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Research Article - (2019) Volume 10, Issue 1

Streptococcus mutans Dental Caries among Patients Attending Debre Berhan Referral Hospital, Ethiopia
Demissew Shenkute and Tsegahun Asfaw*
Department of Medical Laboratory Science, College of Medicine, Debre Berhan University, Debre Berhan, Ethiopia
*Correspondence: Tsegahun Asfaw, Department of Medical Laboratory Science, College of Medicine, Debre Berhan University, Ethiopia, Email:

Received: 20-Nov-2018 Published: 04-Jan-2019, DOI: 10.35248/2155-9597.1000350


Background: Dental caries is an irreversible microbial disease of the calcified tissues of the teeth. Streptococcus mutans is a bacterial resident of the oral cavity and is considered to be the principal etiological agent of dental caries in humans. Therefore, the aim of this study was to determine the prevalence and risk factors associated with Streptococcus mutans dental caries.

Methods: A cross sectional study was conducted among patients who attended Debre Berhan referral hospital dental clinic. Patient’s demographic and clinical information was collected by using pre-tested questionnaire. Dental plaques from all patients was picked up by forceps and suspended in to phosphate-buffered saline for further Streptococcus mutans identification.

Result: From a total of 115 study participants 56 (48.7%) and 59 (51.3%) were males and females respectively. The overall prevalence of Streptococcus mutans was 79 (68.7%) among patients with dental caries. participants 25 (21.7%) had gem bleeding and 47 (40.9%) of the participants had previous tooth decay.

Conclusion: In this study, again Streptococcus mutans is the common public health problem among dental caries patients. Drinking soft drinks, oral debris and gingival index were the associated risk factor for dental caries of Streptococcus mutans.


Dental plaque is an adherent deposit of bacteria and their products, which forms as a white greenish or even yellow film on all tooth surfaces. Dental plaque accumulates naturally at stagnant or retentive sites formed after one to two days with no oral hygiene [1]. Dental caries is the single most prevalent and costly infectious disease worldwide, affecting more than 90% of the population in the US. The development of dental cavities requires the colonization of the tooth surface by acid producing bacteria, such asStreptococcus mutans, in conjunction with the frequent ingestion of a cariogenic high sucrose diet, the substrate for acid and glucan production by organisms. The elevated amounts of acid and glucans modulate the establishment of cariogenic organisms within tightly adherent biofilms known as dental plaque [2]. Streptococcus mutansis one of the major etiological factors of dental caries. Tooth surfaces colonized with S. mutans are at a higher risk for developing caries [3]. Dental caries is an irreversible microbial disease of the calcified tissues of the teeth, which is characterized by demineralization of the inorganic portion and destruction of the organic substance of the tooth, which often leads to cavitation. Dental caries is a multifactorial disease, which is caused by host, agent, and environmental factors [4]. Streptococcus mutans are gram positive cocci bacteria. These facultative anaerobes are commonly found in the human oral cavity, and are a major contributor of tooth decay. S. mutansgrow at temperatures between 18°C-40°C. Streptococcus mutansare a cariogenic microorganism that breaks down sugar for energy and produces an acidic environment, which dematerialize the superficial structure of the tooth. The result of the conversion disintegrates the coating of the tooth then later dissolves the Calcium molecule creating a hole [5,6]. S. mutanscan be isolated from individuals either with or without a history of caries, but the development of dental caries dependent on the bacterial load strain variation of S.mutans including, acid-utility, biofilm-formation potential, and production of glucans [7,8].

Materials and Methods

Study area and period

The study was conducted at Debre Berhan referral hospital, which is located around 130 km away from Addis Ababa. The study was conducted from March, 2017 to August, 2018.

Study design

A cross sectional study was conducted.

Inclusion and exclusion criteria

All patients attending dental clinic of Debre Berhan referral hospital with clinical manifestation of dental caries and who are volunteer and able to give sample were included. Patients who are taking antibiotics in the last 30 day were excluded.

Sample size and sampling technique

The sampling technique was based on convenient sampling method. The sample size was all patients with clinical manifestation of dental caries who were visited Debre Berhan referral hospital dental clinic and fulfill inclusion criteria.

Data collection methods

Patient’s socio demographic and clinical information was collected by using pre-tested questionnaire. All study participants was examined by dental doctor. Dental plaques from all patients were picked up through forceps (probe) and transferred into 2 ml of sterile tube containing phosphate-buffered saline and processed immediately after collection in Debre Berhan university microbiology laboratory [9].

Isolation and identification of S. mutans

The dental plaque suspension was vortexed for 30 s for content homogenization. Then a volume of 100 μl was spread onto Mitissalivaris (MS-agr) by using sterile cotton swab and incubated in 5% CO2 for 48 hours at 37°C. A colony count of more than 250 colonies (104 cells/ml) was considered as positive samples. Small colony was subculture on the surface of blood-agar plates for further identification. A gram positive cocci, alpha hemolytic on blood agar, catalase negative mannitol, and lactose fermenters was considered S. mutans [1,10].

Data entry and analysis

Data was edited, cleaned and checked for its completeness and was entered SPSS version 16 for analysis. Patients’ Socio-demographic and clinical characteristics were described by using descriptive statistics. Bivariate and multivariate logistic regression analysis was done to identify the risk factors and p-value less than 0.05 was taken as statistically significant.

Ethical consideration

Ethical clearance was obtained from Debre Berhan University Ethical Review Board. Letter of permission was secured from Debre Berhan referral Hospital clinical director managements. Written informed consent and assent was obtained from the study participants. Any information concerning the patients was kept confidential and patients with positive result were communicated.

Quality control

To assure the quality of the data generated during the study, standard operating procedures were followed during media preparation and other laboratory procedures. Sterility check was performed to avoid the possibility of contamination. All reagents was checked for their expiry date and prepared according to the manufacturer’s instruction.


Among of 115 study participants, the overall prevalence of dental caries of Streptococcus mutans was 79 (68.7%).

Socio-demographic characteristics of the of the participants

Among 115 participants, 56 (48.7%) were males and 59 (51.3%) were females. The mean age of the participants was 32.67 years with standard deviation (SD=1.48). 64 (55.7%) and 51 (44.3%) of the participants were come from urban and rural area respectively. Regarding occupation 17 (14.8%) of them were housewife followed by farmer 13 (11.3%). In terms of educational status, majority of the residents, 34 (49.3%) has completed grade 12, as shown in Table 1.

  Socio- demographic characteristics Culture result for Streptococcusmutans   Total NO (%)
Positive NO (%) Negative NO (%)
Sex Male 43(37.4) 13(11.3) 56(48.7)
Female 36(31.3) 23(20.0) 59(51.3)
Place of residence Urban 41(35.7) 23(20.0) 64(55.7)
Rural 38(33.0) 13(11.3) 51(44.3)
Occupation Farmer 11(9.6) 2(1.7) 13(11.3)
Merchant 6(5.2) 5(4.3) 11(9.6)
Employed 10(8.7) 7(6.1) 17(14.8
Unemployed 3(2.6%) 1(0.9) 4(3.5)
Housewife 11(9.6) 6(5.2) 17(14.8)
Driver 1(0.9) 0(0) 1(0.9)
Other 37(32.2) 15(13.0) 52(45.2)
Educational status Illiterate 36(31.3) 10(8.7) 46(40.0)
Read &write only 2(2.9) 3(4.3) 5(7.2)
1-4 grade 5(7.2) 5(7.20) 10(14.5)
5-8 grade 7(10.1) 1(1.4) 8(11.6)
9-12 grade 7(10.1) 5(7.2) 12(17.4)
Above 12 22(31.9) 12(17.4) 34(49.3)

Table 1: Socio-demographic characteristics of patients attending dental clinic of Debre Berhan referral hospital from March 2017 to August 2018.

Knowledge and practice on tooth cleaning habit of the respondents

From 115 participants 73 (63.5%) were cleaned their teeth and among these 73 (63.5%), 40 (54.8%) were used tooth stick and tooth brush respectively. From respondents who cleaned their teeth more than half of them were cleaned their teeth in sideway (horizontally) and also most of the participants were cleaned their tooth after meal and morning only. Very few were cleaned their teeth morning and before going to bed as shown in Table 2.

Knowledge and practice on oral health Culture result for S.mutans
Positive NO (%) Negative NO (%)                    Total NO (%)
Habit of cleaning teeth Yes 47(40.9) 26(22.6) 73(63.5)
No 32(27.8) 10(8.7) 42(36.5)
Materials used to clean teeth Tooth Stick 28(38.4) 12(16.4) 40(54.8)
Charcoal 1(1.4) 2(2.7) 3(4.1)
Tooth brush & rinse with water 9(12.3) 8(11.0) 17(23.3)
Others 9(12.3) 4(5.5) 13(17.8)
Frequency of cleaning teeth     Once a day 22(30.1) 4(5.5) 26(35.6)
After each meal 2(2.7) 3(4.1) 5(6.8)
Before and after each meal 2(2.7) 3(4.1) 5(6.8)
More than once a day 3(4.1) 4(5.5) 7(9.6)
Irregularly 18(24.7) 12(16.4) 30(41.1)
Way of cleaning teeth Top to bottom 6(8.2) 5(6.8) 11(15.1)
Side way 23(31.5) 10(13.7) 33(45.2)
Mixed 16(21.9) 11(15.1) 27(37.0)
Circular 2(2.7) 0(0.0) 2(2.7)
Time of brushing teeth Morning only 13(17.8) 10(13.7) 23(31.5)
After meal 16(21.9) 8(11.0) 24(32.9)
Before meal 3(4.1) 0(0.0) 3(4.1)
Before going to bed 2(2.7) 0(0.0) 2(2.7)
Irregular 11(15.1) 8(11.0) 19(26.1)

Table 2: Knowledge and practice on tooth cleaning habit of patients attending dental clinic of Debre Berhan referral hospital from March 2017 to April 2018.

Associated risk factor for dental caries

Sixteen (13.9%) and 8 (7.0%) of the study participants had a habit of drinking alcohol and smoking cigarette respectively. Twenty eight (24.3%) of the participants had a habit of chewing chat. Seventy two (62.6%) of the participants had a habit of taking sweet in take or food.

Twenty two (30.6%) of the participants were taking sweet intake irregularly. Eighty one (70.4%) of the participants had a habit of taking soft drink and significantly associated with S. mutans dental caries (p=0.01) as shown in Table 3.

Associated risk factor Culture result Streptococcusmutans p- value
Positive No (%) Negative No (%) Total No (%)
Habit of drinking alcohol Yes 13(11.3) 3(2.6) 16(13.9) 0.24
No 66(57.4) 33(28.7) 99(86.1)
Frequency of drinking
Always 0(0.0) 1(6.2) 1(6.2) 0.10
Sometimes 6(37.5) 1(6.2) 7(43.8)
Rarely 7(43.8) 1(6.2) 8(50)
Habit of smoking cigarette Yes 8(7) 1(0.9) 9(7.8) 0.17
No 71(61.7) 35(30.4) 106(92.2)
Frequency of smoking cigarette Regularly 5(55.6) 0(0.0) 5(55.6) 0.32
Occasionally 3(33.3) 0(0.0) 3(33.3)
Rarely 0(0.0) 1(11.1) 1(11.1)
Habit chewing chat Yes 23(20) 5(4.3) 28(24.3) 0.08
No 56(48.7) 31(27.0) 87(75.7)
Frequency of chewing chat Regularly 8(28.6) 1(3.6) 9(32.6) 0.40
Occasionally 12(42.9) 2(7.1) 14(50.0)
Rarely 3(10.7) 2(7.1) 5(17.9)
Habit of taking sweet intakes or food Yes 46(40) 26(22.6) 72(62.6) 0.15
No 33(28.7) 10(8.7) 43(37.4)
Kind of sweet intake Chocolate 0(0.0) 3(4.2) 3(4.2) 0.20
Candy 1(1.4) 1(1.4) 2(2.8)
Sugar cane 6(8.3) 3(4.2) 9(12.5)
Sugared coffee 21(29.1) 8(11.1) 29(40.3)
Sugared tea 12(16.7) 9(12.5) 21(29.2)
Others 6(8.3) 2(2.8) 8(11.1)  
Frequency of taking sweet intake Once a day 13(18.1) 3(4.2) 16(22.2) 0.15
After each meal 8(11.1) 1(1.4) 9(12.5)
More than once a day 12(16.7) 10(13.9) 22(30.6)
Irregularly 12(16.7) 10(13.9) 22(30.6)
Every other day 1(1.4) 1(1.4) 2(2.8)
Once time per week 0(0.0) 1(1.4) 1(1.4)
Habit of taking soft drinks Yes 50(43.5) 31(27.0) 81(70.4) 0.01
No 29(25.2) 5(4.3) 34(9.6)
Frequency of taking soft drink Regularly 3(3.7) 4(4.9) 7(8.6) 0.26
Occasionally 28(34.6) 12(14.8) 40(49.4)
Rarely 19(23.5) 15(18.5) 34(42.0)
Presence xerostomia Yes 4(3.5) 0(0.0) 4(3.5) 0.17
No 75(65.2) 36(31.3) 111(100)
Diabetes mellitus Yes 15(13.0) 4(3.5) 19(16.5) 0.29
No 64(55.7) 32(27.8) 96(83.5)  

Table 3: Associated risk factor for dental caries in patients attending dental clinic of Debre Berhan referral hospital from March 2017 to April 2018.

Clinical data on oral health

In this study, a total of 115 participants 25 (21.7%) had gem bleeding and 47 (40.9%) of the participants had previous tooth decay. Nearly more than half the respondents had oral debris covering not more than one third of the tooth surface. Only 42 (36%) were free from oral debris. Oral debris has statistically significance association withS. mutans dental caries (P=0.022). Most of the participants 55 (47.8%) had normal gingival index and 50 (43.5%) had mild inflammation but only 1 (0.9%) had sever inflammation. Gingival index has statistically significant association with S. mutans dental caries (P=0.002). Fifty eight (50.4%) of the participant had no calculus index and 41 (35.7%) had mild super gingival calculus. Only few 3 (2.6%) had excessive supra and sub gingival calculus as shown in Table 4.

Clinical finding Result p–value
Positive No (%) Negative No (%) Total No (%)
Gem bleeding Yes 18(15.7) 7(6.1) 25 (21.7) 0.69
No 61(53.0) 29(25.2) 90 (78.3)
Previous tooth decay Yes 35 (30.4) 12 (10.4) 47 (40.9) 0.27
No 44 (38.3) 24 (20.9) 68 (59.1)
Oral debris   No debris 22 (19.1) 20 (17.4) 42 (16.5) 0.022      
Soft Debris covering not more than 1/3 of the tooth surface 47 (40.9) 14 (12.2) 64 (53.0)
Soft debris covering more than 1/3 but not more than 2/3 of the exposed tooth surface 9 (7.8)  1(0.9) 10 (8.7)
soft debris covering more than two third of exposed tooth surface 1(0.9) 1(0.9) 2 (1.8)
Plaque index no plaque 1(27.0) 20(17.4) 51(44.4) 0.23
plaque adhering to the      free gingival margin which cannot be seen by naked eye 39(33.9) 12(10.4) 51(44.3)
moderate accumulation of deposits on the gingival margin which can be seen with naked eye   9(7.8) 4(3.5)   13(11.3)
Gingival index Normal 30(26.1) 25(21.7) 55(47.8)   0.002
mild inflammation 40(34.8) 10(8.7) 50(43.5)
Moderate inflammation 9(7.8)                   0(0) 9(7.8)
sever inflammation 0(0) 1(0.9) 1(0.9)
Calculus index   No calculus 36(31.3) 22(19.1) 58(50.4)   0.24
Mild super gingival            calculus 29(25.2) 12(10.4) 41(35.7)
Moderate  supra & sub gingival calculus 11(9.6) 2(1.7) 13(11.3)
Excessive supra & sub gingival calculus 3(2.6) 0(0) 3(2.6)

Table 4: Clinical finding in patients attending dental clinic of Debre Berhan referral hospital from March 2017 to April 2018.

Class of tooth decay

From the total 47 tooth decay cases, 21 (44.7%) of them had class I followed by class II which was 17 (36.2%) as shown in Table 5.

Class of tooth decay Frequency No (%)
Class I 21 (44.7)
Class II 17 (36.2)
Class III 4 (8.5)
Class IV 2 (4.3)
Class V 3 (6.4)
Total 47 (100)

Table 5: Frequency of class of tooth decaying patients attending dental clinic of Debre Berhan referral hospital with culture results for S. mutans from March 2017 to April 2018.


In Ethiopia, there is scarcity of data on Streptococcus mutans dental caries. In this study Streptococcus mutans dental caries is the major public health problem among patients attending dental clinic of Debre Berhan referral hospital. In this study, the prevalence of Streptococcus mutansdental caries was found to be (68.7%) which is comparable with a study conducted in Brazil (68.5%) [11], China (67.5%) [12] and Srilanka (68.8%) [13]. However, it was lower than study conducted in Qatar (85%) [14], Saudi Arabia (80%) [15]. It was higher than study conducted in other parties of Ethiopia particularly in Gondar (36.3%) [15].The difference could be due to the difference in knowledge and practice on oral hygiene.

Habit of taking soft drink was found to be statistically significance association with Streptococcus mutans dental caries. This also supported by similar findings done in India and Zimbabwe respectively [16,17]. This also might be associated with acid production by cariogenic organism such as Streptococcus mutans that adherent to teeth as result of fermentation of soft drink. Later the enamel of tooth went to tooth decay.

In this study, the highest prevalence was seen in urban area 41 (35.7%) than rural 38 (33.0%). This finding was in agreements with a study done in Zimbabwe [17]. The possible reason for this also might be due to the habit of urban population taking soft drink and food.

Oral debris is a major risk factor for dental caries; that has statistically significant association withStreptococcus mutans dental caries than those who had no oral debris. This finding also confirms other findings [18]. Moreover; gingival index was significance association with Streptococcus mutans dental caries. Patients with gingival index were more likely to have dental caries ofStreptococcus mutans . This also might be a good indicator of poor oral hygiene practices [19]. Because gingival index increase Streptococcus mutans colonization and in severe cases it involves loses of the enamel.

In this study drinking alcohol, smoking cigarette, taking soft intake, plaque index and calculus index and chewing chat has no significant association withStreptococcus mutans dental caries [20]. The reason for this discrepancy might be short data collection period and small number of the study population.

Conclusions and Recommendations

Dental caries of Streptococcus mutansis the common public health problem among patients attending at dental clinic of Debre Berhan referral hospital. Soft drinks, oral debris and gingival index were the associated risk factor for dental caries of Streptococcus mutans . Health education on oral hygiene, dietary habit and dental visit should be given to prevent and control Streptococcus mutans dental caries. Moreover, further studies using all diagnostic method should be done.

Conflict of Interests

The authors declare that they have no conflict of interests.


This work was not funded by any organization.

Authors Contributions

DS performed the laboratory activities. DS analyzed the data. TA wrote the manuscript. All authors read and approved the final manuscript.


We would like to thank Debre Berhan University for giving this opportunity. We also thank staffs of dental clinic of Debre Berhan referral hospital for their help during data collection process.


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Citation: Shenkute D, Asfaw T (2019) Streptococcus mutans Dental Caries among Patients Attending Debre Berhan Referral Hospital, Ethiopia. J Bacteriol Parasitol 10:350 doi:10.4172/2155-9597.10.350

Copyright: © 2019 Shenkute D, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.