preterm birth risk linked to DIVERSITY of microbes in AMNIOTIC FLUID

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*Preterm Birth Risk Linked To Diversity Of Microbes In Amniotic Fluid *

http://www.medicalnewstoday.com/articles/119390.php

US researchers have discovered a significant link between the number and

range of bacteria or fungi in a mother's amniotic fluid and the *degree

to which her baby is born premature and sick.

*

Scientists at Stanford University Medical School in California, and

colleagues from other establishments, published their findings in the

26th August issue of the open access online journal /PLoS One/. [link to

article hereinbelow]

About 12 per cent of all births in the US are premature and the figure

is going up, wrote the researchers, who were led by research associate

Dr Dan DiGiulio, in the lab of senior author Dr Relman. They found

that previously unrecognized and unidentified infections of amniotic

fluid may account for a significant number of these births:

" If we could prevent these infections in the first place, or detect them

sooner, we might one day be able to prevent some of these premature

births, " said DiGiulio.

DiGiulio and Relman worked with colleagues at Wayne State University in

Detroit, the Detroit Medical Center and the Eunice Kennedy Shriver

National Institute of Child Health and Human Development and analyzed

amniotic fluid from women in preterm labour. They found that 15 per cent

of the fluid samples contained bacteria and fungi. This figure is

considerably more than the amount given in previous estimates.

The researchers also found that the more diverse the range of microbes

(the " burden " of potentially infectious agents), the more likely the

women were to give birth earlier and also to have sicker babies.

Relman, who is professor of infectious disease and also of microbiology

and immunology at Stanford University Medical School, said they were

shocked to find that:

" This amniotic compartment, which we have traditionally viewed as

somewhat sacrosanct, *is infected significantly more often than we thought. "

*Previous studies using a more conventional sampling method had

estimated the infection rate at around 10 per cent.

For the study DiGiulio and colleagues examined the amniotic fluid of 166

women who went into preterm labour at the Detroit Medical Center between

October 1998 and December 2002. 113 of the women actually went on to

have preterm babies.

They used a modern technique called PCR, short for polymerase chain

reaction, which is more sensitive than the conventional method to detect

microbes like bacteria, fungi and other living organisms, which relied

on taking a sample of amniotic fluid with a needle inserted into the

amniotic cavity and then culturing and growing them in the lab. But this

rather " rough " technique did not pick up the full range of microbes in

the samples.

DiGiulio said scientists have become very good at cultivating some of

the " weeds " of the microbial world but many species of micro-organisms

don't respond to culturing. PCR uses scraps of DNA that encode portions

of ribosomal RNA (rRNA) to detect the full range of individual species

present, including those that don't respond to being cultured.

By using a mix of PCR and lab cultures, they estimated around 25 per

cent of the 166 samples taken from the women who went into premature

labour were infected with bacteria or fungi. The total range of

micro-organisms they found spanned 17 different bacteria and one fungal

species, considerably more than the 11 found by conventional means.

These included some known species that scientists did not realize played

a role in preterm delivery and one completely new one not seen before.

DiGiulio and Relman also discovered that:

* All the women whose samples were positive by either PCR or by

culture had their babies prematurely.

* All those who were positive by both methods had their babies

within one day of the initial fluid collection.

* 68 percent of those that were positive by only one, but not the

other, method delivered within the same time period.

* 27 percent of samples from infected women who delivered their

infants before 25 weeks gestation were positive only by PCR.

* What was interesting was that using the culture method alone,

failed to show that these samples were infected.

This last statistic is important because only 30 per cent of preterm

babies in this age group (born before 25 weeks of gestation) survive.

The scientists said it was very important to be able to diagnose

infection accurately in these women.

DiGiulio and colleagues also found that the babies arrived earlier when

the burden of infection increased. Thus the greater the number and range

of bacteria and fungi, as detected by rRNA, in the amniotic fluid

sample, the more likely the mother was to be delivered of a very young

and very sick baby.

Speculating on their results, the researchers suggested that infected

amniotic fluid may contribute to preterm birth because it triggers an

inflammatory response in the pregnant mother. The microbes either travel

from the vagina into the amniotic sac, or get into the mother's

bloodstream from other parts of the body like the mouth. Other studies

have linked gum disease and bacterial vaginosis to increased risk of

early delivery.

*/ " Microbial Prevalence, Diversity and Abundance in Amniotic Fluid

During Preterm Labor: A Molecular and Culture-Based Investigation. " /*

DiGiulio DB, Romero R, Amogan HP, Kusanovic JP, Bik EM, et al.

PLoS ONE 3(8), 26 August 2008, e3056.

DOI:10.1371/journal.pone.0003056.

*Click here for Abstract.

<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0003056>*

Sources: Journal Article.

Written by: Catharine Paddock, PhD

Copyright: Medical News Today

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