Question 1

Induction of capsule formation by B.anthracis can be accomplished with _____ agar.

Accepted Answer

As a means of identification,bicarbonate agar is used to induce B.anthracis capsule formation.

Question 2

Which of the following types of anthrax occurs after ingesting the spores and affects the abdominal or oropharyngeal area? (Patients usually die from toxemia and overwhelming sepsis. )

Accepted Answer

Gastrointestinal anthrax can be fatal as a result of toxemia and an overwhelming sepsis that cannot be controlled.

Question 3

Media that can be used for isolating Bacillus anthracis include:

Accepted Answer

All Bacilli and related genera grow well on 5% sheep blood agar,chocolate agar,routine blood culture media,and commonly used nutrient broths.They will not grow on MacConkey agar,and those that are susceptible to nalidixic acid will not grow on Columbia blood agar with CNA.Two special media are used for the isolation and identification of B.anthracis.Polymyxin-lysozyme-ethylenediaminetetraacetic-thallous (PLET)acetate can be used for the selection and isolation of this species from contaminated specimens.As a means of identification,bicarbonate agar is used to induce B.anthracis capsule formation.

Question 4

Suspect spore-forming,gram-positive Bacillus species that is γ-hemolytic,nonmotile,and penicillin-susceptible and that produces a wide zone of lecithinase on egg yolk agar can be identified as:

Accepted Answer

B.anthracis should be suspected if typical γ-hemolytic "Medusa head" colonies are observed on 5% sheep blood agar and if the organism is subsequently found to be nonmotile and lecithinase-positive.

Question 5

The microbiologist identified an organism that produces large γ-hemolytic colonies on blood agar and appears as a gram-variable rod on Gram staining.In order to further identify the organism,the microbiologist should:

Accepted Answer

Based on the information presented in the question,the microbiologist should complete a biochemical identification and an antibiotic susceptibility.At this point,the type of isolate is unknown and therefore,it is important to identify the species to determine the antibiotic pattern.If the organism is indeed B.anthracis,some strains produce β-lactamases.CLSI has published technical guidelines and interpretive criteria for testing Bacillus spp.

Question 6

Induction of sporulation by Bacillus species can be accomplished with _____ agar.

Accepted Answer

To induce sporulation,organisms can be grown on triple sugar iron (TSI)agar,urea agar,or nutrient agar containing 5 mg/L of manganese sulfate.On Gram-stained smears,spores appear clear because they do not retain the crystal violet or safranin.However,spores will stain with specific dyes such as malachite green that is forced into the spore using heat;the vegetative cell is then counterstained with safranin.

Question 7

Enzyme-linked immunosorbent assays (ELISAs)are available that can serologically identify which Bacillus species?

Accepted Answer

Indirect hemagglutination and ELISAs are available to detect antibodies to B.anthracis.

Question 8

A patient diagnosed with B.anthracis is allergic to penicillin.Which antibiotic can be given that will be therapeutically effective?

Accepted Answer

Ciprofloxacin or doxycycline plus one or two other antibiotics is an alternative choice for treatment if a patient is allergic to penicillin.

Question 9

Which of the following is described as a spore-forming,gram-positive Bacillus that is β-hemolytic,motile,Voges-Proskauer (VP)-positive,and citrate-positive and causes two types of food poisoning as a result of toxin release?

Accepted Answer

B.cereus is another important species to identify.It is resistant to penicillin,β-hemolytic,and motile,and it produces a wide zone of lecithinase on egg yolk agar.

Question 10

A U.S.Food and Drug Administration (FDA)-cleared immunochromatographic test produces a red line on the cassette and can presumptively identify which gram-positive Bacillus that is g-hemolytic and morphologically has a "Medusa head" appearance when grown on 5% sheep blood agar?

Accepted Answer

An immunochromatographic test is available for B.anthracis,which is γ-hemolytic and morphologically has a "Medusa head" appearance when grown on 5% sheep blood agar.

Question 11

A gram-positive Bacillus,which is β-hemolytic on 5% sheep blood agar,produces a wide zone of lecithinase on egg yolk agar,is nonmotile,and was isolated from the stool of a patient with abdominal pain and watery diarrhea.Because of the patient's existing immunocompromised state,the physician administered penicillin as the antibiotic therapy.The patient's condition did not improve after 7 days of treatment.Which one of the following statements explains the reason for the antibiotic failure?

Accepted Answer

B.anthracis produce β-lactamase;therefore penicillin and all derivatives would be an ineffective treatment,regardless of how long the antibiotic would be administered.

Quiz 14: Bacillus and Similar Organisms