Superbugs, MRSA, Phages and Bdellovibrio

A New York-based urologist warned this week that laptops could be bad for mens' sperm counts. Dr. Yefim Sheynkin studied 29 men in their 20s and 30s and found that using a laptop for an hour increased the temperature of the average scrotum by over 2.5 degrees celsius, potentially affecting fertility. Previous studies have found that raising scrotal temperature by as little as 1 degree celsius is sufficient to affect sperm formation, but the volunteers in the laptop study achieved this rise in temperature after just 15 minutes on the computer. The effects of temperature on sperm formation are well known. A 1999 study showed that American mens' sperm production can drop by over 40% during the summer, compared to the winter, and that in hotter temperatures sperm speed drops and the number of defective sperms increases. On the basis of their findings Sheynkin and his team argue that regular daily laptop use could lead to chronically low sperm counts and advise users to put their laptop on a table whenever possible. They are now planning a follow up study to find out to what extent regular laptop use can affect mens' fertility.

Mark - MRSA, or Methicillin Resistant Staphylococcus aureus, is a special variety of a very common bacterium. We come into contact with it every day, and a third of us have Staphylococcus aureus up our noses all the time! MRSA is just a small group of this bacterium that has become resistant to a common type of antibiotics. The bacteria itself isn't particularly nasty; it is just more resistant to treatment, which has implications when trying to find ways of preventing and treating infection. The problems Staphylococcus would cause on a day to day basis are wide ranging, and are one of the commonest causes of infection in normal healthy people. When we have a cut, it is usually our own Staphylococcus that infects us. The MRSA strain was first found early 1960s, which was the same time that the antibiotic methycillin was introduced. The reason there were a few isolates of the resistant strain so early on is probably due to methicillin being related to beta-lactin. Beta-lactin is a natural antibiotic produced by fungi; probably used as defence against bacteria. Therefore, Staphylococcus has been in contact with the antibiotic for a long time, allowing a few resistant strains to evolve. It is only since people have been repeatedly prescribed antibiotics that problems have arisen. The non-resistant strains die out, leaving the resistant strains behind.

克里斯- When did MRSA become a big problem in hospitals?

Mark - it actually took quite a long time. For many years, the bacteria were only found occasionally, and only slightly more often in people in hospital than people not in hospital. MRSA started to appear in clusters of people in nearby beds, but the outbreaks were still small. The problem has increased as the resistant bacteria has been passed from patient to patient. The most significant method of transmission is via the hands of healthcare workers in general, not just doctors. If a patient has MRSA on their skin and receives care from a member of staff who forgets to wash their hands, the next patient they treat will have the bacteria passed onto them. It is important to distinguish between being colonised by bacteria and being infected by bacteria. Studies have shown that people visiting hospital acquire a range of bacteria different from those they came in with. However, they do not develop a similar range of infections: having MRSA on your skin does not necessarily mean that you will become ill.

An inhaler laden with viruses called bacteriophages, which prey selectively on bacteria, could be a new weapon to tackle MRSA infections. Nick Mann, from the University of Warwick, has been developing ways to use phages to combat hospital superbugs, as he explains to Chris Smith...

Nick - Bacteriophages are viruses that infect bacterial cells and kill them. The word bacteriophage literally means 'bacteria eater.'

克里斯- How do they grow?

Nick - Phages attach to bacteria and inject their genetic material into the cell. The genetic material makes more copies of itself, bursts the cell open and goes into the environment. One phage gives rise to, say, 100 new phages, which inject their genetic material into 100 more bacteria and so on. This amplifying process is one of the great benefits to phage therapy. Putting one phage into an infected wound will lead to a chain reaction that expands until all the bacteria are dead. This is in contrast to antibiotics, which become less concentrated and less effective the longer and further they travel into the body.

克里斯- How would you give the phage to the patient?

Nick - More trails are needed before we can start administering phages to patients, but we will probably start by putting them on surface wounds. This could be achieved by impregnating wound dressings with the phages. Once the bacteria have gone, the phages also die out. Another avenue we are exploring with regards to MRSA is trying getting rid of it in the nose. The phages will be delivered through a plastic inhaler. So far, it has been tried out on a couple of student volunteers which remained negative for MRSA for the few days we looked at them. We are going to do longer controlled trails and are desperately trying to get it into hospitals. If the nasal inhaler is given to visitors, staff, and patients, the levels of MRSA in hospitals will hopefully decrease.

克里斯- Will the bacteria become resistant to the phages like they have to some antibiotics?

Nick - The bacteria will become resistant, but phages are living and can mutate too. Therefore, the bacteria and phages will fall into an evolutionary arms race whereby both bacteria and bacteriophages will evolve methods to outwit the other. As long as phages can keep up, they will always be a threat to the bacteria.

Plants make food for themselves via photosynthesis. This process involves a number of chemicals, enzymes and pigments, including green chlorophyll. Copper stops the photosynthetic process from working, which is why copper is toxic to plants and algae.

The lines on the roof are likely to have been caused by copper: some builders purposely build copper strips into roofs to stop them going green.

As for killing a tree with a copper nail, I'm not sure that that is true: trees are very large and contain lots of water to dilute any copper particles put into it. Therefore, lots of copper would be needed to kill a tree.

Metallic copper (which a nail would be made from) does not go into solution easily and would find it hard to get into the tree's food and water transport systems.

就人类而言,我认为铜中毒是联合国likely in this area. The east of England has very hard water, which makes the water pipes fur up. This makes it hard for our drinking water to come into contact with the pipes.

Copper in small amounts is actually important for humans as it helps some of our enzymes work. Only in the genetic 'Wilson's disease' can copper be a problem where sufferers accumulate too much of the metal in their brains.

Tablets taken by mouth contain a lot of the actual antibiotic. They also contain lots of other substances which enable the manufacturer to produce a tablet that can be kept in packets and are easy to swallow. For example, the smooth outer coatings of some tablets are often made out of vegetable products. Once the tablet is in your stomach, the active bits distribute around the body through the bloodstream, reach the site(s) of infection, and kill the offending bacteria. There are three different ways antibiotics kill bacteria. Some stop bacteria from growing by stopping their protein production; others stop them from making chromosomes; and the third type stop bacteria from making cell walls. Without a proper cell wall, the bacteria explode and die.