Lecture 2 Introduction to Microbiology

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Lecture 2 Introduction to Microbiology

• Lecture aims
• To provide an introduction to the study of
  microbiology
• To introduce some basic terms
• To provide a little history
• refer Black Chpt 1pges 1-25,Chpt 3 pgs 49-69
  Chpt4 pgs72-106

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The Nature of Microbiology

• Microbiology has a wide range of applications
• We will focus on
• The kind of microbes
• How they are related to disease
• Infection control

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Why Bother with Microbiology?Lets leave it to
the Path lab to deal with!
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Perhaps the following case study will assist us
in our decision as to the relevance of
microbiology to the practicing health
professional

• You're the registered nurse in an intensive care
  unit (ICU) with 3
• febrile patients and 1 developing a wound
  infection
• Relevant (immediate) patient histories
• Patient No. 1 adult female following abdominal
  surgery
• Patient No. 2 adult male from oncology following
  chemoX
• Patient No. 3 child with community acquired
  pneumonia
• Patient No. 4 adult male develops lower limb
  surgical wound infection
• A new intern asks what will I do
  microbiologically, nurse?
• Can you assist her?... if you can't, you need to
  do some
• microbiology

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Possible short answers to case studies

• Patient 1 with abdominal surgery Take blood
  cultures and
• empirically X with amoxyl, gentamicin and
  metronidizole.
• Patient 2 take blood cultures depending how
  seriously ill, treat
• with as above or if life threatening,
  consider imipenem /-
• vancomycin.
• Patient 3 take sputum sample and blood cultures
  and treat
• empirically with cefotaxime.
• Patient 4 take swabs of wound for microbiology
  analysis,
• consider blood cultures. If wound is below
  knee consider empirical
• treatment with flucloxacillin amoxil
  keep in mind possibility of
• MRSA and therefore vancomycin.
• Rationale The 67421 microbiology course

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Microbiology defined

• The study of organisms, where the individual
  cells of the
• 'microbe' can't be seen by the unaided
  human eye'
• That is, we need to use specialized detection
  systems-usually
• optical instruments termed microscopes.
• There are 2 main type main types of microscopes
  in use
• Bright field microscope resolution about 0.2µm
• Electron microscope resolution about 100 times
  greater

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The microbial world2 divisions Procaryotes
Eucaryotes

• Procaryotes
• No nucleus
• Generally circular DNA genome
• /- cell wall
• Can have extrasomal DNA
• DNA without introns
• Haploid
• Binary division

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• Eucaryotes
• Have nucleus
• Other membrane organelles
• Diploid chromosomes
• Mitotic meiotic division
• Have introns and exons

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In clinical microbiology we have interest in both

• Bacteria (procaryotic)
• Eg Staph sp, Strep sp, E.coli, Mycoplasma sp
• Fungi (eucaryotic)
• Candida sp (single celled yeast), Aspergillus sp
  (multicelled)
• Parasites (eucaryotic)
• Giardia lamblia, Plasmodium sp (malaria)
• Viruses
• HIV, HBV, HBC, Rubella, Herpes (EBV, VZ, HSV)

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Microbial classification

• Two components
• Nomenclature (Taxonomy)
• Use as many characteristics as possible to
  separate Kingdoms, Families, Genera and Species
• Rapid identification (clinical use)
• Use as few definitive characteristics to define
  the agent to assist appropriate intervention

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Example of a diagnostic key

• Unknown bacteria 'X'
• Gram stain ( /-)
• Shape (eg cocci, rods, coccobacilli) c
• Configuration (chains, clusters,
  diplo) clusters
• Catalase(/-)
• Coagulase (/ -)
• Antibiotic sensitivity (eg Methicillin S/R)
  R
• Identification Multi Resistant Staphylococcus
  aureus (MRSA)

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A little History

• Main events people (refer table 1.3 pge 21 in
  text)
• Before about 1650 philosophers believed in
  SPONTANEOUS
• GENERATION
• Significant discoveries altered this thinking.

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Some of the key players were

• ANTON van LEEUWENHOEK
• Mid 17th Century probably 1st to observe bacteria
  under
• magnification
• Although Robert Hooke first to observe microbes
  through magnification)- Its thought he saw
  protozoa ie larger cells such as amoebae)

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• LOUIS PASTEUR
• Demonstrated by the use of sterile media that
  microbes were in fact
• present in air,
• And that air in does not create microbes
• Used broths in flasks and S funneled microbial
  traps experiments

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• Ignaz SEMMELWEIS
• Discovered that the death rate of neonates in
  labour wards staffed
• by trainee doctors was 10-20 higher than in
  hospitals training only
• midwives
• Joseph LISTER
• adopted the use of 'aseptic' techniques which
  lead to its general adoption)

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• ROBERT KOCH
• Proved beyond doubt that specific organisms were
  the cause of specific infectious diseases.
• Experiments with the very lethal disease
  (especially of cattle)
• anthrax

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• KOCHS POSTULATES
• 1. The same 'pathogen' must be present in every
  case of the
• disease
• 2. The pathogen must be isolated from the
  diseased host and
• grown in pure culture
• 3. The pathogen when inoculated into a
  susceptible uninfected
• host causes the disease
• 4. The pathogen must be reisolated in pure
  culture from the
• inoculated animal

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