1990, The British Journal of Radiology, 63, 532-534
Bacterial contamination of contrast media stored after opening By *D. Lisle, M B , BS, * t J . F. Ratcliffe, FRCS, FRCR, t J . Faoagali, FRCPA and t S . Cherian, M B , BS 'Department of Radiology, Royal Children's Hospital, Brisbane, tDepartment of Radiology, University of Queensland and tDepartment of Microbiology, Royal Brisbane Hospital, Queensland, Australia {Received September 1989 and in revised form January 1990)
Abstract. A barium suspension, iohexol, iopamidol and ioxaglate which were diluted with tapwater and 0.9% NaCl and dextrose saline (4% and 0.18%) were made into aliquots of 10 ml and stored at 4°C, room temperature and 37°C for 8 weeks. Regular handling and bacterial cultures were performed. These studies confirmed that environmental organisms do contaminate these solutions and that they also support viable organisms, but do not become significantly colonized at room temperature or 4°C. The solutions should be stored at room temperature or at 4°C. The diluted barium solution was the contrast medium least contaminated and if it is not contra-indicated for other reasons should be used in preference to low osmolality water soluble contrast media on the basis of its cost, radiological contrast and low microbial contamination rate.
Low osmolality water soluble (LOWS) contrast media have been shown to be suitable for gastro-intestinal studies in animals (Ginai, 1985), adults (Bell et al, 1987) and children and infants (Ratcliffe, 1986; Cohen, 1987). The expense of LOWS media prohibits their general use in gastro-intestinal radiology but there are certain clinical conditions in which their use is desirable. One practical way of reducing the cost of LOWS media for this purpose is to use medium left over from other investigations. The patient in whom it is necessary to use LOWS media in the gastro-intestinal tract may be at risk if contrast medium which is seriously contaminated with bacteria is used. This paper reports an experiment to identify the organisms which contaminate opened contrast media bottles which were stored and handled in a non-sterile manner to determine whether significant colonization occurs. Materials and methods
Three LOWS contrast media, one barium suspension and two solutions for intravenous infusion were tested. They were iohexol (Omnipaque 300, Sterling Pharmaceuticals), iopamirlol (Iopamiro 300, Schering Ltd), ioxaglate (Hexabrix 32, May and Baker), a barium suspension (Tixobar, Astra Pharmaceuticals), normal saline (0.9% NaCl, Travenol) and dextrose saline (4% dextrose and 0.18% NaCl, Travenol). Testing was performed at three different temperatures in the departmental refrigerator (0-4°C), at room temperature (15-22°C) and in the departmental contrast medium wanning oven (37°C) over a period of 8 weeks. The contrast media were diluted to concentrations commonly used in paediatric radiology using tapwater as set out in Table I to a volume of 300 ml for each test Address to Dr J. Ratcliffe, Department of Radiology, Royal Children's Hospital, Brisbane, Queensland, 4029, Australia. 532
liquid. Thirty millilitres of each liquid were separated into three 10 ml aliquots (one aliquot in each temperature environment) and put into sealed sterile containers which remained unopened for the 8 weeks. A further 30 ml of each liquid were divided into 10 ml aliquots and placed in sterile containers and sent immediately to the laboratory. The remaining 240 ml of each test liquid were divided into three 80 ml aliquots and placed in clean unused standard pharmacy bottles made of clear glass with plastic screw tops and each stored in the three temperature environments for 8 weeks. Every 7 days each of the 18 bottles was shaken, inspected and opened and 10 ml of the test liquid were removed with a syringe and aspirating cannula unique for each liquid and placed in a sterile container and sent to the laboratory. All the manipulations were done by one of the group (D.L.) and, in order to mimic the practice in radiology departments, no anti-bacterial precautions were taken. Hands were not washed and no mask was worn. The syringes and aspirating cannulae were stored in a clean and non-sterile area.
Table I. Solutions under study 4% Dextrose+ 0.18% NaCl 0.9% NaCl 75 ml of Tixobar 100% w/v 150 ml of Iohexol 300 mg I/ml 150 ml of Iopamidol 300 mg I/ml 150 ml of Hexabrix 300 mg/ul
Undiluted 300 ml Undiluted 300 ml + 225 ml of tapwater = 300 ml +150 ml of tapwater = 300 ml + 150 ml of tapwater = 300 ml + 150 ml of tapwater = 300 ml
The British Journal of Radiology, July 1990
Bacterial contamination of contrast media
All the samples sent to the laboratory were labelled in a code known only to the operator (D.L.). In the laboratory each 10 ml aliquot was inspected and mixed with 10 ml of tryptone soy broth and incubated at 35°C for 3 weeks. Direct plating of samples on receipt in the laboratory was not performed because all the solutions were crystal clear and there was insufficient sample to direct plate filter and culture in broth. The samples were inspected daily and if they became cloudy a gram stain was performed on the cloudy sample which was subcultured onto blood agar (5% horse blood) and MacConkey agar which were incubated at 35°C in air for 48 h and examined for bacterial growth. All organisms were identified using standard methods (Lennette et al, 1985) including the A.P.I. system (Vercieu, France). Results
Only the barium suspension became cloudy on shaking. No cloudiness or other abnormality was observed with the naked eye in any of the solutions during the course of the experiment. Fourteen different organisms were cultured from the samples submitted to the laboratory. One-third (5/18) of the samples mixed in an unsterile manner but then sealed for 8 weeks contained organisms, whereas twothirds of the samples in bottles opened weekly (84/144) were contaminated.
The distribution of infecting organisms is shown in Table II. The most frequently found organism was Bacillus species (mainly B. cereus). Micrococci were
found in the liquids kept at 4°C in the refrigerator. Overall contamination rates were similar in all three temperature environments. The same organism is found more frequently in samples of different liquids taken on the same day than in samples taken from the same liquid over several weeks. This form of transmission indicates that inoculation is likely to occur during handling, rather than persisting because of colonization of the bulk of the contrast medium. The exception may be micrococci in iohexol at 37°C. Discussion
Previous studies on the effect of contrast media on bacteria have been designed because of the fear that contrast media injected into or excreted into body cavities might interfere with the later microbiological diagnosis and identification of infection. Results are difficult to interpret, but in one study it was shown that conventional high osmolality contrast media tend to be antibacterial, whereas LOWS media tend to be less so (Dawson et al, 1983). The purpose of this study was to observe which bacteria contaminate or colonize contrast media in an X-ray department if the contrast media are handled in a non-sterile manner. The need for this study was gener-
Table II. The distribution of organisms cultured from 144 samples at weekly intervals at three different temperatures Week Cold 4% Dextrose 0.9% Saline Tixobar Iohexol Iopamidol Ioxaglate Room temperature 4% Dextrose 0.9% Saline Tixobar Iohexol Iopamidol Ioxaglate 37°C 4% Dextrose 0.9% Saline Tixobar Iohexol Iopamidol Ioxaglate
1
2
3
4
5
6
B P B
B P S/P P
B S
S B A B
R
R
A
2 B
B P B
S D S 4 C B
B M 5
D B
B
B
M/S B
M B
P P P
P P
P
3 A S
M B A B B
B B S B B
M P B
s
M
B S B
8
R
1 B B B B
7
M/D M B
M/C M R
R M
M
M 6
B
M B
B
B = Bacillus species (34); P = Pseudomonas stuzeri (12); S = Staphylococci epidermidis (10); M = Micrococcus species (14); R = Propionibacteria species (5); D = Diptheroid (3); A = Pseudomonas acidovorans (4); C = Acinetobacter calcoaceticus species (2); 1 = Flavobacteria species (1); 2 = Streptococci acremoris (1); 3 = Pasturella species (1); 4 = Pseudomonas species (1); 5 = Aerobic gram positive rods; 6 = Staphylococci aureus (1). Vol. 63, No. 751
533
D. Lisle, J. F. Ratcliffe, J. Faoagali and S. Cherian
ated by the expensive waste of LOWS contrast media in a paediatric X-ray department where frequently only a part of an ampoule or bottle of LOWS contrast medium is used. It has been our practice in the past to use a fresh container for each new patient and to discard any residual contrast medium at the end of each investigation. In our department it is fairly common to use LOWS media for gastro-intestinal studies in babies, infants and children and in these investigations the same degree of sterility as is required for intravascular or subarachnoid use is not required. We usually use LOWS media at dilutions almost equivalent in osmolality to plasma and therefore used the intravenous fluids (dextrose saline and normal saline) for comparison. We also used Tixobar at a 25% strength in babies in whom it is not contra-indicated. It is not our practice to use sterilized barium suspensions. It was initially anticipated that the dextrose saline would be quickly contaminated and permanently colonized and that this would act as a control. It was also expected that the normal saline which is relatively biologically inert would be contaminated as frequently as the contrast media but would not support bacterial growth. Both these expectations proved to be false and we have no explanation for the failure to identify organisms in dextrose saline and normal saline. Dilution and manipulation of the test liquids was performed in as "normal" a non-sterile manner as possible but in order to reduce individual variability these manipulations were performed by only one author (D.L.). The results show that all contrast media are easily contaminated and can support viable organisms more easily than do either dextrose saline or normal saline. Transmission of contaminating organisms by the operator at the time of sampling seems to be more important at room temperature and in cold solutions than is persistent colonization of contrast media. Persistent colonization does not seem to occur at room tempature or at 4°C. Bacillus species were the most frequent contaminating organism at all temperatures and may have colonized ioxaglate at 37°C. Micrococci were found mainly at 37°C and may have colonized iohexol at this temperature. Tixobar in a 25% suspension supports contaminants less well than do LOWS media at all three temperatures and there was no evidence of colonization of Tixobar.
534
This suggests that careful handling—using sterile equipment and sterile water for dilution at the time of investigation and storage at room temperature or at 4°C—may be more important in reducing the incidence of contamination of LOWS media for gastro-intestinal studies than the fact that the container had been opened and its contents part used in the past. Because LOWS contrast media at 37°C may support the growth of environmental micro-organisms, it is important to store opened containers at 4°C to minimize the multiplication of contaminating micro-organisms. Conclusion 1. Opened bottles of LOWS contrast media stored in the refrigerator or at room temperature may be used for gastro-intestinal studies providing clean equipment is used on each occasion. 2. Dilute Tixobar is preferable, from a microbiological point of view, to LOWS media isosmolar to plasma, providing the gastro-intestinal tract is intact. 3. Particular care should be taken not to keep opened bottles (or damaged bottles or ampoules) of LOWS media in warming ovens, especially if these media are to be used parenterally. References BELL, MCKINSKY & MILLS, 1987. Iopamidol in the diagnosis of
suspected upper G.I. perforation. Clinical Radiology, 38, 165-168. COHEN, M. D., 1987. Choosing contrast media for the evaluation of the gastro-intestinal tract of neonates and infants. Radiology, 162, 447-456. COWAN,
S. T.
& STEELE,
K.
J.,
1975. Manual for
the
Identification of Medical Bacteria, 2nd edn (Cambridge University Press, Cambridge). DAWSON, P., BACKER, A. & HOLTON, J. M., 1983. The effect of
contrast media on the growth of bacteria. British Journal of Radiology, 56, 809-815. GINAI, A. Z., 1985. Experimental evaluation of various available contrast agents for use in the gastro-intestinal tract in case of suspected leakage. Effect on peritoneum. British Journal of Radiology, 58, 969-978. LENNETTE, E. H., BALOWS, A., HAUSLER, W. J. & SHADOMY, H.
J., 1985. Manual of Clinical Microbiology, 4th edn (American Society for Microbiology, Washington, USA). RATCLIFFE, J. F., 1986. The use of low osmolality water soluble (LOWS) contrast media in the paediatric gastrointestinal tract. A report of 115 cases. Paediatric Radiology, 16, 47-52.
The British Journal of Radiology, July 1990
Bacterial contamination of contrast media stored after opening By *D. Lisle, M B , BS, * t J . F. Ratcliffe, FRCS, FRCR, t J . Faoagali, FRCPA and t S . Cherian, M B , BS 'Department of Radiology, Royal Children's Hospital, Brisbane, tDepartment of Radiology, University of Queensland and tDepartment of Microbiology, Royal Brisbane Hospital, Queensland, Australia {Received September 1989 and in revised form January 1990)
Abstract. A barium suspension, iohexol, iopamidol and ioxaglate which were diluted with tapwater and 0.9% NaCl and dextrose saline (4% and 0.18%) were made into aliquots of 10 ml and stored at 4°C, room temperature and 37°C for 8 weeks. Regular handling and bacterial cultures were performed. These studies confirmed that environmental organisms do contaminate these solutions and that they also support viable organisms, but do not become significantly colonized at room temperature or 4°C. The solutions should be stored at room temperature or at 4°C. The diluted barium solution was the contrast medium least contaminated and if it is not contra-indicated for other reasons should be used in preference to low osmolality water soluble contrast media on the basis of its cost, radiological contrast and low microbial contamination rate.
Low osmolality water soluble (LOWS) contrast media have been shown to be suitable for gastro-intestinal studies in animals (Ginai, 1985), adults (Bell et al, 1987) and children and infants (Ratcliffe, 1986; Cohen, 1987). The expense of LOWS media prohibits their general use in gastro-intestinal radiology but there are certain clinical conditions in which their use is desirable. One practical way of reducing the cost of LOWS media for this purpose is to use medium left over from other investigations. The patient in whom it is necessary to use LOWS media in the gastro-intestinal tract may be at risk if contrast medium which is seriously contaminated with bacteria is used. This paper reports an experiment to identify the organisms which contaminate opened contrast media bottles which were stored and handled in a non-sterile manner to determine whether significant colonization occurs. Materials and methods
Three LOWS contrast media, one barium suspension and two solutions for intravenous infusion were tested. They were iohexol (Omnipaque 300, Sterling Pharmaceuticals), iopamirlol (Iopamiro 300, Schering Ltd), ioxaglate (Hexabrix 32, May and Baker), a barium suspension (Tixobar, Astra Pharmaceuticals), normal saline (0.9% NaCl, Travenol) and dextrose saline (4% dextrose and 0.18% NaCl, Travenol). Testing was performed at three different temperatures in the departmental refrigerator (0-4°C), at room temperature (15-22°C) and in the departmental contrast medium wanning oven (37°C) over a period of 8 weeks. The contrast media were diluted to concentrations commonly used in paediatric radiology using tapwater as set out in Table I to a volume of 300 ml for each test Address to Dr J. Ratcliffe, Department of Radiology, Royal Children's Hospital, Brisbane, Queensland, 4029, Australia. 532
liquid. Thirty millilitres of each liquid were separated into three 10 ml aliquots (one aliquot in each temperature environment) and put into sealed sterile containers which remained unopened for the 8 weeks. A further 30 ml of each liquid were divided into 10 ml aliquots and placed in sterile containers and sent immediately to the laboratory. The remaining 240 ml of each test liquid were divided into three 80 ml aliquots and placed in clean unused standard pharmacy bottles made of clear glass with plastic screw tops and each stored in the three temperature environments for 8 weeks. Every 7 days each of the 18 bottles was shaken, inspected and opened and 10 ml of the test liquid were removed with a syringe and aspirating cannula unique for each liquid and placed in a sterile container and sent to the laboratory. All the manipulations were done by one of the group (D.L.) and, in order to mimic the practice in radiology departments, no anti-bacterial precautions were taken. Hands were not washed and no mask was worn. The syringes and aspirating cannulae were stored in a clean and non-sterile area.
Table I. Solutions under study 4% Dextrose+ 0.18% NaCl 0.9% NaCl 75 ml of Tixobar 100% w/v 150 ml of Iohexol 300 mg I/ml 150 ml of Iopamidol 300 mg I/ml 150 ml of Hexabrix 300 mg/ul
Undiluted 300 ml Undiluted 300 ml + 225 ml of tapwater = 300 ml +150 ml of tapwater = 300 ml + 150 ml of tapwater = 300 ml + 150 ml of tapwater = 300 ml
The British Journal of Radiology, July 1990
Bacterial contamination of contrast media
All the samples sent to the laboratory were labelled in a code known only to the operator (D.L.). In the laboratory each 10 ml aliquot was inspected and mixed with 10 ml of tryptone soy broth and incubated at 35°C for 3 weeks. Direct plating of samples on receipt in the laboratory was not performed because all the solutions were crystal clear and there was insufficient sample to direct plate filter and culture in broth. The samples were inspected daily and if they became cloudy a gram stain was performed on the cloudy sample which was subcultured onto blood agar (5% horse blood) and MacConkey agar which were incubated at 35°C in air for 48 h and examined for bacterial growth. All organisms were identified using standard methods (Lennette et al, 1985) including the A.P.I. system (Vercieu, France). Results
Only the barium suspension became cloudy on shaking. No cloudiness or other abnormality was observed with the naked eye in any of the solutions during the course of the experiment. Fourteen different organisms were cultured from the samples submitted to the laboratory. One-third (5/18) of the samples mixed in an unsterile manner but then sealed for 8 weeks contained organisms, whereas twothirds of the samples in bottles opened weekly (84/144) were contaminated.
The distribution of infecting organisms is shown in Table II. The most frequently found organism was Bacillus species (mainly B. cereus). Micrococci were
found in the liquids kept at 4°C in the refrigerator. Overall contamination rates were similar in all three temperature environments. The same organism is found more frequently in samples of different liquids taken on the same day than in samples taken from the same liquid over several weeks. This form of transmission indicates that inoculation is likely to occur during handling, rather than persisting because of colonization of the bulk of the contrast medium. The exception may be micrococci in iohexol at 37°C. Discussion
Previous studies on the effect of contrast media on bacteria have been designed because of the fear that contrast media injected into or excreted into body cavities might interfere with the later microbiological diagnosis and identification of infection. Results are difficult to interpret, but in one study it was shown that conventional high osmolality contrast media tend to be antibacterial, whereas LOWS media tend to be less so (Dawson et al, 1983). The purpose of this study was to observe which bacteria contaminate or colonize contrast media in an X-ray department if the contrast media are handled in a non-sterile manner. The need for this study was gener-
Table II. The distribution of organisms cultured from 144 samples at weekly intervals at three different temperatures Week Cold 4% Dextrose 0.9% Saline Tixobar Iohexol Iopamidol Ioxaglate Room temperature 4% Dextrose 0.9% Saline Tixobar Iohexol Iopamidol Ioxaglate 37°C 4% Dextrose 0.9% Saline Tixobar Iohexol Iopamidol Ioxaglate
1
2
3
4
5
6
B P B
B P S/P P
B S
S B A B
R
R
A
2 B
B P B
S D S 4 C B
B M 5
D B
B
B
M/S B
M B
P P P
P P
P
3 A S
M B A B B
B B S B B
M P B
s
M
B S B
8
R
1 B B B B
7
M/D M B
M/C M R
R M
M
M 6
B
M B
B
B = Bacillus species (34); P = Pseudomonas stuzeri (12); S = Staphylococci epidermidis (10); M = Micrococcus species (14); R = Propionibacteria species (5); D = Diptheroid (3); A = Pseudomonas acidovorans (4); C = Acinetobacter calcoaceticus species (2); 1 = Flavobacteria species (1); 2 = Streptococci acremoris (1); 3 = Pasturella species (1); 4 = Pseudomonas species (1); 5 = Aerobic gram positive rods; 6 = Staphylococci aureus (1). Vol. 63, No. 751
533
D. Lisle, J. F. Ratcliffe, J. Faoagali and S. Cherian
ated by the expensive waste of LOWS contrast media in a paediatric X-ray department where frequently only a part of an ampoule or bottle of LOWS contrast medium is used. It has been our practice in the past to use a fresh container for each new patient and to discard any residual contrast medium at the end of each investigation. In our department it is fairly common to use LOWS media for gastro-intestinal studies in babies, infants and children and in these investigations the same degree of sterility as is required for intravascular or subarachnoid use is not required. We usually use LOWS media at dilutions almost equivalent in osmolality to plasma and therefore used the intravenous fluids (dextrose saline and normal saline) for comparison. We also used Tixobar at a 25% strength in babies in whom it is not contra-indicated. It is not our practice to use sterilized barium suspensions. It was initially anticipated that the dextrose saline would be quickly contaminated and permanently colonized and that this would act as a control. It was also expected that the normal saline which is relatively biologically inert would be contaminated as frequently as the contrast media but would not support bacterial growth. Both these expectations proved to be false and we have no explanation for the failure to identify organisms in dextrose saline and normal saline. Dilution and manipulation of the test liquids was performed in as "normal" a non-sterile manner as possible but in order to reduce individual variability these manipulations were performed by only one author (D.L.). The results show that all contrast media are easily contaminated and can support viable organisms more easily than do either dextrose saline or normal saline. Transmission of contaminating organisms by the operator at the time of sampling seems to be more important at room temperature and in cold solutions than is persistent colonization of contrast media. Persistent colonization does not seem to occur at room tempature or at 4°C. Bacillus species were the most frequent contaminating organism at all temperatures and may have colonized ioxaglate at 37°C. Micrococci were found mainly at 37°C and may have colonized iohexol at this temperature. Tixobar in a 25% suspension supports contaminants less well than do LOWS media at all three temperatures and there was no evidence of colonization of Tixobar.
534
This suggests that careful handling—using sterile equipment and sterile water for dilution at the time of investigation and storage at room temperature or at 4°C—may be more important in reducing the incidence of contamination of LOWS media for gastro-intestinal studies than the fact that the container had been opened and its contents part used in the past. Because LOWS contrast media at 37°C may support the growth of environmental micro-organisms, it is important to store opened containers at 4°C to minimize the multiplication of contaminating micro-organisms. Conclusion 1. Opened bottles of LOWS contrast media stored in the refrigerator or at room temperature may be used for gastro-intestinal studies providing clean equipment is used on each occasion. 2. Dilute Tixobar is preferable, from a microbiological point of view, to LOWS media isosmolar to plasma, providing the gastro-intestinal tract is intact. 3. Particular care should be taken not to keep opened bottles (or damaged bottles or ampoules) of LOWS media in warming ovens, especially if these media are to be used parenterally. References BELL, MCKINSKY & MILLS, 1987. Iopamidol in the diagnosis of
suspected upper G.I. perforation. Clinical Radiology, 38, 165-168. COHEN, M. D., 1987. Choosing contrast media for the evaluation of the gastro-intestinal tract of neonates and infants. Radiology, 162, 447-456. COWAN,
S. T.
& STEELE,
K.
J.,
1975. Manual for
the
Identification of Medical Bacteria, 2nd edn (Cambridge University Press, Cambridge). DAWSON, P., BACKER, A. & HOLTON, J. M., 1983. The effect of
contrast media on the growth of bacteria. British Journal of Radiology, 56, 809-815. GINAI, A. Z., 1985. Experimental evaluation of various available contrast agents for use in the gastro-intestinal tract in case of suspected leakage. Effect on peritoneum. British Journal of Radiology, 58, 969-978. LENNETTE, E. H., BALOWS, A., HAUSLER, W. J. & SHADOMY, H.
J., 1985. Manual of Clinical Microbiology, 4th edn (American Society for Microbiology, Washington, USA). RATCLIFFE, J. F., 1986. The use of low osmolality water soluble (LOWS) contrast media in the paediatric gastrointestinal tract. A report of 115 cases. Paediatric Radiology, 16, 47-52.
The British Journal of Radiology, July 1990
