MICROBIOLOGY 101 LABORATORY MANUAL

EXERCISE #20: STAPHYLOCOCCUS & DISEASE TRANSMISSION

NAME, ID #:_______________________________________________.

REVISED: 08/04/99

INTRODUCTION

The staphylococci, often in association with streptococci, produce abscesses, boil, carbuncles, osteomyelitis (infections of the bone) and fatal septicemia's (blood infections). The staphylococci are G+, catalase +, non-spore-forming, facultative anaerobic, large cocci, that tend to grow in grape-like clusters. They are normal inhabitants of the SKIN and the NASAL MEMBRANES of healthy people. Human staphylococci strains tend to be salt tolerant and are able to grow in the presence of NaCl concentrations that inhibit most other bacteria. Important pathogenic strains include Staphylococcus aureus which produces a variety of diseases including food poisoning, impetigo, boils, carbuncles, osteomyelitis (infections of the bone), toxic shock syndrome and fatal septicemia's (blood infections). Approximately 10% of the general public carry this organism. Further, 90% of hospital personnel have been reported to harbor staphylococci and thus are the reservoir for the frequent #nosocomial staph infections. S. aureus, along with Pseudomonas strains, are especially dangerous to burn patients. Staph hospital infections are one of the most dangerous infections you can contract; it is sometimes called the "GOLDEN PLAGUE" because of the yellow color of its colonies. S. aureus is considered one of the most dangerous microbes on earth and thousands of Americans die every year from staph infections they contacted while in the hospital. A major concern is that most hospital staph strains are resistant to most of the antibiotics available. It is perhaps ironic that the first infection treated with an antibiotic (penicillin) was a fatal staph infection and now we have come almost full circle to where staph will soon be resistant to all the antibiotics we have in our arsenal.

In this exercise you will attempt to isolate S. aureus from the upper respiratory system and from the skin.

PURPOSE OF STAPHYLOCOCCUS LABORATORY:

  1. To isolate Staphylococci from the human body.
  2. To become familiar with the characteristics of the Staphylococci.

RELATIONSHIP TO LECTURE MATERIAL

GENERAL INSTRUCTIONS:

  1. Please place all appropriately labeled drawings on the back of the manual so the instructor can identify them.

PROCEDURE:

  1. Read pg. 1, 3, 15-16, 25, 28, 30, 38, 46, 49, 67, 72, & 138 in A Photographic Atlas for the Microbiology Laboratory.
  2. Obtain, per pair, two plates of mannitol salt agar, sterile swabs and a tube of sterile saline.
  3. One of the pair is to dip a swab into the saline and swab the inside of the nose of their partner.
  4. Inoculate a corner of the plate and streak for isolation.
  5. The other member of the pair will dip a swab into the saline and swab their partner's skin (inside of arm) and repeat the plating & streaking procedure.
  6. Incubate both plates at 37oC until the next lab.
  7. At the next lab observe the types of colonies that appear on the plates and note their color and the color of the medium surrounding the colonies.
  8. Choose two or three likely staphylococcus colonies and gram stain them; include the control cultures.
  9. Prepare a table summarizing your observations and conclusions and show it to the instructor.
  10. Click here for a discussion of S. aureus. Click here for a discussion of the clinical aspects of Staph Infections.

SAMPLE QUESTIONS: You should be able to answer these questions at the conclusion of this laboratory.

PURPOSE OF DISEASE TRANSMISSION EXERCISE

  1. To demonstrate how diseases are spread via human contact.
  2. To relate this information to our own lives so we can protect ourselves from infection.

INTRODUCTION

When we get an infectious disease we all wonder "How did I catch that bug and from whom?" This is the first question a professional epidemiologist also asks, only they couch it in terms of the general population: "How did anyone catch that bug and from whom or what?" Knowing how a disease is spread is one of three crucial pieces of information public health officials need to know in order to control the spread of disease. The other two are: "What is the etiological agent responsible for the disease?" and "How can the disease best be treated so as to stop/minimize its further spread or occurrence?"  With these three pieces of information almost all diseases, including those caused by infectious agents, can be limited, if not prevented. If, as is sometimes the case, answers to all three can not be determined, then the first question assumes predominance, for if the "source" of an infection is known immediate steps can usually be taken to limit the further spread of a pathogen. For example, although #John Snow did not know the answer to the last two questions, he was able to stop the London Cholera infection by removing the handle of the Broad Street Pump, from which people were obtaining Cholera-contaminated drinking water.

Typically, when epidemiologists investigate the origin and nature of an epidemic they initially collect detailed information on the victims, and their close associates including, if possible, those currently ill with the disease. This information includes asking questions like: "Where have you been/visited the past few weeks?", "What foods have you eaten lately?", "What animals have you had contact with recently?", "Have you had any insect bites recently?", "Who have you associated with and in what way?" etc. Obtaining useful information requires considerable thought, since the wrong data will delay solving the problem. Large areas (cities, even entire countries) may have to be covered and 1,000s of people questioned using everything from personal interviews to questionnaires. The data then has to be compiled and analyzed to extract the useful information, which is often obscured by the mass of unrelated data or "noise". Often the location of each case is placed on a map to determine if a physical source of the disease can be found. Frequently, no logical pattern emerges and the process must be repeated with a new set of questions or a different approach. During an epidemic, this must be done in an atmosphere of fear and panic, frequently with limited funds and manpower, and all mixed with a serious dose of complicating political and social factors (religion [God's punishment on _______], prejudice [the CIA, homosexuals, hippies etc. spread it], scientific illiteracy [it's the result of a curse, demons] etc.). Tracking HIV infections is a classical case in point; it has everything including SEX, more SEX, prejudice, money, prejudice, religion, prejudice etc. Consider how you would collect such information in remote parts of Africa or South America?

In this laboratory exercise you will simulate the pattern of "DISEASE" transmission. You will gather data on the pattern of the transmission and analyze this data to determine the local likely source of the "INFECTION". You will then discuss this data and related considerations.

MATERIALS

  1. Test tubes of solution, including ONE that contains "Pseudo Ebola", one per student; labeled with a number.
  2. A solution for detecting who has contracted a "PSEUDO EBOLA INFECTION".
  3. Pasteur pipettes, one per student.
  4. Clean test tubes, one per student.

PROCEDURE

  1. Each student chose a numbered test tube containing a solution. Record the number of your solution. The tube will be marked so to indicate the amount of fluid to be transferred. Mark all other tubes at this point. One tube in the class will contain a chemical (the infected tube: PSEUDO EBOLA) whose pattern of transfer will be followed.
  2. Each student will pick ONE other student at random and exchange a quantity of solution indicated by the mark on the tube with him/her. Mix the test tubes thoroughly after the exchange.
  3. Record the name of the person you exchanged solutions with: ROUND: 1; NAME:_________________________.
  4. Only at the Instructor's signal each student will find a DIFFERENT student and exchange solutions as before. ROUND: 2; NAME:____________________________________.
  5. Only at the Instructor's signal repeat an exchange a third time with a DIFFERENT student. ROUND: 3; NAME__________________________________.
  6. Each student then adds the PSEUDO EBOLA detector solution to their test tube, mix thoroughly and record the color as RED or YELLOW.
  7. Record on the board the names of each student and each of their 3 contacts. Circle the ones who are infected (RED).
  8. The Instructor will lead the class in a discussion of the results, during which you will attempt to determine who was the original carrier of the "PSEUDO EBOLA" and the answers to the following questions:

CONCLUSIONS

Record the data from the board and be prepared to discuss it in the class. Use the space below to record the consensus findings. Be sure and record the logic behind this conclusion.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ADDITIONAL INFORMATION ON STAPH AND ITS DISEASES:

http://129.109.136.65/microbook/ch012.htm: This site does an excellent job of covering Staph medically.

Copyright © Dr. R. E. Hurlbert, 1999.
This material may be used for educational purposes only and may not be duplicated for commercial purposes.
SCIENCE HALL, ROOM 440CA
PHONE: 509-335-5108
FAX: 509-335-1907
E-mail address: hurlbert@wsu.edu or hurlbert@pullman.com 

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