Page 86 - 75_02

ANTONIO L. DOADRIO Y COLS. AN. R. ACAD. NAC. FARM.

434, described as standard of sensitivity likely was less affected than
E. coli CECT 516, used in resistance to metals.

In the S. aureus spp aureus cultures, two different media were
used: TSA and blood agar. The later provided an environment similar
in somewhat manner to the mammalian tissues, because is a protein-
rich medium containing cellular rests. cefotaxime was effective
against those strains of S. aureus spp aureus, but the sensitivity was
increased in the TSA cultures. It could be justified because an
antibiotic sequestration by protein binding occurred in the blood agar
medium. cefotaxime is reported to bind proteins, so the amount of
free antibiotic would be 27-38% reduced in the presence of proteins
(11). It means that the amount of functional antibiotic was lesser in
the blood agar. Our findings agreed the reported data, because the GIZ
in blood agar had mean values 25% smaller than in TSA cultures.

As observed in E. coli, the two strains assayed did not show the
same results regarding the level of sensitivity to cefotaxime. However
the experimental results were not enough to build statistical analysis,
it seemed, comparing the data of the E. coli and S. aureus spp aureus
strains, that the intensity of the antibiotic aggression could have a
strain dependent component in each of the sensitive species.

As above mentioned, the importance of this work is to know
whether the complex, antibiotic-metal has biological activity against
the strains of microorganisms studied.

The cefotaxime-copper complex (Table 5) had some activity
against B. subtilis CECT 356 and E. coli CECT 516 only at the highest
concentration used, being harmless at lower concentrations.

The results would induce misleading conclusions. Apparently,
there waas a moderate microbicide activity against the model species,
but a matter of scale should be addressed. cefotaxime was fully
active at µM concentrations or lower, whereas the complex derivate
required a concentration six orders of magnitude higher to affect
slightly the cell viability. The maximum concentration in vivo of
cefotaxime reported in adult patients with a normal renal function
is 55 µM (1,11), so the microbicide effect of the complex lacked of
a practical relevance in physiological terms.

Finally, we wish to warm about the clinical outcome of our finding:
antibiotic treatment based on cefotaxime in copper poisoned patients

230