Question 1

Which of the following groups of bacteria have Clinical Laboratory Standards Institute (CLSI)guidelines that describe specific testing methods and interpretative standards for susceptibility reporting?
A)A.facilis and Stenotrophomonas maltophilia
B)P.fluorescens and R.mannitolilytica
C)P.aeruginosa and B.pseudomallei
D)B.cepacia and B.vesicularis

Accepted Answer

The Clinical Laboratory Standards Institute (CLSI)guidelines describe specific testing methods (e.g. ,disk diffusion and minimal inhibitory concentration)and provide interpretative standards for susceptibility reporting of P.aeruginosa,B.cepacia,S.maltophilia in the CLSI M100 series document.Guidelines for minimal inhibitory concentration assays for other non-Enterobacteriaceae isolates,including Pseudomonas spp.other than P.aeruginosa,can be found in the same document.Testing methods for more fastidious organisms,such as B.pseudomallei and B.mallei,are published in the CLSI M45 series document.See Chapter 12 for more information.

Question 2

Which combination of nonfermenting gram-negative bacilli are oxidase positive,but do not grow on MacConkey agar within 24 to 48 hours.
A)B.cepacia and Pseudomonas stutzeri
B)Brevundimonas dimunuta and Pseudomonas veronii
C)P.aeruginosa and R.insidiosa
D)B.vesicularis and Acidovorax facilis

Accepted Answer

All organisms featured in Chapter 22 usually grow on MacConkey agar,except B.vesicularis and A.facilis.All genera also grow well in broth-blood culture systems and common nutrient broths,such as thioglycollate and brain-heart infusion.

Question 3

PC agar is a selective media for isolation of B.cepacia.What is the purpose of the polymixin B and ticarcillin in the media?
A)They provide nutrients to enrich the growth of B.cepacia.
B)They cause color change in the media from yellow to pink.
C)They inhibit growth of gram-positive and other gram-negative organisms.
D)They stabilize the media to support growth if prolonged incubation is needed.

Accepted Answer

PC agar is a selective and differential media designed to enrich the growth of B.cepacia from respiratory specimens from CF patients.PC agar contains crystal violet,bile salts,polymyxin B,and ticarcillin to inhibit gram-positive and rapid-growing,gram-negative organisms.Inorganic and organic components,including pyruvate and phenol red,also are added.B.cepacia breaks down the pyruvate,creating an alkaline pH and resulting in a color change of the pH indicator (phenol red)from yellow to pink.

Question 4

Preferred samples for plating onto Ashdown media include throat,rectal,or sputum samples.Disease presentation can range from subclinical to disseminated disease.This infection is endemic in Southeast Asia.Which organism is being sought?
A)B.cepacia
B)Burkholderia gladioli
C)B.mallei
D)B.pseudomallei

Accepted Answer

Ashdown medium is used to isolate B.pseudomallei when melioidosis is suspected.Preferred specimens include throat,rectal,or sputum samples.The medium contains crystal violet and gentamicin as selective agents to suppress the growth of contaminating organisms.Neutral red is incorporated into the medium and is taken up by the organism,making the dry,wrinkled colony appear violet-purple,which distinguishes it from other bacteria.

Question 5

The following species,P.aeruginosa,P.fluorescens,Pseudomonas putida,P.veronii,Pseudomonas monteilii,and Pseudomonas mosselii,all produce a water-soluble,yellow-green pigment called:
A)pyocyanin.
B)pyomelanin.
C)pyorubrum.
D)pyoverdin.

Accepted Answer

P.aeruginosa,P.fluorescens,P.putida,P.veronii,P.monteilii,and P.mosselii comprise the group known as the fluorescent pseudomonads.These species all produce pyoverdin,a water-soluble,yellow-green or yellow-brown pigment that fluoresces under UV illumination.P.aeruginosa is the only species that produces pyocyanin.

Quiz 20: Pseudomonas, Burkholderia, and Similar Organisms

Which of the following groups of bacteria have Clinical Laboratory Standards Institute (CLSI) guidelines that describe specific testing methods and interpretative standards for susceptibility reporting?

Which combination of nonfermenting gram-negative bacilli are oxidase positive,but do not grow on MacConkey agar within 24 to 48 hours.

PC agar is a selective media for isolation of B.cepacia.What is the purpose of the polymixin B and ticarcillin in the media?

Preferred samples for plating onto Ashdown media include throat,rectal,or sputum samples.Disease presentation can range from subclinical to disseminated disease.This infection is endemic in Southeast Asia.Which organism is being sought?

The following species,P.aeruginosa,P.fluorescens,Pseudomonas putida,P.veronii,Pseudomonas monteilii,and Pseudomonas mosselii,all produce a water-soluble,yellow-green pigment called: