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Year : 2015  |  Volume : 6  |  Issue : 2  |  Page : 211-214  

Influence of nail biting and finger sucking habits on the oral carriage of Enterobacteriaceae

Department of Oral and Maxillofacial Pathology, Narayana Dental College and Hospital, Chinthareddypalem, Nellore, Andhra Pradesh, India

Date of Web Publication4-May-2015

Correspondence Address:
Firoz G Kamal
Narayana Dental College and Hospital, Chinthareddypalem, Nellore Andhra Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0976-237X.156048

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Background: Oral habits like thumb sucking and nail biting are pernicious habits that act as an adaptive function in obtaining pleasure and subduing anxiety. These habits may also act as carriers of numerous microorganisms into the oral cavity, of which, Enterobacteriaceae members are transient pathogens, which might result in debilitating systemic conditions. Aim: To study the oral carriage of Enterobacteriaceae in children having habit of nail biting and thumb sucking. And to study the association of the organism with the individual's respective plaque indices. Subjects and Methods: Totally, 40 chronic nail biters, 40 chronic thumb suckers, and 20 controls (no habit) (8-15 years old) were enrolled in the study. Appropriate history and their plaque indices recorded. Sterile containers were used to collect the salivary samples and later cultured on Agar plates. Biochemical tests categorized the organisms into subspecies. Statistical Analysis Used: ANNOVA, Student's t-test. Results: Presence of a nail biting habit indicated a higher plaque index, which in turn showed a higher carriage of Enterobacteria spps, predominantly Escherichia coli. Conclusions: Oral surgical intervention in individuals with pernicious oral habits need to be counseled and educated on the possible complications, which might otherwise provide an environment that disseminates these microorganisms resulting in a broad range of local and systemic infections.

Keywords: Bacteremia, cellulitis, Enterobacteriaceae, extraction complications, nail biting, thumb sucking

How to cite this article:
Kamal FG, Bernard RA. Influence of nail biting and finger sucking habits on the oral carriage of Enterobacteriaceae. Contemp Clin Dent 2015;6:211-4

How to cite this URL:
Kamal FG, Bernard RA. Influence of nail biting and finger sucking habits on the oral carriage of Enterobacteriaceae. Contemp Clin Dent [serial online] 2015 [cited 2022 May 25];6:211-4. Available from:

   Introduction Top

The mouth harbors a diverse, abundant, and complex microbial community, which tends to inhabitate both the soft and hard tissues in the form of biofilms. [1] However, a highly efficient innate host defense system constantly monitors the bacterial colonization and prevents bacterial invasion of the local tissues. [2],[3] Accumulating evidence suggests the impact of the dental diseases on the general health of the individual, warranting a harmonious relation of the microorganisms with that of the oral tissues, albeit any shift in this balanced ecology would unfold a series of events that might result in a disease status.

Habits such as thumb sucking and nail biting, are seen usually in children as an adaptive function of obtaining pleasure. [4],[5] These habits act as carriers of numerous microorganisms into the oral cavity, of which, Enterobacteriaceae members are transient pathogens, which might result in debilitating systemic conditions. [6],[7] We undertook the present study to find the prevalence of Enterobacteriaceae in children with both thumb sucking and nail biting habits and to correlate it with their respective plaque indices.

   Subjects and Methods Top

The study population comprised of 100 subjects between the ages of 8-15 years and were grouped into three categories, nail biters group (NBG), thumb suckers group (TSG), and the controls group (CGs). Individuals consulting the Departments of Oral Medicine, Pedodontics and Orthodontics of the institute were selected for the study after an informed consent was obtained.

Details in relation to age, sex, oral hygiene practice, medical history, and data pertinent to their nail biting and thumb sucking habits and plaque index score recorded. The subjects were instructed to rinse their mouth with 10 ml of phosphate-buffered saline solution for 60 s [8] and were asked to expectorate the rinse into a universal container. Individual samples were centrifugation at 17000 g (12500 rpm) for 10 min, following which the supernatant was discarded, and the deposit re-suspended in 1 ml of phosphate-buffered saline to obtain a concentrated rinse. The procedures followed were in accordance with the ethical standards on human experimentation.

One loop full of concentrated rinse was inoculated on to Mc Conkey's agar and blood agar culture media using standard streak plate method. Batches of culture plates were incubated at 37°C for 24 h, and the growth of Enterobacteriaceae observed as pink and white colored colonies.

The suspected colonies were subjected to Gram stain for the identification of Gram-negative bacteria. Once identified, the colonies were further subjected to biochemical reactions such as oxidase test, indole test, methyl red test, Voges-Proskauer test, and citrate utilization test for the subspecies identification.

   Results Top

The mean plaque index was highest in NBG at 1.834 while in TSG 1.763 and in the CG 1.7. With a statistical difference between NBG and CGs [P = 0.008, [Table 1].
Table 1: Mean plaque scores between two groups using t-test

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Carriage rate of Enterobacteria in all the groups was analyzed using Pearson Chi-square test, and it was found that an increased carriage was seen among NBG when compared to the CG [P = 009, [Table 2].
Table 2: Comparison of Enterobacteriaceae carriage rate between two groups using Pearson Chi - square test

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Four species of Enterobacteria were isolated, which included  Escherichia More Details coli, Klebsiella, Proteus, and Enterobacter. While the most commonly isolated organism in nail biting children was E. coli, the less commonly isolated organism was Proteus. In thumb-sucking children, Klebsiella was isolated the most while the less commonly isolated organism was enterobacter. On the other hand, only Klebsiella was isolated from the CG [Table 3].
Table 3: Species of Enterobacteriaceae isolated

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   Discussion Top

Members of Enterobacteriaceae are Gram-negative straight rods, aerobic and facultative anaerobic, oxidase negative and catalase-positive organisms, mainly distributed in soil, water, plants, animals, and intestinal canal of humans. [9] These Enterobacteria, which are considered as pathogenic, are transient organisms of oral cavity and can gain entry through oral pernicious habits or due to poor hygiene maintenance, but do not cause any disease or any alteration of the oral microbial flora as such. The most notable species of Enterobacteria considered as pathogenic are Enterobacter clocae, Enterobacter aerogenes, and Enterobacter agglomerans.[10] These are the most common pathogens associated with hospital infections, representing 6% of all the nosocomial isolates and 10% of all pneumonia isolates. [11],[12]

Reports suggest that enteric organisms in the oral cavity are responsible for the post extraction cellulitis of the floor of the mouth and neck caused by  Salmonella More Details cholerasius. [13] In some cases, Enterobacteria like E. aerogenes and E. coli along with other Gram-negative organisms are the causative agents in osteomyelitis of the mandible. [14]

Earlier studies have reported that these organisms can cause bacteremia in up to 5-10% among all the Gram-negative infections in adults and up to 0.6% of all the Gram-negative infections in children. [15]

Literature revealed that environmental organisms can be inoculated into the oral cavity through paranormal habits like nail biting resulting in transmission of infections to other parts of the body, by contaminated hands or environmental objects, which may be responsible for the cause of morbidity and mortality worldwide. [16]

The study analyzed the prevalence of the Enterobacteria organism in the stated population group, and correlated it to the study and CGs and to the oral hygiene status and isolated the predominant type of species in the Enterobacteria group.

The plaque index of all the groups was recorded and the mean levels of plaque among the individual groups were studied using the Student's t-test which showed a higher mean index value in the TSG (1.763), than the CG (1.7). Further comparison of mean plaque indices between NBG and CG showed an index value of 1.834, which was not consistent with the study of Baydas et al. (2.083) but giving us a statistically significant result using t-test, P = 0.008 [Table 1]. An ANOVA test was used to compare the Mean of all the three groups, which showed no statistically significant difference (P = 0.113). Saliva of the individuals was analyzed for isolation of the organism and it was found that an isolation of 42% was seen among NBG as against a 30% in TSG, with a 10% isolation in the CG. This was consistent with the studies done by Baydas et al. who stated that there was a higher carriage of Enterobacteria among NBG. A Pearson Chi-square test revealed a statistical significance (P = 0.009) in the prevalence of Enterobacteria between these two groups, NBG and CG [Table 2], indicating that this might be due to poor oral/general hygiene maintenance.

A similar study done by Reddy et al. showed an increased carriage rate of Enterobacteria among nails biters (65.6%), than the CG (8.2%). [17]

In a study [18] done on Caucasians for the prevalence of coliforms in the dental plaque, the isolation rate was 5% while Hägg et al. [19] reported an 11.1% prevalence of coliform carriage in the individuals on fixed orthodontic therapy. In another study of 120 healthy individuals by Mobbs et al., [20] a 6.6% prevalence of Enterobacteria was seen, of which, students showed the highest prevalence. This was found to be consistent with our study wherein the CG showed a 10% isolation.

The carriage of Enterobacteria, when compared between TSG and CG showed a higher prevalence in TSG (12%) than the CG (10%), though not statistically significant.

A lower isolation rate was seen in our study when compared to Baydas et al.'s study despite using the same technique. This could be attributed to the environmental conditions and geographic distribution of the organism, age, ethnic variations, socio-economic status, and oral hygiene status of the individuals and resistance to a particular organism as stated by Sedgley and Samaranayake et al. [9]

The data indicate that though there was no significance in between the overall mean plaque index, a significant difference between the NBG and the CG, in accordance with previous studies of Baydas et al., suggesting that there could indeed be a correlation between the nail-biting habit, plaque index, and the oral carriage of the organism.

The Enterobacteria species isolated in our study were E. coli, Klebsiella, Proteus, and Enterobacter. Of these, the most commonly isolated Enterobacteria among all three groups was E. coli (in 12 subjects), whereas the least isolated Enterobacteria was enterobacter (3 subjects) as shown in [Table 3]. Our results are consistent with the results of Baydas et al. and Sushma et al. 16 who showed a greater isolation of E. coli. Other organisms such as streptococci, staphylococci, pseudomonas, and candida were also seen along with Enterobacteria.

This indicates the greater prevalence of E. coli in humans among different population groups. Studies by earlier authors reported that E. coli was the most frequently isolated organism among Enterobacteriaceae family in different systemic illnesses. With these data, it can be suggested that E. coli gets a channel of entry into the oral cavity through the chronic nail biting and thumb sucking habits and can be a perpetrator of local and systemic infections.

Earlier studies have shown that surgical manipulation of the oral cavity in these individuals could lead to localized disease like gingivitis and systemic infections like bacteremia and infective endocarditis. [7]

   Conclusions Top

This study would like to emphasize the need of caution while surgically managing children, with nail biting and thumb sucking habits, to prevent the dissemination of environmental microorganisms into the oral cavity thereby preventing local and systemic complications.

   References Top

Samaranayake LP. Essential Microbiology for Dentistry. 3 rd ed.  Philadelphia: Churchill Livingstone, Elsevier Company; 2006. p. 255-66.  Back to cited text no. 1
Marsh P, Martin MV. Oral Microbiology. 4 th ed . Oxford, London: Wright Publishing Ltd.; 1999. p. 58-81.  Back to cited text no. 2
Nisengard RJ, Newman MG. Oral Microbiology and Immunology. 2 nd ed.  Philadelphia: W. B. Saunders Company; 1988. p. 120-8.  Back to cited text no. 3
Leung AK, Robson LM. Nail biting. Clin Pediatr 1990;29:690-2.  Back to cited text no. 4
Tanaka OM, Vitral RW, Tanaka GY, Guerrero AP, Camargo ES. Nailbiting, or onychophagia: A special habit. Am J Orthod Dentofacial Orthop 2008;134:305-8.  Back to cited text no. 5
Fuqua W, Brosh S. Nail biting. Practitioners Guide to Evidence Based Psychotherapy. New York: Spinger; 2006. p. 414-22.  Back to cited text no. 6
Baydas B, Uslu H, Yavuz I, Ceylan I, Dagsuyu IM. Effect of a chronic nail-biting habit on the oral carriage of Enterobacteriaceae. Oral Microbiol Immunol 2007;22:1-4.  Back to cited text no. 7
Samaranayake LP, MacFarlane TW, Lamey PJ, Ferguson MM. A comparison of oral rinse and imprint sampling techniques for the detection of yeast, coliform and Staphylococcus aureus carriage in the oral cavity. J Oral Pathol 1986;15:386-8.  Back to cited text no. 8
Sedgley CM, Samaranayake LP. Oral and oropharyngeal prevalence of Enterobacteriaceae in humans: A review. J Oral Pathol Med 1994;23:104-13.  Back to cited text no. 9
Ye Y, Li JB, Ye DQ, Jiang ZJ. Enterobacter bacteremia: Clinical features, risk factors for multiresistance and mortality in a Chinese University Hospital. Infection 2006;34:252-7.  Back to cited text no. 10
Bonomo RA, Fiorentino M, Salvatore A, Jacobs M, Morissey A, Whalen C, et al. Enterobacter species Bacteremia: Factors predictive of mortality at a tertiary care institution. Infect Dis Clin Pract 2009;9:123-7.  Back to cited text no. 11
Sedgley CM, Samaranayake LP. The oral prevalence of aerobic and facultatively anaerobic gram-negative rods and yeasts in Hong Kong Chinese. Arch Oral Biol 1994;39:459-66.  Back to cited text no. 12
Rubelman PA. Post extraction cellulitis caused by Salmonella cholerasius. J Oral Surg 1961;19:255-6.  Back to cited text no. 13
Mashberg A, Carroll MA, Morrissey JB. Gram-negative infections of the oral cavity and associated structures: Report of two cases. J Oral Surg 1970;28:376-81.  Back to cited text no. 14
Bonadio WA, Margolis D, Tovar M. Enterobacter cloacae bacteremia in children: A review of 30 cases in 12 years. Clin Pediatr (Phila) 1991;30:310-3.  Back to cited text no. 15
Cohen MB. Etiology and mechanisms of acute infectious diarrhea in infants in the United States. J Pediatr 1991;118:S34-9.  Back to cited text no. 16
Reddy S, Sanjai K, Kumaraswamy J, Papaiah L, Jeevan M. Oral carriage of Enterobacteriaceae among school children with chronic nail-biting habit. J Oral Maxillofac Pathol 2013;17:163-8.  Back to cited text no. 17
[PUBMED]  Medknow Journal  
Leitch JA, Lang M, Macfarlane TW, Mackenzie D. The prevalence and distribution of yeasts and coliforms in dental plaque. J Dent Res 1991;70:709.  Back to cited text no. 18
Hägg U, Kaveewatcharanont P, Samaranayake YH, Samaranayake LP. The effect of fixed orthodontic appliances on the oral carriage of Candida species and Enterobacteriaceae. Eur J Orthod 2004;26:623-9.  Back to cited text no. 19
Mobbs KJ, van Saene HK, Sunderland D, Davies PD. Oropharyngeal Gram-negative bacillary carriage: A survey of 120 healthy individuals. Chest 1999;115:1570-5.  Back to cited text no. 20


  [Table 1], [Table 2], [Table 3]

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