Chap 22 Anaerobic Organisms

The taxonomy of Anaerobes are separated into…

GP spore forming bacilli, GP non spore forming bacilli, GN non spore forming bacili, and Anaerobic Cocci

What is the main genus of GP, spore forming anaerobes?

Clostridium (and related Clostridioides)

Name relevant Clostridium spp

C. perfringens, C. botulinum, C. tetani, C. difficile

GP spore forming bacilli have a … shape

“box car”

What is the primary mode of transmission for GP spore forming bacilli?

Ingestion or open wounds that have been contaminated with soil

Name classic diseases from GP spore forming bacilli where the spores have been ingested

Botulism and Food poisonining

Name classic diseases from GP spore forming bacilli where the spores have entered through open wounds

Tetanus, Myonecrosis (gas gangrene), and wound infections

Which GP Spore forming bacilli has an endogenous origin whereas the others are exogenous?

C. difficile

What clostridium spp produces a double zone of hemolysis and is lecithinase positive?

C. perfringens

Which C. perfringens type is the most common and causes food poisoning?

Type A

What enterotoxin does C. perfringens type A produce during sporulation?

CPE (Clostridium perfringens enterotoxin) - causes diarrhea in food poisoning

What C. perfringens type causes Enteritis Necroticans (Necrosis of the intestinal lining)?

Type C

What toxins does C. perfringens Type C produce?

Beta and alpha toxin

What is the main virulence factor of C. botulinum?

Botulinum neurotoxin - an EXTREMELY potent neurotoxin that block acetylcholine release at neuromuscular junctions

What type of paralysis does botulinum toxin cause?

Flaccid paralysis

What is the mechanism of action of botulinum toxin?

It cleaves SNARE proteins, preventing acetylcholine release from presynaptic nerve terminals

What are the three main clinical forms of botulism?

1. Foodborne

2. Infant

3. Wound

What causes foodborne botulism?

Ingestion of preformed toxin in improperly canned or preserved foods

What causes infant botulism?

Ingestion of spores (not toxin), which germinated in the infant’s gut and release toxin - commonly linked to honey

What causes wound botulism?

Contamination of wounds with spores that germinate and produce toxin in anaerobic tissue

How is C. botulinum related to Botox?

Botox is a purified, diluted form of botulinum toxin type A, used therapeutically to temporarily relieve muscle for medical and cosmetic purposes

What is the treatment of botulism?

The antitoxin and supportive care in the form of respiratory assistance

Why is C. botulinum considered a potential agent of bioterrorism?

Because its neurotoxin is the most potent toxin known, causing paralysis and death in extremely small doses

How is C. botulinum differentiated from C. tetani in terms of toxin effect?

C. botulinum: blocks acetylcholine release —> flaccid paralysis

C. tetani: blocks inhibitory neurotransmitters —> spastic paralysis

What is the main virulence factor of C. tetani?

The Tetanospasmin neurotoxin that inhibits neurotransmitters

How does tetanus clinically present?

Trismus (lock jaw), Risus sardonicus (distorted grin), Opisthotonus (arched back), and muscle rigidity and spasms

What is the mode of transmission for C. tetani?

spores in the environment enter the skin through puncture wounds

How is tetanus prevented?

With the diphtheria-Tetanus-Pertussis (DTaP) Vaccine

How is tetanus treated?

Injection of antitoxin, muscle relaxants, and intensive therapy

What is myonecrosis (gas gangrene)?

Rapid necrosis of skeletal muscle causes by bacterial infection, most often the C. perfringens spp

What exotoxin causes the tissue necrosis in gas gangrene?

Alpha toxin

What Clostridium spp are involved in Bacteremia (bacteria in the blood)?

C. perfringens, C. septicum, C. tertium, and C. bifermentans 

What is the most common isolate in blood cultures?

C. perfringens

What clostridium causes pseudomembranous colitis?

C. difficile

Is C. difficile a part of the normal flora of the GI tract?

Yep

Why is C. diff an antibiotic associated diarrhea?

Because the antibiotics destroy the normal gut flora which increases growth of the bacteria causing toxin production (Type A: Enterotoxin and Type B: Cytotoxin)

C. diff is a … infection and increases in outpatients who have received antimicrobial therapy

nosocomial

PCR identification of C. diff is from the ID of…

both toxins and Glutamate Dehydrogenase (GDH)

What enzyme is found in all C. difficile and is important in identifying the bacteria by PCR?

GDH

What color does C. difficile fluoresce?

Chartreuse

What type of odor is associated with C. diff?

Barnyard or Horse Stable

What media do GP spore formers not grow on?

BBE and KVLB

These species are …

• Actinomyces

• Bifidobacterium

• Lactobacillus

• Propionibacterium and Cutibacterium

GP non spore forming bacilli

Which non spore forming anaerobe produces “molar tooth” colonies and sulfur granules?

Actinomyces israelii

Actinomycosis is a NF of what areas?

oral cavity, GI, and UG tracts

What disease is associated with Actinomycosis? 

Chronic Granulomatous Infectious Disease (CGD) - Granulomas erupt at the skin surface and drain pus

How is a definitive diagnosis of Actinomycosis made?

A gram stain of the pus

Which genus of non-spore-forming rods shows branching “dog bone” or “Y” shapes?

Bifidobacterium

Where is Bifidobacterium commonly found in the human body?

NF of the GI tract

What is a clinically significant role of Bifidobacteriun?

Probiotic activity

Bifidobacterium spp rarely causes infection except in…

immunocompromised patients or patients who had abdominal surgery

Where is Lactobacillus commonly found in the human body?

NF of the oral cavity, GI, and Female genital tract

What is Lactobacillus’ role in the health of the female genital tract?

In lactic acid production that lowers the pH, suppressing growth of other organisms

Is Lactobacillus catalase positive or negative?

Negative

What antibiotic is Lactobacillus resistant to?

Vancomycin

How is lactobacillus related to bacterial vaginosis (BV)?

In BV, Lactobacillus numbers decrease, leading to overgrowth of anaerobic bacteria like Gardnerella vaginalis, Prevotella and Mobiluncus

What is the morphology of Cutibacterium?

Often pleomorphic or club shaped

Where is Cutibacterium acnes normally found?

NF of skin, particularly, the sebaceous oil glands

Is Cutbacterium catalase positive or negative?

Catalase positive

What is the former name of Cutibacterium?

Propionibacterium

What acid does Cutibacterium produce?

Propionic acid that inhibits the growth of other bacteria

All Gram Negative bacilli Anaerobes are…

non spore forming

What is the distinct gram stain morphology of GNR Anaerobes?

Fusobacterium and Growth on BBE (growth in bile and hydrolyze esculin)

These species are…

• Bacteroides fragilis group

• Prevotella

• Porphyromonas

• Fusobacterium

GN Anaerobe Bacilli