Non spore forming anaerobic bacteria

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2. Anaerobic bacteria

  • Gram positive sporulating bacilli
  • Gram positive non-sporulating bacilli
  • Gram negative non-sporulating bacilli(nm)
  • Gram negative non-sporulating bacilli(m)
  • Gram positive anaerobic cocci
  • Gram negative anaerobic cocci

3. Gram positive non-sporulating bacilli:

  • Actinomyces
  • Bifidobacterium
  • Proprionbacterium ( Corynebacterium)
  • Arachnia ( Proprionbacterium propionica )
  • Eubacterium

4. Gram negative non-sporulating bacilli.( non motile)

  • Bacteroides (Bacteroides fragilis).
  • Fusobacterium
  • Porphyromonas
  • Prevotella

5. Gram negative non-sporulating bacilli (motile)

  • Treponema
  • Borrelia
  • Campylobacter

6. Anaerobic cocci

  • Gram positive anaerobic cocci
  • Peptostreptococcus
  • Peptococcus
  • Gram negative anaerobic cocci
  • Veillonella
  • Acidaminococcus

7. Gram negative non-sporulating bacilli

  • Prototype-Bacteroides fragilis
  • Will grow in 20% bile
  • On blood agar it is non-haemolytic
  • Gram negative and pleumorphic
  • Resistant to kanamycin, vancomycin and colistin
  • Catalase positive
  • Pigmented strains were formerly calledBacteroides melaninogenicus
  • But have now been re-classified to two new Genera:
  • Prevotellawhich is saccharolytic
  • Porphyromonaswhich is asaccharolytic.

8. Fusobacterium

  • Long thin gram negative rods with pointed ends
  • May or may not grow in 20% bile
  • Catalase negative
  • Sensitive to kanamycin and colistin but resistant to vancomycin

9. Provisional identification of non-spore forming anaerobic Gram negative bacilli

  • Growth inUV-light
  • 20% bilekanamycinvancomycincolistinpigmentfluorecsence catalase
  • B.fragilisYesResist.Resist.Resist.NoNo+
  • PrevotellaNoResistSens.Sens.YesYes-
  • Porphyromons NoResist.Sens.Sens.YesYes-
  • FusobacteriumNoSensit.ResistSens.NoNo-

10. Anaerobes as normal flora

  • Anaerobic bacteria are the predominant normal human bacterial flora.
  • Bacteroides and Prevotera spp are the most predominant.
  • In the mouth : Prevotella, Fusobacterium, Porphylomonas and anaerobic cocci.
  • In stomach:mostly facultative anaerobes in low counts.
  • Terminal ileum:Bacteroides, Bifidobacterium and facultative anaerobes.
  • Colon:Highest concentration of bacteria, mostly Bacteroides, Fusobacteria,Clostridia, anaerobic cocci, Bifidobacteria and facultative anaerobes.
  • Vagina : mostly anaerobes especially gram positive rods, but may vary depending on menstral cycle, pregnancy, menopause and other gynaecological conditions.
  • Distal urethraboth male and female have small numbers of Bacteroides, Prevotera and Fusobacteria spp.
  • Uterine cavity: Sterile

11. Pathogenesis

  • Synergy with aerobic bacteria is essential in the pathogenesis
  • But also there are several virulence factors involved in the pathogenesis
  • Capsular polysaccharide inhibits phagocytosis, enhences abscess formation.
  • Pili and fimbriae enhence adherence
  • Lipopolysaccharide endotoxin enhences abscess formation.
  • Succinic acid-inhibits phagocytosis
  • Enzymes like hyaluronidase, collagenase, neuraminidase, heparinase, fibrinolysins etc

12. ClinicalClues for anaerobic infections

  • -Foul smelling pus
  • -Proximity to mucosal surfaces.
  • -Massive necrotic tissues
  • -Septic thrombophlebitis
  • - Infection following human bite
  • Septic abortion
  • Infection following lower GIT and female genital surgery

13. Laboratory clues

  • Purulent exudate but no bacterial growth on culture
  • Foul smelling culture plates
  • Colonies fluoresce brick red under UV light
  • Failure to grow organisms seen on gram stain.

14. Infections

  • Oral cavity eg dental abscess, periodontal disease, acute gingivitis.
  • Intra abdominal eg. peritonitis, abcsesses etc
  • Sinuses(chronic sinusitis)
  • Female genital tract eg pelvic inflamatory disease(PID), endometritis,pelvic abcsess, bacterial vaginosis etc.
  • Pleuro-pulmonary infections eg aspiration pneumonia, lung abcsess, empyema etc
  • Bacteraemia and septicaemia and metastatic abcsesses

15. Laboratory Diagnosis.

  • Isolation: good specimen, use selective and non-selective media, good anaerobic incubation and identify by biochemical tests and gas-liquid-chromatography and molecular techniques if available.

16. Treatment

  • Surgical drainage and removal of dead and necrotic tissues.
  • Combination of antibiotics to cover aerobes and anaerobes.

17. Anaerobic Gram positive non-spore forming bacilli.

  • Actinomycescause actinomycosis
  • Bifidobacterium branched, normal flora in GIT.
  • Eubacterium- mouth and bowel normal flora.
  • Rothia- normal flora in mouth. Also in periodontal disease.
  • Lactobacillus-normal flora in vagina
  • Propionibacterium- on skin as normal flora

18. Anaerobic cocci

  • Peptococci and Peptostreptococci present in mouth,gut, female genital tract together with other anaerobes may be responsible for all above mentioned infections.