Aerobic Gram positive Bacilli

Question 1

What are Aerobic Gram-Positive Bacilli?

Answer 1

Species of bacteria in the genera:
* Bacillus spp.
* Nocardia spp.
* Actinomyces spp.
* Streptomyces spp.

Question 2

What are the general characteristics of Bacillus spp.?

Answer 2

Gram-positive, rod-shaped, aerobic, spore-forming

Question 3

Where can species of Bacillus be found?

Answer 3

Widely in the environment (i.e., soil and water of all climates)

Question 4

What distinguishes Moraxella catarrhalis from Neisseria species?

Answer 4

Similar morphology and biochemistry, but not part of the Neisseriaceae family

Question 5

Is Neisseria gonorrhoeae always pathogenic?

Answer 5

Yes

Question 6

Can Neisseria meningitidis be a commensal inhabitant?

Answer 6

Yes, in the upper respiratory tract of carriers

Question 7

What are the key characteristics of Bacillus anthracis?

Answer 7

Forms spores aerobically, catalase positive, non-motile, ferments glucose, produces lecithinase

Question 8

What are the virulence factors of Bacillus anthracis?

Answer 8

Capsule of D glutamic acid, complex anthrax toxin (edema factor, protective antigen, lethal factor)

Question 9

What are the three human forms of anthrax?

Answer 9

• Cutaneous
• Inhalation (pulmonary)
• Gastrointestinal

Question 10

What complications can arise from anthrax?

Answer 10

Meningitis (5% of anthrax cases)

Question 11

What microscopy characteristics are observed for Bacillus anthracis?

Answer 11

Large, square-ended rods with internal clear areas, Gram-positive or variable

Question 12

How do Bacillus anthracis colonies appear on blood agar?

Answer 12

Nonhemolytic, large, grey, flat with an irregular margin (resembling ‘Medusa Head’)

Question 13

What are the presumptive identification criteria for Bacillus anthracis?

Answer 13

• Non-hemolytic
• Non-motile
• Produces lecithinase

Question 14

What is the significance of a ‘string of pearls’ appearance in microscopy?

Answer 14

Presumptive identification for Bacillus anthracis

Question 15

What are the two forms of food poisoning caused by Bacillus cereus?

Answer 15

• Diarrheal Syndrome
• Emetic Form

Question 16

What is a common characteristic of Bacillus cereus colonies?

Answer 16

β-hemolytic, frosted-glass appearance, aerobic, spore-forming, Gram-positive, motile

Question 17

What is the primary cause of opportunistic eye infections related to Bacillus?

Answer 17

Bacillus cereus

Question 18

True or False: Bacillus anthracis is motile.

Answer 18

False

Question 19

Fill in the blank: Bacillus anthracis is susceptible to _______.

Answer 19

penicillin

Question 20

What is Bacillus cereus classified as?

Answer 20

Aerobic Gram-Positive Bacilli

Question 21

What is a common contaminant among Bacillus species?

Answer 21

Bacillus subtilis

Question 22

What systems can be used for the identification of Bacillus species?

Answer 22

API 20E or 50CH systems

Question 23

Which genera consist of aerobic actinomycetes?

Answer 23

Nocardia and Actinomyces

Question 24

What is a characteristic morphology of Actinomycetes?

Answer 24

Filamentous hyphae

Question 25

What is the typical Gram stain appearance for Nocardia?

Answer 25

Gram-positive with branching filaments

Question 26

What is a possible appearance due to a weak or irregular Gram stain?

Answer 26

Beading appearance

Question 27

What is the cultural characteristic of Nocardia colonies?

Answer 27

Chalky or velvety in appearance

Question 28

Is Nocardia partially acid-fast?

Answer 28

Yes

Question 29

What are the general characteristics of Corynebacterium species?

Answer 29

Found as free-living saprophytes, human and animal pathogens ## Footnote Corynebacterium diphtheriae is the most significant pathogen. Other species may cause infections in immunocompromised hosts.

Question 30

Describe the morphology of C. diphtheriae on stained smears.

Answer 30

Palisading or individual cells may form V or L arrangements, with common 'club' and 'beaded' forms ## Footnote C. diphtheriae is facultatively anaerobic and ferments glucose and maltose.

Question 31

What is the virulence factor of C. diphtheriae?

Answer 31

Exotoxin, specifically diphtheria toxin ## Footnote C. ulcerans and C. pseudotuberculosis can also produce the exotoxin.

Question 32

What does Tinsdale agar indicate for C. diphtheriae?

Answer 32

Produces gray to black colonies with brown halos ## Footnote This agar is useful for differentiating C. diphtheriae from other species.

Question 33

What is the significance of Corynebacterium jeikeium?

Answer 33

Linked to infections in patients with prosthetic devices or catheterization ## Footnote Can cause nosocomial septicemia, bacteremia, pneumonia, and meningitis.

Question 34

What are the biochemical characteristics of Corynebacterium jeikeium?

Answer 34

Catalase positive, nitrate negative, urea negative ## Footnote It oxidatively utilizes glucose and is pyrazinamidase positive.

Question 35

What is the clinical significance of Corynebacterium urealyticum?

Answer 35

A urinary tract pathogen in immunocompromised and catheterized individuals ## Footnote It is associated with non-hemolytic colonies.

Question 36

Describe the general characteristics of Listeria monocytogenes.

Answer 36

Gram-positive, aerobic, non–spore-forming coccobacillus ## Footnote It is widespread in nature and the only human and animal pathogen of its kind.

Question 37

What are the clinical manifestations of Listeria infection in pregnant women?

Answer 37

Mild flu-like illness, potential for premature labor and septic abortion ## Footnote Infection may lead to granulomatosis infantiseptica in the fetus.

Question 38

What is the most common presentation of Listeria infection in healthy hosts?

Answer 38

Meningitis ## Footnote Infection is often associated with ingestion of contaminated food.

Question 39

What are the cultural characteristics of Listeria monocytogenes?

Answer 39

Produces a narrow zone of hemolysis similar to Group B streptococcus ## Footnote Differentiation includes catalase positive and negative hippurate hydrolysis test.