Gram positive Cocci Staphylococci Streptococci Enterococci Bacilli Bacillus Clostridia Corynebacteria

Overview of the medically most important gram positive bacteria

Genus Clostridium

Learning objectives: Describe the basic microbiological features of the genus Clostridium Describe clinical significance of the genus Clostridium List the most clinically important Clostridium species List the main clinical conditions caused by C. perfringens, C. tetani, C. botulinum and C. difficile and describe their major virulence factors

Learning objectives: Describe the major differences between the main clinical conditions caused by C. perfringens, C. tetani, C. botulinum and C. difficile and describe the laboratory methods used in the diagnosis of each infection Describe in general the management of the main infections caused by genus Clostridium

Clostridium > 200 species and sub-species Thick, Gram-positive, sporing rod Strict anaerobes Soil is natural habitat GIT Exotoxins and enzymes

Medically important species C. perfringens ◦ Anaerobic cellulitis and gas gangrene (clostridial myonecrosis) C. tetani ◦ Tetanus C. botulinum ◦ Botulism C. difficile ◦ Pseudomembranous colitis

Diagnosis of clostridial infections Identification of the pathogen ◦ Gas gangrene Identification of the pathogen + toxins ◦ Tetanus, botulism and colitis

Morphology and culturing Large, Gram-positive rod Flagellated (except C. perfringens) Sporulated Anaerobic atmosphere at 37°C C. perfringens colonies are convex, smooth, and hemolytic Colonies of motile clostridia have an irregular edge

Management Penicillin G Antitoxins are used in therapy of tetanus and botulism Hyperbaric O 2 is used to treat gas gangrene The most important preventive measure against tetanus is active vaccination with tetanus toxoid

Gas gangrene (clostridial myonecrosis) Anaerobic cellulitis

Pathogen spectrum Clostridium perfringens C. novyi C. septicum C. histolyticum

Toxins and enzymes Toxins: ◦ Necrotizing, hemolytic, and/or lethal activity Enzymes: ◦ Collagenases, proteinases, DNases, lecithinases, and hyaluronidase

Pathogenesis and clinical picture Frequently contaminate open wounds Types of infections: ◦ Anaerobic cellulitis ◦ Gas gangrene (clostridial myonecrosis)

Anaerobic cellulitis Infection restricted to the fascial spaces that does not affect musculature There is no toxemia

Gas gangrene (clostridial myonecrosis) An aggressive infection of the muscles Gas, myonecrosis and toxemia Medical emergency

Laboratory diagnosis Specimens Direct examination Anaerobic culture Identification

Clostridium tetani (Tetanus)

Tetanus (lockjaw) Acute clostridial disease Clinical manifestations caused by strong neurotoxin (tetanospasmin)

Pathogenesis and clinical picture Pathogens invade tissues following injuries Toxin produced Increased muscle tone and spasms

Diagnosis Toxin detection in wound material The pathogen is difficult to culture

Treatment Anti-toxin Wound cleaning Muscle relaxants

Clostridium botulinum (botulism)

Botulism Rare but serious paralytic illness The toxin enters the human body in one of three ways: ◦ Ingestion of spores (infant botulism) ◦ Toxin ingested with food (adult botulism) ◦ Infected wounds (wound botulism)

Clostridium botulinum toxin Very strong neurotoxin Heat-labile protein Flaccid paralysis

Clinical picture of classic botulism Paralysis especially in the nerves of the head Frequent symptoms: seeing double, difficulty swallowing and speaking, constipation, and dry mucosa

Mortality and cause of death Mortality: 25–70%, depending on the amount of toxin ingested Death usually results from respiratory paralysis

Diagnosis and treatment Diagnosis: ◦ Toxin detection Therapy: ◦ Anti-toxin

Clostridium difficile (pseudomembranous colitis)

Clostridium difficile Fecal flora of 1–4% of healthy adults and in 30–50% of children during the first year of life Pseudomembranous colitis: ◦ Clindamycin ◦ Aminopenicillins ◦ Cephalosporins Antibiotic-associated colitis

Pathological mechanism Based on formation of two toxins: ◦ Toxin A is an enterotoxin ◦ Toxin B is a cytotoxin

Laboratory diagnosis Isolation of the pathogen Cytotoxin detection in stool filtrates by cytopathic effect ELISA for toxins “A” and “B”

Treatment Not always required Indicated only in severe cases Metronidazole is the drug of choice