Asymptomatic Bacteriuria: The Question for Treatment
Submitted by Jennie Gunn, PhD, FNP, CTN-A
To improve the quality of care for adult patients with asymptomatic bacteriuria by preventing unnecessary antibiotic intake, antimicrobial side effects, possible risk for drug resistance, and by avoiding medication-related costs.
Literature search included Cochrane, MedlinePlus, Cumulative Index to Nursing and Allied Health Literature, journal of Clinical Infectious Disease from 2005 to 2013, and the Infectious Disease Society of America guidelines.
Asymptomatic bacteriuria is common in patients who have diabetes, in elders who are institutionalized, in patients who have had a kidney transplant, in pregnant women, in women who are menopausal, in patients who have undergone urologic procedures, and in patients who have indwelling catheters. Treatment of asymptomatic bacteriuria is not recommended by the Infectious Disease Society of America except for pregnant women to prevent infants from being born at low birth weight.
Implications to Practice
Quality clinical interventions require the assessment of patients with asymptomatic urinary tract infections to make a sound decision whether to apply additional screening such as urine culture. The goal is to treat patients with asymptomatic bacteriuria appropriately. Evidence-based patient- centered care promotes patient safety.
Treatment of ASB is not recommended for patients with no apparent symptoms such as urgency, frequency, or burning on urination. In the absence of symptoms or presence of high level of bacteria, screening or treating patients with asymptomatic bacteriuria is not recommended; treating pregnant women with asymptomatic urinary infections may help prevent babies having a low birth weight.
Tags: asymptomatic bacteriuria, screening, guidelines, adults.
Asymptomatic Bacteriuria: The Question for Treatment
The number of patients with bacteriuria or urinary tract infections (UTI) is about 8.1 million per year, and this accounts for $340 million to $450 million in cost annually (United States Department of Health and Human Services, 2012; Virginia Department of Health, 2013). Not all patients with positive urinalysis for leukocytes are symptomatic. In some adult patients, significant numbers of bacteria may be colonized in the urinary tract with no apparent symptoms such as frequency, urgency, and burning on urination. Treatment of patients with asymptomatic UTI, who may not have enough bacteria to be considered infective, may subject patients to unnecessary antimicrobial treatment. Bringing clinical nursing practice, in line with evidence- based guidelines, promotes quality patient-centered care and prevents inappropriate treatment of asymptomatic bacteriuria (ASB) that may lead to unnecessary antibiotics side effects such as nausea and diarrhea along with possible resistance to certain pathogens. The purpose of the article is to increase the awareness of nurses and nurse practitioners regarding the physical and financial burden along with antimicrobial resistance caused by unnecessary treatment of ASB.
When female patients arrive to the clinic for a yearly exam, a urine sample is often collected as part of the laboratory work up. A routine urinalysis (UA) will reveal many things about the patient’s health and is a relatively inexpensive test which includes specific gravity, pH, glucose, protein, bilirubin, urobilinogen, nitrites, leukocyte esterase, blood, and ketones (Ariathianto, 2011). When the indicators do not fall within the normal range of leukocytes or a high level of bacteria is present, this indicates a condition described as bacteriuria or UTI exists.
When the patient has no symptoms of UTI, yet the urinalysis is positive for leukocytes, ASB may be present.
Defining Asymptomatic Bacteriuria
One indicator of a potential problem is the bacterial level in the urine. Bacterial numbers in the urine are often a high enough level to cause symptoms; this may come as a surprise to the woman who is asymptomatic. ASB is a concern for the clinician, because ASB is associated with genitourinary abnormalities, pregnancy, diabetes, older age, spinal cord injuries, immunocompromised patients, increased sexual activities in young women, and post menopause (Bryan, 2011). The presence of bacteria without symptoms may be a sign of an inflammatory process in the genitourinary tract that may be attributed to sexually transmitted diseases, renal calculi, vaginal contamination, and colonization. The presence of non-nitrite producing bacteria or a lack of sufficient time for the bacteria to produce nitrites because of the rapid flushing of the bladder might be another reason to consider ASB (Colgan, Nicolle, McGlone, & Hooton, 2006). Contributing factors to a false positive ASB in the urinalysis include a delay in testing of the
urine sample from the time that it was obtained or that the urine sample was left at room temperature which can cause the bacteria to multiply every 20 minutes (Colgan, et al., 2006).
Asymptomatic bacteriuria is defined by the Infectious Diseases Society of America ([IDSA], 2005) as two consecutive clean catch urine samples with the same bacterium in quantitative counts of equal or more than 100,000 colony forming units (cfu/ml) (Bryan, 2011). The most common organism is Escherichia (E) coli; however, E. coli found in patients with ASB is less virulent in its ability to cause symptoms. ASB is more prevalent in females, postmenopausal women, patients who are in long term care facilities, patients with mental changes, and in presence of comorbidities. ASB which is non-virulent varies with age:
prevalence in schoolgirls is one percent and in women aged 80 years and over is 20 percent (Dalal, Nicolle, Marrs, Zhang, Hardy, & Foxman, 2009; Yacoub & Akl, 2011). Seventy six percent of ASB cases resolve by themselves, because trace or few leukocytes in the UA test is not a diagnosis for UTI in an asymptomatic patient, but might be an inflammatory process in the genitourinary tract such as vaginitis (Eke, Akarolo-Anthony, Enumah, 2012; Dalal, et al., 2009).
Symptomatic Versus Asymptomatic
Consider the patient who comes to the clinic for a yearly wellness exam. When the urinalysis report returns, the UA is positive for leukocytes and nitrites, negative for blood and protein. However, the patient denies painful urination, lower back pain, pelvic pain, chills, fever, history of diabetes, history of kidney stones, and the physical exam and vital signs are normal; the diagnosis is most likely ASB. Positive leukocytes and nitrites in an asymptomatic female patient is not an indication for treatment except for pregnant women to prevent pyelonephritis.
Unnecessary treatment of ASB increases antimicrobial resistance, subjects patients to antimicrobial side effects, and places a burden of unnecessary costs of antibiotics to patients (Bryan, 2011). Exploring reasons of bacterial presence in the bladder, whether it is symptomatic or asymptomatic, is important. In symptomatic bacteriuria or UTI, urine culture bacterial counts are greater than 100,000 cfu/ml of urine; this means there is a 10% chance to cause complications such as pyelonephritis (Colgan, Nicolle, McGlone, & Hooton, 2006). Other causes that are worth to explore in patients with ASB are women with cystocele, an enlarged kidney due to an obstruction such as kidney stone, post genitourinary surgery, and patients with indwelling catheter (Colgan, Nicolle, McGlone, & Hooton, 2006).
Recommendations for Asymptomatic Bacteriuria
Human urine has antibacterial agents such as acids, urea, short carbohydrate chains, and salts that protect the urinary tract from bacteria unless there are physiological or physical changes such as old age, pregnancy, increased glucose in urine in diabetes, changes in estrogen level such as in women who are postmenopausal, and immune-related changes in patients who are immunocompromised (Freeman, 2010).
Screening or treating ASB is not recommended for patients with diabetes, patient who are elderly, women who are postmenopausal, or patients who are immunocompromised (Bryan, 2011). However, 30-40% of pregnant women, if left untreated, may develop pyelonephritis and may have low birth infants (IDSA, 2005). Screening the first trimester of the pregnancy for microorganisms and treating the bacteria is recommended by IDSA to prevent complications such as pyelonephritis. Untreated ASB is associated with low birth weight, intrauterine growth retardation, and premature labor. Physiologic and physical changes in pregnancy that contribute to ASB are decreased bladder tone that cause urinary stasis, increased progesterone level, increased glomerular filtration rate due to increased kidney length, smooth muscle relaxation, displacement of the bladder due to uterine enlargement, and glucose excretion which is 100 times higher in pregnant women causing bacterial growth in the bladder.
Asymptomatic Bacteriuria Risk Factors in Patients with Diabetes
Patients with diabetes are prone to ASB six to 24 times more than non-diabetic patients, because high concentration of glucose in the bladder allows microorganisms to multiply (Jepson, Mihaljevic, & Craig, 2010). Prevalence of ASB depends on the duration of diabetes, glucosuria, bladder neuropathy, and possible colonization of the bacteria. Antibiotics do not eradicate the bacteria in patients with diabetes, and often, ASB does not cause any harm if left untreated. According to IDSA, screening and treating ASB patients with diabetes is not recommended; however, urine culture is recommended in patients with diabetes diagnosed with ASB with risk factors such as microalbuminuria which may progress to renal failure. Asymptomatic UTI may be a possible cause for microalbuminuria. Carter, Tomson, Stevens, and Lamb (2006) recommend urine culture to exclude UTI.
Patients who are Elderly
ASB is more prevalent in older age, at a rate of 13- 22.4%, and in long term care residents, at 25-50%, mostly due to urethral contamination from the gut by the microorganism E. coli (Midthum, 2004; Mulryan, 2011). In older women, ASB is common due to incomplete emptying of the bladder resulting in multiple organisms in the bladder. Other causes are contamination, fistulas, or kidney stones (Midthum, 2004). Risk factors for ASB include Parkinson’s disease, cognitive impairment, Alzheimer’s, cerebrovascular disease, patients with indwelling catheters, patients having urinary tract calculi, low estrogen levels, and patients who have abnormal genitourinary tract (Midthum, 2004). Risk factors that need monitoring to prevent complications are infections caused by urea-splitting organisms such as Pseudomonas or Proteus microorganisms that may cause stones in the urinary tract if left untreated (Mulryan, 2011).
Menopause is a normal change in older women, but symptoms caused by estrogen deficiency are a concern to female patients due to vaginal dryness, dysuria, irritation, and itching. The physiologic changes such as vaginal tissue atrophy, increased vaginal pH, decreased blood flow, and shortening of the vagina contribute to ASB (Nicolle, Bradley, Colgan, Rice, Schaffer, & Hooton, 2005). Bacteriuria in postmenopausal women, which is caused by a contaminant, is usually due to low estrogen levels. In low estrogen levels, there is no need to treat with antimicrobials, but instead oral or vaginal estrogen may reverse tissue atrophy associated with menopause after three to six months (Perrotta, Aznar, Meja, Albert, & Ng, 2008). Risk factors for ASB in postmenopausal women include a history of urinary incontinence, presence of cystocele, and recent sexual intercourse. Screening for and treatment of asymptomatic bacteriuria in premenopausal is not recommended (IDSA, 2005).
Patients who are Immunocompromised
Prevalence of ASB in patients with Human Immunodeficiency Virus (HIV) and patients who undergo kidney transplant is increased due to the low immunity status. Screening and treatment of ASB patients with HIV is not recommended by IDSA (2005), because there are no reported beneficial outcomes in treating immunocompromised patients, and there are very limited studies on patients with HIV diagnosed with ASB (Colgan, Nicolle, McGlone, & Hooton, 2005).
The highest prevalence of ASB among patients who are immunocompromised from kidney transplant medication is in the first six months after surgery. Urinary tract infections in patients who are immunocompromised from kidney transplant treatment are usually asymptomatic and, if not treated, may lead to pyelonephritis and bacteremia. ASB-related mortality rate in immunocompromised patients is 11% post kidney transplant surgery (Nicolle, et al., 2005). However, patients who have had a kidney transplant are usually on long-term antimicrobial administration and that may prevent infections such as UTI’s. IDSA (2005) recommends not screening or treating ASB in patients undergone kidney transplants because they are protected due to life-long prophylaxis.
The Decision to Treat
According to IDSA (2005), management of ASB is exclusive to pregnant women; antimicrobial treatment for ASB in the elderly, non-pregnant women, postmenopausal women, post kidney transplant, patients with diabetes is not indicated. Unnecessary ASB treatment may cause patients harm such as antibiotic adverse effects and possible development of bacterial resistance, plus cost of the medication. Leukocytes presence in the urine does not indicate infection: presence of bacteria in the urine might be due to sexually transmitted diseases, renal calculi, vaginal contamination, colonization, presence of non-nitrite producing bacteria, or lack of sufficient time for the bacteria to produce nitrites because of the rapid flushing of the bladder (Colgan et al., 2006). The provider should inquire thoroughly about patient’s history to provide safe and patient-centered care (Zalmanovici-Trestioreanu, Lador, Sauerbrun-Cutler, & Leibovici, 2012). Informing patients to return to the clinic in case there is any change such as fever, chills, blood in the urine, vaginal discharge, and low flank pain are important in providing safe quality care.
Whether to treat or not treat patients presenting with positive UA for leukocytes, ASB is an issue to providers; it is a challenge to inform the patient that there are bacteria in the urine, but there is no need to treat it. Reassuring patients with ASB and then determining if further urine culture is needed are important to promote patient safety. Treatment of ASB is not recommended for patients with no apparent symptoms such as urgency, frequency, or burning on urination. In the absence of symptoms or the presence of high levels of bacteria, screening or treating patients with asymptomatic bacteriuria is not recommended; treating pregnant women with asymptomatic urinary infections may help prevent babies having a low birth weight.
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