Anaerobes

What are anaerobes?

Microorganisms that do not require oxygen for growth and may even die in its presence.

Where are anaerobes prevalent?

Human mouth, gastrointestinal tract, colon, female genital tract, and skin.

How do anaerobes compare to aerobic bacteria in the lower intestinal tract?

Anaerobes outnumber aerobic bacteria by 1000:1 in the lower intestinal tract.

What types of infections can anaerobes cause?

Devastating infections often polymicrobic and considered important human pathogens.

What is an exogenous infection?

An infection that originates from external sources.

Give an example of an exogenous infection caused by anaerobes.

Clostridium botulinum and Clostridium tetani.

What is an endogenous infection?

An infection that originates from within the body, often involving commensal organisms.

What is an example of an endogenous infection?

Bacteroides fragilis leading to abdominal abscess.

What are obligate aerobes?

Microorganisms that require oxygen for growth and metabolism.

What distinguishes strict anaerobes?

Cannot tolerate oxygen and will die upon exposure.

What are facultative anaerobes?

Microorganisms that can use oxygen for metabolism but can also grow in anaerobic conditions.

What are aerotolerant anaerobes?

Microorganisms that can survive in the presence of oxygen but do not utilize it.

What do microaerophiles require?

Oxygen but only in low concentrations.

What types of specimens are preferable for anaerobic culture?

Abscesses from liver, lung, brain, and abdomen; necrotic tissue; wound infections near mucous membranes.

What specimens should be avoided for anaerobic cultures?

Nasal, pharyngeal, vaginal swabs, and voided urine.

What is essential for transporting specimens to maintain anaerobic conditions?

Use of gassed out collection tubes and PRAS media.

What types of common infections are caused by anaerobes?

Abscesses, dental infections, aspiration pneumonia, and post-operative infections.

What are the gram stain characteristics of Bacteroides, Porphyromonas, and Prevotella?

Pale, pleomorphic, gram-negative coccobacilli exhibiting bipolar staining.

What is the structure of Fusobacterium species under gram stain?

Long, thin gram-negative bacilli with tapered ends.

What characterizes Actinomyces species?

Branching gram-positive bacilli.

What is the gram stain appearance of Clostridia species?

Large gram-positive bacilli, with C. perfringens showing boxcar arrangement.

What are the types of spores classified by Clostridium?

Terminal, central, and subterminal spores.

Where are terminal spores found in Clostridium tetani?

At the end of the rod, round and swollen.

What media is used for anaerobic culture?

Media supplemented with hemin, blood, vitamin K, and reducing agents.

What does PEA agar do?

Inhibits facultative anaerobes to isolate gram-positive and gram-negative obligate anaerobes.

What is KV agar used for?

Isolating gram-negative obligate anaerobes like Bacteroides and Fusobacterium.

What does PVLB agar isolate?

Gram-negative obligate anaerobes.

What is the purpose of thioglycollate broth?

Enriched broth used for plating anaerobically.

What is the anaerobic jar used for?

Creating an anaerobic environment for culturing bacteria.

What gases are used in anaerobic chambers?

85% N2, 10% H2, 5% CO2.

What are common identification techniques for anaerobes?

Gram stain, gross examination, colonial morphology, and biochemical tests.

Which biochemical tests help in identifying anaerobes?

Catalase test, nitrate reduction, and indole production.

What characterizes Clostridium species?

Gram-positive, spore formers, catalase negative, true exotoxin producers.

What are the neurotoxins produced by Clostridium tetani?

Tetanospasmin.

How does Clostridium tetani cause tetanus?

By introducing toxins through wounds leading to muscle contractions.

What symptoms are associated with tetanus?

Lockjaw and characteristic back arching.

How is tetanus treated?

With antitoxins, antibiotics, and supportive care.

What is the main diagnostic feature of Clostridium tetani?

Gram positive bacilli with terminal spores resembling a tennis racket.

What causes botulism?

Food with preformed botulism toxin, wounds, or infants ingesting spores.

How does botulism toxin affect the body?

It binds to nerve fiber synapses causing flaccid paralysis.

What are the common types of botulism toxin?

Types A, B, E are most common.

What are the clinical signs of botulism?

Flaccid paralysis, especially affecting thoracic muscles.

What is the treatment for botulism?

Antitoxin administration to bind the toxin.

What infections does Clostridium perfringens cause?

Myonecrosis, food poisoning, and intra-abdominal infections.

What types of toxins does C. perfringens produce?

Alpha toxin, hemolysins, and enterotoxins.

What are the identifying features of Clostridium perfringens on blood agar?

Double zone of hemolysis.

What tests can identify Clostridium perfringens?

Lipase positive on egg yolk agar, reverse CAMP test.

What characterizes Clostridium difficile?

Gram-positive, non-spore forming bacilli associated with opportunistic infections.

What common infection is caused by Clostridium difficile?

Antibiotic-associated pseudomembranous colitis.

What is a common method for identifying C. difficile?

Testing for toxin A (enterotoxin) or toxin B (cytotoxin).

What are the signs of Actinomyces israelii infections?

Yellow 'sulfur' granules and actinomycosis.

Where is normal flora of Gram positive non-spore forming bacilli found?

Oral cavity, bowel, vaginal tract, and urinary tract.

What types of infections can anaerobic gram-positive cocci cause?

Abscesses in various organs including liver and brain.