Monthly Archives: December 2009

Hitting the headlines this week

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Mapping our microbes

Researchers have successfully mapped the different microbial communities over the whole body according to research by Costello and colleagues published in Science this week.

The human body is home to trillions of bacteria, so many that in fact bacteria outnumber our own cells by 10 to 1. The human body’s microbiota (the microorganisms that live inside or on our body) is often diverse and complex. It is important to examine the different communities of bacteria that live in association with a healthy human body so that we can better understand how these microorganisms affect our health.

The researchers assessed the diversity of bacteria in different habitats on the body, in different people and whether these bacterial communities changed over time. Over the course of three months, the researchers surveyed and sequenced the different bacteria from up to 27 human body sites – including the ear canal, gut, mouth and skin – in seven to nine healthy adults. They found that bacterial communities were defined by their location on the body. Some body sites, like the back of the knee or the gut, have many different types of bacteria living there whilst places like the navel or forehead have very few types of bacteria. These bacterial communities within each habitat varied little over time in individuals. Surprisingly, some skin sites – including the forearm, palm, index finger and back of the knee – had a greater diversity of bacteria compared with the gut and the mouth (body sites known to harbour many different types of bacteria). The researchers then “transplanted” bacteria from one site on the body to another (after sterilisation) and monitored which bacteria grew to test whether some parts of the body were more hospitable to bacteria than others. For instance, tongue bacteria could grow on a person’s forearm but not on their forehead and similar results were achieved when transplanting one person’s tongue bacteria onto another person’s forearm or forehead. Finally, the researchers found that different people had very different types of bacteria living on them (we have our own personalised set of microorganisms living on us).

Further work is needed to survey the human microbiota of more people and how it changes over a longer period of time. Studies like the Human Microbiome Project will help to map the microbes of many more people and further our understanding of the microbial factors which are associated with health and disease.

ResearchBlogging.org
Costello, E., Lauber, C., Hamady, M., Fierer, N., Gordon, J., & Knight, R. (2009). Bacterial Community Variation in Human Body Habitats Across Space and Time Science, 326 (5960), 1694-1697 DOI: 10.1126/science.1177486

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Prophylactic antibiotics do not prevent preterm birth

Routine prophylaxis with antibiotics does not prevent preterm birth in high risk populations according to research by van den Broek and colleagues published in PLoS Medicine.

Most pregnancies last about 40 weeks, babies born before 37 weeks of completed pregnancy are considered premature. Premature birth is a major cause of infant mortality and morbidity in high- and low-income countries. Babies born prematurely often have long-term health problems and disabilities. There are many causes of preterm birth but it has been previously shown that infection (especially ascending genital tract infection) is an important contributing factor.

This study investigated whether prophylactic antibiotics (in this case Azithromycin), given to pregnant women regardless of whether they are showing signs of infection, prevented premature birth. The researchers enrolled 2,297 pregnant women in Southern Malawi in the Azithromycin for the Prevention of Preterm Labor (APPle) study. This was a randomised, community-based, placebo-controlled trial; half the women were given azithromycin at 16-24wks and 28-32wks whilst the rest received a placebo tablet at similar times. The health of both mother (such as malarial status and anaemia) and baby (gestational age at delivery and birth weight) was monitored up to 6 wks after delivery. There were no significant differences in outcome (including preterm birth, mean gestational age at birth, mean birth weight, perinatal death and maternal anaemia) between the azithromycin and placebo groups of women. Furthermore, meta-analysis (combining results of several studies) of these results with seven other similar studies showed that prophylactic antibiotics in pregnancy had no effect on preterm birth.

Clearly, these findings do not the support the use of antibiotics as prophylaxis to prevent preterm birth. It is unknown why these results are negative given the fact that infection has been associated with preterm birth. More work is needed to determine whether different antibiotics or doses might be useful, and to identify alternative strategies for the prevention of preterm birth.

ResearchBlogging.org
van den Broek, N., White, S., Goodall, M., Ntonya, C., Kayira, E., Kafulafula, G., & Neilson, J. (2009). The APPLe Study: A Randomized, Community-Based, Placebo-Controlled Trial of Azithromycin for the Prevention of Preterm Birth, with Meta-Analysis PLoS Medicine, 6 (12) DOI: 10.1371/journal.pmed.1000191

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Filed under Infectious Disease, Medicine

Hitting the headlines this week

  • skunk users at greater risk of psychosis
  • Obama to attend end of Copenhagen climate summit
  • debate over drug companies and clinical trials still rages
  • Cave spiders return home
  • Would you eat lab grown meat?
  • Measles deaths worldwide reduced by 78%, but more vaccinations needed to prevent the disease resurging.

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