Title: Gram-Positive Bacilli: Spore-formers Chapter 17 Bacillus
1Gram-Positive Bacilli Spore-formers Chapter 17
2Bacillus Species General Characteristics
- Gram-positive spore-formers vs. nonspore-formers
Corynebacterium sp. (no spores)
Bacillus sp. (spore-forming)
3Bacillus species General Characteristics
- Found in nature, from the arctic to the desert
- Aerobic
- Most are saprophytic and are isolated as
contaminants - Bacillus anthracis is a major pathogen
- Others are opportunists
Bacillus sp. stained with spore stain
4Gram-Positive Bacilli Spore-formers
- Spores are produced when the bacteria get
stressed (i.e. drying, temp.) - Heat shock (heat to 56o) will induce spore
formation - On gram stain, appear as clear areas within the
bacterial cell - Spores aid in the survival of the bacteria
5Significant Bacillus Species
- Bacillus anthracis
- Agent of anthrax, a disease in livestock
- Humans acquire infection by contamination of
wound or ingestion or inhalation of spores - Bacillus cereus
- Causes food poisoning, frequently from left-over
rice - An opportunist
- Bacillus subtilis
- Common laboratory contaminant
6Bacillus anthracis General Characteristics
- Morphology (might resemble Clostridium, except
for being aerobic and catalase ) - Large, sporeforming gram-positive to
gram-variable bacilli - Spores viable for up to 50 years
- Nonhemolytic on sheep blood agar (this
characteristic differentiates B. anthracis from
other Bacillus spp.) - Catalase
- Some strains produce pink to blue-black pigment
7Virulence Factors
- Virulence factors work together to produce
damage - Polypeptide capsule
- Potent exotoxins
8Bacillus anthracis
Clinical Infections in Humans
- Cutaneous anthrax or "malignant pustule (also
called black escher) - Organisms gain access through cuts localized
infection - Majority of cases in the world are cutaneous
- Pulmonary anthrax or "woolsorter's disease
- Acquired through inhalation of spores may result
in respiratory distress and death - Gastrointestinal
- Acquired by ingestion of contaminated raw meat
- Usually fatal
9Bacillus anthracis
Clinical Infections in Humans
10Anthrax Complications and Treatment
- Fatality rate of gastrointestinal form is highest
although rare - Meningitis may occur in 5 of cases
- Antibiotic therapy penicillin in high doses or
ciprofloxacin (cipro) - Vaccination is available to those with high risk
of exposure
11Laboratory Diagnosis
- Goal in identification is to RULE OUT B.
anthracis - If B. anthracis is suspect, MUST work under
safety hood
12Laboratory Diagnosis Bacillus anthracis
- Microscopic morphology
- Gram stain large, square-ended
gram-positive/gram- variable rods may appear
end-to-end giving a "bamboo appearance
- Colonial morphology
- Nonhemolytic on 5 blood agar raised, large,
grayish-white, irregular, fingerlike edges
described as Medusa head or beaten egg whites
(colony stands upright when lifted with loop)
13Laboratory Diagnosis Bacillus anthracis
- B. anthracis in a gram stain from a cutaneous
lesion
14Laboratory Diagnosis Bacillus anthracis
- B. anthracis colonies showing finger-like edges
and beaten egg whites consistency
15Other Bacillus species B. cereus
- Food poisoning (can be cultured from stool or
vomitus) - Diarrheal syndrome
- Associated with meat, poultry, and soups
- Incubation period of 8 to16 hours
- Fever uncommon
- Resolves within 24 hours
- Emetic form
- Associated with fried rice
- Abdominal cramps and vomiting
- Incubation period of 1 to 5 hours
- Resolves in 9 hours
16Other Bacillus species B. cereus
- Other than B. anthracis, all Bacillus spp. are
HEMOLYTIC on blood agar - All Bacillus spp. produce spores and are aerobic
- Infections in the immunosuppressed hosts
- Opportunistic infections of the eye
- Meningitis, septicemia, and osteomyelitis
- Found as contaminants in drug paraphernalia
17Other Bacillus species
- Bacillus subtilis
- Common laboratory contaminant
B. cereus colony on blood agar Large, ß-
hemolytic colony
18Laboratory Identification Bacillus anthracis
19 20Aerobic ActinomycetesNocardia species
- General Characteristics
- Aerobic, gram-positive, filamentous rods,
sometimes resembling branched hyphae - Weakly acid-fast and may stain gram-variable
- Morphologically resemble fungi, both in culture
and in types of infections produced, but is a
true bacteria - Generally found in the environment (primarily
soil) and mostly affect immunocompromised
individuals
21Aerobic Actinomycetes Nocardia, Actinomadura,
and Streptomyces species
- Significant Nocardia species (majority isolated
from sputum and wounds) - N. asteroides
- N. braziliensis
- N. caviae
- Actinomadura species
- A. madurae
- A. pelletieri
- Streptomyces species
22Aerobic Actinomycetes Nocardia, Actinomadura,
and Streptomyces species
- Clinical infections
- Pulmonary form
- Mostly in immunocompromised
- High fatality
- Starts as lung lesion
- Mycetomas
- Cutaneous
- Invasive
- Gram stain can show sulfur granules (masses of
organisms may be yellow or orange)
Sulfur granules collected from draining sinus
tracts in mycetoma
23Laboratory Diagnosis Nocardia, Actinomadura, and
Streptomyces species
- Microscopy
- Gram-positive branching filaments are seen in
direct smears from sputum or aspirated material - May show beading appearance
- Verify with acid fast stain
Gram-stained smear of sputum showing
Gram-positive branched beaded bacilli.
24Laboratory Diagnosis Nocardia, Actinomadura, and
Streptomyces species
- Expectorated sputum with purulence
- Gram-positive filamentous bacilli
- Suspicious for actinomycetes
25Laboratory Diagnosis Nocardia, Actinomadura, and
Streptomyces species
26Laboratory Diagnosis Nocardia, Actinomadura, and
Streptomyces Species
- Cultural characteristics
- Chalky, matte, dry, crumbly appearance
- May be pigmented
- Identification
- Utilization of carbohydrates
- Hydrolysis of casein, tyrosine, and xanthine
Chalky, white colonies on blood agar plate
isolated from sputum sample consistent with
Nocardia sp. or Streptomyces sp.
27Streptomyces
- Species
- Streptomyces somaliensis
- Streptomyces anulatus
- Streptomyces paraguayensis
- Habitat
- Soil and decaying vegetation
- Disease states
- Mycetoma- a chronic, localized, painless,
subcutaneous infection
28Streptomyces
- Morphology Characteristics
- Aerobic growth in 3-30 days
- Waxy, bumpy or velvety rugose forms, yellow to
orange - Will grown on SBA, mycology media and LJ media
- GPR with extensive branching, chains and spores
- Identification
- Acid-fast negative
29Laboratory Diagnosis Nocardia, Actinomadura, and
Streptomyces Species
- Sputum smear, partially acid-fast bacilli,
consistent with Nocardia sp. - Actinomadura and Streptomyces sp. are not
acid-fast