Microbiology Chapter 19 Gram Positive Bacilli of Medical Importance

Bacilli -

rod-shaped cells that can be arranged in single cells or in chains of cells

List the 3 general groups of bacilli

1. Endospore formers

2. Non-Endospore formers

3. Irregular shape and staining

Describe structure of Bacillus Genus

gram positive, endospore forming, motile, rod shaped

What is the primary reservoir of Bacillus genus?

soil, may infect grazing animals

Bacillus Genus are mostly ______

saprobes, many aerobes and facultative anaerobes, catalase +

Bacillus genus. Medically important species:

Bacillus cereus, Bacillus anthracis

Bacillus anthracis: Anthrax -

central endospores, facultative anaerobe

Bacillus anthracis: Anthrax - Virulence factors

Polypeptide capsule (hides from white blood cells), Exotoxin (anthrax toxin)

What are the 3 types of anthrax?

Cutaneous, Gastrointestinal, Pulmonary

What is the least lethal type of anthrax?

Cutaneous (enters through skin)

What is the most lethal type of anthrax?

Pulmonary (inhalation)

Gastrointestinal anthrax-

ingestion

What are the treatments for anthrax?

Antibiotics: penicillin, tetracycline, ciprofloxacin

Vaccine: live strain and/ or purified toxoid (limited effectiveness: multiple boosters and many inoculations)

What is the difference between Bacillus cereus and B.anthracis ?

Bacillus cereus is very similar genetically and morphologically to B.anthracis, but it doesn’t make Anthrax toxin

Bacillus cereus can cause ____

food poisoning (spores survive cooking)

Describe structure of clostridium genus

gram positive, rod- shaped, endospore forming

Where can clostridium genus be found?

often found in soils, animals, GI tracts

Gas gangrene -

dead tissue sore that releases gas, most frequently caused by Clostridium perfringens

What are the virulence factors of gas gangrene?

Alpha toxin, collagenase, hyaluronidase, DNase

What happens during gas gangrene?

bacteria will ferment carbohydrates in the muscles which causes gas, gas separates muscle fibers

Myonecrosis Treatment

cleaning wounds, debridement, antibiotics, hyperbaric O2 chamber

Tetanus -

lock jaw, neuromuscular disease caused by Clostridium tetani, most often occurs from puncture wounds, IV drug users, burns

Clostridium tetani cells produce what?

tetanospasmin, causes uncontrollable muscle spasms and contraction

How do you treat tetanus?

Antitoxin Ig specific to Tetanospasmin toxin (neutralizes new toxin but doesn’t affect already bound toxin)

What antibiotics can be used to treat tetanus?

penicillin, tetracycline

Clostridium difficile causes _______

antibiotic associated colitis

Clostridium difficile produces _____

enterotoxins damaging intestines

What is the treatment of clostridium difficile?

Antibiotics: oral vancomycin or metronidazole or Fecal transplant: transplant healthy feces into colon

Clostridium botulinum -

Botulism (rare, very lethal)

Clostridium perfringens -

mild intestinal illness, common form of food poisonins, not very lethal

What treatment is used for Clostridial food poisoning?

penicillin antibiotic, antitoxin for botulism, cardiac and respiratory support for botulism

C.botulinum produces ____

Botulinum toxin

Botulinum toxin blocks _____

release of Acetylcholine at neuromuscular junctions, muscles can’t contract, respiratory failure

_______ allow growth of C. botulinum

Anaerobic conditions

What is Botox used to treat?

Can treat cross eyes, painful muscle contractions, reduces skin wrinkles, migraines, needs to be injected every 4-6 months

Describe the structure of Listeria monocytogenes

Gram positive, flagellated, non-spore-forming, resistance to heat, cold, pH, salt, bile

Describe the structure of erysipelothrix rhusiopathiae

gram positive, infections can cause red, itchy lesions, especially on the skin

Where are erysipelothrix rhusiopathiae located?

tonsils of pigs, other animals and environments

What is the third most common food poisoning fatalities?

listeria monocytogenes: listeriosis

Listeria monocytogenes: listeriosis (Location)

Primarily soil and water, also in contaminated foods (meat and dairy)

listeria monocytogenes: listeriosis (Treatment)

ampicillin, trimethoprim antibiotics

Irregular Forming Bacilli -

pleomorphic/polymorphic, stain unevenly

Medically important genera:

Corynebacterium, mycobacterium, nocardia, Propionibacterium, actinomyces

Corynebacterium diphtheriae causes ____

diphtheria

Corynebacterium diphtheriae starts with _____

local infection, if systemic may damage the heart, nerves

Mycobacteria -

irregular Bacilli, acid-fast staining, contain mycolic acid, strict aerobes, catalase +

Mycobacterium tuberculosis spreads how?

air droplets containing M. tuberculosis

Mycobacterium tuberculosis infects _____

lungs, kidneys, lymph, meninges, bone

Mycobacterium tuberculosis doesn’t produce _____

exotoxins or enzymes

Primary TB-

phagocytosis, immune system surrounds and attacks infected tissue

Secondary TB-

if patient doesn’t fully fight off infection, bacteria survive and may be dormant or continue to grow

What antibiotics are used to tuberculosis?

isoniazid, rifampin, pyrazinamide

Leprosy -

Numbness, muscle weakness, thickened earlobes, grows in nerve cells, skin macrophages, obligate parasite

Leprosy is found where-

humans, armadillos

Genera Actinomyces & Nocardia are _____

nonmotile filamentous bacteria that may cause chronic infection of skin and soft tissues

Actinomyces Israelii-

responsible for diseases of the oral cavity, thoracis or intestines (actinomycosis)

Nocardia brasiliensis -

causes pulmonary disease similar to TB (nocardiosis)