VanAR wrote:Mywan- thanks for your take. Admittedly, I hadn't seen the term "superinfection" before, but after reading, it made sense that it was an infection caused by an antibiotic/antifungal-resistant strain.
The term "superinfection" is actually much more inclusive of all types of simultaneous infections or reinfection of the same cells of pathogenic variants. It was the association of antibiotics implied here that lead me to limit the meaning provided in the present context.
VanAR wrote:My skepticism however, was less technical than even your explanation. My understanding (perhaps flawed) of these types of "superinfections", even in humans, is that they have only been a major problem relatively recently with the advent of rampant overuse of antibiotics, especially as broad-spectrum cleaners in hospitals and other surgical facilities.
Nature has always been in an arms race of this same nature. It is part and parcel to the very concept of evolution to which all living organisms owe their existence. Prior to us developing antibiotics this arms race went on under our noses without our understanding. Penicillin, the first antibiotic safe for humans, occurred naturally in a mold. Today Penicillin is far less useful due to resistance.
It could be said that wide spread use of these antibiotics is the problem, but that is nothing new historically and occurred naturally as well. When some animal evolved a particularly effective defense against some pathogen then evolution dictates that this resistance would increase in the population over generations. As the majority of the total population became more and more resistant then the evolutionary pressure on the pathogen to circumvent this resistance increases. All this occurred naturally until what was a resistance no longer has any advantage (i.e., the resistance in the pathogenic population gains the upper hand), and any new method of resistance that evolves begins spreading through the population.
The "rampant overuse of antibiotics" merely mimics what happens naturally at a more rapid rate, and it only appears to be a recent phenomena since this is our first round of antibiotics where we get to see and understand what has been happening all along because our medicines are visibly losing their effectiveness.
Another interesting question is what happens when a population fails to develop an effective resistance to some pathogen. As this pathogen becomes more effective at killing the host population then those pathogenic variants that are less lethal has an advantage, since a dead host is not a host. If a pathogen wipes out its population of host it wipes itself out. A variant of the predator/prey relation applies to pathogens as well. That is why the vast majority of such organisms are in some form of symbiotic relationship with their host. So long as the host population is high and the pathogen population is low the advantage to a symbiotic relationship is lessened.
VanAR wrote:Is there any history, or any evidence, of antibiotic/antifungal-resistant strains in the pathogens of non-mammals? Perhaps naively, I'm assuming that many of these pathogens wouldn't encounter such antibiotics (I'm using that term generally here) frequently enough for there to be a strong selective pressure for resistant genes, even in captive reptile populations. On the other hand, Mader's book suggests that experiences like Mulebrother's are fairly common for fungal infections in reptiles.
Yes, loads of evidence. With farm animals and veterinarian antibiotic use here is an article:
Globally, an estimated 50% of all antimicrobials serve veterinary purposes. Bacteria that inevitably develop antibiotic resistance in animals comprise food-borne pathogens, opportunistic pathogens and commensal bacteria. The same antibiotic resistance genes and gene transfer mechanisms can be found in the microfloras of animals and humans. Direct contact, food and water link animal and human habitats. The accumulation of resistant bacteria by the use of antibiotics in agriculture and veterinary medicine and the spread of such bacteria via agriculture and direct contamination are documented.
You mention non-mammals and reptiles in particular. Consider the Komodo dragon. Not only has Komodo dragons developed a resistance to a huge variety of bacteria, but has formed a symbiotic relation of sorts such that they actively support these bacteria to help kill prey bitten by them. Any pathogen dangerous to the health of Komodo dragons then by proxy become pathogens to the bacterial colonies they support.
VanAR wrote:Even under optimal circumstances, they're a bugger to get rid of completely, and it's not always clear which antifungal is most effective, or what dose should be used, which compounds the problem. That could lead to a greater probability of developing resistant strains in captivity.
Even if the resistant strains are limited to the hobbyist, and never make up a significant percentage of the total pathogenic population, you could still end up with strains that are more prevalent in the pet trade. Basically this results in a pathogenic variant that specializes in infecting hobbyist environments. We are playing a numbers game with our protocols. The more effective we, or any living organism, become at treating anything the more evolutionary pressure we put on pathogens to circumvent it. The more effective the pathogens become the more evolutionary pressure is placed on them to become less pathogenic.
The difficulty in treating these reptile infections may be due to killing off a lot of harmless microbes should have otherwise out-competed the pathogens. A new mouthwash designed specifically to avoid killing good bacteria appears to be particularly effective so far: http://www.dentistry.ucla.edu/news/new- ... f-the-past
Even if you could send every human pathogen into extinction new ones would evolve in a relatively few years. Nylon-eating bacteria (Flavobacterium) have evolved to eat nylon, which didn't even exist prior to 1935. Our best long term defense against bacteria is bacteria, and you actually need a good human microbiome of bacteria to remain alive and healthy. Their are more bacterial cells in and on you than your body contains and you require them to survive. For something interesting google "fecal transplant