
D) in the genera Granulicatella and Abiotrophia
The most frequent cause of prosthetic heart valve infections occurring within 2-3 months after surgery is:
A) streptococcus pneumoniae
B) Streptococcus pyongenes
C) Staphylococcus aureus
D) Staphylococcus epidermidis
D) Staphylococcus epidermidis
Gram-positive cocci isolated form a blood culture have the following characteristics:
optochin susceptibility: negative
bacitracin susceptibility: negative
bile esculin hydrolysis: negative
hippurate hydrolysis: positive
catalase: negative
This organism is most likely:
A) Staphylococcus aureus
B) Streptococcus pneumoniae
C) streptococcus pyogenes
D) Streptococcus agalactiae
D) Streptococcus agalactiae
During the previous month, Staphylococcus epidermidis has been isolated from blood cultures at 2-3 times the rate from the previous year. The most logical explanation for the increase in these isolates is that:
A) the blood culture media that are contaminated with this organism
B) the hospital ventilation system is contaminated with Staphylococcus epidermidis
C) there has been a break in proper skin preparation before drawing blood for culture
D) a relatively virulent isolate is being spread from patient to patient
C) there has been a break in proper skin preparation before drawing blood for culture
A 55 year old man presents to the emergency room with chest pain and is found to have suffered a heart attack. He has a past history of hypertension, and high cholesterol. The patient is admitted and scheduled for a triple bypass procedure. During recovery, he becomes septic, developing a high grade fever and pneumonia. Gram-positive cocci in clusters, isolated from both his lungs via an induced sputum specimen and the surgical incision, produce beta-hemolytic, catalase-positive colonies on sheep blood agar.
Identify the organism most likely isolated and the biochemical test performed to confirm the identification.
A) Stapylococcus aureus and latex agglutination
B) Streptococcus pyogenes and PYR
C) Streptococcus agalactiea and latex agglutination
D) Enterococcus faecium and PYR
A) Stapylococcus aureus and latex agglutination
A patient with a prosthetic heart valve visits the dentist for her yearly checkup. Two weeks, later, she presents to her primary care physician wit a high fever, chills, and shortness of breath and receives a diagnosis of subacute endocarditis. Multiple blood culture sets are drawn on the patient and sent to the lab. 24 hrs later the bottles are positive for bacterial growth. Which organisms would you expect to grow?
A) Staphylococcus lugdenensis
B) Staphylococcus saprophyticus
C) Streptococcus viridans
D) Streptococcus agalactiae
C) Streptococcus viridans
A blood culture from a 64 year old male with lymphoma was positive blood culture at 18 hrs incubation. The organisms are nonlactose fermenting gram-negative bacilli on MacConkey agar. Further testing gives the following reactions:
oxidase: neg
TSI: alkaline/acid, no hydrogen sulfide
motility: pos
indole: pos
citrate: pos
ornithine decarboxylase: neg
urea: pos
phenylalanine deaminase: pos
VP: negative
The genus is:
A) Morganella
B) Proteus
C) Providencia
D) Serratia
C) Providencia
A blood culture bottle with macroscopic signs of growth is Gram stained and the technician notes small, curved gram-negative bacilli resembling “gull wings”. It is subcultured to blood and chocolate agar, and incubated aerobically and anaerobically. After 24 hrs, no growth is apparent. The next step should be to:
A) subculture the bottle, and incubate the microaerophilic conditions
B) assume the organism is nonviable, and ask for repeat specimen
C) utilize the oxidase and indole test to detect Aeromonas
D) subculture the bottle to a medium containing X and V factors
A) subculture the bottle, and incubate the microaerophilic conditions
Which of the following specimens is considered to be the most sensitive for the recovery of Brucella in cases of chronic infections?
A) blood
B) urine
C) bone marrow
D) lymph node
C) bone marrow
A college student attended a beach party where raw oysters and other shelfish were consumed. The next day, he had symptoms of septicemia. The blood cultures grew gram-negative bacilli with the following characteristics:
oxidase: pos
MacConkey agar: pink colonies
O/129: susceptible
The most likely organism is:
A) Aeromonas hydrophila
B) Pseudomonas putida
C) Serratia marcescens
D) Vibrio Vulnificus
D) Vibrio Vulnificus
The laboratory receives a blood culture from a veterinarian who has been ill for many weeks with fevers in the afternoon and evenings, arthritis, and fatigue. the blood culture is positive after 5 days, and the organism has the following characteristics:
Gram Stain: small, gram-negative coccobacilli
Sheep Blood Agar: growth after 24 hrs with small, smooth, raised colonies
What should the microbiologist do next?
A) consider the growth contamination and perform another Gram stain
B) perform biochemical identification for HACEK organisms
C) perform identification and susceptibility testing using an automated system
D) take extra safety precautions for possible Brucella
D) take extra safety precautions for possible Brucella
