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Micro/Immuno Part 2 > Anaerobic Bacteria > Flashcards

Flashcards in Anaerobic Bacteria Deck (19):

Anaerobic Bacteria

-obligate anaerobes
-can be aerotolerant of facultative
-use other flashcards about fermentation pathways-inefficient, intermediate waste product,leave energy in final, waste is organic acid or alcohol, repertoires


common sources of pathogen 1

-normal flora escape normal compartment
-actinomyces, B corrodens, P melaninogenica in mouth
-B fragilis in colon and vagina
-abcess fills with bacteria and dead neutrophils, swells, becomes painful


common source of pathogens 2

-soil-spores enter through wounds, germinate, produce exotoxins
-C tetani
-C perfringens
-C botulinum


Route of entry 2 from soil

-spores germinate in vacuum packed foods
-C perfringens in food poisoning:bacteria briefly survive in gut and release enterotoxin
-C botulinum in infants-bacteria survive briefly in gut and release neurotoxin
-Botulism in foodborne-bacteria do not survive in gut but already filled food with neurotoxin


anaerobes in lab

1. sample must be handles anaerobically and labeled as such
2. standard clinical labs are anaerobic culture, gram stain, gas chromatography


liquid culture

-innoculate test tube of media
-add a reducing agent like thoglycolate to eliminate dissolved oxygen
-fill completely, stopper tightly and incubate WITHOUT SHAKING
-aerobe grows on top, anaerobe on bottom, both in middle


agar plates

-quickly streak onto agar media with usual benchtop sterile technique
-place plates in anaerobic culture jar
-add a chemical system to remove oxygen from jar's atmosphere and color indicate successful removal (Gas-Pak)
-airtight seal
-place whole jar in incubator for 48 hours
-note that colonies will die very shortly after removal from jar unless using a glovebox



-box with oxygen free atm
-airlock for bringing plates and instruments in and out (flood with nitrogen)
-gloves attached to box for manipulations within


Identifying anaerobes

-gram stain
-chemical testing-ability to ferment, hydrolize various macromolecules
-gas chromatography


gas chromatography

-analyzes organic acids being produced by the anaerobes fermentation pathways
-extracts from culture or pus sample are run against control mixes


treatment of anaerobic infections

-surgical care for abscess
-antitoxin for toxigenic disease-tetanus/botulism
-antibiotics-penicillin G, cefotoxin, chloramphenicol, clindamycin
-metronidazole-specific for anaerobic bacteria-broken down to active form where the bacteria are



-clostridium all gram pos and rods and in soil, except C dif
-spores to survive transfer
-all make exotoxins



-gram neg anaerobic bacilli-normal flora gone bad
-bacteriodes and prevotella
-no spores



-gram pos
-long rod
-no spores


C. tetani

-spores are environmental: soil, dust, manure, some human skin and GI
-gram pos
-transmitted to humans by soil contamination of wounds-splinters, thorns, punctures, IV septic surgery, septic handling of umbilical cord
-insertion beneath the skin surface limits air contact
-spores germinate- vegetative cells release exotoxin tetanospasmin
-large and small subunit, small unit delivered, retrograde axonal transport to CNS
-acts as protease, cleaves synaptobrevin in inhibitory motor nerves of CNS, no inhibitory motor neuron activity
-can't stop contracting


generalized tetanus

-bacteria from locus of infection
-exotoxin tetanospasmin enters bloodstream
->50% untreated mortality from resp failure
-21-31% treated mortality
-vaccination can save


C dif

-gram pos spore forming rod
-pseudomembranous colitis
-disrupts normal flora
-normal gut flora for 3% general pop, 30% hospitalized
-fecal oral, especially nosocomial from spores on hospital instruments or on hands of HCWs


c dif pathogenesis

-recent course of antibiotics or cancer chemotherapeutics supresses other normal flora
-germinating cells release exotoxin A, disrupts tight junctions, causing swelling and IF
-exotoxin B is major toxin, disrupts cytoskeleton by depolymerizing actin, kills surrounding cells
-more virulent and drug resistant in 2001-2002
-mortality increased from 6%


c dif diagnosis and treatment

-patches of dead and dying cells appear as yellow white plaques
-withdraw initial antibiotic cures 20%
-oral metronidazole or vancomycin
-surgical resection or removal of the colon may be required
-toxic megacolon or colonic perforation may occur