Introduction: In the following report we will research and discuss possible antibiotics to recommend to Dr Livingston, who has asked my team and I the pathologists, to recommend an antibiotic to treat two patients who he treats. Both have recently had hip replacement surgery and have later fallen and received cuts to the same area, which is now infected. Dr Livingston has taken biological samples form patient A and Patient B; he is unsure what bacteria could be causing the infections. It is our job to research and decide what bacteria could be causing the infections on both patients. Dr Livingston believes that the infections could be Staphylococcus epidermidis infection from the hip replacement surgery or Escherichia coli infection which could be form the abattoir were both patients work. Both infections require different treatment, sample A and Sample B have been sent to the pathology lab to be analysed.
The infection E. coli (Escherichia coli) is a common type of bacteria that can get into your food, like vegetables or beef. E. coli is not always harmful, you find E. coli in your intestines where it helps to break down and digest food. But sometimes it can get in to your blood and cause a very serious infection. It is estimated the 73 000 cases of E. coli occur in the united states every year and 61 deaths as a result. Someone who has E. coli may have symptoms like bad stomach cramps, vomiting and diarrhoea, sometimes with blood in it. E. coli grows in an opaque coloured colony and is Gram –‘ve. E. coli is resistant to penicillin G and is susceptible to most other antibiotics.
The infection S. epidermidis (Staphylococcus epidermidis) is a bacterium commonly found on the skin that is normally harmless. But can get into the blood and cause a blood stream infection which can lead to a lot of other infections. This Infection mostly affects people with weakened immune systems e.g. Newborns or people with implanted medical devices such as prosthetic joints. S. epidermidis is Gram +’ve and is small bacteria that appear to grow in individual cocci when seen under a microscope. S. epidermidis also grows in an opaque coloured colony. S. epidermidis is resistant to the antibiotic Sulphertriad, but is susceptible to most other antibiotics.
Scanning electron image of S.epidermidis Scanning electron image of E.coli
The first procedure used when researching the samples is Bacterium isolation (16 Stroke technique). This technique is used to spread and separate the colonies into individuals on the agar plates. Each colony consists of one type of bacteria. This technique is done to isolate one bacterium so it can be sampled to see if it is gram positive or negative. When spreading the bacteria on the agar plate only a tiny bit is used. It is spread with a special sterilised flame loop. Sterilising the flame loop between each phase of the Bacterium Isolation is very important because it stops cross contamination. The flame loop must be heated till red hot and then cooled for best results.
[pic] Image of bacteria on an agar plate spreed using the 16 stroke tecnique.
Another procedure used when researching the samples is the Gram stain procedure. This is the first step in identifying bacteria. It is a four step procedure the uses certain dyes, crystal violet, iodine, ethanol preparation and safranin, to make a bacterial cell stand out. All bacteria can be divided into two main sub-groups; physical properties in the cell membranes define the two groups. The two groups are Gram positive (Gram +’ve) and Gram negative (Gram –‘ve). Gram positive bacteria have a thick mesh like cell wall made of peptidoglycan (50- 90% of the cell wall) which gets stained purple or blue by crystal violet when tested. Peptidoglycan is a polymer (a large molecule composed of repeating structural units) that consists of sugars...