In the years I’ve spent writing about infectious diseases I can only think of a handful that have made me squirm: Guinea worm disease, which involves painful extractions of long worms from the human body (blech); Naegleria fowleri, the brain-eating amoeba (pretty self-explanatory); Ebola (because, well, it’s Ebola); and Staph A (full name, Staphylococcus aureus).
Like most Americans, I’m privileged to live in an area where certain diseases are not as prevalent as others. (Human health is incredibly intertwined with socioeconomic status and human rights—but that’s a post for another time.) Being so fortunate, there are some diseases that just are not part of my everyday reality. And while it’s pretty unlikely that I’ll contract Guinea worm disease anytime soon, Staph A could easily become a very damaging part of my—and your—life.
Staph A is one pesky pathogen. It seems to be everywhere, too: It’s one of the most common causes of hospital-related and community-acquired infections (meaning those passed from person to person), according to the New England Journal of Medicine, and it can cause anything from a pimple to sepsis (a serious blood infection that can lead to organ failure and death). Between 25 and 30 percent of people actually carry Staph A on their skin or in their nasal passages, without being harmed.
But Staph A can be incredibly harmful—if it’s carrying the right genes. The genes that make up a Staphylococcus bacterium determine whether or not it will secrete an enzyme, a protein, or a toxin that will cause someone to become ill. Gastroenteritis, Toxic Shock Syndrome, and necrotizing pneumonia are all associated with toxins secreted by Staph A.
It’s becoming clear that Staph A is a threat to people even when it’s not resistant to antibiotics. But since this series is about superbugs—or bacteria that are resistant to a growing number of antibiotics typically used to treat them—we’re going to cover two superbugs in particular: methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Staphylococcus aureus (VRSA).
The bacteria that were killed off when Alexander Fleming accidentally discovered penicillin were Staphylococcus aureus. Back then, penicillin was an excellent option for stopping Staph A infections. But by 1944—just as penicillin was being produced en masse—William Kirby published the first evidence of penicillin-resistant Staphylococcus aureus. By the 1970s, studies were already showing a high prevalence of Staph A that couldn't be stopped with penicillin in hospitals and communities around the U.S., according to the Centers for Disease Control (CDC).
Penicillin, like carbapenems (another type of antibiotic), is what’s known as a beta-lactam antibiotic. Penicillin, though, differs from carbapenems in that it typically treats Gram-positive bacteria (like Staph A) rather than Gram-negative bacteria. After Staph A began showing resistance to penicillin, doctors switched and started using the antibiotics vancomycin and methicillin to combat these infections. Vancomycin is typically seen as a last-resort drug because of both its power and toxicity.
By the 1980s, the CDC was collecting data showing that the bugs were winning against methicillin, too, as more cases of methicillin-resistant Staph A (MRSA) turned up in large, urban medical centers. It was a trend that continued into the ‘90s and started affecting smaller hospitals, too. In 1997, the New England Journal of Medicine revealed two infections of Staph A that weren’t as vulnerable to vancomycin, the "last resort" drug. You can guess the rest: MRSA and VRSA are now quite serious problems.
It’s worth noting that not everyone is equally at risk for MRSA and VRSA infections. Staph A is predominantly thought of as a hospital-acquired infection, though person-to-person infections outside hospitals have jumped over the years and should be taken seriously. The CDC says that people with chronic diseases like diabetes, cancer, and lung disease are particularly at risk. In hospitals, ICU patients; those requiring long-term hospital care; and especially patients on ventilators or using catheters for long periods of time are at an increased risk for Staph A.
So where do we go from here to fight this superbug? That’s not clear. Some agencies report that MRSA cases have declined over the past few years. A recent study in PLOS One suggests that a protein found in human breast milk could help reverse antibiotic resistance—including in penicillin- and methicillin-resistant Staphylococcus aureaus. But there’s also so little federal funding for MRSA research right now that it’s not likely we’ll crack the code of finding a new-and-improved antibiotic to fight MRSA anytime soon. Wired reporter Maryn McKenna quotes Dr. Eli Perencevich and a World HAI Report, which notes that for every AIDS death there is $69,000 awarded in federal grants. For MRSA, that amount is just $570. And yet, according to McKenna, there are more MRSA deaths in the U.S. every year than from HIV, pneumococcal, meningococcal, and flu deaths combined.
For every death from MRSA we spend $570 on research. Compare that to $69,000 for every AIDS death, even though MRSA deaths far outnumber those from AIDS.
There’s also the issue of MRSA transmission from humans to animals, and from animals to humans. A study published in EMBO Molecular Medicine in early 2013 provides evidence of MRSA transmission from livestock to humans. Perhaps it’s time to take the use of antibiotics in livestock a little more seriously?
So let’s say the worst-case scenario happens and you are infected with MRSA. What happens—is there anything doctors can use to fight this powerful bacterial infection? There are a few drugs that remain effective against MRSA, and one of them is vancomycin. However—and this is key—the more we use vancomycin, the more vancomycin resistance we may see. If this drug-of-last-resort became useless, we’d have to treat with other super-strong drugs, like daptomycin. And, of course, we’d again be running the risk of more antibiotic resistance. Right now, cases of VRSA, thankfully, remain low. As of 2010, the CDC reported just 13 cases in the U.S. To keep these numbers down, we need to focus on limiting the spread of MRSA—and the use of vancomycin.
At the top of most lists of how to control these infections is hand hygiene (i.e., really good hand-washing). If you have a mild Staph A skin infection—MRSA or not—don’t try to treat it yourself; see a medical professional. The CDC also recommends rapid reporting of MRSA and increasing education and awareness so more people are aware of these infections and how to protect themselves against them.
--By Anna Tomasulo
Were you aware of MRSA infections? Do you know anyone who’s been infected? If so, how they contract MRSA or VRSA?