Staphylococcus Lab Report

This experiment was conducted to find the genus and species of an unknown bacteria prescribed by the lab teacher, which was unknown bacteria GA3 in my case. Identification of unknown bacteria techniques are used on an every day basis to figure out what type of bacteria it is and to find the best method of how to treat a patient with this bacteria (1). All five “I’s” of Microbiology were used in the testing for the unknown culture. Inoculation was used several times to put the unknown culture into agar plates or into biochemical test tubes. After Inoculation of these tubes or plates, they always were placed into the incubator for further growth and development. Isolation was used to make sure we got the correct bacteria we were testing for. After each further isolation, we gram stained the culture and inspected the culture under a microscope to further help in the identification process of the unknown bacteria. Multiple tests were done on the unknown culture to make sure we were confident in what kind of bacteria the unknown was.

When determining which bacteria I wanted to use for this experiment I had to decide on E.coli bacteria which is gram negative and staphylococcus a gram positive bacterium. These were chosen because they are safe enough to grow in a college laboratory and were supplied by the technician. Gram negative bacteria has an outer membrane making it more resistant to antiseptics and antibiotics, it also makes it more fatal to the human host it is inhabiting. Whereas gram

Unknown #462. Multiple tests were performed as described in Brown’s1 manual to identify the unknown; it was determined that the unknown was Staphylococcus epidermidis. The incubation temperature of each test was 37˚C and they were incubated for 24-48 hours. The morphological test performed on the unknown #462 were all consistent with the expected results for this bacterial species such cell shape, motility, and gram stain. The bacterium was gram positive was confirmed by growth on PEA plate, inhibition of growth on EMB plate, and through gram staining. The optimal growth temperature was at 37˚C which corresponds to the optimal temperature mesophilic bacterium as stated in StrainInfo2.

In the world of microbiology it is vitally important to be able to discern the identities of microorganisms. Not only is it important in a lab setting but as well as in healthcare in general. Properly identify what strain of bacteria a person has will aid in the proper medicine and dose given. Throughout the semester we have learned about different types of bacteria and certain test that can clearly identify them. The purpose of this lab report is to identify a Gram-positive or Gram-negative bacterium. Using all the knowledge of procedures and lab techniques identify the unknown and discuss all the tests you performed.

MSA agar is selective and differential medium which was used to see if the bacteria fermented mannitol or not. Selective because it selects for gram positive bacteria specifically Staph. species and it has 7.59% NaCl which means the bacteria must tolerate high concentrations of salt to grow and differential because it has a mannitol phenol red pH indicator. After running most of the test, I was able to conclude that my gram positive unknown is either Staphylococcus aureus or Staphylococcus epidermis. To differentiate between the two MSA agar was used because Staphylococcus aureus ferments mannitol and should have growth because it is a gram positive bacteria but Staphylococcus epidermis does not ferment mannitol but can have growth on the agar. So, using aseptic technique, I split the plate in half and inoculated my 2 unknowns onto MSA plate, then incubated at 37 for 24 hours. I knew my unknown A would not grow because it is a gram negative bacteria but it was inoculated as a control to make sure the test is running properly. When I came the next day, the gram-positive bacteria of my plate had growth and the color changed from red to yellow indicating that the bacteria fermented mannitol, which produced acid lowering the pH of the medium. Gram-positive bacteria had yellow color growth and it was surrounded by a yellow halo and gram-negative bacteria did not have any growth and the agar was still red in

For this experiment, I utilized unknown number three which I later identified as Staphylococcus epidermis. I concluded that the unknown organism was Staphylococcus epidermis based on numerous tests performed in the laboratory which I will discuss in detail throughout this paper. One of the first tests performed was the Gram Stain. The Gram Stain

The purpose of this project was to identify the identities of two unknown bacteria in a mixed broth culture by using several separation methods. To separate the organisms, a four-way streak plate technique was used to isolate the two unknown bacteria into separate visible colonies. Then after each colony were clearly isolated; the two unknowns were processed through Gram staining test to determine the Gram stain and morphology. After Gram staining, a carbohydrate test was performed on each unknown to determine if it had glucose, sucrose, or lactose fermentation. The results of the sugar test help determining which biochemical test should be performed next. The Gram positive organism was tested through a carbohydrate fermentation test, then further tested to confirm its identity through an indole and catalase test. The Gram negative organism was tested through carbohydrate fermentation test, then further tested to confirmed its identity through an indole, and TSIA test. After running four biochemical tests, the results conclude that the Gram positive unknown was Staphylococcus aureus. S. aureus was identified based on the fermentation results of the glucose test, negative indole test, and a positive catalase production. S. aureus is a Gram positive circular shaped bacterium that is very common in the U.S and is normally found in the nose, respiratory tract, and on the skin. This bacterium is usually the most common cause of infections after injury or surgery.

The purpose of this experiment was to isolate and identify an unknown Staphylococcus species based on its morphological and biochemical profile (Alachi, 2006). The Staphylococcus genus consists of Gram-Positive bacteria, arranged in grape-like clusters. These species are common residents of the skin and mucous membranes of humans and animals. Majority of Staphylococci are catalase-positive, oxidase negative, aerobic and facultatively anaerobic, and non-motile. They are considered opportunistic pathogens and cause roughly 80% of suppurative skin diseases (e.g., boils). Many Staphylococci

Conclusion: The first two tests performed required that I streak the liquid culture onto a TSA plate in order to isolate individual colonies. The second involved performing a successful gram stain, which resulted in gram positive staphylococci. After successfully performing these tests I was able to narrow down

Staphylococcus aureus is a cluster bacterium that can be found on the skin of around 25% of healthy adults. This bacterium is growing everyday all over the world and many people have no idea they are even carriers. “Staphylococcus aureus is present in the nose of adults (temporarily in 60% and permanently in 20 to 30%) and sometimes on the skin” (Levison). This bacterium has the ability to cause skin infection and sometimes may lead to severe life threatening diseases. There are several different strains of staphylococcus and depending on the severity of the infection is how a health care provider decides the treatment most efficient. Impetigo is more common in children, but adults still have the chance of getting this skin condition. Toxic Shock Syndrome is also associated with S. aureus and is found in at least 50% of the cases to date. S. aureus can display a variety of symptoms and all vary with the disease at hand. Symptoms can range from a boil on the skin or in the nose to skin rashes. More severe symptoms can be carbuncles and infection of the blood (sepsis).Staphylococcus aureus is an ugly bacterium; that can lead to several diseases, such as Toxic Shock Syndrome and Impetigo. S. aureus has multiple symptoms and is treated with a variety of antibiotics.

Chemical methods of control: Antimicrobial drugs, involves the use of chemicals to prevent and treat infectious diseases. Pasteur and others observed that infecting an animal with Pseudomonas aeruginosa protected the animal against Bacillus anthracis. Later, the word “antibiosis” (against life) for this inhibition and called the inhibiting substance “Antibiotic”. As researchers found out more and more about these chemicals they were able to discover that antibiotics are chemicals or natural substances such as bacteria, fungi, as well as synthetic drugs; that inhibit or kill microbes in small amounts. Chemotherapeutic agents are antimicrobial chemicals (natural or synthetic) that can be used internally or may be absorbed.

A total of 88 S. aureus were isolated from different samples including surfaces (n=34, 38.9%), personnel (23, 26.6%), air (20, 23%) and patients (11, 11.9%).

Staphylococcus aureus is a leading cause of human bacterial infections worldwide1, and following the discovery and widespread utilization of antibiotics, S. aureus has evolved to become resistant to a number of antimicrobial treatments. Most notably, Methicillin-resistant Staphylococcus aureus (MRSA) strains have acquired the mecA gene, encoding the penicillin binding protein (PBP2a), which confers resistance to oxacillin and all β-lactam antibiotics 2. These characteristics, combined with other virulence factors, have made MRSA infections difficult to treat, and lead to MRSA being recognized as a significant cause of morbidity and mortality 3. MRSA is also the leading cause of nosocomial infections4–6, contributing significantly to increased healthcare costs 7. CDC estimated in 2008 that MRSA was responsible for 89,785 cases of disease, causing 15,249 deaths in the US8.

Staphylococcus Aureus, commonly known as “Staph”, is present on most of the population on our skin and in our nostrils and throat. It can live on even the healthiest, cleanliest individuals. The staph bacteria do not cause harm until there is an open area or break in the human’s main defense system, the skin. Once the bacteria enter the wound, an infection may occur.

Life History and Characteristics: Staphylococcus aureus is a gram positive bacterium that is usually found in the nasal passages and on the skin of 15 to 40% of healthy humans, but can also survive in a wide variety of locations in the body. This bacterium is spread from person to person or to fomite by direct contact. Colonies of S. aureus appear in pairs, chains, or clusters. S. aureus is not an organism that is contained to one region of the world and is a universal health concern, specifically in the food handling industries.