Notorious pathogen forms slimy 'streamers' to clog up medical devices

A group of researchers from the US has moved a step closer to preventing infections of the common hospital pathogen, Staphylococcus aureus, by revealing the mechanisms that allow the bacteria to rapidly clog up medical devices.

In a study published today, 27 June, in the Institute of Physics and German Physical Society's New Journal of Physics, the researchers have shown that the bacteria colonizes into large groups, called biofilms, using a biological glue, and form thin, slimy, thread-like structures called streamers.

The streamers adhere to a surface and are able to trap passing cells as they flow through medical devices such as stents and catheters, becoming more rigid and eventually clogging up the whole device.

In their study, the researchers, from Princeton University, recreated the physical environments of medical devices with curvy channels, multiple networks and a flowing fluid, and showed that streamers can rapidly expand and create a blockage in a surprisingly short space of time.

Moreover, if the surfaces were coated with human blood plasma, which the bacteria often encounter in infectious sites, the biofilm streamers appeared in the structures even more quickly.

Methicillin-resistant Staphylococcus aureus (MRSA) is a notorious strain of the bacteria that has developed a resistance to antibiotics, making it particularly difficult to treat in humans.

MRSA is the most widespread cause of hospital-associated infections in the US and Europe, and has a high mortality rate. Patients with open wounds, implanted devices and weakened immune systems are at the greatest risk of infection.

Infections that are associated with medical devices are a primary concern, as the biofilms that the bacteria form have an enhanced resistance to antibiotics.

Co-author of the research Professor Howard Stone, from Princeton University, said: "We have shown that Staphylococcus aureus can create slimy, thread-like biofilm streamers in environments that mimic the physical and chemical conditions of medical devices such as stents and catheters.

"By studying the morphologies and growth dynamics of the bacteria, we believe there is potential to develop novel methods that prevent diseases associated with this notorious pathogen."

In their study, Professor Stone and colleagues investigated how surface geometry, surface chemistry, and fluid flow affected the formation of streamers.

They examined four strains of Staphylococcus aureus by staining the cells with fluorescent dyes and taking high-resolution images as a flow was passed through the microfluidic structures, which contained curvy channels and multiple networks.

Their results showed that the flow of fluid through the structures was the major contributor to the shape of the biofilm streamers, as opposed to movements of the cells themselves, and that the biofilm streamers could form in a number of different complex environments, leading the researchers to believe that the streamers are ubiquitous in natural environments.

Compared to another common pathogen, Pseudomonas aeruginosa, which the researchers previously studied, Staphylococcus aureus formed and clogged up the channels much more quickly.

"The different dynamics of biofilm formation may result from different mechanisms, and different flows of the biofilm matrix, which are research directions we are currently pursuing," Professor Stone continued.

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The above story is based on materials provided by Institute of Physics . Note: Materials may be edited for content and length.

How Do You Block a Penalty Kick?

In today’s World Cup match between Brazil and Chile, it came down to penalty kicks. If neither team is ahead after two extra 15 minute time period, each team gets 5 penalty kicks. The team that scores the most of these 5 wins the match. Brazil won. Oh, was that a spoiler? No, it can’t be. Surely you know the score by now.

It seems pretty tough to stop one of these penalty kicks. How about a quick analysis?

How Fast is a Kick?

Of course, there isn’t a perfect side angle view of these penalty kicks. This means that it would be difficult to get a trajectory of the ball. However, I don’t really need that. I only need an estimate of the speed. Since I know the ball starts 12 yards from the goal, I can find the velocity by measuring the time of flight. Yes, these things go pretty fast. I find it’s easiest to use Tracker Video Analysis just to get the start and end time of the kick.

Using this method, I get the following speeds. Note that this is just an estimate because if the ball is kicked at an angle it actually goes farther to goal line than just 12 yards.

  • Kick 1: 24.94 m/s

  • Kick 2: 39.18 m/s

  • Kick 3: 17.9 m/s

  • Kick 4: 30.47 m/s

  • Kick 5: 39.18 m/s

  • Kick 6: 30.47 m/s

  • Kick 7: 34.28 m/s

  • Kick 8: 24.42 m/s

  • Kick 9: 24.93 m/s

  • Kick 10: 30.47 m/s

This gives an average kick speed of about 30 m/s. Really, the video I used was mostly on the crappy side so that these numbers cold be off.

Reaction of a Keeper

Really, not the reaction. I am thinking of the acceleration of a keeper (goalie). Here is a plot of the position of a keeper during a kick. In this case, he starts his move 0.2 seconds before the ball is actually kicked.

Data Tool

He seems to have a fairly constant acceleration of about 5.26 m/s2. So, if he starts in the center of the goal, how long will it take him to reach one side of the goal? A goal is 7.32 meters wide so this means he must travel 3.66 meters. Since he starts from a speed of zero, I can jsut use one of the kinematic equations.

La te xi t 1

With a final x position of 3.66 meters and an acceleration of 5.26 m/s2, I get a time of 1.18 seconds.

If I used a distance of 12 yards for a ball with the lowest speed of 17.9 m/s, that gives a time of travel at just 0.61 seconds.

How to Block a Kick

Now for the important point. How do you stop these kicks? The answer is simple: guess. Guess which way the ball is going to be kicked and move that way after the kicker has already determined his kick direction. It’s just that simple.

Oh, but what if the keeper had a greater acceleration? Let’s double it and make it 10.52 m/s2. This would still give a time of 0.83 seconds to get to the side of the goal. Not good enough.

But maybe guessing would work. According to this site, 85% of the penalty kicks are successful goals. So, if you guess and get just one block you could consider yourself (as a keeper) successful.

Evolution Book For Young Children: Grandmother Fish [Greg Laden's Blog]

In a previous life (of mine) my father-in-law, an evolutionary biologist, kept an oil painting of a fish on the wall of the living room. At every chance he would point out, to visitors or to anyone else if there were no visitors, that he kept a portrait of his distant ancestor hanging in a prominent location, pointing to the oil painting. It was funny even the third or fourth time. It isn’t really true, of course, that this was his ancestor. It was a bass, more recently evolved to its present form than humans, I suspect. But it is true that the last common ancestor of humans and fish was a lot more like a fish than like a human.

I know it is hard to find good books about evolution for kids, and it is even harder to find a book for really young kids. A book needs to be written for the audience, engaging, entertaining, and all that — it needs to be a good book — before it can also teach something. A book that teaches but sucks as a book doesn’t really teach much.

Recently, Jonathan Tweet of Seattle Washington sent me a draft of a book he was working on that is such a thing, a good book that teaches about evolution and targeted to young kids. He had sent the book around to a number of experts for two reasons. First, he wanted to make sure he wasn’t saying anything wrong vis-a-vis evolution. Second, he wanted to make sure he got his facts straight at another level so he could provide useful and accurate footnotes for the adults who might read the book for the kids. I had a comment or two, but really, he already had his ducks in a row and the book, with the notes, was in good shape. It had evolved, as a project, very nicely.

The book is: Grandmother Fish: a child’s first book of evolution. From his blurb:

Grandmother Fish is the first book to teach evolution to preschoolers. While listening to the story, the child mimics the motions and sounds of our ancestors, such as wiggling like a fish or hooting like an ape. Like magic, evolution becomes fun, accessible, and personal. Grandmother Fish will be a full-size (10 x 8), full-color, 32-page, hardback book full of appealing animal illustrations, perfect for your bookshelf. US publishers consider evolution to be too “hot” a topic for children, but with your help we can make this book happen ourselves.

Jonathan made a kick-starter to raise 12,000 to produce the book. He’s already reached that goal and is now edging towards the stretch goal of $20K.

You can visit the kickstarter site HERE. You can download an early draft of the book. Personally, I plan to make this a Christmas gift for several friends and relatives who have kids the right age, assuming it is available by then. You can also see a several videos by the author and illustrator.

You can go to the Kickstarter site now and invest in any one of several different products that will be sent to you.

You may know of Tweet’s other work on Dungeons & Dragons and similar projects.

I recommend the book, strongly. Thank you for writing it, Jonathan.

My zombie story [Pharyngula]

The zombie plague was a dud. When the first cases emerged, scattered around the globe, everyone knew exactly how to put them down: destroy the brain. The world had been so saturated with zombie comic books, zombie TV shows, zombie novels, and zombie movies in the greatest, if unplanned, public health information program ever, that the responses to the outbreaks was always swift and thorough. In fact, most civilian casualties were caused not by the zombies themselves, but by the way everyone had been conditioned by the media to respond to lumbering, moaning, disheveled humanoid forms with instant and brutal violence.

The death of a few dead homeless, mentally ill people, or others who just weren’t perky morning people, was considered a small price to pay for the ruthless efficiency with which the zombie problem was eradicated. There was talk of giving George Romero a Nobel peace prize; Time Magazine ran an issue with “Heroic Humanity” featured on the cover; the public acquired a cocky attitude and brain-smashing weapons of destruction became the hot new fashion accessory. The horror of the worst catastrophe we could imagine, the emergence of an evil twin of our species, corrupt and mindlessly destructive, had been met and dismissed with arrogant ease.

An important lesson was not learned. Zombies were our mirror image, big animals that were short-sighted and heedlessly destructive, and we had easily wiped them out…because big animals are delicate, fragile things with a limited population size, requiring immense amounts of cooperation to survive. Our pride was undeserved. We had discovered how easy it was to kill small groups of bipedal primates. Nature laughed at our trivial accomplishment.

The same plague had been burning through rat populations. Every city, every small town garbage dump, every ship, had been boiling with upheaval in the darkness as the zombie rats spread the infection everywhere. The rats were numerous, and it took three months for the disease to consume them…and then the undead rodents slithered upwards, looking for a new food source. They were ubiquitous and silent and sneaky, and found ways into bedrooms at night, where the smug humans lay with shotguns and pistols and hammers for demolishing large-skulled stupid targets, their doors safely (they thought) barred against 70 kilogram intruders. The little, mindless zombie rats scurried forward, and gnawed.

Homo sapiens was extinct within a year.

(I had this idea for a great and accurate zombie novel that would reveal the true message of the zombie fad — come on, look at yourselves, it’s all about rapacious humans with no restraint — and would also make me millions of dollars. I got up this morning all excited and rushed to start writing it, and then I discovered that I could tell the whole story in five paragraphs. Oops. Is there much of a market for one-page novels? With a totally depressing conclusion?)

Outlander TV Adaptation Won’t Shy Away From Spanking

Diana Gabaldon

Elenna Loughlin

Diana Gabaldon is the author of the wildly popular Outlander series, which tells the story of Claire Randall, a World War II-era nurse who finds herself transported to 18th-century Scotland, where she falls in love with a rugged highlander named Jamie. Battlestar Galactica’ s Ronald Moore will bring the series to television in August, and Gabaldon promises that the show will not tone down any of the racy content of the first novel, which includes the hero whipping the heroine with his swordbelt, and a torture scene featuring what she calls “non-consensual buggery.”

“If it’s in the book, we’ll film it the way it is in the book,” Gabaldon says in Episode 112 of the Geek’s Guide to the Galaxy podcast. “I couldn’t ask for better than that.”

The show is sure to raise eyebrows in much the same way as the wildly popular Game of Thrones , based on the book series by Gabaldon’s friend and fellow Santa Fe resident George R. R. Martin. That’s no accident. The success of Game of Thrones has sent studios scrambling to find another big fantasy book series with adult themes to adapt for TV. Still, as faithful as Outlander promises to be, fans of the books will have to accept that some changes will be made. Gabaldon has urged them to relax about small differences, such as Claire’s eyes being blue not brown.

“It’s the 18th century,” she says. “The lighting is such that 90 percent of the time you can’t even tell what color anybody’s eyes are.”

Listen to our complete interview with Gabaldon in Episode 112 of Geek’s Guide to the Galaxy (above). Then stick around after the interview as guest geeks John Joseph Adams, Christie Yant, and Wendy Wagner join host David Barr Kirtley to discuss Women Destroy Science Fiction , a special crowdfunded double issue of Lightspeed magazine written and edited entirely by women.

Diana Gabaldon on soldiers reading her books:

“The books are very popular with servicemen and women. A lot of them who are deployed to Iraq or Afghanistan will go to a bookstore and pick up the biggest book they can find for the flight, which is often enough one of mine, and when they get to the other side they call their families and say, ‘Send the rest of the series.’ They empathize with Jamie Fraser, you know, he’s a warrior, as they are, and he’s fighting for the same things they are. … But beyond that they are surprisingly interested and involved in the relationships of the main characters. One of them said to me in a letter, you know, you get a weekly phone call, and usually half of it is taken up with just domestic inquiries … and it’s very stilted, and by the time you’re relaxed with each other again the phone call is over, so it’s kind of unsatisfying. He said with the books to talk about you can say, ‘Oh, I’m up to chapter so-and-so. Have you read this yet?’ And if she has then you can say, ‘Well, would you do what she did?’ And the conversation takes place on a much more immediately intimate level, because they can discuss their own relationship in the safe context of the relationship of these characters.”

Diana Gabaldon on historical fiction:

“Cultural concepts are one of the most fascinating things about historical fiction. There’s always a temptation, I think, among some historical writers to shade things toward the modern point of view. You know, they won’t show someone doing something that would have been perfectly normal for the time but that is considered reprehensible today. For instance women drinking alcohol while pregnant. I get a lot of people being just appalled that Claire drinks wine while she’s pregnant, and I’m saying, ‘It was 1743. Everyone drank wine regardless.’ And in fact while Claire comes from 1945, there was absolutely no idea in anyone’s head that drinking alcohol would cause any problems whatsoever. The thought that you ought not to drink while pregnant came much, much later. In fact, I had my first child in 1982, and I was still told by nurses and so forth, ‘Have a glass of wine with dinner. It’ll help you relax.’”

Women Destroy Science Fiction Panel

Christie Yant on reading J.R.R. Tolkien as a girl:

“I read Tolkien when I was 11. I read The Hobbit and the trilogy on a road trip with my family. I identified with the nonhumans in those books, and it never occurred to me why that was. It’s because none of the nonhumans were women, and I felt very nonhuman a lot of the time. … It never occurred to me that I wasn’t reading about girls. It never occurred to me that I wasn’t represented, because I didn’t think I was supposed to be. I was supposed to want to be a boy. … It’s really the internet that’s allowed me to connect with ideas that freed me from what I and others call ‘girl hate.’ I was a girl and a woman who didn’t want to be one, because I believed that we were inferior. I didn’t know the language for feminism. I certainly had never heard of Joanna Russ. I had never encountered these ideas before, and again, I came to it so late in life, I just feel kind of bad for that tiny Christie who would rather have been a hobbit than a person.”

Wendy Wagner on Women Destroy Science Fiction:

“Some of these essays just make you want to go out and be like, ‘If the patriarchy had a physical embodiment, I would break the patriarchy’s kneecaps today.’ … I really wanted to make the nonfiction be about inspiring and empowering women to read and write science fiction, because I love science fiction, it’s the bulk of what I write, and I just want everybody to feel inspired by it and as welcome within it as I want to be welcome. … There’s this essay by Nisi Shawl which is about how to help women writers. It’s just chock full of resources and encouragement and support, and it’s exactly what I wish someone had handed me when I was 19 and thinking, ‘Oh, I’m never going to be a great writer.’ … There’s a great reading list that Stina Leicht put together which is part personal essay about how science fiction helped her as a young person as well as recommendations of great feminist work. … I think there’s just so much positive energy in the reading list. I’m glad I got to put it together.”