Recently I completed my sixth year investigation on the topic of
Staphylococcus Epidermidis bacteriophage properties. I investigated the
susceptibility of these strains of bacteria: NCTC RP62A, 11047 and 1457. I
found that the usual method of estimating the phage concentration in a
solution ( by using one dilution and multiplying it by the dilution factor)
was too inacccurate because:
It assumed 100% infectivity and lysis. It was found that if several
dilutions were used and the no. of plaques produced were counted a best fit
line could be obtained ( value for thr regression constant was no less than
0.89, with 1 being a perfect straight line). Thus it was concluded that a
line with a gradient of 1 shows 100% infectivity and lysis due to the phage
and that the estimated concentration was accurate. However, in most cases
this did not happen (gradients of 0.45, 0.89....) and thus the final estimate
was too low. Thus obtaining those lines gave indication of how good the
estimate was and how susceptible the bacteria are. Please, send me any
comments, critisisms or questions as I will be working on this project again
in the summer.
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