Introduction:
Urinary tract Infection (UTI) represents one of the most common diseases
encountered in medical practice today and occuring from the neonate to geriatric age group.1
UTI exists when pathogenic microorganisms are detected in the urine, urethra, bladder,
kidney or prostate. In most instances, growth of >105 organisms/ml from a properly collected
midstream “clean-catch” urine sample indicates infection.2 Bacterial infections of the urinary
tract, whether hospital acquired or community acquired, occur in all age groups in both
genders, and usually require urgent treatment.3
UTI’s often results in serious complications like secondary bacteremia and sepsis
leading to a rise in mortality in addition to enormous hospital costs.4 The resistant bacterial
strains are emerging and spreading throughout the world, mainly because of the extreme
genetic plasticity of the micro organisms themselves, the mobility of world population and
the heavy selective pressures of antimicrobial use.5
In all UTI cases, there is a need to initiate empirical antimicrobial treatment before
obtaining the microbiological results.6 The initiation of antimicrobial therapy in community
acquired UTI is empirical, so knowledge of the most common etiological agents isolated and
resistance pattern of the isolated pathogens is essential to provide clinically appropriate and
cost effective therapy. There exists a great need for antimicrobial resistance surveillance at
the local, national & international levels.7
Material and methods: Source of data
The present study was conducted in the department of Microbiology, Bowring and
Lady Curzon Hospital attached to Bangalore Medical College and research centre, Bengaluru
from june 2009 to feb 2010. A total of 600 suspected cases of UTI attending the outpatient
department and inpatients were studied for a period of one year.
Inclusion Criteria
Clinically suspected cases of urinary tract infection of both sexes and all age groups
admitted in the wards and cases attending the outpatient department.
Exclusion Criteria
Patients who were treated with the antibiotics were excluded from the study.
Collection of the sample
Fresh midstream urine samples were collected in universal sterile containers from all
cases. The samples were transported and processed in the laboratory without delay.
Processing
Microscopic examination
A clean grease free slide was taken and a drop of uncentrifuged urine was placed on it
and covered with the coverslip. It was examined under the low power and high power of the
microscope for the presence of pus cells and motile bacteria [Fig 1].
Culture
Each sample was plated onto 5% Sheep blood agar and MacConkey agar plates using
a calibrated loop, delivering 0.01ml of the sample. Plates were incubated aerobically at 370c
overnight and observed for the presence of significant bacteriuria (>105 org/ml) [Fig 2].
Plates showing significant bacteriuria were further processed for identification using standard
methods.8 Those plates showing insignificant bacteriuria and no growth (<105 org/ml) were
discarded.
Identification of bacterial pathogens was made on the basis of gram stain, hanging drop and
biochemical tests like catalase, oxidase, IMViC reactions, TSI, urease, mannitol motility &
fermentation, nitrate reduction and sugar fermentation tests[Fig 3].
Antibiotic susceptibility testing:
The conventional sensitivity method used in this study was modified Kirby- Bauer disc
diffusion method. Isolates were grown in peptone water at 370 C and turbidity was matched
with 0.5 McFarland standard. The lawn culture was done on Mueller Hinton agar plate and
antibiotic discs were placed[Fig 4]. The plates were incubated at 370C overnight and the
zones of inhibition were interpreted according to CLSI guidelines9. Antibiotic susceptibility
& culture media were evaluated regularly using ATCC strain (25922) of Escherichia coli.
The antibiotic discs and its strength used are6 :
Ampicillin
10 µg
Amikacin
30 µg
Amoxiclav
20/10 µg
Carbenicillin
100 µg
Cefotaxime
30µg
Cefpodoxime
10µg
Ciprofloxacin
5 µg
Cotrimoxazole
1.25/23.75 µg
Gatifloxacin
5 µg
Gentamicin
10 µg
Imipenem
10 µg
Norfloxacin
10 µg
Nitrofurantoin
300 µg
Nalidixic acid
30 µg
Pipera/tazobac
100 µg
Rapid method of susceptibility testing by MINI API
The rapid method used to test susceptibility pattern is MINI API by BIOMERIEUX
[Fig 5]. It consists of rapid ATB strips [Fig 6] made up of transparent, rigid, thermoformed
plastic and contains 16 cupules. Each strip carries a screen- printed code which is
automatically recognized by the strip reader. Each cupule contains a dehydrated antibiotic at
a given concentration. The first cupule serves as the growth control and contains no
antibiotic. The strips are inoculated with a bacterial suspension prepared in a semisolid
medium specific to ATB tests. The strips are incubated for 4 hours and is placed on the reader
and read automatically. The reader recognizes the strip code, carries out the measurements
and transfers them to the computer, which establishes the corresponding profile
(intermediate, Resistant, sensitive).10
Results:
Out of 600 cases, 320 (51.6%) were females and 280 (48.3%) were males. Male to
female ratio was 1:1.14. 24.16% of the patients belonged to the age group of ≤10 years
(71males and 74 females). 20.5% were of the age group 11-20years (60 males and 63
females). 16.3% were of the age group 21-30 years (45 males and 53 females). 12.6% were of
the age group 31-40 years (38 males and 38 females). Suspected UTI cases above 40 years
was relatively insignificant.
Age
Males
Females
Total
No
%
No
%
No
%
≤10
71
11.8
74
12.3
145
24.16
11-20
60
10.0
63
10.5
123
20.5
21-30
45
7.5
53
8.88
98
16.3
31-40
38
6.3
38
6.30
76
12.6
41-50
31
5.16
34
5.6
65
10.83
51-60
21
3.5
29
4.83
50
8.3
>60
14
2.3
29
4.83
43
7.1
280
46.56
320
53.44
600
100
Table A: Age and sex distribution of the study group
significant bacteria with pyuria is seen in 55 cases (9.1%), significant bacteriuria
without pyuria in 13 cases (2.1%), Pyuria without significant bacteriuria was seen in 1 case
(0.16%) and 88.5% cases with no pyuria and bacteriuria.
Findings
Total
Pyuria & bacteriuria
55
9.1
7.1 – 11.7
Bacteriuria alone
13
2.1
1.3 – 3.7
Pyuria alone
01
0.16
0.03 – 0.9
88.5
85.7 – 90.8
No
pyuria
&
no 531
%
95% CI
bacteriuria
Total no screened
600
100
Table B: Results of microscopy and culture
32.7% cases were from inpatients and 67.3% from outpatient department. Out of 196
inpatients, 23 cases (11.73%) showed culture positive . Out of 394 outpatients, 46 cases
(11.6%) showed culture positive.
A total of 69 uropathogens were isolated. Escherichia coli was the commonest uropathogen
isolated (73.9%), followed by Klebsiella pneumoniae (24.6%) and Citrobacter freundii
(1.4%).
Type of organism
No
Percentage
95% CI
Escherichia coli
51
73.9
65.6-85.2
Klebsiella pneumoniae
17
24.6
13.6-32.8
Citrobacter freundii
01
1.4
0.3-0.78
Total
69
100
Table C: Uropathogens isolated in the study
Escherichia coli was 100% sensitive to amikacin & imipenam and was least sensitive
to nalidixic acid (5.8%) & carbenicillin (11.7%). Klebsiella pneumoniae was highly sensitive
to imipenem (100%), piperacillin/tazobactum (82.3%), amikacin (70.5%) and least sensitive
to ampicillin (5.8%), carbenicillin (5.8%). Citrobacter was sensitive to imipenem alone.
ATCC strain of Esch.coli showed sensitivity to all the antibiotics used in this study.
Escherichia coli
Klebsiella spp
Citrobacter freundii
No
%
No
%
No
%
Ampicillin
10
19.6
01
5.8
0
0
Amikacin
51
100
12
70.5
0
0
Amoxiclav
21
41.1
03
17.6
0
0
Carbenicillin
06
11.7
01
5.8
0
0
Cefotaxime
17
33.3
03
17.6
0
0
Cefpodoxime
13
25.4
03
17.6
0
0
Ciprofloxacin
09
17.6
05
29.4
0
0
Gatifloxacin
08
15.6
07
41.1
0
0
Gentamicin
22
43.1
05
29.4
0
0
Cotrimoxazole
21
41.1
06
35.2
0
0
Imipenam
51
100
17
100
1
100
Nalidixic acid
03
5.8
02
11.7
0
0
Norfloxacin
08
15.6
06
35.2
0
0
Nitrofurantoin
34
66.6
06
35.2
0
0
Pipera/tazobac
48
94.1
14
82.3
0
0
Table D: Antibiotic sensitivity pattern of uropathogens isolated in the study
Discussion:
Laboratory diagnosis of UTI using urine cultures is based on the semi-quantitative counts of
organisms and identification of the isolates. It is important to note that urine cultures are reserved for
patients with complicated UTI or those who failed or relapsed after empirical therapy. In the
outpatient setting, symptomatic patients with uncomplicated UTI are usually treated empirically.
However, other investigations may be helpful and each primary care physician has his own strategy. If
empiric treatment is based on history alone then one would be treating at least 40% of patients without
UTI. This is because through history taking, the pretest probability of a UTI hardly exceeds sixty
percent.10
In the present study, UTI’s were more common in ≤ 10 years age group (20.2%), is not in
comparision with other studies as the number of cases referred
were more from the pediatric
department (24.16%). Mohammed Akram et al11 and Anbumani et al4 reported 20-49 years as the
commonest age group affected. females were more commonly affected (53.44%) than males
(46.56%), is in comparision with the study of Nwanze et al 12 (60%). Females are more commonly
affected because of the short urethra, its proximity to anus and its termination beneath the labia. All
this factors predisposes for the colonization of colonic gram negative bacilli 13. Significant bacteriuria
was seen in 11.5% of the study group, is in comparision with the study of Mohammed akram et al 11(
11.1%), Dimitrov TS et al14 (11.74%). Escherichia coli was the commonest uropathogen (73.9%)
isolated, is in comparision with the study of Katarzyna et al 6 (73%) and Semra Kurutupe et al7
(73.2%).The pattern of antibiotic susceptibilities, although subject to frequent changes, its assessment
is important for clinical and epidemiological purposes. This is because the resistance of various
organisms to antimicrobials poses a challenge to treat UTI since it decreases the effectiveness of
treatment and increases morbidity, mortality and cost of care.
Escherichia coli was highly sensitive to amikacin (100%) and imipenem (100%).Similar
findings were seen in the studies.15,16 It was less sensitive to ampicillin (19.6%), similar to the reports
of Hadiza et al15 (18%), is less compared to the study of Katarzyna et al6 (55%). Sensitivity to
cotrimoxazole was 41.1%, similar to the reports of Mohammed H Abu et al 17 (40.4%), is less
compared to the study of Katarzyna et al6(80.9%)
and Yvonne et al16(73.5%). Sensitivity to
norfloxacin was 15.6%. Similar findings was not found in other studies. This may be due to frequent
and inadvertent use of antibiotics empirically without any laboratory investigations.
Conclusion:
In the present study, the antibiotic sensitivity pattern gave a serious cause for concern
because the predominant uropathogens were less sensitive to commonly used antibiotics.
In occasions of complicated or recurrent UTI’s, the success of treatment depends on
prompt administration of appropriate antibiotics. Since the sensitivity pattern of uropathogens
are subjected to change during the course of time, it is important to do local hospital based
periodical assessment of it. This would allow early and appropriate management of UTI’s.
The rapid method for antibiotic susceptibility testing by MINI API is technically
simple, reliable(results are similar to disk diffusion method), early reporting (within 48
hours), and cost effective when compared to time consuming, technically demanding and
expensive conventional method.
Acknowledgement:
I would like to thank all the technicians of department of microbiology, Bowring hospital for
their constant help and support during the entire study.
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