Indian Journal of Dental Research

: 2006  |  Volume : 17  |  Issue : 2  |  Page : 70--3

Microbial contamination of "In use" bar soap in dental clinics

PP Hegde1, AT Andrade2, K Bhat1,  
1 Department of Preventive and Community Dentistry, KLES Institute of Dental Sciences, Belgaum, India
2 Department of Preventive and Community Dentistry, KLES Institute of Dental Sciences, Belgaum; Department of Microbology, Hi-Tech Laboratory, Belgaum, India

Correspondence Address:
P P Hegde
Department of Preventive and Community Dentistry, KLES Institute of Dental Sciences, Belgaum


Bar soap from 18 different dental clinics were investigated for microbial contamination, while it was DQin-useDQ. Of the 32 samples obtained from the bar soap, 100% yielded positive culture. A total of 8 different genera of organisms were isolated. Each bar soap was found to harbor 2-5 different genera of micro organisms. Heavily used soap had more micro organisms compared to less used soap. The microbial load of the DQin-useDQ bar soap constituted a mixed flora of gram positive, gram negative, aerobes, anaerobes, and fungi. The results indicate that the bar soap under DQin-useDQ condition is a reservoir of microorganisms and handwashing with such a soap may lead to spread of infection.

How to cite this article:
Hegde P P, Andrade A T, Bhat K. Microbial contamination of "In use" bar soap in dental clinics.Indian J Dent Res 2006;17:70-3

How to cite this URL:
Hegde P P, Andrade A T, Bhat K. Microbial contamination of "In use" bar soap in dental clinics. Indian J Dent Res [serial online] 2006 [cited 2020 Nov 27 ];17:70-3
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In the profession of 'dentistry', we work in close proximity with the oral cavity, which is a gateway for the entry of many substances, not excluding the microorganisms. Thereby it becomes the prime duty of the dentist to prevent cross-contamination, which implies patient as well as personal safety. Widely endorsed as a part of "Universal Precaution", handwashing for a dentist is 'sine qua non'. From times immemorial, soap has been widely used as an adjunct for handwashing. It has been observed, that the bar soaps have been routinely used for handwashing by the dentist in their clinics. Literature review [1],[2],[3]reveals reports of isolation of microorganisms from the "in-use" soap bars. This raises the concern that the bar soap used in the warfare against microbes becomes a harbor of microorganisms, which may ultimately result in infection outbreaks. Since there are a few studies [1],[2],[3] addressing this question that have been published, this study was undertaken to test this concern. The purpose of this study was to investigate whether the soap bar under "in-use" condition was contaminated with microorganisms and if so, to isolate the different types of microorganisms.


Test Site : The soap survey was carried out in 18 different dental clinics in Belgaum.

Test Soap : To begin with, fresh soap bars (popular brand of medicated soap) commonly used by the dentists, purchased from the supermarket were placed at the dental clinic bandwashing stations. This bar soap was intended to be used by the dentist and the other auxiliaries in the clinic. None of them were aware of the aim of the study. This was done to eliminate any kind of bias that could have influenced the results.

The soap sample was taken on 2 occasions, the first sample from fresh (unused) soap [T(0]], and the second sample after 7 days of use [T(7)]. The soap bar was weighed before and after the 7 day period to maintain uniformity and to measure the soap use respectively. The soap samples were obtained (in duplicate) by using sterile cotton swabs moistened with phosphate buffer solution (PBS). Under sterile conditions, the moistened cotton swab was slid in a single stroke over the top portion of the soap, which was placed in the soap dish at the wash station in the dental clinic. The swab was immediately introduced into a sterile test tube containing 2m1 of PB S. At no time did the swab come in contact with the tester's fingers or the outside of the tube. Sterility control samples were taken. As additional control, vigilance was kept on the microbial count of the water supply. The test tubes were transferred to the Hi Tech Diagnostic center, Belgaum where the microbiological analysis was performed.

Laboratory Procedure : The test tubes were vigorously shaken for 30 seconds. Preliminary tests were done to evaluate whether direct streaking of the swab or streaking of PB S in ocuhun would yield higher recovery of microorganism from bar soaps. The results showed that the use of direct swab method yielded high recovery of microorganisms and no negative samples, in contrast to lower yields and some negative values when the PBS inocuhun was used. Thereafter for the culturing of microorganism, direct streaking of the swab was the method of choice. One cotton swab was used to streak 2 agar plates; chocolate agar for Gram positive aerobes and facultatives, Mackonkey agar for Gram negative aerobes and facultatives and blood agar for anaerobes. These plates were incubated for 48 hours at 37sub C aerobically and anaerobically. Sabouraud's dextrose agar was used for fungi and was incubated for 5 days at 37sub C. After incubation, the plates were counted for microbial colonies and expressed as colony fonning units (cfu/per bar of soap). Identification was initially based on the morphological characteristics and then on the reaction to specific biochemical test [4].


The bar soap samples were obtained from 32 hand washing stations at 18 different dental clinics. AtT(0) (fresh unused bar soap), 29 samples were found to be free of microorganisms, while only 3 samples showed the presence of Staph. epidermidis. The sterility controls for swab, PBS and culture plates. At T(7) (sample after 7 days of use), 100%(n=32) yielded positive culture. The data of the microbial isolates is collectively represented in [Table 1]. The microbial load of the "in use" bar soap constituted a mixed variety of gram positive, gram negative, aerobes, anaerobes and fungi. The total microbial population obtained from bar soap represented 8 different genera. The soaps were found to harbor 2 to 5 different genera of microorganisms per bar. Maximum number of bar soaps, 21(65.62%) had harbored 4 different genera of microorganisms, while 7(21.87%) samples showed 5 genera of microorganisms and 4(12.5%) samples showed 2 genera of microorganisms. [Table 1], also summarizes the frequency of isolation of the microorganisms from 32 samples. Staph.epidermidis was a common feature in all the samples, while pathogenic Staphaureus was found in 6 samples. E coli and Klebsiella had a major share of occurrence, i.e25 of 32 and 28 of 32 samples respectively. Table 2 compares the microbial isolates of the present study with two other previous studies [1],[2].


A self-designed protocol was used to investigate the microbial contamination of the bar soap under "In use" condition in the dental clinic set up. The results showed that all (100%) the bar soaps under "in use" condition yielded positive culture, indicating that "in use" bar soaps were depots of microorganisms. This result is in accordance with other similar study reports [1],[2],[3].

In the study by Kabara IT and Brady MB [1],who investigated bar and liquid soaps from 26 public lavatories for microbial colonies, of the 84 samples from the bar soap, 100% yielded positive culture and the microbial population obtained from the bar soap represented over 16 different genera [Table 2]. In the study conducted by McBride ME [2], 92-96% of the samples from the "in use" bar soaps (with and without antibacterial) yielded positive culture (microorganisms listed in [Table 2]). Also, in a study conducted in the household setting, Brook SJ and Brook I [3] studied the microbial content of 14 bars of soap. The major bacteria isolated were Staphylococcus species and Enterobacteriaceae. It was also observed that the number of bacteria isolated from heavily used soaps which were wet were higher than from infrequently used soaps that were dry.

In the present study, the diverse microorganisms [Table 1] found on the "in use" bar of soap suggests that bar soap may be an important reservoir of infection. Though the microbial isolates belong to the normal commensals of the body and also constitute the normal environmental flora, the pathogenic Staph. aureus was also isolated. Staph. aureus (also called as Hospital Staphylococci), E coli and Klebsiella which are isolated are shown to be the prime organisms, that cause nosocomial infections. The other microorganisms, though normal commensals, are potential pathogens. The use of such a contaminated product may thus serve as a continuous source of infection and re-infection for the users[1]. The involvement of bar soap in the outbreak of infection in the hospital has been mentioned earlier by Kabara JJ and Brady MB [1] and Jacques L et al [5].

As is evident from Table 2, there is variation in the isolates of the microorganisms from the "in-use" bar soap compared to, However this can be attributed to the fundamental differences in the procedural aspects, soap brands, site of the study and experimental protocol. For example, our study is of a cross-sectional nature or single sampling (TO and T7) in contrast to the multiple sampling (T0, Tl, T2, T3, T4, T7) studies of Kabara IT and Brady MB [1] and McBride ME [2]. Interestingly, it has been observed in the longitudinal study of McBride ME [2], the microbial flora of "in use" soap products displayed a variation in number and there also existed sporadic appearance and disappearance of different microorganism over the period of time, indicating that the organisms were continuously being removed either mechanically or due to the self sterilizing activity of the soap, as is described by Barman EA and Judge LF [6].

Contamination of bar soap can be attributed to two reasons. Contamination from the environment is the first possible cause, as the bar soap is placed openly in a dish, exposed to the environmental organisms. Secondly, the use of soap by dental personnel means the soap in use is being continously inoculated with bacteria from their hands.


The findings of this study have shown that the "in-use" bar soap is in fact a harbor for microorganisms, thereby possibly causing greater harm and thus nullifying the original purpose of hand washing. This study report should be considered as an "eye opener" by every individual dentist whose duty towards all the patients collectively is to protect them from cross-infection. Hence, this attempt to create awareness. The Center for Disease Control -1989 chapter 8, suggests that bar soaps should not be used for hand washing. As alternatives for the adjuncts used for hand washing the dentists could use a disinfectant which is not exposed to the environment or to the previous users hands, like the liquid soap, single use soap tablet and soap strips or surgical scrubs.


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