Chapter 36: Bacteremia and Sepsis. Answers Explained

MULTIPLE CHOICE 1. Which of the following is an example of a primary bacteremia source? a. An infected heart valve b. A case of pneumonia c. A patient with hepatitis d. A wound abscess A Bacteremia may be ...

MULTIPLE CHOICE 1. Which of the following is an example of a primary bacteremia source? a. An infected heart valve b. A case of pneumonia c. A patient with hepatitis d. A wound abscess A Bacteremia may be classified by its site of origin. Primary bacteremia arises from an endovascular source, such as an infected cardiac valve or an infected intravenous catheter, whereas secondary bacteremia arises from an infected extravascular source, such as the lung in patients with pneumonia; a case in which the source of bacteremia remains undefined is termed bacteremia of unknown origin. REF: 869 OBJ: Level 2: Interpretation 2. Which of the following is an example of a secondary bacteremia source? a. An infected cardiac valve b. The lung c. An infected intravenous catheter d. The bone marrow B Bacteremia may be classified by its site of origin. Primary bacteremia arises from an endovascular source, such as an infected cardiac valve or an infected intravenous catheter, whereas secondary bacteremia arises from an infected extravascular source, such as the lung in patients with pneumonia; a case in which the source of bacteremia remains undefined is termed bacteremia of unknown origin. REF: 870 OBJ: Level 2: Interpretation 3. Bacteremias can be classified by all of the following categories except: a. microbiology. b. acquisition. c. pathogenesis. d. duration. C Bacteremias can be classified by microbiology, acquisition, and duration. REF: 870 OBJ: Level 1: Recall 4. What condition results when there is a procedural manipulation of a body site containing normal flora, causing those bacteria to enter the bloodstream? a. Continuous bacteremia b. Intermittent bacteremia c. Septic shock d. Transient bacteremia D Transient bacteremia usually occurs after a procedural manipulation of a particular body site that is colonized by indigenous flora, causing the organisms to enter the blood. Such sites include the mouth, and the gastrointestinal and urogenital tracts. Transient bacteremia may appear for a brief period following dental, colonoscopic, or cystoscopic procedures. REF: 870 OBJ: Level 1: Recall 5. What is the most common clinical manifestation associated with continuous bacteremia? a. Meningitis b. Pleurisy c. Encephalitis d. Endocarditis D Infective endocarditis is the most common clinical manifestation associated with continuous bacteremia, although other endovascular sources, such as infected intravascular catheters or septic thrombi, can result in continuous bacteremia. REF: 870 OBJ: Level 1: Recall 6. All of the following factors are associated with an unfavorable outcome in bacteremia except: a. surface wound or abscess. b. polymicrobial bacteremia. c. presence of malignancy. d. acquired immunodeficiency syndrome (AIDS). A Factors associated with an unfavorable outcome in bacteremia include age older than 70 years; polymicrobial bacteremia; presence of malignancy; AIDS or renal failure; origin of the bacteremia in the respiratory tract, bowel; unknown origin; and inappropriate antimicrobial therapy. REF: 870 OBJ: Level 1: Recall 7. Bacteremias are least often associated with which of the following patient conditions? a. Patients with hematologic malignancies b. Those undergoing elective outpatient surgical procedures c. Those receiving immunosuppressive chemotherapy d. Patients undergoing bone marrow transplantation B Bacteremias are more frequent among persons with neoplasia, especially those with hematologic malignancies, those receiving immunosuppressive chemotherapy, and those undergoing bone marrow transplantation. REF: 871 OBJ: Level 1: Recall 8. Which immunosuppressive agent can increase a patient’s risk of bacteremia? a. Cancer chemotherapy b. Corticosteroid therapy c. Transplant maintenance therapy d. All of the above D Bacteremias are more frequent among persons with neoplasia (abnormal growth of new cells that may be benign or malignant), especially those with hematologic malignancies, those receiving immunosuppressive medication or chemotherapy, and those undergoing bone marrow transplantation. Persons with other chronic underlying diseases (e.g., diabetes, cirrhosis) and those receiving immunosuppressive therapy (e.g., those receiving glucocorticoids for rheumatoid arthritis, stem cell or solid organ transplant patients) are also at increased risk for bacteremia. REF: 871 OBJ: Level 1: Recall 9. What underlying condition predisposes a person to a polymicrobial bacteremia? a. Intravenous drug use b. Burns c. Gastrointestinal tract sources d. All of the above D The predisposing factors in polymicrobial bacteremia include intravenous drug use, burns, and gastrointestinal tract sources. Especially at risk are immunocompromised patients, particularly those with alcoholism, granulocytopenia, extensive burns, diabetes mellitus, and chronic renal failure, and patients with vascular insufficiency as a result of ischemia. REF: 872 OBJ: Level 1: Recall 10. Development of a vaccine has decreased which major cause of bacteremia in children? a. Haemophilus influenzae b. Streptococcus pneumoniae c. Escherichia coli d. Hepatitis A A Some organisms have become less prevalent causes of bacteremia because of immunization practices that have decreased the risk of infection. For example, infection with H. influenzae b, formerly a major cause of bacteremia and sepsis in children, decreased by over 95% after introduction of the conjugate Hib vaccine. REF: 872 OBJ: Level 1: Recall 11. The patient’s immune system attempts to control infection via which of the following mechanisms? a. Antibodies b. Complement activation c. Phagocytosis d. All of the above D Once bacteremia occurs, the patient’s immune system attempts to control infection via antibodies, which opsonize organisms and allow complement-mediated killing, as well as by phagocytosis. In addition, filtering mechanisms in the lymphatics and large vascular beds in the liver and spleen may sequester organisms and allow their destruction. REF: 872 OBJ: Level 1: Recall 12. Bacteremia with which organism often leads to endocarditis, osteomyelitis, septic arthritis, hepatic abscess, or pyomyositis? a. Streptococcus pneumoniae b. Escherichia coli c. Staphylococcus aureus d. Pseudomonas aeruginosa C S. aureus is particularly prone to cause metastatic infection or abscess formation as a consequence of bacteremia; S. aureus bacteremia may lead to endocarditis, osteomyelitis, septic arthritis, hepatic abscess, or pyomyositis. REF: 872 OBJ: Level 2: Interpretation 13. What are two potential consequences of bacteremia? a. Endocarditis and meningitis b. Meningitis and encephalitis c. Encephalitis and hepatitis d. Sepsis and septic shock D Sepsis and septic shock are potential consequences of bacteremia. REF: 872 OBJ: Level 1: Recall 14. Lipopolysaccharide in gram-negative bacteria and the lipoteichoic acid and peptidoglycan in gram-positive bacteria cause which of the following to be released in the human body? a. Tumor necrosis factor b. Interleukin (IL)-1 c. IL-6 d. All of the above D In both cases, a bacterial membrane component (lipopolysaccharide, also known as endotoxin, in the case of gram-negative organisms; lipoteichoic acid and peptidoglycan in the case of gram-positive organisms) interacts with macrophages and causes release of tumor necrosis factor (TNF), interleukin-1 (IL-1), IL-6, and other proinflammatory cytokines, increasing endothelial activation, vascular permeability, blood flow, and recruitment of neutrophils. REF: 872 OBJ: Level 2: Interpretation 15. The most common sites associated with bacteremia and sepsis include all the following except: a. reproductive organs. b. infected intravascular catheters. c. the lung. d. the abdomen. A A number of sources often give rise to bacteremia. The most common sites associated with bacteremia and sepsis are infected intravascular catheters, the urinary tract, the lung, and the abdomen. REF: 873 OBJ: Level 1: Recall 16. All of the following organisms are colonizers of indwelling catheters except: a. coagulase-negative staphylococci. b. Streptococcus pyogenes. c. Staphylococcus aureus. d. Enterococcus spp. B As useful as indwelling catheters are, they are highly vulnerable to colonization and infection by organisms, such as coagulase-negative staphylococci, S. aureus, and Enterococcus spp., with subsequent spread to the bloodstream to cause bacteremia; frequently, the strains causing a catheter-related bloodstream infection are resistant to multiple antibiotics. REF: 871 OBJ: Level 1: Recall 17. How does a biofilm protect the organism from host defenses? a. By inhibiting phagocytosis b. By inhibiting chemotaxis c. By suppressing the lymphoproliferative response d. All of the above D The biofilm protects the organism from host defenses by inhibiting phagocytosis, chemotaxis, and oxidative metabolism and by suppressing the lymphoproliferative response. It may also significantly increase the concentrations of antimicrobials required to inhibit the growth of coagulase negative staphylococci attached to the catheter. REF: 873 OBJ: Level 1: Recall 18. What organism is most commonly associated with bacteremia due to acute pyelonephritis? a. Escherichia coli b. Enterobacter aerogenes c. Pseudomonas aeruginosa d. Staphylococcus aureus A Urinary tract infections account for roughly 17% of all bacteremias. Infection of the upper urinary tract (acute pyelonephritis) leads to bacteremia in up to 40% of affected patients. E. coli is the most common cause of bacteremia in this setting. REF: 873 OBJ: Level 1: Recall 19. All of the following organisms are common causes of pneumonia and which typically produce a concurrent bacteremia except: a. Enterobacter aerogenes. b. Escherichia coli. c. Pseudomonas aeruginosa. d. Staphylococcus aureus. B The most common organisms in pneumonia that produce a concurrent bacteremia include S. pneumonia, H. influenzae, S. aureus, P. aeruginosa, and Enterobacter aerogenes. REF: 873 OBJ: Level 1: Recall 20. What condition leads to most (75%) of the cases of bacteremia arising from intra-abdominal infections? a. Pleurisy b. Cholecystitis c. Peritonitis d. Irritable bowel syndrome C Primary peritonitis, which frequently occurs in patients with cirrhosis, is associated with bacteremia in 75% of cases involving aerobic bacteria; common pathogens include Escherichia coli, Klebsiella pneumoniae, Streptococcus pneumoniae, and Enterococcus. REF: 873 OBJ: Level 1: Recall 21. What can happen when a transient bacteremia is produced from a dental procedure or a superficial skin infection? a. Hepatitis can result. b. Pneumonia can result. c. Deep vein thrombosis can result. d. Cardiac valves can be seeded with bacteria. D Transient bacteremia (from dental procedures or a superficial skin infection) can seed cardiac valves with bacteria. These organisms multiply within a dense vegetation composed of bacteria and fibrin, protected from killing by neutrophils, and give rise to a continuous bacteremia, which can then seed other organs. REF: 874 OBJ: Level 2: Interpretation 22. What type of a medical implant device is commonly associated with osteomyelitis, which will then lead to bacteremia? a. Prosthetic joints b. Stainless steel rods c. Orthopedic screws d. Orthopedic plates A Prosthetic joints, particularly those implanted in the hip, can be hematogenously seeded by organisms, such as Staphylococcus aureus and coagulase-negative staphylococcus, and then give rise to bacteremia. REF: 874 OBJ: Level 2: Interpretation 23. Abnormal conditions that may indicate the presence of bacteremia include all the following except: a. disseminated intravascular coagulation (DIC). b. thrombocytopenia. c. coagulopathy. d. anemia. D Altered clinical laboratory values that may be indicative of bacteremia include the following: thrombocytopenia, leukocytosis or leukopenia, lactic acidosis, hypoglycemia or hyperglycemia, abnormal liver function tests, coagulopathy, DIC, and elevations in C-reactive protein, haptoglobin, and fibrinogen. REF: 874 OBJ: Level 1: Recall 24. When drawing blood for blood cultures in a child younger than age 10, how much blood should be drawn? a. 1 mL for each year of life b. 5 mL c. 2 mL d. 1 mL for children younger than 2 years old, 3 mL for children younger than 7 years old, and 5 mL for children up to 10 years old A The following age-volume protocol has been recommended: younger than age 10, 1 mL of blood for each year of life; 10 years old or older, 20 mL; and 10 years old or older (poor veins), less than 20 mL. This protocol is based on studies that have demonstrated that as the volume of blood cultured increases from 2 to 20 mL, the yield of positive culture results increases from 30% to 50%, except in newborns. REF: 875 OBJ: Level 1: Recall 25. The recommendation of three sets of blood culture drawn at 1-hour intervals is recommended to diagnose which of the following conditions? a. Meningitis b. Infective endocarditis c. Pneumonia d. Peritonitis B Arbitrary timing of 30- to 60-minute intervals between draws has shown no significant differences in positivity rates, therefore blood culture sets may be obtained simultaneously or consecutively as long as they are from separate venipunctures. The exception is for suspected infective endocarditis in which 30- to 60-minute intervals are recommended to document continuous bacteremia. REF: 876 OBJ: Level 2: Interpretation 26. If a patient with a bacteremia is receiving appropriate antibiotics for a known infection but is not responding to treatment, how does the physician find out if another organism is causing the problem? a. Redraw the blood cultures. b. Redraw the blood cultures using an antibiotic removal device (ARD). c. Switch the patient to another antibiotic that will resolve the clinical symptoms. d. Perform hemodialysis to remove the organisms from the patient’s blood. B In specimens from patients receiving clinical amounts of -lactam antimicrobial agents, penicillinase may be added to the medium to inactivate these agents. Some commercially available automated blood culture systems have blood culture bottles containing ARD, a resin that nonspecifically absorbs any antimicrobial agent present in the patient’s blood. REF: 877 OBJ: Level 2: Interpretation 27. SPS performs all the following functions in the blood culture bottles except: a. anticoagulation. b. prevention of phagocytosis. c. act as a bacterial nutrient. d. inactivate certain antibiotics. C SPS, one of the commonly used additives, performs the following functions: anticoagulation, neutralization of the bactericidal effect of human serum, prevention of phagocytosis, and inactivation of certain antimicrobial agents. REF: 877 OBJ: Level 2: Interpretation 28. Septi-Chek is which type of blood culture system? a. Continuous-monitoring blood culture system b. Lysis-centrifugation blood culture system c. Aerobic-anaerobic blood culture system d. Biphasic broth-slide system D A broth-slide system was designed from the original biphasic blood culture medium culture bottle. Septi-Chek consists of a slide paddle containing chocolate, MacConkey, and malt extract agars attached to the top of a standard broth bottle. Once these bottles have been inoculated, they should be tipped daily or at least twice weekly so as to bathe the slide paddle with the broth culture medium. REF: 877 OBJ: Level 1: Recall 29. What is the principle of a continuous monitoring blood culture system? a. The amount of 14CO2 produced is measured as a growth index and compared with a threshold. b. The amount of increased lipopolysaccharide is measured and compared against the null value. c. The pH of the media is continuously measured to check for bacterial metabolic by-products. d. An optical monitor records the number of bacteria and records the growth. A When the organism in the blood culture bottle uses 14CO2-labeled substrate, 14CO2 is released. The instrument monitors CO2 production by aspirating gas into an ionization chamber using sterile needles. In the ionization chamber, the amount of 14CO2 produced is measured as growth index and compared with an established threshold level. REF: 878 OBJ: Level 1: Recall 30. How long are conventional (manually processed) blood cultures held before being discarded as negative? a. 4 days b. 7 days c. 14 days d. 21 days B Blood culture bottles are incubated at 35° 2° C for 5 days typically for the automated systems and may be held for 7 days for the manual systems. REF: 877 OBJ: Level 1: Recall 31. Separate venipunctures were performed to collect three sets of blood cultures from a patient with an artificial heart valve. The first and third sets grew a gram-positive pleomorphic rod in 1 of 2 bottles while the second set had no growth in either bottle. What is the most likely explanation for these findings? a. The patient probably has an infection with Clostridium spp. b. The blood cultures were contaminated with skin flora. c. The blood cultures were probably contaminated in the laboratory. d. The patient probably has an infection with Bacillus spp. B It is important to remember that even though antiseptic technique is used in the collection of blood, somewhere between 1% and 3% of blood cultures become contaminated with organisms such as coagulase-negative staphylococci, Corynebacterium spp., Bacillus spp. (not B. anthracis), alpha-hemolytic streptococci, and Propionibacterium acnes, which are ordinarily skin colonizers, resulting in pseudobacteremia. REF: 874 OBJ: Level 3: Synthesis 32. A patient receiving chemotherapy for leukemia has developed a fever causing the physician to request blood cultures times three. Each set of cultures grows an -hemolytic streptococcal organism? What is the most likely explanation for these results? a. The patient probably has an infection with -hemolytic strep. b. The blood cultures were contaminated with skin flora c. The blood cultures were probably contaminated in the laboratory. d. The patient probably has an infection with Bacillus spp. A In some patients, such as those receiving cancer chemotherapy, organisms such as coagulase-negative staphylococci, Corynebacterium spp., Bacillus spp. (not B. anthracis), -hemolytic streptococci, and Propionibacterium acnes, can represent true pathogens, making it essential to distinguish between blood culture results that reflect true bacteremia and those that represent pseudobacteremia. REF: 874 OBJ: Level 3: Synthesis 33. Which of the following organisms are inhibited by the anticoagulant sodium polyanethole sulfonate (SPS)? a. Enterobacter aerogenes b. Escherichia coli c. Peptostreptococcus anaerobius d. Streptococcus pyogenes C Despite its usefulness in blood culture media, SPS inhibits the growth of certain organisms, notably Peptostreptococcus anaerobius, Neisseria gonorrhoeae, N. meningitidis, and Gardnerella vaginalis. If these organisms are suspected, 1.2% gelatin added to the blood culture bottle may help to neutralize the inhibitory effect of SPS. REF: 877 OBJ: Level 3: Synthesis