microbiology introduction 2
DESCRIPTION
This is a series of lectures on microbiology useful for undergraduate medical and paramedical studentsTRANSCRIPT
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MicrobiologyClass II
Dr. Ashish Jawarkar
Consultant Pathologist
Parul Sevashram hospital
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Microbiology and the Role of the Medical Assistant Microbiology – study of microorganisms
(simple forms of life visible only with a microscope)
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Medical assistant Assists physician Obtains specimens Prepares specimens for direct examination Prepares specimens for transportation to
reference laboratory If office has a POL, performs microbiologic
procedures
Microbiology and the Role of the Medical Assistant (cont.)
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How Microorganisms Cause Disease Cause disease in variety of ways
Use nutrients needed by cells and tissues Damage cells directly Produce toxins
May remain localized or become systemic Transmission
Direct contact Indirect contact
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How Microorganisms Cause Disease (cont.)
Localized symptoms Swelling Pain Warmth Redness
Generalized symptoms Fever Tiredness Aches Weakness
Normal flora Provides a barrier Can cause an infection
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Apply Your Knowledge
1. What role does the medical assistant play in relation to microbiology?
ANSWER: The medical assistant may assist the physician in obtaining specimens, obtain specimens herself, prepare specimens for direct examination or transport to a reference laboratory, and possibly perform microbiologic procedures.
2. How do microorganisms cause disease?
ANSWER: Organisms cause disease by using nutrients needed by cells and tissues, damaging cells directly, or producing toxins.
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Classification of Microorganisms Structure
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Classification of Microorganisms Classification by structure
Subcellular – DNA or RNA surrounded by a protein coat – viruses
Prokaryotic – simple cell structure with no nucleus or organelles – bacteria
Eukaryotic – complex cell structure with nucleus and specialized organelles – protozoans, fungi, parasites
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Protozoans – single celled eukaryotes Fungi – multicelled eukaryotes with cell wall Parasites – multicelled eukaryotes without
cell wall
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Naming of microorganisms
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Standardized naming Genus
Category of biologic classification Example – Staphylococcus
Species of organism Represents a distinct type of microorganisms Examples – Staphylococcus aureus and
Staphylococcus epidermidis
Naming of Microorganisms (cont.)
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Apply Your Knowledge
Describe the classifications of microorganisms and give an example of each.
ANSWER: Microorganisms are classified as:Subcellular organisms that have DNA or RNA surrounded by a protein coat – virusesProkaryotic organisms have a simple cell structure with no nucleus or organelles – bacteria Eukaryotic have a complex cell structure with nucleus and specialized organelles – protozoans, fungi, parasites
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Viruses Smallest known
infectious agents Subcellular
microorganism Have only nucleic acid
surrounded by a protein coat
Must live and grow in living cells of other organisms
Hepatitis virus
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Viruses (cont.) Illnesses caused by viruses
Colds Influenza Croup Hepatitis Warts
Vaccines are available for many viruses
AIDS Mumps Rubella Measles Herpes
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Bacteria Single-celled prokaryotic organisms Reproduce rapidly Classification
Shape Ability to retain dyes Ability to grow
with / without air Bacillus bacterial classification
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Bacteria: Classification and Identification
Shape Coccus – spherical, round, or ovoid
Bacillus – rod-shaped
Spirillum – spiral-shaped
Virbrio – comma-shaped Spirillum bacterial classification
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Bacteria: Classification and Identification
Shape
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Ability to retain certain dyes Gram’s stain (Gram +ve, Gram –ve) Acid-fast stain (AFB+ve, AFB –ve)
Ability to grow in presence or absence of air Aerobes – grow best in the presence of oxygen Anaerobes – grow best in the absence of oxygen
Bacteria: Classification and Identification (cont.)
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Special groups Mycobacteria – bacilli
with a cell wall that differs from most bacteria
Rickettsiae Very small Live and grow within
other living organisms such as mites and ticks
Chlamydiae Cell wall structure
differs from other bacteria
Live and grow within other living cells
Mycoplasmas – completely lack the rigid cell wall
Bacteria: Classification and Identification (cont.)
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Protozoans
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Protozoans Single-celled eukaryotic organisms, larger than
bacteria
Found in soil and water
Illnesses Malaria Amebic dysentery Trichomoniasis vaginitis
Leading cause of death in developing countries
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Fungi Eukaryotic organisms with
rigid cell wall Yeasts
Single-celled Reproduce by budding
Molds Large, fuzzy, multicelled
organisms Produce spores
Superficial infections Athlete’s foot Ringworm Thrush
Can cause systemic infections
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Multicellular Parasites Organisms that live on or in another organism and
use it for nourishment
Parasitic worms Usually due to poor
sanitation Roundworms Flatworms Tapeworms
Parasitic insects Bite or burrow under
the skin Mosquitoes Ticks Lice mites
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Apply Your Knowledge
Matching:
___ Yeast or mold A. Virus
___ Tapeworm / lice B. Bacteria
___ Classified by shape C. Protozoan
___ Subcellular organism D. Fungus
___ May be aerobic or anaerobic E. Multicellular parasite
___ Smallest known organism
___ Found in soil and water
E
ANSWER:
D
A
B
B
C
A
Very Good
!
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How Infections Are Diagnosed
Steps to diagnosis and treatment1. Examine the patient
Presumptive diagnosis May or may not need additional tests
2. Obtain specimen(s) Label properly Include presumptive diagnosis
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How Infections Are Diagnosed (cont.)
3. Examine specimen directly Wet mount Smear
4. Culture specimen Culture medium – contains nutrients Examine culture visually and microscopically
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How Infections Are Diagnosed (cont.)
5. Determine sensitivity to antibiotics
6. Treat the patient as ordered Antimicrobial – to kill
pathogen or suppress its growth
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Apply Your Knowledge
What is the process for diagnosing an infection?
ANSWER: There are six steps for diagnosis and treatment of an infection:
1. Examine the patient 4. Culture the specimen
2. Obtain specimen(s) 5. Determine sensitivity
3. Examine specimen directly 6. Treat patient / appropriate antimicrobial
Super!
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Specimen Collection
Must be collected correctly If not, may not grow in
culture
Contaminants may be mistakenly identified
Patient may receive incorrect or harmful therapy
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Specimen Collection (cont.)
Devices Use appropriate collection
device or specimen container Sterile swabs – absorbent
material on the tip
Collection and transporting systems Sterile, self-contained Transport medium Aerobic or anaerobic
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Specimen Collection: Guidelines
Avoid causing harm, discomfort, or undue embarrassment
Collect from appropriate site
Obtain specimen at correct time
Use appropriate devices
Obtain sufficient quantity of specimen
Obtain specimen prior to the start of antimicrobial therapy
Label correctly
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Specimen Collection (cont.)
Throat culture specimens Swab back of throat in the area
of the tonsils Avoid touching any structures
in the mouth Prepare culture plate or
prepare correctly for transport to laboratory
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Specimen Collection (cont.)
Urine specimen Clean-catch
midstream to minimize contaminants
Process within 60 minutes or refrigerate
Sputum specimen Specimen from
lungs Avoid
contaminating specimen with saliva
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Specimen Collection (cont.)
Wound specimen Swab wound or
lesion Do not touch
outside of wound
Stool Specimens Technique varies
Bacterial infection Protozoal or
parasitic infection
Instruct patient in correct collection procedure
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Apply Your Knowledge
What are the general guidelines for specimen collection?
ANSWER: They are to avoid causing harm, discomfort, or undue embarrassment; collect from appropriate site; obtain specimen at correct time; use appropriate collection devices; obtain sufficient quantity of specimen; obtain specimen prior to the start of antimicrobial therapy; and label specimen correctly.
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Transporting Specimens to an Outside Laboratory Many offices send cultures to an outside lab
Three main objectives Follow proper collection
procedures and proper collection device
Prevent deterioration of specimen
Protect anyone handling specimen
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Direct Examination of Specimens Enables physician to initiate treatment immediately
Wet mounts NaCl mixed with
specimen of glass slide Presence of pathogen
and movement of microorganism
Potassium hydroxide (KOH) mounts Used if a fungal
infection of the skin, nails, or hair is suspected
KOH dissolves keratin that can mask presence of a fungus
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Preparation and Examination of Stained Specimens Quick, tentative
diagnosis Differentiation
between types of infections
Gram’s stain Moderate-
complexity test Bacteria either
retain or lose purple color Gram-positive
bacteria Gram-negative
bacteria
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Apply Your Knowledge
1. What are the methods for preparing a slide for direct examination by the physician?
ANSWER: They are wet mount and KOH mount.
2. How does the examination of stained specimens facilitate patient care?
ANSWER: Stained specimens enable the physician to provide a quick, tentative diagnosis and differentiate between types of infections.
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Culturing Specimens Inoculating a culture plate
Transfer some of the specimen onto a culture plate
Label the plate correctly Qualitative analysis – determination of type of
pathogen Quantitative analysis – number of bacteria
present in sample
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Culturing Specimens (cont.)
Incubating culture plates 35 to 37º C for 24 to 78 hours Agar side up
Interpreting cultures Requires skill and practice Characteristics of colonies Relative number Changes to media around colonies
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Culturing Specimens (cont.)
Culture media Liquid, semisolid, or
solid forms Contains agar Selective or nonselective
Special culture units Rapid urine culture – Uricult Also available for throat, vaginal, and blood
specimens
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Apply Your Knowledge
3. What is the process for culturing a specimen?
ANSWER: The culture medium is inoculated with the specimen and placed in an incubator to promote growth of the organism on the culture medium.
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Determining Antimicrobial Sensitivity
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Determining Antimicrobial Sensitivity An outside lab
reports Sensitive – no
growth Intermediate – little
growth Resistant –
overgrown
Procedure Filter paper containing
antimicrobial agents placed on inoculated agar plate
Incubated for 24 hours Evaluate effectiveness
of agent
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Apply Your Knowledge
1. What is the difference between selective and nonselective culture media?
ANSWER: Selective culture media allows the growth of only certain kinds of bacteria. Unselective culture media support the growth of most organisms.
2. The office received a culture sensitivity report on a bacteria that said it was resistant to an antimicrobial. What does this mean?
ANSWER: It means that the bacteria was not killed by the antimicrobial and that there was an overgrowth of the bacteria.
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In summary Types of microorganisms Nomenclature Structure Specimen collection Techniques Antibiotic resistance
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Thank You