ORIGINAL ARTICLE
EVALUATION OF RAPID METHOD FOR THE DETECTION OF BACTERIURIA
USING CONVENTIONAL CULTURE AS REFERENCE STANDARD
Lakshmi N1, Maheswaran R2
HOW TO CITE THIS ARTICLE:
Lakshmi N, Maheswaran R. “Evaluation Of Rapid Method For The Detection Of Bacteriuria Using Conventional
Culture As Reference Standard”. Journal Of Evolution Of Medical And Dental Sciences 2013; Vol2, Issue 50,
December 16; Page: 9798-9800.
ABSTRACT:INTRODUCTION: A new commercially available method for detection of bacteriuria is
compared to a conventional semi-quantitative bacteriology method. Screening methods are used to
detect significant level of pathogenic microorganisms in urine specimens. This rapid method offers
the advantages of both rapidly reporting the result as well as controlling costs1. On the basis of these
findings, it is recommended to test the urine samples of all patients with suspected urinary tract
infections by the rapid method and confirm and obtain the sensitivity pattern for the positive
findings. Using this method we can get instant results and the patient would receive prompt
appropriate treatment2.MATERIALS & METHODS: 600 mid-stream specimens of urine were tested
by using Urocolor dipstick strips. Results for three infection associated markers- glucose,nitrite and
pus cells were compared with the results of conventional laboratory culture &
microscopy.RESULTS: Of the 600 urine samples obtained 136 were positive and 464 negative for
infection associated markers whereas 166 were positive and 434 negative by culture. CONCLUSION:
This study had shown that the combination of strip test for nitrite, glucose and pus cells raised the
sensitivity to 97%, and among the strip negative results there is a high probability that the patient
does not have UTI.
INTRODUCTION:Urine is one of the most common samples submitted to the microbiology
laboratory for testing. Quantitative urine culture represents the gold standard3 for the laboratory
diagnosis ofurinary tract infection which is a labour-intensive, time consuming & expensive activity.
Over 60% of all samples processed show no evidence of significant bacterial growth.
Generation of a final negative culture report within a short time of specimen receipt is
beneficial. A positive result requires urine culture and sensitivity for confirmation and treatment.
Use of a rapid screen would be beneficial to the patient and the physician and reduce laboratory
workload.
MATERIALS & METHODS:600 mid-stream specimens of urine were received over a five month
period (between 1.2.2011 and 1.7.2011) from the departments of Medicine, Surgery, Obstetrics and
Gynaecology at the Kempegowda Institute of Medical Sciences and Research Hospital (KIMSH)
Laboratory. Samples were also received from general practitioners of that area.
These samples were tested by using the SD urocolor dipstick strips (Standard Diagnostics
Inc). Urine obtained in a clean dry container was mixed well before testing. The test area of the strip
was charged with fresh urine sample and removed immediately to avoid dissolving out of reagents.
The strip was placed on tissue paper to remove excess urine and was kept in a horizontal position to
prevent possible mixing of chemicals from adjacent test areas. The test areas were compared with
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Page 9798
ORIGINAL ARTICLE
the corresponding colour chart on the bottle label and read visually at 60 seconds. The used strips
were discarded.
RESULTS:Out of the 600 samples 136 were positive for three infective markers, 25 were nitrate
negative but glucose and pus cells positive, five were indeterminate and 434 were negative for all
three infective markers. 72.3% (434/600) all specimens were strip negative for nitrite, glucose and
pus cells. The positive cases were confirmed with culture.
Of the 600 samples 166 were culture positive, 70 samples shows no significant bacteriuria
and 63 samples shows contamination (more than three organisms).
ISOLATE
CULTURE
GRAM
BTS
GLUCOSE
NITRATE
PUS CELLS
E. coli
Total [166] 28%
[52] 9%
[40] 76%
Total [136] 22.7%
[44] 85%
[50] 96%
[34] 65%
[47] 90%
Klebsiella
[56] 93%
[53] 5%
[50] 92.5%
Citrobacter
[12] 2%
[10] 83.3%
[11] 92%
[44] 85%
[55] 98%
[48] 86%
[50] 92.5%
[45] 80%
[12] 105%
[11] 92%
[11] 92%
[11] 92%
[4] 100%
Nil
Proteus
[4] 75%
[2] 50%
[2.6] 67%
[2.6] 6%
Pseudomonas
[3] 5%
[3] 100%
[2.6] 67%
[3] 100%
[2] 67%
67%
Staph. aureus
[13] 2%
[6] 46%
[8] 62%
[12] 92%
[6] 62%
CONS
[9] 115%
[8] 89%
[6] 69%
[9] 100%
67%
[17] 100%
[3] 8%
Enterococci
[17] 3%
[13] 76%
[12] 76%
[12] 76%
TOTAL
166
135
136
162
104
Comparison of conventional culture & biochemical test strip (BTS Urocolor)
for significant isolates
[4] 100%
[3] 100%
[12] 92%
[9] 100%
[16] 94%
147
DISCUSSION:With the present problem of constantly increasing laboratory workflow, there is a real
need to economize on the time spent performing unnecessary testing3. Two- thirds of all urine
specimens sent to the laboratory in this study comes from various departments, and only 28% of all
the specimens received were subsequently confirmed to have significantly bacteriuria. 72.3% of all
specimens were strip negative for nitrite, glucose and pus cells. The cost of the reagent strip test is
approximately Rs6.50 much less than the cost of processing the specimen in the laboratory. The
method is therefore cost effective with the advantages,that a negative urine sample is rapidly
identified and unnecessary drug treatment is avoided with consequent cost saving. Through this
method the general practitioner would have instant results thus the patient would receive
immediate and appropriate treatment. Conventional culture technique requires more than 18 - 24
hours for obtaining an accurate colony count. It represents a labor-intensive, time consuming and
expensive activity in which over 60% of all samples processed show no evidence of significant
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Page 9799
ORIGINAL ARTICLE
bacterial growth. Negative culture report after several hours of receipt of specimen is a disadvantage
of conventional culture.
So a rapid report of a negative result can be decisive in improving patient management. Use
of screens to detect significant levels of pathogenic micro organisms in urine specimens offers the
advantages to both rapidly reporting results and controlling costs, and also beneficial to the patients,
the physician and the laboratory. Nitrite, glucose, protein were all negative for clear urine. Positive
test strips compared with conventional culture good correlation seen in BTS and only culture for
positive strips. The aim of this study was to reduce the proportion of culture negative urines arriving
in the laboratory by producing local evidence based guidelines for the use of urine dipstick testing.
No special equipments are needed for screening urine samples so it can also be done in field
conditions.
BIBLIOGRAPHY:
1. Clinical relevance of culture versus screens for the detection of microbial pathogens in urine
specimens. The American Journal of Medicine. Volume 83,Issue 4, October 1987,pages 739745.
2. Diagnostic value and cost utility analysis for urine Grams stain and urine microscopic
examination as screening test for UTI. Department of laboratory medicine, Faculty of medicine,
Chulalongkorn University. 1030 Bangkok, 25-10-2004.
3. Validation of a method for the rapid diagnosis of UTI suitable for use in general practice. Br J
Gen - Pract- 1990. Oct: 40(339): 403-405.
AUTHORS:
1. Lakshmi N.
2. Maheswaran R.
PARTICULARS OF CONTRIBUTORS:
1. Associate
Professor,
Department
of
Microbiology, Sapthagiri Institute of Medical
Sciences and Research Centre, Bangalore.
2. HOD & Professor, Department of Community
Medicine, Sapthagiri Institute of Medical
Sciences and Research Centre, Bangalore.
NAME ADRRESS EMAIL ID OF THE
CORRESPONDING AUTHOR:
Dr. Lakshmi N.
Associate Professor,
Department of Microbiology,
Sapthagiri Institute of Medical Sciences and
Research Centre, Bangalore – 560090.
Email –drlakshmi53@gmail.com
Date of Submission: 11/11/2013.
Date of Peer Review: 12/11/2013.
Date of Acceptance: 20/11/2013.
Date of Publishing: 12/12/2013
Journal of Evolution of Medical and Dental Sciences/Volume 2/Issue 50/ December 16, 2013
Page 9800