Chapter 18 Anaerobic Bacteria

Category Spore-forming: Spore-forming: rod, Gram (+)--- Clostridium rod, Gram (+)--- Clostridium Nonspore-forming: G+ or G- Nonspore-forming: G+ or G- rod or cocci rod or cocci

Clostridium Species Large, spore-forming, G+ bacilli Large, spore-forming, G+ bacilli The shape of the cell and location of the spore varies with the species The shape of the cell and location of the spore varies with the species Nature habitat is the soil or the intestinal tract of animals and humans Nature habitat is the soil or the intestinal tract of animals and humans Spores are highly resistant Spores are highly resistant cause disease primarily through the production of numerous exotoxins. cause disease primarily through the production of numerous exotoxins. perfringens, tetani, botulinum, perfringens, tetani, botulinum,

Section 1 Clostridium Tetani

Biological characterization Slim, G+ rod Slim, G+ rod Anaerobic (strictly) Anaerobic (strictly) Peritrichous flagella Peritrichous flagella terminal located round spore terminal located round spore its diameter greater than vegetative cell. its diameter greater than vegetative cell. (drumstick apperance) (drumstick apperance)

Pathogenesis and symptomatology A. pathogenesis By wounds contaminated with soil or foreign bodies By wounds contaminated with soil or foreign bodies by umbilical cord (infants) by umbilical cord (infants)

An anaerobic miroenvironment: The wounds are narrow and deep (a puncture wound with a rusty nail) The wounds are narrow and deep (a puncture wound with a rusty nail) local blood supply is poor: ischemia 缺血 local blood supply is poor: ischemia 缺血 necrotic tissuenecrotic tissue infected with facultative or other aerobic organismsinfected with facultative or other aerobic organisms

produces two exotoxins: tetanolysin tetanolysin tetanospasmin tetanospasmin a kind of neurotoxina kind of neurotoxin Heat-labileHeat-labile toxicity is strongtoxicity is strong Spread along nerves to the central nervous systemSpread along nerves to the central nervous system

Tetanospasmin binds to ganglioside receptors binds to ganglioside receptors inhibitory neurons in CNS inhibitory neurons in CNS Block releasing of the inhibitory glycine (neurotransmitter) Block releasing of the inhibitory glycine (neurotransmitter) stops nerve impulse to muscles stops nerve impulse to muscles spastic paralysis 痉挛性麻痹 spastic paralysis 痉挛性麻痹 severe muscle contractions and spasms severe muscle contractions and spasms can be fatal can be fatal

Tetanospasmin Tetanospasmin

B. symptomatology 1. Generalized tetanus Muscular spasms Muscular spasms Inability to open the mouth properly (lockjaw or trismus) 牙关紧闭 ; Inability to open the mouth properly (lockjaw or trismus) 牙关紧闭 ; (sardonic feature) 苦笑面容 (sardonic feature) 苦笑面容 Generalized muscle spasm Generalized muscle spasm opisthotonos 角弓反张 death

2. Neonatal tetanus Associated with an initial infection of umbilical stump Associated with an initial infection of umbilical stump

C. tetani This baby has neonatal tetanus. It is completely rigid. Tetanus kills most of the babies who get it. Infection usually happens when newly cut umbilical cord is exposed to dirt CDC

laboratory Diagnosis * by the clinical symptoms * by the clinical symptoms * a history of injury * a history of injury

Control Control organism must be removed by local debridement 清创术 organism must be removed by local debridement 清创术 toxoid toxoid TAT (skin test) TAT (skin test) antibiotics (For more serious wounds) antibiotics (For more serious wounds)

Section 2 C. perfringens C. perfringens

Biological characterization Large, G+, Large, G+, Bacillus with square ends Bacillus with square ends Form spores, capsule Form spores, capsule Can ferment a variety of sugars Can ferment a variety of sugars Produce multiple exotoxins Produce multiple exotoxins Anaerobic Anaerobic

Stormy fermentation In milk media In milk media Ferment lactose Ferment lactose Produce a large amount of gas Produce a large amount of gas Clot of casein are tore by gas Clot of casein are tore by gas

Pathogenesis and symptomatology Gas gagrene Gas gagrene Clostridial food poisoning Clostridial food poisoning

A. Gas gangrene By contamination of traumatized areas or from intestinal tract By contamination of traumatized areas or from intestinal tract anaerobic miroenvironment anaerobic miroenvironment Ferment carbohydrates in tissue Ferment carbohydrates in tissue Produce gas Produce gas produce variety of toxins and enzymes produce variety of toxins and enzymes

Edema Edema Hemorrhagic bullae Hemorrhagic bullae Crepitation 捻发音 Crepitation 捻发音 Systemic findings Systemic findings Coma, death Coma, death Without treatment death occurs within 2 days

B. Clostridial food poisoning By ingestion of B. By ingestion of B. Produce enterotoxin Produce enterotoxin diarrhea diarrhea

Section 4 C. botulinum

Biological characterization Anaerobic Anaerobic G+, large rod G+, large rod Peritrichous flagella Peritrichous flagella Spores are oval, subterminal Spores are oval, subterminal resemble tennis racket 网球拍状 resemble tennis racket 网球拍状 produces botulinum toxin produces botulinum toxin

Pathogenesis and symptomatology A. Botulinum toxin The main virulence factors The main virulence factors The most potent neurotoxin known in nature The most potent neurotoxin known in nature Resistant to the enzymes of the gastrointestinal tract Resistant to the enzymes of the gastrointestinal tract Destroyed by heating for 20 min at 100 ℃ Destroyed by heating for 20 min at 100 ℃

A. Botulinum toxin Absorbed from the gut Absorbed from the gut Inhibits the release of acetylcholine at the synapse Inhibits the release of acetylcholine at the synapse inhibits nerve impulses inhibits nerve impulses flaccid paralysis flaccid paralysis death death respiratoryrespiratory cardiac failurecardiac failure

B. deseases 1. Food-borne botulism ingestion of food contaminated by B. ingestion of food contaminated by B. Cause by botulinum toxin Cause by botulinum toxin Most common offenders Most common offenders Smoked foodsSmoked foods Vacuumpacked foodsVacuumpacked foods Canned alkaline foodsCanned alkaline foods

2. Wound botulism By botulinum spore contamination of traumatized areas By botulinum spore contamination of traumatized areas

3. Infant botulism Ingestion of C. botulinum- contaminated babies ’ foods (honey) Ingestion of C. botulinum- contaminated babies ’ foods (honey) Spores germinate, multiply and yield toxin Spores germinate, multiply and yield toxin “ Floppy baby ” “ Floppy baby ”

Latest progress Study of botulinum toxin application of botulinum toxin

summary C.tetani : morphology and stain, C.tetani : morphology and stain, pathogenesis (malgenic conditions), pathogenesis (malgenic conditions), prevention and treatment prevention and treatment C.perfringens: stain, culture, C.perfringens: stain, culture, diseases diseases C.botulinum: morphology and stain, C.botulinum: morphology and stain, pathogenesis, diseases pathogenesis, diseases