Volume 6, Spring 2008 - Saddleback College

Fall 2007 Biology 3A Abstracts
Figure 1. Average inhibition growth of E. coli after the
first 48 hour period. Error bars indicate SE. Average
inhibited growth of E. coli in 1.0% AgNO3 was 0.52 ± 0.11
(SE). The 0.5% AgNO3 sample obtained an average
inhibition of 0.26 ± 0.02 (SE). A two tailed t- test was
calculated to have a p value of 0.08.
The inhition growth of E. coli under the two
types of silver nitrate solutions appeared to increase
within the 1.0% sample over a 96 hour period as
shown in Figure 2, but started to remain constant
within the 0.5% silver nitrate samples. Although the
inhibition growth increased in both concentrations
there was no net significance in the first trial, P value
was more than 0.05 (p = 0.08). The experiment was
run for 48 hours longer to further determine if there
was a significance in inhibition. After the second trial
p= 0.008, which indicated a statistical significance in
the inhibition growth of E. coli under the 1.0%
solution. The final results confirm our initial
hypothesis and conclude that there is a statistical
difference in the inhibition growth of E. coli under
both silver nitrate solutions.
concentration. According to an article by Wong and
Jelacic (2000) in the New England Journal of
Medicine, individuals that were treated with
antibiotics for E. coli infection experienced
symptoms of hemolytic uremic syndrome. Factors
significantly associated with the hemolytic–uremic
syndrome were a higher initial white-cell count
(relative risk, 1.3; 95 percent confidence interval, 1.1
to 1.5), evaluation with stool culture soon after the
onset of illness (relative risk, 0.3; 95 percent
confidence interval, 0.2 to 0.8), and treatment with
antibiotics (relative risk, 14.3; 95 percent confidence
interval, 2.9 to 70.7). Through trial and error
investigators can uncover the most effective
antibacterial agent to ward off E. coli. The 1.0%
silver nitrate concentration did exhibit growth
inhibition, as well as the 0.5% silver nitrate
concentration and the results concluded that there is a
significant difference with the use of silver nitrate.
Previous investigators had similar findings in with
the use of silver derivatives such as Feng and Wu,
who concluded that morphological changes took
place in bacteria treated with silver ions. Jack and
Tagg also found that gram positive strains of bacteria,
such as E. coli, can only by inhibited by
destabilization of membrane functions. A function
known of silver nitrate is to cause destruction of the
cell according to Sondi and Sondi. This knowledge is
a positive indication that silver nitrate is effective in
the inhibition of E. coli, and if it could be derived in
antibiotic form to treat infected humans, it would be a
turning point in the field of medicine and bacterial
control.
Literature Cited
Feng, Q.L. and Wu, J. (2000). A mechanic study of
the antibacterial effect of silver ions on Escherichia
coli and Staphylococcus aureus. Journal of
Biomedical Materials Research. 52: 662-668.
Figure 2. Average inhibition growth of E. coli after the
second 48 hour period. Error bars indicate SE. Average
inhibited growth of E. coli in 1.0% AgNO3 was 0.57 ± 0.06
(SE). The 0.5% AgNO3 sample obtained an average
inhibition of 0.26 ± 0.01 (SE). A two tailed t- test was
calculated to have a p value of 0.008.
Discussion
Growth inhibition of E. coli and many other
bacteria has been an issue at large in the medical field
and investigators continue to pursue new research
methods to improve the modes of treatment. The
results of this trial concluded that there is a
statistically significant difference in the inhibiting
growth of E. coli between the 0.5% silver nitrate
concentration and the 1.0% silver nitrate
Jack, R.W. and Tagg J.R. (1995). Bacteriocins of
gram positive bacteria. Microbiology and Molecular
Biology Reviews. 171-200, Vol 59, No. 2
Nataro, J and Kaper, J. (1998) Diarrheagenic
Escherichia coli. Clinical Microbiology Reviews. p.
142-201, Vol. 11, No. 1
Schreurs, W.J. and Rosenberg, H. (1982) Effect of
silver ions on transport and retention of phosphate by
Escherichia coli. Journal of Bacteriology. 152: 7-13
Sondi, I. and Sondi, B. (2004) Silver nanoparticles as
antimicrobial agent: a case study on E. coli as a
model for Gram-negative bacteria. Journal of Colloid
and Interface Science. 275: 177-182
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Saddleback Journal of Biology
Spring 2008