Comments on: Faster Than a Speeding Antibiotic…

By: Richard

Richard — Mon, 26 Oct 2009 05:26:09 +0000

The giving of low doses of antimicrobials to animals over a prolonged period is the ideal experimental setup if one wants deliberately to generalt resistance. Whereever people have looked at it, animals from farms, or indeed countries in which it is usual to use antimicrobials as growth promoters carry higher proportions of resistant organisms in their bowels. Meat from the slaughterhouse is inevitably contaminated by faecal matter, so if you culture thouse plastic wrapped tasty chunks of meat at the supermarket, they will carry faecal bacteria.
If absoluttely scrupulous food hygiene is not practiced (and where is it?), bacteria will be transferred from raw meat to ready to eat food, and may colonise the eater’s bowel.
Even if the transferred bacterium is not a pathogen (that is, it doesn’t cause disease, and the vast majority of bacteria are not pathogens) the genes for resistance to antimicrobials are often on “transposable elements”, bits of DNA that can go from one bacterium to another, often only remotely related bacterium.
How often this happens, and how important it is for human disease are very difficult to say. Most bacteria are very fussy in terms of the hosts in whcih they can live, and the overwhelming majority of the bacteria in a load of animal faeces consumed with your salad will not be able to survive in the human bowel. Some, though, may do a bit of swapping of DNA before they die.
A few bacteria, however, do infect both humans and animals. The best studied of these is Campylobacter. Almost all cases of ciprofloxacin resistant campylobacteriosis diagnosed in Denmark (the country in which use of antibiotics as growth promoters has longest been banned) are in people who have eaten chicken imported into Denmark, not locally raised. Other studies, also in Europe, show that, while one is more likely to pick up a Campylobacter from organic free-range chicken, that Campylobacter is much less likely to be antibiotic resistant. There is similar evidence around antibiotic resistant Salmonella.
For some other intestinal organisms, such as the strains of Escherichia coli that cause urinary tract infection, there is somewhat weaker evidence linking resistance to animal husbandry practices.
For non-enteric organisms (for example Staphylococcus aureus), there is little or no evidence that animal husbandry practices affect resitance rates in humans.
Whatever happens on the farm, the biggest risks are in the intensive care units of hospitals (everyone on antibiotics, tubes in every orifice, lots of care procedures done by staff too busy to disinfect their hands before and after every patient contact, even though they know they should).
The spread of antimicrobial resistance requires not only the antimicrobial selective pressure which comes from the use and abuse of antibiotics, but also circumstances which allow for spread from one host to another, whether through poor food hygiene, poor household hygiene or lapses in hospital infection control. Only addressing both selective pressure AND spread do we have any hope of slowing the rise of resistance.

A bit off topic, but the third generation cephalosporin most used by New Zealand GPs will almost certainly be ceftriaxone, given as a single intramuscular injection for treatment of gonorrhoea. Only around three years ago, the first line drug would have been a single tablet of ciprofloxacin. When the gonococcus becomes resistant to third generation cephalosporins, there is no easy next option. A few such horribly resistant strains have been reported from Japan. They have still been susceptible enough to be treated with a higher dose of ceftriaxone – given by intravenous infusion – but for how much longer?

By: gander

gander — Mon, 26 Oct 2009 01:47:34 +0000

Wally, which generation a cephalosporin, or any other antibiotic, belongs to doesn’t determine its value. Few of the infections a GP will likely see in his practice should be treated with a third-generation cephalosporin – but many of them could be treated with a first-generation. For some infections good old penicillin G from 1942 is still the best drug.

I’d like to know for what indications the manufacturer was encouraging the vets to use a 3rd generation cephalosporin, though. That does ring alarm bells.

You have a point about the overuse of antibiotics in animal husbandry (not particularly in veterinary practice, but rather as feed supplements). I understand that the poultry industry in North America some years back was dosing birds with enrofloxacin (closely related to human drugs Noroxin, Ciproxin and others), which might have been part of the reason that that class of drugs are becoming less useful in practice. Richard, any comment?

By: wally

wally — Mon, 26 Oct 2009 01:22:33 +0000

gp’s have a relatively limited number of antibiotics they can use.
i would be interested to know if the widespread use of advanced antibiotics in the veterinary industry has anything to do with the emergence of resistant organisms.
a microbiologist told me a couple of years ago he went to a vet conference where they were advertising 3rd generation cephalosporins for use in animals. the poor old gp’s in nz are still on the 1st generation!

By: Richard

Richard — Sun, 25 Oct 2009 18:43:08 +0000

Here is a direct quote hidden near the bottom of a page on the Waikato research unit website:
“None of the results being obtained clinically should be considered evidence that Active Manuka Honey is more effective than other honey – a comparative clinical trial will be needed to establish that. Nevertheless, there are good theoretical reasons for choosing to use Active Manuka Honey with a good level of the non-peroxide antibacterial activity for management of wound infections.”
You can make a theoretical case for just about anything, and I don’t buy their theory.

By: Johnnieboy

Johnnieboy — Sun, 25 Oct 2009 10:35:25 +0000

Good luck finding one of those mythical ‘peer-reviewed papers from researchers not dependent on funding from the makers of the products they are researching’ for products in a doctor’s practice or hospital. You haven’t commented on whether there is any objective merit to anything said from Waikato University on the issue of active manuka honey vs ordinary honey.

You’re missing the point that the cost of research is so high that if pharma money doesn’t support it- it often doesn’t get done. Dr Molan was probably doing his research long before there was even a nickel to be made from it- who gives a crap about something we put on our toast anyway, and something that a bunch of house-wives think fixes a few scabs? The answer- now it’s our fastest growing industry.

I suggest to avoid the hype and the scam artists that you only bother buying that honey that the research unit used for their research- summerglow apiaries (tastes good too but still has that manuka tang). Only one producing pharmaceutical grade stuff apparently, and their prices are much better than anything you’ll see in the supermarket (or airport!). Next time the stomach gives you grief, it’s a great, cheap fix.