Clostridium

genus Clostridium

large, gram-positive spore-forming anaerobic motile bacilli

found in soil, marine sediments, sewage, and GI as saprophytes

many clostridia produce a zone of beta hemolysis

200+ species

good growth on blood-enriched media

spores are usually wider than rod diameter, placed centrally, sub-terminally, or terminally

Clostridium botulinum

causes botulism

worldwide distribution

seven antigenic varieties of botulism toxin: serotypes A-G

A, B, E, and F are principal causes of human illness

• types A and B are associated with a variety of foods

• type C causes limberneck in birds

• type D causes botulism in mammals

• type E is associated with fish products

• type F is rare and severe, causing rapidly progressing paralysis

• type G is not associated with disease

botulinum toxin

absorbed from the GI tract, enters bloodstream, binds to receptors of presynaptic membranes of motor neurons of PNS and cranial nerves

flaccid paralysis

botulinum toxin lethal dose

1-2 ug/kg

foodborne botulism

intoxication following C. botulinum growth and toxin production in GI tract

wound botulism

result of tissue contamination with spores

commonly seen in injection drug user

infant botulism

honey is the most frequent vehicle of infection

inhalation botulism

occurs when toxin enters respiratory tract

very rare

botulism diagnostics

detection of toxin from serum, gastric secretions, or stool, or from leftover food

botulism treatment

supportive care

mechanical ventilation if necessary

trivalent antitoxin (A, B, E) IV

Clostridium tetani

bacteria responsible for tetanus

worldwide distribution

types distinguished by flagellar antigens

tetanus

rigidity and convulsive spasms of skeletal muscle

noninvasive infection

caused by tetanospasmin

tetanolysin is a nonpathogenic hemolysin

tetanospasmin

blocks the release of inhibitory neurotransmitters (GABA, glycine)

tetanus diagnosis

clinical picture, history of injury, anaerobic culture from wounds

tetanus treatment

not satisfactoryt

tetanus prevention

toxoid immunization

Clostridium perfringens

produces invasive infection, including gas gangrene

produces enterotoxin that induces intense diarrhea in 7-30 hours

gas gangrene/myonecrosis

lethal infection of soft tissue characterized by rapidly progressive gangrene of injured tissue and foul-smelling gas production

always a mixed infection with toxigenic clostridia, proteolytic clostridia, various cocci and gram-negative organisms

clostridial toxin aggregates platelets and forms thrombi, cutting off blood supply to area: skin turns green/black

Clostridium difficile

produces toxins A and B that cause a severe diarrheal disease called pseudomembranous colitis

infection usually results from antibiotic treatment

infection causes watery/bloody diarrhea, abdominal cramps, leukocytosis, fever