Colony Morphology and Differential Media in Clinical Microbiology
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Questions and Answers

Which group of bacteria is known for having a high G + C content in their DNA?

  • Firmicutes (correct)
  • Actinobacteria
  • Chlamydiae
  • Cyanobacteria
  • Which bacterium is thermophilic and is often used in molecular biology for its heat-resistant DNA polymerase?

  • Streptomyces griseus
  • Thermus aquaticus (correct)
  • Bacillus cereus
  • Mycobacterium tuberculosis
  • Which bacterial phylum includes species capable of photosynthesis and oxygenic photosynthesis?

  • Cyanobacteria (correct)
  • Chloroflexi
  • Chlorobi
  • Planctomycetes
  • Which bacteria are known for their ability to form endospores, making them highly resistant to harsh conditions?

    <p>Clostridium perfringens</p> Signup and view all the answers

    What makes the 16S rRNA gene a good target for bacterial identification/classification?

    <p>It is universal in all bacteria</p> Signup and view all the answers

    What allows for 'universal' amplification of the 16S rRNA gene target?

    <p>Conserved regions flanking variable regions</p> Signup and view all the answers

    How is bacterial identification accomplished in the lab using the 16S rRNA gene?

    <p>Extract DNA and run gel electrophoresis</p> Signup and view all the answers

    Which method uses proteins and carbohydrates as markers to distinguish bacterial strains?

    <p>Serological typing</p> Signup and view all the answers

    What method involves analyzing DNA structure and sequences to distinguish between bacterial strains?

    <p>Molecular typing</p> Signup and view all the answers

    Which method distinguishes bacterial species and strains by their growth patterns, flagella, capsule, and cell wall characteristics?

    <p>Biochemical typing</p> Signup and view all the answers

    What method can still be useful in labs lacking genomic testing equipment?

    <p>Phage typing</p> Signup and view all the answers

    Which gene analysis is used for bacterial identification in clinical microbiology?

    <p>$16S$ rRNA gene analysis</p> Signup and view all the answers

    What can be sequenced to identify an organism's taxonomic group and calculate relatedness between groups?

    <p>$16S$ rRNA gene</p> Signup and view all the answers

    Which method is commonly used for identifying prokaryotes and determining their position on the evolutionary tree of life?

    <p>16S rRNA sequence analysis</p> Signup and view all the answers

    What is the main aim of whole genome sequence comparison in prokaryotic classification?

    <p>To create a high-resolution microbial tree of life</p> Signup and view all the answers

    Which resource is a comprehensive classification of all known species based on genetic relatedness?

    <p>Bergey’s Manual of Systematic Bacteriology</p> Signup and view all the answers

    What are the phenotypic methods for prokaryotic identification mentioned in the text?

    <p>16S rDNA sequence analysis and whole genome sequence alignment</p> Signup and view all the answers

    What plays a crucial role in diagnosing infections and starting appropriate treatment?

    <p>Microscopic morphology</p> Signup and view all the answers

    What are E. coli strains Sakai (O157:H7) and CFT073 known for?

    <p>Causing severe intestinal disease and urinary tract infections, respectively.</p> Signup and view all the answers

    What involves comparing nucleotide sequences and using cutoffs for genus and species identification?

    <p>16S rDNA sequence analysis</p> Signup and view all the answers

    What is taxonomy primarily concerned with?

    <p>Creating hierarchical systems to classify and identify organisms</p> Signup and view all the answers

    Why is classifying prokaryotes challenging?

    <p>Due to their lack of sexual reproduction and morphological similarity</p> Signup and view all the answers

    What provides more accurate insights into evolutionary relatedness compared to phenotypic traits?

    <p>DNA sequencing</p> Signup and view all the answers

    What does the Three Domain System include?

    <p>Bacteria, Archaea, and Eucarya</p> Signup and view all the answers

    What complicates DNA comparisons and highlights the obstacle in classifying prokaryotes?

    <p>Horizontal gene transfer</p> Signup and view all the answers

    What are the levels of categorization underneath species in prokaryote taxonomy?

    <p>Strains</p> Signup and view all the answers

    What were historical prokaryote classifications heavily reliant on?

    <p>Phenotypic traits</p> Signup and view all the answers

    What is the study of evolutionary relationships between organisms known as?

    <p>Phylogeny</p> Signup and view all the answers

    What does taxonomy encompass?

    <p>Classification, nomenclature, and identification</p> Signup and view all the answers

    Which system replaced the five-kingdom system for classifying prokaryotes?

    <p>Three Domain System</p> Signup and view all the answers

    What are informal groupings like 'Kingdoms' not used for in prokaryote classification?

    <p>Bacteria/archaea</p> Signup and view all the answers

    What aids in identifying organisms based on their color at specific temperatures?

    <p>Colony morphology</p> Signup and view all the answers

    Which method allows rapid identification of prokaryotes via biochemical tests?

    <p>Commercial kits like API test strips and Enterotube II</p> Signup and view all the answers

    Which test is used to differentiate prokaryotic species based on the type and quantities of fatty acids in their membranes?

    <p>Fatty acid analysis (FAME)</p> Signup and view all the answers

    Which method allows detection of small numbers of organisms from body fluids, soil, food, and water, including those that cannot be cultured?

    <p>Nucleic acid amplification tests (NAATs)</p> Signup and view all the answers

    What is used to locate nucleotide sequences characteristic of a species or group, with limitations in detecting single possible species/strain?

    <p>Nucleic acid probes, like fluorescence in situ hybridization (FISH)</p> Signup and view all the answers

    What uses fluorescent DNA probes to bind to specific sequences found in S. aureus and 'coagulase negative' staphylococci, enabling rapid assay directly on patient samples in 20 minutes?

    <p>ADVANDX QUICKFISH®</p> Signup and view all the answers

    What technique allows for the detection of specific nucleotide sequences and overcomes the limitations of culture-based methods?

    <p>Nucleic acid probes and NAATs</p> Signup and view all the answers

    What is assessed through biochemical tests such as the catalase test and sugar fermentation?

    <p>Metabolic capabilities</p> Signup and view all the answers

    What provides certainty of identification for organisms such as Streptococcus pyogenes and E. coli?

    <p>Differential media and biochemical tests</p> Signup and view all the answers

    What is used to differentiate prokaryotic species based on the type and quantities of fatty acids in their membranes?

    <p>Fatty acid analysis (FAME)</p> Signup and view all the answers

    Study Notes

    Identifying Prokaryotes in Clinical Microbiology

    • Colony morphology aids in identifying organisms, e.g., Streptococci are fairly small, Serratia marcescens colonies are often red at 22°C, and Pseudomonas aeruginosa often produces green pigment.
    • Differential media and biochemical tests provide certainty of identification, e.g., Streptococcus pyogenes yields B-hemolytic colonies on blood agar and E. coli ferments lactose, forming pink colonies on MacConkey agar.
    • Metabolic capabilities are assessed through biochemical tests, such as the catalase test and sugar fermentation, often relying on color changes and pH indicators.
    • Commercial kits like API test strips and Enterotube II allow rapid identification of prokaryotes via biochemical tests, making the process less labor-intensive and more consistent.
    • Basic strategy for identifying prokaryotes relies on dichotomous keys, with tests like Gram stain, catalase, and oxidase aiding in the identification process.
    • Serology involves using antisera from immunized animals to diagnose and identify pathogens, as proteins and polysaccharides of prokaryotic cells serve as identifying markers.
    • Fatty acid analysis (FAME) is used to differentiate prokaryotic species based on the type and quantities of fatty acids in their membranes, with gas chromatography used for measurement.
    • Nucleic acid amplification tests (NAATs), like polymerase chain reaction (PCR), allow detection of small numbers of organisms from body fluids, soil, food, and water, including those that cannot be cultured.
    • Nucleic acid probes, like fluorescence in situ hybridization (FISH), locate nucleotide sequences characteristic of a species or group, with limitations in detecting single possible species/strain.
    • ADVANDX QUICKFISH® uses fluorescent DNA probes to bind to specific sequences found in S. aureus and "coagulase negative" staphylococci, enabling rapid assay directly on patient samples in 20 minutes.
    • Nucleic acid probes can bind to denatured, single-stranded DNA of an unknown organism, and if they do not bind, the unknown organism is not the targeted species, showing the principle of the technique.
    • The use of nucleic acid probes and NAATs allows for the detection of specific nucleotide sequences, overcoming the limitations of culture-based methods and enabling the identification of non-culturable organisms.

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    Description

    Test your knowledge of colony morphology and differential media used in clinical microbiology for identifying different organisms based on their culture characteristics. This quiz covers identifying common bacteria based on colony size, color, odor, and media reactions.

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