Exam 3 - (CH 21) Nonfermenting and Miscellaneous Gram-Negative Bacilli Textbook Review Questions Flashcards
Which of the following is an exotoxin produced by Pseudomonas aeruginosa?
A. DNase
B. Lipopolysaccharide
C. Phospholipase
D. Alginate
A. DNase
Which pigment produced by Pseudomonas aeruginosa is water-soluble and fluoresces under short-wavelength ultraviolet light?
A. Pyocyanin
B. Pyoverdin
C. Pyorubin
D. Pyomelanin
B. Pyoverdin
Which of the following sets of reactions distinguishes Pseudomonas stutzeri from most other Pseudomonas spp.?
A. Arginine dihydrolase (ADH) negative and starch hydrolysis positive
B. ADH positive and starch hydrolysis positive
C. Growth at 4°C and gelatin hydrolysis positive
D. Growth at 42°C and production of pyverdin
A. Arginine dihydrolase (ADH) negative and starch hydrolysis positive
Which best describes Acinetobacter baumannii?
A. Asaccharolytic, oxidase negative, and catalase positive
B. Nonlactose fermenting, oxidase positive, and catalase negative
C. Lactose fermenting, oxidase negative, and nonmotile
D. Asaccharolytic, oxidase and catalase positive, and motile
C. Lactose fermenting, oxidase negative, and nonmotile
Stenotrophomonas maltophilia is positive for this test.
A. Oxidase
B. Lactose fermentation
C. DNase
D. o-Nitrophenyl-β-D-galactopyranoside (ONPG)
C. DNase
Studies suggest that this plate is most effective in reducing overgrowth while maintaining good recovery of Burkholderia cepacia.
A. B. cepacia–selective agar (BCSA)
B. Oxidative-fermentative base, polymyxin B, bacitracin, lactose (OFPBL)
C. Thiosulfate citrate bile salt sucrose (TCBS) agar
D. Cefsulodin-irgasan-novobiocin (CIN) agar
A. B. cepacia–selective agar (BCSA)
This test result indicates an isolate is most likely Oligella ureolytica rather than an Alcaligenes spp.
A. Nonmotile
B. Abundant growth on MacConkey (MAC) agar
C. Nonoxidative
D. Positive phenylalanine deaminase (PDA)
D. Positive phenylalanine deaminase (PDA)
Which is the best test to differentiate between Brevundimonas vesicularis and Brevundimonas diminuta?
A. Oxidase
B. Glucose oxidation
C. Maltose oxidation
D. Esculin hydrolysis
D. Esculin hydrolysis
Nonpigmented strains of Chromobacterium violaceum have been confused with
A. Aeromonas.
B. Pseudomonas.
C. Citrobacter.
D. Plesiomonas.
A. Aeromonas
Which of the following best describes Ralstonia pickettii?
A. Oxidase and catalase negative
B. Nonmotile and does not grow on MAC agar
C. Slow grower that grows on MAC agar
D. Resistant to all cephalosporins and carbapenem
C. Slow grower that grows on MAC agar
Based on carbohydrate utilization, what is the difference between nonfermentative and fermentative organisms?
Fermentative gram-negative bacilli are able to metabolize carbohydrates to derive energy under anaerobic conditions. Phenotypically, these bacteria can produce an acid “butt” in specific media (e.g., triple sugar iron [TSI] agar or Kligler iron agar [KIA]). Nonfermenters cannot ferment sugars and are not able to acidify the butt of TSI or KIA.
What is the typical natural habitat of most nonfermenters?
Most nonfermenters exist in the environment, often a moist or aquatic environment. They are not usually part of the normal human biota. Nonfermenters may also be found in soil and on plants, as well as in hospital environments on countertops, on equipment, and occasionally in contaminated liquids used for dispensing medications and disinfectants.
What types of infections do nonfermenters cause?
Nonfermenters rarely cause infections outside of the hospital environment, except when traumatically implanted (e.g., into the skin from soil, vegetation, or water sources) or in the case of immunocompromised patients. In the hospital, nonfermenters may be the cause of nosocomial urinary tract infections, postsurgical wound infections, pneumonia (particularly ventilator-associated pneumonia), and/ or bacteremia. The incidence of infection is greater in the immunocompromised patient.
What risk factors are associated with infections caused by nonfermentative, gram-negative bacilli?
Risk factors for infection by nonfermenters include immunocompromised states from cancer or cancer chemotherapy, transplantation, and steroid use. In the immunocompetent individual, infections are associated with burns, catheters, prior use of broad-spectrum antimicrobial agents, metabolic disorders (e.g., diabetes mellitus), and foreign body implantation, traumatically or via transplanted organs.
What are the four most common nonfermentative, gram-negative bacilli isolated in the clinical laboratory?
Pseudomonas aeruginosa is the most common nonfermenter associated with clinical infections, especially nosocomial infections. Acinetobacter baumannii complex, Burkholderia spp., and Stenotrophomonas maltophilia are often isolated from hospitalized patients, especially from respiratory specimens, but they are more often colonizers and are not always clinically significant. The isolation of a nonfermenter from a single blood culture, or as part of a polymicrobial infection, often indicates that the organism is acting as a colonizer or a laboratory contaminant rather than a relevant pathogen. However, if one of the nonfermenters is seen on a Gram stain from a sterile site, is the only organism isolated, and is present in high numbers, its clinical significance needs to be considered.