His vital signs reported a temperature of 39.4 degree C, pulse 112/min, resting
ID: 167152 • Letter: H
Question
His vital signs reported a temperature of 39.4 degree C, pulse 112/min, resting 18/min and blood pressure 124/70 mmHg. On exam, his lower left leg was swollen and tender. The overlying skin was warm and red with multiple necrotic-appearing lesions (Figure 1). The knee joint was normal with full range of motion. Laboratory studies showed a differential of 68% PMNs and 10% bands, 16% lymphs, with a white blood cell count of 16, 400/mu L. His hematocrit was 42%, his ESR was 98 mm/hr and his C-reactive protein was 18 mg/L unit. His serum chemistries were normal. X-rays of the left femur showed soft-tissue edema without any abnormalities of the bone. Bone scans of the same area showed intense uptake in the proximal femur. Blood and wound aspirate were obtained and sent for gram stain and culture (Figure 2A & B). 1. Describe what you observed in Figure 2A & B. The organism is catalase and coagulase positive. What organism was causing his infection? Susceptibility results for this organism are seen in Figure 3. How do you interpret these susceptibility results? Explain the likely reasons for the results seen with drugs 2 and 4. What test is being used to test vancomycin (drug 5)? Why is this test being used and what does it show? What virulence factor is particularly associated with skin and soft tissue infections (SSTis)? Explain its mechanism of action. This virulence factor and this type of antibiogram are associated with a particular strain of this organism. Briefly discuss the evolvingExplanation / Answer
In figure 2A it is showing violet or blue coloured of developed colony of the strain which is responsilbe for the disesase. figure 2B it is showing colony formation morphology of the responsible strian.
from hte figure the morphology of the colny is as follow
shape of colony: round shape,
the possible organism to cause this infectionis gram positive strin
it may be species of Staphylococcus, Staphylococcus aureus , methicillin resistant Staphylococcus aureus
colour of colony:white or slight gold
if it is gold yhen it is due to the pigment produced by responsible strain.
2. it is the zone inhibition
it is done with the help of antibiotic zone.
first responsible strin is developed using apporopriate nutriant medium after that that the measurment of antibiotic capacity in terms of zone inhibition.
drug 2 shows the larger zone of inhibition as comare to zone 4 means drug 2 is more potent as compare to drug 4 in terms of antibiotic capacity.
3. Vancomycin is an antibiotic used to treat a number of bacterial infections.
vancomycin test include below method
Disk diffusion test
Among the microbial susceptibility determination methods, the Disk Diffusion test is the most common one. In this method, after isolation of bacterium, some of the bacterial colony is dissolved in a physiology serum , then, it is transferred culture medium. Afterwards, the relevant antibiogram disks are put in the culture medium by distance of 11mm from each other. After capping them, they are incubated at 36°C for 24h. Next, under the light, the diameter of inhibition halo (growth inhibition halo) is examined and measured by ruler and compared with the reference tables, and then reports are provided as susceptible, resistant, or intermediate. Measurement of the inhibition halo must be done always with ruler. The length of the ruler should pass through the disk center to measure the diameter; all of these actions should be performed under the light.
if it is less than 13mm that means it is vancomycin resistent species.
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