It's a bird! It's a plane! It's superbug!
It seems like MRSA is everywhere lately, but how does a mild-mannered bacterium become an antibiotic-deflecting superbug? Where did it come from? Is there any kryptonite to defeat it?
MRSA stands for Methicillin-Resistant Staphylococcus Aureus, but let's forget about the "Methicillin-Resistant" for now. Staphylococcus aureus, or Staph, is a Gram-positive spherical bacterium that appears in clusters. It's considered "Gram-positive" because unlike some other bacteria, Staph has a peptidoglycan cell wall that absorbs Gram stain, turning it blue-violet.
In some people, Staph can colonize the nasal passages and even the skin. Often, this isn't a problem, but under certain circumstances, Staph can multiply, produce enterotoxins, and invade cells and structures, causing anything from food poisioning and skin infections to pneumonia and toxic shock syndrome. This page is a great resource to learn more about bacteriology and Staph's pathogenicity.
It turns out that the peptidoglycan cell wall is important. It protects the bacterium's internal machinery from the outside world. Methicillin, a beta-lactam antibiotic (named for its chemical structure), inhibits enzymes that are crucial in cell wall synthesis. By inactivating the enzymes, methicillin effectively turns the bacterium's cell wall into Swiss cheese, causing it to die.
So where does the "Methicillin-Resistant" fit in? Think survival of the fittest. Like every other organism in the world, bacteria evolve, albeit at a faster pace. Where it take humans about 25 years to reproduce, it only takes bacteria about 20 minutes. Each time bacteria reproduce, there's a chance for a mutation that might have no effect, be detrimental, or convey an advantage. In a certain way, antibiotics "drive" mutations toward one direction.
Imagine trillions of bacteria all over the world, constantly reproducing. In the presence of an antibiotic, many will stop reproducing and die. However, a random genetic difference that protects a bacterium from the antibiotic in some way would provide it with a survival advantage. These bacteria would survive and reproduce, and in turn, the "fittest" bacteria in each new generation would survive to reproduce again. By exposing bacteria to antibiotics repeatedly, we inadvertently select for the bacteria with the strongest resistance over and over again, until the bacteria becomes "immune" to the antibiotic.
Some bacteria have evolved to produce an enzyme that actually breaks down the antibiotic before it can affect the cell wall. Other bacteria, like MRSA, have altered proteins that still function in cell wall synthesis, but no longer bind methicillin.
Are we doomed? Not quite. Just because methicillin doesn't work against MRSA, doesn't mean that other drugs like vancomycin (some resistance reported), linezolid (Zyvox), daptomycin (Cubicin) and tigecycline (Tygacil) are ineffective. Although free registration is required, this Medscape article is a great way to learn more about the clinical treatment of MRSA.
They key to preventing antibiotic resistance is prescribing/using antibiotics judiciously. Indiscriminate use is what got us into this mess in the first place. There are also steps you can take to decrease your chances of contracting MRSA. Check out these guidelines from the CDC. In the meantime, go wash your hands!
MRSA stands for Methicillin-Resistant Staphylococcus Aureus, but let's forget about the "Methicillin-Resistant" for now. Staphylococcus aureus, or Staph, is a Gram-positive spherical bacterium that appears in clusters. It's considered "Gram-positive" because unlike some other bacteria, Staph has a peptidoglycan cell wall that absorbs Gram stain, turning it blue-violet.
In some people, Staph can colonize the nasal passages and even the skin. Often, this isn't a problem, but under certain circumstances, Staph can multiply, produce enterotoxins, and invade cells and structures, causing anything from food poisioning and skin infections to pneumonia and toxic shock syndrome. This page is a great resource to learn more about bacteriology and Staph's pathogenicity.
It turns out that the peptidoglycan cell wall is important. It protects the bacterium's internal machinery from the outside world. Methicillin, a beta-lactam antibiotic (named for its chemical structure), inhibits enzymes that are crucial in cell wall synthesis. By inactivating the enzymes, methicillin effectively turns the bacterium's cell wall into Swiss cheese, causing it to die.
So where does the "Methicillin-Resistant" fit in? Think survival of the fittest. Like every other organism in the world, bacteria evolve, albeit at a faster pace. Where it take humans about 25 years to reproduce, it only takes bacteria about 20 minutes. Each time bacteria reproduce, there's a chance for a mutation that might have no effect, be detrimental, or convey an advantage. In a certain way, antibiotics "drive" mutations toward one direction.
Imagine trillions of bacteria all over the world, constantly reproducing. In the presence of an antibiotic, many will stop reproducing and die. However, a random genetic difference that protects a bacterium from the antibiotic in some way would provide it with a survival advantage. These bacteria would survive and reproduce, and in turn, the "fittest" bacteria in each new generation would survive to reproduce again. By exposing bacteria to antibiotics repeatedly, we inadvertently select for the bacteria with the strongest resistance over and over again, until the bacteria becomes "immune" to the antibiotic.
Some bacteria have evolved to produce an enzyme that actually breaks down the antibiotic before it can affect the cell wall. Other bacteria, like MRSA, have altered proteins that still function in cell wall synthesis, but no longer bind methicillin.
Are we doomed? Not quite. Just because methicillin doesn't work against MRSA, doesn't mean that other drugs like vancomycin (some resistance reported), linezolid (Zyvox), daptomycin (Cubicin) and tigecycline (Tygacil) are ineffective. Although free registration is required, this Medscape article is a great way to learn more about the clinical treatment of MRSA.
They key to preventing antibiotic resistance is prescribing/using antibiotics judiciously. Indiscriminate use is what got us into this mess in the first place. There are also steps you can take to decrease your chances of contracting MRSA. Check out these guidelines from the CDC. In the meantime, go wash your hands!
Tags: mrsa, aureus, infections, methicillin, resistance, staph, staphylococcus
Add a Comment
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Comment by Vincent J. Tamuzza, MD on February 28, 2009 at 5:21pm - I'm very sorry to hear about your daughter's condition. She should probably see an Immunologist or Infectious Disease specialist in a nearby city, like Madison or Milwaukee. Children's Hospital of Wisconsin might be a good option, since it is affiliated with a medical school, and academic institutions are usually the most up to date. Those types of specialists might be able to address why a child so young would have already suffered two bouts of MRSA, and what precautions you can take to prevent another infection. Her immune system should definitely be checked. Make sure you always tell any doctor who treats her that she has a history of MRSA infections. Any skin wounds that become infected should be cultured (swabbed and test). All my best to you and your family. Good luck.
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Comment by ameixner on February 28, 2009 at 2:15pm -
I have a one year old daughter who has had mrsa infections twice now in less than six months. The doctors keep putting her on antibiotics and this last time she got the infection they think she may be colonized with the mrsa. I cant seem to get my concerns addressed. I want to know that if she gets an open wound is she going to keep getting thes infections. She gets the cellulitis and the first time she got it we had to take her to a surgeon to have the absess drained in her groin. The er doc mis diagnosed my 6month old then with a wound or injury to her groin area. Do these doctors out there even know what they are looking for in regards to this superbug as they call it?
I want to know if my daughter will ever out grow this bacteria or is she going to have to suffer with this for the rest of her life. I do everything i am told with her and what i know from being a mother and she still has had problems with it. The second time she got the infection was after she got her vaccination shot. Some how the bacteria had gotten into the broken skin and caused the infection and cellulitis. Luckily i noticed soon enough that i brought her in and told the doc that she had had problems with mrsa before and that it was doing the same thing.
my daughter is a year and i want to be able to see her grow up without worrying about getting an infection everytime she falls or gets some kind of open wound.
Do you have any ideas on how i can help her from having mrsa reaccuring.
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Comment by Vincent J. Tamuzza, MD on April 26, 2008 at 1:05am
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I'm sorry about your recent diagnosis, Lesly. MRSA infections can be very frightening and confusing.
As I mentioned in my original post, many if not most people are colonized with plain old Staphylococcus Aureus. Most of the time, this does not cause any problems, unless certain conditions are met; bacterial overgrowth (diabetes), immunocompromised host (recent surgery, cancer, HIV), or self-inoculation (skin wound, unchanged tampon).
Healthcare workers, like everyone else, run the risk of carrying regular Staph, but because we come in contact with a large number of sick people who carry MRSA, the Staph we carry might be of the MRSA variety. Again, most of the time, this isn't a problem (for ourselves at least). The biggest concern would be when a healthcare worker carrying MRSA doesn't wash his/her hands and use gloves, especially when doing things like changing bandages. Also, even if we don't carry MRSA ourselves, without proper aseptic practices we could transfer MRSA (or even regular Staph) between patients.
Antibiotics are usually reserved for active MRSA infections (like cellulitis or an abscess). As previously mentioned, even though methicillin does not work, there are still other antibiotics that do. These antibiotics, however, probably cannot completely clear an active carrier by destroying every single MRSA bacterium in the nose or on the surface of the skin. Plus, as a healthcare worker, you'd just be prone to "catching" it again and returning to a carrier state.
The best thing to do as a healthcare worker is to wash your hands both before and after treating a patient, to always follow universal precautions, and to use MRSA precautions (gown, gloves, mask) when treating a patient with a known MRSA infection.
For everyone else: wash your hands often, launder clothes, towels and linens frequently, and take proper precautions in communal settings (wipe down gym equipment, avoid touching shower walls).
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Comment by Lesly on April 14, 2008 at 2:17pm -
Great resources, Vinnie, and great timing - I just found out last week that I'm apparently an active carrier of MRSA (most probably contracted at the hospital where I work) and have been in and out of the doctor's offices lately discussing treatment options.
It's hard to miss all the news stories going out about the MRSA epidemic, and it's even more alarming to hear that it's spreading throughout the medical community via infected health care providers.
But, honestly, I've found this whole MRSA thing really confusing and I've had so many questions: If it's antibiotic-resistant, why do I have to take another antibiotic for treatment? Why are so many health care workers infected with it? Why aren't they on treatments, too, if they're around sick people?
I was really surprised to find out from the number of physicians that I've seen in the last week that other than washing my hands more frequently, there was little else I needed to do to resume working with patients. Several physicians that I spoke to said that it was actually quite common and, unless I was in contact with someone who was severely immuno-compromised, I needn't worry about infecting others.
With all the hype about MRSA in the media, I guess I thought it would be a bigger deal. Anyone else have any thoughts about MRSA from a public health standpoint?
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Comment by Usha on April 12, 2008 at 12:35am -
In the meantime, go wash your hands!
Just make sure that your soap isn't an antibacterial one!!
The indiscriminate use of antibacterials like triclosan in various household products is part of the problem. Here's a good article from the CDC that talks about the use of triclosan and the development of resistance.
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Comment by Vincent J. Tamuzza, MD on April 9, 2008 at 7:58pm
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I'm so sorry, Jolyn! I don't know how I missed it, both in your post and in the website you referred to. Funny enough, most of my comments are still applicable. I found even less on grapefruit seed extract, except this Wikipedia entry. Actually, grapefruit seed extract would give me even more pause then grape seed extract. Grapefruit juice is a notorious inhibitor of the cytochrome p450 enzymatic pathway in drug metabolism, often raising the level of medication in the blood. This fact might have prompted the notion that grapefruit seed extract has antimicrobial activity, but I don't know for sure. Taking grapefruit seed extract with other medications could be dangerous, and taking grapefruit seed extract on its own could be ineffective. To learn more about grapefruit-drug interactions, click here.
Thanks Jolyn. We've touched on several topics today!
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Comment by Jolyn on April 9, 2008 at 7:00pm - I had the same confusion when my friend told me about it. I was referring to grapefruit seed extract, not grape seed extract. Here's more info on it.
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Comment by Vincent J. Tamuzza, MD on April 9, 2008 at 3:46pm
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Hi Jolyn. Thanks for your comment and questions. Although I can't comment on your friend's condition specifically, since I don't know exactly what ailment he was suffering, I'd like to address some topics you brought up.
I don't see a problem using antibiotics when warranted, as in the case of a diagnosed or proven bacterial infection. Generally, if an antibiotic has been shown to be effective in treating a particular condition, I would go with the antibiotic over a "natural" remedy to remove the infection from the body in a timely manner. Antibiotics, however, should not be given out like candy to anyone and everyone who has a cold (As you know, antibiotics are ineffective against viral infections, which most colds are).
As far as for grape seed extract specifically, the jury seems to still be out on that one. From what I found, it seems to have potential as a supplement for its antioxidant properties. Perhaps as more research is performed, grape seed will be incorporated into more therapies. As always, it should be taken under the supervision of a healthcare professional. More information on grape seed extract can be found here.
Lastly, the website you mentioned brings up the topic of acid-base equilibrium. Unfortunately, this immediately casts doubt on the quality of the information being provided. The blood must be strictly maintained between a pH of 7.35 and 7.45. Any slight deviation usually results in illness. Fortunately, the lungs and kidneys are exquisitely capable of handling the acid-base balance. This article from Quackwatch explains more about the acid-alkaline myth.
I think we should definitely be looking for more alternatives to the antibiotics we already have. I think it would be wise to explore plants and herbs for medical therapies either in their own nature state, a purified concentration, or for their incorporation into a pharmaceutical agent. After all, penicillin was isolated from mold. I'm actually an advocate for complementary and alternative medicine, but when given a choice, I'll always choose a tried and true method over an "experimental" one.
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Comment by Jolyn on April 9, 2008 at 1:18am
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Interesting blog here, Vinnie. I live in Mexico part of the year and, yes, we get infections all the time. Most gringos and Mexicans pick up bacterial infections and parasites, even drinking bottled water and purifying all vegetables and fruits, at some point. The common practice is to use antibiotics, especially Vermox (a one-month, three-month or one-year, tablet) which can be purchased over the counter here.
An amigo recently had a bacterial infection and to avoid yet another course of antibiotics, instead used grapefruit seed extract in liquid form and papaya tablets for one month. It seems like this treatment worked. There were no harmful bacteria left in the stool sample whereas there were prior to use of the grapefruit seed extract.
This web site says its good for viral, bacteria and fungal infections, plus parasites.
What do you think of grapefruit seed extract as an alternative to antibiotics? Is this really a safe and effective substitute for antibiotics?
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