OBJECTIVES FOR THE
MICROBIOLOGY LABORATORY
The goals for this laboratory course is to provide the students with a basic fundamental knowledge of how microorganisms grow, react with specific types of growth media and their biochemical reactions with media used in identification. Laboratory procedures are used to show students the effects of antimicrobial chemotherapeutic drugs on specific bacteria.
Students will be given unknown organisms to identify, using all the knowledge they have obtained during the semester performing the aforementioned lab exercises.
Microscopy
To show students the correct way to used a microscope when viewing stained specimens of various types of bacteria. To help students become aware of how a microscope works when dealing with its various parts. To be able to see bacterial morphology and arrangement of cells. To become acquainted with the terms like resolution, refractive index, par focal and total magnification.
Gram Stain
This is the most important stain performed in the micro lab. It helps to differentiate Gram positive bacteria from Gram negative bacteria. The student will become aware of the structure of the bacteria’s cell wall and why it will take on a specific stain.
Acid Fast Stain
This stain will show students that not all bacteria can be viewed when stained with the Gram stain. Because of their make up, different types of stain are needed for this microbe to be viewed under the microscope. Some of the species that are AFB positive are disease producers, like tuberculosis and leprosy.
Capsule Stain
This stain is performed to show students that all bacteria are not made up alike. The capsule is found around organisms that are very virulent and this substance is secreted from within the bacterial cell. It helps the bacterium to be able to avoid the host’s immune system for a period of time.
Spore Stain
This stain is performed to show students some bacteria will become dormant when environmental conditions are not suitable. They can see the endospores that are formed or the spore that becomes free from the cell when the environmental become worse.
Culture Transfer Techniques
This exercise is to convey to students they type of equipment that is needed to transfer bacteria from one type media to another. It shows how each is used and which is the most accurate, especially when making dilutions.
Isolation of Pure Cultures
This experiment is performed by students so that they can see what needs to be done to isolate bacteria and produce a pure colony. Pure colonies are needed when bacterial identification is performed. If a colony is not pure when studies are being carried out, your results will have either false positives or false negatives.
Cultural Characteristics
An organisms macroscopic appearance will exhibit differences when grown on different types of culture media. We teach the students how to perform this exercise and what to look for when the culture has grown out.
Temperature Factors
This experiment is set up to demonstrate to students the various temperatures that specific microbes will grow within. The effects of temperature on cellular enzymes and proteins, especially if they become denatured and the organism dies. A comparison will be made between the various bacteria plated out here, to show how bacteria can adapt to all types of environments.
Atmospheric Oxygen Requirements
This exercise is performed to show students the different pathways that a bacterium can use to stay viable. Some organisms are totally in need of oxygen while others are killed by oxygen. This procedure will also show that some bacteria can use more than one pathway when growing in a culture.
Cultivation of Anaerobic Organisms
This exercise is to show students the methods that can be used when cultivating anaerobic organisms.
Determination of Susceptibility to Dental Caries
This test is carried out to show the organisms that are responsible for dental caries. It also shows how to perform the experiment that will demonstrate a host’s susceptibility to caries formation.
Normal Microbial Flora of the Throat & Skin
To identify microorganisms that normally reside in the throat and skin.
Microbiological Analysis of Urine Specimens
This procedure is to help the students to become familiar with the organisms commonly responsible for infections of the genitourinary tract.
It show methods for detection of bacteriuria and identification of microorganisms associated with the urinary tract.
Identification of Human Staphylococcal Pathogens
This exercise is to show students how they can become familiar with the medical importance of staphylococci organisms.
It gives the information needed for the student to perform selected laboratory procedures designed to differentiate among the major staphylococcal species.
Identification of Human Streptococcal Pathogens
This exercise is needed to help students to become familiar with the medical importance of streptococci.
Selected laboratory procedures are designed to differentiate streptococci on the basis of their hemolytic activity and biochemical patterns associated with the Lancefield group classifications.
Streptococcus pneumoniae identification
To become familiar with laboratory procedures to differentiate between Streptococcus pneumoniae and other alpha hemolytic streptococci.
Use of Differential & Selective Media
To become familiar with the use and function of specialized media for selection and differentiation of microorganisms.
Chemical Agents of Control: Chemotherapeutic Agents
To show students that chemotherapeutic agents are chemical substances used in the treatment of infectious diseases. Their mode of action, if they produce a static or cidal effect on microorganisms without producing a like effect in the host cells.
Extracellular Enzymatic Activities of Microorganisms
To determine the ability of microorganisms to excrete hydrolytic extracellular enzymes capable of degrading the polysaccharide starch, the lipid tributyrin and the proteins gelatin and caesin.
Carbohydrate Fermentation
To determine the ability of microorganisms to degrade and ferment carbohydrates with the production of an acid or acid and gas.
Triple Sugar Iron Agar Test
To learn a rapid screening procedure that will differentiate among members of the enterobacteriaceae. To distinguish between the enterobacteriaceae and other groups of intestinal bacilli.
IMViC Tests
To determine the ability of microorganisms to degrade the amino acid tryptophan.
To determine the ability of microorganisms to oxidize glucose with the production and stabilization of high concentrations of acid end products.
To differentiate between all glucose-oxidizing enteric organisms, particularly Escherichia coli & Enterobacter aerogenes.
To differentiate further among enteric organisms such as Klebsiella pneumoniae, E. coli & E. aerogenes by neutral end products.
To differentiate even further among enteric organisms on the basis of their ability to ferment citrate as a sole carbon source.
Hydrogen Sulfide Test
To determine the ability of microorganisms to produce hydrogen sulfide from substrates such as the sulfur-containing amino acids or inorganic sulfur compounds.
Urease Test
To determine the ability of microorganisms to degrade urea by means of the enzyme urease.
Nitrate Reduction Test
To determine the ability of some microorganisms to reduce nitrates to nitrites or beyond the nitrite stage.
Catalase Test
To determine the ability of some microorganisms to degrade hydrogen peroxide by producing the enzyme catalase.
Oxidase Test
To perform an experimental procedure that is designed to distinguish among groups of bacteria on the basis of cytochrome oxidase activity.
Lysine Iron Agar Reactions
To determine the ability of microorganisms to either deaminate or decarboxylate Lysine.
Identification of Enteric Microorganisms Using Multitest Systems
To become familiar with the members of the family Enterobacteriaceae.
To become familiar with laboratory procedures disigned to identify enteric pathogens using commercial multitest microsystems.
Species Identification of Unknown Bacterial Cultures
To identify an unknown bacterial species by the use of keys, selective and differential media, biochemical reactions, present of enzymes and Gram stains for morphology.
Agglutination Reaction: Mono-Test for Infectious Mononucleosis
To show students a commercial test kit for the detection of infectious mononucleosis heterophile antibodies.
Sexually Transmitted Diseases: Rapid Immunodiagnostic Procedures
To show students a commercial test kit for the rapid detection in the screening of syphilis.
Standard Qualitative Analysis of Water
To determine the presence of coliform bacteria in a water sample.
To obtain an index as to the possible number of organisms present in the sample under analysis.
To confirm the presence of coliform bacteria in a water sample for which the presumptive test was positive.
To confirm the presence of coliform bacteria in a water sample, or, if necessary, to confirm a suspicious but doubtful result of the previous test.
Microbiological Analysis of Food Products: Bacterial Count
To determine the total number of microorgnisms present in food products.
To determine the presence of coliform bacteria in the selected food products.