Can a person be resistant to antibiotics?
December 27, 2009 1:04 AM   Subscribe

Can a person be resistant to antibiotics?

My girlfriend has an ear infection. Amoxicillin proved useless, so the doctor gave her Erythromycin. This helped but now, 10 days later, the infection is still here. She's going back for more tablets.

She told the doctor that Amoxicillin never worked when she had bouts of Pleurisy when younger, but the doctor wouldn't listen. When we returned to get a new dose of meds, he said he was surprised, and that the reason it usually doesn't work is allergy. That clearly isn't the case here.
posted by humblepigeon to Health & Fitness (15 answers total)
A bacterium can be resistant to antibiotics. I don't think it has anything to do with the person.

posted by esprit de l'escalier at 1:27 AM on December 27, 2009 [1 favorite]

No, a person cannot be 'resistant' to antibiotics. Antibiotics are designed to specifically target microbes. So we can administer antibiotics and wipe out huge numbers of microbes but cause no direct damage to the human host.

So no, people can't become resistant themselves to antibiotics, because antibiotics have no direct effect of our cells.

Microbial populations themselves can become resistant. When you use an antibiotic on a microbial population, you are selecting for any genes which confer resistance to the antibiotic. The rise of microbial resistance to antibiotics has been and still is a very powerful case study of natural selection in action. The profligate use of antibiotics (Neosporin: Every cut. Every time.) has led to widespread resistance to antibiotics.

But most antibiotic resistance is found concentrated in hospitals (and also feedlots) where Goldilocks conditions exist for the spread of resistance. Most people are not walking around with dangerous, multi-drug resistant strains of bacteria. Despite this, the average bacterium is probably much more resistant to antibiotics than was the case 60 years ago.

Your girlfriend's ear infection may be caused by a particularly resistant strain of microbe. Or the drugs administered so far may not be effective against this particular microbe - this happens too, and is slightly different from questions of antibiotic resistance. Some drugs are ineffective, some are effective, depending upon the specific microbe/s involved - because microbes differ widely in terms of physiology. Or your girlfriend's ear infection may be difficult to treat by antibiotics. I'm not educated enough to know for certain, and the doctor in question almost surely has a better idea than I do, but I do remember hearing about middle-ear infections being very stubborn, because antibiotics have a hard time reaching the site.

I would be highly surprised if there is a link between your girlfriend's stubborn earlier pleurisy and the current problem.
posted by schmichael at 1:53 AM on December 27, 2009 [11 favorites]

No, but they can be infected with an antibiotic resistant bacteria.
posted by delmoi at 2:59 AM on December 27, 2009 [1 favorite]

Maybe she metabolises the Amoxicillin faster than ordinary mortals? Probably not though, I've never heard of anything like that.
posted by atrazine at 3:13 AM on December 27, 2009

I've had inner ear infections where several courses of different antibiotics didn't relieve all symptoms and a tube was the only solution. Not sure if it was down to antibiotic resistant bacteria, or bad inner ear architecture that wouldn't let the mucous and lymph and whatnot drain out.
posted by Lentrohamsanin at 3:44 AM on December 27, 2009

Some people flush/process certain types of chemicals faster than others.

I've seen it with alcohol, various types of illegal and medical drugs - so is it possible for antibiotics?
It doesn't mean that the antibiotics aren't still targeting the bacteria, but maybe her body just mops it up faster than average, thus leaving it less time to do it's job?
posted by Elysum at 4:41 AM on December 27, 2009

Technically antibiotic resistance is defined by an organism not being affected by the antibiotic. What this means is that we're all resistant to the antibiotics used to treat bacterial infections in humans. We hope that the bacteria being targeted are not resistant.

Ah, semantics.

As stated by other mefites, it is more likely that the bacteria involved in your girlfriend's ear infection are resistant to the antibiotics she was given.
posted by sciencegeek at 5:39 AM on December 27, 2009

Does your girlfriend take the antibiotics on schedule and does she take the whole prescription, even if she starts feeling better part way through? I understand (IANAD) that patients who stop taking the drugs early because they feel better can get worse again.

Maybe even if a person isn't "resistant", s/he can have worse-than-typical luck with antibiotics if s/he doesn't understand how to take them correctly, or understands but still doesn't.
posted by fritley at 6:46 AM on December 27, 2009 [1 favorite]


If she was allergic to the antibiotics, she would have an allergic reaction, ranging from mild hay-fever symptoms to anaphylaxis. From my understanding of how antibiotics work, that would not limit their effectiveness against the infection, however.

How is the drug being administered? Pill or ear drops? If she has an ear infection, she may have a wax or fluid buildup that is somehow preventing the active chemicals in her bloodstream from effectively reaching the infection in her ear.

Perhaps your doctor can recommend a ear drop or something else that can help loosen any kind of buildup in the ear and help the drugs reach the infection site and also help your body expel the invaders?

If she is unlucky enough to have a strain of bacteria that is resistant to that common drug, doctors can prescribe more unusual anti-biotics that are typically not widely used, in order to prevent the kind of resistance that is becoming so common.
posted by kzin602 at 8:26 AM on December 27, 2009

No. But your body may harbor resistant strains of bacteria. If she has some, then the antibiotics probably never worked 100% and the bacteria keep coming back, with slightly more resistance too.
posted by chairface at 8:52 AM on December 27, 2009

Metabolism of antibiotics like penicillin takes more than a few hours and I doubt there is much variation between people, or at least not enough to make a difference. If some people could metabolize it very quickly then we would be seeing lots more resistant bacteria as that would be the same as not finishing your dose.

As far as being resistant, that seems unlikely. Her body isnt doing anything. The penicillin is doing all the work. When it comes into contact with bacteria it weakens the cell wall and the bacteria then either dies or later dies from bursting. The bacteria doesnt need her body to do this. Its action independent of the human. It doesnt stimulate your immune system or anything. Its simply a chemical poison that kills cells that you, hopefully, dont need.

If anything the bacteria is resistant.
posted by damn dirty ape at 9:21 AM on December 27, 2009

Ear infections are very difficult to treat; I've had a couple where the doc had to try three different antibiotics until finding the right one.

As others have said, it's the bacteria, not the host, that determines whether or not the antibiotic is effective.

The only thing I would look at, if it were me in this situation, is whether any of the supplements or OTC meds I was taking were affecting the potentiation of the antibiotic.

As for the pleurisy that wasn't affected by amoxicillin, your GF might have had a mycoplasma infection that was misdiagnosed; that happened to me once, and it was only after three rounds of antibiotics with no effect that they gave me something that specifically targeted mycoplasma and it cleared up within a week. Can't tell without a time machine and a doctor to go in it, though.
posted by Sidhedevil at 10:21 AM on December 27, 2009

Has your girlfriend ever had MRSA? Staph?

I ask because the last time I had it, they ran a panel on the sample and gave me a list of antibiotics that they said technically were no longer effective for infections in my body. Amoxicillin was one of those listed as ineffective.

It's probably not possible to do a full panel now, but IANAD, so this may be the culprit. According to my doctor, once you've had MRSA a few times, your body just doesn't react the same way to certain antibiotics; that's why they ran the panel for me, so I'd know in the future which antibiotics are still effective against infections in my system.

I am not sure if they specifically indicated that these drugs were ineffective against the MRSA itself, or against any infection I would contract in the future, but perhaps someone smarter than me could answer this part?

Regardless, I know that the one they told me would kill anything would be Cipro. Perhaps she could ask for that one specifically.
posted by Unicorn on the cob at 10:50 AM on December 27, 2009

If the filler in the antibiotic pills is something that your girlfriend is allergic to, it might be an issue. For example, I can't take some generic medicine formulations because they 'go through my system really fast.'
posted by corprew at 6:33 PM on December 27, 2009

It may also be a case of the antibiotic not reaching sufficient concentration in the pocket of worst infection. This happens with sinus infections where the antibiotic carried in the blood never fully wipes out the bacteria in the sinuses because the sinuses are poorly supplied by tiny capillaries. Something similar could happen in the inner ear.
posted by slow graffiti at 7:29 PM on December 27, 2009

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