Pathogenic Gram-Positive Bacillus

Bacillus anthracis

primarily a disease of herbivores that humans can contract from infected animals

Three routes of entry for Bacillus anthracis

1)inhalation of spores

2)inoculation of spores into the body through a break in the skin

3)ingestion of spores

Virulence factors of Bacillus anthracis

capsule and anthrax toxin (exotoxin that causes edema and cell death)

Diseases caused by Bacillus anthracis

gastrointestinal anthrax, cutaneous anthrax, and inhalation anthrax

Gastrointestinal anthrax

*Bacillus anthracis*

intestinal hemorrhaging that lead to death, rare in humans

Cutaneous anthrax

*Bacillus anthracis*

produces ulcers called an eschar and toxemia

Inhalation anthrax

*Bacillus anthracis*

spores germinate in the lungs and secret toxins that are absorbed into the bloodstream, rare in humans

Diagnosis of Bacillus anthracis

the presence of large, nonmotile, gram-positive bacilli in the clinical samples of the lungs or skin

Treatment of Bacillus anthracis

ciproflaxacin and many other antimicrobials are effective

Prevention of Bacillus anthracis

control the disease in animals and the anthrax vaccine is available but it is a toxoid vaccine that requires multiple boosters

Clostridium (genus)

found in soil, water, and GI tracts of animals and human, forms endospores allow for survival in harsh conditions

Clostridium perfringens

commonly grown in the digestive tract of animals and humans

Virulence factor of Clostridium perfringens

produces 11 toxins that have various effects on the body and can result in irreversible damage

Diseases caused by Clostridium perfringens

food poisoning and gas gangrene

Food poisoning

*Clostridium perfringens*

benign disease characterized by abdominal cramps and watery diarrhea

Gas gandrene

*Clostridium perfringens*

endspores are introduced into the body through some traumatic event and cause necrosis

Diagnosis of Clostridium perfringens

aerobic plate/jar counting of food for more than 10^5 of bacteria in per gram of food or feces

Treatment of Clostridium perfringens

food poisoning if self-limited and gas gangrene requires removal of dead tissue and administration of antitoxin and penicillin

Prevention of Clostridium perfringens

difficult bc it is so common but proper cleaning of wounds can help avoid gas gandrene

Clostridium botulinum

anaerobic, endospore forming, common in soil and water

When does botulism occur?

results when the endospores germinate and produce botulism toxin

Virulence factor of Clostridium botulinum

botulism toxin

Botulism toxin

*in Clostridium botulinum*

deadliest toxin know and is absorbed through intestines travel to neuromuscular junction

Symptoms of botulism

occurs 12-36 hours after ingestion, double vision, difficult swallowing, flaccid muscle paralysis, and respiratory failure

How does the botulism toxin cause flaccid muscle paralysis and respiratory failure

usually acetylcholine is released to contract a muscle but the botulism toxin block the acetylcholine from releasing-> no muscle contraction anywhere, inability to inhale

3 forms of botulism

food-borne botulism, infant botulism, wound botulism

Food-born botulism

*Clostridium botulinum*

usually occurs due to the consumption of the toxin in a home canned, results in progressive paralysis

Infant botulism

*Clostridium botulinum*

results from the ingestion of endospores that will colonize the GI tract due to the lack of normal microbiota, paralysis and death are rare

Wound botulism

*Clostridium botulinum*

wound becomes contaminated with endospores, symptoms are the same as food-borne botulism

Diagnosis of Clostridium botulinum

symptoms are diagnostic but can confirm with culturing the food, feces, or patient's wound

Three approaches of treatment for Clostridium botulinum

1) repeated washing of the intestinal tract to remove clostridium

2)administer antibodies against botulism toxin to neutralize toxin in the blood

3)administer antimicrobial drugs to kill clostridia in infant botulism cases

Prevention of Clostridium botulinum

proper canning of food to prevent contamination and infants younger than one should not consume honey

Why shouldn't infants younger than one have honey?

honey creates an osmotic pressure that will kill regular microbiota but not botulism

Clostridium tetani

endospore forming and obligately anaerobic

found in soil, dust, and GI tract of animals and humans

When does tetanus occur?

results when the bacterial endospores germinate and produce tetanus toxin

How does the tetanus toxin cause respiratory failure?

the toxin blocks the inhibitory neuron so no signal is sent for the muscle to relax after the excitatory neuron is turn on->muscles contract to full force=can't exhale to breath

Diagnosis of Clostridium tetani

characteristic muscular contraction, bacteria is rarely isolated from clinical samples bc it grows too slow

Treatment of Clostridium tetani

thorough cleaning of wounds to remove endospores, passive immunization w/ immunoglobulin, administration of antimicrobials, and active immunization w/ tetanus toxoid

Prevention of Clostridium tetani

immunization with tetanus toxoid, booster every ten years

Mycobacterium

has waxy lipid mycolic acid covered cell wall that causes slow growth, protection from lysis, capacity for intracellular growth, and resistant to many things

The three main mycobacterial diseases

tuberculosis, leprosy, and opportunistic infections in AIDS patients

Tuberculosis

respiratory disease caused by mycobacterium tuberculosis

Virulence factors of mycobacterium tuberculosis

mycolic acid and cord factor

What is the cord factor

a cell wall component that keeps daughter cells together that increases virulence and inhibits migration of neutrophils

Transmission of Tuberculosis

respiratory droplets, can survive on fomites for 8 months

Three forms of tuberculosis

primary, secondary, and disseminated

Primary tuberculosis

results from the initial infection with M. tuberculosis

Secondary tuberculosis

reestablishment of active infection after period of dormancy, rupture of tubercule

Disseminated tuberculosis

results when infection spreads throughout the body, consumption

Diagnosis of Tuberculosis

acid-fast stain of sputum, tuberculin skin test, and chest x-rays to identify active disease

Treatment of Tuberculosis

common antimicrobial but difficult bc the bacteria grow slowly and can live within macrophages

Prevention of Tuberculosis

prophylactic use of antibacterial drugs and immunization w/ BCG vaccine is used

Leprosy

caused by mycobacterium leprae and bacteria has never been grown in cell free culture->hard to follow Koch's postulates

Two forms of leprosy

tuberculoid and lepromatous

Tuberculoid leprosy

nonprogressive form of the disease due to a strong cell-mediated immune response that is characterized by the loss of sensation in regions of the skin

Lepromatous leprosy

produces gradual tissue destruction that results in the loss of facial features, digits, and other body structures

Diagnosis of leprosy

based on signs and symptoms of disease, loss of sensation in skin lesions or disfigurment

Treatment of leprosy

combination of antimicrobial drugs, lifelong treatment is sometimes needed

Prevention of leprosy

primarily prevented by limiting exposure to the pathogen and BCG vaccine provides some protection

Most common mycobacterial infection among AIDS patients in the United States

mycobacterium avium-intracellulare, results from the ingestion of contaminated food/water and will cause massive organ failure

Which disease is not caused by an endospore forming bacterium:

anthrax, tetanus, pelvic inflammatory disease, botulism

pelvic inflammatory disease

Which bacteria divides by snapping division where the daughter cells remain attached in a V-shape:

staphylococci, enterococci, corynebacterium, listeria, mycobacterium

corynebacterium

What is the most common disease caused by propionibacterium:

acne, food poisoning, pneumonitis, folliculitis, a sty

acne

What bacteria produces one of the most deadly bacterial toxins known

Clostridium botulinum

True or false: The only source of tetanus is from a deep puncture wound from rusty nails

false

Which microbe is an opportunistic pathogen in patients being treated w/ broad-spectrum antibiotics:

clostridium difficile, listeria monocytogenes, mycobacterium leprae, nocardia asteroides

clostridium difficle

True or false: Bacillus anthracis is primarily a disease of humans

false