The real issue with antibiotic-resistant bacteria is that virtually all of our antibiotics are natural chemicals, or derivatives of them, that have been in the environment for millions or possibly billions of years. That means that the genes for antibiotic resistance already exist in the environment, or for structurally-modified antibiotics like the various penicillins, require only modest modifications to the antibiotic resistance genes. When bacteria become antibiotic-resistant, it isn’t a matter of them suddenly developing a gene that destroys the antibiotic, it’s a case of a preexisting gene entering a population.*
One of the annoying things about bacteria is that there are tons of ways for bacteria to spread genes to other bacteria, sometimes completely unrelated bacteria. Viruses sometimes pack up host genetic material instead of their own, and inject it into a new host. Some bacteria, such as Bacillus, are naturally “competent” which means they can suck up naked DNA from the environment and use it as its own. And lots of bacteria are having sex all the time and spreading genes willy-nilly that way. All these mean that if an antibiotic resistance gene is in the environment, there’s plenty of ways for it to get into bacteria and help them survive. At that point, you’re selecting for bacteria with these genes and boom, now you’ve got an antibiotic-resistant population.
As far as I know, fungi aren’t nearly as promiscuous as bacteria are, and sex is a much slower process for them. When bacteria mate, it’s just a poke and a squirt and boom, you’ve got a bacterium with new genes, while fungi have to fuse, undergo meiosis, differentiate into sexual spores, germinate, and THEN compete in the environment. You’ll only have mating within a single species, and there generally aren’t many ways for DNA to go from the environment into fungi, so you pretty much need to bring in a resistant individual fungus, of the species that’s causing the infection, and then it needs to either proliferate from scratch.
So it’s certainly possible for it to happen, but bacteria have ways of spreading genes through a population far faster than fungi do. Resistance certainly can and does evolve in eukaryotes (see mosquitoes and DDT for example) but generally over years and decades rather than days. That said, I’d still treat it aggressively if for no other reason than that I wouldn’t want to get athlete’s foot again!
This is all off the top of my microbiology undergraduate head, so if anybody knows better feel free to correct me, but I think I’ve got the broad strokes right.
*It’s true that resistance can develop through mutations that change the shape of the affected protein, keeping the antibiotic from interacting with it, but I don’t think these are important for the spread of antibiotic resistance. It’s much easier to spread a novel gene than it is to outright replace an essential gene with a stranger’s.