Most of us assume that by the time food arrives at the grocery store, it’s been checked for any chemicals that might harm us. That’s not necessarily the case: food manufacturers and federal employees test for some known culprits in some foods, but the search isn’t exhaustive, especially when it comes to imported items. Recently, scientists working with ABC News checked to see whether imported farmed shrimp bought from grocery stores had any potentially dangerous antibiotic residue, left over from the antibiotic-filled ponds in which they are raised. It turns out, a few of them did.
Out of 30 samples taken from grocery stores around the US, 3 turned up positive on tests for antibiotics that are banned from food for health reasons. Two of the samples, one imported from Thailand and one from India, had levels of carcinogenic antibiotic nitrofuranzone that were nearly 30 times higher than the amount allowed by the FDA. The other antibiotics the team discovered were enroflaxin, part of a class of compounds that can cause severe reactions in people and promote the growth of drug-resistant bacteria, and chloramphenicol, an antibiotic that is also a suspected carcinogen.
For frequent readers of this blog and Carl Zimmer’s The Loom, the bacterium Clostridium difficile may ring a bell. It’s a germ that can cause devastating, intractable gut infections, and is one of the reasons behind the recent development of fecal transplants to try to give the patient healthy gut bacteria to fight back with. C. difficile is on more people’s radar these days, and with good reason. A new Centers for Disease Control report shows that infections from C. difficile and another gut pathogen, norovirus, have grown more common and much more lethal in the last fifteen years. In 2007, they killed more than double the people they’d killed ten years before, jumping from 7,000 to 17,000. Most of those who died were elderly.
The rise of antibiotic-resistant bacteria has got many experts predicting a future in which currently tractable diseases, like tuberculosis, became untreatable again. The popularity of modern antibiotics, ironically, is what is leading to their downfall: antibiotics in consumer products, like soaps, as well as the excessive use of antibiotics by people who have no bacterial infections, help select for strains of bacteria that don’t respond to drugs. Factory-farmed livestock, which receive tremendous doses of antibiotics in their feed, are also a likely breeding ground for resistant bacteria that could potentially infect humans.
Proponents of factory farming have scoffed at such claims [pdf], but now, scientists have provided definitive evidence that this happens: through genetic analysis, they found that a strain of MRSA, already resistant to one family of drugs, had hopped from people to farmed pigs, acquired resistance to another antibiotic being fed to the pigs, and then leapt back into humans, taking its new resistance with it. That strain, called MRSA ST398 or CC398, is now causing 1 out of 4 cases of MRSA in some regions of the Netherlands [pdf], where it arose, and it has also been found across the Atlantic in nearly half of the meat in US commerce. After this strain arose in 2004, the European Union began a ban the use of antibiotics in livestock feed. In the United States, however, where most of the antibiotics in circulation are being used in farming, no such regulation exists.
Image courtesy of wattpublishing / flickr
Bacteria that have evolved defenses against antibiotics are something of a disaster waiting to happen. Whenever a new drug-resistant strain, or a gene that confers resistance, crops up in a new place—as when the NDM-1 gene, which confers resistant to up to 14 drugs, showed up in drinking water in New Delhi—it’s another nail in coffin of a world in which we can heal nearly everything. Scientists are looking into how to get around that resistance, though, and there are some hopeful headlines now and then, including a recent study from researchers at North Carolina State University in which they identified a molecule that can boost the efficacy of two antibiotics against bacteria 16-fold.
The molecule, which the researchers found by testing about 50 candidates to see if they could reduce the number of NDM-1-carrying K. pneumoniae by a significant amount, doesn’t have any antimicrobial properties of its own. It’s an adjuvant, which means it has to be applied in tandem with another drug to have any effect—in this case, the antibiotics carbapenem and cephalosporin. The researchers checked a couple of different ways that it could be working, and found that it was making bacterial membranes easier for the drug to get through, but not enough to account for all of its surprising strength: it lowered by 16 times the amount of antibiotic required to knock the bacteria on their behinds. That’s handy, because taking massive amounts of antibiotics—enough to overwhelm the defenses of resistant bacteria—can be hazardous to your health, and if adding in this adjuvant tips the scales so that safe amounts can knock out infections, that’s pretty neat.
As an antibiotic sidekick, it’s definitely still on the mysterious side. But the team writes that they are looking further into its mechanism, so stay tuned.
Image courtesy of Muriel Gottrop / Wikimedia Commons
What’s the News: Gonorrhea, known in earlier days as the clap, has generally been considered the training wheels of STDs: a young sailor on his first tour of duty would feel a slight burning while urination, get a big shot of penicillin in the infirmary, learn the error of his ways, and start carrying a condom in his wallet.
But after years of warning that drug resistance in STDs was on the way, scientists have now found a strain of the bacterium that stands up to the usual antibiotic treatments, sparking fears that the days of easily banished gonorrhea are over.
What’s the News: Going undercover can require some sacrifices–burning off your fingerprints, for instance, a la Gattaca. It’s the same story with bacteria: they can slip below antibiotics’ radar without any mutations, but only using an elaborate system of self-sabotage. A new study reveals the workings of this biochemical disguise.
What’s the News: Scientists are using nanoparticles to develop ways to fight bacteria that are resistant to conventional antibiotics. These tiny drugs physically punch holes through bacteria instead of killing them chemically, which means that they could be especially effective on antibiotic-resistant bacteria strains like the dangerous methicillin-resistant Staphylococcus aureus (MRSA). “The applications are going to be very diverse, whether we’re talking about wound healing or dressing, skin infection, and quite possibly injections into the bloodstream,” James Hedrick, master inventor at IBM Almaden Research Center in San Jose, California, told Popular Science.