By Terry Vanderheyden

MADRID, January 3, 2006 ( – Spanish researchers have found that mice conceived using sperm exposed to E.coli bacteria before artificially inseminating a mouse egg, retain the genetic code of the bacteria in their DNA.

The finding raises new concerns for in-vitro fertilization as an alternative to natural procreation, especially as IVF has become increasingly popular for couples experiencing difficulty in conceiving a child.

Scientists from Spain’s agricultural research agency, INIA, used a method of IVF known as intracytoplasmic sperm injection (ICSI), to inject a single sperm directly into an egg – a method used for men with low sperm count or poor sperm motility. The method is used in approximately half of all IVF procedures, according to a BBC report.

Sperm that was frozen and later implanted was found to transmit the E.coli DNA to the embryo 19% of the time, whereas of those embryos that successfully implanted into female mice, only 6% retained the genetic material.

The scientists, led by Pedro Nuno Moreira, warned that “semen samples collected in human infertility clinics are frequently contaminated with bacteria,” according to their report that appeared in the journal Human Reproduction. The title of their research, Inadvertent Transgenesis by Conventional ICSI in Mice, highlights the crux of the problem: that DNA from the bacteria actually alters the genetic structure of the DNA in the resulting embryos.

The term transgenesis refers to the altering of an organism’s genetic code by the transfer of a gene or genes from another species or breed. Mixing sperm with foreign DNA has also been proposed as a way to intentionally alter the genetics of the offspring.

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