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(单词翻译:双击或拖选)
Unraveling a hidden cause of UTIs — plus how to prevent them
If you've had a urinary tract2 infection, you're in good company. About 60% of women will develop one in their lifetime. UTIs lead to more than a million emergency room visits each year and more than $2 billion in medical costs.
Many of these infections are caused by common strains of E. coli bacteria that humans have lived with for millennia3. But now researchers are investigating an unsettling source of some of the illness: the meat supply.
UTIs make urinating painful or difficult and can interfere4 with sex, sleep and exercise. Sometimes they can cause fever or chills. But since they can be treated with antibiotics6, they've been considered more of a nuisance than a public health problem. Recently though, multi-drug resistance to some of the bacteria, including strains of E. coli, that cause UTIs has become an increasing worry.
But many of the more than 700 known strains of Escherichia coli are harmless. So the authors of a new study set out to solve a mystery: Which strains cause infections, and where do they come from?
They had a hunch7 that the U.S. animal agriculture system could be a likely culprit.
Both farm animals and humans have some strains of E. coli bacteria in their guts8. When farm animals are slaughtered9, the bacteria from their guts can contaminate raw meat, which can in turn contaminate kitchen surfaces during cooking.
A team of researchers spent one year collecting samples of raw meat in Flagstaff, Ariz., to find out if there's an overlap10 between the strains of E. coli in the meat supply and the strains that can make people sick.
"We sampled all the chicken, turkey and pork from every grocery store in the city twice per month," explains Lance Price, a professor at George Washington University Milken School of Public Health and the founding co-director of the Antibiotic5 Resistance Action Center.
They also collected urine samples from the Flagstaff Medical Center from people who were hospitalized with UTIs.
In their study, published in the scientific journal One Health, the researchers found that about 8% of UTIs in Flagstaff could be attributed to bacteria from meat. Nationwide, they estimate as many as 640,000 infections each year are caused by foodborne E. coli strains from animals.
"Our study provides compelling evidence that dangerous E. coli strains are making their way from food animals to people through the food supply and making people sick," Price says.
Genomic sleuthing clarifies the link with livestock11
To pin down the connection, the researchers brought both the meat and urine samples back to their laboratory and cultured for E. coli, explains co-author Paul Keim, the executive director of the Pathogen and Microbiome Institute at Northern Arizona University. They performed genomic sequencing to inspect the microbes' DNA12.
This helped them identify segments of DNA from the bacteria that are specific to strains from animals, and others that are specific to strains in people. "We started recognizing that, hey, here's these little packages of DNA that are really strongly associated with chicken," Price explains. Others can be strongly associated with pork, and others with people.
"The genomic analysis allowed us to match up a number of different strains," explains Keim.
The degree of overlap between the E. coli strains from meat and those found in samples from patients with UTIs was striking, says Tim Johnson, a professor at the College of Veterinary Medicine at the University of Minnesota who studies poultry13 diseases and genomics.
"When I first saw the data, I was pretty overwhelmed at the connectivity," Johnson says, though he says the study falls short of proving that the UTIs were caused by E.coli from meat. He points to the other ways the bacteria can contaminate the food supply. For instance, they can get into irrigation water and contaminate crops.
Big picture, Keim, says, the study shows "there's lots of E. coli strains out there that cause UTIs and you can get them through the food supply."
Stopping human disease may start on the farm
The researchers plan to continue to trace the connection between the food supply and human UTIs. The study allowed them to create a data platform to which they hope to build on. It's similar to how the FBI developed a database of criminal's DNA fingerprints14 that they can search to solve crimes, explains Keim. "We didn't have that for E. coli," or for UTIs until doing this study, he says.
This kind of knowledge could lead to new strategies to prevent the spread of bacteria that cause UTIs.
For instance, the study points to two E. coli strains that have particularly high virulence15, including the ST131-H22 strain, which has been found in poultry operations. A previous study showed this strain may be a vehicle for human infection.
It turns out this strain is also causing disease in birds in poultry operations, so Johnson says some farmers vaccinate16 their flocks against it. "They use what's called an autogenous vaccine," Johnson explains. Those are customized for the flock from strains of bacteria isolated17 from animals in the flock. He says a better understanding of the overlap between human disease and animal disease, can help farmers take proactive prevention steps.
"If you're finding a problematic strain that's killing18 chickens or turkey, that could also be a food safety threat, they can make vaccines19 against those strains to try to eliminate them from the barns," Johnson says.
Ways to prevent UTIs
UTIs involve a complex interplay of bacteria, our microbiomes, immune systems and anatomy20, says Dr. Michelle E. Van Kuiken, a urologist who specializes in female pelvic medicine, at the University of California, San Francisco. And Van Kuiken says patients need to understand they may get sick because of factors beyond their personal control.
"We're seeing this connection and we need to be cognizant about how large-scale animal agriculture could be impacting human health," Van Kuiken says. "To some extent, women have been done a disservice by them thinking it's something they're doing wrong or things that they can modify," she adds.
Though some of what's causing them may be out of your control, there are evidence-based tips worth trying to prevent recurrent UTIs.
1. Understand your anatomy
People born with female anatomy are more prone21 to urinary tract infections, explains Elodi Joy Dielubanza, a urologist at Brigham and Women's Hospital. The urethra, which carries urine from the bladder outside the body, is typically shorter in women and it's in very close proximity22 to the anus.
The way the E. coli ends up invading the urinary tract is kind of gross, but the bottom line is that the bacteria comes out in our poop. And, if you don't wipe right (from front to back), it can end up in the urethra where it can invade the urinary tract.
Sex can play a role too. During penis in vagina sex, the bacteria – which can live in the tissue near the anus – can travel along the penis toward the entrance of the urethra. That's why it's smart to urinate after sex to flush out some of the bacteria.
2. Stay hydrated
It's important to consume enough fluids to maintain adequate urine production, says Dielubanza. "Our body's best defense23 against invading bacteria is to flush it away," she says. "I like to advise my patients to maintain at least a daily intake24 of six cups of water."
3. Be careful with kitchen hygiene25
E. coli can not survive high temperatures, so if you cook your meat to recommended minimum temperatures, you will kill off the bacteria.
The bigger risk may be poor kitchen hygiene, says University of Minnesota's Tim Johnson. "It's a common misperception that most of the transmission from chicken to human occurs by eating undercooked meat. And the fact is that the vast majority of people fully26 cook [it], especially poultry," he says.
Pay attention to utensils27 that have touched raw meat, like the cutting board, knife and spatula28. "Even though you think you may have washed them thoroughly29, maybe you didn't," Johnson warns. Raw meat liquid can also get on the counter surfaces, so pay attention to where it seeps30 out and clean it up.
The USDA has tips on how to prevent cross-contamination in the kitchen and when you're outdoors on the grill31.
4. Supplements may help prevent recurrent infections
Several studies show that cranberry32 supplements can help reduce the risk of recurrent UTIs, according to a review by the American Urological Association. Compounds in cranberries33, known as proanthocyanidins, may help prevent bacteria from adhering to the lining34 of the urinary tract. But Dielubanza says the evidence is mixed, and she points out there's usually not enough concentration of the compounds in many of the sweetened cranberry juices sold in grocery stores to make a difference. So if you want to try it, some doctors suggest cranberry supplements instead.
Though there's less research to date, there's growing data supporting the use of another supplement, D-Mannose, a type of polysaccharide. Van Kuiken explains that D-Mannose gets rapidly excreted in urine. When bacteria bind35 to the polysaccharide, it can help flush them out of the urinary tract. "It's a safe supplement that's available over the counter," Van Kuiken says.
5. Approaching menopause and after, use vaginal estrogen cream
As the female body starts producing less estrogen during the years leading up to menopause, risk for UTIs can go up, says Dielubanza. "The loss of estrogen can change our vaginal microenvironment and make us more prone to developing UTIs," she says. "The good bacteria that colonize36 our vaginas may be less likely to survive after menopausal changes."
For women in perimenopause or later dealing37 with recurrent UTIs, some physicians advise starting some patients on topical vaginal estrogen.
"It amazes me how many women that I see that fall into this age category who have not heard of vaginal estrogen," says Van Kuiken. "Probably one of the single most important things that we can do to help prevent recurrent urinary tract infections is [prescribe] topical estrogen."
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| n.抄本，誊本，副本，肄业证书 | |
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tract
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| n.传单，小册子，大片(土地或森林) | |
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millennia
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| n.一千年，千禧年 | |
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interfere
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| v.(in)干涉，干预；(with)妨碍，打扰 | |
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antibiotic
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| adj.抗菌的；n.抗生素 | |
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antibiotics
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| n.（用作复数）抗生素；（用作单数）抗生物质的研究；抗生素，抗菌素( antibiotic的名词复数 ) | |
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hunch
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| n.预感，直觉 | |
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guts
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| v.狼吞虎咽，贪婪地吃，飞碟游戏（比赛双方每组5人，相距15码，互相掷接飞碟）；毁坏（建筑物等）的内部( gut的第三人称单数 )；取出…的内脏n.勇气( gut的名词复数 )；内脏；消化道的下段；肠 | |
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slaughtered
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| v.屠杀，杀戮，屠宰( slaughter的过去式和过去分词 ) | |
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overlap
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| v.重叠，与…交叠；n.重叠 | |
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livestock
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| n.家畜，牲畜 | |
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DNA
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| (缩)deoxyribonucleic acid 脱氧核糖核酸 | |
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poultry
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| n.家禽，禽肉 | |
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fingerprints
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| n.指纹( fingerprint的名词复数 )v.指纹( fingerprint的第三人称单数 ) | |
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virulence
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| n.毒力，毒性；病毒性；致病力 | |
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vaccinate
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| vt.给…接种疫苗；种牛痘 | |
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isolated
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| adj.与世隔绝的 | |
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killing
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| n.巨额利润；突然赚大钱，发大财 | |
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vaccines
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| 疫苗，痘苗( vaccine的名词复数 ) | |
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anatomy
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| n.解剖学，解剖；功能，结构，组织 | |
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prone
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| adj.(to)易于…的，很可能…的；俯卧的 | |
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proximity
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| n.接近，邻近 | |
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defense
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| n.防御，保卫；[pl.]防务工事；辩护，答辩 | |
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intake
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| n.吸入，纳入；进气口，入口 | |
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hygiene
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| n.健康法，卫生学 （a.hygienic） | |
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fully
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| adv.完全地，全部地，彻底地；充分地 | |
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utensils
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| 器具，用具，器皿( utensil的名词复数 )； 器物 | |
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spatula
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| n.抹刀 | |
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thoroughly
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| adv.完全地，彻底地，十足地 | |
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seeps
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| n.（液体）渗( seep的名词复数 )；渗透；渗出；漏出v.（液体）渗( seep的第三人称单数 )；渗透；渗出；漏出 | |
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grill
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| n.烤架，铁格子，烤肉；v.烧，烤，严加盘问 | |
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cranberry
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| n.梅果 | |
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cranberries
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| n.越橘( cranberry的名词复数 ) | |
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lining
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| n.衬里，衬料 | |
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bind
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| vt.捆，包扎；装订；约束；使凝固；vi.变硬 | |
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colonize
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| v.建立殖民地，拓殖；定居，居于 | |
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dealing
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| n.经商方法，待人态度 | |
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