Anaerobic Bacteriology Lecture

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Anaerobic Bacteriology Lecture

  1. 1. ANAEROBIC BACTERIOLOGY Dr. Ma. Ellery M. Mendez FPAMS , FPAAM, DPSMAP
  2. 2. <ul><li>Anaerobes generate energy by fermentation </li></ul><ul><li>Lack the capacity to utilize O2 as a terminal hydrogen acceptor </li></ul><ul><li>Some are sensitive to O2 concentration as low as 0.5% O2 </li></ul><ul><li>Most can survive in 3%-5% O2 </li></ul><ul><li>A few can grow poorly in the presence of air  aerotolerant anaerobes </li></ul><ul><li>Many are members of the normal flora </li></ul><ul><li> created by presence of facultative </li></ul><ul><li>anaerobes </li></ul>
  3. 3. FACTORS THAT INHIBIT THE GROWTH OF ANAEROBES BY OXYGEN <ul><li>1. Toxic compounds are produced </li></ul><ul><li>e.g. H2O2 , Superoxides </li></ul><ul><li>2. Absence of catalase & Superoxide </li></ul><ul><li>dismutase </li></ul><ul><li>3. Oxidation of essential sulfhydyl groups in enzymes without sufficient reducing power to regenerate them </li></ul>
  4. 4. FACTORS RESPONSIBLE FOR THEIR VIRULENCE <ul><li>1. Lipopolysaccharide </li></ul><ul><li>- promotes abscess formation, enhanced coagulation </li></ul><ul><li>2. Polysaccharide capsule </li></ul><ul><li>- correlated with abscess production </li></ul><ul><li>3. Enzymes </li></ul><ul><li>a. Collagenase </li></ul><ul><li>b. Heparinase </li></ul><ul><li>* develop thrombophlebitis & septic emboli </li></ul><ul><li>4. Short chained fatty acids </li></ul><ul><li>a. Butyrate- seen in dental plaque </li></ul><ul><li>b. succinic acid – reduces phagocytic killing </li></ul>
  5. 5. Multiplication of the opportunistic pathogens is facilitated by: <ul><li>1. inhibition of phagocytosis & intracellular killing </li></ul><ul><li>by PMN in the presence of Bacteroides by: </li></ul><ul><li>a. competition of opsonins </li></ul><ul><li>b. inhibition by capsular materials </li></ul><ul><li>2. protection of antibiotic susceptibility strains in </li></ul><ul><li>mixtures thru destruction by the ß-lactamases </li></ul><ul><li>3. utilization of O2 by facultative species that aids in </li></ul><ul><li>producing a suitable environment for growth of </li></ul><ul><li>anaerobe </li></ul>
  6. 6. Anaerobic Bacteria of Medical Interest MORPHOLOGY GRAM STAIN GENUS Sporeforming (+) Clostridium Non-sporeforming bacilli (+) (-) Actinomycetes, Bifidobacterium,Eubacte-rium,Propionibacerium, Mobilncus,Lactobacillus Bacteroides,Fusobacterium Prevotella,Porphyromonas Non-sporefoming cocci (+) (-) Peptococcus, Pepto-streptococcus Streptococcus Veilonella
  7. 7. CLINICAL MANIFESTATION <ul><li>Clinical hints </li></ul><ul><li>1. odor </li></ul><ul><li>2. tissue </li></ul><ul><li>3. location </li></ul><ul><li>4. necrotic tissue </li></ul><ul><li>5. endocarditis with (-) blood culture </li></ul><ul><li>6. infection associated with malignancy </li></ul><ul><li>7. black discoloration </li></ul><ul><li>8. blood containing exudates </li></ul><ul><li>9. associated with sulfur granules </li></ul><ul><li>10. Bacteremic feature with jaundice </li></ul><ul><li>11. human bites </li></ul>
  8. 8. Sites and Infection produced by Anaerobes
  9. 10. LABORATORY DIAGNOSIS <ul><li>A. COLLECTION </li></ul><ul><li>Anaerobes are endogenous in nature </li></ul><ul><li>I. Appropriate specimens for anaerobic </li></ul><ul><li>culture : </li></ul><ul><li>1. pus </li></ul><ul><li>2. pleural fluid </li></ul><ul><li>3. urine </li></ul><ul><li>4. pulmonary secretions </li></ul><ul><li>5. uterine secretions or sinus tract material </li></ul>
  10. 11. <ul><li>II. Collection by needle aspiration is preferrable than swab culture because of </li></ul><ul><li>a. better survival of pathogen </li></ul><ul><li>b. greater quantity of specimen </li></ul><ul><li>c. less contamination with extraneous </li></ul><ul><li>organism are often achieved </li></ul>
  11. 12. B. HANDLING <ul><li>If a swab must be used, a 2 tube system </li></ul><ul><li>must be used </li></ul><ul><li> 1 st tube contains swab in O2 free CO2 </li></ul><ul><li> 2 nd tube contains PRAS (pre-reduced </li></ul><ul><li>anaerobically steilized culture media) </li></ul><ul><li>Specimen should be placed in anaerobic transport device with gas mixture </li></ul>
  12. 13. C. Isolation <ul><li>Gram stain should be done in the </li></ul><ul><li>laboratory : </li></ul><ul><li>a. choice of appropriate media & </li></ul><ul><li>methods for culture </li></ul><ul><li>b. quality control for the types of </li></ul><ul><li>bacteria that laboratory culture </li></ul><ul><li>reveal </li></ul>
  13. 14. A solid or liquid medium maybe used & must provide an anaerobic environment  Anaerobic Culture System <ul><li>ANAEROBIC JAR </li></ul><ul><li>1. Candle Jar </li></ul><ul><li>- reduces O2 environment </li></ul><ul><li>- only ↑ CO2 tension </li></ul><ul><li>2. Gas Pak Jar </li></ul><ul><li>a. Palladium aluminum coated pellets </li></ul><ul><li>- catalyst </li></ul><ul><li>- chemically reduces O2 </li></ul><ul><li>- reacts with residual O2 in the presence of H2 to form </li></ul><ul><li>H2O </li></ul>
  14. 15. <ul><li>b. Gas Pak envelope </li></ul><ul><li>- generates CO2 & H2 gases </li></ul><ul><li>c. Methylene blue strip </li></ul><ul><li>- indicator </li></ul><ul><li>blue -> (+) O2 </li></ul><ul><li>white -> (-) O2 </li></ul><ul><li>II. Anaerobic Glove Chamber </li></ul><ul><li>- close system </li></ul><ul><li>- used for premature babies </li></ul><ul><li>- e.g. incubator </li></ul><ul><li>III. Roll Tube </li></ul><ul><li>- has a pedal  gas ( CO2 & H2 ) would come out </li></ul><ul><li>- place test tube directly to the outlet </li></ul>
  15. 16. D. IDENTIFICATION <ul><li>Plates are checked at </li></ul><ul><li>> 18-24 hours for faster growing species like </li></ul><ul><li>Cl. Perfringens & B.fragilis & daily thereafter up to </li></ul><ul><li>> 5-7 days for slowly growing species like </li></ul><ul><li>Actinomyces, Eubacterium & propionibacterium </li></ul><ul><li>Genus is determined by </li></ul><ul><li>- gram stain, cellular morphology, Gas-liquid </li></ul><ul><li>chromotography </li></ul><ul><li>Species determination is based on fermentation of sugars & other biochemical determination </li></ul>
  16. 17. TREATMENT <ul><li>- Susceptibility testing should be done </li></ul><ul><li>- surgical drainage & resection of necrotic tissue </li></ul><ul><li>- most are resistant to aminoglycosides </li></ul><ul><li>- for Bacteroides gr oup, if resistant to Penicillin & Cephalosporin, they may use: </li></ul><ul><li>a. Clindamycin </li></ul><ul><li>b. Metronidazole </li></ul><ul><li>c. Chloramphenicol </li></ul>
  17. 18. <ul><li>THE END </li></ul>

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