Soraya Pashaei Marandi Bio 111 543 7 October 2015 Assignment 5 Cell Case Study Background In order to classify a bacteria the chemical and physical properties of their cell walls are taken into consideration A Gram s stain test is conducted to test whether a bacteria is Gram positive or Gram negative Gram positive bacterias have a complex network of amino sugars that form a cell wall For this type of bacteria the test results will come back as blue purple On the other hand Gram negative bacterias have a cell wall with less peptidoglycan and their test results appear to be pink Broad spectrum antibiotics target both Gram positive and Gram negative bacteria while narrow spectrum antibiotics target either or Results For this cell case study a sample A bacteria and a Sample B bacteria were placed on separate microscope slides They were then each stained with crystal violet and the crystal violet was then trapped with iodide solution To decolorize the samples alcohol was poured onto the slides They were then counterstained with safranin in order for Gram negative bacteria to appear a pink color Each slide was observed under a 100x objective microscope Culture A appeared to be pink with a bacillus shape Escherichia coli This meant that Culture A of Mary Farmer was a Gram negative bacteria Culture B appeared to be a blue purple color with a coccus shape Streptococcus aureus This meant that Culture B of Brian Evans was a Gram positive bacteria The next step was to observe the sample of antibiotics and measure the zones of bacterial inhibition These zones would be where there were clear circles around the antibiotic disk The results varied among the different antibiotics and the different cultures Some antibiotics were more resistant to the bacteria and therefore would not be a reasonable treatment for the patients For Mary Farmer Culture A she should be prescribed Nalidixic Acid because it was the antibiotic that was most sensitive to Culture A For Brian Evans Culture B he should be prescribed Penicillin because it was the antibiotic that was the least resistant Some misconstrued results could come from leaving the alcohol on the slide too long which would strip the Gram positive bacteria cells Another problem could arise from having too many cells of the bacteria placed on the slide because it becomes difficult to view the result under the microscope Questions 1 The most effective antibiotic for Culture A was Nalidixic Acid 2 The most effective antibiotic for Culture B was Penicillin 3 Both children do not have the same infection considering the Gram s stain bacteria shapes and the antibiotic test results 4 Bacteria A came back with a Gram negative test result and Bacteria B came back with a Gram positive test result 5 Neither patient would be infected with more than one strain 6 Not all the bacterias were resistant to antibiotics however some were 7 I suggest Dr Fields prescribes Mary Farmer Nalidixic Acid as treatment He should then prescribe Brian Evans Penicillin
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