The bugs of summer Scared of bacteria? We have the scoop on your microbial friends and foes
Take a moment to gaze at your reflection in the mirror. What do you see? The surface of your skin? The inside of your mouth? Take a closer look: Believe it or not, bacteria outnumber human cells 10 to one.
Where do they come from? Some hop on board during the birthing process. Others enter the mouth during infancy, when babies breastfeed and fend off kisses from Aunt Mildred. Many more are acquired from food and drink over the years.
But before you try to scour the 90 trillion or so bugs from your body, relax ... for the most part, there's nothing to fear. As disturbing as it sounds, bacteria make our bodies work. Sure, we could do without the body odor or stale morning breath our microbial guests leave behind, but we wouldn't necessarily want to live without bugs such as Lactobacilli, which stop yeast from infecting the female genital tract, or the intestine-dwelling bacteria that fend off the pathogens humans ingest.
"Americans tend to have an irrational fear of bacteria everywhere," says Paul Gulig, Ph.D., a professor of molecular genetics and microbiology in the College of Medicine.
That's ironic, considering that "many, if not most, of the infectious diseases you become infected with are caused by microorganisms that you carry around with you all the time," says J. Glenn Morris, M.D., M.P.H., director of UF's Emerging Pathogens Institute.
For the most part, these bugs keep us healthy. But when they appear in the wrong place at the wrong time, illness can strike. Many women have experienced the painful burn of a urinary tract infection when E. coli takes a wrong turn up the urethra, and it's no news that Staph loves to cause skin infections.
"We're surrounded by this cloud of bacteria," Morris says. "Our body is built with a variety of defense mechanisms that keep those bacteria out and safely removed from where they're going to do harm. But if there are breakdowns in the body's defense mechanisms, those bacteria can get their revenge and infect us."
And revenge is apparently a dish best served warm, at least for bacteria, which tend to thrive in the summer months. That's why in this issue, the POST is taking a look at some of the top places bacteria lurk. So before you hit the beach or down those raw oysters this summer, you may want to check out the following words of advice UF experts had about our bacterial friends (and frenemies).
Hazard No. 1: The Beach
Sharks aren't the only things to worry about off Florida's Gulf Coast. Almost all oysters there are infected with a flesh-eating pathogen called Vibrio vulnificus. The good news? Fewer than 50 infections are reported each year. The bad news? Half those patients die within hours.
Even if you don't eat oysters, walking barefoot over oyster beds isn't a good idea either. A small cut can rapidly progress into a fulminating leg infection. Often, amputation is the best treatment.
Still, one of the biggest enigmas in the field is why so few people — mostly those with compromised immune systems — become infected, while most do not.
"Why can such a terrible, rapid, destructive disease process occur so rarely when so many people, particularly immunocompromised people, are exposed to the bacteria?" Gulig asks.
Gulig's group was among the first to show that some strains of the bacteria cause rapid and debilitating disease, while others aren't quite as threatening. This year, they plan to compare the genetics of the two strains to home in on genes important for causing disease.
Hazard No. 2: The Cookout
Unless you've been living in a cave, you've probably heard about the recent outbreak of illness associated with tomatoes. Researchers aren't sure whether tomatoes were actually to blame, but they do know what stowaway bacterium caused all the trouble: Salmonella, a foodborne pathogen that causes gastrointestinal distress.
"There is a striking increase in the amount of foodborne disease during the summer months," Morris says. "It's more difficult to follow the standard food-safety recommendations as far as keeping cold foods cold and hot foods hot."
Another often-overlooked pathogen is Listeria monocytogenes. Low levels of Listeria are present in many foods, including meat, produce and soft cheeses, and of the 2,500 people infected each year, few experience more than mild symptoms. But pregnant women beware: This bacterium is one of the most common bacterial causes of miscarriage and stillbirth.
"The woman usually gets a mild febrile illness, but it can pass through the placenta and kill the fetus," says Fred Southwick, M.D., division chief of infectious diseases at the UF College of Medicine, who studies the movements of Listeria inside cells to understand how the bacteria hijack human cells to sidestep antibiotics and the human immune response.
Unlike most bacteria, Listeria thrives at refrigeration temperatures, and infections can be difficult to trace because the incubation period ranges from two days to two months. Pregnant? Avoid foods that have been refrigerated for more than a few days and zap cold cuts in the microwave until steaming hot before layering them on your sandwich.
Hazard No. 3: The Great Outdoors
Floridians have worried about a lot of things through the years, but Lyme disease wasn't always one of them. Now, thanks to our RV-driving friends from the North, the tick-borne disease is here to stay.
Veterinarians noticed the first cases of Lyme disease in South Florida in the 1980s. It took several years before experts traced the influx of infections to Yankee snowbirds. They brought their dogs. The dogs brought the ticks. And the ticks brought the bacteria, Borrelia burgdorferi.
"For some time, the only animals we saw here in Florida with Lyme were those that traveled back and forth," says Rick Alleman, D.V.M., Ph.D., a professor of physiological sciences in the College of Veterinary Medicine. "Now it's here. There are dogs that have become Lyme positive that have never left the state."
The infection can be treated easily with antibiotics, but in some cases, the bacteria cause the human immune system to attack its own cells, resulting in recurrent arthritis.
"Some people and animals that develop Lyme arthritis have perpetual disease even once they're treated with antibiotics to kill the organisms," says Alleman, who studies Anaplasma phagocytophyla, a similar bacterium also transmitted by deer ticks. "In some areas of the country where Lyme is really prevalent there are even support groups that people will attend."
Hazard No. 4: The Hospital
If you've been stricken with any of the first three hazards, chances are you've been admitted to a hospital. But don't rest too easy: If you're trying to avoid bacterial infections, the hospital isn't necessarily the best place to be.
"Antibiotic resistance is becoming a huge problem, particularly in the hospitals, and at the moment we don't seem to have a good handle on it," Morris says.
Historically, patients have been overtreated with antibiotics and then released into the community, where they unknowingly spread drug-resistant bacteria. One of them is Pseudomonas aeruginosa, the most common cause of infection in patients hospitalized for more than a week.
"Pseudomonas is an environmental bacterium," says Shouguang Jin, Ph.D., a professor of molecular genetics and microbiology in the College of Medicine. "It's distributed all over the soil, the water, the air. Wherever you go, it's there."
Like other pathogens, antibiotic resistance makes Pseudomonas infections difficult to treat, says Jin, who studies how the bacteria avoid being killed by antibiotics.
"One of the mechanisms that's really important is turning off the membrane permeability, like shutting off the door (to the cell) so that the antibiotics can't penetrate," says Jin, whose research has shown that this doorway opens and closes in response to signals in the external environment. Jin hopes his finding will pave the way for new therapies.
Until new drugs become available, experts are focusing on preventing the spread of drug resistance in the hospital. Southwick helped initiate a stewardship program at Shands at UF that monitors the use of antibiotics and encourages health-care workers to take precautions to stem the spread of drug-resistant pathogens.
"The majority of infections are viral and antibiotics don't help," says Southwick, who published a textbook to educate clinicians on the topic. "However, physicians use antibiotics even though the patient doesn't have a bacterial infection. That's one of the problems we have."
Hazard No. 5: The Locker Room
About 30 percent of the population carries staph bacteria on their skin and in their noses, but only about 1 percent of us are colonized with the more lethal methicillin-resistant Staphyloccocus aureus, also called MRSA.
"MRSA used to be found almost exclusively in the hospital environment, where you had very sick patients with staph infections who were being treated with lots of antibiotics, putting the selective pressure on those organisms to acquire resistance," Gulig says.
But eventually those bacteria evolved and acquired the ability to move effectively outside of the hospital and throughout the community.
"All of a sudden, what we're seeing is the local football team showing up with MRSA and your great-aunt showing up with MRSA," Morris says.
The latest hubs for MRSA infection are fitness centers, where sweaty people share equipment ... and bacteria.
"I don't go to the fitness centers, but I wouldn't be surprised if people spent more time wiping equipment down with disinfectant solutions than actually working out," Gulig says.
Infections are also common among athletes in contact sports, such as football.
"The problem with football players, in particular, is that it's a contact sport and they get cuts and scrapes," says Southwick, who helped track the source of an outbreak at UF. "If you carry MRSA on your skin and don't get cuts and scrapes, it won't cause a problem. But when you get a break in your skin, the bacteria can take hold and cause very serious problems."
Hazard No. 6: Your Mouth
It's been called the gateway to the body, and aptly so. Oral bacteria don't always stay in the mouth. After a routine dental procedure, it takes less than a minute for these bugs to appear in the heart, lungs and other areas of the body.
"The interesting thing about the oral cavity is that there are probably 700 to 800 species that can be there," says Martin Handfield, Ph.D., an associate professor of oral biology in the College of Dentistry. "In any given mouth, you probably have between 60 to 70 different species at a given time."
But of all those bacteria, only a few are known agents of disease, Handfield says. And they don't just cause diseases in the mouth. Porphyromonas gingivalis, the bug that causes periodontal disease, has been found in the wombs of women experiencing preterm labor and in the hearts of patients with cardiovascular disease.
That isn't the only oral bacterium implicated in heart disease. Have a sweet tooth? Watch out. Researchers in UF's department of oral biology were among the first to discover that certain strains of Streptococcus mutans — the same bacteria that love to eat sugar and spit out caries-causing acids — are capable of invading tissues in the heart.
"We performed a series of investigations that may change the image of S. mutans as an acid-puking bug that's only good at eating away your tooth enamel," says Lin Zeng, Ph.D., a postdoctoral fellow in the College of Dentistry.
The take-home lesson? Bacteria cause problems when they go renegade in the body. But unless you have another plan for breaking down certain vitamins and foods or any of the other functions our microbial tagalongs handle for us, we have to live with them. Germaphobes, this means you too.
"Maybe it's time to stop treating organisms as if they are pathogenic or nonpathogenic," Handfield says. "Maybe all organisms are part of a spectrum of pathogenicity where at one extreme they're typically good and healthy and part of the good flora unless you're putting them in a weird situation, and at the other extreme, they may be involved with disease most of the time."
Hazard No. 7: The Day Care Center
If you've ever turned up your nose at the smell of children running rampant around a day care center, you might be on to something. Those tiny tots are full of more than just sugar and spice and everything nice. Somewhere in the mix could be the diarrhea-causing bacteria Shigella dysenteriae.
"The main places you hear about Shigella in the United States are day care centers. It's not a foodborne pathogen — it's usually transmitted person to person. In day cares, little kids handle their diapers and all kinds of things," says Southwick, who is studying the ways Shigella paralyzes the immune system and migrates around the body.
"Shigella usually causes the cells to die pretty quickly, so you get a big inflammatory response," says Southwick. "You get large ulcers in the GI tract that bleed. It causes terrible diarrhea and bloody diarrhea because of its ability to spread and cause tissues and cells to die."
Fortunately, the Centers for Disease Control and Prevention estimates that fewer than 53 Americans become ill each year from the bacteria, and the illness is easily cleared up with antibiotics.
Hazard No. 8: The Bedroom
Long walks on the beach. Strolling in the summer moonlight. Yes, summer is a time when new love blossoms. And, if you're not careful, all that romance could put you in danger of meeting the bacteria behind Hazard No. 8 on our list — Chlamydia.
One in every four teenage girls in the United States — about 3.2 million — is infected with a sexually transmitted disease, according to the CDC. Chlamydia trachomatis infections are the second most common, after the human papillomavirus. Chlamydia, which only survives inside human cells, enters the body through the eyes or genital tract and causes a relatively short-lived infection with lasting consequences, says Scott Grieshaber, Ph.D., an assistant professor of oral biology in the College of Dentistry.
"Chlamydia is eventually controlled by the immune system and killed, but it causes this horrible scarring effect," Grieshaber says, describing how the infection can permanently scar the fallopian tubes and uterus, leading to ectopic pregnancies or infertility.
This effect is particularly gruesome when Chlamydia enters the eyes by hand contact or, in less hygienic regions, contact with flies.
"Eventually, the eyelids flip over and the eyelashes cause abrasions across your cornea until finally the scarring gets so bad that you can't see," Grieshaber says. "It's a really horrible disease."
Chlamydia was originally thought of as a disease of the tropics but is actually a disease of poverty, says Grieshaber, who is studying how these bacteria enter human cells and live undetected by the immune system until late during the infection.
"Chlamydia replicates at very high numbers and bursts the cells, then is released. This then causes a huge inflammatory response," Grieshaber says. "It's a real fight (between the bacteria and the immune system) between who kills the most cells. That's where all the damage comes from: the host immune system trying to clean up this infection."
Hazard No. 9: The International Flight
More people die from Mycobacterium tuberculosis infections than from any other bacterial disease.
"One-third of the world is infected with latent TB, making it the most common infection in mankind," says Michael Lauzardo, M.D., an assistant professor of pulmonary, critical care and sleep medicine at UF's College of Medicine and director of the Southeastern National Tuberculosis Center. "Eight to 10 million people develop TB each year and almost 2 million die from it worldwide."
An airborne disease, tuberculosis is transmitted from person to person. Once the organism gets into the lungs, it moves into the body's immune cells, where it can gain access to the rest of the body. After causing a primary infection, it goes into a latent phase that may last months or even decades before the disease manifests.
"The biggest challenge is the emergence of drug-resistant strains around the world, making TB essentially untreatable in some individuals," says Lauzardo, noting it's also challenging to control TB in areas where HIV is common. "The two diseases feed off one another and present challenges that we are, as of yet, unable to overcome with currently available strategies."