Dear Doctor: I had a urinary tract infection that improved on the antibiotic Keflex, but lab tests showed the bacteria was actually resistant to the Keflex, so I had to switch to a different antibiotic. I don’t understand -- if the infection was resistant, why did the symptoms go away?

Dear Reader: Urinary tract infections, or UTIs, are one of the most common bacterial infections in the U.S. They occur when bacteria -- in the majority of cases it’s E. coli -- colonize any of the tissues or structures of the urinary system. This includes the kidneys, which filter waste and excess water from the blood to make urine; the ureters, which are the tubes through which urine leaves the kidneys; the bladder, where urine is stored; and the urethra, through which urine leaves the body.

Although both men and women can get a UTI, the condition is more common in women. According to some estimates, anywhere from 40% to 60% of women will have at least one UTI in their lifetime. Symptoms can include urine that is dark, cloudy, bloody or pungent, an urgent need to urinate that yields very little urine, pain or burning during urination, and abdominal pain. In the elderly, a UTI can present without any physical symptoms, but result in confusion or temporary cognitive impairment.

Unfortunately, as you have experienced firsthand, urinary tract infections are becoming increasingly challenging to treat. This is due to the growing problem of drug-resistant pathogens, which affect an estimated 2 million people in the United States every year. Antibiotic resistance happens when drugs are no longer effective at completely eradicating the bacteria and fungi that cause infection and disease. That means that although some of the bacteria or fungi may be killed by the drug, others aren’t. Those that are resistant to the drug will continue to grow and reproduce, causing the disease or condition to persist.

We suspect that in your case, the initial antibiotic killed enough of the bacteria that were causing your UTI for the symptoms to abate and afford you physical relief. However, because the infection included bacteria that were resistant to Keflex, the UTI was not being cured. Those bacteria that were resistant to Keflex were continuing to grow. Fortunately, your health care provider followed the current guidelines to send a urine sample out to test for antibiotic resistance. Using the results of those lab tests, you were prescribed a different and ideally more effective antibiotic. In some cases, it can take multiple attempts with different antibiotics to successfully vanquish a UTI. Whichever drug is prescribed, be sure to ask about potential interactions with food or other drugs, and to complete the regimen, even after symptoms go away.

Because of the risk of the infection moving to the kidneys, it’s important to make sure that a UTI is completely cleared up. Patients whose urinary tract infection is caused by a drug-resistant strain of bacteria should continue to be followed after antibiotic therapy is complete. We recommend at least one repeat urine test to “test for cure” and make sure that the UTI has been completely eradicated.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My wife and I appreciate your articles about ticks, and we wonder if you could talk about Rocky Mountain spotted fever? A friend of ours here in Arkansas got really sick from it, and since our family is big on outdoor activities, we want to know what to look for.

Dear Reader: We’re glad the information about tick-borne infections and illnesses has been useful. We get quite a few questions on the topic, which reflects the growing awareness of ticks and the health dangers associated with them.

Rocky Mountain spotted fever, or RMSF, is a potentially deadly disease acquired when an individual is bitten by a tick infected with the bacterium Rickettsia rickettsii. Depending on the region, the disease is spread by the Rocky Mountain wood tick, the American dog tick or the brown dog tick. Although it has been found across wide areas of the United States, Rocky Mountain spotted fever is most often reported in Oklahoma, North Carolina, Missouri, Tennessee and in your home state of Arkansas. It can also be found in parts of the American Southwest and in Mexico.

As with many tick-borne diseases, initial signs of RMSF can be general enough that they are easily attributed to other causes, including a cold or the flu. Symptoms commonly include fever, headache, abdominal pain, nausea, vomiting and lethargy. The rash that usually accompanies RMSF often develops between two and four days after the initial infection, which adds to the challenge of a swift and accurate diagnosis. The rash can take a variety of forms, from bold red splotches to tiny pinpoint dots.

Although a laboratory test is needed to confirm RMSF, the Centers for Disease Control and Prevention urge health care providers to commence immediate treatment when clinical signs and symptoms, as well as a thorough health and travel history, point to the disease. Immediate treatment is crucial in cases of Rocky Mountain spotted fever, and waiting for confirmation from a lab test can put the patient at risk.

The recommended treatment for RMSF is the antibiotic doxycycline. Early treatment can prevent serious illness and death. When left untreated, the bacterium that causes Rocky Mountain spotted fever can cause extensive damage to blood vessels throughout the body, which leads to tissue and organ damage. Death can occur in as little as eight days after the onset of symptoms. At this time, there is no vaccine for RMSF, which makes prevention the only way to avoid infection.

Summer is high season for ticks. These tiny arachnids can be as small as a poppy seed early on in their life cycle, and since a tick bite is usually painless, ongoing vigilance is key. At the risk of repeating ourselves, this includes avoiding densely wooded and brushy areas, covering exposed skin with light-colored clothes, wearing closed-toed shoes, tucking pants into socks, using appropriate pesticides and doing visual body scans, including of pets. And check into local resources. Many communities throughout the U.S. have vector control agencies, which are devoted to the identification and control of dangerous local pests, including ticks.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Our granddad is 86 and wound up in the ER with extreme abdominal pain, which turned out to be gallstones. The doctors say he should have his gallbladder removed. Why? Isn’t that a big operation just to take care of gallstones?

Dear Reader: The gallbladder is a small, pear-shaped pouch that sits on the right side of the abdomen, just beneath the liver. It’s part of the biliary tract, which is a system of organs, ducts and vessels. The structures of the biliary tract -- sometimes referred to as the biliary tree -- secrete, store and guide a bitter greenish-yellow liquid called bile, which aids in the breakdown of dietary fat. Bile is secreted by the liver and is stored in the gallbladder. It’s a complex liquid with dissolved substances that aid in the digestion of fat and play a role in the elimination of certain waste products. When bile isn’t being used for digestion, it is stored in the gallbladder.

In some people, small hardened deposits known as gallstones may form. This often happens because of too much cholesterol, or when the gallbladder is unable to empty properly. People who are overweight or obese are at an increased risk of gallstones, as are those who live with diabetes. This is due to the higher level of triglycerides, a type of lipid, in the blood. Rapid weight loss has been known to trigger the formation of gallstones. So can fasting, which is one of the things that can prevent a gallbladder from adequately emptying. A tendency to form gallstones can also run in families.

Gallstones can irritate the lining of the gallbladder and lead to inflammation or infection. Because the gallbladder stretches and squeezes as it fills and empties, gallstones can also shift and move into the bile ducts. Although small stones can pass unimpeded, larger stones can become lodged and cause a blockage. This prevents the gallbladder from emptying into the small intestine.

Sudden and severe pain in the upper right section of the abdomen may be a symptom of a gallbladder attack. The pain can last just a few moments, or it can go on for hours. Pain in the upper back and the area of the right shoulder can also occur during a gallbladder attack. Urine may turn a dark yellow color, and the attack may be accompanied by nausea, vomiting and profuse sweating.

The most common treatment for a gallbladder attack is surgery. That’s because -- even when symptoms recede -- the stones are still there. This raises the risk of another blockage, infection and even rupture. The good news is that most gallbladder surgeries are now done laparoscopically, meaning that instead of an abdominal incision and an “open” surgery that can result in a weeklong hospital stay, the procedure is done with instruments and a camera that are introduced into the abdomen via small incisions. Patients typically leave the hospital in 24 to 48 hours, and are fully recovered in about two weeks.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)