Micro

• Biological Safety Cabinet

  Enclosed workspace designed to provide protection from exposure to infectious agents
• Classes of Biosafety Cabinet

  • Class I
  • Class II
  • Class IIA
  • Class IIB
• 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
  • Direct the flow of contaminated air into the filters
  • Also called as VERTICAL LAMINAR FLOW BSCs
• Class IIA Biosafety Cabinet

  • Self-contained, and 70% of the air is recirculated [most common in clinical microbiology section]
• Class IIB Biosafety Cabinet

  • Selected for radioisotopes, toxic chemicals or carcinogenic samples
• Bacteria

  Prokaryotic unicellular organisms that lack a true nucleus and nuclear membrane
• Bacteria

  • Single, closed, circular chromosomes of double-stranded DNA called NUCLEOID
  • PLASMIDS: small circular molecules o extrachromosomal circular DNA
  • May either be GRAM POSITIVE [violet] or GRAM NEGATIVE [pink or reddish pink]
  • BINARY FISSION: asexual reproduction of bacteria
  • Bacteria size: range from 0.2 to 2um in diameter and 1 to 6um in length
• Gram Stain

  • Principal stain used for microscopic examination of bacteria
  • First devised by Hans Christian Gram during the late 19th century
  • Divide most bacterial species into two large groups: Gram-positive (take up the basic dye, crystal violet) and Gram-negative (allow crystal violet dye to wash out easily with decolorizer alcohol or acetone)

  
• 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
• Specimen Collection

  • Universal Precaution are followed throughout the collection and handling process
  • Persons collecting or handling specimens should wear gloves and a laboratory gown
  • Eye protection should be worn if splashing
  • Accidents or injuries (needle prick) must be reported immediately
• General Guidelines for Specimen Collection

  • 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! ASEPTIC TECHNIQUE is required
  • Specimen container should LABELED with patient's identification, the date and time of collection and the source of specimen
• Collection of Specimens from Various Body Sites

  • THROAT (SWABS): Tongue should be depressed before swabbing between the tonsillar pillars and behind the uvula
  • SPUTUM: Expectorated specimens from deep cough should be collected into a sterile specimen cup
  • STOOL: Should never be taken from the toilet and should not be contaminated with urine
  • URINE: Midstream clean-catch is the most common collection method
  • BLOOD: 2-3 cultures should be collected at random times during 24-hour period, skin is disinfected with 70% alcohol, followed by Iodine
  • CEREBROSPINAL FLUID: Should be collected aseptically by PHYSICIAN, should be processed immediately and not exposed to heat or refrigeration
  • GENITAL TRACT: MEN (penile discharge) - Exudates may be expressed from the urethral orifice or a small-diameter swab inserted 3-4 cm into the urethra, WOMEN (vaginal discharge) - A sterile swab is inserted into the cervix with an aid of speculum
• Handling and Transport of Specimens

  • Anaerobic specimens must be transported in an anaerobic system, Aerobic set-up is okay to be exposed in oxygen, Anaerobic should not be exposed to oxygen
  • Swab samples are not allowed to dry out
  • Most specimen can be held at 2°C to 8°C [refrigerator temperature] if transport cannot occur immediately EXCEPT temperature-sensitive organisms, blood culture bottles, and CSF
• Types of Culture Media

  • Nutritive Media: Support the growth of a wide range of microorganisms
  • Differential Media: Microorganisms that can be distinguished on the basis if 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
  • Backup Broth: Also called supplemental or enrichment broth, for detection of small numbers of organisms present
  • Specialized Media: Used when specific organisms are suspected
• Incubation

  • 35°C-37°C: Normal incubation temperature for bacterial cultures
  • Anaerobic jars, 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

  • 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
• Gram staining negative color


  Reddish pink red or pink
• Aerobic respiration 


  Yes to O sugar-atp
• Anaerobic respiration 


  Ekis to O fermentation