chapter 18 anaerobic bacteria category spore-forming: spore-forming: rod, gram (+)--- clostridium...

Chapter 18Chapter 18

Anaerobic Anaerobic BacteriaBacteria

CategoryCategory

Spore-forming: Spore-forming:

rod, Gram (+)--- rod, Gram (+)--- ClostridiumClostridium

Nonspore-forming: G+ or G-Nonspore-forming: G+ or G-

rod or coccirod or cocci

Clostridium SpeciesClostridium Species Large, Large, spore-formingspore-forming, , G+ bacilliG+ bacilli The shape of the cell and location of the The shape of the cell and location of the

spore variesspore varies with the species with the species Nature habitat is the soil or the intestinal Nature habitat is the soil or the intestinal

tract of animals and humanstract of animals and humans Spores are Spores are highly resistanthighly resistant cause disease primarily through the cause disease primarily through the

production of numerous production of numerous exotoxinsexotoxins.. perfringens, tetani, botulinum, perfringens, tetani, botulinum,

Section 1Section 1

Clostridium TetaniClostridium Tetani

BiologicalBiological characterizationcharacterization

Slim, Slim, G+ rodG+ rod Anaerobic (strictly)Anaerobic (strictly) Peritrichous flagellaPeritrichous flagella terminal located round sporeterminal located round spore its diameter greater than its diameter greater than

vegetative cell. vegetative cell.

((drumstick apperancedrumstick apperance) )

Pathogenesis and symptomatologyPathogenesis and symptomatology

A. pathogenesisA. pathogenesis

By woundsBy wounds contaminated with contaminated with soil or foreign bodiessoil or foreign bodies

by umbilical cord (infants) by umbilical cord (infants)

An anaerobic miroenvironment:An anaerobic miroenvironment: The wounds are narrow and deep The wounds are narrow and deep

(a puncture wound with a rusty (a puncture wound with a rusty nail)nail)

local blood supply is poor: local blood supply is poor: ischemia ischemia 缺血缺血• necrotic tissuenecrotic tissue• infected with facultative or other infected with facultative or other

aerobic organismsaerobic organisms

produces two exotoxinsproduces two exotoxins:: tetanolysintetanolysin tetanospasmin tetanospasmin

• a kind of neurotoxina kind of neurotoxin• Heat-labileHeat-labile• toxicity is strongtoxicity is strong• Spread along nerves to the central Spread along nerves to the central

nervous systemnervous system

TetanospasminTetanospasmin

binds to ganglioside receptors binds to ganglioside receptors • inhibitory neurons in CNSinhibitory neurons in CNS

Block releasing of the inhibitory Block releasing of the inhibitory glycine (neurotransmitter)glycine (neurotransmitter)

stops nerve impulse to muscles stops nerve impulse to muscles spastic paralysis spastic paralysis 痉挛性麻痹痉挛性麻痹 severe muscle contractions and severe muscle contractions and

spasmsspasms can be fatalcan be fatal

TetanospasminTetanospasmin

B. symptomatologyB. symptomatology

1. Generalized tetanus1. Generalized tetanus Muscular spasmsMuscular spasms Inability to open the mouth properly Inability to open the mouth properly

(lockjaw or trismus) (lockjaw or trismus) 牙关紧闭牙关紧闭 ;;

(sardonic feature)(sardonic feature) 苦笑面容苦笑面容 Generalized muscle spasmGeneralized muscle spasm opisthotonos 角弓反张 death

2. Neonatal tetanus 2. Neonatal tetanus Associated with an initial Associated with an initial

infection of umbilical stumpinfection of umbilical stump

C. tetaniC. 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 Diagnosislaboratory Diagnosis

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

ControlControl

organism must be removed by organism must be removed by local local debridement debridement 清创术清创术

toxoidtoxoid TAT (skin test)TAT (skin test) antibiotics (For more serious antibiotics (For more serious

wounds)wounds)

Section 2Section 2

C. perfringensC. perfringens

Biological characterizationBiological characterization Large, Large, G+,G+, Bacillus with square endsBacillus with square ends Form Form spores, capsulespores, capsule Can ferment a variety of sugarsCan ferment a variety of sugars Produce multiple exotoxinsProduce multiple exotoxins AnaerobicAnaerobic

Stormy fermentationStormy fermentation

In milk mediaIn milk media Ferment lactoseFerment 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 symptomatologyPathogenesis and symptomatology

Gas gagreneGas gagrene

Clostridial food poisoningClostridial food poisoning

A. Gas gangreneA. Gas gangrene

By contamination of traumatized By contamination of traumatized areas or from intestinal tractareas or from intestinal tract

anaerobic miroenvironmentanaerobic miroenvironment Ferment carbohydrates in tissueFerment carbohydrates in tissue Produce gas Produce gas produce variety of toxins and produce variety of toxins and

enzymes enzymes

Edema Edema Hemorrhagic bullaeHemorrhagic bullae Crepitation Crepitation 捻发音捻发音 Systemic findingsSystemic findings Coma, deathComa, death

Without treatment Without treatment death occurs within 2 death occurs within 2 daysdays

B. Clostridial food poisoning B. Clostridial food poisoning

By ingestion of B.By ingestion of B. Produce enterotoxinProduce enterotoxin diarrheadiarrhea

Section 4Section 4C. botulinumC. botulinum

Biological characterizationBiological characterization

AnaerobicAnaerobic G+, large rodG+, large rod Peritrichous flagellaPeritrichous flagella SporesSpores are oval, subterminal are oval, subterminal

resemble tennis racketresemble tennis racket 网球拍状网球拍状 produces botulinum toxin produces botulinum toxin

Pathogenesis and symptomatologyPathogenesis and symptomatology

A. Botulinum toxinA. Botulinum toxin The main virulence factorsThe main virulence factors The most potent neurotoxinThe most potent neurotoxin

known in natureknown in nature Resistant to the enzymes of the Resistant to the enzymes of the

gastrointestinal tractgastrointestinal tract Destroyed by heating for 20 Destroyed by heating for 20

min at 100℃min at 100℃

A. Botulinum toxinA. Botulinum toxin

Absorbed from the gut Absorbed from the gut Inhibits the release of Inhibits the release of

acetylcholine at the synapseacetylcholine at the synapse inhibits nerve impulses inhibits nerve impulses flaccid paralysisflaccid paralysis death death

• respiratory respiratory •cardiac failurecardiac failure

B. deseasesB. deseases

1. Food-borne botulism1. Food-borne botulism ingestion of food contaminated ingestion of food contaminated

by B.by B. Cause by botulinum toxin Cause by botulinum toxin Most common offendersMost common offenders

• Smoked foodsSmoked foods• Vacuumpacked foodsVacuumpacked foods• Canned alkaline foodsCanned alkaline foods

2. Wound botulism2. Wound botulism

By botulinum spore contamination By botulinum spore contamination of traumatized areasof traumatized areas

3. Infant botulism3. Infant botulism Ingestion of C. botulinum-Ingestion of C. botulinum-

contaminated babies’ foods contaminated babies’ foods (honey)(honey)

Spores germinate, multiply and Spores germinate, multiply and yield toxinyield toxin

““Floppy baby”Floppy baby”

Latest progressLatest progress

Study of botulinum toxin

application of botulinum toxin

summarysummary

C.tetaniC.tetani : morphology and stain, : morphology and stain,

pathogenesis (malgenic conditions),pathogenesis (malgenic conditions),

prevention and treatmentprevention and treatment C.perfringensC.perfringens: stain , culture, : stain , culture,

diseasesdiseases C.botulinumC.botulinum: morphology and stain,: morphology and stain,

pathogenesis, diseasespathogenesis, diseases