Microbiology
Technologies + Future Outlook
Microbiology
• Since we have started to harness the amazing
power of bacteria, the field of microbiology has
become much more prominent
• As we previously learned, we are developing new
ways to utilize bacteria to our advantage!
– Detergents
– Mining
– Textiles
– Food
In the clinical lab
• Most bacterial cultures are processed much like we did in
this lab
– Swab “infected” areas
– Culture bacteria on growth media
– Observe colonies
– Perform culture tests*
– Oxidase, indole*
– Perform gram staining procedure
– Identify organism
– Perform Antibiotic susceptibility testing
Microbiology Technologies
•However, a clinical lab has access to
more $$, and are designed to be
more microbiology specific than our
lab.
•These are some of the interesting
technologies used in clinical labs
around the world today!
Automated Laboratories
Culturing Bacteria
• Clinical labs now have access to a wide variety of Chromogenic
Media
– The chromogenic mixture contains chromogenic
substrates as Salmon-GAL, X-Gal, X-glucuronide, etc.
– Certain enzymes, produced by some bacteria, cleave
these substrates, resulting in the different coloration of
certain bacteria colonies.
Bacterial Identification
• Chromogenic Agar
• Automated Identification systems
– E.g. the Vitek system (bioMerieux)
– Bacterial cultures are inserted into cards with a
variety of different compounds, which when
metabolized, will let the user know exactly what
organism you are dealing with
Bacterial Identification
• MALDI-TOF system
– Matrix Assisted Laser dissociated/ionized – Time of
Flight
– Essentially, a machine which zaps bacteria with a laser,
causing all the proteins and cellular components of that
bacteria to travel up a tube.
– Mass spectrometer – complex machine which measures
the mass of particles, and tells exactly what the bacteria
is, in a matter of 2 minutes
– Typically takes 4-5 days to confirm positive results
Antibiotic Susceptibility Testing
• First let’s look at a few key terms
– Antibiotic
– An antimicrobial agent, used to combat bacterial
infections
– Antiseptic
– Antimicrobial agent applied to the surface of living
tissue
– Disinfectant
– Antimicrobial agent that is applied to non-living
surfaces for sterilization
Antibiotic Susceptibility Testing
• Bacteriocidal
–Kills bacteria
• Bacteriostatic
–Stops bacteria from replicating, long
enough so host immune system can fight
off infection
Antibiotic Susceptibility Testing
• Automated Systems
– The Vitek system , which we previously learned
about can be used to give an antibacterial
susceptibility background to a wide variety of
organisms
• Diffusion Systems
– Etests
– Kirby Bauer Disk Diffusion tests
Etests
• A strip of specialized
paper, containing different
concentrations of a specific
antibiotic.
• Where the bacteria stops
growing tells the doctor
what dose of antibiotic to
give that patient (MIC –
minimum inhibitory
concentration)
Kirby Bauer Disk Diffusion Test
• Works by placing
antibiotic disk on a
cultured agar plate, and
measuring the “zone of
inhibition” size
• Tells whether the
bacteria is sensitive or
resistant to the
antibiotic, depending on
the zone size
So why is the study of microbiology
important?
• By now, hopefully we realize the
importance of bacteria in our everyday
lives… good or bad.
• With a greater understanding of
microbiology, more career opportunities
open up into this exploration as well!
Careers in Microbiology
• Clinical Physician
– Immunologist
– Microbiologist
– Pathologist
• Laboratory Technician
• Food & Drink
– Any major food company hires microbiologists
– Same with any brewing company as well…
– Wine microbiology
• Industry
– Green movement in the 21st Century has opened the door to many microbial
practices
– Biomining, bioremediation, biofuels
To Do Now
• Use Kirby Bauer Disc diffusion sheet in front of you, to
determine “your bacterias” zone of inhibition sizes to different
types of antibiotics
– Which antibiotic would you use to combat this infection?
• NB. This is the hypothetical activity to replace the actual
antibiotic test… it is possible these agents do not work against
the organism you have found.
– You must find your organism by deducing your Gram stain
results + colony descriptions
– Subsequently, determine which antibiotics are effective
against that organism
When you have finished
• Continue to work on your Lab assignment, or continue review of
Chapter 24.