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• Microbiology


  Divided into bacteriology, virology, mycology, parasitology (most usually included in microscopy section)

  
• Bacteria is the most common microorganism to be tested under the microbiology section
• Tertiary laboratory


  Performs microbiology procedures
• Class I biosafety cabinet


  • Allows room air to pass into cabinet and around the area and material within, sterilizing only the air to be exhausted
  • Consist of negative pressure
  • Operated in open front
• Class II biosafety cabinet


  • Air flows in "sheets", which serves as a barrier to particle from outside the cabinet
  • Directs the flow of contaminated air into the filters
  • Also called as VERTICAL LAMINAR FLOW BSCs
• Types of Class II safety cabinet


  • Class IIA – self-contained, and 70% of the air is recirculated
  • Class IIB – selected for radioisotopes, toxic chemicals, or carcinogenic samples
• Prokaryotic unicellular organisms


  Lack a true nucleus and nuclear membrane
• Nucleoid


  Single, closed, circular chromosomes of double stranded DNA
• Plasmids


  Small circular molecules of extrachromosomal circular DNA (for serological and antibody testing and classifying bacteria)

  
• Bacterial classification


  • Gram positive
  • Gram negative

  
• Binary Fission


  Asexual reproduction of bacteria
• Bacteria size


  Range from 0.2 to 2µm in diameter and 1 to 6µm in length
• Gram Stain


  • Principal stain used for microscopic examination of bacteria
  • First devised by Hans Christian Gram during the late 19th century
  • Helpful enough to narrow down what type of antibiotics can be used and to identify the morphology of the bacteria

  
• Gram staining results


  • Gram positive – take up the basic dye, crystal purple or violet
  • Gram negative – allow crystal violet dye to wash out easily with decolorizer alcohol or acetone; safranin; red or pink
• Differences between Gram positive and Gram negative

  • Cell wall: Thick (Peptidoglycan) vs Thin (Peptidoglycan)
  • Lipopolysaccharide: Absence vs Presence
  • Gram Staining: Purple vs Red or Pink
  • Representation: Purple or Violet result vs Pink result
• Four basic morphological types of bacteria


  • Cocci – spherical-shaped cells
  • Bacilli – rod-shaped cells
  • Spirilla – spiral-shaped cells
  • Vibrios – comma-shaped cells

  
• Two types of bacterial metabolism


  • Fermentation – Process by which bacteria catabolize carbohydrates to produce energy
  • Respiration – also known as oxidation, Process of bacterial energy generation rather than fermentation, Found usually in blood
• Universal Precautions


  Followed throughout the collection and handling process
• Aseptic Technique


  Required for specimen collection
• Specimen collection guidelines


  • Specimen should be from the infection site and not contaminated by the surrounding area
  • Specimen should be collected before antimicrobials are administered (Antibiotics)
  • Appropriate collection devices and containers should be used and must be STERILE!
  • Specimen container should LABELED with patient's identification, the date and time of collection and the source of specimen
• Specimen collection from various body sites


  • Throat (Swabs)
  • Sputum
  • Stool
  • Urine
  • Blood
  • Cerebrospinal fluid
  • Genital Tract
• Specimen transport guidelines


  • Anaerobic specimens must be transported in an anaerobic system (deep tissues)
  • Swab samples are not allowed to dry out (fluid transport medium)
  • Most specimen can be held at 2°C to 8°C if transport cannot occur immediately except: Temperature-sensitive organisms, Blood culture bottles [incubator at 37°C], CSF (Cerebrospinal fluid) [incubator at 37°C]
• Microbiology tests


  • Gram stain – first requested by the physician because it provides immediate results for microbiology; 20 to 30 minutes
  • Culture and sensitivity – second requested by the physician; attempting to grow microorganisms from the specimen; 12 hours to 24-48 hours

  
• Classifications of Culture Media


  • Nutritive Media – Support the growth of a wide range of microorganisms and are considered nonselective
  • Differential Media – Microorganisms that can be distinguished on the basis of certain growth characteristics evident on the medium
  • Selective Media – Support the growth of one group of organisms, but not another, by adding antimicrobials, dyes, or alcohol to a particular medium
  • Backup Broth – Also called supplemental or enrichment broth, For detection of small numbers of organisms present, Growth for specific type of organism
  • Specialized Media – Used when specific organisms are suspected
• Incubation


  • 35°C to 37°C: Normal incubation temperature for bacterial cultures
  • Anaerobic jars (candle jar), bags, or an anaerobic chamber are appropriate for incubation of anaerobic cultures
  • 42°C to 45°C: for stool cultures for detection of Campylobacter jejuni
• Specimen Rejection Criteria for Microbiology


  • Specimen received in nonsterile or contaminated containers
  • Specimen contaminated with barium or other foreign substances
  • 24-hour urine or sputum collections
  • Saliva instead of sputum
  • Unrefrigerated urine specimens 2 hours or more post-collection
• Immunology


  Study of immune system (prevents the establishment if infection in the body)
• Serology


  • Study of antigen-antibody reactions
  • Study of non-cellular component of the blood called SERUM
• Samples used in serological test


  • Serum – most commonly used
  • CSF
  • Urine
  • Stool
• When to use serology


  • Unable to culture infectious agent
  • Confirmation of etiologic ID of the specimens
  • Diagnosis of immunologically-related disorders
  • Determine immune status - Vaccination
• Antigen


  • Also known as FOREIGN SUBSTANCES
  • Stimulate the immune system [once it has entered the body]
  • Substances that induce or elicit an immune response
  • Substances that induce or elicit the production of antibodies
• Antibodies


  • Also knowns as IMMUNOGLOBULINS
  • One of the major substances produced by the immune system that will block harmful antigen
  • Find a specific antigen, bind to it, and then destroy it
  • Functions: Cell toxicity [destroy infectious agent], Neutralization, Opsonization
• Serology


  When unable to culture infectious agent, confirmation of etiologic ID of specimens, diagnosis of immunologically-related disorders, determine immune status
• Culture


  Attempt to grow organisms
• It is possible that there are organisms that take too long to culture or because it is dangerous to grow, it would be unable to culture for the safety of the workers
• Antigen


  Also known as FOREIGN SUBSTANCES, substances that induce or elicit an immune response, substances that induce or elicit the production of antibodies
• Antibodies


  Also known as IMMUNOGLOBULINS, one of the major substances produced by the immune system that will block harmful antigen, functions include cell toxicity, neutralization, opsonization
• Agglutination


  • Antigens involved are particulate, clumping of reactants in serological test
• Precipitation


  • Antigens involved are soluble antigens, liquid form or formation of sediments in the mixture
• VDRL


  Venereal Disease Research Laboratory Test, only use for screening for syphilis, uses heated serum, principle is flocculation