Chapter 19 Gram Positive Bacilli

3 Groups of Gram Positive Bacilli?

1. Endospore formers

2. Non-endospore formers

3. Irregular Shaped and Staining properties

3 Genera of Gram + Bacilli?

1. Bacillus

2. Clostridium

3. Mycobacterium

Key Differences between Genera

1. Bacillus is Aerobic

2. Clostridium is Anaerobic

3. Mycobacterium produces NO spores, has mycolic acids

What is an Endospore

• a dense survival unit that develops in a vegetative cell in response to nutrient deprivation

What types of bacteria are Endospores usually?

-Most are gram+, motile, rod-shaped

-Ex. Bacillus and Clostridium

Bacillus Anthracis: Diseases?

Cutaneous/Pulmonary anthrax

Bacillus Cereus: Diseases?

Food Poisoning

Clostridium Perfringens: Diseases

Gas Gangrene (myonecrosis), Food Poisoning (mild)

Clostridium Tentani: Diseases

Tetanus

Clostridium Difficile: Diseases

C. Diff Associated Diseases

Clostridium Botulinum: Diseases

Botulism (wound, infant, food-borne)

Mycobacterium Tuberculosis: Diseases

Recurrent/Extrapulmonary/Primary TB

Mycobacterium Leprae: Diseases

Leprosy of skin (lepromatous) and nerve (tuberculoid)

Genus Bacillus: General Characteristics

• Saprobic

• Source of Antibiotics

• Degrades macromolecules

Is Bacillus O2 Requirements?

Aerobic and Catalase +

Bacillus Environment

Soil

2 Significant Species of Bacillus

• Bacillus anthraces; cause of anthrax

• Bacillus cereus; food poisoning

Bacillus Anthracis Shape & Growth Conditions

• Large, block-shaped angular nonmotile rods

• Endospores form in all environments except inside a living host

3 Types of Anthrax

• cutaneous - spores enter through skin, black sore - eschar; least dangerous

• pulmonary - inhalation of spores from animal products or soil

• Gastrointestinal - ingested spores. Rare, lethal

(Anthrax cases reported in livestock from Africa, Asia, Middle East)

Bacillus Cereus Growth

• Grows in foods, survive cooking and heat

• No treatment

• Resist disinfection/antisepsis

Bacillus Cereus Environment

Air and Dust borne

Bacillus Cereus Effects

• Food poisoning; nausea, vomiting, cramps, diarrhea, 24-hour duration

What does Genus Clostridium Synthesize?

• Synthesize organic acids, alcohols, and exotoxins

Genus Clostridium O2 Requirements

• Anaerobic and catalase negative

Clostridium Type of Infections?

wound/tissue infections, and food intoxications

Clostridium Perfringens Type of Infection

most frequent clostridia involved in soft tissue and wound infections

Where is Clostridium Perfringens Found

Spores found in soil, human skin, intestine, and vagina

Clostridium Perfringens Methods of Entry

surgical incisions, compound fractures, diabetic ulcers, septic abortions, puncture wounds, gunshot wounds

Clostridium Perfringens Virulence Factors

• Alpha toxin (RBC rupture, edema, and tissue destruction)

• Collagenase

• Hyaluronidase

• DNase

2 Forms of Gas Gangrene

• True Myonecrosis

• Anaerobic cellulitis — bacteria stay in already-dead tissue, produces gas and toxins but is localized; Less aggressive.

What is True Myonecrosis?

• More Destructive, mimics necrotizing faciitis

• Fermentation of muscle carbohydrates results in gas formation

Physical Treatment of Gangrene

Cleansing or Debridement of tissue

What Antibiotics for Gangrene?

Cephasporin & Penicillin

What kind of therapy for Gangrene?

Hyperbaric Oxygen Therapy (Adding O2)

T/F There are vaccines for Gangrene

False

What does Clostridium Tetani Cause?

Tetanus or Lockjaw

Tetanus

• Neuromuscular disease causing muscle spasms or paralysis

• Required Anaerobic environment

How does tetanus occur

spores enter wounds, burns, umbilicus, frostbite, crushed body parts

Tetanospasmin (Chemistry of Tetanus)

• Neurotoxin blocks inhibitory neurotransmitter release at motor nerve endings → muscles contract uncontrollably

• Paralysis of respiratory muscles can cause death

Demographic of Tetanus

Geriatric patients, IV drug abusers, neonates in developing countries (neonatal tetanus)

Clostridium difficile Infection In Hospitals

Major Cause of diarrhea in hospitals

Is C. Diff. a normal resident?

Yes, resident of intestines in low numbers

2 Species of Clostridial Food Poisoning

• Clostridium botulinum – rare but severe intoxication usually from home canned food

• Clostridium perfringens – mild intestinal illness; second most common form of food poisoning worldwide

Botulism

Intoxication associated with inadequate food preservation

Clostridium botulinum

• spore-forming anaerobe; commonly inhabits soil and water'

• Botulinum toxin, is released

Clostridium Botulinum Growth Steps

1. Spores are present on food when gathered and processed

2. If reliable temperature and pressure are not achieved air will be evacuated but spores will remain

Botulinum toxin Function

• in neuromuscular junctions, blocks the release of acetylcholine necessary for muscle contraction to occur

• Double or blurred vision, difficulty swallowing

Infant botulism cause

• ingested spores

• Immature state of the neonatal intestine and resident microbiota allows the spores grow and release neurotoxin

• Most common botulism in US

Treatment of Botulism

• Antitoxin; cardiac and respiratory support

• Penicillin

• Propperly preserve canned foods, usage of preservatives

Clostridial Gastroenteritis

• Caused by Clostridium Perfringens

• Spores contaminate food that has not been cooked thoroughly enough to destroy spores

Difference between Bacillus anthraces and cereus?

Antharcis is Aerobe

Cereus is Facultative Anaerobe

Mycobacteria Testing

• Acid fast stain

• Produce catalase

Shape of mycobacteria

Irregular bacili (polymorphic)

How fast do Mycobacteria grow?

VERY slow

What is tubercle

long, thin rods that grows in masses or strands to protect M. Tuberculosis

Mycobacterium TB virulence factors

Complex waxes and cord factors

Predisposing factors of TB

• inadequate nutrition, debilitation of the immune system, poor access to medical care, lung damage, and genetics

• Airborne

Sign of Mycobacterium?

Coughing up blood

How many people carry tubercle bacillus?

1/3 of world population, 15 million in U.S.

• 5 to 10% infected people develop clinical disease

Infectious dose of TB

10 cells

TB Progression

1. Week 3-4: Immune system forms tubercles (granulomas) — central core of bacilli surrounded by inflammatory cells

2. Advanced stage: Central core undergoes caseous (cheese-like) necrosis → eventually heals via calcification

Detecting TB: Tuberculin Sensivity

Mantoux test- injection of PPD (tuberculin) look for read wheal to form in 48-72 hours

Detecting TB: In vitro TB test

• QuantiFERON-TB Gold test

• T-SPOT TB tes

Detecting TB: Other Methods

• Chest X-rays – non-diagnostic, used to rule out pulmonary TB

• Acid-fast staining – of sputum or other specimens

  • Ziehl-Neelsen stain

• Cultural isolation and biochemical testing (LAB TESTING OF PLATES)

What is false Positive for TB?

When you have previous TB antibodies that react to the Mantoux test

Step 1 Prevention of TB

• 6-24 months of at least 2 drugs for 8 weeks

  • Isoniazid and rifampin

Step 2 Prevention of TB

• daily doses of INH and RIF for 18 weeks

Mycobacterium leprae

• leprosy, a chronic disease that begins in the skin and mucous membranes and progresses into nerves

• Hansen’s Disease

• strict parasite

Why can’t you culture mycobacterium leprae

• very virus-like, cannot grow on artificial media

• slowest growing of ALL species

How does M. Leprae multiply?

within host cells in large packets called globi

2 forms of Leprasy?

Tuberculoid (paucibacillary)

Lepromatous (multibacillary)

Tub vs Lep # of bacilli?

Tub: Few

Lep: Many

Tub vs Lep Lesions?

Tub: Shallow skin lesions

Lep: Deeper lesions in cooler areas of body

Tub vs Lep Effects?

Tub: Loss of pain sensation in lesions

Lep: Sensory loss, occurs late In disease

Tub vs Lep Skin nodules?

Tub: No skin nodules

Lep: Gross skin nodules

Diagnosing Leprosy

• Combination of symptomology, microscopic examination of lesions, and patient history

• Numbness in hands and feet, loss of heat and cold sensitivity, muscle weakness, thickened earlobes, chronic stuffy nose

• Detection of acid-fast bacilli in skin lesions, nasal discharges, and tissue samples

Treatment of Leprosy

• No definitive vaccine

• Trials indicate the “bacille Calmette-Guérin” (BCG) vaccine may prevent tuberculosis

3 Types of Infections by Non-TB Myocobacteria

• Disseminated Micobacterial Infection in AIDS

  • Caused by Mycobacterium avian complex bacilli

• Nontuberculous Lung Disease

  • Mycobacterium kansasii, causes pulmonary infections

• Miscellaneous Mycobacterial Infections

Specific Miscellaneous Mycobacterial Infections

M. marinum – water inhabitant; lesions develop after scraping on swimming pool concrete. Labeled fish tank granuloma

M. scrofulaceum – infects cervical lymph nodes in children living in the Great Lakes region, Canada, and Japan

M. paratuberculosis – raw cow’s milk; recovered from 65% of individuals diagnosed with Crohn’s disease

What does Lepromatous (Multibacillary) Leprosy cause?

Severe disfigurement of face and extremities

What are usual habitats of endospore-forming bacteria?

a. intestines of animals

b. soil

c. water

d. foods

b. soil

Most Bacillus species are

a. true pathogens

b. opportunistic pathogens

c. nonpathogens

d. commensals

c. nonpathogens

Many clostridial diseases require a(n) _____ environment for their development

a. living tissue

b. anaerobic

c. aerobic

d. low pH

b. anaerobic

Clostridium Perfringens causes

a. myonecrosis

b. food poisoning

c. antibiotic-induced colitis

d. both a and b

d. both a and b

The action of tetanus exotoxin is on the

a. neuromuscular junction

b. sensory nurons

c. spinal interneurons

d. cerebral cortex

c. spinal interneurons

The action of botulinum toxin is on the

a. spinal nerves

b. cerebellum

c. neuromuscular junction

d. smooth muscle

c. neuromuscular junction

An infection peculiar to swine causes ____ when transmitted to humans

a. anthrax

b. diphtheria

c. tuberculosis

d. erysipeloid

d. erysipeloid

TB is spread by

a. contaminated fomites

b. food

c. respiratory droplets

d. vectors

c. respiratory droplets

The form of Hansen’s disease associated with severe disfigurement of the face is

a. paucibacillary

b. multibacillary

c. facio-cranial

d. papular

b. multibacilary

Soil mycobacteria can be the cause of

a. tuberculosis

b. Hansens disease

c. fish tank granuloma

d. erysipeloid

c. fish tank granuloma

Caseous lesions containing inflammatory WBC are

a. lepromas

b. pseudomembranes

c. eschars

d. tubercles

d. tubercles

Which infectious agent is an obligate parasite

a. Mycobacterium tuberculosis

b. Corynebacterium diptheriae

c. Mycobacterium leprae

d. Clostridioides difficile

c. Mycobacterium leprae

Which infections would be categorized as a zoonosis

a. anthrax

b. diptheria

c. gas gangrene

d. both a and b

a. anthrax

Actinomycetes are ___ that cause ___

a. filamentous rods, chronic granuloma infections

b. pleomorphic bacteria, erysipeloid

c. spore-formers, tooth decay

d. hyphae, pseudomembranes

a. filamentous rods, chronic granuloma infections