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UTIs in Women

The Most Common Causes

(What You Should Know)

In most cases, that is in about 80 percent in adult women, urinary tract infection is caused by a variety of infectious bacteria (pathogens) normally present in the intestines, especially in the colon. Nearly all infections of the lower urinary tract and bladder are caused by a few strains of E. coli bacteria, called uropathogenic Escherichia coli (UPEC).

A variety of other Enterobacteriaceae and Gram-positive pathogens, includes:

Staphylococcus aureus

Staph aureus is present in up to 25 percent of healthy people. This type of bacterium is commonly found on the skin and hair as well as in the noses and throats of people and animals. It is a common cause of urinary tract infections among people with urinary tract catheterization. Staph aureus is also a known cause of nosocomial urinary tract infections that are acquired and contracted within a hospital environment. Transmission usually occurs via healthcare workers, patients, hospital equipment, or interventional procedures. Urinary tract is one of the most common sites of infection.

Unfortunately, there is an increasing incidence of multi drug-resistant (MDR) pathogens causing hospital-acquired infections. This rise can be explained by indiscriminate use of antibiotics and lacking hygiene measures, especially among medical staff. Methicillin-resistant Staphylococcus aureus (MRSA) is one the commonly seen multidrug-resistant pathogens. Although not considered to be a sexually transmitted infection, Staph aureus is something that can be passed from skin to skin contact.

Staphylococcus saprophyticus

This pathogen is the cause of 5 to 15 percent cases of urinary tract infections.

Group B streptococcus

It can be found in the digestive tract, urinary tract, and genital area of adults.

Chlamydia trachomatis

One of the most common causes of bladder infection, especially urethritis.

Pseudomonas aeruginosa

Pseudomonas aeruginosa is a common bacterium found in soil, water, skin flora and most man-made environments. An opportunistic pathogen of immunocompromised individuals vulnerable to infections, it typically infects he urinary tract.

P. aeruginosa appears to be among the most adherent of common urinary pathogens to the bladder uroepithelium. An infection can occur via an ascending or descending route.

It can also invade the bloodstream from the urinary tract. This route is the source of approximately 40 percent of P. aeruginosa infections.

This bacterium is also the third leading cause of hospital-acquired urinary tract infections, accounting for approximately 12percent of all infections of this type. They are usually related to urinary tract catheterization, instrumentation or surgery.

As a highly relevant opportunistic pathogen, P. aeruginosa has low antibiotic susceptibility. It is naturally resistant to a large range of antibiotics and may demonstrate additional resistance after unsuccessful treatment.

Therefore, choosing an antibiotic should be guided according to antibiotic susceptibility test (AST), rather than empirically. By exposing P. aeruginosa to a variety of antibiotics, it helps to decide which one should be prescribed for this particular infection.

Other common pathogens include

  • Mycoplasma hominis,
  • Klebsiella pneumoniae,
  • Enterococcus faecalis,
  • Proteus mirabilis.

These bacteria tend to remain limited to the urethra and reproductive system. Unlike E. coli, they are sexually transmitted. They are usually related to urinary tract catheterization, instrumentation or surgery.

Other possible causes of urinary tract infections include:

  • yeast infection, especially if taking antibiotics for repeated infections,
  • allergies, mainly from foods,
  • stress and anxiety,
  • sexual intercourse (it is common to get UTI’s after having sex; therefore, wiping off with antibacterial wipes or washing with soap and water before and after sex is recommended),
  • lubricated condoms (due to sensitivity to the spermicides),
  • heavy metal toxicity,
  • poor kidney function.

Uropathogenic E. Coli Infection

Various harmless strains of uropathogenic E. coli (UPEC) are normally present in the body – but they do not belong in the urinary tract. These bacteria, however, have multiple little hairs called cilia that function like little feet that allow them to climb from the skin around the vagina, up the urinary tube (urethra), into the bladder.

If E. coli bacteria get into the bladder or the urethra, the body has ways of fighting them off. They include the obvious methods of simply flushing them out with the urine. But these bacteria have evolved ways of anchoring themselves to the cells of the urinary tract.

The pathogenic invaders take advantage of receptors naturally found on the cells of the mucosal lining of the urinary tract. These receptors are like molecular “docking bays” for substances which the cells need for their normal growth and development.

E. coli use “grappling hooks”, called type I pili, to first hook on to these receptors, and then to invade the cell. These pathogenic “grappling hooks” are composed of long, fibrous chains of a molecular “glue” called adhesin.

Once inside the cell, E. coli can live and reproduce in safety, shielded from many of the body’s defensive immune responses. In fact, they are so sophisticated that when the body detects that cells have been infected and activates the cell suicide program to destroy the bacteria, E. coli can actually flee the dying host cell before it is flushed out, and look for new cells to invade!

Survival Rate of E. Coli

E. coli return in as many as 30 percent of women apparently “cured” by antibiotics! They are able to survive an antibiotic treatment by reverting to an inactive state.

Within several days of antibiotic treatment, the number of bacteria reproducing can drop to zero. Not all the bacteria are killed, though. About 3 percent of the bacteria may be still present in a dormant state after treatment with ciprofloxacin (Cipro). About 7 percent may linger after treatment with trimethoprim-sulfamethoxazole (Bactrim-Septra).

Even after a month of antibiotic exposure, about 10 million of the original 1 billion bacteria may remain.

Antibiotic-Resistant Strains of E. Coli

A newly identified, antibiotic-resistant strains of a common E. coli bacterium are contributing to an increase in relatively hard-to-treat bladder infections in women.

The analyzed strains, resistant to Bactrim-Septra, a popular two-drug combination, show a pattern of resistance to multiple antibiotics. They have genetic characteristics called “virulence factors” that increase their ability to infect the urinary tract.

Not much is known about how new strains of bacteria that infect the urinary tract arise and spread. There is also no evidence that the new strains of E. coli are causing any increase in kidney infections or other serious complications. It could be that these organisms have been around forever and have now acquired resistance to several antibiotics. They could have been introduced, perhaps through contaminated food.

E. coli-Contaminated Chicken Can Cause UTIs

Many women have long blamed their sex life for those painful urinary tract infections, but they also might need to blame the chicken meat. It turns out, eating E. coli-contaminated chicken can cause UTIs, according to a study published in the journal Emerging Infectious Diseases (April 2014).

In the study, scientists tested 320 samples of beef, pork, and chicken for the nasty strain of E. coli bacteria that is usually responsible for UTIs, mainly from transfer from the anal region to the urethra. They discovered that the E. coli strains from chicken are genetically similar to those that cause human UTIs. Uh oh!

How to reduce your risk?

As the study’s researchers blame improper food handling for food-borne UTIs, we can minimize our chances of developing an E. coli infection by:

  • Washing your hands. Clean your hands thoroughly (at least 25 seconds!) after using the bathroom and before food preparation.   
  • Cooking meats thoroughly. Use a meat thermometer to ensure chicken is cooked to an internal temperature of at least 165°F (74°C).      
  • Preventing cross contamination. Be sure to thoroughly wash your hands, counters, cutting boards, and utensils after they come in contact with raw meat.

Chlamydia Infection

Chlamydia is a common sexually transmitted disease caused by a bacterium called Chlamydia trachomatis. In women, the chlamydia organism infects cells of the lining of the cervix, rectum, and eye. Persons with chlamydia infections often have no symptoms. Consequently, they may transmit the infection to other people without knowing it.

However, when the symptoms do occur, their type and severity will depend on the site of the infection and the person’s response to it. Women who do have symptoms of chlamydia infection may notice:

  • an increased vaginal discharge,
  • irritation of the area around the vagina,
  • burning pain with urination.

To diagnose chlamydia, a special test must be done by a health professional. As this is a serious condition, it requires prompt medical attention and is easily treated with an antibiotic medication.

Pelvic Inflammatory Disease

If not detected and treated, chlamydia can lead to a pelvic inflammatory disease. It is a signal that the infection has spread to the uterus and fallopian tubes.

Symptoms of pelvic inflammatory disease include:

  • lower abdominal pain,
  • painful intercourse,
  • irregular periods,
  • spotting and
  • fever.

In pregnant women, chlamydia infection can be passed on to their newborn children, where it can cause eye infections and pneumonia.


Although 25 percent of all hospitalized patients will receive a catheter at some point in their stay, nearly 1 out of every 3 patients undergoing catheterization does not need it! That much of this overcatheterization may be due to the fact that it makes the jobs of hospital staff easier.

However, once inserted, the devices often remain too long because doctors either forget or do not know which of their patients still have a catheter inserted.

Catheters are considered necessary for patients who are:

  • bed-ridden,
  • incontinent or unable to control urine flow,
  • in post-operative recovery,
  • diagnosed with a bladder obstruction (for example, due to an enlarged prostate),
  • in need to have their urine levels observed.

Unfortunately, every day a catheter is left in, a patient has a 5 percent chance of developing a urinary tract infection, as bacteria from the patient’s genital area – in most cases pathogenic E. coli bacteria – migrate up the outside of the catheter and infect the otherwise sterile bladder.

Usually treated with antibiotics, the urinary tract infections have the potential to lengthen hospital stays and cause more serious side effects that can be life threatening (when infection spreads to the bloodstream).

For this reason, researchers are calling for a mandatory “stop-order” on all hospital catheterizations after 48 hours, with a daily review thereafter. The incidence of UTIs is reduced, however, if silver alloy catheters are used.

Repeated Bladder Infections

Most likely women over the age of 55 years or between the ages of 25 and 29 are more prone to repeated infection. For most of them, it can be a painful and frustrating battle.

Women who have had three of more UTIs a year are likely to continue having them. It means that they can get another infection within 18 months of the last one, or even more frequently.

One possible factor behind recurrent urinary tract infection may be the ability of bacteria to attach to cells lining the urinary tract. The symptoms sometimes can be caused by chemical irritation, such as bath additives and washing powders. They may disappear, if toiletries and washing powder are changed.

Usually, the latest infection stems from a strain or type of bacteria that is different from the infection before it, indicating a separate infection. Even when several urinary tract infections in a row are due to E. coli, slight differences in the bacteria indicate distinct infections.

Antibiotic treatment does not successfully kill all the bacteria participating in the infection.

In fact, it may encourage many of the bacteria to persist in a resting state. Therefore, current standard drug treatments for bladder infections are not adequate and this phenomenon may account for many of the repeat urinary tract infections.

Some women, however, have recurrent symptoms suggestive of urinary tract infection – but without actual infection being present. This condition is not serious, but can be troublesome.

Chronic or recurrent urinary tract infections should be treated thoroughly because of the chance of kidney infection (pyelonephritis).


Trapped in a Vicious Cycle of Repeated Infections?

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