Vol. 114, November
THE JOURNAL OF UROLOGY
Printed in U.S.A.
Copyright © 1975 by The Williams & Wilkins Co.
RAPID MINIATURIZED TESTS FOR BACTERIURIA: MICROSTIX AND BACTURCUL T URINE TESTS CHESTER C. WINTER From the Diuision of Urolo{ly, Ohio State Uniuersity i'vfedical Center, Columbus, Ohio
ABSTHACT
for the presence of infection the was found far to be the Microstix and Bacturcult too many where urine were the such as in an office or outpatient clinic. Perhaps the last 2 tests would better results if urine samples were collected after at least 4 hours of incubation. time in the uH:,wuc, as suggested their
standard
A~A~ac,,A
Numerous tests for the presence of urinary bacteria have been made chemical reactions in infected urine, allowing diagnostic color changes and/or visible colonies of bacteria. The speed of testing varies from 30 seconds to 24 hours. Such tests are designed to allow the clinician to make an early judgment regarding urinary infection without waiting for the more time-consuming standard colony count-culture and drug testing, which 48 to 96 hours. Furthermore, no is necessary to conduct the tests. ,Judicial skill is in their clinical application, which of course falls short of regular countings and precise species identification. These factors have made the tests in evaluation of randomly collected urine samples in the physicians' offices and the hospitals. METHODS AND MATERIALS
Four tests for urinary infection were conducted for comparison of results in randomly collected urine specimens. Two were the standard studies of 1) microscopic examination of fresh urine sediment and 2) routine hospital laboratory culture-colony count of fresh urine and started within 1 hour of , urine collection, The remaining 2 were newly · introduced commercial tests-3) Microstix* and 4) Bacturcult. t Urine sediment microscopy was carried out centrifuging fresh urine for 2 minutes and examining a drop of the sediment with the for the presence of bacteria. Voided and catheterized specimens were included. for publication June Assoat annual of ciation, Miami Beach, * Ames Company, 1127 46514. Laborato:riesj 35 Ccrn.~netce Rd., Stan1ford, 06904
Standard hospital cultures were carried out for fresh voided and catheterized urine specimens and the results were interpreted as counts and identification in 48 hours. Antibiotic sensitivity tests for individual were conducted in subcultures when colony counts reached 10,000 or more per ml. The Microstix reagent strip contains 3 bands; a N-(1-napthyl) ethylenediamine impregnated band that turns a variable shade of red in the presence of bacteria that convert nitrate to nitrite to diazomum and 2 culture medium zones that allow of either total number of bacteria or gramcolonies of bacteria after 12 hours of incubation. The was moistened with urine and the nitrite reagent band was read after 30 seconds. The strip was then placed in a sterile cellophane envelope and incubated for 12 hours, after which the red density spots were counted for number of gram-negative bacteria and total count. The Bacturcult is a sterile plastic tube coated with special nutrient indicator-culture medium that is rinsed with the fresh urine specimen, sealed and incubated for 24 hours. Results were read through a transparent counting circle as to number of colonies and the color change was suggestive of the species. Yellow color indicated lactose fermenters such as Escherichia coli or enterococcus, rose to orange was characteristic of Klebsiella, staphylococcus or streptococcus and magenta signified urea-splitting organisms such as Proteus or Pseudomonas. RESULTS
There were 200 bladder urine lected: 122 micturition and 78 results of culture, microscopy, Microstix and Bacturcult were tabulated in 2 main of infected and uninfected and ·voided g:t1d catheterized (table 1). Tl:e res1_;lts s.lso
756
WINTER
were analyzed according to sex. In order to decide whether the patient had urinary infection , the standard laboratory culture was considered always correct. The results were rean alyzed by arbitrarily requiring at least 3 tests to be in agreement with more weight given to the standard hospital culturecolony count. A colony count of 10,000 or more was considered significant while lower counts were viewed as contamination. Even when the standard hospital cultures were relegated to a non-control status they showed a high degree of reliability, with 100 per cent accuracy among the uninfected urine samples , whether obtained by catheterization or voiding . A respectable accuracy was also found in the infected urine group of 93 and 92 per cent, respectively, for the catheterized and voided specimens. The over-all accuracy for standard hospital cultures in all patients when submitted to this method of analysis was 96 per cent (table 2). Microscopy did not fare as well as might be expected, with a general accuracy of 72 per cent. When the laboratory culture was not considered the control , the accuracy rate rose to 82 per cent. A large difference was found in the uninfected subgroups (voided 83 per cent and catheterized 60 per cent) and a significant spread was noted in the infected patients (66 per cent for micturition and 79 per cent when catheter collected). The tabulations broken down according to sex are shown in tables 3 and 4. The Microstix test was divided into nitrite test, total bacterial colony count and gram-negative colony count. When looked at as a whole 100 per cent accuracy was achieved in all uninfected catheterized urine specimens but accuracy dropped to 89 to 94 per cent when voided. The infected specimens averaged 72 to 76 per cent validity for catheter collections and only 60 to 65 per cent when voided (tables 1 and 2). The nitrite test fared poorly in the infected group (voided 29 to 37 per cent and catheterized TABLE
1. Study of 200 urine samples from both sexes-
per cent accuracy Uninfected
Culture Microscopy Microstix Bacturcult
Cat h.
Void .
Cath.
100 83 94 68
100
100 66 65 77
100 79 72 90
100 50
All Samples 100 72 83 71
2. Study of 200 urine samples from both sexes with at least 3 tests in agreement-per cent accuracy
TABLE
Uninfected
Culture Microscopy Microstix Bacturcult
Infe ction identification in male subjectsper cent accuracy Uninfec ted
Culture Mi croscopy Microstix Bacturcult
Infected
All
Void .
Cath.
Void .
Cath .
100 81 98 71
100 50* 100 0*
100 71 73 82
100 66 68 100
Samples 100 67 85 63
* Sample was too sma ll. TABLE 4 .
Infection identification in female subjectsper cent accuracy Uninfected
Culture Microscopy Microstix Bact urcult
Void . 100 86 89 62
Infect ed
All
Cath.
Void .
Cath.
100 62 100 60
100 63 58 73
100 62 73 66
Samples 100 68 80 65
48 to 52 per cent) and in the uninfected group (voided 93 to 96 per cent and catheterized 100 per cent). The total bacterial count was 78 to 86 per cent accurate from catheterized infected bladders but 82 to 84 per cent for voided urine samples. In non-infected urine samples the voided specimens came out 82 to 92 per cent while catheterization yielded 78 to 86 per cent accuracy (tables 5 to 8). The void-infected subjects showed 71 to 73 per cent accuracy when tested for gram-negative organisms. This test yielded better accuracy for . catheterized infected (87 to 96 per cent) and uninfected urine (void 92 to 96 per cent, catheter 100 per cent) . Finally, the Bacturcult test results ranged from 50 to 92 per cent accuracy. The infected group achieved 77 to 86 per cent accuracy for voided and 64 to 90 per cent for catheterized urine samples; while the uninfected were 68 to 84 per cent accurate when voided specimens were tested and .. 50 to 92 per cent if catheter collected (tables 1 and 2) . COMMENT
Infected
Void.
60
TABLE 3.
Infect ed
Void.
Cath.
Void.
Cath.
100 86 89 84
100 88 100 92
92 70 60 86
93 90 76 64
All Samples 96 82 81 82
It is difficult to achieve perfect accuracy in the determination of urinary infection regardless of the methodology used . Our studies confirm the high reliability of hospital laboratory cultures. Catheterized specimens yielded better accuracy in 35 subgroups while the voided specimens were better in only 14 categories. High power microscopy showed a range of 60 to 90 per cent accuracy, emphasizing the necessity for standard laboratory urine cultures if highest reliability is desired. The Microstix nitrite color indicator proved completely unpredictable in the presence of infection. This may be attributed in part to the timing of urine collections which were largely mid day . The nitrite reaction is best accomplished in the first morning specimen when sufficient in vivo incubation time has elapsed to allow highest bacte-
'l.
757
RAPID MINIATURIZED TESTS FOR BACTERIURIA TABLE
5. Bacterial identification with Microstix test in
both sexes-per cent accuracy Nitrite Uninfected urine: Voided Catheterized Infected urine: Voided Catheterized
Total Bacteria
Gm.-Neg. Bacteria
96 100
92 100
96 100
37 52
84 78
73 87
TABLE 8. Bacterial identification with Microstix test in
both sexes with at least 3 tests in agreementper cent accuracy
Uninfected urine: Voided Catheterized Infected urine: Voided Catheterized
Gm.-Neg. Bacteria
Nitrite
Total Bacteria
93 100
82 100
92 100
29 48
82 86
71 96
TABLE 6. Bacterial identification with Microstix test in
male subjects-per cent accuracy
Uninfected urine: Voided Catheterized Infected urine: Void Catheterized
TABLE
Nitrite
Total Bacteria
96 100
96 100
100 100
57 57
86 71
77 83
Gm.-Neg. Bacteria
7. Bacterial identification with Microstix test in
female subjects-per cent accuracy Nitrite Uninfected urine: Voided Catheterized Infected urine: Voided Catheterized
I,-
Total Bacteria
Gm.-Ng. Bacteria
95 100
84 100
89 100
22 50
83 80
71 89
rial concentration. However, when the urine was sterile the nitrite test was 89 to 100 per cent reliable . The total Microstix colony count (78 to 100 per cent) was less accurate than standard culture (92 to 100 per cent) but better than microscopy (60 to 90 per cent), while the gramnegative bacterial count varied more in its accuracy (71 to 100 per cent) and.showed poor predictability of infection in voided specimens. The Bacturcult test was surprisingly inaccurate when no infection was present (50 to 92 per cent) and too many falsely negative results were found in the presence of infection (10 to 36 per cent) . REFERENCES
CRAIG, W. A., KUNIN, C. M. and DEGROOT, J.: Evaluation of new urinary tract infection screening devices. Appl. Microbiol., 26: 196, 1973. MACKAY-SCOLLAY, E. M.: A simple quantitative and qualitative microbiological screening test for bacteriuria. J . Clin. Path., 22: 651, 1969.
THE JOURNAL OF UROLOGY
Printed in U.S.A.
Copyright © 1975 by The Williams & Wilkins Co.
RAPID MINIATURIZED TESTS FOR BACTERIURIA: MICROSTIX AND BACTURCUL T URINE TESTS CHESTER C. WINTER From the Diuision of Urolo{ly, Ohio State Uniuersity i'vfedical Center, Columbus, Ohio
ABSTHACT
for the presence of infection the was found far to be the Microstix and Bacturcult too many where urine were the such as in an office or outpatient clinic. Perhaps the last 2 tests would better results if urine samples were collected after at least 4 hours of incubation. time in the uH:,wuc, as suggested their
standard
A~A~ac,,A
Numerous tests for the presence of urinary bacteria have been made chemical reactions in infected urine, allowing diagnostic color changes and/or visible colonies of bacteria. The speed of testing varies from 30 seconds to 24 hours. Such tests are designed to allow the clinician to make an early judgment regarding urinary infection without waiting for the more time-consuming standard colony count-culture and drug testing, which 48 to 96 hours. Furthermore, no is necessary to conduct the tests. ,Judicial skill is in their clinical application, which of course falls short of regular countings and precise species identification. These factors have made the tests in evaluation of randomly collected urine samples in the physicians' offices and the hospitals. METHODS AND MATERIALS
Four tests for urinary infection were conducted for comparison of results in randomly collected urine specimens. Two were the standard studies of 1) microscopic examination of fresh urine sediment and 2) routine hospital laboratory culture-colony count of fresh urine and started within 1 hour of , urine collection, The remaining 2 were newly · introduced commercial tests-3) Microstix* and 4) Bacturcult. t Urine sediment microscopy was carried out centrifuging fresh urine for 2 minutes and examining a drop of the sediment with the for the presence of bacteria. Voided and catheterized specimens were included. for publication June Assoat annual of ciation, Miami Beach, * Ames Company, 1127 46514. Laborato:riesj 35 Ccrn.~netce Rd., Stan1ford, 06904
Standard hospital cultures were carried out for fresh voided and catheterized urine specimens and the results were interpreted as counts and identification in 48 hours. Antibiotic sensitivity tests for individual were conducted in subcultures when colony counts reached 10,000 or more per ml. The Microstix reagent strip contains 3 bands; a N-(1-napthyl) ethylenediamine impregnated band that turns a variable shade of red in the presence of bacteria that convert nitrate to nitrite to diazomum and 2 culture medium zones that allow of either total number of bacteria or gramcolonies of bacteria after 12 hours of incubation. The was moistened with urine and the nitrite reagent band was read after 30 seconds. The strip was then placed in a sterile cellophane envelope and incubated for 12 hours, after which the red density spots were counted for number of gram-negative bacteria and total count. The Bacturcult is a sterile plastic tube coated with special nutrient indicator-culture medium that is rinsed with the fresh urine specimen, sealed and incubated for 24 hours. Results were read through a transparent counting circle as to number of colonies and the color change was suggestive of the species. Yellow color indicated lactose fermenters such as Escherichia coli or enterococcus, rose to orange was characteristic of Klebsiella, staphylococcus or streptococcus and magenta signified urea-splitting organisms such as Proteus or Pseudomonas. RESULTS
There were 200 bladder urine lected: 122 micturition and 78 results of culture, microscopy, Microstix and Bacturcult were tabulated in 2 main of infected and uninfected and ·voided g:t1d catheterized (table 1). Tl:e res1_;lts s.lso
756
WINTER
were analyzed according to sex. In order to decide whether the patient had urinary infection , the standard laboratory culture was considered always correct. The results were rean alyzed by arbitrarily requiring at least 3 tests to be in agreement with more weight given to the standard hospital culturecolony count. A colony count of 10,000 or more was considered significant while lower counts were viewed as contamination. Even when the standard hospital cultures were relegated to a non-control status they showed a high degree of reliability, with 100 per cent accuracy among the uninfected urine samples , whether obtained by catheterization or voiding . A respectable accuracy was also found in the infected urine group of 93 and 92 per cent, respectively, for the catheterized and voided specimens. The over-all accuracy for standard hospital cultures in all patients when submitted to this method of analysis was 96 per cent (table 2). Microscopy did not fare as well as might be expected, with a general accuracy of 72 per cent. When the laboratory culture was not considered the control , the accuracy rate rose to 82 per cent. A large difference was found in the uninfected subgroups (voided 83 per cent and catheterized 60 per cent) and a significant spread was noted in the infected patients (66 per cent for micturition and 79 per cent when catheter collected). The tabulations broken down according to sex are shown in tables 3 and 4. The Microstix test was divided into nitrite test, total bacterial colony count and gram-negative colony count. When looked at as a whole 100 per cent accuracy was achieved in all uninfected catheterized urine specimens but accuracy dropped to 89 to 94 per cent when voided. The infected specimens averaged 72 to 76 per cent validity for catheter collections and only 60 to 65 per cent when voided (tables 1 and 2). The nitrite test fared poorly in the infected group (voided 29 to 37 per cent and catheterized TABLE
1. Study of 200 urine samples from both sexes-
per cent accuracy Uninfected
Culture Microscopy Microstix Bacturcult
Cat h.
Void .
Cath.
100 83 94 68
100
100 66 65 77
100 79 72 90
100 50
All Samples 100 72 83 71
2. Study of 200 urine samples from both sexes with at least 3 tests in agreement-per cent accuracy
TABLE
Uninfected
Culture Microscopy Microstix Bacturcult
Infe ction identification in male subjectsper cent accuracy Uninfec ted
Culture Mi croscopy Microstix Bacturcult
Infected
All
Void .
Cath.
Void .
Cath .
100 81 98 71
100 50* 100 0*
100 71 73 82
100 66 68 100
Samples 100 67 85 63
* Sample was too sma ll. TABLE 4 .
Infection identification in female subjectsper cent accuracy Uninfected
Culture Microscopy Microstix Bact urcult
Void . 100 86 89 62
Infect ed
All
Cath.
Void .
Cath.
100 62 100 60
100 63 58 73
100 62 73 66
Samples 100 68 80 65
48 to 52 per cent) and in the uninfected group (voided 93 to 96 per cent and catheterized 100 per cent). The total bacterial count was 78 to 86 per cent accurate from catheterized infected bladders but 82 to 84 per cent for voided urine samples. In non-infected urine samples the voided specimens came out 82 to 92 per cent while catheterization yielded 78 to 86 per cent accuracy (tables 5 to 8). The void-infected subjects showed 71 to 73 per cent accuracy when tested for gram-negative organisms. This test yielded better accuracy for . catheterized infected (87 to 96 per cent) and uninfected urine (void 92 to 96 per cent, catheter 100 per cent) . Finally, the Bacturcult test results ranged from 50 to 92 per cent accuracy. The infected group achieved 77 to 86 per cent accuracy for voided and 64 to 90 per cent for catheterized urine samples; while the uninfected were 68 to 84 per cent accurate when voided specimens were tested and .. 50 to 92 per cent if catheter collected (tables 1 and 2) . COMMENT
Infected
Void.
60
TABLE 3.
Infect ed
Void.
Cath.
Void.
Cath.
100 86 89 84
100 88 100 92
92 70 60 86
93 90 76 64
All Samples 96 82 81 82
It is difficult to achieve perfect accuracy in the determination of urinary infection regardless of the methodology used . Our studies confirm the high reliability of hospital laboratory cultures. Catheterized specimens yielded better accuracy in 35 subgroups while the voided specimens were better in only 14 categories. High power microscopy showed a range of 60 to 90 per cent accuracy, emphasizing the necessity for standard laboratory urine cultures if highest reliability is desired. The Microstix nitrite color indicator proved completely unpredictable in the presence of infection. This may be attributed in part to the timing of urine collections which were largely mid day . The nitrite reaction is best accomplished in the first morning specimen when sufficient in vivo incubation time has elapsed to allow highest bacte-
'l.
757
RAPID MINIATURIZED TESTS FOR BACTERIURIA TABLE
5. Bacterial identification with Microstix test in
both sexes-per cent accuracy Nitrite Uninfected urine: Voided Catheterized Infected urine: Voided Catheterized
Total Bacteria
Gm.-Neg. Bacteria
96 100
92 100
96 100
37 52
84 78
73 87
TABLE 8. Bacterial identification with Microstix test in
both sexes with at least 3 tests in agreementper cent accuracy
Uninfected urine: Voided Catheterized Infected urine: Voided Catheterized
Gm.-Neg. Bacteria
Nitrite
Total Bacteria
93 100
82 100
92 100
29 48
82 86
71 96
TABLE 6. Bacterial identification with Microstix test in
male subjects-per cent accuracy
Uninfected urine: Voided Catheterized Infected urine: Void Catheterized
TABLE
Nitrite
Total Bacteria
96 100
96 100
100 100
57 57
86 71
77 83
Gm.-Neg. Bacteria
7. Bacterial identification with Microstix test in
female subjects-per cent accuracy Nitrite Uninfected urine: Voided Catheterized Infected urine: Voided Catheterized
I,-
Total Bacteria
Gm.-Ng. Bacteria
95 100
84 100
89 100
22 50
83 80
71 89
rial concentration. However, when the urine was sterile the nitrite test was 89 to 100 per cent reliable . The total Microstix colony count (78 to 100 per cent) was less accurate than standard culture (92 to 100 per cent) but better than microscopy (60 to 90 per cent), while the gramnegative bacterial count varied more in its accuracy (71 to 100 per cent) and.showed poor predictability of infection in voided specimens. The Bacturcult test was surprisingly inaccurate when no infection was present (50 to 92 per cent) and too many falsely negative results were found in the presence of infection (10 to 36 per cent) . REFERENCES
CRAIG, W. A., KUNIN, C. M. and DEGROOT, J.: Evaluation of new urinary tract infection screening devices. Appl. Microbiol., 26: 196, 1973. MACKAY-SCOLLAY, E. M.: A simple quantitative and qualitative microbiological screening test for bacteriuria. J . Clin. Path., 22: 651, 1969.
