Chapter 16: Aerobic Gram-Positive Bacilli. All Answers

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MULTIPLE CHOICE 1. What is the name of the group of bacteria that are slightly curved, gram-positive rods often referred to as club-shaped or Chinese letters when viewed in a Gram stain? a. Coryn... ebacterium b. Staphylococcus c. Neisseria d. Listeria A Upon Gram staining, corynebacteria demonstrate slightly curved, gram-positive rods with unparallel sides and slightly wider ends, producing the described club shape or coryneform. The term diphtheroid, meaning diphtheria-like, is sometimes used in reference to this Gram staining morphology. REF: 350 OBJ: Level 2: Interpretation 2. What is the major virulence factor associated with Corynebacterium diphtheriae? a. Trypsin b. Diphtheria toxin c. Diphtheria bacteriophage d. Hyaluronidase B The major virulence factor associated with C. diphtheriae is the diphtheria toxin. This toxin is produced by strains of C. diphtheriae infected with a temperate bacteriophage, which carries the tox gene for diphtheria toxin. Only toxin-producing strains cause the disease diphtheria. REF: 350 OBJ: Level 1: Recall 3. A young girl is brought to her physician by her mother, who says the child has been very sluggish with a fever of 38° C (100.5 F) for a week. The mother noticed that the child’s tonsils were red and that yesterday the back of her throat turned a gray color and looked to have a gray membrane on it. What disease should the physician suspect? a. Strep throat b. Tonsillitis c. Diphtheria d. Scarlet fever C Corynebacterium diphtheriae is carried in the upper respiratory tract and spread by droplet infection or hand-to-mouth contact. The incubation period averages 2 to 5 days. The illness begins gradually and is characterized by low-grade fever, malaise, and a mild sore throat. The most common site of infection is the tonsils or pharynx. The organisms rapidly multiply on the epithelial cells, and the toxigenic strains of C. diphtheriae produce toxin locally, causing tissue necrosis and exudate formation, triggering an inflammatory reaction. This combination of cell necrosis and exudates forms a tough gray to white pseudomembrane, which attaches to the tissues. REF: 352 OBJ: Level 3: Synthesis 4. What organism displays Babès-Ernst granules on a Gram stain? a. Listeria monocytogenes b. Erysipelothrix rhusiopathiae c. Rhodococcus equi d. Corynebacterium diphtheriae D C. diphtheriae often stains irregularly, especially when stained with methylene blue, giving them a beaded appearance. The metachromatic areas of the cell, which stain more intensely than other parts, are called Babès-Ernst granules. They represent accumulation of polymerized polyphosphates. REF: 352 OBJ: Level 2: Interpretation 5. What media does Corynebacterium diphtheriae grow on? a. Sheep blood agar (SBA) b. Loeffler c. Cystine-tellurite blood d. All of the above D Although C. diphtheriae will grow on nutrient agar, better growth is usually obtained on a medium containing blood or serum, such as Loeffler serum or Pai agars. Characteristic microscopic morphology is demonstrated well when organisms are grown on Loeffler medium. On SBA, the organism may have a very small zone of hemolysis. Cystine-tellurite blood agar is a modification of Tinsdale medium, and when grown on this medium, the corynebacteria form black or brownish colonies from the reduction of tellurite. REF: 352 OBJ: Level 1: Recall 6. What test is performed to determine if Corynebacterium diphtheriae is a toxigenic strain of an organism? a. Elek test b. Schick test c. Lancefield group test d. Coagulase A The in vitro diphtheria toxin detection procedure is an immunodiffusion test first described by Elek and called the Elek test. REF: 353 OBJ: Level 2: Interpretation 7. What Corynebacterium infects mostly immunocompromised patients? a. C. pseudotuberculosis b. C. jeikeium c. C. striatum d. C. ulcerans B C. jeikeium, named after Johnson and Kaye who first linked this organism with human infections, appears to be part of the usual skin flora. Infections have been limited to patients who are immunocompromised, have undergone invasive procedures, or have a history of intravenous drug abuse. REF: 355 OBJ: Level 1: Recall 8. What is one of the most frequently isolated, clinical significant corynebacteria? a. Corynebacterium ulcerans b. C. pseudotuberculosis c. C. urealyticum d. C. diphtheriae C C. urealyticum is one of the most frequently isolated clinically significant Corynebacterium. It has been described as primarily a urinary pathogen. REF: 355 OBJ: Level 1: Recall 9. All of the following species of Arcanobacterium are clinically significant except: a. Arcanobacterium haemolyticum. b. A. pyogenes. c. A. bernardiae. d. A. urealyticum. D Three species of Arcanobacterium are clinically significant: A. haemolyticum, A. pyogenes, and A. bernardiae. REF: 360 OBJ: Level 1: Recall 10. What is the colony morphology of A. haemolyticum on sheep blood agar (SBA)? a. A narrow zone of -hemolysis and a black opaque dot is seen when the colony is scraped away b. -Hemolysis, with pitting around the edges of the colony c. -Hemolysis, with a central black opaque dot in the colony d. A wide zone of -hemolysis and a large, yellow, mucoid colony A A. haemolyticum produces small colonies on SBA that demonstrate a narrow zone of hemolysis after 24 to 48 hours of incubation similar in appearance to the -hemolytic streptococci. Frequently, a black opaque dot is observed on the agar when the colony is scraped away. Pitting of the agar beneath the colony has also been reported. REF: 360 OBJ: Level 2: Interpretation 11. What organism shows diphtheroid gram-positive rods with traces of branching on a Gram stain? a. Rothia dentocariosa b. Rhodococcus equi c. Listeria monocytogenes d. Corynebacterium diphtheriae B Key features for the identification of Rhodococcus is the salmon-pink pigment and a Gram stain showing characteristic diphtheroid gram-positive rods with traces of branching. REF: 365 OBJ: Level 2: Interpretation 12. What organism is a member of the human oropharyngeal flora, but has been isolated from people with endocarditis? a. Listeria monocytogenes b. Rhodococcus equi c. Rothia dentocariosa d. Corynebacterium diphtheriae C A member of the normal human oropharyngeal flora, R. dentocariosa may be found in saliva and supragingival plaque. It has been isolated from patients with endocarditis. REF: 356 OBJ: Level 2: Interpretation 13. What organism is responsible for spontaneous abortion and stillborn neonates, and can cause meningitis with a fatality rate approaching 50% in newborns? a. Corynebacterium diphtheriae b. Rhodococcus equi c. Rothia dentocariosa d. Listeria monocytogenes D Infection of the neonate with L. monocytogenes is extremely serious. Fatality rates are high, approaching 50% if the fetus is born alive. Late-onset disease occurs several days to weeks after birth. Affected infants generally are full term and healthy at birth. The disease is most likely to manifest as meningitis. REF: 357 OBJ: Level 2: Interpretation 14. Several people from a picnic came down with a gastrointestinal disturbance, and public health officials suspected a case of food poisoning. The food, especially hot dogs, were cultured and after 24 hours of growth on sheep blood agar (SBA), there was a small, round, smooth, translucent colony surrounded by a narrow zone of -hemolysis. A Gram stain showed gram-positive coccobacilli. Motility medium was inoculated and an umbrella pattern of motility was observed at room temperature. What organism was isolated as the cause of the illness? a. Listeria monocytogenes b. Rhodococcus equi c. Rothia dentocariosa d. Corynebacterium diphtheriae A L. monocytogenes is catalase positive and motile at room temperature, which along with -hemolysis excludes corynebacteria. In wet mount preparations, L. monocytogenes exhibits “tumbling motility” when viewed microscopically. In motility medium, the characteristic “umbrella” pattern is seen when the organism is incubated at room temperature. REF: 357 OBJ: Level 3: Synthesis 15. Erysipelothrix rhusiopathiae produces all the following diseases except: a. septicemia. b. meningitis. c. endocarditis. d. erysipeloid. B E. rhusiopathiae produces three types of disease in hum septicemia, endocarditis, and erysipeloid. The incidence of E. rhusiopathiae infections is low. Systemic infection is very uncommon and rarely develops from localized infection. REF: 358 OBJ: Level 1: Recall 16. One of the foremen at a pig farm notices purple sores on one of his workers. The worker has not been feeling well for the past 2 weeks, so the foreman sends him to the doctor. The doctor takes scrapings from the sores and sends them to the laboratory for a culture and sensitivity. The Gram stain shows 3+ thin, gram-positive rods that have filaments. The culture plates were examined the next day and revealed nonhemolytic, pinpoint, transparent colonies. What is the most likely pathogen? a. Streptococcus pneumoniae b. Streptococcus pyogenes c. Erysipelothrix rhusiopathiae d. Rhodococcus C E. rhusiopathiae is the only species in the genus. It is a gram-positive, nonsporulating, pleomorphic rod that has a tendency to form long filaments. It is found worldwide and is a commensal or a pathogen in a very wide variety of vertebrates and invertebrates. Domestic swine are the major reservoir. Erysipeloid is a localized skin infection that resembles streptococcal erysipelas. The infected area is painful and swollen, and gives rise to a characteristic lesion—a sharply defined, slightly elevated, purplish red zone that spreads peripherally as discoloration of the central area fades. Low-grade fever, arthralgia, lymphangiitis, and lymphadenopathy may occur. REF: 359 OBJ: Level 3: Synthesis 17. What is the name of the bacteria that plays an important role in the health of the female vaginal tract, protecting it against pathogens? a. Diphtheroids b. Gardnerella vaginalis c. Erysipelothrix rhusiopathiae d. Lactobacillus D Lactobacillus spp. plays an important role in the health of the female vaginal tract, because it is recognized as protecting the host from urogenital infections. Lactobacilli produce lactic acid from glycogen, which lowers the vaginal pH and suppresses the overgrowth of organisms like Mobiluncus, Prevotella, and Gardnerella vaginalis. REF: 361 OBJ: Level 2: Interpretation 18. After 24 hours, a sheep blood agar (SBA) from a vaginal culture is read. The SBA has -hemolytic, pinpoint, rough colonies all over the plate. A catalase test is performed, and it is negative. What organisms do these characteristics fit? a. Lactobacillus and viridans streptococci b. Diphtheroids and rhodococci c. Staphylococcus and Listeria d. Corynebacterium and Arcanobacterium A Colony morphology of Lactobacillus varies and ranges from -hemolytic, pinpoint in size to rough and gray in color. Catalase is negative and, unless a Gram stain is performed, differentiation from Streptococcus sp. viridans group is difficult. REF: 361 OBJ: Level 3: Synthesis 19. All the following are general characteristics of the genus Bacillus except: a. aerobic. b. gram-positive. c. form endospores. d. cocci. D Members of the genus Bacillus are aerobic, gram-positive, rod-shaped organisms that form endospores. On Gram stain, however, spores do not stain and appear only as “empty spaces.” REF: 365 OBJ: Level 1: Recall 20. What is the name of the Bacillus sp. that causes anthrax in cattle? a. B. anthracis b. B. cereus c. B. asteroids d. B. subtilis A B. anthracis was shown to cause anthrax in cattle by Robert Koch in the development of Koch’s postulates in helping to prove the germ theory of disease. REF: 365 OBJ: Level 1: Recall 21. What is the name of the species that, before the onset of bioterrorism and immunocompromised patients, was considered a common laboratory contaminant? a. Streptococcus b. Bacillus c. Rhodococcus d. Arcanobacterium B Bacillus spp. are found as contaminants in specimens from a number of sources. B. anthracis is the bioterrorism agent that can cause inhalation anthrax. B. cereus and B. subtilis have been found to occasionally cause serious illness in immunocompromised patients. REF: 365 OBJ: Level 1: Recall 22. The three proteins that make up the anthrax toxin include all the following except: a. protective antigen. b. edema factor. c. cellular factor. d. lethal factor. C Anthrax toxin consists of three proteins called protective antigen, edema factor, and lethal factor, each of which individually is nontoxic but act synergistically to produce damaging effects. REF: 366 OBJ: Level 1: Recall 23. How is anthrax spread in animals? a. Respiratory-droplet where the bacteria is directly transferred b. Intimate contact where the bacteria is directly transferred c. Drinking contaminated water where the bacteria is directly transferred d. Eating plants contaminated with the spores D The disease is not spread from animal to animal but rather by animals feeding on plants contaminated with the spores. REF: 366 OBJ: Level 1: Recall 24. What form of anthrax is found among animal workers and has been dubbed woolsorter’s disease? a. Cutaneous b. Gastrointestinal c. Inhalation d. Optical C Terms such as woolsorter’s disease and ragpicker’s disease were used to describe infection with spores of B. anthracis as a result of handling contaminated animal fibers, hides, and other animal products. Inhalation anthrax, also called woolsorter’s disease, is acquired when spores are inhaled into the pulmonary parenchyma. REF: 366 OBJ: Level 1: Recall 25. The symptoms of inhalation anthrax include all of the following except: a. productive cough. b. dyspnea. c. cyanosis. d. disorientation. A The severe phase of the inhalation anthrax has a high mortality rate. The respiratory problems (dyspnea, cyanosis, pleural effusion) are followed by disorientation, then coma, and death. REF: 366 OBJ: Level 1: Recall 26. The symptoms of gastrointestinal anthrax include all the following except: a. abdominal pain. b. rice water stools. c. bloody diarrhea. d. vomiting. B Gastrointestinal anthrax occurs when the spores are inoculated into a lesion on the intestinal mucosa following ingestion of the spores. The symptoms of gastrointestinal anthrax include abdominal pain, nausea, anorexia, and vomiting. Bloody diarrhea may also occur. REF: 366 OBJ: Level 1: Recall 27. What disease is considered a complication of any form of anthrax (cutaneous, gastrointestinal, or inhalation)? a. Sepsis b. Endocarditis c. Meningitis d. Gangrene C Approximately 5% of patients with anthrax (cutaneous, inhalation, gastrointestinal) develop meningitis. REF: 367 OBJ: Level 1: Recall 28. What bacteria’s morphology is described as large, square-ended, gram-positive or gram-variable rods found singly or in chains? a. Streptococcus pneumoniae b. Nocardia asteroids c. Listeria monocytogenes d. Bacillus anthracis D B. anthracis is a large, square-ended, gram-positive or gram-variable rod found singly or in chains. In Gram stain preparations of clinical samples, vegetative cells can appear with clear zones around the cells, representing the presence of a capsule. REF: 367 OBJ: Level 2: Interpretation 29. What bacterium produces colonies that are nonhemolytic, large, gray, and flat with an irregular margin on sheep blood agar (SBA)? a. Bacillus anthracis b. Streptococcus pneumoniae c. Nocardia asteroides d. Listeria monocytogenes A On SBA, colonies of B. anthracis are nonhemolytic, large (2 to 5 mm), gray, and flat with an irregular margin because of outgrowths of long filamentous projections of bacteria that can be seen with a dissecting microscope. The term Medusa head has been used to describe the colony morphology of B. anthracis. REF: 367 OBJ: Level 2: Interpretation 30. All the following tests should be performed by sentinel laboratories to rule out the possibility of Bacillus anthracis from an isolate except: a. gram stain. b. glucose fermentation. c. catalase. d. motility. B In order to rule out B. anthracis, the Centers for Disease Control and Prevention (CDC) has established basic diagnostic protocols. These protocols include a minimum number of common tests. Caution should always be used in working with an isolate suspected of being B. anthracis. Work should be done in a biologic safety cabinet, and the area should be disinfected when the work is complete. Approved tests to be performed by sentinel laboratories include Gram stain, colony morphology, catalase, motility, and capsule detection. The Gram stain can be performed directly on clinical specimens or on culture isolates. REF: 367 OBJ: Level 1: Recall 31. What are the confirmatory tests performed at a state laboratory for Bacillus anthracis? a. Flagellar antigen and mannitol fermentation b. Endospore stain and a capsule antigen c. Cell wall polysaccharide and a capsule antigen d. Cell wall polysaccharide and an endospore stain C The reference laboratory will likely perform direct fluorescent antibody assays for a cell wall polysaccharide and a capsule antigen. The presence of both antigens is confirmation for B. anthracis. REF: 368 OBJ: Level 1: Recall 32. What antibiotic, in 2000, was approved by the U.S. Food and Drug Administration (FDA) for postexposure inhalation anthrax? a. Penicillin b. Erythromycin c. Cephalosporin d. Ciprofloxacin D In 2000, ciprofloxacin was approved by the FDA for management of postexposure inhalation anthrax based on data from animal models. According to the Centers for Disease Control and Prevention (CDC) recommendations and based on studies in nonhuman primates and other animal and in vitro data, ciprofloxacin or doxycycline should be used for initial intravenous therapy until antimicrobial susceptibility results are known. REF: 368 OBJ: Level 1: Recall 33. What Bacillus sp. is a relatively common cause of food poisoning and opportunistic infection in susceptible hosts? a. Bacillus cereus b. B. anthracis c. B. asteroids d. B. pneumoniae A B. cereus is a relatively common cause of food poisoning and an opportunistic infection in susceptible hosts. Food poisoning caused by B. cereus takes two forms: diarrheal and emetic. REF: 368 OBJ: Level 2: Interpretation 34. What other gram-positive rod is similar to Bacillus anthracis? a. B. subtilis b. B. cereus c. L. monocytogenes d. E. rhusiopathiae B B. cereus is similar to B. anthracis in many ways, both morphologically and metabolically. REF: 369 OBJ: Level 1: Recall 35. Which of the following is true about Nocardia spp.? a. These organisms grow well on standard nonselective media. b. Growth may take a week or more. c. Infections occur in immunocompromised patients. d. All of the above. D The colonial and microscopic morphology, and the types of infections caused, resemble those of the fungi, but these organisms are true bacteria. Nocardia spp. grow well on standard nonselective media. Growth may take a week or more. Generally, infections caused by these organisms are seen in immunocompromised patients. REF: 361 OBJ: Level 1: Recall 36. All of the following are commonly encountered Nocardia spp. except: a. Nocardia asteroides. b. N. brasiliensis. c. N. transvalensis. d. N. nova. C The most commonly encountered species include N. asteroides, N. brasiliensis, N. farcinica, and N. nova. Less commonly encountered species include N. otitidiscaviarum, N. pseudobrasiliensis, N. abscessus, N. africana, and N. transvalensis. REF: 362 OBJ: Level 1: Recall 37. What is the name of the iron-chelating compound produced by Nocardia spp.? a. Nocobactin b. Novobiocin c. Narcalase d. Niacin A Nocardia spp. produce an iron-chelating compound called nocobactin. A correlation has been reported between the amount of nocobactin produced by the organism and its virulence. REF: 362 OBJ: Level 1: Recall 38. What is the name of the Nocardia sp. that causes a chronic confluent bronchopneumonia? a. Nocardia nova b. N. brasiliensis c. N. asteroides d. N. transvalensis C The majority of pulmonary infections are caused by the N. asteroides complex. The most common manifestation of infection is a confluent bronchopneumonia that is usually chronic but may be acute or relapsing. REF: 362 OBJ: Level 2: Interpretation 39. What is the name of the Nocardia sp. that most frequently causes a cutaneous infection? a. Nocardia nova b. N. brasiliensis c. N. asteroides d. N. transvalensis B Cutaneous infection occurs following inoculation of the organism into the skin or subcutaneous tissues. N. brasiliensis is the most frequent cause of this form of nocardiosis, which is usually seen in the hands and feet as a result of outdoor activity. REF: 362 OBJ: Level 1: Recall 40. How can Nocardia spp. be presumptively identified? a. Strong staining with Gram stain and the presence of filamentous, branching organisms b. Medusa head colonies with filamentous, branching organisms present on acid-fast stain c. Sulfur granules that when crushed and Gram stained reveal filamentous, branching organisms d. Filamentous, branching organisms with a carbolfuchsin acid-fast stain with a weak acid decolorizer, but not a Kinyoun acid-fast stain D Presumptive identification of Nocardia spp. can be made based on observation of a filamentous, branching isolate that is acid fast upon staining with carbolfuchsin and decolorizing with a weak acid (0.5% to 1.0% sulfuric acid), but not with the Kinyoun acid-fast stain. REF: 363 OBJ: Level 1: Recall 41. Why is it that although Nocardia spp. grow well on most common nonselective laboratory media, many are missed when the cultures are read? a. These organisms require 3 to 6 days to grow. b. These organisms require factors X and V to grow. c. These organisms require 3 to 6 weeks to grow. d. These organisms are anaerobic. A These organisms show an oxidative type of metabolism, and as a genus, they use a wide variety of sugars. They do not require specific growth factors as do Haemophilus and Francisella organisms. Nocardia spp. grow well on most common nonselective laboratory media incubated at temperatures between 25 C and 37 C, although 3 to 6 days or longer may pass before growth is seen. Most cultures are read for 48 hours, then the plates are discarded. REF: 363 OBJ: Level 2: Interpretation 42. Why is it extremely important to diagnose infections with Nocardia spp.? a. Antifungal agents do not kill these organisms. b. These organisms are resistant to penicillin. c. These organisms are susceptible to sulfonamides. d. All of the above. D Treatment of Nocardia infection often involves drainage and surgery and antimicrobials. The organisms are resistant to penicillin but susceptible to sulfonamides. Antifungal agents, of course, have no activity against Nocardia organisms; this fact underscores the importance of laboratory diagnosis, because many of the clinical manifestations of pulmonary and cutaneous infection are shared with other organisms, including fungi. REF: 363 OBJ: Level 2: Interpretation 43. What are the names of the species of organism that are primarily saprophytic organisms and resemble other aerobic actinomycetes with the morphology and diseases they cause? a. Actinomadura b. Saprophytes c. Streptomyces d. Streptococcus C The genus Streptomyces is a large, diverse group of bacteria. Streptomyces spp. are primarily saprophytes found as soil microorganisms and resemble the other aerobic actinomycetes with regard to morphology and the diseases they cause. REF: 364 OBJ: Level 1: Recall 44. What is the name of the genus whose members are called nocardioforms? a. Gordonia b. Weimeronia c. Rhodococcus d. Tsukamurella A Members of the genus Gordonia are aerobic, catalase-positive, gram-positive to gram-variable, slightly acid fast, nonmotile. They grow with mycelial forms that fragment into rod-shaped or coccoid elements—hence, the term nocardioform. REF: 364 OBJ: Level 1: Recall 45. Infections caused by Tsukamurella paurometabola include all the following except: a. chronic lung infection. b. brain abscesses. c. knee prosthesis infection. d. conjunctivitis. B Several species of Tsukamurella have been reported to cause infections in humans. Most infections reported in the literature have been due to T. paurometabola and include chronic lung infection, subcutaneous abscess, cutaneous lesions, catheter-related bacteremia, peritonitis associated with continuous ambulatory peritoneal dialysis, knee prosthesis infection, and conjunctivitis. REF: 365 OBJ: Level 1: Recall [Show More]

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