Chapter 18 Anaerobic bacteria

Classification spore-forming anaerobes Clostridium --G+ exogenous infection --pathgen non-spore-forming anaerobes G+, G- cocci, bacilli endogenous infection—opportunistic infection

Content Clostridium C. tetani C. botulinum C. perfringens C. difficile Non-spore-forming anaerobes

I. Clostridium General characteristics gram-positive, spore-forming bacilli Distributed in soil and intestine of human and animal obligate anaerobes motile -- peritrichous flagella (exception: C. perfringens—nonmotile) Exotoxin--- typical clinical symptoms

I. Clostridium C. tetani C. botulinum C. perfringens C. difficile

C. tetani

C. tetani--Characteristics anaerobic gram-positive rod that forms terminal spores—”drumstick” motile with peritrichous flagella No capsule tetanospasmin

C. tetani--Pathogenicity portal of entry: wound conditions of infection regional anaerobic environment deep and narrow wound, contamination of soil or foreign bodies necrotic tissues contamination of aerobes or facultative anaerobes

C. tetani-- Pathogenicity Virulence factors Tetanospasmin Protein (neurotoxin) Heat-labile (65℃, 30min) and protease-labile Toxoid available(artificial active vaccination) Mechanisms

Mechanisms of tetanospasmin toxin → inhibitory interneuron → blocks the release of neurotransmitters from the presynaptic membrane of inhibitory interneurons, e.g., glycine and γ–aminobutyric acid ( inhibit the motor neuron) → spastic paralysis (rigid paralysis) excitatory transmitter: acetylcholine inhibitory transmitter: glycine and γ–aminobutyric acid

Mechanisms of tetanospasmin spastic paralysis (rigid paralysis)

C. tetani-- Pathogenicity Disease-tetanus latent period: 4-5d ～ several weeks typical symptoms: rigid paralysis Opisthotonos Lockjaw, sardonic smile Drooling, sweating, irritability

C. tetani-- Pathogenicity Disease-neonatal tetanus a frequent cause of death in developing countries most common causes: cutting the umbilical cord with unsterilized instruments or infection of the umbilical stump the fatality rate: around 50% the common death cause: respiratory failure

Microbiological test Typical manifestations and injury history help diagnosis. Microscopic detection and isolation culture are usually not used .

C. tetani-- Immunity Antitoxin immunity Gained by active or passive immunization

C. tetani-- Control for children: basic immunization Prevention Active immunization: tetanus toxoid for children: basic immunization DPT(diphtheria toxoid, pertussis vaccine, tetanus toxoid) for a high-risk group : toxoid booster

C. tetani-- Control Urgent prevention Proper care of wounds: surgical debridement Passive immunization: tetanus antitoxin urgent prevention (along with toxoid) As soon as possible Allergic skin test before use

C. tetani– treatment Large dose and early use of TAT because TAT can not neutralize exotoxin that have already bound with receptor on nervous target cell Special treatment administration of antibiotics supportive measures

Pathogen of gas gangrene and food poisoning C. perfringens Pathogen of gas gangrene and food poisoning

C. perfringens --Characteristics Shape and structure Large G+ rods Subterminal endospore Capsule Nonmotile

C. perfringens --Characteristics Cultivation strict anaerobic double zones of hemolysis generation time : 8-10 minutes carbohydrate fermentation---active metabolism Inner zone: θ toxin complete Outer zone: α toxin Incomplete

stormy fermentation

C. perfringens --Characteristics Classification five toxigenic types (A through E) A cause most of human infections + Type α, Alpha β, Beta ε, Epsilon A B C D E ι, Iota

C. perfringens -- Pathogenicity Virulence factors αtoxin produced by all strains the most potent toxin→ exhibits lecithinase activity→ destroys erythrocytes, leukocytes, and platelets,muscle cells, endothelial cell

Increasing of vascular permeability Massive hemolysis and bleeding, tissue necrosis Dysfunction of heart and liver

C. perfringens -- Pathogenicity Virulence factors Enterotoxin produced by types A(most), C, and D heat-labile Toxin of food poisoning Others collagenase, hemolysin, proteinase, DNase (deoxyribonuclease)

C. perfringens -- Pathogenicity Disease Gas gangrene Occurrence Transmission: trauma Pathogens: 60～80％ cases by type A Conditions: localized anaerobic environment Manifestation: sudden outset, emphysema, edema(crepitation) necrotic tissues, foul-smelling, toxemia, shock

C. perfringens -- Pathogenicity Disease Food poisoning transmission: gastrointestinal tract pathogens: type A manifestation: short incubation period (10hrs) cramps and watery diarrhea --- self-limiting

Laboratory diagnosis Quick diagnosis and treatment Direct slide smear Isolation culture Animal test Food poisoning diagnosis

Prevention and control Prompt and extensive surgical debridement of involved area and excision of all devitalized tissue Antibiotics Polyvalent antitoxin Hyperbaric oxygen

C. Botulinum pathogen of botulism

C. botulinum---Characteristics Gram positive rod Subterminal endospore Noncapsule Obligate anaerobe

Racket shaped

C. botulinum--- Pathogenicity Virulence factor— botulinum toxin neurotoxin relatively heat-labile: 100℃, 10min; 80℃, 20min types: A, B, C, D, E, F, G the most potent toxic material known 10,000 times potassium cyanide(KCN)

mechanism of action: Botulinum toxin is absorbed from the gut and binds to receptors of presynaptic membranes of motor neurons blocking the presynaptic release of the neurotransmitter acetylcholine → lack of muscle contraction and flaccid paralysis

Mechanisms of botulinum toxin flaccid paralysis

Sausages, seafood products, sweat bean sauce, and canned food C. botulinum--- Pathogenicity Disease—Botulism Endospore → germinate → toxin → flaccid paralysis Sausages, seafood products, sweat bean sauce, and canned food Food poisoning Infant botulism Wound botulism  Ducks displaying the characteristic flaccid paralysis caused by the disease Honey

C. botulinum--- Pathogenicity Disease Food poisoning transmission: ingestion of toxin-contaminated food manifestation: flaccid paralysis double vision, blepharoplegia ,dysphagia, difficulty in breathing and speaking gastrointestinal symptoms are rare limb muscles rarely involved cause of death: respiratory failure

C. botulinum--- Pathogenicity Disease infant botulism transmission: ingestion of organism-contaminated food(honey) manifestation: constipation, poor feeding, difficulty in sucking and swallowing, weak cry, loss of head control--- Floppy baby prevention: free of honey under 1 year old

C. botulinum--- Pathogenicity Disease wound botulism Rare Transmission: trauma

Control and treatment Destroy the spores in food,preventing spore germination or destroy toxin. Patients with botulism require adequate ventilatory support Trivalent botulinum antitoxin(A,B,E)

C. difficile

C. difficile --- Pathogenicity Virulence factor exotoxin A: enterotoxin exotoxin B: cytotoxin Disease pseudomembranous colitis: dysbacteriosis antibiotic-associated diarrhea

C. difficile --- Control Treatment discontinuation of causative antibiotics administration of sensitive antibiotics Prevention no vaccine use antibiotics only in necessary

non-spore-forming anaerobes

Characteristics include both G+ and G- bacilli and cocci. members of the normal flora cause: endogenous infection 23 genera and 10 genera pathogenic to human

Conditions causing disease Change of habitat Decrease of host defense Dysbacteriosis Local anaerobic environment formation

Characteristics of infections endogenous infection throughout body, most chronic nonspecific manifestations, most pyogenic local abscess ,tissue necrosis, septicemia foul-smelling discharge, sometimes gas formation direct smear positive, aerobic culture negative have no response to some antibiotics such as aminoglycisides

Diseases septicemia infections in central nervous system dental sepsis pulmonary infections intraabdominal infections infections of the female genital tract

Question 1. Make a list of the major pathogenic Clostridial species, indicating the virulence factors and diseases they cause. 2. What are the principle of treatment and prevention for the infection by C.tetani? 3. Make a list of conditions in which can cause disease infected by non-spore-forming anaerobes. 4. What affect do tetanospasmin and botulinum toxin have on muscles? 5. Choose the best answer 1) the primary toxin associated with invasive C.perfringens infection is a. neuraminidase b. alpha toxin c. hyaluronidase d. coagulase 2) a neurotoxin that causes flaccid paralysis is a. tetanospasmin b. botulinum toxin c. αtoxin d. enterotoxin

occurrence development of anaerobic environments (e.g., deep wound) spores → vegetative cells → toxins and invasive enzymes ↓ tissue destruction and necrosis; carbohydrate fermentation and gas (H2; ,CO2) formation and accumulation in the tissue restrict the blood supply (flow) increases the tissue necrosis