Deck 18: Principles and Applications of Maldi-Tof Mass Spectrometry for the Rapid Identification of Bacteria and Fungi

Question 1

Differentiate the microscopic morphology of staphylococci and streptococci as seen by Gram stain.

Answer 1

Staphylococci are gram positive cocci (round in shape). These cocci are arranged in irregular clusters like grapes. Streptococci are also gram positive cooci but arranged in chains.
Thus, both Staphylococci and Streptococci are gram positive in nature but they differ in the arrangement of their cocci.

Question 2

Community-Acquired Methicilin-Resistant Staphylococcus
The following case reported by the Centers for Disease Control and Prevention. They illustrate the emerging problem of community-acquired methicillin-resistant Staphylococcus aureus , as well as clinical and laboratory features of staphylococcal infection.
A 16-month-old girl was brought to a local hospital with fever, hemoptysis (bloody sputum), and respiratory distress. The day before admission, she had a productive cough and a 2-cm papule on her lower lip. A chest X-ray showed infiltrates in the left lower lobe of her lung and a pleural effusion (fluid in the pleural space). She was treated with a cephalosporin-type antimicrobial and a methicillin-type antimicrobial. Shortly after arriving at the hospital, her blood pressure dropped, and she was intubated and treated with vancomycin. Despite supportive efforts, she died after 7 days from progressive cerebral edema (brain swelling) and multiorgan failure. The patient's blood, sputum, and pleural fluid grew MRSA that was multidrug susceptible.
What two tests could the laboratory have used to identify these isolates as Staphylococcus aureus ?

Answer 2

To identify the isolates as S.aureus , the technicians can grow the organism on blood agar. On blood agar, it produces light to golden yellow pigment liberating beta-hemolytic colonies.
The presence of S.aureus in the isolates can be confirmed by performing coagulase and mannitol fermentation tests. S.aureus will be coagulase positive and also ferments mannitol.
Thus, the laboratory could have used coagulase test and mannitol fermentation test to identify the isolates as S.aureus.

Question 3

What are the two types of staphylococcal coagulase?

Answer 3

The coagulase positive Staphylococci will produce two types of coagulase enzyme. One is bound form and the other is free from.
The bound coagulase acts directly on fribrogen to give fibrin. The free coagulase acts on prothrombin to give thrombin-like product.

Question 4

Community-Acquired Methicilin-Resistant Staphylococcus
The following case reported by the Centers for Disease Control and Prevention. They illustrate the emerging problem of community-acquired methicillin-resistant Staphylococcus aureus , as well as clinical and laboratory features of staphylococcal infection.
A 16-month-old girl was brought to a local hospital with fever, hemoptysis (bloody sputum), and respiratory distress. The day before admission, she had a productive cough and a 2-cm papule on her lower lip. A chest X-ray showed infiltrates in the left lower lobe of her lung and a pleural effusion (fluid in the pleural space). She was treated with a cephalosporin-type antimicrobial and a methicillin-type antimicrobial. Shortly after arriving at the hospital, her blood pressure dropped, and she was intubated and treated with vancomycin. Despite supportive efforts, she died after 7 days from progressive cerebral edema (brain swelling) and multiorgan failure. The patient's blood, sputum, and pleural fluid grew MRSA that was multidrug susceptible.
What antibiotic susceptibility pattern separates these isolates from MRSA isolated from hospitalized patients?

Question 5

What is protein A? Describe one method for detecting it.

Question 6

Community-Acquired Methicilin-Resistant Staphylococcus
The following case reported by the Centers for Disease Control and Prevention. They illustrate the emerging problem of community-acquired methicillin-resistant Staphylococcus aureus , as well as clinical and laboratory features of staphylococcal infection.
A 16-month-old girl was brought to a local hospital with fever, hemoptysis (bloody sputum), and respiratory distress. The day before admission, she had a productive cough and a 2-cm papule on her lower lip. A chest X-ray showed infiltrates in the left lower lobe of her lung and a pleural effusion (fluid in the pleural space). She was treated with a cephalosporin-type antimicrobial and a methicillin-type antimicrobial. Shortly after arriving at the hospital, her blood pressure dropped, and she was intubated and treated with vancomycin. Despite supportive efforts, she died after 7 days from progressive cerebral edema (brain swelling) and multiorgan failure. The patient's blood, sputum, and pleural fluid grew MRSA that was multidrug susceptible.
What precautions did hospital personnel need to take to prevent transmission of these strains to other hospitalized patients?

Question 7

What properties of S. aureus distinguish it from S. epidermidis and S. saprophyticus?

Question 8

How is S. saprophyticus distinguished from S. epidermidis?

Question 9

From what specimen type would S. saprophyticus most likely be isolated?

Question 10

What is a nosocomial infection? Who acquires it? Why?

Question 11

Why are staphylococcal infections frequent among hospital patients?

Question 12

Discuss the role played by S. aureus in human infectious diseases.

Question 13

Community-Acquired Methicilin-Resistant Staphylococcus
The following case reported by the Centers for Disease Control and Prevention. They illustrate the emerging problem of community-acquired methicillin-resistant Staphylococcus aureus , as well as clinical and laboratory features of staphylococcal infection.
A 16-month-old girl was brought to a local hospital with fever, hemoptysis (bloody sputum), and respiratory distress. The day before admission, she had a productive cough and a 2-cm papule on her lower lip. A chest X-ray showed infiltrates in the left lower lobe of her lung and a pleural effusion (fluid in the pleural space). She was treated with a cephalosporin-type antimicrobial and a methicillin-type antimicrobial. Shortly after arriving at the hospital, her blood pressure dropped, and she was intubated and treated with vancomycin. Despite supportive efforts, she died after 7 days from progressive cerebral edema (brain swelling) and multiorgan failure. The patient's blood, sputum, and pleural fluid grew MRSA that was multidrug susceptible.
What was the likely source of the original Staphylococcus infection in each patient?