Bacterial clasification

Transcription

1 Bacterial clasification Describe bacterial classification: List taxon levels Define taxonomy and identification Describe principles of taxonomy Explain classification of bacteria

2 Taxonomy the science of classification, especially of living organisms, to facilitate research and communication. Organisms are arranged into taxonomic categories or taxa (singular: taxon), to show degrees of similarities between organisms.

3 The three phylogenetic lineages of cells (Domains according to comparative rrna sequences) Bacteria Archae Eukarya

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5 Bacteria :Prokaryotic Archae :Prokaryotic Eukarya :Eucaryotic

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9 Criteria that drive taxonomy Genomic analysis has become the final determinant of taxonomy demonstration of phenotypic features remains the primary means of applying these classifications in diagnostic microbiology.

10 Based on certain shared genotypic and phenotypic characteristics bacteria are classified into: Family Genus Species Strain

11 Genus (plural genera) refers to a group of bacterial organisms that share in common several structural, biochemical and physiological traits Species refers to a subgroup of organisms within a genus that share more specific traits among themselves. The term strain refers to a pure culture made up of descendants of a single isolation

12 Introduction to bacteriology Bacterial classification: Phenotypic Analytic Genotypic

13 Bacterial classification is based on several major properties Gram staining (and other stains) Morphology Metabolic behavior Infection patterns Intracellular vs extracellular Antigenic composition DNA sequence

14 Bacteria Relatively simple Prokaryotic Cell wall: gram-negative or positive

15 Bacteria Preliminary classification: size (1-20 micrometer) shape(sphere,rod,spiral) arrangement (single cell, chain, cluster)

16 Phenotypic classification I First characteristics used to identify bacteria Morphology(shape) Macroscopic appearence of colonies Microscopic shape of the individual organism

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23 Natural classification scheme that reflects major differences in cell wall structure and to some extent the mechanisms involved in disease. Gram positive (blue): single membrane consisting of a thick peptidoglycan layer no lipopolysaccharide

24 Gram negative (pink): inner and outer membranes, with outer membrane having lipopolysaccharide molecules

25 Property discovered by Christian Gram 1883, a Danish botanist, while attempting to differentiate bacteria from human tissue by different staining methods. He noted differences in stain retention by bacteria..

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28 The ultrastructure of Escherichia coli (E. coli) as an example of a prokaryote

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31 The general size of a prokaryotic cell is about 1-2 um. Note the absence of membrane bound organelles There is no true nucleus with a nuclear membrane The ribosome's are smaller than eukaryotic cells The slime capsule is used as a means of attachment to a surface Only flagellate bacteria have the flagellum Plasmids are very small circular pieces of DNA that maybe transferred from one bacteria to another.

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34 Gram positive cocci in clusters Gram positive cocci in chains

35 Gram negative cocci Gram negative rods

36 Morphology Rods or cocci Curved or spiral Filamentous

37 Some correlation between morphology and disease Spiral bacteria---treponemes, Borrelias, Leptospiras, Spirillium tend to cause systemic diseases

38 Pathogenic filamentous bacteria Actinomyces, Nocardia, Mycobacteria tend to cause chronic diseases Gram positive bacteria, Staphylococcus more likely to cause skin infections, Streptococci skin and pneumonia

39 Phenotypic classification Most common methods Biochemical markers İdentification of a clinically significant isolate Subdividing beyond the species level epidemiology Biotyping

40 Metabolic properties may influence ability type of disease caused but not the only factor Aerobe versus anaerobe (microaerophilic, facultative aerobes) Anaerobes have a greater propensity to cause abscesses Brain, lung, liver, intra-abdominal abscesses

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43 Biochemical reactions are used to classify

44 Phenotypic classification Other methods Serotyping (inert on biochemical testing, difficult to grow, etc) Analysis of antibiogram patterns Phage typing

45 Analytic classification II Genus, species, subspecies level Chromatographic pattern of cell walll mycolic acids for mycobacteria Analysis of lipids in the entire cell for many bacteria and yeasts Analysis of the whole cell protein and cellular enzymes Labor intensive and expensive

46 Genotypic classification III The most precise method for classification Ratio of guanine to cytosine DNA hybridization Molecular probes Relationship among bacterial isolates Detection of microrganisms directly in clinical specimens Rapid identification of microorganisms, esp. slow growing.. Nucleic acid sequence analysis Amplification and sequence analysis Sequences of ribosomal RNA highly conserved İdentification Defining evolutionary relationship Complete sequencing of the entire genome

47 Genotypic classification Other genotypic methods Plasmid analysis Ribotyping Analysis of chromosomal DNA sequences

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49 Sequencing

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54 Aerobic, Gram-Positive cocci Catalase-Positive cocci Micrococcus Staphylococcus Stomatococcus Catalase-Negative cocci Aerococcus Alloiococcus Enterococcus Lactococcus Leuconostoc Pediococcus Streptococcus

55 Aerobic, Gram-Positive Bacilli Actinomycetes with Cell Wall Mycolic Acids Corynebacteriaceae Corynebacterium Nocardiaceae Gordona Nocardia Rhodococcus Tsukamurella Mycobacteriaceae Mycobacterium

56 Aerobic, Gram-Positive Bacilli (II) Actinomycetes with No Cell Wall Mycolic Acids Actinomadura Dermatophilus Nocardiopsis Oerskovia Rothia Streptomyces Thermophilic actinomycetes Saccharomonospora Saccharopolyspora Thermoactinomyces Tropheryma

57 Miscellaneosus Gram-Positive Bacilli Arcanobacterium Bacillus Brevibacterium Erysipelotrix Gardnerella Listeria Turicella

58 Aerobic, Gram-Negative cocci, Coccobacilli, and Bacilli Cocci and Coccobacilli Branhamella Moraxella Neisseria Bacilli Enterobacteriaceae Citrobacter Enterobacter Escherichia Klebsiella Morganella Proteus Salmonella Serratia Shigella Yersinia

59 Aerobic, Gram-Negative cocci, Coccobacilli, and Bacilli (II) Bacilli Vibrionaceae Vibrio Aeromonodaceae Aeromonas Pleisomonodaceae Pleisomonas Campylobacteriaceae Arcobacter Campylobacter Helicobacteriaceae Helicobacter Bacilli Pseudomonadaceae Pseudomonas Pasteurellaceae Actinobacillus Haemophilus Pasteurella

60 Aerobic, Gram-Negative cocci, Coccobacilli, and Bacilli (III) Miscellaneous genera Acinetobacter Bartonella Bordetella Brucella Burkholderia Capnocytophaga Cardiobacterium Eikenella Francisella Kingella Legionella Spirillum Stenotrophomonas Streptobacillus

61 Anaerobic, Gram-Positive and Gram- Negative Bacteria Gram-Positive cocci Peptostreptococcus Gram-Negative cocci Veilonella Gram-Positive bacilli Actinomyces Bifidobacterium Clostridium Eubacterium Lactobacillus Propionibacterium Mobiluncus Gram-Negative bacilli Bacteroides Fusobacterium Porphyromonas Prevotela

62 Miscelaneous, Medically Important Bacteria Mycoplasmataceae Mycoplasma Ureaplasma Spirochaetaceae Borrelia Treponema Leptospiraceae Leptospira Chlamydiaceae Chlamydia Chlamydophila Other bacteria Coxiella Ehrlichia Orientia Rickettsia

63 How does an experienced physician approach bacterial diseases? Organ system approach Which bacteria cause disease in a certain location Gram stain approach What does the gram stain show--used to treat empirically before cultures are completed Requires that one is able to get a gram stain which is not always the case

64 Organ system approach Meningitis Pneumococci, Meningococci, Hemophilus influenzae, Listeria Sinusitis Pneumococci, H. influenzae, Moraxella Acute otitis media Pneumococci, H. influenzae, Moraxella Pharyngitis Group A streptococci These are all aerobic bacteria

65 Now add in the Gram stain Gram negative rods seen in CSF in meningitis H. influenzae Gram positive cocci in meningitis Pneumococcus Gram positive cocci in sinusitis Pneumococcus or Staphylococcus Gram stain may suggest the organism --clusters or diplococci?

66 Pneumonia Pneumococcus, H. influenzae Pleural cavity Pneumococcus, Staphylococcus Endocarditis Streptococcus, Staphylococcus, Enterococci

67 Pneumonia-sputum gram stain Gram positive diplococci as predominant organism Pneumococcus--the most common gram positive cocci found in pneumonia Therapy Endocarditis-blood culture positive Gram positive cocci on the stain Maybe Streptococci, Enterococci, or Staphylococci Treatment decision made on this basis- Vancomycin +