Spore-forming Gram-positive Bacilli Flashcards
are found in the soil
Spores
remain viable in soil for decades. Although spores are naturally in soil from around the world, the organisms are not regularly cultivated from soils.
Spores
Animals, esp. livestock (?), become infected while grazing on grass contaminated with spores which germinate.
goats, sheep, cattle, horses
The vegetative cells multiply and elaborate toxins, which spread in the body cause fatal (?). When the organisms are returned to the soil in animal excrement or carcasses, they sporulate and become a long-term reservoir of infection.
septicemia and toxemia
Transmission to humans is by
direct inoculation, ingestion, or inhalation of spores
Most common form of anthrax in humans, accounting for more than 95% of cases, but the least dangerous form
Cutaneous Anthrax (malignant pustule)
Acquired by inoculation of spores through cut or abrasion of the skin, either from soil or infected animal products
Cutaneous Anthrax (malignant pustule)
begins with a small, itchy lesion resembling an insect bite; in 1-2 days, it develops into a non-painful papule that changes rapidly into a vesicle, then a pustule filled with blue-black edema fluid.
Cutaneous Anthrax (malignant pustule) : Signs and symptoms: Skin infection
blackened crater, typically 1-3 cm in diameter, surrounded by edem.
“black eschar”
Cutaneous Anthrax (malignant pustule) : Signs and symptoms
Lymphangitis and lymphadenopathy
Cutaneous Anthrax (malignant pustule) : Signs and symptoms
fever, malaise, and headache may occur.
is fully developed. Eventually, it dries, loosens, and separates; healing is by granulation and leaves a scar. It may take many weeks for the lesion to heal and the edema to subside.
Eschar
Can lead to sepsis, the consequences of systemic infection—including meningitis—and death in 20% of untreated cases.
Cutaneous Anthrax (malignant pustule)
Extremely rare in humans (accounts for less than 1% of cases)
Gastrointestinal Anthrax (violent enteritis)
Acquired from ingestion of the organism’s spores from contaminated or uncooked meat.
Gastrointestinal Anthrax (violent enteritis)
Characterized by an acute inflammation of the intestinal tract.
Gastrointestinal Anthrax (violent enteritis)
Death occurs in 60% of untreated cases.
Gastrointestinal Anthrax (violent enteritis)
Gastrointestinal Anthrax (violent enteritis) : Signs and symptoms:
- Initially, nausea, loss of appetite, vomiting, and fever
- Followed by abdominal pain, vomiting of blood, and severe (often bloody) diarrhea.
Acquired by inhalation of airborne spores while handling animal products
Pulmonary or Inhalation Anthrax (Woolsorter’s disease)
it develops in handlers of raw animal hair, wool or hides
Pulmonary or Inhalation Anthrax (Woolsorter’s disease)
The incubation period in inhalation anthrax may be as long as 6 weeks.
Pulmonary or Inhalation Anthrax (Woolsorter’s disease)
The fatality rate in inhalation anthrax is high in the setting of known exposure
Pulmonary or Inhalation Anthrax (Woolsorter’s disease)
it is higher when the diagnosis is not initially suspected.
Pulmonary or Inhalation Anthrax (Woolsorter’s disease)
- First symptoms are flu- or common cold-like symptoms including a sore throat, mild fever, and muscle aches.
- Followed by coughing, chest discomfort, shortness of breath, and tiredness — which are manifestations of toxemia, marked hemorrhagic necrosis, edema of the mediastinum, and substernal pain. Sepsis occurs, and there may be hematogenous spread to the gastrointestinal tract, causing bowel ulceration, or to the meninges, causing hemorrhagic meningitis.
Pulmonary or Inhalation Anthrax (Woolsorter’s disease):
Signs and symptoms
has been considered as an agent for bioterrorism. It has been classified as Category A (highest priority) biological agent because it is easily disseminated, can cause high mortality, and can generate public panic.
B. anthracis
Occurs after the intravenous injection of drugs contaminated with spores
Injectional anthrax
May result to soft tissue infections, may result in death of shock, coma, organ failure, and necrotizing fasciitis.
Injectional anthrax
Found in virulent strains of B. anthracis.
Capsule
Consists mainly of a polypeptide, poly-D-glutamic acid
Capsule
Instrumental in the adherence of the organism to host’s cells and tissue and is an anti-phagocytic factor.
Capsule
Antibodies formed against the capsule do not protect against the disease.
Capsule
Plasmid-encoded protein complex made up of 3 components
Anthrax exotoxins
binds to specific cell receptors, and after proteolytic activation, it forms a membrane channel that mediates entry of EF and LF into the host’s cell.
Protective antigen (PA)
It is so called because it induces protective antitoxins
Protective antigen (PA)
is an adenylate cyclase.
Edema factor (EF)
Together with PA, it forms a toxin known as edema toxin.
Edema factor (EF)
This most likely impairs host defenses and is responsible for the fluid accumulation seen in anthrax.
Edema factor (EF)
combines with PA to form lethal toxin, responsible for cytolysis of macrophages.
Lethal factor (LF)
This is a major virulence factor and cause of death in infected animals and humans. When injected into laboratory animals (eg, rats), the lethal toxin can quickly kill the animals.
Lethal factor (LF)
Control soil contamination is key to preventing anthrax, measures include:
(1) disposal of animal by burning or by deep burial in lime pits (2) decontamination (usually by autoclaving) of animal products (3) protective clothing and gloves for handling potentially infected materials
(4) active immunization of domestic animals with live attenuated vaccines
Vaccination is recommended for the following high-risk groups:
(1) laboratory workers handling the B. anthracis routinely
(2) persons who handle potentially infected animals/animal products (e.g., hides and furs) esp. in high incidence areas
(3) military personnel deployed to areas with high risk for exposure
The first-generation human vaccine to be licensed for use in the United States
BioThrax
a cell-free formulation prepared from a culture filtrate of a toxigenic, nonencapsulated, avirulent strain of B. anthracis , which contains PA, LF, and EF, with PA being the major component.
BioThrax
It consists of 3 subcutaneous injections given 2 weeks apart, followed by 3 additional SC injections given at 6, 12, and 18 months; annual booster injections are recommended thereafter to maintain protective level of immunity.
BioThrax
Two vaccines using highly purified recombinant (?) have been manufactured in the United States and the United Kingdom.
PA (rPA)
is recommended in the setting of potential exposure to B. anthracis as an agent of biologic warfare
Chemoprophylaxis
Similar to B. anthracis, but B. cereus are motile with peritrichous flagella, and are non-encapsulated.
Bacillus cereus
Spores are found in the soil (also considered as an airborne and dust-borne contaminant that multiplies very readily in cooked foods such as rice, potato, and meat dishes)
Bacillus cereus: HABITAT
Transmission to humans is by ingestion or direct inoculation.
Bacillus cereus: TRANSMISSION
Food poisoning
•Has two distinct forms:
Emetic form
Diarrheal form
Associated with eating fried rice, and occasionally, pasta dishes that are contaminated with the organism’s toxin.
Emetic form
Has incubation period of 1–6 hours
Emetic form
Manifestations include nausea, vomiting, abdominal cramps, and occasionally diarrhea (clinically resembles staphylococcal food poisoning)
Emetic form
Recovery occurs within 24 hours after the onset.
Emetic form
Associated with meat dishes and sauces contaminated with spores
Diarrheal form
Has an incubation period of 8-16 hours
Diarrheal form
Manifestations include profuse diarrhea with abdominal pain and cramps; fever and vomiting are uncommon (clinically resembles C. perfringens food poisoning)
Diarrheal form
Recovery occurs within 12 hours after the onset.
Diarrheal form
Occurs when the organisms are introduced into the eye by foreign bodies in association with trauma.
Eye Infections
Clinical presentation may be in the form of severe keratitis, endophthalmitis, and panophthalmitis.
Eye Infections
B. cereus has also been associated with localized infections and with systemic infections, including:
endocarditis, meningitis, osteomyelitis, and pneumonia.
are released during spore germination, and may be preformed in the food or produced in the intestine.
Enterotoxins
Responsible for the clinical presentation of the emetic form of the disease.
Heat-stable enterotoxin
Produced when spores survive cooking rice, and keeping the rice warm results in germination of spores and enterotoxin formation
Heat-stable enterotoxin
this pre-formed toxin remains in the food despite reheating.
Heat-stable enterotoxin
Responsible for the clinical presentation of the diarrheal form of the disease. •Produced after ingestion of the B. cereus spore-contaminated vegetables,
Heat-labile enterotoxin
Produced after ingestion of the B. cereus spore-contaminated vegetables, meat, and cream sauces.
Heat-labile enterotoxin
Acute diarrheal disease caused by B. cereus may be prevented by?
proper cooking and refrigeration of foods prepared in bulk to prevent proliferation of vegetative forms of the bacteria and formation of the enterotoxin.
may be gram-variable on prolonged incubation.
Gram-positive bacilli
Spores are larger than the diameter of the organism in which they are formed; may be placed centrally, subterminally, or terminally.
Spore-forming
Sporangia are swollen.
Spore-forming
Most are motile with peritrichous flagella EXCEPT
C. perfringens, C. innocuum, C. ramosum
Groups of anaerobes based on aerotolerance test: Each colony type from the anaerobic isolation plate is subcultured to an aerobic (5% to 10% CO2) and anaerobic blood agar plate for overnight incubation.
Anaerobic
NOT capable of growth on agar surfaces exposed to O2 levels above 0.5%.
Strict obligate anaerobes
e.g., C. heamolyticum, C. novyi type B, C. tetani, C. botulinum, Clostridioides (formerly Clostridium) difficile
Strict obligate anaerobes
- Can grow when exposed to oxygen levels ranging from about 2% to 8% (average, 3%) e.g., C. perfringens
Moderate obligate anaerobes
Show limited or scant growth on agar in room air or in a 5% to 10% CO2 incubator, but grow best under anaerobic conditions.
Aerotolerant anaerobes
e.g., C. histolyticum, C. tertium and C. carnis
Aerotolerant anaerobes
Catalase (-)
CLOSTRIDIUM SPECIES
Can be part of the normal flora of the GI tract; these are clinically relevant as the cause of both endogenous and exogenous infections.
CLOSTRIDIUM SPECIES
causes 80% of gas gangrene (myonecrosis)
C. perfringens