Microbial contamination in two antimicrobial and four control brands of alginate impression material Christopher D. Rice, DDS, MA,* Mark A. Dykstra, PhD,b and Philip H. Feil, EdDC University of Missouri-Kansas City, Schools of Medicine and Dentistry, and Diagnostic Microbiology Laboratories, Research Medical Center, Kansas City, MO. Previous investigations have revealed commercial alginate impression material to be contaminated with viable microorganisms. Some manufacturers are now producing alginate materials that contain antimicrobial agents. The purpose of this study was to test and compare two antimicrobial and four control brands without antimicrobial agents of commercial dental alginate impression material for the presence of viable microorganisms. Forty-eight or 96 measured samples of each brand were taken from previously unopened containers using a sterile technique. The samples were placed on chocolate agar plates and in thioglycolate broth tubes and were incubated along with appropriate parallel controls. After incubation, colonies were enumerated, gram-stained, and identified using standard microbiologic methods. The two antimicrobial brands contained viable organisms in 12.5% of the samples incubated on agar media and also contained such organisms in from 0% to 16.7% of the samples incubated in thioglycolate media. The four control brands contained viable organisms in from 29.2% to 100% of the samples incubated on agar media and also contained these organisms in from 25% to 79.2% of the samples incubated in thioglycolate media. There was a statistically significant difference (p < 0.05) in contamination frequencies among some brands. Contamination frequencies of the top and middle portions of the containers did not differ significantly. The concentration of organisms in contaminated samples was 2.8 colony-formed units (CFUs) per gram for the antimicrobial alginates, and from 9 to 161.1 CFUs per gram for the control brands. Most organisms isolated were common environmental contaminants. It is concluded that samples from the antimicrobial brands exhibited lower overall levels of microbial contamination than did the control brands. (J PROSTHET DENT 1992;67:535-40.)
T
he increasing emphasis on infection control has created interest in the possible hazard of the clinical use of commercial irreversible hydrocolloid (alginate) impression material. Several studies1-g have addressed preventing the transmission of microorganisms via impression materials after exposure to the patient’s oral fluids. One aspect that has received little attention is the risk from contamination of dental materials during the manufacturing and packaging process. The American Dental Association and the Federal Food and Drug Administrationlo-I2 maintain contamination This work was supported by grants from Coe Laboratories, Inc., and L. D. Caulk, Inc. *Assistant Professor, Department of Oral Diagnosis, School of Dentistry. bDirector, Diagnostic Microbiology Laboratories, Research Medical Center, and Associate Clinical Professor, School of Medicine. cAssociate Professor, Department of Behavioral Sciences, School of Dentistry. 10/l/34865
THE JOURNAL OF PROSTHETIC DENTISTRY
standards on expendable dental materials. Samples of previously unopened dental materials have been found to contain viable microorganisms. Montgomery13 found 8 % of unopened endodontic gutta-percha cones to be contaminated with pathogenic organisms. A pilot study by Rice, et al.14to determine the incidence of bacterial contamination in various other expendable dental materials found four different materials that contained aerobic bacterial contamination in approximately 30% of the samples. However, the size of each specimen was not accurately measured, and testing was limited to visual assessmentof broth media with characterization of the isolates by a gram-stain procedure. Two of the contaminated materials, alginate and gingival retraction cord, were studied further by Rice et al.15and the findings confirmed the original observations. The contamination frequency of the alginate samples, but not of the retraction cord, was found to be statistically significant when compared with control results. Unfortunately, only one brand was tested and only the top layer of each container was sampled. 535
RICE,
DYKSTRA,
AND
FEIL
s 8AAYPLEI ,
100
90
40 30 20 10 0 IDENTIC
Fig.
Table I. Combined and thioglycolate)
contamination
JELTMTE
JELTI)WE*
1. Overall contamination
frequency
(both agar
COL
frequency.
COE AM.
JCLT* A.M.
A.M., Antimicrobial.
Table II. Differences between mean squares for each brand (analysis of variance) Brand
Brand
Percent contaminated
A
B
C
D
E
F
6.3
14.6
27.1
66.7
70.8
90.7
A, Caulk J&rate + AM (n = 48); B, Coe Hydrophilic + AM (n = 48); C, Coe Alginate (n = 48); D, Caulk Jeltrate Plus (n = 48); E, Caulk Jeltrate (n = 96); F, Cadco Identic (n = 96). AM, Antimicrobial.
A third studyI identified and enumerated viable bacteria in previously unopened containers of four different brands of alginate impression material, and evaluated whether contamination was limited to the superficial layers within the containers. The four brands varied widely in the percentage of contaminated samples and in the concentration and spectrum of contaminating organisms. One brand (Coe Alginate, Coe Laboratories, Chicago, Ill.) was found to have a significantly (p < 0.05) lower rate of contaminated samples than the other three brands tested. The contamination rate of samples from the top and middle layers did not vary significantly. Two manufacturers have addressed the risk of transmission of microorganisms in dental impression materials by developing alginates with antimicrobial agents. Coe Hydrophilic Gel Alginate (Coe Laboratories) contains chlorhexidine, and Caulk Jeltrate Plus Antimicrobial Alginate (L. D. Caulk Co., Milford, Del.) contains phenylalanine plus a quaternary ammonium compound. A recent studyI revealed that the Caulk product significantly inhibited growth of gram-positive rods and cocci, gram-negative cocci, and yeast, and t,o a lesser extent, gram-negative rods
536
Brand
V C R S U S B R A N D
Vs
A
A
0
B
C
D
E
B
0.0833
C
0.2291*
0.1458
0
D
0.6042*
0.5209*
0.3751*
E
0.6458*
0.5625*
0.4167*
0.1416
0
F
0.8542*
0.7709*
0.6251*
0.2500*
0.2084*
Abbreviations, *p < 0.05.
F
0
identifying
0
0
letters, and number of samples as in Table I.
on contact. Another studylK established that the Caulk product significantly reduced populations of Pseudomonas aeruginosa, Salmonella choleraesuis, and Staphylococcus aureus after water rinsing, a common infection control procedure performed after the material is used clinically. The purpose of this study was to test and compare samples from factory-sealed containers of these two antimicrobial alginates and from four control brands of commercial dental alginate impression material for the presence of viable microorganisms.
MATERIALS
AND
METHODS
Twelve sealed containers of the two antimicrobial brands and of four control brands of dental alginate impression
APRIL
1992
VOLUME
67
NUMBER
4
CONTAMINATION
IN ANTIMICROBIAL
ALGINATES
lb SAMPLES
80
80 50 40 30 20 10 0 IDENTIC
Fig.
2. Contamination
JEWRATE
Jl!LTRATE*
COE
COE
JLLT*
A.M.
A.M.
frequency in thioglycolate media. Abbreviations as in legend to
Fig. 1.
material were obtained from the manufacturers. The tested antimicrobial brands were Coe Hydrophilic Gel, fast set, wild cherry (Coe Laboratories), batch number 04129OA, and Jeltrate Plus ABV (L. D. Caulk Company), batch number 06790. The tested control brands were Jeltrate Plus, regular set (L. D. Caulk Co.), batch number 030990; Coe Alginate, regular set, wild cherry (Coe Laboratories), batch number 020190A; Cadco Identic (Cadco Dental Products, Oxnard, Calif.), batch numbers 8948,9283,9284 and 9399; and Jeltrate, regular set (L. D. Caulk Co.), batch numbers 040490-2 and 040490-3. Additional orders for 12 sealed containers of the Cadco Identic (batch number 9441) and the Jeltrate, regular set (batch number 033090) were obtained to allow further comparison of different batches. The packaging and containers were examined to ensure they had not been violated in any manner. Each container was opened and four 0.06 gm samples were removed aseptically, two from the top portion and two from the middle portion. Individual chocolate agar plates were inoculated with a top and middle sample each. The remaining two samples (one top and one middle) were subjected to grinding in 3.5 mm sterile water for 10 seconds to form a slurry. The slurry was then dispensed into tubes of thioglycolate broth that were inverted once to combine the slurry with the broth medium. Twenty-four sham-inoculated chocolate agar plates and an equal number of sham-inoculated thioglycolate broths served as negative controls. Ten chocolate plates were challenged with a mixture of four isolates (Escherichia coli, American Type Culture Collection [ATCC] No. 25922; S. aureus, ATCC No. 29213; P. aeruginosa, ATCC No. 27853; and Streptococcus faecalis, ATCC No. 29212) to ensure that the media supported growth of common microorgan-
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Table
III.
Growth in thioglycolate (percent of samples) Brand Organism
Bacillus sp. Corynebacterium sp.
A
B
C
D
E
F
-
8 4
17 8
29 4 -
40 4
69 8
4
4
6
4 2
46
82
Staphylococcus,coagulase negative Propronibacterium Aspergihs sp.
acne.s
Percent contaminated*
-
-
0
17
25
33
A, Caulk J&rate + AM (n = 24); B, Coe Hydrophilic + AM (n = 24); C, Coe Alginate (n = 24); D, Caulk Jeltrate Plus (n = 24); E, Caulk Jeltrate (n = 48); F, Cadco Identic (n = 48). Abbreviations as in Table I. *Some samples had more than one contaminant.
isms. The microbial specimens were maintained for reference purposes in the laboratory of a local hospital. All plates were incubated at 37” C for 7 days and colonies were counted on plates showing growth. Isolates were gramstained and identified using standard microbiologic methods.lg The thioglycolate broth tubes were incubated at 37O C for 7 days, gram-stained, subcultured to chocolate agar plates, incubated aerobically, and blood agar plates were incubated anaerobically. Organisms that grew were identified as described above. The frequency of contaminated samples was compared across brands, media, batches, and locations of samples using separate one-way analyses of variance or t tests, depending on the appropriateness of the test. Post hoc com-
537
RICE,
DYKSTRA.
AND
FEIL
lOO-SO807060-
.’
so 40 3020loo
T IDEWTIC
JELlRATE
JEWRATE*
COL
JILT*
A.Y.
CM
AM.
l Yl)C..NNOD 0.05) difference between samples from the top and middle portions of their containers. There was no significant difference (p > 0.05) in the results of different batches from the same manufacturer, and the data for each brand were considered as a unit. The overall average contamination frequency (both top and middle samples, both thioglycolates and agar media) of Jeltrate Plus Antimicrobial was 6.3 % , and for Coe Hydrophilic Gel the average contamination frequency was 14.6% . The control alginate values were Coe Alginate at 27.1%, followed by Caulk Jeltrate Plus at 66.7%) Caulk Jeltrate at 70.8 %, and Van R/Cadco Identic at 90.7%. These results are summarized in Table I and Fig. 1. The two antimicrobial brands exhibited a significantly (p < 0.05) lower overall contamination frequency than three of the four control brands, the exception being Coe Alginate. The Caulk Jeltrate Plus antimicrobial brand was significantly (p < 0.05) less contaminated than the Coe Alginate control brand; however, the Coe Hydrophilic Gel was not significantly less contaminated. The Coe Alginate control was significantly (p < 0.05) less contaminated than the other three control brands. These results are summarized in Table II. The spectrum of various types of organisms isolated in the thioglycolate broths and chocolate agar plates is illustrated in Tables III and IV and in Figs. 2 and 3, respectively. The concentration of organisms isolated in each contaminated sample on the chocolate agar plates is summarized in Table V and Fig. 4. Some samples yielded con-
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1992
VOLUME
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NUMBER
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CONTAMINATION
IN ANTIMICROBIAL
ALGINATES
C.F.U.r/QRAM
OF OONTAMINATED
8AMPLE
JELTRATE
JELlRATE*
160 & 50-. 40 -.
30-
20 -.
lo-o-
J
I IDENflC
COE
L JtLT*
A.M.
J COE
A.M.
‘YI8C.*RHODOCOCCUI),IRAnnAUELLA,ENT~~O~
Fig. 4. Concentration of organisms in agar media. C.F.U.s, Colony-forming units; other abbreviations as in legend to Fig. 1.
fluent growth of Bacillus sp. and the exact number of colony-forming units (CFUs) could not be accurately assessed; however, it was determined that a minimum of 10 colonies had to be present for this appearance. The two antimicrobial alginates showed the lowest concentration at 2.8 CFUs/gm of contaminated sample each. The control alginates’ concentrations included Coe alginate at 9.0 CFUs/ gm, Caulk Jeltrate Plus at 41.7 CFUs/gm, Caulk Jeltrate at 50.7 CFUs/gm, and Cadco Identic at 161.7 CFUs/gm of contaminated sample. DISCUSSION The chocolate agar media showed an average contamination frequency of alginate samples approximately twice as often as did the thioglycolate broths. This may be due to a failure to disperse the alginate sample in the thioglycolate broths, despite grinding of the samples. The spectrum of contaminants in the agar plates featured mostly low virulence organisms. Bacillus sp., the most common contaminant, are of low virulence and are commonly found as environmental contaminants. Staphy2ococcus sp. (coagulase-negative), aerobic Actinomyces, Aspergillus sp., Sarcina, Rhodococcus, and Corynebacterium sp., are relatively low in virulence. Moraxella (Branhamella) catarrhalis, Pantoea (Enterobacter) agglomerans, and Staphylococcus aureus, and Staphylococcus aureus, all moderately virulent organisms, were also isolated.
The organisms identified in the thioglycolate broths included Bacillus sp., coagulase negative Staphylococcus sp., Corynebacterium sp., and Aspergillus sp., all discussed previously. Propionibacterium acnes is an anaerobic skin commensal of low virulence.
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Table V. Agar contamination concentration (number of colony-forming units/per gram of contaminated sample) Brand Organism
Bacillus sp. Staphylococcus, coagulase
ABCD 1.4 -
-
2.8
29.9
3.5
6.9
-
0.7 1.4
1.4 2.1
2.8
-
-
0.7
--
-
0.7
E
F
45.5 2.1
160.4 0.7
negative Corynebacterium sp. Aerobic Actinomyces Aspergillus sp. Sarcina
0.7
Moranella catarrhalis Rhodococcus Enterobacter agglomerans Staphylococcus aureus
---_ ----
Total CFUs/gm
2.8
0.7
-
0.7
0.7 1.4 0.3
0.3 0.3
2.8
9.0
41.7
50.7
161.1
A, CaulkJeltrate + AM (n = 24); B, Coe Hydrophilic + AM (n = 24); C, Coe Alginate (n = 24); D, Caulk Jeltrate Plus (n = 24); E, Caulk J&rate (n = 48); F, Cadco Identic (n = 48). CFU, Colony-forming units; other abbreviations as in Table I.
CLINICAL
SIGNIFICANCE
With increasing frequency, it is necessary to perform dental procedures on immunocompromised patients. McGhee et aL2” cautioned that the compromised patient may have an altered flora and be susceptible to infection with less usual organisms, and ordinary dental procedures may result in septicemias that are potentially fatal. The patient becomes more susceptible to infections from microbes of lower virulence as the immune response becomes 539
RICE,
progressively less efficient. Thus microorganisms that are avirulent could become pathogenic in severely immunocompromised hosts. Many of the organisms isolated in this study are avirulent members of environmental flora, or avirulent members of normal skin flora. However, the potential may still exist for the initiation of infectious disease through the routine use of contaminated dental materials in debilitated or immunocompromised patients.
SUMMARY Samples of two brands containing antimicrobial agents and of four control brands of commercially available alginate impression powder were incubated in two different media. The resulting colonies were identified by standard methods, and the results were statistically analyzed. Antimicrobial alginates had a significantly (p < 0.05) lower overall frequency of contamination when compared with three of the control brands. Brands varied appreciably in the spectrum and concentration of contaminants; however, contamination frequencies did not vary significantly between the top and middle layers of the containers, or between different batches of the same brand. Most organisms were found to be common environmental contaminants that may represent a hazard only to immunocompromised patients. We thank J. David Eick, PhD, Charles M. Cobb, DDS, PhD, and Dawn Lumpkin, BS, MT (ASCP), SM, for their assistance on this project.
REFERENCES 1. Leung RL, Schonfeld SE. Gypsum casts as a potential source of microbial cross-contamination. J PROSTHET DENT 1983;49:210-1. 2. Williams N, Falkler W Jr, Jasler J, Romberg E. The persistence of contaminant bacteria in dental laboratory pumice [Abstract]. J Dent Res 1985;64:258. 3. Powell GL, Runnells RD, Saxon BA, Whisenant BK. The presence and identification of organisms transmitted to dental laboratories. J PROSTHET DENT
1990;64:235-7.
4. Council on Dental Materials, Instruments and Equipment. Infection control recommendations for the dental office and the dental laboratory. J Am Dent Assoc 1988;116:241-8.
540
DYKSTRA,
AND
FEIL
5. Setcos JC, Gerstenblatt R, Palenik CJ, Hinoura K. Disinfection of a polyether dental impression material [Abstract]. J Dent Res 1985;64:244. 6. Toh CG, et al. Intluences of disinfectants on a vinyl polysiloxane impression material [Abstract]. J Dent Res 1987;66:133. 7. Setcos JC, Chang M, Palenik CJ, Blumershine R. The effects of disinfectants on a poysuifide impression material [Abstract]. J Dent Res 1986;65:260. 8. Herrera SP, Merchant VA. Dimensional stability of dental impressions after immersion disinfection. J Am Dent Assoc 1986,113:419-22. 9. Puersfeldt A, Asmussen E. Effect of disinfecting solutions on accuracy of alginate and elastomeric impressions. Stand J Dent Res 1989;97:470-5. 10. United States Food and Drug Administration. Manufacture, packing, storage and installation of medical devices: Regulations establishing good manufacturing practices. Fed Register 1978;43:141. 11. Council adopts American Dental Association specification No. 18 (alginate impression material). American Dental Association Council on Dental Materials and Devices. J Am Dent Assoc 1968;77:1354-8. 12. Document No. 41 for Recommended standard practices for the biological evaluation of dental materials. Council on Dental Materials, Instruments, and Equipment, American Dental Association. American National Standard/American Dental Association Document No. 41. 1982. 13. Montgomery S. Chemical decontamination of gutta-percha cones with polyvinylpyrrolidone-iodine. Oral Surg 1971;31:258-66. 14. Rice CD, Moghadam B, Gier RE, Cobb CM. Aerobic bacterial contamination in dental materials. Oral Surg Oral Med Oral Pathol 1990;70:537-9. 15. Rice CD, Dykstra MA, Gier RE. Bacterial contamination in irreversible hydrocolloid impression material and gingival retraction cord. J PROSTHET DENT
1991;65:496-9.
16. Rice CD, Dykstra MA, Gier RE, Cobb CM. Microbial contamination in four brands of commercial alginate impression material. J PROSTHET DENT
1991;65:419-23.
17. Palenik CJ, Setcos JC, Miller CH, Sheldrake MA. Antimicrobial activity of a disinfectant-containing alginate impression material [Abstract]. J Dent Res 1990;69:348. 18. Jefferies S, Bennet R, Stambaugh K. Effectiveness of antimicrobial containing alginate in reducing surface bacteria [Abstract] J Dent Res 1990;69:348. 19. A.S.M. Manual of clinical microbiology. 4th ed. Washington, DC: A.S.M. Press, 1987. 20. McGhee JR, Michalek SM, Cassell GH, eds. Dental Microbiology. New York: Harper and Row, 1982. Reprint
requests to:
CHRISTOPHER D. RICE, DDS, MA UNIVERSITY OF MISSOURI-KANSAS SCHOOL OF DENTISTRY 650 EAST 25~~ STREET KANSAS CITY. MO 64108
CITV
APRIL
1992
VOLUME
67
NUMBER
4
T
he increasing emphasis on infection control has created interest in the possible hazard of the clinical use of commercial irreversible hydrocolloid (alginate) impression material. Several studies1-g have addressed preventing the transmission of microorganisms via impression materials after exposure to the patient’s oral fluids. One aspect that has received little attention is the risk from contamination of dental materials during the manufacturing and packaging process. The American Dental Association and the Federal Food and Drug Administrationlo-I2 maintain contamination This work was supported by grants from Coe Laboratories, Inc., and L. D. Caulk, Inc. *Assistant Professor, Department of Oral Diagnosis, School of Dentistry. bDirector, Diagnostic Microbiology Laboratories, Research Medical Center, and Associate Clinical Professor, School of Medicine. cAssociate Professor, Department of Behavioral Sciences, School of Dentistry. 10/l/34865
THE JOURNAL OF PROSTHETIC DENTISTRY
standards on expendable dental materials. Samples of previously unopened dental materials have been found to contain viable microorganisms. Montgomery13 found 8 % of unopened endodontic gutta-percha cones to be contaminated with pathogenic organisms. A pilot study by Rice, et al.14to determine the incidence of bacterial contamination in various other expendable dental materials found four different materials that contained aerobic bacterial contamination in approximately 30% of the samples. However, the size of each specimen was not accurately measured, and testing was limited to visual assessmentof broth media with characterization of the isolates by a gram-stain procedure. Two of the contaminated materials, alginate and gingival retraction cord, were studied further by Rice et al.15and the findings confirmed the original observations. The contamination frequency of the alginate samples, but not of the retraction cord, was found to be statistically significant when compared with control results. Unfortunately, only one brand was tested and only the top layer of each container was sampled. 535
RICE,
DYKSTRA,
AND
FEIL
s 8AAYPLEI ,
100
90
40 30 20 10 0 IDENTIC
Fig.
Table I. Combined and thioglycolate)
contamination
JELTMTE
JELTI)WE*
1. Overall contamination
frequency
(both agar
COL
frequency.
COE AM.
JCLT* A.M.
A.M., Antimicrobial.
Table II. Differences between mean squares for each brand (analysis of variance) Brand
Brand
Percent contaminated
A
B
C
D
E
F
6.3
14.6
27.1
66.7
70.8
90.7
A, Caulk J&rate + AM (n = 48); B, Coe Hydrophilic + AM (n = 48); C, Coe Alginate (n = 48); D, Caulk Jeltrate Plus (n = 48); E, Caulk Jeltrate (n = 96); F, Cadco Identic (n = 96). AM, Antimicrobial.
A third studyI identified and enumerated viable bacteria in previously unopened containers of four different brands of alginate impression material, and evaluated whether contamination was limited to the superficial layers within the containers. The four brands varied widely in the percentage of contaminated samples and in the concentration and spectrum of contaminating organisms. One brand (Coe Alginate, Coe Laboratories, Chicago, Ill.) was found to have a significantly (p < 0.05) lower rate of contaminated samples than the other three brands tested. The contamination rate of samples from the top and middle layers did not vary significantly. Two manufacturers have addressed the risk of transmission of microorganisms in dental impression materials by developing alginates with antimicrobial agents. Coe Hydrophilic Gel Alginate (Coe Laboratories) contains chlorhexidine, and Caulk Jeltrate Plus Antimicrobial Alginate (L. D. Caulk Co., Milford, Del.) contains phenylalanine plus a quaternary ammonium compound. A recent studyI revealed that the Caulk product significantly inhibited growth of gram-positive rods and cocci, gram-negative cocci, and yeast, and t,o a lesser extent, gram-negative rods
536
Brand
V C R S U S B R A N D
Vs
A
A
0
B
C
D
E
B
0.0833
C
0.2291*
0.1458
0
D
0.6042*
0.5209*
0.3751*
E
0.6458*
0.5625*
0.4167*
0.1416
0
F
0.8542*
0.7709*
0.6251*
0.2500*
0.2084*
Abbreviations, *p < 0.05.
F
0
identifying
0
0
letters, and number of samples as in Table I.
on contact. Another studylK established that the Caulk product significantly reduced populations of Pseudomonas aeruginosa, Salmonella choleraesuis, and Staphylococcus aureus after water rinsing, a common infection control procedure performed after the material is used clinically. The purpose of this study was to test and compare samples from factory-sealed containers of these two antimicrobial alginates and from four control brands of commercial dental alginate impression material for the presence of viable microorganisms.
MATERIALS
AND
METHODS
Twelve sealed containers of the two antimicrobial brands and of four control brands of dental alginate impression
APRIL
1992
VOLUME
67
NUMBER
4
CONTAMINATION
IN ANTIMICROBIAL
ALGINATES
lb SAMPLES
80
80 50 40 30 20 10 0 IDENTIC
Fig.
2. Contamination
JEWRATE
Jl!LTRATE*
COE
COE
JLLT*
A.M.
A.M.
frequency in thioglycolate media. Abbreviations as in legend to
Fig. 1.
material were obtained from the manufacturers. The tested antimicrobial brands were Coe Hydrophilic Gel, fast set, wild cherry (Coe Laboratories), batch number 04129OA, and Jeltrate Plus ABV (L. D. Caulk Company), batch number 06790. The tested control brands were Jeltrate Plus, regular set (L. D. Caulk Co.), batch number 030990; Coe Alginate, regular set, wild cherry (Coe Laboratories), batch number 020190A; Cadco Identic (Cadco Dental Products, Oxnard, Calif.), batch numbers 8948,9283,9284 and 9399; and Jeltrate, regular set (L. D. Caulk Co.), batch numbers 040490-2 and 040490-3. Additional orders for 12 sealed containers of the Cadco Identic (batch number 9441) and the Jeltrate, regular set (batch number 033090) were obtained to allow further comparison of different batches. The packaging and containers were examined to ensure they had not been violated in any manner. Each container was opened and four 0.06 gm samples were removed aseptically, two from the top portion and two from the middle portion. Individual chocolate agar plates were inoculated with a top and middle sample each. The remaining two samples (one top and one middle) were subjected to grinding in 3.5 mm sterile water for 10 seconds to form a slurry. The slurry was then dispensed into tubes of thioglycolate broth that were inverted once to combine the slurry with the broth medium. Twenty-four sham-inoculated chocolate agar plates and an equal number of sham-inoculated thioglycolate broths served as negative controls. Ten chocolate plates were challenged with a mixture of four isolates (Escherichia coli, American Type Culture Collection [ATCC] No. 25922; S. aureus, ATCC No. 29213; P. aeruginosa, ATCC No. 27853; and Streptococcus faecalis, ATCC No. 29212) to ensure that the media supported growth of common microorgan-
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Table
III.
Growth in thioglycolate (percent of samples) Brand Organism
Bacillus sp. Corynebacterium sp.
A
B
C
D
E
F
-
8 4
17 8
29 4 -
40 4
69 8
4
4
6
4 2
46
82
Staphylococcus,coagulase negative Propronibacterium Aspergihs sp.
acne.s
Percent contaminated*
-
-
0
17
25
33
A, Caulk J&rate + AM (n = 24); B, Coe Hydrophilic + AM (n = 24); C, Coe Alginate (n = 24); D, Caulk Jeltrate Plus (n = 24); E, Caulk Jeltrate (n = 48); F, Cadco Identic (n = 48). Abbreviations as in Table I. *Some samples had more than one contaminant.
isms. The microbial specimens were maintained for reference purposes in the laboratory of a local hospital. All plates were incubated at 37” C for 7 days and colonies were counted on plates showing growth. Isolates were gramstained and identified using standard microbiologic methods.lg The thioglycolate broth tubes were incubated at 37O C for 7 days, gram-stained, subcultured to chocolate agar plates, incubated aerobically, and blood agar plates were incubated anaerobically. Organisms that grew were identified as described above. The frequency of contaminated samples was compared across brands, media, batches, and locations of samples using separate one-way analyses of variance or t tests, depending on the appropriateness of the test. Post hoc com-
537
RICE,
DYKSTRA.
AND
FEIL
lOO-SO807060-
.’
so 40 3020loo
T IDEWTIC
JELlRATE
JEWRATE*
COL
JILT*
A.Y.
CM
AM.
l Yl)C..NNOD 0.05) difference between samples from the top and middle portions of their containers. There was no significant difference (p > 0.05) in the results of different batches from the same manufacturer, and the data for each brand were considered as a unit. The overall average contamination frequency (both top and middle samples, both thioglycolates and agar media) of Jeltrate Plus Antimicrobial was 6.3 % , and for Coe Hydrophilic Gel the average contamination frequency was 14.6% . The control alginate values were Coe Alginate at 27.1%, followed by Caulk Jeltrate Plus at 66.7%) Caulk Jeltrate at 70.8 %, and Van R/Cadco Identic at 90.7%. These results are summarized in Table I and Fig. 1. The two antimicrobial brands exhibited a significantly (p < 0.05) lower overall contamination frequency than three of the four control brands, the exception being Coe Alginate. The Caulk Jeltrate Plus antimicrobial brand was significantly (p < 0.05) less contaminated than the Coe Alginate control brand; however, the Coe Hydrophilic Gel was not significantly less contaminated. The Coe Alginate control was significantly (p < 0.05) less contaminated than the other three control brands. These results are summarized in Table II. The spectrum of various types of organisms isolated in the thioglycolate broths and chocolate agar plates is illustrated in Tables III and IV and in Figs. 2 and 3, respectively. The concentration of organisms isolated in each contaminated sample on the chocolate agar plates is summarized in Table V and Fig. 4. Some samples yielded con-
APRIL
1992
VOLUME
67
NUMBER
4
CONTAMINATION
IN ANTIMICROBIAL
ALGINATES
C.F.U.r/QRAM
OF OONTAMINATED
8AMPLE
JELTRATE
JELlRATE*
160 & 50-. 40 -.
30-
20 -.
lo-o-
J
I IDENflC
COE
L JtLT*
A.M.
J COE
A.M.
‘YI8C.*RHODOCOCCUI),IRAnnAUELLA,ENT~~O~
Fig. 4. Concentration of organisms in agar media. C.F.U.s, Colony-forming units; other abbreviations as in legend to Fig. 1.
fluent growth of Bacillus sp. and the exact number of colony-forming units (CFUs) could not be accurately assessed; however, it was determined that a minimum of 10 colonies had to be present for this appearance. The two antimicrobial alginates showed the lowest concentration at 2.8 CFUs/gm of contaminated sample each. The control alginates’ concentrations included Coe alginate at 9.0 CFUs/ gm, Caulk Jeltrate Plus at 41.7 CFUs/gm, Caulk Jeltrate at 50.7 CFUs/gm, and Cadco Identic at 161.7 CFUs/gm of contaminated sample. DISCUSSION The chocolate agar media showed an average contamination frequency of alginate samples approximately twice as often as did the thioglycolate broths. This may be due to a failure to disperse the alginate sample in the thioglycolate broths, despite grinding of the samples. The spectrum of contaminants in the agar plates featured mostly low virulence organisms. Bacillus sp., the most common contaminant, are of low virulence and are commonly found as environmental contaminants. Staphy2ococcus sp. (coagulase-negative), aerobic Actinomyces, Aspergillus sp., Sarcina, Rhodococcus, and Corynebacterium sp., are relatively low in virulence. Moraxella (Branhamella) catarrhalis, Pantoea (Enterobacter) agglomerans, and Staphylococcus aureus, and Staphylococcus aureus, all moderately virulent organisms, were also isolated.
The organisms identified in the thioglycolate broths included Bacillus sp., coagulase negative Staphylococcus sp., Corynebacterium sp., and Aspergillus sp., all discussed previously. Propionibacterium acnes is an anaerobic skin commensal of low virulence.
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Table V. Agar contamination concentration (number of colony-forming units/per gram of contaminated sample) Brand Organism
Bacillus sp. Staphylococcus, coagulase
ABCD 1.4 -
-
2.8
29.9
3.5
6.9
-
0.7 1.4
1.4 2.1
2.8
-
-
0.7
--
-
0.7
E
F
45.5 2.1
160.4 0.7
negative Corynebacterium sp. Aerobic Actinomyces Aspergillus sp. Sarcina
0.7
Moranella catarrhalis Rhodococcus Enterobacter agglomerans Staphylococcus aureus
---_ ----
Total CFUs/gm
2.8
0.7
-
0.7
0.7 1.4 0.3
0.3 0.3
2.8
9.0
41.7
50.7
161.1
A, CaulkJeltrate + AM (n = 24); B, Coe Hydrophilic + AM (n = 24); C, Coe Alginate (n = 24); D, Caulk Jeltrate Plus (n = 24); E, Caulk J&rate (n = 48); F, Cadco Identic (n = 48). CFU, Colony-forming units; other abbreviations as in Table I.
CLINICAL
SIGNIFICANCE
With increasing frequency, it is necessary to perform dental procedures on immunocompromised patients. McGhee et aL2” cautioned that the compromised patient may have an altered flora and be susceptible to infection with less usual organisms, and ordinary dental procedures may result in septicemias that are potentially fatal. The patient becomes more susceptible to infections from microbes of lower virulence as the immune response becomes 539
RICE,
progressively less efficient. Thus microorganisms that are avirulent could become pathogenic in severely immunocompromised hosts. Many of the organisms isolated in this study are avirulent members of environmental flora, or avirulent members of normal skin flora. However, the potential may still exist for the initiation of infectious disease through the routine use of contaminated dental materials in debilitated or immunocompromised patients.
SUMMARY Samples of two brands containing antimicrobial agents and of four control brands of commercially available alginate impression powder were incubated in two different media. The resulting colonies were identified by standard methods, and the results were statistically analyzed. Antimicrobial alginates had a significantly (p < 0.05) lower overall frequency of contamination when compared with three of the control brands. Brands varied appreciably in the spectrum and concentration of contaminants; however, contamination frequencies did not vary significantly between the top and middle layers of the containers, or between different batches of the same brand. Most organisms were found to be common environmental contaminants that may represent a hazard only to immunocompromised patients. We thank J. David Eick, PhD, Charles M. Cobb, DDS, PhD, and Dawn Lumpkin, BS, MT (ASCP), SM, for their assistance on this project.
REFERENCES 1. Leung RL, Schonfeld SE. Gypsum casts as a potential source of microbial cross-contamination. J PROSTHET DENT 1983;49:210-1. 2. Williams N, Falkler W Jr, Jasler J, Romberg E. The persistence of contaminant bacteria in dental laboratory pumice [Abstract]. J Dent Res 1985;64:258. 3. Powell GL, Runnells RD, Saxon BA, Whisenant BK. The presence and identification of organisms transmitted to dental laboratories. J PROSTHET DENT
1990;64:235-7.
4. Council on Dental Materials, Instruments and Equipment. Infection control recommendations for the dental office and the dental laboratory. J Am Dent Assoc 1988;116:241-8.
540
DYKSTRA,
AND
FEIL
5. Setcos JC, Gerstenblatt R, Palenik CJ, Hinoura K. Disinfection of a polyether dental impression material [Abstract]. J Dent Res 1985;64:244. 6. Toh CG, et al. Intluences of disinfectants on a vinyl polysiloxane impression material [Abstract]. J Dent Res 1987;66:133. 7. Setcos JC, Chang M, Palenik CJ, Blumershine R. The effects of disinfectants on a poysuifide impression material [Abstract]. J Dent Res 1986;65:260. 8. Herrera SP, Merchant VA. Dimensional stability of dental impressions after immersion disinfection. J Am Dent Assoc 1986,113:419-22. 9. Puersfeldt A, Asmussen E. Effect of disinfecting solutions on accuracy of alginate and elastomeric impressions. Stand J Dent Res 1989;97:470-5. 10. United States Food and Drug Administration. Manufacture, packing, storage and installation of medical devices: Regulations establishing good manufacturing practices. Fed Register 1978;43:141. 11. Council adopts American Dental Association specification No. 18 (alginate impression material). American Dental Association Council on Dental Materials and Devices. J Am Dent Assoc 1968;77:1354-8. 12. Document No. 41 for Recommended standard practices for the biological evaluation of dental materials. Council on Dental Materials, Instruments, and Equipment, American Dental Association. American National Standard/American Dental Association Document No. 41. 1982. 13. Montgomery S. Chemical decontamination of gutta-percha cones with polyvinylpyrrolidone-iodine. Oral Surg 1971;31:258-66. 14. Rice CD, Moghadam B, Gier RE, Cobb CM. Aerobic bacterial contamination in dental materials. Oral Surg Oral Med Oral Pathol 1990;70:537-9. 15. Rice CD, Dykstra MA, Gier RE. Bacterial contamination in irreversible hydrocolloid impression material and gingival retraction cord. J PROSTHET DENT
1991;65:496-9.
16. Rice CD, Dykstra MA, Gier RE, Cobb CM. Microbial contamination in four brands of commercial alginate impression material. J PROSTHET DENT
1991;65:419-23.
17. Palenik CJ, Setcos JC, Miller CH, Sheldrake MA. Antimicrobial activity of a disinfectant-containing alginate impression material [Abstract]. J Dent Res 1990;69:348. 18. Jefferies S, Bennet R, Stambaugh K. Effectiveness of antimicrobial containing alginate in reducing surface bacteria [Abstract] J Dent Res 1990;69:348. 19. A.S.M. Manual of clinical microbiology. 4th ed. Washington, DC: A.S.M. Press, 1987. 20. McGhee JR, Michalek SM, Cassell GH, eds. Dental Microbiology. New York: Harper and Row, 1982. Reprint
requests to:
CHRISTOPHER D. RICE, DDS, MA UNIVERSITY OF MISSOURI-KANSAS SCHOOL OF DENTISTRY 650 EAST 25~~ STREET KANSAS CITY. MO 64108
CITV
APRIL
1992
VOLUME
67
NUMBER
4
