Anaerobic Microbe Characteristics

* Cannot live in oxygen, obtain energy from fermentation and not respiration

* Clostridum and normal flora in unusual location are main pathogens

* Resident to skin, mucus in mouth, oropharynx, nasopharynx, URT, large intestine, vagina.

Anaerobes from Endogenous Flora

* Bacteroides

* Pophyromonas

* Prevotella

* Fusobacterium

* Other (peptococcus, peptostreptococcuc, actinomycetes, veillonella, propionibacterium acnes, eubacterium, bifidobacterium)

Bacteroides Characteristics

* Gram negative rods

* Mainly in colon some in mouth

* Resistant to aminoglycoside antibiotics ie gentamicin and kanamycin

* B. fragilis B. thetaiotaomicron, B. melaninogenicus

B. fragilis Characteristics

* Non-spore forming, non-motile, small pleomorphic rod, sometimes coccobacillus

* Resistant to penicillin, clindamycin, metronidazole

* Polysaccharide capsule- antiphagocytic, promotes abscess formation

* Weak LPS endotoxin

* Most aerotolerant, superoxide dismutase and catalase producer

* Intra-abdominal, lung, brain, and pelvic abscess, perotonitis, septicemia, endocarditis

* Produces NA, lipase, protease

Porphyromonas and Prevotella Characteristics

* Produce black iron-containing pigment on blood agar

* Isolated from oral cavity, prevotella also from vagina

* Infections of head, neck, respiratory track, chronic periodontitis, pelvic, abdominal infections.

Fusobacterium Characteristics

* Normal flora in oral cavity

* F. nucleatum and F. necrophorum pathogenic

* Long slender cells with tapered ends

* Fully toxic endotocin- septic shock and vascular collapse

* Similar infections to Bacteroides.

Other Endogenous Anaerobic Genera

* Peptococcus, Peptostreptococcus- mixed anaerobic infections

* Actinomycetes

* Veillonella- oral Gram - coccus. Uncertain pathogenic role

* Propionibacterium acnes- Gram + rod, skin, acne.

* Eubacterium, Bifidobacterium- Gram + rods in fecal flora. Occasionally cause infections.

Endogenous Anaerobes Characteristics

Proximity to colonized mucosal surfaces

Abscesses

Fould smelling gas in tissues

Necrotic Tissue

Mixed infections common

Do not respond to aminoglycosides. Sensitive to clindamycin or metronidazole

Clostridium Characteristics

* Large, Gram +, endospore forming rods

*In soil, GI tract of humans and animals

* Protein exotoxin important virulence

* Important pathogens: C. tetani, perfringens, botulinum, and difficile.

* Usualy exogenous infections from preformed toxins

Tetanus Characteristics

* Caused by Clostridium tetani

* Round temrinal spores in long, narrow, pleomorphic rods

* Motile, peritrichous flagella

* Colonies with "ground glass" appearance, hemolytic, think, spreading growth

Tetanus Pathogenesis and Clinical Picture

* Spores in wound, Organisms germinate, multiply, make toxin

* Necessary: Low Redox potential and mixed bacterial flora

* Toxin (next notecard)

Tetanus Toxin

Intracellular protein released from bacteria by autolysis

Toxin on plasmid

Split into two fragments of increased toxicity

Binds peripheral nerve, internalized, transported to axon to cell body of neuron in spinal cord.

Transports to inhibitory where binds gangliosides, inhbits release of inhibitory neurotransmitter.

Tetanus Clinical Picture

*Results in convulsice conraction of voluntary muscles, initially at site of injury, then jaw.

*Other voluntary msucles may become involved, death due to respiratory failure.

Tetanus Treatment

* Antitoxin, must use before toxin fixted to nervous system

* Surgical debridement of wound site

* Antibiotic

* Booster injection of tetanus toxoid

C. botulinum

Characteristics

Oval, subterminal spores

Large, grayish colonies, hemolysis usually present

Botulism toxin

Three forms: Classical, infant, and wound

A-H antigenic variants of toxin, highly neurotoxic!

Botulism Pathogenesis

Classical form

* Classical is food borne.

* Organism grows anaerobically in food, produces toxin.

* Flaccid paralysis, respiratory failure

* Mortality rate reduced to 10% from 70%

* Rare in US

Botulism Pathogenesis

Wound Form

Rarest form in US.

Wound infected with C botulinum spores.

Toxin produced in vivo.

Botulism Pathogenesis

Infant form

* Infect GI tract of newborns, produces toxin in vivo.

*Often from honey containing spores.

*Low mortality rate (1-2%), 5x more frequent that food borne.

Botulism Toxin

* Inhibits release of acetylcholine at neuromuscular synapses.

*Results in flaccid paralysis.

* From lysogenic conversion

Botulism Treatment

* Treat a ntitoxin against A, B, E variants

* Maintain ventilation w mechanical respirator

* No antibiotics for foodborne but can be used for other forms

Clostridium perfringens Characteristics

* Very lage rods, encapsulated within tissue, non motile

* Spores are rare

* Rapid growth, hemolysis

*  Ferment Carbohy in muscles, produce gas

* Up to 12 toxins produced

C. perfringens Clinical Picture:

Wound infection

* Wound infection, spores germinate, bacteria multiply, produce gas w fermentation.

* Gas distends tissues, messed up blood supply-necrosis via toxins

* As necrosis extends: hemolytic anemia, severe tocemia, death.

C. Perfringes: infections Caused

* Wound (another card details infection)

* Uterine Infection- septic abortion

* Septicemis

* Food poisoning-preformed toxin, mild and common

* Small intestine-Enteritis necroticans, rare, 50 Mortality from necrosis and perfortion

C. perfringen

Treatment

Surgical debridement

Massive antibiotic therapy

Hyperbaric oxygen treatment

Clostridium difficile

Characteristics

*Kept at low levels of normal flora due to competition

* Iatogenic- antibiotics kill bowel floral opening niche for antibiotic resistant flora

* Cytotoxin-diarrhea, kills colon epith cells>pseudomembrane

* Leads to peritonitis, perforation, death.

C. difficile

Diagnosis, treatment

* Diagnose by presence of cytotoxin in stool

* Stop antbiotic causing problem, start fluid relacement, new antibiotic given.

Note: can have diease without previous antibiotic therapy.

Petococcus, peptostreptococcus

Actinomycetes

Veillonella

Propionbacterium acnes

Eubacterium, Bifidobacterium

Characteristics of Engdogenous Anaerobic Infections

Proximity to mucosal surfaces

Frequently abscesses

Foul smelling discharge

Gas in tissues

Necrotic tissue

Frequently mixed

Don't respond to aminoglycosides. Respond to aminoglycosides, metronidazole.