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Essay about Unknown Lab Report
Background: In Jane Horack’s article “Staphylococcus epidermidis”, S. epidermidis is described as “gram-positive cocci bacteria that are part of the normal flora on the skin and nasal passages. ” The article goes on to say that the species was originally named Staphylococcus Albus by microbiologist Rosenback in 1884. When viewed under a microscope S. epidermidis will appear in chains, pairs, or grape-like clusters (Horak 1). Taxonomically, the species S. epidermidis falls in the genus Staphylococcus, which is in the bacterial family Staphylococcaceae. S. pidermidis is in the phylum Firmicutes, under the Bacillales order. Like many members of the genus Staphylococcus, S. epidermidis is non-motile, as well as non-spore forming (Horak 1). The species is also facultative anaerobes, but not all strains of S. epidermidis will ferment. S. epidermidis is catalase positive, and this sets them apart from other gram-positive cocci, such as Streptococcus. They are also urease positive, cannot utilize Mannitol, and are resistant to several antibiotics (Horak). Staphylococcus epidermidis is considered “an opportunistic pathogen. It usually has a symbiotic relationship with its host, and for this reason it rarely causes diseases and is usually considered nonpathogenic (Avdic, Habes, and Avdic 3885). Recently though, the microorganism is becoming the common cause of nosocomial infections. In “Microbiology: with diseases by taxonomy”, Richard Bauman defines a nosocomial infection as “a disease acquired in a healthcare setting. ” These infections are often found with implants and plastic items that have inserted into the body, such as catheters, pacemakers, and urinary catheters (Avdic, et. l 3885). “The ability of this microorganism to causes infections is primarily due to its ability to form biofilms on synthetic surfaces of implanted medical devices” (Avdic, et. al 3885). Biofilms are considered the primary residence of microorganisms in nature, and are composed of numerous microorganisms (Bauman 173). Numerous studies clearly show that a large number of hospital strains have the ability to form multilayered biofilms on inert surfaces (Avdic, et. al 3886).
The formation of biofilms has serious clinical consequences and is the cause of many persistent and chronic infections particularly in patients who have long been hospitalized or are in critical condition. (Avdic, et. al 3886). These infections are more severe in patients with compromised immune systems, such as the elderly, young children, or cancer patients (Horak 2). One of the biggest concerns with S. epidermidis is the frequency of these nosocomial infections. As these infections become more prevalent, antibiotic resistance is quickly increasing (Horak).
In Michael Otto’s article “Staphylococcus epidermidis – the “accidental” pathogen”, he suggests the reason for this resistance is due to antibiotic overuse. Vaccination and decolonization has been discussed as preventative measures, but there is currently no vaccine for S. epidermidis, and the effect of decolonization may prove counterproductive. If S. epidermidis was removed from the normal human flora, it might allow other microorganisms to colonize (Otto). For those reasons, it is commonly agreed that best way to deal with S. epidermidis infections is by a series of preventative measures.
Staphylococcus Epidermidis biofilm Staphylococcus Epidermidis biofilm Materials and Methods: There were series of tests performed before the unknown could be properly identified. The unknown was first plated using the antiseptic technique. The aim of the antiseptic technique is to separate colonies of each microorganism so it may become easily distinguished and pure colonies will isolated. The process began by flaming the inoculating loop over the Bunsen burner to kill any pre-existing bacteria. The neck of the vial containing cells of the unknown was also flamed to kill any existing microorganism.
The inoculation loop was then dipped in the nutrient broth, and neck of the vial was flamed once again. After a brief cool-down, the inoculating loop was streaked across a nutrient agar plate using the Quadrant Streak method. The Quadrant Steak method involves smearing the bacteria in quadrant one. The quadrant begins at the top of the agar plate, the loop is smeared into a downwards motion. Following this process, the inoculating loop was flamed once again. After the loop cooled down, a single colony from quadrant one was targeted and smeared into quadrant two, and was followed by flaming the inoculating loop.
The process was repeated to smear bacteria into the remaining quadrants three and four. The agar plate was then turned upside to prevent condensation from dipping onto the culture and causing contamination. The process was repeated four additional times on to a phenylethyl alcohol agar (PEA), a Mannitol slat agar (MSA), a MacConkey agar (MAC), and an eosin methylene blue agar (EMB). Following the incubation of the several agar plates, the growth of colonies allowed for the next step in diagnosis – staining. The simple stain was performed first and can be used to determine cell shape, size, and arrangement.
The process required the inoculating loop to be flamed once more, and a loopful of the culture was smeared onto a clean slide. A drop was water was applied onto the slide, and mixed to create a thin film. After the water had dried, the slide was heat-fixed. The heat-fixture ensured the bacteria would not be removed during the staining process. The slide was then covered with the agent Methylene blue for thirty seconds, and the excess dye was removed with water the gentle blotting. S. epidermidis – simple stain S. epidermidis – simple stain
Following the simple stain, the Gram Stain was performed. The Gram Stain is a procedure used to determine the presence or lack of peptidoglycan in the cell walls of a bacterium. The process began with flaming the inoculation loop, and smearing a colony of bacteria onto a clean slide. A drop of water was applied and smeared to create a thin film. After the water had completely dried, the slide was then passed through the Bunsen burner. This adhered the bacteria to slide. The slide was then stained with Crystal Violet for sixty seconds, and completely rinsed with distilled water.
The slide was rinsed with distilled water after every step. After the crystal violet, the slide was covered in Iodine for sixty seconds, and rinsed. Following the Iodine, the slide was decolorized with 95% ethyl alcohol-acetone for three to five seconds, and rinsed. The last step was the counterstain with Safrain for thirty seconds, rinse, and gently blot off the excess water. If the bacteria retained a purple stain, it was considered Gram-positive. However, if the bacteria possessed a pink or red stain, it was considered Gram-negative. S. epidermidis Gram-stain S. epidermidis Gram-stain