ABSTRACT
Asymptomatic bacteriuria or asymptomatic urinary infection are bacteria present in urine in the absence of clinical signs and symptoms of urinary infection in the hosts. The microbiological definition is having greater than or equal to 105cfu/ml of same organism(s) in a urine specimen. This study investigated the prevalence of asymptomatic bacteriuria in female students and to determine the antibiotic sensitivity pattern of bacterial isolates. A total of forty (40) female student urine samples were examined and analyzed for asymptomatic bacteriuria. The total number of positive cultures (with significant growth) 17 out of 40 samples analyzed representing 42.5% is presented in table 4 while 57.5% was with insignificant growth. Culture plates with bacteria count greater than or equal to 105cfu/ml were considered significant and thus indicative of UTI (Urinary tract infection). The bacterial isolates and their percentage prevalence of the organisms is as show in table 3. Escherichia coli was found to be the most prevalent (47.0%), followed by Staphylococcus aureus (23.5%) and Klebsiella Spp (11.7%). The least prevalent organisms were Proteus Spp and Streptococcus Spp with 11.7% and 5.8% respectively. Isolates were tested against antibiotics which included Ampicillin, Cotrimoxazole, Ciprofloxacin, Gentamicin, Tetracycline and Chloramphenicol by disc diffusion method. The occurrence of asymptomatic bacteriuria was 42.5% while the isolates were E. coil representing 47.0% of the isolates. Others were S. aureus 23.5%, Klebsiella Spp (11.7%); Proteus Spp (11.7%) and Streptococcus Spp (5.88%). A negative test for nitrite and leucocyte esterase was not used to rule out an infection as culture was demonstrated on such samples. Positive tests from the urine dipstick analysis however required further confirmation through urine culture. Ciprofloxacin was the most active antibiotic as it achieved a success rate of 87.5% against E. coil while Tetracycline and Ampicillin recorded the least. The incidence rate of 42.5% reported in this study should be of great concern because asymptomatic bacteriuria predisposes patients to UTI.
TABLE OF CONTENTS
Title page i
Certification ii
Dedication iii
Acknowledgment iv
Table of Contents v-vi
List of Tables vii
Abstract viii
CHAPTER ONE:- INTRODUCTION AND LITERATURE-REVIEW
1.0
Introduction 1
1.1 Aim and Objectives 2
1.2 Literature Review 3
1.2.1 An Overview of Urine 3
1.2.2 Asymptomatic Bacteriuria 4
1.2.2.1 Etiology 4
1.2.2.2 Pathophysiology 5
1.2.2.3 Classification 5
1.2.2.4 Epidemiology 6
1.2.2.5 Presentation 7
1.2.3 Asymptomatic Bacteriuria in
Pregnancy 7
1.2.4 Asymptomatic
Bacteriuria in Diabetic Patients 9
1.2.5 Pathogenesis of ASB and UTIs 11
1.2.6 Bacterial
Adherence and Virulence Factor for UTI 12
1.2.7 Diagnosis
of ASB and UTIs 12
1.2.7.1 Urine
Microscope 13
1.2.7.2 Dipstick
Test 13
1.2.7.3 Urine
Culture 14
1.2.8 Common
Antibiotics for ASB and Other UTIs 15
CHAPTER TWO:-
MATERIALS AND METHODS
2.0 Materials 17
2.1 Study
Population 17
2.1.1 Collection
of Samples 17
2.2 Methods 17
2.2.1 Sterilization
of Media and Materials 17
2.2.2 Microscopy 17
2.2.3 Isolation
of Bacterial Species 18
2.2.4 Identification
of Isolates 18
2.2.4.1 Gram
Staining 18
2.2.4.2 Biochemical
test 19
2.2.5 Subculture
and Purification 20
2.2.6 Antimicrobial
Susceptibility Testing 20
CHAPTER THREE
Results 22
CHAPTER FOUR
Discussion, Recommendation and Conclusion 29
References 33
LIST
OF TABLES
|
|
Page
|
|
1
|
Urinalysis for Nitrite and
Leucocyte Esterase.
|
23
|
|
2
|
Microscopic Examination
|
24
|
|
3
|
Frequency of Isolation of
Organisms
|
25
|
|
4
|
Level of Bacteriuria.
|
26
|
|
5
|
Biochemical, Macroscopy and
Microscopic Characteristic of Isolated Bacteria
|
27
|
|
6
|
Antimicrobial
Susceptibility Rates of Bacterial Isolates against Antimicrobial Agents
|
28
|
CHAPTER ONE
1.0 INTRODUCTION
The term bacteriuria means the presence of bacteria in
urine and it is taken to be significant when urine contains a bacterial count
of 105cfu/ml in voided mid stream urine, aseptically collected from
an individual without apparent symptom of urinary tract infection (Forbes et al, 2002., Ophori et al., 2010). Asymptomatic bacteriuria is bacteriuria
without the classical symptoms of urinary tract infection (fever, frequent
urination; painful urination). The importance of asymptomatic bacteriuria is
that it is a major risk factor for the development of UTI (Patterson and
Andnole, 1997).
Bacterial infection of the urinary tract in human are
the most frequent bacterial disease affecting out patients, hospitalized
patients and apparently healthy populations (Piatti et al., 2008). The frequency and natural history of asymptomatic
bacteriuria vary for different populations and is more common in females than
in males by virtue of the shortened urethra.
Asymptomatic bacteruria can occur in both infants and
adults but is seen more frequently in females than in males and is a major
contain in UTI (Nurullaev, 2004). This is because under favorable conditions,
asymptomatic bacteriuria progresses to symptomatic (clinical) UTI (Scholes et al., 2000; Harrington and Hooton, 2000).
Factors such as shortness of urethra, estrogen deficiency, use of
contraceptives, diabetes, sexual activity, easy contamination of urinary tract
with fecal flora (Gupta et al.,
2001), obstructing lesions, and genetic factors such as blood group secretor
status, increase the likelihood of women contracting a UTI (Scholes et al., 2000).
The clinical significance of asymptomatic has been
however controversial because the widespread use of the quantitative urine
culture provided a reliable means for identification. This has led to question
whether bacteriuria, in the absence of symptoms, leads to complications of
urinary infection. Adverse outcomes, of concern have included the short-term
complications of symptomatic lower tract infection and longer-term
complications, such as genitourinary concern, renal failure, hypertension and
death. Alternatively, asymptomatic bacteriuria may be beneficial. Colonization
of the genitourinary tract by an virulent organism could prevent infection with
more virulent organisms, through competition for nutrients, or receptor sites,
by eliciting a cross host immune or inflammatory response or by other mechanisms.
Bacteria that colonize the urinary tract (which include
organs that collect and store urine and release it from the body: kidneys,
ureters, bladder and urethra) may ascend towards the bladder to cause cystitis,
which is usually associated with the classic symptoms of UTI. UTI can proceed
from the bladder, through the ureters, to the kidneys where it can cause pylonephritis,
which may lead to irreversible kidney damage, renal failure and death (Scholes et al., 2005).
The most bacterial etiologic agents in asymptomatic
bacteriuria are mostly members of the Enterobacteriaceae Klebsiella pneumonia, Eschericbia, Enterococcus faecalis, Streptococcus agalactiae; Staphylococcus and Streptococcus
pyogenes (Ophori et al., 2010) with
E. coli being the most common
organism isolated from patients with asymptomatic bacteriuria (Geerlings et al., 2000). These bacteria are
resistant to multiple antibiotics, and thus, they pose a serious threat to the
safety and proper functionary of the patient. Untreated asymptomatic
bacteriuria predisposes an individual to recurrent UTI, which may cause renal
diseases. However, in most cases, asymptomatic bacteriuria does not cause any
problem and treatment is not necessary.
1.1
AIMS AND OBJECTIVES
This study is aimed at;
(a)
Investigating the
prevalence of asymptomatic bacteriuria (ASB) in female students of MOUAU
(b)
Isolating and identifying
the organisms responsible for the infection.
(c)
Studying the effects of
commonly used antibiotics on the bacteria isolated i.e. antimicrobial
susceptibility pattern of isolated bacteria.
1.2 LITERATURE
REVIEW
1.2.1 AN OVERVIEW OF URINE
Urine is an aqueous solution of greater than 95% water, with the
remaining constituents in order of decreasing concentration as follows:- area
9.3g/l, chloride 1.87g/l, sodium 1.17g.l, potassium 0.75g/l, creatinine
0.670g/l and other dissolved ions, inorganic
and organic compounds (Colgan et al.,
2006). Urine is a typically sterile bye-product of the body secreted by the
kidneys through a process called urination and excreted through the urethra.
Urine contains a variety of fluids; salts and waste products (Ngwai et al., 2010). Urine flows from the
kidney through the Ureter, bladder and finally the urethra before leaving the
body. The urine is usually sterile until it reaches the urethra, where epidermal
cells living the urethra are colonized by facultative anaerobic Gram negative
rods and cocci (Madigan and Brock, 2009). When these bacteria get into the
bladder or kidney and multiply in the urine, they cause urinary tract infection
(UTI). Sequel to elimination from the body, urine can acquire strong odours due
to bacterial action and in particular, the release of ammonia from the
breakdown of urea.
Some diseases alter the quantity and consistency of urine (e.g.)
diabetes introducing sugar into urine (Watts et al., 1993).
Urine varies in appearance depending principally upon the body’s
level of hydration, as well as other factors. Normal urine is transparent
ranging from colorless to amber but is usually Pale yellow (Colgan et al., 2006). The colorless urine
indicates over-hydration. Average urine production in adult human is about
1-2l/day, depending on state of hydration, activity level, environmental factors,
weight and the individual’s health. Producing too much urine requires medical
attention. Polyuria is a condition of excessive production of urine (> 2.5l/day;
Oliguria < 100ml per day). Turbid or cloudy urine may be a symptom of
bacteria infection.
1.2.2 ASYMPTOMATIC BACTERIURIA AND UTIs
Asymptomatic bacteriuria in young women is common but
rarely persists. It is a strong predictor of subsequent symptomatic urinary
tract infection. Asymptomatic bacteriuria occurs frequently and is a major
cause of UTI.
This is because under favorable conditions, asymptomatic presents
with symptoms of UTI (Scholes et al.,
2000).
UTI is defined as the presence and multiplication of
significant numbers of microorganisms in one or more structures of the urinary
tract (Bladder, urethra, kidneys) with the organism invading the surrounding
tissue (Stanm,2002., Scholes et al.,
2000). Bacteria in the urine especially gram-negative rods usually indicate a
UTI. UTIs are among the most common bacterial infections acquired in the
community and in hospital. They are generally self-limiting but have a
propensity to recur (Salvatore et al.,
2011, Foxman, 1990). UTI affects all age groups and is among the leading cause
of morbidity in persons of all age specific sub- populations at increased risk
of UTIs include pregnant women (Okonko et
al., 2010), the elderly, patients with spiral cord injuries and/ or
catheters (Nicolle,2001), patients with diabetes or sclerosis, patients with
AIDs/HIV patients with underlying urologic abnormalities. The risk of incidence
increases with age co-existent disease and increasing duration of
catheterization.
1.2.2.1 ETIOLOGY
UTI is caused by the ascent of bacteria up the urethra.
The organisms that cause UTI are common normal rectal and perinea bacterial
flora and include Escherichia coli, Klebsiella,
Staphylococcus and Streptococcus (Ophori
et al., 2010). E coli remains the
predominant Uropathogen (80%) isolated in acute community acquired
uncomplicated infections followed by Staphylococcus
saprophytic, Klebsiella, Enterobacter
and proteins species. These bacteria have specialized characteristics, such as
the production of adhesins, siderophores and toxins that enable them to
colonize and invade the urinary tract (Johnson, 1991; Mabbett el al., 2009). The pathogens tradition
associated with UTI are changing many of their features, particularly because
of antimicrobial resistance (Wold et al.,
1992). The etiology of UTI is also affected by underlying host factors that
complicate UTI such as age, diabetes, spiral cord injury or catheterization.
1.2.2.2 PATHOPHYSIOLOGY
The urinary tract, from the kidneys to the urethral
meatus is normally sterile and resistant to bacterial colonization (Olowu and
Oyetunji, 2003), despite frequent contamination of the distal urethra with
colonic bacteria. Mechanisms that maintain the tract’s sterility include urine
acidity, emptying of the bladder at micturition urination, ureteroversical and
urethral sphincters and various immunologic and mucosal barriers.
About 95% of UTIs occur when bacteria ascent the urethra
to the bladder and, in the case of acute uncomplicated pyelonephritis, ascend
the ureter to the kidney (Olaitan, 2006) the remained of UTIs are hematogenous.
Systemic infections can result from UTIs particularly in the elderly.
1.2.2.3 CLASSIFICATION
Bacterial UTIs can involve the urethra, kidneys and
bladder. A UTI may involve only the lower urinary tract (bladder), in which
case it is known as cystitis (Colgan and Williams, 2011) or bladder infection.
Alternatively, it may involve the upper urinary tract (kidneys) in which case
it is called pyelonephitis (Lane and Takhar, 2011). It can also affect the urethra
when organisms gain access to it, acutely or urethra in which case it is known
as urethritis. A UTI is said to be complicated when the patient has diabetes,
is pregnant or immune compromised. Otherwise if a women is healthy and
pre-menopausal, it is considered uncomplicated (Colgan and Williams, 2011). A
complicated UTI is lying factors that predispose to ascending bacterial
infection. Such predisposing factors include urinary instrumentation (E.g.
Catheterization), anatomic abnormalities, poor bladder emptying etc
uncomplicated UTI occurs without underlying abnormalities impairment of urine
flow.
1.2.2.4 EPIDEMIOLOGY
UTIs are the most
frequent bacterial infection in women. They occur more frequently between the
ages of 16 and 35 years with 10%of women getting an infection yearly and 60% an
infection at some point in their lives.
Recurrences are common, with nearly half of the women getting a
second infection within a year (Stapleton, 1999) UTIs occur four times more
frequently in female than males because of their anatomic predisposition (i.e
short urethra).This holds true at most ages except in elderly populations where
the UTI rates in males approaches that of females of the same age (McMurdo and
Gillespie; 2000). The rate of asymptomatic bacteriuria increase with age from
2-7% in women of child bearing age to as high as 50% in elderly women
(Dielubanza and Schaefer, 2011). The increased risk of UTI in women using
antibiotic or spermicidal probably occur because of alternations in vaginal
flora that allow overgrowth of E. coli (Stecher and Hardt, 2008).
In young sexually active women, sexual activity is the
cause of 75-90% of bladder infections, with the risk of infection related to
the frequency of sex (Hooton et al.,
2000). Antibiotic use changes the vaginal flora and promotes colonization of
the genital tract with E. coli,
resulting in subsequent increased risk of UTI.
The organism isolated in patients with asymptomatic
bacteriuria will be influenced by patient variables healthy persons will likely
have E. coli, whereas a nursing horn resident with a catheter is more
likely to have multiple drug resistant polymicrobic flora (e.g. Pseudomonas aerogenosa) (Mims et al.,
1990).
1.2.2.5 PRESENTATION:
A UTI can present
with a range of symptoms the presenting symptoms will vary with the age and
sere of the patient and also with the severity and site of the infection but
may include:- urinary frequency, Dysuria, Hematuria, Urinary Inconsistency, Rigors,
Nausea, Vorniting, Suprapubic or loin pain, and painful frequent passing of
only small amounts of urine (Nicolle, 2003). In all form of UTI (Cystitis, Urethritis,
pyelonephritis), the urine may be cloudy, urination tends to be painful of the
urethra is inflamed. If the bladder is inflamed, urination is both painful and
frequent. If the infection reaches the kidney, symptoms are more severe.
1.2.3 ASYMPTOMATIC BACTERIURIA
This is a major risk factor for the development of UTI in pregnancy
due to physiological changes (Ophori et al.,
2010). Increased UTI in pregnant women has led to high morbidity and mortality
with the subsequent increase in Nosocomial infection (Vazque and Sobel, 1995).
Although the incidence of bacteriuria in pregnant women is similar to that in
that non-pregnant women, the incidence of acute pyelonephritis in pregnant
women with bacteriuria is significantly increased (Schnarr and Smaill, 2008).
While asymptomatic bacteriuria in no non-pregnant women is generally benign,
pregnant women with bacteriuria have an increased susceptibility to
Pyelonephritis (Dafnis and Sabatini, 1992). The prevalence of asymptomatic
bacteria range from 6.1% to 10.9% the rate of asymptomatic bacteriuria in
pregnant women is comparable to non-pregnant women, indicating that pregnant
alone does not necessarily incline to the development of asymptomatic
bacteriuria. Nicolle (2003) reported that the frequency of bacteriuria
increases by about 1% during pregnancy.
There are a number of conditions associated with an increased
prevalence of asymptomatic bacteriuria in pregnancy- low socio economic status,
sickle cell traits diabetes previous medical history of UTI and grand
multiparty (Ophori et al., 2010).
Pregnancy is a
unique state with anatomic and physiologic urinary tract changes. It causes
numerous hormonal and mechanical changes in the body. It also gives rise to
several. Physiological changes resulting in immune suppression. In a study by
Brian and Pamela (2003), it was shown that T and B lymphocytes count do not
change in pregnancy but their function is suppressed. This explains the
increased incidence of infection in pregnant women.
UTIs are one of such infections and are more concerning
in pregnancy due to the increased risk of kidney infection (Ezeome et al., 2006). In pregnancy, beginning
in the sixth week, with peak incidence during the 22nd to 24th
week, the high progesterone levels elevate the risk of decreased muscle tone of
the ureters and bladder, which leads to a greater likelihood of reflux (Schnarr
and Smaill, 2008), where urine flows back up the ureters and towards the
kidneys. The pressure effect of a much bigger, the increasing smooth muscle
relaxing effect of pregnancy hormone, and the pressure on the blood from the
descending presenting part, ma all lead to stasis of urine, which will
encourage bacteria multiplication (Oli et
al., 2010).
In addition, differences in urine PH and
Pregnancy induced Glycosuria and aminoaciduria provide an excellent culture
medium for bacterial growth in areas of urinary stases (Schnarr and Smaill,
2008). These changes along with the already short urethra and difficulty with
hygiene due to the distended pregnant belly increase the frequency of UTI in
pregnant females.
A limited and predictable spectrum of organisms causes
UTI in pregnant otherwise healthy females. E.
coli is the primary urinary tract pathogen accounting for 75%-90% cases
others are Staphylococcus saprophyticus, Klebsiella pneumonia, Proteus mirabilis and Group B Streptococci.
UTIs are one of the most common medical complications of
pregnancy. This is because untreated upper UTI in pregnancy carries well
documented risk of morbidity and rarely mortality to the pregnant women (Okonko
et al., 2010). Untreated bacteriuria
in pregnancy either asymptomatic or symptomatic is associated with a 50%
increase in the risk of low birth weight and a significant increase in the risk
of premature delivery, pre-eclampsia (a state of high blood pressure and kidney
dysfunction during pregnancy that can lead to seizures) (Nicolle, 2003),
hypertension and anemia (Kiningham, 1993). Some of the fetal complications of
acute pyelonephitis in pregnancy include premature labour, intra-uterine growth
restriction and possibly intra-uterine fetal death (Addo et al., 2002). Some possible material complications include chronic
pyelonephritis and septicemias (Oli et
al., 2010). However, screening of
pregnant women for asymptomatic bacteriuria and associated UTI minimize these
UTI associated complication. Certain antibiotic are unsuitable for use in
pregnancy (e.g. tetracycline) due to their potential toxicity.
1.2.4 ASYMPTOMATIC BACTERIURIA IN DIABETIC PATIENTS:
Diabetes mellitus has a
number of long-term efforts on the Genito-urinary system. This effect
predisposes to bacterial urinary tract infection in the patient with diabetes
(Ophori et al., 2010). Diabetes
mellitus is a major health problem in Nigeria. Following the 1985 World Health
Organization (WHO) criteria, diabetes mellitus is defined an a fasting glucose
concentration of at least 7.8mmcl/l (140ml/l) or a two hour glucose
concentration of at least 11.1mmg/L(200mg1/L) (Wahl et al., 1998).
Asymptomatic
bacteriuria occurs three (3) times more often among women with diabetes than
among otherwise healthy women; asymptomatic bacteruria is associated with an
increased risk of symptomatic infection (Geerlings et al., 2001). The presence of asymptomatic bacteruira in diabetic
women is however not associated with a faster decrease in renal function
(Meiland et al.,2006) or a greater
risk of diabetes complications or mortality (Geerlings et al; 2001). Risk factor of asymptomatic bacteriuria in diabetic
women include sexual intercourse, degree of metabolic control, age duration of
diabetes, insulin use and some diabetes complications. In a study of Zhanel et al., 1991, involving women with
diabetes, there was an association between asymptomatic bacteriuria and
long-term complications of diabetes such as retinopathy, nephropathy and
neuropathy. The bladder dysfunction due to diabetic neuropathy could play a
role in the prevalence of asymptomatic bacteriuria among women with diabetes
(Nicolle, 2001). Women with diabetes and asymptomatic bacteriuria has a much
higher chance to develop pyelonephritis some individuals present with a
distressing picture showing definite progression of pyelonephritis
characterized by evidence of systemic infection, local extension of the
infection, septicemia, and severe impairment of metabolic control, which may become
too difficult to manage. Because of these reasons, diabetes has long been
considered to be as predisposing factor for UTI.
UTI is classically
assumed to be a clinically relevant problem for persons with diabetes (Baldwin
and Root, 1993). The increased prevalence (7% to 13%) of bacteriuria in
diabetic women is largely attributable to autonomic neuropathy leading to on
paired bladder emptying (Schnarr and Smaill, 2008).
Many possible
explanations have been proposed to account for the greater prevalence of
bacteriuria in diabetic persons. These include:-
Ø Increased adherence of uropathogens to bladder epithelial cells.
Ø The effects of glucosuria of the growth of uropathogens in diabetic
persons (Geerlings et al; 2001).
E. coli has been reported to adhere more
tightly invitro to the vaginal and buccal cells of women with recurrent UTIs
than those of healthy persons. High levels of glucose in the urine of persons
with diabetes might cause uropathogens to furnish. Geerlings et al; 2001 found that moderate and
severe glucosuria (glucose concentrations between 100 and 1000mg1/L) enhanced
bacterial growth inviro. These glucose concentrations are seen in the urine of
out patients with diabetes ranges from 0to 6.0mg1/L.
Symptomatic urinary
infection may be more severe in diabetic than non- diabetic patients.
The severity of symptomatic infection and frequent observation of
bacteriuria in diabetic women has led to some recommendations for treatment of
asymptomatic bacteriuria However, a long-term prospective study of the
nature history of asymptomatic bacteria is harmful These studies suggest that
asymptomatic bacteriuria (ASB) in diabetic women does not glucose control or
promote development of long-term complications of diabetes. Antimicrobial
treatment of bacteriuria does not decrease the frequency or severity of,
symptomatic urinary infection.
1.2.5 PATHOGENESIS OF ASB
AND UTIs
The normal genitourinary tract is sterile, apart from the distal
urethra. Uropathogenic organism especially uropathogenic E. coli (UPE) have a variety of virulence tracts that enable them
to successfully the normally sterile urinary tract (Zhang and Foxman, 2005)
these tracts include a number of adhesions, iron sequestration systems and
toxins that distinguish them from normal bowel flora E. coli; ASB occurs following ascension of bacteria up the urethra
into the bladder, sometimes with subsequent ascension to the kidneys. After
gaining entry to the bladder, E. coli are able to attach to the bladder
will and form a biofilm that resists the body’s immune response (Salvatore et al., 2011). These organisms then
persist in the urinary tracts without eliciting a host response sufficient to
produce symptom or cause indication (Scharr and Smaill, 2008), variables such
as host genetic disposition, incomplete bladder emptying or the presence of a
foreign body may all facilitate persistence, expression of organism virulence
factor is, then, one variable that determine symptoms or persistence. A local
urinary host response is often present despite the absence of symptoms. Pyruria
is the most common. Other local inflammatory or immune markers such as cytokines
and urinary immunoglobulin may also be present.
1.2.6 BACTERIAL ADHERENCE AND
VIRULENCE FACTORS FOR UTI
Bacterial adhesion onto mucosal or urothelial cells is
an important phenomenom determining bacterial virulence. Infection in the
urinary tract is relented in part to the ability of, urethra, bladder and renal
interstitum (Mulvey, 2002). Adhesion property of the bacteria is an important factor
that mediate the ability of a bacterial species to colonize the vaginal surface
uropathogenic Enterobacteriaceae are electronegative and too small to overcome
repulsion by the net negative charge of epithelial cells. As a result bacterial
adhesion cannot occur in the absence of fimbriae or other (non-fimbriae)
surface adhesion systems. These systems have favorable electrical charge and
also promote adhesion through hydrophobicity fimbriae allow irreversible
attachment to the uroepithelial cell membrane through adhesions (Oelschlaeger et al., 2002). The virulence factors of E. coli are mainly responsible for
promoting progression of the organism from the fecal reservoir into the bladder
and occasionally the kidney.
1.2.7 DIAGNOSIS
Asymptomatic bacteriuria is a
microbiologic diagnosis determined with a urine specimen that has been
collected in a manner to minimize contamination and transported to the
laboratory in a timely fashion to limit bacterial growth. Thus the presence of
a significant quantity of bacteria in a urine specimen properly collected from
a person without symptoms or a sign of a UTI characterizes ASB (Rubin et al; 1992). A clean- catch urine
sample in which urine is collected in midstream (a technique where the first 5ml
of urine is not captured but the next 5 to 10ml is collected in a sterile
container) to prevent contamination with organisms present at the opening of
the urethra is necessary for laboratory analysis. Analysis may involve simple
dictation for the presence of bacteria or it may involve culture and
identification of the specific organism that is causing infection. It may be
useful to confirm the diagnosis through urinalysis, looking for the presence of
urinary nutrient, white blood cells (leucocytes) or leucocytes esterase another
test, urine microscopy, looks for the presence of red blood cells, white blood
cells or bacteria. The other test urine culture, is deemed positive of it shows
a bacterial colony count greater than or equal to 105cfu/ml of a
typical urinary pathogen (Hooton et al;
2000).
1.2.7.1 URINE MICROSCOPY
Microscopic examination of urine is useful but not definitive as it
reveals the presence of pus, bacteria and other substance in urine. Pyuria (pus
in urine) is evidence of inflammation in the genitourinary tract and is common
in subjects with asymptomatic bacteriuria
Phyuria is present with ASB in 32% of young women. Pyuria is defined
as 8WBcs/ML of uncentrifuged urine, which corresponds to 2-5 WBCs/high power
field in spun sediment. The presence of bacteria in the absence of pyuria, is
usually due to contamination during sampling. Gross hematuria is uncommon.
Pyuria also accompanies other inflammatory conditions of the genitourinary
tract and is thus, by itself, not sufficient to diagnose bacteriuria.
1.2.7.2 DIPSTICK TEST
Also are commonly used. The stick has 9-pads each
impregnated with different chemicals. The leukocyte esterase and nitrite tests
(two of the components of the stick) are used in primary care settings to
evaluate urinary symptoms. A positive nitrite test on a freshly collected
sample is highly specific for UTI, but the test is not very sensitive. The
leukocyte esterase test is very specific for the presence of >10WBCS/ml and
is fairly sensitive.
Limitations of the
dipstick nitrite test in diagnosing bacteriuria include:- infection with
non-nitrite producing pathogens; delays between obtaining and testing the
sample; and insufficient time from the collection for nitrites to appear at
detectable levels. Combining the leucocytes esterase and nitrite tests results
in higher specificity than using either test alone (Hooton, et al; 2000).
Urinalysis with microscopic examination for bacteria is
thus a useful test for the identification of bacteriuria.
1.2.7.3 URINE CULTURE
Although urine cultures are expensive, require laboratory expertise
and take 24-48 hours for results to become available, quantitative culture
remains the gold standard for diagnosis of UTI.
Quantitative
analysis of bacteria in urine culture was developed several decades ago (Hooton
et al; 2000) to establish reliable
criteria for discriminating between infection and contamination in asymptomatic
persons, with the expectation that asymptomatic infection might be associated
with pyelonephitis, hypertension, renal disease and complications of pregnancy (Zhanel and Harding, 1990). In
studies of ASB, counts of at least 105 colony-forming unit per
milliliter usually predicated persistently high levels of bacteriuria whereas
counts of less 105cfu/ml usually meant persistently low levels of
bacteriuria, (Hooton et al; 2000).
Diagnosis of ASB and UTI include the use of blood agar and either MacConkey
agar or a similar selective medium for routine urine culture. Therefore, the
presence of at least 105cfu/ml of the same urinary tract pathogen in
urine specimens has been widely adopted as the criterion identifying
potentially important bacteria in asymptomatic women.
1.2.8 COMMON ANTIBIOTICS
FOR ASB
Asymptomatic
bacteriuria is common. Populations with structural or functional abnormalities
of the genitourinary tract may have an exceedingly high prevalence of
bacteriuria (Schnarr and Smaill, 2008); but even healthy individuals frequently
have positive urine cultures. ASB is seldom associated with adverse outcomes.
Pregnant women (Okonko et al., 2010)
and individuals who are to undergo traumatic genitourinary interventions are at
risk for complications of bacteriuria and benefit from treatments, for other
populations, including most bacteriuria individuals, negative outcomes
attributable to ASB have been progression to UTI.
Antibiotics are the mainstay treatment for all forms of urinary
tract infections. The choice of antibiotic and length of treatment depend on
the patient’s history and the urine test that identify the causative bacterial.
The sensitivity test is especially useful in helping select the most effective
medication. It has been argued however, that the positive effect of antibiotic
therapy is mediated by an alternate mechanism such as modification of vaginal
flora, rather than eradication of bacteriuria.
Nitrofurantoin, however, which does not alter vaginal flora, is
effective in, preventing pyelonephitis in pregnancy. It is effective against E. coli; Enterococcus, Klebsiella and S
aureus. It is however not combined with quinolone antibiotic because of its
adverse effect.
UTI are often treated with different broad- spectrum
antibiotics even when one with a narrow spectrum of activity may be
appropriate. This is because of concerns about infection with resistant
organisms. Fluoroguinolones are preferred as initial agents for empiric therapy
of UTI in areas where resistance is likely to be of concern (Ngwai et al., 2010). This is because they have
high bacteriological and clinical cure rates, as well as low rates of
resistances among most common Uropathogens. Ciprofloxacin is one of the
broad-spectrum fluroquilnone frequently used to treat
urinary infections because of its excellent activity against
majority of urinary tract bacteria and particularly E. coli (Warren et al;
1999). Ciprofloxacin has a success rate of 90% in eradicating bacteriuria.
Other common antibiotics for asymptomatic and
symptomatic lower urinary tract infections include:- Cephalexin, Co-trimoxazole,
Gentamycin, Ampicillin, Streptomycin and Tetracycline. Tetracycline is however
not an appropriate agents to use in pregnancy because it leads to discoloration
of the teeth if taken after five months gestation (Schnarr and Smaill, 2008).
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