CLASSIFICATION OF BACTERIA

Transcription

1 CLASSIFICATION OF BACTERIA

2 DISCLOSURE Relevant relationships with commercial entities none Potential for conflicts of interest within this presentation none Steps taken to review and mitigate potential bias N/A

3 LEARNING OBJECTIVES This lecture is designed to meet the following end-of-week learning objective: 1. Describe the classification of bacteria

4 MODULE OBJECTIVES By the end of this module, you should be able to: 1. Classify bacteria according to Gram reaction, microscopic morphology and aerobic tolerance

5 RECOMMENDED READING Engleberg et al (eds.) Schaechter s Mechanisms of Microbial Disease (5th Edition), Lippincott Williams & Wilkins Chapters 10

6 BACTERIA - CLASSIFICATION Divided into Gram-positive and Gramnegative Divide by microscopic morphology Divided into aerobic and anaerobic based on whether they can tolerate environments with oxygen

7 BACTERIA - CLASSIFICATION Divided into Gram-positive and Gramnegative Divide by microscopic morphology Divided into aerobic and anaerobic based on whether they can tolerate environments with oxygen

8 Black JG. Microbiology Principles and Explorations 5 th Edition 2002 THE GRAM STAIN

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10 BACTERIAL CELL WALL STRUCTURE Black JG. Microbiology Principles and Explorations 5 th Edition 2002 Slide 10

11 BACTERIAL CLASSIFICATION I Bacteria Gram-Positive Gram-Negative

12 BACTERIA - CLASSIFICATION Divided into Gram-positive and Gramnegative Divide by microscopic morphology Divided into aerobic and anaerobic based on whether they can tolerate environments with oxygen

13 Black JG. Microbiology Principles and Explorations 5 th Edition 2002 BACTERIAL SHAPE

14 Black JG. Microbiology Principles and Explorations 5 th Edition 2002 BACTERIAL SHAPE

15 pairs diplococci chains clusters Black JG. Microbiology Principles and Explorations 5 th Edition 2002

16 BACTERIAL CLASSIFICATION II Bacteria Gram-Positive Gram-Negative Cocci Bacilli Cocci Bacilli

17 CREATING A SMEAR Directly from a specimen (e.g., sputum) From a culture

18 CREATING A SMEAR

19 FIXING THE SMEAR Heat Fix or Methanol Fix

20 GRAM STAINING SMEARS

21 VIEWING SMEARS 1000x Magnification

22 USEFULNESS OF THE GRAM STAIN Devised by Danish microbiologist, Hans Christian Gram in 1884 Remains one of the most useful rapid diagnostic test in modern microbiology labs 1. Provides the basis for empiric antibiotic therapy for bacterial infections 2. May indicate the need for laboratory procedures not routinely used (e.g., fungal culture, anaerobic culture) 3. Helps assess adequacy of a specimen

23 ASSESSING SPECIMEN ADEQUACY Sputum reject (100x)

24 ASSESSING SPECIMEN ADEQUACY Sputum acceptable (100x)

25 ASSESSING SPECIMEN ADEQUACY Sputum acceptable (1000x)

26 BACTERIA - CLASSIFICATION Divided into Gram-positive and Gramnegative Divide by microscopic morphology Divided into aerobic and anaerobic based on whether they can tolerate environments with oxygen

27 BACTERIAL METABOLISM RESPIRATION (aerobic conditions) (net gain 38 ATP) - Glycolysis, Krebs (TCA) Cycle, and membrane based electron transport chain using O 2 as final electron acceptor RESPIRATION (anaerobic conditions) (net gain <38 ATP) - Respiration using substances other than O 2 (e.g., nitrate, sulfate, etc.) as the final electron acceptor FERMENTATION (anaerobic conditions) (net gain 2 ATP) - Glycolysis and cytosol based substrate level phosphorylation (no Krebs cycle or membrane based electron transport chain)

28 AEROBES Strict Aerobes Solely depend on aerobic respiration Facultative Anaerobes Can use aerobic or anaerobic metabolism Microaerophilic Depends on aerobic respiration but killed by O 2 Aerotolerant Uses anaerobic fermentation but can survive in O 2

29 Strict Anaerobes ANAEROBES Use anaerobic metabolism Killed by the presence of oxygen (lacks enzymes that breakdown oxygen free radicals and hydrogen peroxide)

30 High O 2 No O 2 Strict Facultative Micro- Aerotolerant Strict Slide 30 Aerobe Anaerobe aerophile Anaerobe Anaerobe

31 AEROBES ANAEROBES High O 2 No O 2 Strict Facultative Micro- Aerotolerant Strict Slide 31 Aerobe Anaerobe aerophile Anaerobe Anaerobe

32 BACTERIAL CLASSIFICATION III Bacteria Gram-Positive Gram-Negative Cocci Bacilli Cocci Bacilli O 2 AnO 2 O 2 AnO 2 O 2 AnO 2 O 2 AnO 2 O 2 = aerobe, AnO 2 = anaerobe

33 BACTERIA - EXAMPLES O 2 Staphylococcus spp. Listeria spp. Neisseria spp. E. coli Streptococcus spp. Corynebacterium spp. Moraxella spp. P. aeruginosa Enterococcus spp. Bacillus spp. [Haemophilus spp. (coccobacilli)] AnO 2 Peptostrepto- Clostridium spp. Veillonella spp. Bacteroides spp. coccus spp.

34 BACTERIA - EXAMPLES O 2 Staphylococcus spp. Listeria spp. Neisseria spp. E. coli Streptococcus spp. Corynebacterium spp. Moraxella spp. P. aeruginosa Enterococcus spp. Bacillus spp. [Haemophilus spp. (coccobacilli)] AnO 2 Peptostrepto- Clostridium spp. Veillonella spp. Bacteroides spp. coccus spp.

35 ATYPICAL BACTERIA Intracellular Chlamydia spp., Chlamydophila spp., Rickettsia Lack Rigid Cell Wall Mycoplasma spp. Acid-fast*/Partially Acid-fast** Mycobacterium spp.*, Nocardia spp.** Spirochetes Treponema pallidum, Leptospira spp.

36 QUIZ Bacteria can be classified according to what three criteria?

37 QUIZ Bacteria can be classified according to what three criteria? 1. Gram reaction 2. Microscopic morphology 3. Aerobic Tolerance

38 KEY MESSAGES Bacteria are prokaryotic cells that can be classified according to their: 1. Gram reaction Gram-positive vs. Gram-negative 2. Microscopic morphology Cocci (clusters, chains) vs. Bacilli Diplococci 3. Aerobic tolerance Aerobic vs. anaerobic

39 BACTERIA - EXAMPLES O 2 Staphylococcus spp. Listeria spp. Neisseria spp. E. coli Streptococcus spp. Corynebacterium spp. Moraxella spp. P. aeruginosa Enterococcus spp. Bacillus spp. [Haemophilus spp. (coccobacilli)] AnO 2 Peptostrepto- Clostridium spp. Veillonella spp. Bacteroides spp. coccus spp.

40 MODULE OBJECTIVES By now you should be able to: 1. Classify bacteria according to Gram reaction, microscopic morphology and aerobic tolerance