Aim
The essence of performing this experiment was to ascertain the degree of infestation of Staphylococcus aureus in the general public (students).
Introduction
Our bodies form a natural habitat for pathogenic strains of staphylococcus aureus. The degrees of infestation vary on our body surfaces with much concentration biased towards the nasal cavities (Toshkova 19). Even with their presence, their effects remain insignificant not unless their threshold capacity, which depends on one’s occupation, is exceeded. As such, it has been established that their concentrations per population fall within a bracket of 10-40% and 50-70% for the general public and hospital staff respectively (Lonneke 14). For these groups, excess of these concentrations represents a health hazard in their respective areas. For food handlers, it may result in food poisoning thus calling for microbial screening as a precaution. Also, screening is done on hospital staff to avert any secondary infection.
To investigate their presence, sterile swabs are used to collect them from their respective areas of habitation. This is followed by a recovery procedure using Mannitol salt agar (MSA) which is later followed by a series of isolation and confirmation tests. This method is vital in unearthing the root cause of disease in case of an outbreak.
Materials/ reagents
Hydrogen peroxide, nutrient agar plate, coagulate tube, specimen (students), a streaking loop, Mannitol salt agar plate, sterile swabs, and incubator.
Method
Taking the nostrils as their most probable location for their presence, sterile swabs were used to collect the strains after which they were cultured in MSA (selective media). This was then followed by streaking of dilute using a flamed loop after which it was aerobically incubated for 36 hours under temperatures of 350 C.
A microscope was used to observe the presence of opaque colonies encompassed within bright yellow zones were investigated. For the student (s) whose test would turn out positive, gram staining and catalase test were to follow. The ultimate test would be the plate coagulase test which would be performed only when the previous test would turn out positive (Toshkova 20). A nutrient agar would be used as a sub-culture to obtain enhanced pure colonies in case of insufficient colonies. All the positive results were later recorded for analysis to determine the concentration of the group tested.
Results
Table 1: of concentration of Staphylococcus aureus in student population from the year 2010 to 2012.
Discussion
The objective of this experiment was to determine the degree of infestation of Staphylococcus aureus in students which are theoretically believed to be falling within the range reserved for the general public (10-40%). From the experimental results, as exhibited by table 1 above, the results concurred with the theoretical. Nearly all the tests for the previous years showed consistent results the theoretical.
Concentrations exceeding the theoretical value mean that the group in question poses a great danger that may result in either cross-contamination in a hospital setting or, food poisoning for food handlers. As such, food handlers in food processing sectors are advised to use protective clothing as a preventive measure against the possibility of food poisoning. This is normally explicitly spelled out and documented as Good Hygienic Practice (GHP).
Previously, MSA typically a selective as well as a deferential media was used to inhibit the growth of nonstaphylococcus strains while at the same time enhancing the growth of pathogenic staphylococci cultures. Staphylococcusaureus is a gram-positive bacterium hence, the essence of doing gram staining was to establish its identity (Lonneke 10). As expected, for students who tested positive, the results turned positive confirming that the bacterium has a thick peptidoglycan wall responsible for retaining the violet stain observed. To separate or distinguish staphylococcus from streptococcus strains effectively catalase test is normally applied. The former is catalase positive while the latter is catalase-negative, and as expected the results turned positive for the students turned positive for the test (Toshkova 18).
Ultimately, the coagulase test performed was to substantiate the real identity of the strain. This is so because not all gram-positive and catalase-positive strains are pathogenic cocci. Coagulase-positive strains (where S.aureus falls) can protect themselves from immune responses, phagocytes, and antimicrobials. They achieve this by engaging the fibrils of the plasma to form a protective layer. The rationale behind incubating these strains at a temperature of 350 C. is because this is almost the body temperature; the habitat temperature where their enzymes perform optimally.
Conclusion
The aim of performing this experiment, to ascertain the degree of infestation of Staphylococcus aureus in the general public (students), was achieved. This is so because it was established that the range expected for a general population is10-40%.
Works Cited
Lonneke, Bode. “The new England journal of medicine.” Preventing Surgical-Site Infections in Nasal Carriers of Staphylococcus aureus 362. 1 (2010): 9-17. Print.
Toshkova, Katia. “Microbiology and virology.” The significance of nasal carriage ofStaphylococcus aureusas risk factor for human skin infections 102. 1 (2001): 17-24. Print.