Part 2 MRSA Screening A methicillin resistant Staphylococcus aureus MRSA screen is a test that looks for the presence of MRSA and no other pathogens It is primarily used to identify the presence of MRSA in a colonized person On a community level screening may be used to help determine the source of an outbreak On a national level additional testing may inform clinicians and researchers about the unique genetic characteristics of the strains of MRSA circulating in the community or health care setting A nasal swab is collected from the nares nostrils of an asymptomatic person and cultured put onto a special nutrient medium incubated and then examined for the growth of characteristic MRSA colonies A swab may be collected from a wound site or skin lesion of a person who has been previously treated for a MRSA infection and cultured similarly A screening culture identifies the absence or presence of MRSA and usually takes 1 to 2 days for a result When studying how bacteria respond to antibiotics the Kirby Bauer disk diffusion method is used In this technique discs containing antibiotics are placed on agar where bacteria are growing and the antibiotics diffuse out into the agar If an antibiotic stops the bacteria from growing we can see circular areas around the wafers where bacteria have not grown This area is called the zone of inhibition The diameter of these zones is measured as shown below 3 What methods would hospitals employ to eliminate MRSA from their facilities 4 What is a strain of bacteria How is it possible that some strains of Staphylococcus aureus can be harmless but others can be deadly You may need to google this 5 A young scientist suggests that a chemical found on the skin of frogs can be used as an antibiotic Explain how the Kirby Bauer disk technique could be used to support this hypothesis 6 Consider the data gathered from the frog skin experiment What conclusion would you draw from the data Site Frog Skin 0 1 2 3 Penicillin Amoxicillin Zone of Inhibition 5 1 2 cm 3 9 cm 3 6 cm