Biologist With A Twist: Dr. Carin Bondar

Are Headlines Hogwash? Part III


Posted on July 13th, by Carin in Carin's Paper Pick 'o the Week. No Comments

Blackburn, J., Mitchell, M., Blackburn, M., Curtis, A., & Thompson, B. (2010). Evidence of Antibiotic Resistance in Free-Swimming, Top-Level Marine Predatory Fishes Journal of Zoo and Wildlife Medicine, 41 (1), 7-16 DOI: 10.1638/2007-0061.1
ResearchBlogging.org

This week’s installment of ‘Are Headlines Hogwash’ brings us to an article from Discovery News this past June.  Here’s the headline:

ANTIBIOTICS BREEDING ‘SUPER BUGS’ IN SHARKS, FISH

I should also add that the first line of the article reads:

“It’s one of the scariest things about modern society — ever since we declared war on bacteria with the widespread use of penicillin in the 1940s, microbes have been adapting, gaining resistance to our drugs, coming back stronger and more vicious than before…”

Superbugs!  Antibiotic Resistance!  Stop the Presses! No wait…start the presses! Uh – hold on… is there really any truth to this dire headline?

She says:   There’s a shred of truth to it.

The research described here did indeed find evidence of bacterial resistance.  Here’s the rundown:  scientists wiped the bums of several large fish species including seven sharks and one teleost, and isolated the bacteria that were found.  This was done at six separate (widespread) locations.  The bacteria were characterized by their gram-stain morphology, and then tested against 13 different drugs for possible resistance.

Antibiotic resistant bacteria were found in all species, and at all sites, for at least one of the drugs tested.  *However, the authors note that when gram stain morphology of the bacteria is included in the analysis the incidence of resistance decreases dramatically.  This is because a gram negative bacteria will OBVIOUSLY be resistant to an antibiotic designed for a gram positive one.

The authors state that “Further characterization of the bacteria for the presence of resistance geneswould have been beneficial but were beyond theresources and scope of this study.”
Ok fair enough.  It doesn’t negate the fact that there are resistant bacteria out there…but it does encourage a wave of caution in interpreting the headline as truth about an imminent threat of superbugs from the ocean.  Resistance?  Yes.  Superbugs akin to those found in hospitals that result in multiple fatalities?  No.  Nothing in this research paper speaks to that kind of situation.  Perhaps in the future this is a possibility, but not here, not now.

He Says: I haven’t even read the article yet and I’m already a bit annoyed.

Sharks are, last I looked, fishes. In essence, the headline says, “Antibiotics breeding super bugs in fish and, by the way, did we mention the fish?”

Someone’s a little too eager for Shark Week, I guess.

Humans have used a lot of antibiotics over the last few decades, and bacteria are responding. Many antibiotics that used to work only work occasionally now. That’s a problem in places where there are lots of humans and human bacteria, but this study tries to look at how far the problem has spread.

The paper shows there are drug-resistant bacteria (the ‘super bugs’ of the headline). But the headline seems pretty definite that those bacteria have that resistance because of human use of antibiotics. Here, the evidence marshaled by Blackburn and company is not as convincing. Antibiotics are not just artificial products; micro-organisms make them to compete with each other. So it’s possible that at least some of the resistance they’re seeing to drugs is not related to human antibiotic use.

To its credit, the main text of the article gets this right, giving the reader some of the subtleties that the headline does not.

To test whether the drug-resistance is due to human antibiotics use, you’d want bacterial samples from these marine populations starting about… 50 years ago. You would expect to see an ever-increasing escalation: as more drugs get used, more and more drug resistant bacteria show up.

That sort of information might not exist, but you might be able to start tracking resistance now and seeing what happens to the bacterial populations when a completely new antibiotic hits the market.

The full news article is better than the headline. I can almost forgive that the main text also makes the “sharks and fish” gaffe.

Some Bonus Fun Comments:

ZF: Biology can involve a lot of a–holes. CB: figuratively and literally!  My entire Master’s thesis was about snail a– holes…an important structure with respect to the evolution of development, but I digress…

ZF: Strictly speaking, some fishes don’t have those: instead they have a cloaca, a joint opening for digestion and reproduction. (Trivia: “Cloaca” is comedian Robin William’s favourite word.)

ZF: But the fact is, Blackburn and company got their bacterial samples from the back end of a bunch of the top predators in the ocean, and therefore, the world.  CB:  I wasn’t kidding when I said that scientists went out wiped the bums of a few (rather insulted?) sharks!

ZF: I’d like you to consider that for a second. Consider the kind of person it takes to get a bacterial sample from a bull shark. The words “bull” and “shark” alone kind of freak me out. I’m not sure I’d want to be in that close contact with an animal that has both those words in its name. Remember that if anyone ever suggests that scientists are wusses.  CB: There’s something to be said for wiping snail and/or crayfish bums instead.

CB: Zen, if we ever tire of biology we should definitely hit the road with our stand-up routine!  Seinfeld look out!





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