Various Risk Factors Of Asymptomatic Bacteriuria Biology Essay

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Various Risk factors of Asymptomatic Bacteriuria with diabetes have been suggested including age, sexual intercourse, duration of metabolic control, and complications of diabetes[3].

Asymptomatic Bacteriuria is defined as the presence of at least 105 colony forming units/ml of 1 or 2 bacterial species in a culture of clean voided mid stream urine from an individual without symptoms of urinary tract infection[4].

Contaminated urine is defined as the presence of at least 3 different micro organisms in 1 urine specimen. On microscopic examination ≥ 1 bacterium / oil immension field on gram staining of unspun, freshly voided urine correlated well with ≥ 105 colony forming units/ml on culture. ≥ 10 leucocytes/mm3 from a clean catch midstream urine sample correlated well with ≥ 105 colony forming units/ml on culture[6].

Asymptomatic bacteriuria is not a separate entity, but an early stage in the course of natural history of urinary tract infection[5].

Asymptomatic Bacteriuria is common in neonates, preschool children, pregnant women, elderly people, diabetics, catheterized patients, patients with abnormal urinary tracts or renal disease. Specifically asymptomatic bacteriuria occurring in DM can cause serious complications like renal and perirenal abscess, gas forming infections such as emphysematous pyelonephritis, and renal papillary necrosis[6].

Though there is no consensus on treatment of Asymptomatic Bacteriuria in various population groups, it was recommended to treat asymptomatic bacteriuria in diabetes mellitus, so as to avoid in the future Asymptomatic Bacteriuria going for symptomatic bacteriuria or complications due to Asymptomatic Bacteriuria[7].

Initially the United States preventive task force recommended periodic testing for asymptomatic bacteriuria in diabetes, pregnant women, pre school children and in persons over age 60 yrs. In general dipsticks combining the leucocyte esterase and nitrite tests should be used to detect Asymptomatic Bacteriuria. However urine culture is a more accurate test than dipstick analysis[8].

However, recently [IDSA] Infectious Disease Society of America came out with a guide lines with no necessity to screen or treat ASB in diabetes patients.

Aims and Objectives

To study the incidence of Asymptomatic Bacteriuria in Diabetes Mellitus patients presenting to a teaching hospital in Puducherry.

To identify the causative organisms responsible for Asymptomatic Bacteriuria in Diabetes Mellitus Patients.

To detect the organisms by urine culture & grams stain.

To study the precipitating factors for Asymptomatic Bacteriuria

Asmptomatic Bacteriuria in non diabetes individuals.

Comparative study between these two patient groups.

The functional unit of the kidney is the nephron. Each human kidney contains about 0.6 Ã- 106 to 1.4 Ã- 106 nephrons, which contrasts with the approximately 30,000 nephrons in each adult rat kidney. The essential components of the nephron include the renal or malpighian corpuscle (glomerulus and Bowman's capsule), the proximal tubule, the thin limbs, the distal tubule, and the connecting tubule. The origin of the nephron is the metanephric blastema. Although there has not been universal agreement on the origin of the connecting tubule, it is now generally believed to derive from the metanephric blastema. The collecting duct system, which includes the initial collecting tubule, the cortical collecting duct (CCD) in the medullary ray, the outer medullary collecting duct (OMCD), and the inner medullary collecting duct (IMCD), considered part of the nephron because embryologically it arises from the ureteric bud. However, all of the components of the nephron and the collecting duct system are interrelated functionally.

Two main populations of nephrons are recognizable in the kidney: those possessing a short loop of Henle and those with a long loop of Henle . The loop of Henle is composed of the straight portion of the proximal tubule (pars recta), the thin limb segments, and the straight portion of the distal tubule (thick ascending limb, or pars recta). The length of the loop of Henle is generally related to the position of its parent glomerulus in the cortex. Most nephrons originating from superficial and midcortical locations have short loops of Henle that bend within the inner stripe of the outer medulla close to the inner medulla. A few species, including humans, also possess cortical nephrons with extremely short loops that never enter the medulla but turn back within the cortex. Nephrons originating from the juxtamedullary region near the corticomedullary boundary have long loops of Henle with long descending and ascending thin limb segments that enter the inner medulla. Many variations exist, however, between the two basic types of nephrons, depending on their relative position in the cortex. The ratio between long and short loops varies among species. Humans and most rodents have a larger number of short-looped than long-looped nephrons

The urinary system or urinary tract is the organ system that produces, stores, and eliminates urine. In humans it includes two kidneys, two ureters, the bladder and the urethra. The female and male urinary system are very similar, they differ only in the length of the urethra.

The kidneys are bean-shaped retroperitoneal organs that lie in the  posterior abdomen. These organ lie in the extraperitoneal connective tissue and situated lateral to vertebral column , just below the rib cage, surrounded by Peri-nephric fat. On the superior pole of each kidney an adrenal gland is situated. The kidneys receive nearly 25% of the cardiac output as their blood supply at a rate of 1.25 L/min from the renal arteries branching from abdominal aorta. Thev main role of kidneys is to filter water soluble waste products from the blood. kidneys are attached to the ureters, which lies more medial and runs down to reach the trigone of urinary bladder. The tasks performed by the kidneys are concentrating urine, regulating electrolytes, and maintaining the homeostasis of acid and base. The kidney excretes and re-absorbs electrolytes like sodium, potassium and calcium under the influence of local and systemic hormones. pH balance is regulated by the excretion of  bound acids and ammonium ions. In addition, they also perform other actions such as removing urea which is a nitrogenous waste product from the metabolism of amino acids. The end product is a hyper osmolar solution carrying waste which is stored in the bladder before urination.

Humans produce about 2.9 litres of urine over 24 hours, according to circumstances to the amount may vary. Since the rate of filtration at the kidney is proportional to the glomerular filtration rate, which in turn is related to the flow of blood through the kidney and the changes in body fluid status can affect kidney function. Exogenous and endogenous hormones to the kidney alter the amount of blood flowing through the glomerulus. 

diabetes mellitus

Diabetes mellitus, is a group of metabolic disease characterized by high blood sugar, due to either of the factors such as decreased insulin secretion, reduced utilization of glucose, and increased production of glucose.

DM is associated many other pathologic changes in our multiorgan system like ESRD, CAD etc.,

DM is one of the leading cause of morbidity and mortality in the entire world.

Globally, as of 2012, an estimated 346 million people have type 2 diabetes

Globally, as of 2010, an estimated 285 million people had diabetes, with type 2DM ocupying about 90% of the cases.The incidence of DM increases rapidly, and it is estimated to almost double by the year 2030. Diabetes mellitus occurs throughout the world, but is more common in the more developed countries .The International Diabetes Federation says that atleast 438 million individuals will have diabetes at the end of 2030. Eventhough the prevalence of both the types 1 & 2 DM is increasing worldwide, the prevalence of type 2 DM is increasing much more severely than type 1 because of increasing obesity, reduced physical activity ,change in eating habits and the aging of the population.The increase in incidence in developing countries due to urbanization and change in lifestyle.


India has more diabetics than any other country in the world, according to the International Diabetes Foundation. The disease affects nearly 50 million Indians,comprising about 7.1% of the nation's adults and about 1 million deaths a year. The average age of onset is 42.5 years. This high incidence is due to to a combination of factors like genetic susceptibility, intake of a high-calorie diet, low-activity lifestyle mainly by India's growing middle class.


Type 1

Type 1 DM is caused by the pancreatic beta cell destruction and deficiency of insulin due to interactions of genetic, environmental, and immunologic factors . some individuals are develop insulin deficiency by unknown mechanisms. Individuals who have a normal genetic susceptibility initially have a normal beta cell mass at birth but later they begin to lose the beta cells within months to years due to autoimmunity. This autoimmune process is triggered by an infection environmental factors . In most of the individuals, immunologic markers appear before diabetes becomes clinically overt but mainly after the triggering event. Insulin secretion progressively declines due to decrease in size of the beta cell mass. Although the glucose tolerance is maintained at a normal rate. The rate at which the beta cell mass declines widely varies among individuals, with some individuals with a tendency to progress rapidly to clinical diabetes while in others it evolves more slowly. In nearly 70-80 percent individuals diabetic features do not become evident until most of the beta cells are destroyed Though residual functiona of the beta cells exist they are insufficient i to maintain the glucose tolerance. The events such as puberty, infection etc., triggers the conversion from glucose intolerance to overt diabetes which are then associated with increased requirement of insulin.

Type 2

Insulin resistance and abnormal insulin secretion are the reasons to the development of type 2 DM. Although there are many controversies in this, most studies favour that insulin resistance occur prior to an insulin secretory defect, but diabetes develops only when secretion of insulin is not adequate. Type 2 DM most likely holds a range of disorders with a common phenotype of hyperglycemia. DM in other ethnic groups like as in Asian, African, and Latin American has a different, but yet undefined, pathophysiology than others. In these groups, DM that is ketosisprone who are often obese or ketosis-resistant who are often lean is commonly seen.


It depends on the type.

Type 1 diabetes is partly inherited and triggered by certain infections and environmental factors

The onset of

Type 1 diabetes is unrelated to lifestyle.

Type 2 diabetes is primarily due to lifestyle factors and genetics.

1.Type I



2. Type II


A. Genetic mutations [ MODY 1 - MODY 6]

* Mitochondrial

* Subunits in ATP sensitive potassium channel

* pro insulin or insulin

B. Genetic defects in insulin action

* Type A insulin resistance

* Leprechaunism

* Rabson-Mendenhall syndrome

* Lipodystrophy syndromes

C. Diseases of the exocrine pancreas




* hemochromatosis

*cystic fibrosis

* fibrocalculous pancreatopathy

* mutations in carboxyl ester lipase

D. Drug or chemical-induced


* vacor -a rodenticide

* pentamidine

* diazoxide

* nicotinic acid

* adrenergic agonists

* thiazides

* hydantoins

* protease inhibitors

* asparaginase

* interfero

* antipsychotics

* epinephrine




*Cushing's syndrome


* hyperthyroidism

* somatostatinoma

* aldosteronoma

F. Infections

*congenital rubella

* cytomegalovirus

* coxsackievirus

G. Uncommon forms of immune-mediated diabetes

*stiff-person syndrome

* anti-insulin receptor antibodies

H. Other genetic syndromes sometimes associated with diabetes

* Wolfram's syndrome

* Down's syndrome

* Turner's syndrome

* Klinefelter's syndrome

* Friedreich's ataxia

* Prader-Willi syndrome

* Huntington's chorea

* myotonic dystrophy

* porphyria

* Laurence-Moon-Biedl syndrome


The classical symptoms of untreated diabetes are loss of weight, polyuria (frequent urination), polydipsia (increased thirst) and polyphagia(increased hunger). Symptoms may develop rapidly (weeks or months) in type 1 diabetes, while they usually develop much more slowly and may be subtle or absent in type 2 diabetes.

Other symptoms are

- blurred vision

- gastroparesis

- peripheral neuropathy

- loss of libido

- hyperpigmentation and skin rashes




<7.8 (<140)

<6.1 (<110)


Impaired fasting glycaemia

<7.8 (<140)

≥ 6.1(≥110) & <7.0(<126)


Impaired glucose tolerance

≥7.8 (≥140)

<7.0 (<126)


Diabetes mellitus

≥11.1 (≥200)

≥7.0 (≥126)


Diabetes mellitus is characterized by recurrent or persistent hyperglycemia, and is diagnosed by demonstrating any one of the following:

Fasting plasma glucose level ≥ 7.0 mmol/l (126 mg/dl)

Plasma glucose â‰¥ 11.1 mmol/l (200 mg/dL) two hours after 75 g oral glucose load as in a glucose tolerance test

Symptoms of hyperglycemia and casual plasma glucose ≥ 11.1 mmol/l (200 mg/dl)

Glycated hemoglobin (Hb A1C) ≥ 6.5%

A positive result, in the absence of unequivocal hyperglycemia, should be confirmed by a repeat of any of the above methods on a different day. According to the current definition, two fasting glucose measurements above 126 mg/dl (7.0 mmol/l) is considered diagnostic for diabetes mellitus.

Glycated hemoglobin is better than fasting glucose for determining risks of cardiovascular disease and death from any cause.


Diabetes mellitus increases the risk of long-term complications which typically develop after many years nearly 10 - 20 years. It may be the first symptom in some who have not been diagnosed before .


DKA[ diabetic ketoacidosis]

HHS[ hyperglycemic hyperosmolar state]




1. retinopathy

2. neuropathy

3. nephropathy


1.coronary heart disease (CHD)

2. peripheral arterial disease (PAD)

3. cerebrovascular disease


1. Gastroparesis

2. Infections

3.Skin changes

4. Hearing loss.

5. Sexual dysfunction

6. Cataracts

7. Glaucoma

8. Periodontal disease

Diabetic emergencies

Diabetic ketoacidosis

DKA occurs due to relative or absolute insulin deficiency combined with excess counter regulatory hormones like glucagon, catecholamines, cortisol, and growth hormone. Both insulin deficiency and glucagon excess, are necessary for development of DKA.

Hyperglycemic hyperosmolar state

HHS occurs due to relative insulin deficiency or inadequate fluid intake. Insulin deficiency increases hepatic glucose production mainly through two process such as glycogenolysis and gluconeogenesis which glucose utilization in skeletal muscle impaired. Hyperglycemia induces an osmotic diuresis that leads to depletion of intravascular volume and this is further exacerbated by inadequate fluid replacement. The cocept why ketosis is absent in HHS is not clearly understood.


The goals of therapy for type 1 or type 2 DM are to

(1) eliminate symptoms related to hyperglycemia,

(2) reduce or eliminate the long-term microvascular and macrovascular complications of DM, and

(3) allow the patient to achieve as normal a lifestyle as possible.

To reach these goals, the physician should identify a target level of glycemic control for each patient, provide the patient with the educational and pharmacologic resources necessary to reach this level, and monitor/treat DM-related complications.


- oral hypoglycemic agents

- insulin


Epidemiologically, urinary tract infections are sub-divided into catheter associated or nosocomial infection or non catheter associated community acquired infections. Infections in either category may be symptomatic or Asymptomatic. Acute community infections are very common and account for more than 7 million Hospital visits annually in the united states. There infections occur in 1-3% of school girls and then increased markedly in incidence with the onset of sexual activity in adolescence. The vast majority of acute infections involve women. Acute symptomatic Urinary Tract Infection's are unusual in men under the young age group of 50 yrs. The development of asymptomatic bacteriuria parallels that of symptomatic infections and in rare among men under 50 years but common among women between 20 and 50 years. Asymptomatic bacteriuria is more among elderly men and women with rates as high as 10-50% in some studies.

Causative organisms of Urinary Tract Infection's are the most common organism are Gram Negative Bacilli

Escherichia coli - 70-80%

Klebsiella - 2-3%

Proteus - 2-4%

Enterococcus - 1-2%

Gram positive cocci

Staphylococcus saprophyticus - 10-15%

More commonly serratia and pseudomonas are known to cause recurrent infections and also in infections which are associated with urological manipulation, calculi or obstruction.

Proteus species and klebsiella species by virtue of urease production and through the production of polysaccharides and extracellular slime predispose to formation of stone and more frequently in patients with calculi.

Chlamydia trachomatis, Neisseria gonorrhea, and herpes simplex virus are most frequently found in sexually active young women .

The causative role of non-bacterial pathogens in Urinary Tract Infection's remains poorly defined. Ureaplasma urealyticum has been frequently isolated from t urine of patients with acute dysuria and increased frequency but it is also found in specimens without urinary symptoms.

In patients with acute prostatitis and pyelonephritis species of mycoplasma hominis has been isolated from prostatic and renal tissues, and are probably irresponsible for some of the infections as well. Candida and other fungal infection is common and sometimes progressive to symptomatic invasive infection.

Mycobacterial infection of Urinary Tract Infection is also a common cause of Asymptomatic Bacteriuria.


The urinary tract should be viewed as a single anatomic unit that is united by a single column of urine extending from the urethra to the kidney.

Routes of Entry to the urinary tract

Ascending Infection

Mostly the infections of kidney units from organisms desired from gastrointestinal tract to the urethra and periurethra tissues into the bladder and then by the catheter to renal pelvis with subsequent invasion of renal medulla.

Hematogenous infection

Accounts for less than 3% cases of Urinary Tract Infection and pyelonephritis. The major cases of hematogenous infection are staphylococcus aureus, salmonella species, pseudomonas aeruginosa, Enterococcus faecalis

Lymphatic spread

Spread of infection along the lymphatic channels connecting bowel and urinary tract is possible.



In females the urethra is prone for gram negative bacilli infection because it is close to the perineum and its short length and its termination beneath the labia. In addition UTI due to increased colonization of E.coli has been associated due to the use of spermicidal compounds with a diaphragm or a cervical cap or of spermicide coated condoms which dramatically alters the normal introital bacterial flora . In males who are a 50 years old and who have no H/o Heterosexual or Homosexual rectal intercourse, Urinary Tract Infection is exceedingly uncommon. Men & women who are infected with HIV are at increased risk of both bacteriuria and Urinary Tract Infection. Lack of circumcision has been identified as a risk factor for Urinary Tract Infection in both neonates & young men.

Pregnancy: 2-9 of Pregnant women 20-30% of pregnant women with Asymptomatic Bacteriuria subsequently develop pyelonephritis. Catheterization during or after delivery causes additional infections.

Obstruction: Any obstruction in free flow of urine tumour, stricture, stone, or prostatic hypertrophy results in increased frequency of Urinary Tract Infection.


Dysfunction that occurs due to interference with the nerve supply to the bladder which is seen in spinal cord injury, tabes dorsalis, multiple sclerosis. Diabetes and other diseases may be associated with Urinary Tract Infection. Other additional causes due to bone demineralization are from immobilization which lead to hypercalciuria, calculus formation & obstructive uropathy.

Vesicoureteral Reflux: Anatomically impaired vesicoureteral function facilities reflux of bacteria and thus Urinary Tract Infection.


Virulence factors of E.coli - surface antigen & toxins

Somatic Polysaccharide surface 0 antigen

Exerts endotoxic activity

Protects bacillus from phagocytosis

Protects bacillus from bactericidal effects of complement.

K antigens or envelop

P fibriae binds specifically to the P blood group substance on human erythrocytes and uroepithelial cells.

The E.coli serotypes commonly responsible for Urinary tract infections are those normally found in the faces, o group 1,2,4,6,7 strains carrying K antigens are more commonly responsible for pyelonephritis.


A maternal History of Urinary Tract Infections is found more among women who have experienced recurrent Urinary Tract Infection's than among controls. It has also been demonstrated that non-secretions of blood group antigens are at increased risk of Urinary Tract Infection.


Normal flora of the vagina

Flushing effect of urine flow and voiding


Bladder glycocalyx

Tomm-horsfall glycoprotein



IgA, IgM, IgG Antibodies


Collection of midstream specimens of urine.

Suprapubic aspiration of urine

Bladder catheterisation

Collection of Midstream Urine collection specimen


Patient must have a full bladder

Retract the fore skin if present

Clean glans penis with swab

Void into toilet with foreskin retracted until half done

Without interrupting stream catch sample in sterile bottle

Complete voiding


Patient must have a full bladder

Patient removes underclothing and stands legs either side of toilet

Separate labia with left hand

Cleans vulva front to back with sterile swab

Void downward into toilet until half done

Without interrupting stream catch urine in sterile bottle

Complete voiding

The method of urine sample collection is followed because the distal urethra contains bacteria normally so voided urine is contaminated so Midstream Urine collection is done.


This method is used when it is impossible to obtain uncontaminated samples or in symptomatic patients with low bacterial counts. This method is not usually followed


Patient must have a full bladder which can be percussed if not percussible or in doubt, give 300ml of water and 20mg of furosemide orally and wait for 1 hr. If still in doubt and especially in obese subjects, localize bladder using ultrasound. When patient supine chose site in midline 2.5cm above symphysis pubis, clean skin with spirit impregnated sterile gauze. Insert a 21 gauge 1.5" needle, attached to a 10ml syringe, directly downwards and aspirate urine. Withdraw needle and collect urine local anesthetics may be used.

Bladder Catheterisation:

It is nearly unnecessary to catheterize patients for collection of urine sample because catheter may introduce infection in the bladder and results in false positive cultures.


Urine being an excellent superfine medium for growth of most bacteria, it must be plated immediately or refrigerated at 4oc. Bacterial counts in refrigerated urine remains constant for as long as 24 hrs.

BD urine culture kit, a urine transport tube containing boric acid, glycerol, sodium formate, preserve bacteria without refrigeration for as long as 24 hrs when greater than 105 CFU/ml were present in initial urine specimen.

SAGE products care of III preservative system also available.

Both above products preserve bacterial inability in urine for 24 hours in the absence of antibodies. A new lyophilized system appears to stabilize microbial population for 24 hrs in the presence of antibiotics. For population of patients from whom colony counts of organisms of less than 105 /ml might be clinically significant, planting within 2 hour collection is recommended. None of the kits have any advantage over refrigeration.


Grams stain method

One of the earliest method, It is a least expensive, the most sensitive and reliable screening method for identifying urine samples that contain greater than 10 CFU/ ml

A drop of well mixed urine is allowed to dry. The smear is gram stained and examined under oil immersion (1000 x ) . Presence of even one organism per oil immersion field after examining 20 fields correlates well with significant bacteriuria in 90% cases. The gram stain should not be relied on for detecting polymorphonuclear leucocytes in urine.


The test is based on ;the absence of nitrite in normal urine. The presence of nitrite, Detected by a simple test indicates the presence of nitrate inducing bacteria in urine. A positive test suggests the presence of atleast 105 organisms per ml of urine. This test detects Escherchia coli, klebsiella, proteus, staplylococcus, and pseudomonas species. False negative tests occurs in the presence of yeast, some gram positive cocci, urinary ascorbic acid, frequent voiding, urobilinogen.

3.Catalase test

This test depends on the generation of oxygen bubbles by catalase produced by the bacteria when hydrogen peroxide is added to the infected urine. False positive results occur in the hematuria.

4. Triphenyl Tetrazolium chloride test

The respiratory activity of growing bacteria, reduce 2,3,5 triphenlytetrazolium chloride to red insoluble triphenyl formogen false positive, false negative results are in the range of 5-10%. This test not used widely.

Glucose oxidase test

Depends on the bacterial metabolism of glucose normally present in urine. In the presence of infection glucose is not detected. False negative tests occur with high urine low rather and frequent voiding, an infected urine must be present in the bladder for some 1 hour before the glucose is metabolized completely. False positive results occur in glycosuric patients.

6.Leucocyte esterase test

This test detects the presence of pyuria by measurement of esterase activity within leucocytes, even in ;the absence of intact neutrophils. On its own it is relatively sensitive. However this test has been combined with griess test sensitivity and ESS-SS-Specificity. On study showed the negative predictive value of the combined tests to be 97.5% therefore if both tests are negative the possibility of a positive urine culture is remote.

7 . Dipslide culture methods

Agar counted slides are immersed in urine or even exposed to the stream of urine during voiding, incubated and growth is estimated by colony counting, by colour change of indications.

8.Automated tests

Based on detection of adenosine triphosphate (ATP) by measuring light emitted by the reaction of lacifenin luciterase. These tests are expensive and takes time.

9. BAC- T screen bacteriuria detection device

In this method the urine is forced through a filter paper, which retains microorganisms, somatic cells and other particles. A dye is then added to the filter paper to visualize the particulate matter that has adhered. The intensity of colour relates to number of particles. This procedure takes approximately one minute, has been shown to detect greater than 90% of all positive urine specimens even in 102 organisms per ml are consider to be significant.

A manual filtration method using the reagents on ;the Bac-T screen in the filtrate checks out Urinary Tract Infection.

Another promising recently introduced manual system combines filtration with differential media to quantitate and identify presumptively uropathogens with results available within 4 hrs.

None of the screening methods are as sensitive or as reliable on a culture. These tests may have a role in ;the immediate diagnostic. Screening of symptomatic patients and may be if some value in mass screening programs. They are not a substitute for urine culture.


Nitrite dipstick is subject to false-negatives, because 4 to 6 hours is required for bacteria to convert nitrate to nitrite in bladder urine, and some infecting organisms are nitrite negative. In a study of bacteriuria screening in infants ,85% of nitrite tests were false negative compared with culture. A 53% false-negative rate was also reported in an obstetric population with dipstick screening of nitrite[28].


The quantitative urine culture remains the optimal screening test[28].

Pour plate dilution technique:

This is an extremely accurate method but time consuming. It is used as a standard of comparison for other methods. Here double dilution series of urine or two fold dilution of urine are spread over the culture plate. The number of colonies in each plate in head in 24 hours and 48 hours and colonies calculated.

Surface culture methods:

Serial 10 fold dilution of urine are plated by surface culture method Number of colonies are calculated at end of 24 hr & 48 hrs.

Both the above methods are too complicated for routine diagnostic ---- for which semi quantitative techniques are more conveniently calibrated bacteriologic loop technique.

Most commonly employed method. In this standard platinum loops or disposable sterile loops are designed to deliver either 0.01 ml or 0.001ml of urine used.

The urine should be mixed thoroughly before plating flame a wire calibrated inoculating loop and allowed to cool and should not touch the surface if disposable plastic tips are not used. Insert the loop vertically into the urine to allow urine to adhere to the loop spread the loopful of urine to the surface of blood agar loop is touched to the center of the plate, from which the inoculums is spread in a line across the diameter in the plate, without flaming or reentering urine loop in drawn across the entire plate crossing the first inoculums without inflaming insert the loop vertically into the urine again for transfer of a loopful to an indicator medium. Incubate plates for atleast 24 hours at 35o to 37o c in air. The colonies are counted on each plate. The number of colonies CFUs are multiplied by 1000 ( if a 0.001ml loop is used) or by 100 if a 0.01ml of loop was used to determine the number of microorganisms per ml in the original specimen. The former medium gives quantitative measurement of bacteriuria while the later a presumptive diagnosis of the bacterium. The isolated are identified by their properties.

Reincubate plates with no growth or tiny colonies for an additional 24 hours before discarding plates. Since antimicrobial treatment or other factors may inhabit initial growth.

Antibiotic sensitivity test

Antibiotic sensitivity tests may be done directly using the urine samples as inocula and the results confirmed by repeating the tests with individual isolates.

Localization of urinary tract infection

Localisation of urinary tract infection to the bladder or kidney in women and to the bladder, kidney or prostate in men, importantly influences the clinical manifestation, response to treatment likelihood and pattern of recurrent infection and long term prognosis associated with these patients. In diabetic patients with urinary tract infection half of patients have upper urinary tract infection. This stratification of patients by site of infection becomes critical. While an ideal procedure for localization of urinary tract infection does not exist, the following techniques are available.

Invasive Method

Ureteral Catheterization

This method was cystoscopy followed by collection of bladder urine samples for quantitative culture. The bladder is then irrigated, repeatedly to wash out bladder organisms. This is confirmed by collecting further samples at the end of the washout procedure. Catheters are then placed along the ureters and left in the place to collect uretheral urine for quantitative culture. A diagnosis of upper tract infection is based on evidence of a 10 fold increase in bacterial counts in ureteral urine compared with post wash out bladder urine. This technique is invasive, not without morbidity and with considerable urological exploration. This method can identify unilateral Upper Urinary Tract Instrumentation.

Bladder washout technique

This method is now usually considered to be the most acceptable gold standard against which all newer techniques should be compared.

To do the washout test, a triple human catheter is inserted, a specimen is collected for culture and the bladder is emptied of urine. Next 100ml of sterile saline, containing 5mg gentamicin or 2 mg of neomycin and 1,25,000 units of topical streptokinase - stretodornace ( two ampoules of the drug) is injected into the catheter and allowed to remain for 30 min. The bladder is then emptied of urine, washed out with two litres of sterile saline and a post washout culture specimen is obtained. Subsequently, five additional urine specimens are collected 10 min are collected 10 minutes apart and the catheter is withdrawn. After quantitative urine cultures have been done in all specimen patients are classified to have lower tract infection if all post-washout culture specimen or upper tract infection if bacterial count > 102/ml occur in at least 4 of specimen 3 to 7 and there is a long increase in count between specimen 2 and the later specimen.

False positive results occur in those patients who have intermittent shedding of microorganisms from kidney and in patients with vesicoureteric reflux.



The ability to concentrate urine is used to localize urinary tract infection. Renal infection results in a decreased concentrating ability; but not the bladder infection. Bilateral infection produces greater concentrating defect. Treatment usually produces a return of normal concentrating ability.


Wacker and Dorfman found that urinary lactate dyhydrogenase activity was elevated in upper urinary tractr infection. Recently LDH - iso - enzyme 5 has been investigated as a localization tool.

False positive results occur in the presence of pyuria, haematuria, proteinuria. So that test is insensitive and non specific.

Measurement of urinary β glucuronidase activity as a localization tool is suggested by Ronald. In patients with upper urinary tract infection, this enzyme level is high

Vigano and associates suggests measuring the renal tubule cell enzyme N Actyl-β-D- Glucosaminidase to localize upper urinary tract infection.


Serum levels of antibody directed against the lipopolysaccharide antigen present on bacteria, particularly that of E.Coli are commonly raised in patients with upper tract infection and absent in those with bladder infection. This is most diagnostically useful when an acute increase in antibody titres is demonstrated on serial samples taken over the period of the infection. Sensitivity and specificity of this test is still doubtful.


Jodal and colleagues reported that consistently elevated level of C - reactive protein in serum, detected by immune diffusion technique were seen in children with pyelonephritis, not with acute cystitis. This test is less sensitive in evaluating adult Urinary Tract Infection.


Described by Thomas in 1974. This method is widely spread and used now because of its simplicity and apparent reliability.

The test depends upon the demonstration of immunoglobin to somatic or O Antigen on the bacterial cell surface. The presence of immunoglobulins is taken as evidence of invasion of tissues, especially the kidney by bacteria, resulting in an antibody response. IgG, IgM, IgA have all been shown to participate in the antibody coating phenomenon, IgG being predominant. Fluorescein-labelled anti-human immunoglobulin is incubated with infected urine and the number of fluorescent - bacteria present s recorded. Different criterias are used for a positive result. The original criterion of Thomas required 25% of all bacteria seen to be fluorescent to qualify as a positive assay. Subsequent criteria have ranged from 1 to 20 fluorescing bacteria in a search of 200 fields to 2 to 5 fluorescing bacteria in a five minute search.

False positive results occur when vaginal or rectal flora contaminate a urine specimen, proteinuria, prostatitis, haemorrhagic cystitis or bladder infection in the presence of bladder tumors or catheters.

False negative results occur in the range of 16 to 38%, if there is delay in performing the test, particularly if bacterial multiplication continues.

In a first inflection the test may not become positive for 2 weeks.


Described by Robin, using the antibody coated bacteria test in conjunction with single dose therapy, the response to single dose of antibiotics may be used as a localization tool.


Renal scanning with 67Ga citrate has been used to localize infection. A false positive rate of 15% and a false negative rate of 13% have been reported.


Significant concentration of IgG and IgA anti Tamm-Horsfall glycoprotein antibodies have been observed in patients with acute pyelonephritis, especially in the presence of vesicoureteric reflux. But this is not the case in lower urinary tact infection.


Asymptomatic bacteriuria is common in neonates, preschool children, pregnant women, elderly patients, in diabetics, in catheterized patients and in patients with abnormal urinary tracts or renal disease. Asymptomatic bacteriuria is uncommon in non elderly, non pregnant women and in men.

The patients with diabetes mellitus have many potential reasons to have bacteriuria which in many instances may be asymptomatic, including poor control of blood glucose levels, diabetic neuropathy with neurogenic bladder and chronic urinary retention, impairment of leucocyte function, frequent instrumentation of urinary tract, recurrent vaginitis and diabetic microangiopathy, and large vessel renal vascular disease.

The prevalence of asymptomatic bacteriuria is not significantly influenced by the duration of diabetes or the quality of diabetic control. A recent study that evaluated haemoglobin A1c levels in diabetic patients with and without bacteriuria was unble to relate the risk of bacteriuria to the level of haemoglobin A1c at the time of urine culture, thus concluding that factors other than reversible metabolic derangement place the diabetic at risk of bacteriuria.

The prevalence of asymptomatic bacteriuria increase as diabetic retinopathy becomes more severe, as heart disease and peripheral vascular disease become apparent .

Locaization techniques indicate that approximately half of all diabetic patients with bacteriuria have upper urinary tract involvements. Most of these patients are asymptomatic .

The long term consequences of asymptomatic bacteriuria in patients with diabetes mellitus are poorly documented. These patients are at high risk of developing.

1.Acute pyelonephritis

2. Renal corticomedullary abscess

3. Renal carbuncle

4. Emphysematous pyelonephritis

5. Emphysematous cystitis

6.Papillary necrosis

7.Metastatic infection

8. Perinephric abscess

Infectious Diseases Society of America-US Public Health Service Grading System for ranking recommendations

in clinical guidelines.

Category, grade Definition

Strength of recommendation

A Good evidence to support a recommendation for use; should always be offered

B Moderate evidence to support a recommendation for use; should generally be offered

C Poor evidence to support a recommendation; optional.

D Moderate evidence to support a recommendation against use; should generally not be offered.

E Good evidence to support a recommendation against use; should never be offered

Quality of evidence.

I Evidence from ≥1 properly randomized, controlled trial.

II Evidence from ≥1 well-designed clinical trial, without randomization; from cohort or casecontrolled analytic studies (preferably from 11 center); from multiple time-series; or from dramatic results from uncontrolled experiments.

III Evidence from opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees.

Recommendations relevant to the diagnosis of urinary tract infections



Diagnosis is based on the results of urine culture with

specimen collected to minimize contamination


For asymptomatic women, two consecutive voided urine

specimens with the same bacterial strain ≥105 CFU/mL B-II

defines bacteriuria

For asymptomatic men, a single voided specimen with B-III

≥105 CFU/mL defines bacteriuria

For men or women, a single catheterized urine specimen A-II

with a single species ≥102 CFU/mL

Pyuria accompanying bacteriuria is not an indication for A-II

antimicrobial treatment

CFU: colony-forming units.

Recommendations for screening for, and treatment of, asymptomatic bacteriuria

(ASB) in selected groups

Recommendation Grade

Pregnant women should be screened for bacteriuria by urine

culture at least once in early pregnancy, and they should A-I

be treated if the results are positive

Screening for, and treatment of, ASB before transurethral A-I

resection of the prostate is recommended

Screening for, and treatment of, ASB is recommended A-III

before other urological procedures for which mucosal

bleeding is anticipated

Recommendations against screening for, and treatment of, asymptomatic


Recommendation Level

Screening for, and treatment of, asymptomatic bacteriuria is not

recommended for:

1. Premenopausal, nonpregnant women A-I

2. Diabetic women A-I

3. Older people living in the community A-II

4. Elderly, institutionalized people A-I

5. People with spinal-cord injury A-I

6. Patients with indwelling catheters A-I