Anaerobic BacteriaAnaerobic Bacteria

CategoryCategory

Spore-forming: Spore-forming:

rod, Gram (+)--- Clostridiumrod, Gram (+)--- Clostridium Nonspore-forming: Nonspore-forming:

see next slides see next slides

Spore-Spore-forming:forming:

rod, Gram (+)--- Clostridiumrod, Gram (+)--- Clostridium

Nonspore-forming:Nonspore-forming:Rod, Gram (+)Rod, Gram (+) PropionibacteriumPropionibacterium 丙酸菌属

Bifidobacterium Bifidobacterium Lactobacillus Lactobacillus

EubacteriumEubacterium ActinomycesActinomyces

Rod, Gram (-)Rod, Gram (-) BacteroidesBacteroides

Fusobacterium Fusobacterium 梭菌属 CampylobacterCampylobacter

Cocci, Gram (+)Cocci, Gram (+) Peptococcus Peptococcus Peptostreptococcus Peptostreptococcus

Cocci, Gram (-)Cocci, Gram (-) VeillonellaVeillonella

CategoryCategory

Clostridium SpeciesClostridium Species

The clostridia are opportunistic The clostridia are opportunistic pathogens. Nonetheless, they are pathogens. Nonetheless, they are responsible for some of the deadliest responsible for some of the deadliest diseases including diseases including gas gangrene, gas gangrene, tetanus and botulismtetanus and botulism. Less life-. Less life-threatening diseases include threatening diseases include pseudomembranous colitispseudomembranous colitis (PC) and (PC) and food poisoning. food poisoning.

cause disease primarily through the cause disease primarily through the production of numerous exotoxins.production of numerous exotoxins.

perfringens, tetani, botulinum, difficileperfringens, tetani, botulinum, difficile

Clostridium TetaniClostridium Tetani

Pathogenesis of tetanus caused by C tetani

General introductionGeneral introduction

C tetaniC tetani is found worldwide. is found worldwide. Ubiquitous in Ubiquitous in soilsoil, it is occasionally , it is occasionally found in found in intestinal flora of humans intestinal flora of humans and animalsand animals

C.C.tetanitetani is the cause of is the cause of tetanustetanus,or ,or lockjawlockjaw. When spores are introduced . When spores are introduced into wounds by contaminated soil or into wounds by contaminated soil or foreign objects such as nails or glass foreign objects such as nails or glass splinterssplinters

BIOCHEMICAL CHARACTERISTICSBIOCHEMICAL CHARACTERISTICS

MorphologyMorphology: long and slender; : long and slender; peritrichous flagella,no capsule, peritrichous flagella,no capsule, terminal located round terminal located round spore(drum-stick apperance), spore(drum-stick apperance), its diameter greater than its diameter greater than vegetative cellvegetative cell..

CultureCulture:obligate anaerobic; :obligate anaerobic; Gram(+); swarming occures on Gram(+); swarming occures on blood agar, faint hemolysis.blood agar, faint hemolysis.

Biochemical activities:Biochemical activities:does does not ferment any carbohydrate not ferment any carbohydrate and proteins.and proteins.

ResistanceResistance: tolerate boiling for : tolerate boiling for 60 min.alive several ten years in 60 min.alive several ten years in soil.soil.

ClassificationClassification and Antigenic and Antigenic Types: Types: C tetani C tetani is the only is the only species. There are no serotypesspecies. There are no serotypes

2-5 x 0.3-0.5um2-5 x 0.3-0.5um

PathogenicityPathogenicity

No invasiveness; toxemia No invasiveness; toxemia (exogenous infection(exogenous infection ））

produces two exotoxins: produces two exotoxins: tetanolysin, and tetanolysin, and tetanospasmintetanospasmin(a kind of (a kind of neurotoxin, toxicity neurotoxin, toxicity strong)strong)

The actions of The actions of tetanospasmintetanospasmin are are complex and involve three complex and involve three components of the components of the nervous system: nervous system: central central motor controlmotor control, , autonomic autonomic functionfunction, and the , and the neuromuscular junctionneuromuscular junction..

retrograde transport retrograde transport to (CNS)to (CNS)

delitescencedelitescence ：： a few a few days to several days to several weeksweeks

The two animal The two animal species most species most susceptible to this susceptible to this toxemia are horses toxemia are horses and and humanshumans..

Clostridium tetaniClostridium tetani --TetanospasminTetanospasmin

disseminates systemically disseminates systemically binds to ganglioside receptors binds to ganglioside receptors

• inhibitory neurones in CNSinhibitory neurones in CNS glycine glycine

• neurotransmitterneurotransmitter stops nerve impulse to muscles stops nerve impulse to muscles spastic paralysisspastic paralysis 痉挛性麻痹 severe muscle contractions and severe muscle contractions and

spasms spasms can be fatalcan be fatal

TetanospasminTetanospasmin

Clinical ManifestationsClinical Manifestations The initial symptom is cramping and The initial symptom is cramping and

twitching of muscles around a wound. The twitching of muscles around a wound. The patient usually has patient usually has no feverno fever but sweats but sweats profusely and begins to experience pain, profusely and begins to experience pain, especially in the area of the wound and especially in the area of the wound and around the neck and jaw muscles around the neck and jaw muscles (trismus)(trismus)..

Portions of the body may become extremely Portions of the body may become extremely rigid, and rigid, and opisthotonosopisthotonos 角弓反张 (a spasm (a spasm in which the head and heels are bent in which the head and heels are bent backward and the body bowed forward) is backward and the body bowed forward) is common.common.

Complications include fractures, bowel Complications include fractures, bowel impaction, intramuscular hematoma, muscle impaction, intramuscular hematoma, muscle ruptures, and pulmonary, renal, and cardiac ruptures, and pulmonary, renal, and cardiac problemsproblems

Clinical ManifestationsClinical ManifestationsDISEASEDISEASE CLINCAL MANIFESTATIONSACLINCAL MANIFESTATIONSA

GeneralizedGeneralized Involvement of bulbar and paraspinal Involvement of bulbar and paraspinal muscles(trismus or lockjaw, risus sardonicus, muscles(trismus or lockjaw, risus sardonicus, difficulty swallowing, irritability, difficulty swallowing, irritability, opisthotonos);involvement of autonomic opisthotonos);involvement of autonomic nervous system(sweating, hyper thermia, nervous system(sweating, hyper thermia, cardiac arrhythmias, fluctuations in blood cardiac arrhythmias, fluctuations in blood pressure)pressure)

CephalicCephalic Primary infection in head,particularly Primary infection in head,particularly ear;isolated or combined involvement of cranial ear;isolated or combined involvement of cranial nerves, particularly seventh cranial nerve; very nerves, particularly seventh cranial nerve; very poor prognosispoor prognosis

LocalizedLocalized Involvement of muscles in area of primary Involvement of muscles in area of primary injury; infection may precede generalized injury; infection may precede generalized disease; favorable prognosisdisease; favorable prognosis

NeonatalNeonatal Generalized disease in neonates; infection Generalized disease in neonates; infection typically originates from umbilicaltypically originates from umbilical 脐带stump;very poor prognosis in infants whose stump;very poor prognosis in infants whose mothers are nonimmunemothers are nonimmune

EpidemiologyEpidemiology 1 1 million cases of tetanus occur annually in the million cases of tetanus occur annually in the

world,with a mortality rate ranging from20% to world,with a mortality rate ranging from20% to 50%. But rare in most developed countries. 50%. But rare in most developed countries.

In some In some developing countriesdeveloping countries, tetanus is still , tetanus is still one of the ten leading causes of death, and one of the ten leading causes of death, and neonatal tetanus accounts for approximately neonatal tetanus accounts for approximately one-half of the cases worldwide.one-half of the cases worldwide.

In less developed countries, approximate In less developed countries, approximate mortality rates remain 85% for neonatal mortality rates remain 85% for neonatal tetanus and 50% for nonneonatal tetanus. tetanus and 50% for nonneonatal tetanus.

In the United States, intravenous drug abusers In the United States, intravenous drug abusers have become another population with an have become another population with an increasing incidence of clinical tetanusincreasing incidence of clinical tetanus

In untreated tetanus, the fatality rate is In untreated tetanus, the fatality rate is 90%90% for the newborn and for the newborn and 40%40% for adults. for adults.

ImmunityImmunity

Humoral immunityHumoral immunity(antitoxin)(antitoxin) There is little, if any, inate immunity There is little, if any, inate immunity

and the disease does not produce and the disease does not produce immunity in the patient. immunity in the patient.

Active immunity follows vaccination Active immunity follows vaccination with tetanus with tetanus toxoidtoxoid

DiagnosisDiagnosis Diagnosis is primarily by Diagnosis is primarily by the clinical the clinical

symptoms (above).symptoms (above). The wound may not The wound may not be obvious. be obvious.

C tetani can be recovered from the C tetani can be recovered from the wound in only about one-third of the wound in only about one-third of the cases.cases.

It is important for the clinician to be It is important for the clinician to be aware that toxigenic strains of C tetani aware that toxigenic strains of C tetani can grow actively in the wound of an can grow actively in the wound of an immunized person.immunized person.

Numerous syndromes, including Numerous syndromes, including rabies rabies and meningitis,and meningitis, have symptoms similar have symptoms similar to those of tetanus and must be to those of tetanus and must be considered in the differential diagnosis.considered in the differential diagnosis.

• infantinfant• DPT (diptheria, pertussis, tetanus)DPT (diptheria, pertussis, tetanus)• tetanus toxoid tetanus toxoid

– antigenicantigenic– no exotoxic activityno exotoxic activity

VaccinationVaccination

ControlControl The offending organism must be The offending organism must be

removed by local removed by local debridemendebridemen 清创术

toxoid toxoid TATTAT; Metronidazole (For more ; Metronidazole (For more

serious wounds)serious wounds) AIDSAIDS patients may not respond patients may not respond

to prophylactic injections of to prophylactic injections of tetanus toxoidtetanus toxoid

C. perfringensC. perfringens

• soil, fecal contaminationsoil, fecal contamination• gas gangrenegas gangrene

– swelling of tissues swelling of tissues – gas releasegas release

* fermentation productsfermentation products• wound contaminationwound contamination

ToxinsToxinstoxintoxin Biological Biological

FeatureFeatureTypes of ToxinsTypes of Toxins

AA BB CC DD EE

lecithinaselecithinase; increase the ; increase the vascular permeability; vascular permeability; hemolytic; produces hemolytic; produces necrotizing activitynecrotizing activity

++ ++ ++ ++ ++

Necrotizing activity, Necrotizing activity, induces hypertension induces hypertension by causing release of by causing release of catecholamines.catecholamines.

－－ ++ ++ －－ －－

increase the increase the permeability of permeability of gastrointestinal wallgastrointestinal wall

－－ －－ －－ ++ －－

Necrotizing activity; Necrotizing activity; increase the vascular increase the vascular permeability permeability

－－ －－ －－ －－ ++

ToxinsToxins Many of these toxins have lethal, Many of these toxins have lethal,

necrotizing, and hemolytic properties;necrotizing, and hemolytic properties; The alpha toxin produced by all types of The alpha toxin produced by all types of C. C.

perfringens,perfringens, is a lecithinase that lyses is a lecithinase that lyses erythrocytes, platelets, leukocytes, and erythrocytes, platelets, leukocytes, and endothelial cells. And its lethal action is endothelial cells. And its lethal action is proportionate to the rate at which it splits proportionate to the rate at which it splits lecithin to phosphorylcholine and lecithin to phosphorylcholine and diglyceride.diglyceride.

The theta toxin has similar hemolytic and The theta toxin has similar hemolytic and necrotizing effects.necrotizing effects.

DNAase, hyaluronidase, a collagenase are DNAase, hyaluronidase, a collagenase are also producedalso produced

EnterotoxinEnterotoxin Many strains of type A produce Many strains of type A produce

enterotoxin, which is a heat-labile protein enterotoxin, which is a heat-labile protein and destroyed immediately at 100 ℃.and destroyed immediately at 100 ℃.

Trypsin treatment enhances the toxin Trypsin treatment enhances the toxin activity threefold.activity threefold.

The toxin is produced primarily by type A The toxin is produced primarily by type A strains but also by a few type C and D strains but also by a few type C and D strains.strains.

It disrupts ion transport in the It disrupts ion transport in the ileum(primarily) and jejunum by inserting ileum(primarily) and jejunum by inserting into the cell membrane and altering into the cell membrane and altering membrane permeability.membrane permeability.

As superantigen. As superantigen.

•Tissue degrading enzymes Tissue degrading enzymes – lecithinase [lecithinase [ toxin] toxin]– proteolytic enzymesproteolytic enzymes– saccharolytic enzymessaccharolytic enzymes

• Destruction of blood vessels Destruction of blood vessels • Tissue necrosisTissue necrosis• Anaerobic environment created Anaerobic environment created • Organism spreadsOrganism spreads

PathogenesisPathogenesis

Without treatment death Without treatment death occurs within 2 daysoccurs within 2 days effective antibiotic therapyeffective antibiotic therapy debridement debridement anti-toxinanti-toxin amputation & death is rareamputation & death is rare

Gas gangreneGas gangrene

Gas gangreneGas gangrene is a life-threatening disease with is a life-threatening disease with a poor prognosis and often fatal outcome. a poor prognosis and often fatal outcome.

Initial trauma to host tissue damages muscle and Initial trauma to host tissue damages muscle and impairs blood supply----lack of oxygenation impairs blood supply----lack of oxygenation

Initial symptomsInitial symptoms : : fever fever and pain in the infected and pain in the infected tissue.; more local tissue necrosis and systemic tissue.; more local tissue necrosis and systemic toxemia. Infected muscle is discolored (purple toxemia. Infected muscle is discolored (purple mottling) and edematous and produces a mottling) and edematous and produces a foulfoul--smelling exudate; gas smelling exudate; gas bubblesbubbles form from the form from the products of anaerobic fermentation. products of anaerobic fermentation.

Gas gangreneGas gangrene

As capillary permeability increases, As capillary permeability increases, the accumulation of fluid increases, the accumulation of fluid increases, and venous return eventually is and venous return eventually is curtailed. curtailed.

As more tissue becomes involved, As more tissue becomes involved, the clostridia multiply within the the clostridia multiply within the increasing area of dead tissue, increasing area of dead tissue, releasing more toxins into the local releasing more toxins into the local tissue and the systemic circulation. tissue and the systemic circulation.

Food poisoningFood poisoning

Enterotoxin producing strainsEnterotoxin producing strains.. These bacteria are found in These bacteria are found in

mammalian mammalian faeces and soilfaeces and soil. . Small numbers of the bacteria may Small numbers of the bacteria may

also be found in foods and they may also be found in foods and they may propagate rapidly to dangerous propagate rapidly to dangerous concentrations if the food is concentrations if the food is improperly stored and handled. improperly stored and handled.

Food poisoningFood poisoning

more than 10more than 1088 vegetative cells are vegetative cells are ingested and sporulate in the gut, the ingested and sporulate in the gut, the toxins can act rapidly in the body, toxins can act rapidly in the body, causing severe diarrhea in 6-18 hours, causing severe diarrhea in 6-18 hours, dysentery, gangrene, muscle infections dysentery, gangrene, muscle infections

The action of The action of C. perfringensC. perfringens enterotoxin enterotoxin involves marked hypersecretion in the involves marked hypersecretion in the jejunum and ileum, with loss of fluids jejunum and ileum, with loss of fluids and electrolytes in diarrhea.and electrolytes in diarrhea.

Cellulitis, FasciitisCellulitis, Fasciitis

Cellulitis, FasciitisCellulitis, Fasciitis Fasciitis : a rapidly progressive, Fasciitis : a rapidly progressive,

destructive process in which the destructive process in which the organisms spread through fascial plan es.organisms spread through fascial plan es.

Fasciitis causes suppuration and the Fasciitis causes suppuration and the formation of gasformation of gas

Absense of muscle involvementAbsense of muscle involvement rapidityrapidity

Necrotizing EnteritisNecrotizing Enteritis Rare, acute necrotizing process in the Rare, acute necrotizing process in the

jejunumjejunum Abdominal pain, bloody diarrhea, shock, and Abdominal pain, bloody diarrhea, shock, and

peritonitisperitonitis Mortality: 50%Mortality: 50% Beta-toxin-producing Beta-toxin-producing C. perfringensC. perfringens type C type C

SepticemiaSepticemia

Who is at risk?Who is at risk?

Surgical patientsSurgical patients; patient after ; patient after trauma with soil contamination.trauma with soil contamination.

People who ingest contaminated People who ingest contaminated meat productsmeat products (without proper (without proper refrigeration or reheating to refrigeration or reheating to inactivate endotoxin)inactivate endotoxin)

EpidemiologyEpidemiology

C. perfringensC. perfringens type A: type A: the intestinal the intestinal tract of humans and animals, soil and tract of humans and animals, soil and water contaminated with feces. water contaminated with feces. forms spores under adverse forms spores under adverse environmental conditions and can environmental conditions and can survive for prolonged periods.survive for prolonged periods.

Type B to E strainsType B to E strains colonize the colonize the intestinal tract of animals and intestinal tract of animals and occasionally humans.occasionally humans.

EpidemiologyEpidemiology

Type AType A: gas gangrene, soft tissue : gas gangrene, soft tissue infections and food poisoninginfections and food poisoning

Type CType C: enteritis; necroticans: enteritis; necroticans

• lecithinase productionlecithinase production

Laboratory identification

Double Hemolysis CirclesDouble Hemolysis Circles

C. botulinumC. botulinum

Biological FeaturesBiological Features

AnaerobicAnaerobic Gram-positiveGram-positive rod-shapedrod-shaped sporeformersporeformer produces a protein neurotoxic.produces a protein neurotoxic. soil, sediments of lakes, ponds, soil, sediments of lakes, ponds,

decaying vegetation.decaying vegetation. intestinal tracts of birds, mammals intestinal tracts of birds, mammals

and fish.and fish.

---A, B, C1, D, E, F, and G.---type A. 62% ---Not all produce toxin.---C and D not ---G plasmid encoded.

DivisionDivision

---spores heat resistant. canning. anaerobic environment ---Botulism eating uncooked foods spores---GI, duodenum, blood stream, neuromuscular synapses.

TransmissionTransmission

---bacterial protease ---light chain,A,50 kDa; heavy chain,100kDa.---disulfide bond. ---A potent toxin

Virulence factorsVirulence factors

Botulinum toxinBotulinum toxin

binds peripheral nerve receptorsbinds peripheral nerve receptors• acetylcholine neurotransmitteracetylcholine neurotransmitter

inhibits nerve impulses inhibits nerve impulses flaccid paralysisflaccid paralysis death death

• respiratory respiratory • cardiac failurecardiac failure

Botulinum toxinBotulinum toxin

BioterrorismBioterrorism• not an infectionnot an infection• resembles a chemical attack resembles a chemical attack • 10 ng can kill a normal adult10 ng can kill a normal adult

---4: foodborne, infant, wound, undetermined. ---Certain foods; wound not.---Foodborne botulism, consumption.---Infant botulism, 1976, under 12m. ---ingestion, colonize and produce toxin in the intestinal tract of infants. honey. ---increased.---internationally recognized.

EpidemiologyEpidemiology

---18-36 hours: ---weakness, dizziness,dryness of the mouth. ---Nausea,vomiting. ---Neurologic features: blurred vision, inability to swallow, difficulty in speech, descending weakness of skeletal muscles, respiratory paralysis.

Clinical syndromesClinical syndromes

BotulismBotulism(( 肉毒中毒肉毒中毒 ))

food poisoningfood poisoning • rarerare• fatalfatal

germination of spore germination of spore inadequately sterilized canned inadequately sterilized canned

food food • homehome

not an infectionnot an infection

Infection with Infection with C. botulinumC. botulinum

Neonatal botulismNeonatal botulism• uncommonuncommon• the predominant form of the predominant form of

botulismbotulism• colonization occurscolonization occurs

no normal flora to competeno normal flora to compete unlike adultunlike adult

WoundsWounds

•extremely rareextremely rare•an infectionan infection

ImmunityImmunity ------specifically neutralized, specifically neutralized, antitoxinantitoxin. . ---toxoided, make good antigens.---toxoided, make good antigens.---does not develop, amount toxic. ---does not develop, amount toxic. ---Repeated occurrence. ---Repeated occurrence. ---Once bound, unaffected by antitoxin.---Once bound, unaffected by antitoxin.---circulating toxin ,neutralized , injection ---circulating toxin ,neutralized , injection

of antitoxin.of antitoxin.---treated immediately with antiserum. ---treated immediately with antiserum. ------multivalent multivalent

toxoid,unjustified,infrequency. toxoid,unjustified,infrequency. experimental vaccine. experimental vaccine.

DiagnosisDiagnosis

---by clinical symptoms alone---differentiation difficult. --- most direct and effective: serum or feces. ---most sensitive and widely used: mouse neutralization test. 48h. Culturing of specimens 5-7d.

TreatmentTreatment

Individuals known to have ingested food Individuals known to have ingested food with botulism should be treated with botulism should be treated immediately with antiserum. immediately with antiserum.

antibiotic therapy (if infectionantibiotic therapy (if infection))• Vaccination will not protect hosts Vaccination will not protect hosts

from botulism, however passive from botulism, however passive immunisation with antibody is the immunisation with antibody is the treatment of choice for cases of treatment of choice for cases of botulism. botulism.

Prevention Prevention

------proper food handling and preparation. proper food handling and preparation.

--- spores survive boiling (100 degrees at --- spores survive boiling (100 degrees at 1 atm) 1h. 1 atm) 1h.

---toxin heat-labile, boiling or intense ---toxin heat-labile, boiling or intense heating, inactivate the toxin. heating, inactivate the toxin.

------bulge, gas, spoiledbulge, gas, spoiled..

C. difficileC. difficile

• After antibiotic use After antibiotic use • Intestinal normal flora --greatly decreasedIntestinal normal flora --greatly decreased• Colonization occurs Colonization occurs • Enterotoxin secreted Enterotoxin secreted • Pseudomembanous colitis Pseudomembanous colitis

Pseudomembranous ColitisPseudomembranous Colitis

Pseudomembranous colitis (PC) results Pseudomembranous colitis (PC) results predominantly as a consequence of the predominantly as a consequence of the elimination of normal intestinal flora elimination of normal intestinal flora through antibiotic therapy. through antibiotic therapy.

Symptoms include Symptoms include abdominal abdominal pain with pain with a a watery diarrheawatery diarrhea and leukocytosis. and leukocytosis. ""PseudomembranesPseudomembranes" consisting of " consisting of fibrin, mucus and leukocytes can be fibrin, mucus and leukocytes can be observed by colonoscopy. observed by colonoscopy.

Untreated pseudomembranous colitis Untreated pseudomembranous colitis can be fatal in about can be fatal in about 27-44%.27-44%.

TherapyTherapy

Discontinuation of initial antibiotic Discontinuation of initial antibiotic (e.g. ampicillin)(e.g. ampicillin)

Specific antibiotic therapy (e.g. Specific antibiotic therapy (e.g. vancomycin)vancomycin)

• no oxidative phosphorylationno oxidative phosphorylation• fermentationfermentation• killed by oxygenkilled by oxygen• lack certain enzymeslack certain enzymes

– superoxide dismutase superoxide dismutase * OO22

--+2H+2H++ H H22OO2 2

– catalase catalase * HH22OO2 2 H H220 + O0 + O22

– peroxidase peroxidase * HH22OO22 H H2200 /NAD to NADH/NAD to NADH

Obligate Obligate (strict)(strict) anaerobes anaerobes

Strict anaerobe infectious Strict anaerobe infectious diseasedisease

Sites throughout body Sites throughout body Muscle, cutaneous/sub-cutaneous Muscle, cutaneous/sub-cutaneous

necrosisnecrosis AbscessesAbscesses

Bacterial Flora of the BodyBacterial Flora of the BodySiteSite Total BacteriaTotal Bacteria RatioRatio

(per/ml or gm)(per/ml or gm) Anaerobes:Aerobes Anaerobes:Aerobes

Upper AirwayUpper AirwayNasal WashingsNasal Washings101033-10-1044 3-5:13-5:1SalivaSaliva 101088-10-1099 1:11:1Tooth SurfaceTooth Surface 10101010-10-101111 1:11:1Gingival CreviceGingival Crevice 10101111-10-101212 1000:1 1000:1

  Gastrointestinal TractGastrointestinal Tract

Stomach Stomach 101022-10-1055 1:11:1Small BowelSmall Bowel 101022-10-1044 1:11:1IleumIleum 101044-10-1077 1:11:1ColonColon 10101111-10-101212 1000:11000:1

  Female Genital TractFemale Genital Tract

EndocervixEndocervix 101088-10-1099 3-5:13-5:1VaginaVagina 101088-10-1099 3-5:13-5:1

Problems in identification of Problems in identification of anaerobic infectionsanaerobic infections

• air in sample (sampling, transportation)air in sample (sampling, transportation)– no growthno growth

• identification takes several days or longeridentification takes several days or longer– limiting usefulnesslimiting usefulness

• often derived from normal flora often derived from normal flora – sample contamination can confuse sample contamination can confuse

Virulence FactorsVirulence Factors

1.1. Anti-phagocytic capsuleAnti-phagocytic capsule• Also promote abscess formationAlso promote abscess formation

2.2. Tissue destructive enzymesTissue destructive enzymes• B. fragilisB. fragilis produces variety of enzymes produces variety of enzymes

(lipases, proteases, collagenases) that (lipases, proteases, collagenases) that destroy tissue destroy tissue Abscess Formation Abscess Formation

3.3. Beta-lactamase productionBeta-lactamase production• B. fragilis B. fragilis – protect themselves and other – protect themselves and other

species in mixed infectionsspecies in mixed infections

4.4. Superoxide dismutase productionSuperoxide dismutase production• Protects bacteria from toxic OProtects bacteria from toxic O22 radicals as radicals as

they move out of usual nichethey move out of usual niche

Characteristics of Anaerobic InfectionsCharacteristics of Anaerobic Infections

1.1. Most pathogenic anaerobes are Most pathogenic anaerobes are usually commensalsusually commensals• Originate from our Originate from our own floraown flora

2.2. Predisposing ConditionsPredisposing Conditions• Breeches in the mucocutaneous barrier Breeches in the mucocutaneous barrier

displace normal floradisplace normal flora• Compromised vascular supplyCompromised vascular supply• Trauma with tissue destructionTrauma with tissue destruction• Antecedent infectionAntecedent infection

Characteristics of Anaerobic Characteristics of Anaerobic InfectionsInfections

3. 3. Complex FloraComplex Flora Multiple speciesMultiple species

• Abdominal Infection Abdominal Infection Avg Avg of 5 speciesof 5 species

3 anaerobic3 anaerobic 2 aerobic2 aerobic

• Less complex then nl floraLess complex then nl flora• Fecal flora 400 different Fecal flora 400 different

species species Those predominant in stool Those predominant in stool

are not infecting species are not infecting species • Veillonella, Veillonella,

Bifidobacterium Bifidobacterium rarely rarely pathogenicpathogenic

• Species uniquely suited to Species uniquely suited to cause infection cause infection predominatepredominate

4.4. Synergistic Mixture Synergistic Mixture of Aerobesof Aerobes & & AnaerobesAnaerobes

E. coliE. coli Consume O Consume O22

• Allow growth Allow growth of of anaerobesanaerobes

Anaerobes Anaerobes promote promote growth of other growth of other bacteria by being bacteria by being antiphagocytic and antiphagocytic and producing B-producing B-lactamaseslactamases

Clues to Anaerobic InfectionClues to Anaerobic Infection

1.1. Infections in continuity to mucosal Infections in continuity to mucosal surfacessurfaces

2.2. Infections with tissue necrosis and Infections with tissue necrosis and abscess formation abscess formation

3.3. Putrid odorPutrid odor4.4. Gas in tissuesGas in tissues5.5. Polymicrobial floraPolymicrobial flora6.6. Failure to grow in the lab Failure to grow in the lab

BIOCHEMICAL KITS BIOCHEMICAL KITS • e.g. API SYSTEMe.g. API SYSTEM

GAS CHROMATOGRAPHYGAS CHROMATOGRAPHY• volatile fermentation productsvolatile fermentation products

Bacteroides fragilisBacteroides fragilis

• Major disease causing strict anaerobic Major disease causing strict anaerobic after abdominal surgeryafter abdominal surgery non-spore-formernon-spore-former

• Prominent capsuleProminent capsule– anti-phagocyticanti-phagocytic– abscess formationabscess formation

• Endotoxin Endotoxin – low toxicitylow toxicity– structure different than other structure different than other lipolysaccharide lipolysaccharide

• EnterobacteriaceaeEnterobacteriaceae (facultative anaerobes) (facultative anaerobes) – commonly cause diseasecommonly cause disease– low numbers gut floralow numbers gut flora

• Strict anaerobesStrict anaerobes – much less commonly cause disease much less commonly cause disease – high numbers gut florahigh numbers gut flora .