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Regional differences in patterns of urinary tract infections
REGIONAL
DIFFERENCES
IN PA’TI’ERNS OF
URINARY TRACT INFECTIONS
ARNOLD
H. FRANZBLAU,
M.D.
Carlsbad Regional Medical Center, Carlsbad, New Mexico
ABSTRACT - The identity of 693 pathogenic bacilli isolated from 2,175 urine specimens cultured during a two-year period in southeastern New Mexico is presented along with results of sensitivity testing by Kirby-Bauer technique. The pattern of infections and sensitivity studies in hospitalized patients is compared with that of office patients and contrasted with results noted in other areas.
For a two-year period in southeastern New Mexico we compared the pathogenic bacteria identified in patients with urinary tract infections cultured in office practice with those cultured in the hospital. Standardized methods of collection, identification, and sensitivity testing were employed. This study presents the identity and antibiotic sensitivity patterns of 693 pathogenic bacilli isolated from 2,175 urine specimens cultured during the period March, 1972, to March, 1974. Blazevic, Stemper, and Matsen’ have drawn attention to the lack of comparative data in the literature in the area of urinary tract bacterial isolates and noted the epidemiologic value of such information. As Stamey’ has pointed out, “the difference between bacteriuria and nonbacteriuria is clearly a statistical consideration in which methodology is of critical importance. Failure to appreciate this point has caused considerable controversy.” Methods In the male group, most specimens were clean midvoided urine, some obtained by catheterization. In the female group almost all specimens were obtained by catheterization; office patients were catheterized with 8 F rigid catheters and hospital patients with 12 F plastic Robinson catheters. Each specimen obtained by either Presented at the Annual Meeting of the South Central Section, American Urological Association, Inc., Denver, Colorado, September, 1974.
30
method was handled in identical fashion in both office and hospital laboratory, and procedures were standardized in both locations. After collection in a sterile container, a calibrated 0.01 cc. drop of urine was placed in two locations on a blood agar plate and an eosin methylene blue plate, and in a tube of thioglycollate broth, and then incubated at 98.6” F. until the following day when colony counts were determined. Because of the catheterization of female patients, colony counts of lo4 per cubic millimeter were arbitrarily defined as a “clinically significant level of bacteria” and were submitted to sensitivity testing. Those of lo3 per cubic millimeter were reported as “not clinically significant,” and sensitivity testing was not done, with the exception of cultures from patients already receiving antimicrobial therapy. These were deemed “clinically significant” regardless of the colony count and subjected to sensitivity testing. Organisms were identified by standard commercially available bacteriologic methods (Enterotube or API). Cultures of Staphylococcus albus or Staphylococcus epidermidis, unless occurring in pure culture of high colony count, were considered to be contaminants and were reported as such. Sensitivity Testing Sensitivities were determined by the KirbyBauer technique which is an accepted method of antibiotic sensitivity testing utilizing a standardized single disk method.3 Sensitivity study reports were available the second day although,
UROLOGY
/ JULY 1975 / VOLUME
VI, NUMBER
1
TABLE 1.
in certain instances, the sensitivity studies could be read and reported as early as eight to twelve hours after being set up.
Total (Per Cent)
Hospital (Per Cent)
OEce (Per Cent)
Escherichia coli Proteus
67 14
62
72
14
14
KlebsiellaAerobacter* Pseudomonas Othersi
13 6
16 8 . ..
10 4
Organism Results Between March 1, 1972, and February 28, 1974, 2,175 urine cultures yielded 693 (32 per cent) “clinically significant” counts of bacilli; the vast majority of which were gram-negative organisms. Of these, 1,212 cultures from office patients yielded 377 (31 per cent) organisms and 963 cultures from hospitalized patients yielded 316 (33 per cent) organisms. We noted a constant percentage of positive cultures each year in hospital and office practice. The concept of follow-up urine cultures for serious urinary tract infections is well established in our area. Their identity and distribution are shown in Table I. We noted significant variations from hospital patients to office patients only in the E. coli cultures isolated, 62 per cent in the office and 72 per cent in the hospital. Since patients are often admitted directly to the hospital from the office and since follow-up office cultures are frequently done on hospital patients with chronic urinary tract infections, this variation is probably of no clinical significance. Our series is of short duration (two years) and no significant inferences can be drawn from the variations in the percentages of the various bacterial isolates from one year to the next. Blazevic, Stemper, and Martin’ reporting from Minneapolis on a ten-year series noted that there had been a slight decrease in E. coli isolates, and in 1964 to 1968 an increase in Klebsiella-Enterobatter isolates; also, since 1967 they noted an increase in Pseudomonas and Candida. Their aggregate results, 1961 to 1971, compared with this series are presented in Table II. Their results, however, reflect all cultures and are not
E. coli Proteus KlebsiellaEnterobacter Pseudomonas Citrobacter (Salmonella) Others
*Serratia included. tOthers includes Shigella, aureus.
.
Salmonella,
Staphylococcus
confined to organisms considered pathogenic. Compared with our New Mexico series, a difference in percentage of isolates of E. coli and Klebsiella-Enterobacter is noted. There is a close correlation of Proteus and Pseudomonas. In 1973 from the University of Western Ontario, Canada, Black and Hatch4 reported their results, and it is interesting to note that in the New Mexico series 67 per cent of the bacteria isolated were E. coli whereas in the Ontario series 46 per cent were E. coli (Table II). There also appears to be significant differences in the percentages of Klebsiella-Enterobacter in the two areas, while there is a close correlation in the percentages of Proteus and Pseudomonas identified. In 1973 from the University of Pennsylvania, Philadelphia, Mulholland and Bruun5 reported their results which, with the exception of Proteus and Pseudomonas, represented a wide variation from our results in New Mexico (Table II). From Bristol, England, in 1971 Gillespie et al. 6 showed a marked variation with our New Mexico series (Table II). It should be pointed out that Gillespie et al. 6 reported on coliform bacilli cultured in female outpatients.
Percentage of gram-negative bacilli isolated - comparison of geographic results
TABLE II.
Organism
Percentage of gram-negative bacilli isolated
-Comparison Minneapolis’
ofNew Mexico
-Comparison ofOntario** New Mexico
-----Comparison ofPhiladelphia 5 New Mexico
-Comparison ofBristol6 New Mexico
34 13
67
46 14
67 14
29
67
14
13
14
22 7
13
22
13
2
8
6
27 10
13
6
6
.
24
-cl
7
...
17
93
67
. 13
5
*Recomputation of data.
UROLOGY
/
JULY 1975
/
VOLUME VI, NUMBER
1
31
In comparing the foregoing studies we find a wide geographic variation in the E. coli isolates and a rather close correlation in Proteus and Pseudomonas (Table II).~s~-~Although it would appear that there are often striking differences in the bacterial isolates in various areas, one should be aware of possible variables. Factors such as different methods of bacteriologic identification of organisms from laboratory to laboratory, and changes in technique within the same laboratory as technologists change, might alter results to a slight degree. Of perhaps greatest interest to the practicing urologist are the results of sensitivity testing in vitro. What drug will achieve the best results, most rapidly, with the least hazard to the patient, and in the final analysis, at the more reasonable cost? The most commonly used antimicrobials available at the time of this study, compared with the percentage of sensitivity studies in which they were found to be positive, are listed in Table III; intermediate sensitivity zones, as reported by Kirby-Bauer technique, have been disregarded. Table III ranks the commonly isolated organisms and gives their in vitro sensitivities to twelve antimicrobial agents. Since E. coli represented two thirds of all urinary pathogens in our study, we noted that gentamicin, closely followed by nitrofurantoin, then colistin and nalidixic,acid were the most effective antimicrobials; followed by chloramphenicol, ampicillin, carbenicillin, tetracycline, sulfa, and kanamycin, and lastly cephalodecreasing rank of sensitivity sporin, in order in vitro.
of
There were no significant variations in susceptibility of organisms from year to year, or from office to hospital patients, no doubt due to the short duration (two years) of this study and the interchange of patients between office and hospital. Despite the use of a standardized technique, Kirby-Bauer, we would caution that the strength of the disks themselves - commercial generic disks as opposed to the free brand name disks offered by drug companies - may alter results, as might variables from technologist to technologist. Table III also demonstrates how antimicrobial sensitivities vary from area to area comparing our results with those of Bruun and Mulholland’ from Philadelphia, and Black and Hatch8 from Ontario. The most striking features in comparing New Mexico with Philadelphia and Ontario are the similarities; gentamicin is the most effective antimicrobial. Colistin, nitrofurantoin, and
32
UROLOGY
/ JULY1975 / VOLUMEVI,
NUMBER
1
nalidixic acid have a uniformly good performance record in all three areas. The differences are also striking, as for example sulfonamides, 94 per cent of Pseudomonas susceptible in Ontario compared with only 25 per cent susceptible in New Mexico.
identity of infecting organisms is made with various areas of North America and elsewhere. Contrasting patterns of bacterial susceptibility, as determined by Kirby-Bauer sensitivity studies, are presented. A plea is made for additional studies of this type to enhance our ability to treat urinary tract infections.
Comment This presentation serves to emphasize the need for urine cultures and standardized sensitivity studies in the treatment of urinary tract infections. A knowledge of the more common organisms extant in one’s own area along with the patterns of sensitivity studies can often be extremely valuable in deciding which antimicrobial to prescribe while awaiting laboratory results which should be available within fortyeight hours. Because of varying patterns of bacteria isolated in urine cultures from one locality to another and indeed from one hospital to another in the same city, it would be helpful to have these reported in the literature along with sensitivity study results. The antimicrobial described in flowing terms in the east may offer only mediocre results in the southwest. This study has confirmed our suspicions that occasional inability to achieve good results in antimicrobial therapy is inherent in the regional differences in bacterial isolates and variables in patterns of bacterial resistance. Summary This article presents a study of some 693 pathogenic bacteria isolated from 2,175 urine specimens cultured during a two-year period in southeastern New Mexico. A comparison of the
UROLOGY
/
JULY 1975 /
VOLUME VI, NUMBER 1
812 North Canal Street Carlsbad, New Mexico 88220 ACKNOWLEDGMENT.
Our appreciation to Henry Burdett, Director, David Kaplenk, Technician, and the staff of Federal Programs, Carlsbad, New Mexico Municipal School District, for technical assistance.
References 1. BLAZEVIC, D. J., STEMPER, J. E., and MATSEN, J. M.: Organisms encountered in urine cultures over a ten year period, Appl. Microbial. 23: 421 (1972). 2. STAMEY, T. A.: Urinary Infections, Baltimore, Williams & Wilkins Co., 1972, p. 1. 3. BAUER, A. W., KIRBY, M. M., SHEFWS, J. C., and TURK, M.: Antibiotic susceptibility testing by a standardized single disk method, Am. J. Clin. Pathol. 45: 493 (1966). 4. BLACK, W. A., and HATCH, L. A.: Gram-negative urinary tract isolates in southwestern Ontario, J. Urol. 109:692 (1973). 5. MULHOLLAND, S. G., and BRUUN, J, N.: A study of hospital urinary tract infections, ibid. 110: 245 (1973) 6. GILLESPIE, W. A., LEE, P. A., LINTON, K. B., and resistance of coliform ROWLAND, A. J.: Antibiotic bacilli in urinary tract infections acquired by women outside hospital, Lancet 2: 675 (1971). 7. BRUUN, J. N., and MULHOLLAND, S. G.: Antibiotic sensitivity of isolates from nosocomial and community acquired urinary tract infections, Urology I: 409 (1973). 8. BLACK, W. A., and HATCH, L. A. : Increasing sensitivity rates of urinary gram-negative bacilli to antimicrobials, J. Urol. 110:336 (1973).
33
DIFFERENCES
IN PA’TI’ERNS OF
URINARY TRACT INFECTIONS
ARNOLD
H. FRANZBLAU,
M.D.
Carlsbad Regional Medical Center, Carlsbad, New Mexico
ABSTRACT - The identity of 693 pathogenic bacilli isolated from 2,175 urine specimens cultured during a two-year period in southeastern New Mexico is presented along with results of sensitivity testing by Kirby-Bauer technique. The pattern of infections and sensitivity studies in hospitalized patients is compared with that of office patients and contrasted with results noted in other areas.
For a two-year period in southeastern New Mexico we compared the pathogenic bacteria identified in patients with urinary tract infections cultured in office practice with those cultured in the hospital. Standardized methods of collection, identification, and sensitivity testing were employed. This study presents the identity and antibiotic sensitivity patterns of 693 pathogenic bacilli isolated from 2,175 urine specimens cultured during the period March, 1972, to March, 1974. Blazevic, Stemper, and Matsen’ have drawn attention to the lack of comparative data in the literature in the area of urinary tract bacterial isolates and noted the epidemiologic value of such information. As Stamey’ has pointed out, “the difference between bacteriuria and nonbacteriuria is clearly a statistical consideration in which methodology is of critical importance. Failure to appreciate this point has caused considerable controversy.” Methods In the male group, most specimens were clean midvoided urine, some obtained by catheterization. In the female group almost all specimens were obtained by catheterization; office patients were catheterized with 8 F rigid catheters and hospital patients with 12 F plastic Robinson catheters. Each specimen obtained by either Presented at the Annual Meeting of the South Central Section, American Urological Association, Inc., Denver, Colorado, September, 1974.
30
method was handled in identical fashion in both office and hospital laboratory, and procedures were standardized in both locations. After collection in a sterile container, a calibrated 0.01 cc. drop of urine was placed in two locations on a blood agar plate and an eosin methylene blue plate, and in a tube of thioglycollate broth, and then incubated at 98.6” F. until the following day when colony counts were determined. Because of the catheterization of female patients, colony counts of lo4 per cubic millimeter were arbitrarily defined as a “clinically significant level of bacteria” and were submitted to sensitivity testing. Those of lo3 per cubic millimeter were reported as “not clinically significant,” and sensitivity testing was not done, with the exception of cultures from patients already receiving antimicrobial therapy. These were deemed “clinically significant” regardless of the colony count and subjected to sensitivity testing. Organisms were identified by standard commercially available bacteriologic methods (Enterotube or API). Cultures of Staphylococcus albus or Staphylococcus epidermidis, unless occurring in pure culture of high colony count, were considered to be contaminants and were reported as such. Sensitivity Testing Sensitivities were determined by the KirbyBauer technique which is an accepted method of antibiotic sensitivity testing utilizing a standardized single disk method.3 Sensitivity study reports were available the second day although,
UROLOGY
/ JULY 1975 / VOLUME
VI, NUMBER
1
TABLE 1.
in certain instances, the sensitivity studies could be read and reported as early as eight to twelve hours after being set up.
Total (Per Cent)
Hospital (Per Cent)
OEce (Per Cent)
Escherichia coli Proteus
67 14
62
72
14
14
KlebsiellaAerobacter* Pseudomonas Othersi
13 6
16 8 . ..
10 4
Organism Results Between March 1, 1972, and February 28, 1974, 2,175 urine cultures yielded 693 (32 per cent) “clinically significant” counts of bacilli; the vast majority of which were gram-negative organisms. Of these, 1,212 cultures from office patients yielded 377 (31 per cent) organisms and 963 cultures from hospitalized patients yielded 316 (33 per cent) organisms. We noted a constant percentage of positive cultures each year in hospital and office practice. The concept of follow-up urine cultures for serious urinary tract infections is well established in our area. Their identity and distribution are shown in Table I. We noted significant variations from hospital patients to office patients only in the E. coli cultures isolated, 62 per cent in the office and 72 per cent in the hospital. Since patients are often admitted directly to the hospital from the office and since follow-up office cultures are frequently done on hospital patients with chronic urinary tract infections, this variation is probably of no clinical significance. Our series is of short duration (two years) and no significant inferences can be drawn from the variations in the percentages of the various bacterial isolates from one year to the next. Blazevic, Stemper, and Martin’ reporting from Minneapolis on a ten-year series noted that there had been a slight decrease in E. coli isolates, and in 1964 to 1968 an increase in Klebsiella-Enterobatter isolates; also, since 1967 they noted an increase in Pseudomonas and Candida. Their aggregate results, 1961 to 1971, compared with this series are presented in Table II. Their results, however, reflect all cultures and are not
E. coli Proteus KlebsiellaEnterobacter Pseudomonas Citrobacter (Salmonella) Others
*Serratia included. tOthers includes Shigella, aureus.
.
Salmonella,
Staphylococcus
confined to organisms considered pathogenic. Compared with our New Mexico series, a difference in percentage of isolates of E. coli and Klebsiella-Enterobacter is noted. There is a close correlation of Proteus and Pseudomonas. In 1973 from the University of Western Ontario, Canada, Black and Hatch4 reported their results, and it is interesting to note that in the New Mexico series 67 per cent of the bacteria isolated were E. coli whereas in the Ontario series 46 per cent were E. coli (Table II). There also appears to be significant differences in the percentages of Klebsiella-Enterobacter in the two areas, while there is a close correlation in the percentages of Proteus and Pseudomonas identified. In 1973 from the University of Pennsylvania, Philadelphia, Mulholland and Bruun5 reported their results which, with the exception of Proteus and Pseudomonas, represented a wide variation from our results in New Mexico (Table II). From Bristol, England, in 1971 Gillespie et al. 6 showed a marked variation with our New Mexico series (Table II). It should be pointed out that Gillespie et al. 6 reported on coliform bacilli cultured in female outpatients.
Percentage of gram-negative bacilli isolated - comparison of geographic results
TABLE II.
Organism
Percentage of gram-negative bacilli isolated
-Comparison Minneapolis’
ofNew Mexico
-Comparison ofOntario** New Mexico
-----Comparison ofPhiladelphia 5 New Mexico
-Comparison ofBristol6 New Mexico
34 13
67
46 14
67 14
29
67
14
13
14
22 7
13
22
13
2
8
6
27 10
13
6
6
.
24
-cl
7
...
17
93
67
. 13
5
*Recomputation of data.
UROLOGY
/
JULY 1975
/
VOLUME VI, NUMBER
1
31
In comparing the foregoing studies we find a wide geographic variation in the E. coli isolates and a rather close correlation in Proteus and Pseudomonas (Table II).~s~-~Although it would appear that there are often striking differences in the bacterial isolates in various areas, one should be aware of possible variables. Factors such as different methods of bacteriologic identification of organisms from laboratory to laboratory, and changes in technique within the same laboratory as technologists change, might alter results to a slight degree. Of perhaps greatest interest to the practicing urologist are the results of sensitivity testing in vitro. What drug will achieve the best results, most rapidly, with the least hazard to the patient, and in the final analysis, at the more reasonable cost? The most commonly used antimicrobials available at the time of this study, compared with the percentage of sensitivity studies in which they were found to be positive, are listed in Table III; intermediate sensitivity zones, as reported by Kirby-Bauer technique, have been disregarded. Table III ranks the commonly isolated organisms and gives their in vitro sensitivities to twelve antimicrobial agents. Since E. coli represented two thirds of all urinary pathogens in our study, we noted that gentamicin, closely followed by nitrofurantoin, then colistin and nalidixic,acid were the most effective antimicrobials; followed by chloramphenicol, ampicillin, carbenicillin, tetracycline, sulfa, and kanamycin, and lastly cephalodecreasing rank of sensitivity sporin, in order in vitro.
of
There were no significant variations in susceptibility of organisms from year to year, or from office to hospital patients, no doubt due to the short duration (two years) of this study and the interchange of patients between office and hospital. Despite the use of a standardized technique, Kirby-Bauer, we would caution that the strength of the disks themselves - commercial generic disks as opposed to the free brand name disks offered by drug companies - may alter results, as might variables from technologist to technologist. Table III also demonstrates how antimicrobial sensitivities vary from area to area comparing our results with those of Bruun and Mulholland’ from Philadelphia, and Black and Hatch8 from Ontario. The most striking features in comparing New Mexico with Philadelphia and Ontario are the similarities; gentamicin is the most effective antimicrobial. Colistin, nitrofurantoin, and
32
UROLOGY
/ JULY1975 / VOLUMEVI,
NUMBER
1
nalidixic acid have a uniformly good performance record in all three areas. The differences are also striking, as for example sulfonamides, 94 per cent of Pseudomonas susceptible in Ontario compared with only 25 per cent susceptible in New Mexico.
identity of infecting organisms is made with various areas of North America and elsewhere. Contrasting patterns of bacterial susceptibility, as determined by Kirby-Bauer sensitivity studies, are presented. A plea is made for additional studies of this type to enhance our ability to treat urinary tract infections.
Comment This presentation serves to emphasize the need for urine cultures and standardized sensitivity studies in the treatment of urinary tract infections. A knowledge of the more common organisms extant in one’s own area along with the patterns of sensitivity studies can often be extremely valuable in deciding which antimicrobial to prescribe while awaiting laboratory results which should be available within fortyeight hours. Because of varying patterns of bacteria isolated in urine cultures from one locality to another and indeed from one hospital to another in the same city, it would be helpful to have these reported in the literature along with sensitivity study results. The antimicrobial described in flowing terms in the east may offer only mediocre results in the southwest. This study has confirmed our suspicions that occasional inability to achieve good results in antimicrobial therapy is inherent in the regional differences in bacterial isolates and variables in patterns of bacterial resistance. Summary This article presents a study of some 693 pathogenic bacteria isolated from 2,175 urine specimens cultured during a two-year period in southeastern New Mexico. A comparison of the
UROLOGY
/
JULY 1975 /
VOLUME VI, NUMBER 1
812 North Canal Street Carlsbad, New Mexico 88220 ACKNOWLEDGMENT.
Our appreciation to Henry Burdett, Director, David Kaplenk, Technician, and the staff of Federal Programs, Carlsbad, New Mexico Municipal School District, for technical assistance.
References 1. BLAZEVIC, D. J., STEMPER, J. E., and MATSEN, J. M.: Organisms encountered in urine cultures over a ten year period, Appl. Microbial. 23: 421 (1972). 2. STAMEY, T. A.: Urinary Infections, Baltimore, Williams & Wilkins Co., 1972, p. 1. 3. BAUER, A. W., KIRBY, M. M., SHEFWS, J. C., and TURK, M.: Antibiotic susceptibility testing by a standardized single disk method, Am. J. Clin. Pathol. 45: 493 (1966). 4. BLACK, W. A., and HATCH, L. A.: Gram-negative urinary tract isolates in southwestern Ontario, J. Urol. 109:692 (1973). 5. MULHOLLAND, S. G., and BRUUN, J, N.: A study of hospital urinary tract infections, ibid. 110: 245 (1973) 6. GILLESPIE, W. A., LEE, P. A., LINTON, K. B., and resistance of coliform ROWLAND, A. J.: Antibiotic bacilli in urinary tract infections acquired by women outside hospital, Lancet 2: 675 (1971). 7. BRUUN, J. N., and MULHOLLAND, S. G.: Antibiotic sensitivity of isolates from nosocomial and community acquired urinary tract infections, Urology I: 409 (1973). 8. BLACK, W. A., and HATCH, L. A. : Increasing sensitivity rates of urinary gram-negative bacilli to antimicrobials, J. Urol. 110:336 (1973).
33