Aerobic Gram positive Bacilli Flashcards
What are Aerobic Gram-Positive Bacilli?
Species of bacteria in the genera:
* Bacillus spp.
* Nocardia spp.
* Actinomyces spp.
* Streptomyces spp.
What are the general characteristics of Bacillus spp.?
Gram-positive, rod-shaped, aerobic, spore-forming
Where can species of Bacillus be found?
Widely in the environment (i.e., soil and water of all climates)
What distinguishes Moraxella catarrhalis from Neisseria species?
Similar morphology and biochemistry, but not part of the Neisseriaceae family
Is Neisseria gonorrhoeae always pathogenic?
Yes
Can Neisseria meningitidis be a commensal inhabitant?
Yes, in the upper respiratory tract of carriers
What are the key characteristics of Bacillus anthracis?
Forms spores aerobically, catalase positive, non-motile, ferments glucose, produces lecithinase
What are the virulence factors of Bacillus anthracis?
Capsule of D glutamic acid, complex anthrax toxin (edema factor, protective antigen, lethal factor)
What are the three human forms of anthrax?
- Cutaneous
- Inhalation (pulmonary)
- Gastrointestinal
What complications can arise from anthrax?
Meningitis (5% of anthrax cases)
What microscopy characteristics are observed for Bacillus anthracis?
Large, square-ended rods with internal clear areas, Gram-positive or variable
How do Bacillus anthracis colonies appear on blood agar?
Nonhemolytic, large, grey, flat with an irregular margin (resembling ‘Medusa Head’)
What are the presumptive identification criteria for Bacillus anthracis?
- Non-hemolytic
- Non-motile
- Produces lecithinase
What is the significance of a ‘string of pearls’ appearance in microscopy?
Presumptive identification for Bacillus anthracis
What are the two forms of food poisoning caused by Bacillus cereus?
- Diarrheal Syndrome
- Emetic Form
What is a common characteristic of Bacillus cereus colonies?
β-hemolytic, frosted-glass appearance, aerobic, spore-forming, Gram-positive, motile
What is the primary cause of opportunistic eye infections related to Bacillus?
Bacillus cereus
True or False: Bacillus anthracis is motile.
False
Fill in the blank: Bacillus anthracis is susceptible to _______.
penicillin
What is Bacillus cereus classified as?
Aerobic Gram-Positive Bacilli
What is a common contaminant among Bacillus species?
Bacillus subtilis
What systems can be used for the identification of Bacillus species?
API 20E or 50CH systems
Which genera consist of aerobic actinomycetes?
Nocardia and Actinomyces
What is a characteristic morphology of Actinomycetes?
Filamentous hyphae
What is the typical Gram stain appearance for Nocardia?
Gram-positive with branching filaments
What is a possible appearance due to a weak or irregular Gram stain?
Beading appearance
What is the cultural characteristic of Nocardia colonies?
Chalky or velvety in appearance
Is Nocardia partially acid-fast?
Yes
What are the general characteristics of Corynebacterium species?
Found as free-living saprophytes, human and animal pathogens
Corynebacterium diphtheriae is the most significant pathogen. Other species may cause infections in immunocompromised hosts.
Describe the morphology of C. diphtheriae on stained smears.
Palisading or individual cells may form V or L arrangements, with common ‘club’ and ‘beaded’ forms
C. diphtheriae is facultatively anaerobic and ferments glucose and maltose.
What is the virulence factor of C. diphtheriae?
Exotoxin, specifically diphtheria toxin
C. ulcerans and C. pseudotuberculosis can also produce the exotoxin.
What does Tinsdale agar indicate for C. diphtheriae?
Produces gray to black colonies with brown halos
This agar is useful for differentiating C. diphtheriae from other species.
What is the significance of Corynebacterium jeikeium?
Linked to infections in patients with prosthetic devices or catheterization
Can cause nosocomial septicemia, bacteremia, pneumonia, and meningitis.
What are the biochemical characteristics of Corynebacterium jeikeium?
Catalase positive, nitrate negative, urea negative
It oxidatively utilizes glucose and is pyrazinamidase positive.
What is the clinical significance of Corynebacterium urealyticum?
A urinary tract pathogen in immunocompromised and catheterized individuals
It is associated with non-hemolytic colonies.
Describe the general characteristics of Listeria monocytogenes.
Gram-positive, aerobic, non–spore-forming coccobacillus
It is widespread in nature and the only human and animal pathogen of its kind.
What are the clinical manifestations of Listeria infection in pregnant women?
Mild flu-like illness, potential for premature labor and septic abortion
Infection may lead to granulomatosis infantiseptica in the fetus.
What is the most common presentation of Listeria infection in healthy hosts?
Meningitis
Infection is often associated with ingestion of contaminated food.
What are the cultural characteristics of Listeria monocytogenes?
Produces a narrow zone of hemolysis similar to Group B streptococcus
Differentiation includes catalase positive and negative hippurate hydrolysis test.
