Harry L.T. Mobley has devoted the better part of 25 years to alleviating the “considerable human misery” created by bacteria that make themselves a little too at-home in millions of women’s urinary tracts.

Working six days a week, Mobley and the dozen researchers in his University of Michigan lab are trying to develop a nasal spray vaccine for urinary tract infections, to keep these rugged invaders from sticking to the bladder, climbing into kidneys and inflicting a torrent of itching, burning, and frequent urination.

Despite the team’s purposeful labors, a safe and effective vaccine for urinary tract infections remains at least a decade off, Mobley figures.

“It’s painful to say that, because it’s such an urgent need,” Mobley, a bacteriologist who chairs the department of microbiology and immunology at Michigan, told ABC News in an interview this week. “Women that get repeated infections — and I mean one after another and another — represent about 2.6 percent of all women. these are the ones we get e-mails from that are totally miserable.”

Urinary tract infection (UTI) is second only to respiratory infection as the most common contagious malady. it disproportionately plagues women, who can be stricken with the pain, pelvic pressure and associated symptoms at many stages of life: when they become sexually active, during pregnancy, around menopause, and in later years if they’re hospitalized or in nursing homes.

Although few cases prove fatal, recurrent infections — more than three a year — of the bladder (cystitis) or kidneys (pyelonephritis) exact an enormous economic toll in medical costs and lost work days. there is a psychological cost too: sufferers feel debilitated and worried that something as enjoyable as sexual activity could lead to another infection.

The National Institute of Diabetes and Digestive and Kidney Diseases pegged the annual cost of evaluating and treating UTIs in 2000 at $3.5 billion (equivalent to the payout so far in BP’s settlement of the Gulf oil spill). Women’s cases accounted for $2.5 billion of the total. in the vast majority of cases, these infections arise in otherwise healthy women.

Mobley’s top target, Escherichia coli bacteria, are responsible for 75 to 90 percent of UTIs, with smaller contributions from Staphylococcus saphrophyticus, Enterobacteriaceae, Proteus and Klebsiella. many of these microbes, which form colonies in the delicate tissues lining the bladder, have grown increasingly resistant to antibiotics, forcing major changes in how and what doctors prescribe to knock them down.

Gone are the days of simply getting a prescription for penicillin.

Instead, patients undergo tests to determine which bugs are responsible and which drugs can be given for the shortest duration without promoting antibiotic resistance. in one interesting twist, doctors have turned back the clock by relying on a 50-year-old drug, nitrofurantoin (also called Macrodantin or Furodantin), which had fallen out of favor, but has become a mainstay because it doesn’t promote resistance.

Many women become trapped in a vicious cycle as antibiotics rout the bacteria, but kill off good bacteria that keep yeast in check, setting the stage for yeast infections they then treat with antifungal pills or creams. They’re then susceptible to additional UTIs because their bodies’ defenses “are not up to par,” said Dr. Ariana L. Smith, a urologic surgeon at the University of Pennsylvania.

Because the decrease in estrogen associated with menopause makes the vagina more alkaline, Smith prescribes vaginal estrogen to restore the formerly-acidic environment that’s inhospitable to disease-causing bacteria.

Most UTI patients have experimented with self-help remedies, downing pitchers of cranberry juice or cranberry extract pills, although the largest and best-designed studies to date show cranberry doesn’t help much.

Tired of spending months on continuous low-dose antibiotics as a preventive, chronic UTI sufferers increasingly try complementary and alternative approaches, such as acupuncture and probiotics, which have been shown in doctors’ practices and some clinical trials to make them feel better.

Ultimately, vaccines may be the best way to reduce the incidence of UTIs, but in the meantime, researchers are studying UTIs from many angles. The biggest strides in UTI research have come in understanding the microbiology and genetics of the disease-causing bacteria; the biology and responses of the tissues they infect; and the response of the immune system to the bacterial invasion.

Scientists are trying to use that information to defeat those marauding microbes before they get the upper hand. They’re devising ways of boosting the immune system so that if nasty bacteria reach the urinary tract, the immune system can defeat them. They’re also designing vaccines to interfere with bacteria’s ability to attach to urinary tract cells.