Chapter 14: Staphylococci. All Answers

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MULTIPLE CHOICE 1. Staphylococci are catalase-positive, gram-positive cocci that resemble other bacteria that are members of what family? a. Micrococcaceae b. Streptococcus c. Escherichia d. E... nterococcus A Micrococcaceae includes Planococcus, Stomatococcus, and Micrococcus, which are all catalase-positive, gram-positive cocci. These are found in the environment and can be normal skin flora. REF: 315 OBJ: Level 2: Interpretation 2. All of the following staphylococci are coagulase-positive except: a. Staphylococcus aureus. b. S. saprophyticus. c. S. intermedius. d. S. delphini. B The staphylocoagulase-producing (coagulase-positive) staphylococci are S. aureus, S. intermedius, S. delphini, S. lutrae, and some strains of S. hyicus. REF: 316 OBJ: Level 1: Recall 3. The two most common species of coagulase-negative staphylococci are: a. Staphylococcus aureus and S. epidermidis. b. S. capitus and S. lugdunensis. c. S. epidermidis and S. saprophyticus. d. S. saccharolyticus and S. epidermidis. C Currently, approximately 35 recognized species of coagulase-negative staphylococci exist. The most clinically significant species in this group are S. epidermidis and S. saprophyticus. REF: 316 OBJ: Level 1: Recall 4. All of the following virulence factors are associated with Staphylococcus aureus except: a. enterotoxins. b. cytolytic toxins. c. cellular components such as protein A. d. endotoxins. D The pathogenicity associated with S. aureus can be attributed to a number of virulence factors, such as enterotoxins, cytolytic toxins, and cellular components such as protein A. Five cytolytic toxins and two exfoliative toxins have been identified. REF: 316 OBJ: Level 1: Recall 5. What are the staphylococcal products that cause diarrhea and vomiting in humans? a. Enterotoxins b. Endotoxins c. Cytolytic toxins d. Cellular components, such as protein A A Staphylococcal enterotoxins are heat-stable exotoxins that cause diarrhea and vomiting in humans. Eight serologically distinct enterotoxins (A-E and G-I) have been identified. REF: 317 OBJ: Level 2: Interpretation 6. Staphylococcal enterotoxin B is linked to: a. carbuncles. b. staphylococcal pseudomembranous enterocolitis. c. food poisoning. d. toxic shock syndrome. B Enterotoxin B has been linked to staphylococcal pseudomembranous enterocolitis, although the mechanism is not understood. REF: 317 OBJ: Level 1: Recall 7. What is the mechanism by which toxic shock syndrome toxin-1 (TSST-1) causes toxic shock syndrome (TSS)? a. The bacteria release the toxin into the blood and it goes to the hypothalamus to produce an extremely high fever. b. The bacteria release the toxin into the gastrointestinal system where phagocytes engulf the bacteria, leaving a pseudomembrane that irritates the colon. c. The toxin is a superantigen that stimulates T-cell proliferation with production of large amounts of cytokines. d. All of the above. C TSST-1 is a superantigen stimulating T-cell proliferation and the subsequent production of a large concentration of cytokines that are responsible for the symptoms. At low concentration, TSST-1 causes leakage by endothelial cells, and at higher concentration, it is cytotoxic to these cells. TSST-1 is absorbed through vaginal mucosa, permitting the systemic effects seen in TSS. REF: 317 OBJ: Level 2: Interpretation 8. What are the effects of the -hemolysin produced by Staphylococcus aureus? a. It acts on sphingomyelin in the plasma membrane of red blood cells. b. It kills polymorphonuclear leukocytes. c. It kills macrophages. d. It lyses red blood cells, damages platelets and macrophages, and can cause severe tissue damage. D -Hemolysin, in addition to lysing erythrocytes, can damage platelets and macrophages, and cause severe tissue damage. REF: 317 OBJ: Level 1: Recall 9. What are the effects of the -hemolysin produced by Staphylococcus aureus? a. It acts on sphingomyelin in the plasma membrane of red blood cells. b. It kills polymorphonuclear leukocytes. c. It kills macrophages. d. It lyses red blood cells, damages platelets and macrophages, and can cause severe tissue damage. A -Hemolysin (sphingomyelinase C) acts on sphingomyelin in the plasma membrane of the erythrocytes and is also called the “hot-cold” lysine. This hemolysin is exhibited in the CAMP test performed in the laboratory to identify group B streptococci. REF: 317 OBJ: Level 1: Recall 10. What are the effects of the Panton-Valentine toxin produced by Staphylococcus aureus? a. It acts on sphingomyelin in the plasma membrane of red blood cells. b. It kills polymorphonuclear leukocytes. c. It kills macrophages. d. It lyses red blood cells, damages platelets and macrophages, and can cause severe tissue damage. B Staphylococcal leukocidin, periventricular leukomalacia (PVL), is an exotoxin lethal to polymorphonuclear leukocytes. It has been implicated as contributing to the invasiveness of the organism by suppressing phagocytosis and has been associated with severe cutaneous infections and necrotizing pneumonia. Although produced by relatively few strains of Staphylococcus aureus, it has been associated with some cases of community-acquired staphylococcal infections. REF: 317 OBJ: Level 1: Recall 11. All of the following enzymes are produced by staphylococci except: a. lipase. b. hyaluronidase. c. amylase. d. protease. C Several enzymes are produced by staphylococci. Examples are coagulase, protease, hyaluronidase, and lipase. REF: 317 OBJ: Level 1: Recall 12. How do staphylococci spread so easily when infecting the skin? a. They produce hyaluronidase, which hydrolyzes hyaluronic acid present in the intracellular ground substance that makes up connective tissue. b. They produce lipase, which melts the fat under the skin, making it easier to spread. c. The hemolysins kill the white and red blood cells; then the protease liquefies the skin protein, allowing easy penetration for the bacteria. d. All of the above. A This enzyme hydrolyzes hyaluronic acid present in the intracellular ground substance that makes up connective tissues, permitting the easy spread of bacteria during infection. REF: 317 OBJ: Level 2: Interpretation 13. What is the function of protein A in the cell wall of Staphylococcus aureus? a. To keep the structural integrity of the cell wall and keep out antibiotics b. To bind the IgG and prevent phagocytosis c. To bind the IgM and inactivate natural killer cells d. To block the activation of the complement cascade B Protein A is one of several cellular components that have been identified in the cell wall of S. aureus. Probably the most significant role of protein A in infections caused by S. aureus is its ability to bind the Fc portion of IgG. Binding IgG in this manner can block phagocytosis. REF: 317 OBJ: Level 1: Recall 14. The primary reservoir for staphylococci is: a. ears. b. mouth. c. nares. d. throat. C The primary reservoir for staphylococci is the nares, with colonization also occurring in the axillae, vagina, pharynx, and other skin surfaces. Nasal carriage in patients admitted to the hospital is common. Because close contact among patients and hospital personnel is not unusual, transfer of organisms often takes place. REF: 317 OBJ: Level 1: Recall 15. The development of staphylococcal infection is determined by: a. virulence of the strain. b. size of the inoculum. c. status of host’s immune system. d. all of the above. D As with most infections, the development of staphylococcal infection is determined by the virulence of the strain, size of the inoculum, and status of the host’s immune system. Infections are initiated when a breach of the skin or mucosal barrier allows staphylococci access to adjoining tissues or the bloodstream. REF: 317 OBJ: Level 1: Recall 16. Staphylococci resist the action of inflammatory cells by the production of toxins and enzymes, thereby establishing: a. a focal lesion. b. an infection. c. toxic shock syndrome. d. scalded skin syndrome. A The organisms are able to resist the action of inflammatory cells, by the production of toxins and enzymes, thereby establishing a focal lesion. REF: 317 OBJ: Level 2: Interpretation 17. Infections caused by Staphylococcus aureus are suppurative, meaning: a. these infections ooze lymph fluid. b. the infection is filled with pus and necrotic tissues. c. the acute inflammatory response gorges the area with red blood cells. d. the toxins activate the coagulation system, which isolates the infection. B Infections caused by S. aureus are suppurative. Typically the abscess is filled with pus and surrounded by necrotic tissues and damaged leukocytes. REF: 317 OBJ: Level 1: Recall 18. What disease is an extensive exfoliative dermatitis caused by staphylococcal exfoliative toxin? a. Bullous impetigo b. Folliculitis c. Ritter’s disease d. Toxic shock syndrome C Scalded skin syndrome, or Ritter’s disease, is an extensive exfoliative dermatitis that occurs primarily in newborns and previously healthy young children. This syndrome is caused by staphylococcal exfoliative or epidermolytic toxin produced by Staphylococcus aureus phage group II, probably present at a lesion distant from the site of exfoliation. REF: 318 OBJ: Level 1: Recall 19. What is a rare but potentially fatal multisystem disease characterized by high fever, hypotension, and shock, and it is associated with highly absorbent tampons? a. Toxic epidermal necrolysis b. Scalded skin syndrome c. Bullous impetigo d. Toxic shock syndrome D Toxic shock syndrome is a rare but potentially fatal multisystem disease characterized by high fever, hypotension, and shock. It was first described by Todd in 1978 and was associated with highly absorbent tampon use, although some cases did appear in men, children, and nonmenstruating women. REF: 318 OBJ: Level 2: Interpretation 20. Staphylococcus aureus food poisoning is most commonly caused by which two enterotoxins? a. A and D b. A and B c. B and C d. B and D A S. aureus enterotoxins, most commonly A and D, have been identified and associated with gastrointestinal disturbances. The source of contamination is usually an infected food handler. Staphylococcal food poisoning is a type of intoxication, resulting from the ingestion of a preformed toxin. REF: 318 OBJ: Level 1: Recall 21. What infection occurs secondary to influenza A virus, has a high mortality rate, and occurs among the infants and immunocompromised patients? a. Gangrene b. Staphylococcal pneumoniae c. Staphylococcal meningitis d. Staphylococcal peritonitis B Staphylococcal pneumonia has been known to occur secondary to an influenza A virus infection. Although rare, staphylococcal pneumonia has a high mortality rate. The pneumonia, which develops as either a contiguous lower respiratory tract infection or a complication of bacteremia, is characterized by multiple abscesses and focal lesions in the pulmonary parenchyma. Infants and immunocompromised patients, such as the elderly and patients receiving chemotherapy or immunosuppressants, are most affected. REF: 319 OBJ: Level 2: Interpretation 22. Infections by which organism are predominantly hospital acquired, and some predisposing factors include catheterization, medical implantation, and immunosuppressive therapy? a. Staphylococcus aureus b. S. intermedius c. S. epidermidis d. S. saprophyticus C The role of S. epidermidis as an etiologic agent of disease has become increasingly evident. Infections caused by S. epidermidis are predominantly hospital acquired. Some of the predisposing factors are instrumentation procedures, such as catheterization, medical implantation, and immunosuppressive therapy. S. epidermidis is probably the most common cause of hospital-acquired urinary tract infections. REF: 319 OBJ: Level 2: Interpretation 23. Which staphylococcal species is associated with urinary tract infections in young, sexually active females? a. Staphylococcus aureus b. S. intermedius c. S. epidermidis d. S. saprophyticus D S. saprophyticus has been associated with urinary tract infections in young, sexually active females. This species is found to adhere more effectively to the epithelial cells lining the urogenital tract than other coagulase-negative staphylococci. REF: 319 OBJ: Level 2: Interpretation 24. Colony characteristics for Staphylococcus aureus on blood agar after 18 to 24 hours incubation at 35° C include all the following except: a. swarming. b. smooth. c. white. d. round. A Staphylococci produce round, smooth, white, creamy colonies on blood agar after 18 to 24 hours of incubation at 35° C. REF: 320 OBJ: Level 1: Recall 25. Which staphylococcus produces wide zones of beta hemolysis on 5% sheep blood agar? a. Staphylococcus epidermidis b. S. aureus c. S. intermedius d. S. saprophyticus B S. aureus may produce hemolytic zones around the colonies and may exhibit pigment production (yellow) with extended incubation. REF: 320 OBJ: Level 2: Interpretation 26. All of the following is used to describe the colonial morphology of Staphylococcus epidermidis except: a. -hemolytic. b. -hemolytic. c. white. d. small to medium. A S. epidermidis colonies are usually small- to medium-size, nonhemolytic, white colonies. REF: 320 OBJ: Level 2: Interpretation 27. What tests are used to detect clumping factor that differentiates Staphylococcus aureus from other staphylococcal species? a. Novobiocin and hemolysin A b. Coagulase and latex agglutination c. Complement fixation and coagulase d. Latex agglutination and enzyme immunoassay (EIA) B S. aureus is often identified by the coagulase tests. Clumping factor, formerly referred to as cell-bound coagulase, causes agglutination in human, rabbit, or pig plasma and is considered a major marker for S. aureus. Clumping factor on the surface of the bacterial cells directly converts fibrinogen to fibrin, which precipitates onto the cell surface, causing agglutination. REF: 321 OBJ: Level 1: Recall 28. How is Staphylococcus saprophyticus presumptively identified? a. Latex agglutination test for clumping factor b. Rabbit plasma test for coagulase c. Novobiocin susceptibility d. All of the above C Presumptive identification of S. saprophyticus is accomplished by testing for novobiocin susceptibility using a 5 g novobiocin disk. S. saprophyticus is resistant to novobiocin, but most other coagulase-negative staphylococci are susceptible. REF: 323 OBJ: Level 1: Recall 29. What antibiotic is used for detection of methicillin resistance? a. Penicillin b. Methicillin c. Erythromycin d. Oxacillin D For laboratory purposes, oxacillin is generally used for detection of methicillin resistance. For coagulase-negative staphylococci, the Clinical and Laboratory Standards Institute (CLSI) recommends a cefoxitin disk be used as the preferred method of detecting methicillin resistance. REF: 324 OBJ: Level 1: Recall 30. Automated antimicrobial susceptibility testing methods are not reliable in detecting these resistant staphylococci. What antibiotic are the bacteria resistant to? a. Vancomycin b. Erythromycin c. Clindamycin d. All of the above A Automated antimicrobial susceptibility testing methods are not reliable in detecting these isolates. Screening using a vancomycin agar plate as described by the Clinical and Laboratory Standards Institute (CLSI) performance guidelines should enhance detection of vancomycin-intermediate Staphylococcus aureus (VISA) and vancomycin-resistant Staphylococcus aureus (VRSA). Detection of these isolates should be confirmed by a reference method or laboratory, and reporting should follow Centers for Disease Control and Prevention (CDC) guidelines. REF: 325 OBJ: Level 1: Recall 31. A woman in her 20s goes to her physician complaining of burning upon urination, frequency, and general malaise. Her physician does a urine culture, and it grows out 25,000 colony-forming units (CFU)/mL of a catalase-positive, coagulase-negative, novobiocin-resistant gram-positive cocci. What is the most likely pathogen? a. Staphylococcus epidermidis b. S. haemolyticus c. S. intermedius d. S. saprophyticus D S. saprophyticus is a cause of urinary tract infections in young sexually active women. It is a catalase-positive, coagulase-negative, and novobiocin-resistant gram-positive cocci. REF: 316 OBJ: Level 3: Synthesis 32. A young man goes to his physician complaining of large, raised, suppurative abscesses on his neck. The man denies having a fever or the chills. What is the name of the lesions on his neck, and what organism causes this type of lesions? a. Staphylococcus epidermidis and boils b. S. aureus and furuncles c. S. saprophyticus and carbuncles d. S. sciuri and folliculitis B Some of the common skin infections caused by S. aureus are folliculitis, furuncles, carbuncles, and bullous impetigo. Furuncles (boils), which can be an extension of folliculitis, are large, raised, superficial abscesses. Carbuncles occur when larger, more invasive lesions develop from multiple furuncles, which may progress into deeper tissues. Unlike furuncles, patients with carbuncles often have fever and chills, indicating systemic spread of bacteria. REF: 317 OBJ: Level 3: Synthesis 33. A young, healthy woman was rushed to the hospital with a high fever, hypotension, and shock. She had not been feeling well that day, but her condition progressively worsened throughout the day. She was feeling fine until a couple days after she started menstruating. What condition could this woman be exhibiting? a. Scalded skin syndrome b. Toxic epidermal necrolysis c. Toxic shock syndrome d. Food poisoning C Toxic shock syndrome is a rare but potentially fatal multisystem disease characterized by high fever, hypotension, and shock. It was first described by Todd in 1978 and was associated with highly absorbent tampon use, although some cases did appear in men, children, and nonmenstruating women. REF: 318 OBJ: Level 3: Synthesis 34. Later in the evening, after attending a family reunion, several family members went to the emergency department after experiencing nausea, vomiting, abdominal pain, and severe cramping. When questioned about the food at the family reunion, the menu included fried chicken, hot dogs, hamburgers, potato salad, deviled eggs, éclairs, and cheesecake. The symptoms appeared about 4 hours after they ate. What is the most probable explanation for these symptoms? a. Staphylococcal food poisoning b. Toxic shock syndrome c. Toxic epidermal necrolysis d. Scalded skin syndrome A Staphylococcus aureus enterotoxins, most commonly A and D, have been identified and associated with gastrointestinal disturbances. Foods that are often incriminated in staphylococcal food poisoning include salads, especially those containing mayonnaise and eggs, meat or eggs, meat products, poultry, egg products, bakery products with cream fillings, sandwich fillings, and dairy products. Symptoms appear rapidly, approximately 2 to 8 hours after ingestion of the food and resolve within 24 to 48 hours. Although no fever is associated with this condition, nausea, vomiting, abdominal pain, and severe cramping are common. REF: 319 OBJ: Level 3: Synthesis [Show More]

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