wk 15- microbiology

• Medical Microbiology


  The study of microscopic organisms, such as bacteria, fungi, and protists, as well as viruses. It encompasses all aspects of these microorganisms such as their behaviour, evolution, ecology, biochemistry, and physiology, along with the pathology of diseases that they cause.
• Medical Microbiology


  • Provides evidence of:
  • Describing the key disciplines in biomedical science
  • Assessing the usefulness of a range of laboratory techniques and their application in biomedical science
  • Analysing the professional aspects of working as a biomedical scientist and career pathways that can be taken
  • Legislation/policies/regulations relating to health and safety at work and your responsibilities
• Microbiology


  The study of microscopic organisms, such as bacteria, fungi, and protists. It also includes the study of viruses, which are not technically classified as living organisms but do contain genetic material.
• Microbiology roles in routine NHS labs

  • Bacteriology - the study of bacteria

  Mycology - the study of fungi

  Parasitology - the study of parasites

  Virology - the study of viruses

  Serology - the diagnostic examination of blood serum

  Molecular Microbiology - diagnosis of microbial infection using molecular techniques
• Bacteriology - the holy trinity

  Microscopy

  Culture

  Sensitivity
• Microscopy


  • Uses microscopes (light, inverted, phase contrast, mercury bulb, blue light LED)

  Typically requires a magnification of 400x to 1000x to properly view bacteria
• Gram Stain


  The most widely used stain in microbiology, discovered by the Danish scientist and physician Hans Christian Joachim Gram in 1884. It involves heat fixing a sample on a microscope slide, applying a primary stain (crystal violet), a mordant (iodine/Lugol's iodine), decolourisation (ethanol/acetone), and a counter-stain (safranin/carbol fuchsin).
• Other applications of stains

  • Auramine Phenol stain for Mycobacteria

  Ziehl-Neelsen stain for Mycobacteria and Cryptosporidium

  Acid/Base stain for white cell differentiation

  Indian Ink for yeasts, especially Cryptococcus

  Wet preparation for cell count, Trichomonas and Candida
• Culture


  Pathological samples received into the laboratory are processed as per Standard Operating Procedure, cultured onto appropriate solid/liquid culture media, and after incubation, culture plates are interpreted to determine whether a pathogen is present.
• Culture Media Types


  • Simple media (e.g. Nutrient Agar)

  Complex media (e.g. Blood Agar)

  Enriched media (e.g. Chocolate Agar)

  Selective media (e.g. XLD)

  Differential media (e.g. CLED)

  Transport medium (e.g. VTM)
• Plate Streaking


  • Plate streaking method
• Mixed Cultures


  • Mixed culture picture
• Sensitivity (Antimicrobial susceptibility testing)


  It is important to undertake antimicrobial susceptibility testing on potential pathogens to determine what antibiotics the organism is sensitive or resistant to, in order to ensure effective treatment.
• Susceptibility Testing Methods


  • Broth Dilution

  Antibiotic Gradient

  Disc Diffusion Test

  Dilution method and MIC determination
• BSAC and EUCAST


  British Society for Antimicrobial Susceptibility and European Committee on Antimicrobial Susceptibility Testing - provide standards for antibiotic susceptibility testing
• Susceptibility Testing Methods


  • Clindamycin E test

  Vancomycin E test
• Identification


  In addition to susceptibility testing, many organisms have to be identified through a variety of manual or automated systems which look at the organisms' biochemical profile, or using MALDI-ToF to identify their proteomic signature. Identification can be used to aid diagnosis and treatment or can be important for epidemiological study.
• Antigen/Antibody Tests


  • Urinary Legionella Antigen

  Urinary Streptococcus pneumoniae Antigen

  Helicobacter pylori Faecal Antigen

  Clostridium difficile GDH

  Clostridium difficile toxin

  Faecal rotavirus antigen

  Respiratory Syncytial Virus antigen

  Salmonella, Shigella, Vibrio antigen agglutination
• Mycology


  Culture of pathological samples specifically for the isolation and identification of yeasts and fungi.
• Parasitology


  Usually performed in the enterics department. Faecal samples are centrifuged and treated to remove vegetable matter and fats, filtered, and the deposit is observed using light microscopy to identify ova and cysts of parasites.
• Virology/Serology


  Viral culture now largely superseded, especially in routine diagnostic labs. Serology looks for the presence of viral antibodies or antigens in serum samples using enzyme Immunoassay, which is largely an automated process.
• Viral/Antibody Tests


  • HIV antibody/antigen

  Hepatitis B Virus (antibody, antigen, core antibody)

  Hepatitis C antibody

  Hepatitis A antibody

  Rubella antibody

  Toxoplasma antibody

  Mycoplasma antibody

  Syphilis antibody

  CMV antibody

  VZ antibody
• Molecular Microbiology


  Often carried out in the Virology/Serology department, utilising PCR to look for the presence of viral/bacterial target genetic material. Can determine the presence/absence as well as quantifying the amount of virus present in the sample.
• The activity tab of the NOW room contains practice exam questions, activities on culture media and microscopy. The resources tab points to further reading on related topics/journal articles and includes a blank PowerPoint presentation of the material covered.