Ways to Identify Unknown Microbe Staph & Strep PDF

WAYS TO IDENTIFY AN UNKNOWN MICROBE: STAPH & STREP PROJECT WAYS TO IDENTIFY A MICROBE OR INFECTION  Signs & Symptoms  Epidemiology  Media  Staining  SOMETIMES YOU CAN DIAGNOSE FROM SIGNS AND SYMPTOMS: Signs: objective, measurable, Symptoms: subjective, feeling or sensation obse...

WAYS TO IDENTIFY AN UNKNOWN MICROBE: STAPH & STREP PROJECT WAYS TO IDENTIFY A MICROBE OR INFECTION  Signs & Symptoms  Epidemiology  Media  Staining  SOMETIMES YOU CAN DIAGNOSE FROM SIGNS AND SYMPTOMS: Signs: objective, measurable, Symptoms: subjective, feeling or sensation observable characteristic, e.g. fever, rash a person has, e.g. pain, fatigue  PATIENT’S HISTORY OR PUBLIC HEALTH INFORMATION  Patient’s age, job, medical history, vaccination status, etc.  Current outbreaks in the area?  Risk factors specific to the location and/or patient’s background? CULTURE MEDIA  Main Purpose:  Provide the nutrients and environment needed for microbial growth.  Maybe there is more we can do with media too…  SOLID, LIQUID & SEMI-SOLID REVIEW MEDIA  Solid:  Liquid:  Agar is added as a solidifying  Growth is identified as ingredient turbidity  Colonies can grow on the surface  Colonies are not present  Bacteria could grow on the surface  Bacteria grows in the liquid and/or be stabbed down into the agar GENERAL-PURPOSE MEDIA  Contains a mix of nutrients  Designed to grow a broad range of microbes  Examples:  Nutrient Broth/Agar  Trypticase Soy Broth/Agar ENRICHED MEDIA  Has additional complex organic substances added (blood, serum, growth factors, etc.)  Required for growing fastidious microbes  Examples:  Blood Agar  Chocolate Agar SELECTIVE MEDIA  Contains something to inhibit the growth of some microbes  “Selects” for the growth of certain ones  Helps to isolate a certain microbe from a mixed culture SELECTIVE MEDIA EXAMPLES  mStaph Broth has a high  Sabouraud’s Agar has a low salt concentration so only pH of 5.6 which inhibits halotolerant microbes bacterial growth and selects can grow in it for fungus DIFFERENTIAL MEDIA  Allows several types of microbes to growth but shows a visible difference between microbes  Differentiates between microbes that are growing  Helps to identify microbes  DIFFERENTIAL MEDIA EXAMPLES  Urea broth has a pH indicator  Chromagar has a group of and those that have the dyes in it that turn bacterial enzyme urease to breakdown colonies specific colors to the urea, turn the broth identify the urinary pathogen bright pink BLOOD AGAR IS BOTH ENRICHED & DIFFERENTIAL Beta  Enriched with Blood so many fastidious microbes can grow  Some microbes hemolyze and we can differentiate  Alpha hemolysis: incomplete lysis (brownish green halos around growth)  Beta hemolysis: complete lysis (clear halos around growth)  Gamma hemolysis: no lysis Alpha Gamma or (growth doesn’t affect the blood) Non-hemolytic SOME MEDIA IS BOTH SELECTIVE & DIFFERENTIAL  Mannitol Salt Agar:  Has a high salt concentration = Selective  Only halotolerant microbes can grow on MSA  Has mannitol & pH indicator = Differential  Mannitol fermenters turn the media yellow  Those that don’t ferment mannitol leave the media pink  DIFFERENTIAL STAINING (USE 2 DYES TO DIFFERENTIATE BETWEEN CELL TYPES OR PARTS)  Basic Steps:  Make a head fixed smear  Primary Stain  Mordant  Decolorizer  Secondary or Counterstain Bacterial Cell Shapes: Coccus / Cocci Bacillus / Bacilli Vibrio Spirillum Spirochete Bacterial Arrangements: Single Diplo Strepto Tetrad Sarcina Staphylo  GRAM STAIN (A DIFFERENTIAL STAIN)  Start with a heat-fixed smear  Steps:  Primary stain = Crystal Violet  Mordant = Iodine  Decolorizer = Ethanol  Counterstain = Safranin  Interpretation:  Purple = Gram Positive  Pink = Gram Negative  A DICHOTOMOUS KEY OF MORPHOLOGY (SHAPE) AND Gram CELL ARRANGEMENT: Reaction Gram - Gram + Cocci Bacilli Cocci Bacilli Single Cocci Diplobacilli Single Bacilli Streptobacilli Diplococci Single Bacilli Staphylococci Streptococci  ENDOSPORE STAIN (A DIFFERENTIAL STAIN)  Start with a heat-fixed smear  Steps:  Primary stain = Malachite Green  Mordant = Steam  Decolorizer = Water  Counterstain = Safranin  Interpretation:  Green = Endospores  Pink = Vegetative Cells  ACID FAST STAIN (A DIFFERENTIAL STAIN)  Start with a heat-fixed smear  Steps:  Primary Stain = Carbol fuchsin  Mordant = Steam  Decolorizer = Acid Alcohol  Counter Stain = Methylene Blue  Interpretation:  Pink/Purple = Acid Fast Cells  Blue = Non Acid Fast Cells EXAMPLE ORGANISM: Escherichia coli Simple Stain Negative Stain Gram Stain Endospore Acid Fast Stain Stain EXAMPLE ORGANISM: Bacillus subtilis Simple Stain Negative Stain Gram Stain Endospore Acid Fast Stain Stain  STAPH & STREP PROJECT  Work in small groups of 3-4  Read the Staph and Strep Project Info  See Ex. 36 & 37 in Lab Manual  Refer to Module 6 on Staph & Strep