Chapter 15: Streptococcus, Enterococcus, and Other Catalase-Negative, Gram-Positive Cocci. All Answers

MULTIPLE CHOICE 1. What test differentiates staphylococci from streptococci? a. Catalase b. Coagulase c. -Hemolysis d. All of the above A Streptococcus and Enterococcus belong to the family Streptococcace ...

MULTIPLE CHOICE 1. What test differentiates staphylococci from streptococci? a. Catalase b. Coagulase c. -Hemolysis d. All of the above A Streptococcus and Enterococcus belong to the family Streptococcaceae. Members of both genera are catalase-negative, gram-positive cocci that are usually arranged in pairs or chains. The negative catalase test result differentiates the streptococci and enterococci from staphylococci. REF: 329 OBJ: Level 1: Recall 2. The atmospheric conditions best suited to grow streptococci and enterococci are: a. room air. b. oxygen-free atmosphere. c. high carbon dioxide concentration. d. low carbon dioxide concentration. B Most members of the genera Streptococcus and Enterococcus behave as facultative anaerobes. Because they grow in the presence of oxygen but are unable to use oxygen for respiration, they may be considered aerotolerant anaerobes. REF: 329 OBJ: Level 1: Recall 3. What is the cell wall made of in streptococci and enterococci? a. Lipopolysaccharide and carbohydrates b. Protein A and phospholipids c. Cholesterol and teichoic acid d. Teichoic acid and peptidoglycan D The streptococci possess a typical gram-positive cell wall consisting of peptidoglycan and teichoic acid. Most streptococci, except for many of the viridans group, have a layer of a group or common C carbohydrate (polysaccharide), which can be used to serologically classify an isolate. REF: 329 OBJ: Level 1: Recall 4. Common schemes to classify streptococci include all the following except: a. biochemical characteristics. b. serologic grouping or typing of C carbohydrate. c. physiologic characteristics. d. flagellar antigens. D Four commonly used classification schemes are hemolytic pattern on sheep red blood cell agar, physiologic characteristics, serologic grouping or typing of C carbohydrate (Lancefield classification), capsular polysaccharide, or surface protein, such as the M protein of Streptococcus pyogenes and biochemical characteristics. REF: 342 OBJ: Level 1: Recall 5. Physiologic classification of streptococci divide the species into all the following groups except: a. pyogenic streptococci. b. lactococci. c. -hemolytic streptococci. d. enterococci. C The physiologic classification divides the species into four groups: pyogenic streptococci, lactococci, enterococci, and viridans streptococci. The pyogenic streptococci are those that produce pus; these organisms are mostly -hemolytic and constitute the majority of the Lancefield groups. The lactococci, members of the genus Lactococcus, are nonhemolytic organisms with Lancefield group N antigens that often are found in dairy products. The enterococci comprise those species found as part of the normal flora of the human intestines; this group of organisms belongs to the genus Enterococcus. REF: 342 OBJ: Level 1: Recall 6. What is the inexpensive test used to presumptively identify Streptococcus pyogenes? a. Optochin b. Bacitracin c. Nitrate d. Citrate B Bacitracin susceptibility has historically been used as an inexpensive test to identify presumptively S. pyogenes. -hemolytic Streptococcus colonies are subcultured to a sheep blood agar (SBA) plate, and a filter paper disk impregnated with 0.04 units of bacitracin is added. The plate is incubated at 35 C overnight; any zone of inhibition is interpreted as sensitive and is a presumptive identification of group A Streptococcus. REF: 344 OBJ: Level 1: Recall 7. What is the name of the test presumptively used to identify group B streptococci? a. CAMP b. Lancefield c. Bacitracin d. Optochin A A Staphylococcus aureus streak is placed down the center of a sheep blood agar (SBA) plate. The unknown streptococcal isolate is inoculated perpendicularly to the S. aureus inoculum. The result is a characteristic arrowhead-shaped hemolysis pattern. REF: 345 OBJ: Level 1: Recall 8. What test can be used to differentiate Streptococcus agalactiae from other -hemolytic streptococci? a. Bacitracin b. Hippurate hydrolysis c. PYR d. Optochin B A useful test to differentiate S. agalactiae from other -hemolytic streptococci is hippurate hydrolysis. S. agalactiae possess the enzyme hippuricase, which hydrolyzes sodium hippurate to form sodium benzoate and glycine. Hydrolysis can be detected by adding Ninhydrin, which reacts with glycine to form a purple color. REF: 345 OBJ: Level 1: Recall 9. What test presumptively differentiates-hemolytic group A streptococci and nonhemolytic group D enterococci from other streptococcal species? a. Bacitracin b. Hippurate hydrolysis c. PYR d. Optochin C The PYR hydrolysis test provides a high probability for the presumptive differentiation of the -hemolytic group A streptococci and the nonhemolytic group D enterococci from the other streptococcal species. REF: 345 OBJ: Level 1: Recall 10. What two tests have been mainstays in identification schemes for the non–-hemolytic, catalase-negative, gram-positive cocci? a. Bacitracin and PYR b. Hippurate hydrolysis and optochin c. Nitrate and PYR d. Bile esculin and salt tolerance D Two tests that have been mainstays in identification schemes for the non–-hemolytic, catalase-negative, gram-positive cocci are the bile esculin hydrolysis test and the salt tolerance test. The bile esculin test is a two-step test; bacteria must grow in the presence of 40% bile and be able to hydrolyze esculin to produce a positive reaction. Growth in 6.5% sodium chloride broth is used to identify Enterococcus and Aerococcus. REF: 346 OBJ: Level 1: Recall 11. What test is used as a presumptive identification of Streptococcus pneumoniae? a. Optochin b. Bacitracin c. PYR d. Hippurate hydrolysis A In the optochin test, a filter paper disk containing optochin is added to the surface of an SBA plate that has just been inoculated with an -hemolytic streptococcus. The plate is incubated overnight at 35 C in a carbon dioxide incubator. A zone of inhibition greater than 14 mm with a 6-mm disk and a zone of inhibition greater than 16 mm with a 10-mm disk are considered susceptible and are a presumptive identification of S. pneumoniae. REF: 346 OBJ: Level 1: Recall 12. Most doctors’ offices use the rapid throat swab methods to identify Streptococcus pyogenes. If the test is positive, the physician treats the patient. What should happen if the test is negative? a. The physician should treat the patient to be safe. b. The physician should perform a throat culture. c. The physician should repeat the rapid strep tests. d. None of the above. B Although a positive finding allows the primary care provider to treat for S. pyogenes infections without waiting for culture results, a negative result necessitates a throat culture. This is because the sensitivity of direct detection methods for group A streptococci is not high enough to ensure that the negative result is not a false negative. REF: 347 OBJ: Level 2: Interpretation 13. Which of the following is the drug of choice for treating most streptococcal infections? a. Erythromycin b. Cephalothin c. Penicillin d. Gentamicin C Despite widespread use, penicillin is the drug of choice in treating most streptococcal infections. However, penicillin-resistant Streptococcus pneumoniae and viridans group isolates have been reported worldwide, and the incidence of penicillin-resistant S. pneumoniae seems to be increasing. REF: 347 OBJ: Level 1: Recall 14. What is the cellular structure that Streptococcus pyogenes relies on for its virulence? a. Peptidoglycan b. Lipopolysaccharide c. S antigens d. M proteins D S. pyogenes has a cell wall structure similar to that of other streptococci and gram-positive bacteria. An antigen that is not found in the other Lancefield groups is referred to as the M protein. This is a molecule attached to the peptidoglycan of the cell wall and extends to the cell surface. The M protein is essential to virulence. REF: 331 OBJ: Level 1: Recall 15. All of the following are additional virulence factors associated with group A Streptococcus except: a. enterotoxins. b. hemolysins. c. toxins. d. enzymes. A Fibronectin-binding protein, lipoteichoic acid, hyaluronic acid capsule, extracellular products including hemolysin, toxins, and enzymes are additional virulence factors associated with group A streptococci. REF: 331 OBJ: Level 1: Recall 16. What is the hemolysin responsible for hemolysis on SBA incubated anaerobically? a. Hyaluronidase b. Streptolysin O c. Streptolysin D d. Hemolysin O B A hemolysin responsible for hemolysis on SBA plates incubated anaerobically is streptolysin O. The O refers to the fact that this hemolysin is oxygen labile. REF: 331 OBJ: Level 1: Recall 17. What causes the red spreading rash in scarlet fever? a. Hyaluronidase b. Streptolysin O c. Streptococcal pyrogenic exotoxins d. Streptolysin S C Some strains of Streptococcus pyogenes cause a red spreading rash, referred to as scarlet fever, resulting from streptococcal pyrogenic exotoxins, formerly called erythrogenic toxins. REF: 332 OBJ: Level 1: Recall 18. Streptokinase is an enzyme produced by group A streptococci that: a. breaks down staphylococci. b. breaks down connective tissue. c. produces a maculopapular rash in rheumatic fever. d. lyses fibrin clots. D Filtrates of group A streptococci cause the lysis of fibrin clots, through the action of streptokinase on plasminogen. REF: 332 OBJ: Level 1: Recall 19. What is one of the most common diseases caused by streptococci? a. Strep throat b. Rheumatic fever c. Acute glomerulonephritis d. Scarlet fever A The most common clinical manifestations of group A streptococcal infection are pharyngitis and tonsillitis. The majority of cases of bacterial pharyngitis are due to Streptococcus pyogenes. Approximately one third of those complaining of sore throat have a throat culture positive for S. pyogenes. REF: 332 OBJ: Level 1: Recall 20. Skin or pyoderma infections with group A streptococci result in all the following syndromes except: a. impetigo. b. bullous impetigo. c. cellulitis. d. erysipelas. B Skin or pyoderma infections with group A streptococci result in the syndrome of impetigo, cellulitis, erysipelas, wound infection, or gangrene. REF: 332 OBJ: Level 1: Recall 21. What disease is produced by group A streptococci that is characterized by a rapidly progressing inflammation and necrosis of the skin, subcutaneous fat, and fascia? a. Erysipelas b. Scarlet fever c. Necrotizing fasciitis d. Streptococcal toxic shock syndrome C Group A streptococcus has been associated with necrotizing fasciitis, an invasive infection characterized by a rapidly progressing inflammation and necrosis of the skin, subcutaneous fat, and fascia. Although relatively uncommon, this bacterial infection is life threatening. REF: 332 OBJ: Level 2: Interpretation 22. Two serious complications of an infection with group A streptococcal disease are: a. toxic shock syndrome and scarlet fever. b. gangrene and rheumatic fever. c. acute glomerulonephritis and necrotizing fasciitis. d. acute glomerulonephritis and rheumatic fever. D There are two serious complications of group A streptococcal disease: rheumatic fever and acute glomerulonephritis. Rheumatic fever is a complication typically following Streptococcus pyogenes pharyngitis. Attacks usually begin within a month after infection. Acute glomerulonephritis may occur after a cutaneous or pharyngeal infection. The pathogenesis seems to be immunologically mediated. REF: 333 OBJ: Level 1: Recall 23. What is the drug of choice to treat group A streptococci when the patient cannot tolerate penicillin? a. Penicillin b. Erythromycin c. Gentamicin d. Cefoxitin B The group A streptococci are susceptible to penicillin, which remains the drug of choice in most cases. However, for patients allergic to penicillin, erythromycin is the drug of choice. REF: 333 OBJ: Level 1: Recall 24. What organism on sheep blood agar (SBA) has colonies that are small and transparent, surrounded by a wide zone of -hemolysis? a. Streptococcus agalactiae b. Streptococcus pyogenes c. Enterococcus d. Viridans strep B Colonies of S. pyogenes on SBA are small, transparent, and smooth with a well-defined area of -hemolysis. REF: 333 OBJ: Level 2: Interpretation 25. Streptococcus agalactiae is a significant cause of: a. pharyngitis. b. cystitis. c. invasive disease of the newborn. d. vaginitis. C S. agalactiae is a significant cause of invasive disease in the newborn. Two clinical syndromes are used to describe neonatal group B streptococcal disease: early-onset infection and late-onset infection. REF: 335 OBJ: Level 1: Recall 26. What organism on sheep blood agar (SBA) has grayish white colonies surrounded by a small zone of -hemolysis? a. Viridans strep b. Enterococcus c. Streptococcus pyogenes d. Streptococcus agalactiae D Group B streptococci grow on SBA as grayish white (sometimes mucoid) colonies surrounded by a small zone of -hemolysis. REF: 335 OBJ: Level 2: Interpretation 27. What are two tests presumptively used to identify group B strep? a. Hippurate hydrolysis and CAMP b. Optochin and PYR c. Bacitracin and PYR d. PYR and hippurate hydrolysis A Presumptive identification is based on biochemical reactions. The most useful tests are hippurate hydrolysis and the CAMP test. REF: 335 OBJ: Level 1: Recall 28. What two tests are presumptively used to identify Enterococcus? a. PYR and hippurate hydrolysis b. Bile esculin and 6.5% NaCl broth c. Bacitracin and PYR d. Catalase and coagulase B Unlike streptococci, enterococci have the ability to grow under extreme conditions; for example, in the presence of bile or 6.5% NaCl, or at 45C or an alkaline pH. REF: 340 OBJ: Level 1: Recall 29. What is VRE? a. Vancomycin-ready erythromycin b. Very-reliable erythromycin c. Vancomycin-resistant enterococcus d. Veocin-resistant enterococcus C Enterococci have intrinsic or acquired resistance to several antimicrobial agents including aminoglycosides, -lactams, and glycopeptides. Resistance of enterococci to glycopeptides, such as vancomycin and teicoplanin, were first described in the late 1980s. Vancomycin-resistant enterococci are VRE. REF: 340 OBJ: Level 1: Recall 30. One major virulence factor for Streptococcus pneumoniae is: a. hemolysin. b. protease. c. hyaluronidase. d. capsular polysaccharide. D The characteristic of S. pneumoniae that is clearly associated with virulence is the capsular polysaccharide. Laboratory strains that have lost the ability to produce a capsule are nonpathogenic. Several toxins are produced, including a hemolysin, an immunoglobulin A protease, neuraminidase, and hyaluronidase. None of these has been shown to have a role in disease production. REF: 336 OBJ: Level 1: Recall 31. Streptococcus pneumoniae causes all the following infections except: a. pharyngitis. b. pneumonia. c. bacteremia. d. meningitis. A S. pneumoniae is a common isolate in the clinical microbiology laboratory. It is an important human pathogen, causing pneumonia, sinusitis, otitis media, bacteremia, and meningitis. REF: 336 OBJ: Level 1: Recall 32. What is the drug of choice to treat Streptococcus pneumoniae? a. Erythromycin b. Penicillin c. Zithromax d. Chloramphenicol B Pneumococcal infections are usually treated with penicillin if the organism is confirmed susceptible. The emergence of resistance has increased in recent years, generating caution against empirical treatment assumptions. REF: 338 OBJ: Level 1: Recall 33. Why do Streptococcus pneumoniae colonies on sheep blood agar (SBA) appear like a coin—raised edges and a depressed center? a. The older growth at the center is smaller due to lack of nutrients. b. The newer growths on the outside of the colony undergo the quellung reaction. c. The older growth at the center is killed due to autolysis. d. The newer growth has a thicker capsule, therefore it appears raised. C As colonies become older, autolytic changes result in a collapse of each colony’s center, giving it the appearance of a coin with a raised rim. The tendency of S. pneumoniae to undergo autolysis can make it difficult to keep isolates alive. REF: 337 OBJ: Level 2: Interpretation 34. Where are the viridans streptococci constituents of the normal flora? a. Upper respiratory tract b. Female genital tract c. Gastrointestinal tract d. All of the above D The viridans streptococci are constituents of the normal flora of the upper respiratory tract, the female genital tract, and the gastrointestinal tract. The term viridans means green. REF: 338 OBJ: Level 1: Recall 35. Streptococcus-like organisms that resemble enterococci and viridans streptococci include all the following except: a. Moraxella. b. Aerococcus. c. Gemella. d. Lactococcus. A The genera Aerococcus, Gemella, Lactococcus, Leuconostoc, and Pediococcus consist of Streptococcus-like organisms that resemble enterococci and viridans streptococci. These have been isolated in clinical specimens and associated with infections similar to the ones caused by enterococci and streptococci. REF: 341 OBJ: Level 1: Recall 36. A young girl goes to her doctor’s office with a fever, headache, and a sore throat. The mother states the girl has a fever of 38.8° C (102° F). What test should the physician perform? a. Throat culture b. Antistreptolysin O c. Optochin d. Gram stain A With a sore throat and fever present, Streptococcus pyogenes is often isolated. The other tests are laboratory tests done on growing organisms, not clinical specimens. Gram stains are not appropriate tests on throat cultures. REF: 332 OBJ: Level 3: Synthesis 37. An 80-year-old woman is admitted from a nursing home where she has been sick with a cough and fever for 2 days. She is coughing up thick, rust-colored sputum. The physician prescribed penicillin, but she is not getting any better. What is her most probable diagnosis? a. Viral pneumonia b. Pneumococcal pneumonia with penicillin-resistant organism c. Enterococcal pneumonia with vancomycin-resistant enterococci (VRE) d. S. agalactiae infection B Streptococcus pneumoniae is the number one cause of bacterial pneumonia, especially prevalent in the elderly and patients with underlying disease. The patient was getting no better because the organism was resistant to penicillin. Rust-colored sputum is a common occurrence in pneumococcal pneumonia. REF: 336 OBJ: Level 3: Synthesis