Influence of Nonnutritive Sucking Habits on the Oral Carriage of Escherichia coli

Objectives This study aimed to evaluate the impact of nonnutritive sucking habits on the presence of oral Escherichia coli. Methods One hundred and twenty children aged 3–5 years old were enrolled in the present case-control study, as follows: 60 children with continuous pacifier and thumb sucking habits (study group) and 60 children without any sucking habits (control group). The children in the two groups were matched in terms of age and gender. Information was gathered from the parents concerning their children using a special sheet. Sterile swabs were taken from both groups and cultured on agar plates. Then, they were subjected to further biochemical tests to identify E. coli species. The mean of the E. coli count was determined for each child. Descriptive, independent t-test and chi-square test statistics were used. The level of significance was set at p < 0.05. Results The presence of nonnutritive sucking habits was related to a higher carriage of E. coli among children. Conclusion Nonnutritive sucking habits may act as a predisposing factor that enhances the colonization of oral E. coli.


Introduction
Sucking habits involve frequent neuromuscular activities (conscious and unconscious) and belong to two types: nutritive, in which nutrition can be gained through child sucking; and nonnutritive, in which the child tries to satisfy his/her psychological needs [1][2][3][4]. In many countries, nonnutritive sucking habit (NNSH) is a popular norm in infancy and early childhood; however, it is considered abnormal over 3 years of age [2,5]. While thumb and digit sucking are performed by some children to comfort themselves [1], others soothe and satisfy their unending need to suck by using a dummy (pacifer), which is a plastic, silicon, or rubber teat-like object usually given to infants and toddlers [6]. Although NNSH may provide some benefcial efects, it has more adverse outcomes than positive ones. Some of these negative efects may be related to dentition, such as the development of dental caries and tooth malalignment [7][8][9]. However, others are related to the child's general health and alteration of the oral and gastrointestinal microbiota, which leads to increased infection [10] and asthma [11]. In addition, NNSH has an adverse efect on the duration of breastfeeding; it may increase the chance of early weaning [7]. Furthermore, NNSH is implicated in the entrance of numerous types of microorganisms into the oral cavity because the objects used for NNSH can act as strong reservoirs of various microorganisms found in the environment [12].
Members of Enterobacteriaceae, such as E. coli, are mainly found in water, soil, plants, and animals. Tey are found in the human intestinal canals [13]. However, when found in the oral cavity by NNSH or because of poor hygiene maintenance, they are considered as transient pathogens that might lead to debilitation of general conditions [14].
In the literature, data regarding evaluation of the efect of NNSH and E. coli are scarce. It was reported that nail biting and thumb sucking habits played an important role in the oral carriage of Enterobacteriaceae [12,14]. Meanwhile, it was reported that children with pacifer sucking habit had higher carriage of oral E. coli, which was associated with diarrhea and increase in gastroenteritis [15,16]. Other infections caused by E. coli may include intestinal infections, cholecystitis, and bacteremia [17].
Not much available data link the presence of E. coli in the oral cavity with the NNSH of children (pacifer and thumb sucking habits), which was the premise that the present study was based on. Terefore, this study was conducted to explore whether the presence of oral E. coli among children was associated with their NNSH, which was the primary objective of this study, while the secondary objectives were to fnd if the type of feeding and the rank of the child had any relation to the NNSH and the oral carriage of E. coli.

Study Design and Sample Population.
Tis case-control study was conducted after getting the ethical approval from the ethical committee of University of Baghdad (Ref. 194320 in September 23, 2020) in accordance with the declaration of the guiding principles of Helsinki [18]. Te subjects were recruited from kindergartens in Baqubah city, the center of Diyala Governorate, Iraq, from December 2020 to March 2021. Tis was a multistage study. Te frst step was the determination of the case group of the study sample (children with pacifer or thumb sucking habit). Te kindergarten's authorities were contacted to explain the purpose of the study. Before the start, the aims of the study were clarifed to the parents and a signed permission was obtained from them via a consent form. Healthy children aged 3 to 5 years were the target of the study sample. Children with chronic disease, those who took antibiotics and/or antimycotics for the previous three months, and those whose parents refused to let them participate and/or only partially flled the questionnaire were excluded.

Data
Collection. Data collection was done using a questionnaire that was designed to gather the needed information. Tis questionnaire included questions on demographic information, general health, type of feeding habit, the rank of the child in the family, and occurrence of deleterious NNSH (thumb and pacifer sucking). Te questionnaire was sent to the parents, and then the completed questionnaire was collected the next day. Children were classifed into two groups according to the presence of oral habits, as follows: (1) the study group, which included children with continuous pacifer and thumb sucking habits; and (2) control group, comprising children from the same kindergarten who had no sucking habits and were age and gender-matched with those in the study group.

Microbiological Examination.
Microbiological samples were obtained from children. Tis was done by swabbing the oral mucosal surface of the children (hard palate, dorsum of the tongue, and cheek and foor of the mouth) using a plane sterile cotton swap (MDIC, Saudi Arabia) [19]. Each swab was streaked on blood agar (Biolife-Haly) and MacConkey agar (Oxoid, England), which is the selective medium for E. coli, and incubated aerobically for 24 h at 37°C. Ten, the colonies were diagnosed by biochemical tests, which included catalase, coagulase, and oxidase tests. In addition, the API 20E system was used for further identifcation; this system is commonly used in identifying E. coli species from suspected isolates [15,17,20]. In this study, method for counting E. coli colonies depended on the plate counting method. Serial dilution was done to get clear colony forming unit (CFU) on the MacConkey agar. Ten, a direct record to the counts of the colonies with the typical morphology were obtained with regard to the dilution factor and volume cultivated according to the following equation: "(number of colonies multiplied by the dilution factor) divided by the volume of culture plates" [21].

Statistical Analysis.
Data were translated into a computerized database structure. Microsoft Excel with Statistical Package for Social Sciences (SPSS) (version 20-computer software, IBM, NY, USA) was used for the data analysis. Data of this study were normally distributed. Te dependent variable was the E. coli count, whereas the independent one was the NNSH. Variables such as age, gender, type of feeding, and the rank of the child in the family were considered as confounding variables. Descriptive statistics were used. Te mean and standard error of the E. coli count were determined, and statistical diferences were found using ttest. However, frequency distribution was used for the categorical variables, and the chi-square test was used to fnd the statistical diference. Te level of signifcance was set at p < 0.05.

Results
A total of 1100 children were screened, and 120 (56 boys and 64 girls with ages ranging from 3 years old to 5 years old) were enrolled (Figure 1). Among those who practiced NNSH, the carriage rate of E. coli was higher with a statistically signifcant diference. More girl children had NNSH than boys. Meanwhile, girls in the NNSH group showed a higher mean of E. coli compared with boys in the same group and with those in the control group (Table 1).
Concerning the method of feeding according to the mean of E. coli presence, children in the NNSH group had a higher mean of E. coli carriage compared to the children who were without sucking habit with a statistical signifcant diference. Mixed feeding method (breast and bottle-feeding) was the predominant method of feeding among the children in the NNSH group and those who were without sucking habit (53 and 38, respectively) ( Figure 2).
More children who were the last children of the family had NNSH. However, a higher mean of E. coli presence was observed among sole children (Figure 3).

Discussion
In this study, in all age groups, a higher mean of E. coli was present among children in the NNSH group when compared with those without any sucking habit, with a statistical signifcant diference, especially among those who were 5 years old. Tis higher presence of microorganisms in the NNSH group was in agreement with the fndings of other studies [13,15]. In the intestinal tract, E. coli is usually present as a commensal [22], but it may be present in the oral cavity as a transient microorganism. Its presence in the oral ecosystem is still considered an infection of the oral structures, in spite of its frequent and normal presence in other sites of the human body [23]. Meanwhile, its presence in the oral cavity may increase among children who have NNSH, especially if they neglect oral hygiene or have poor maintenance of personal hygiene, in which case, microbial entry could be via the orofecal route [24]. A potentially alarming efect might result from the entry of enteric microorganisms into the body via the oral cavity [25].

International Journal of Dentistry
Although the NNSH group had a higher mean of E. coli, the carriage rate of E. coli by gender revealed that girls had higher mean. Tis could be due to the fact that girls exhibit emotions and are more sensitive; thus, they may practice NNSH more frequently than boys [26].
Concerning the type of feeding in relation to the mean of E. coli, children in the NNSH group had the higher mean of E. coli count for both types of feeding found in this study (breast and mixed feeding), and children who were fed by the mixed type of feeding had higher mean of E. coli in both groups. Tis result might be due to the protective impact of breastfeeding against the Gramnegative microbial infection via the enhancement of intraluminal agglutination or by bactericidal efect. Possibly, protection might be related to the inhibition of bacterial attachment to the surface of the oral epithelial tissues [27].
Te mean of the E. coli count between the two groups according to the rank of the child revealed that a higher mean of E. coli was present among children of all ranks within the NNSH group compared with those without sucking habit. However, the results were statistically signifcant only for the frst and the last children. Possibly, those children could practice the habit more frequently than the other children.

Conclusion
Te NNSH showed high correlation with the presence of E. coli. Tey may act as a predisposing factor that enhances the colonization of oral E. coli among children. Terefore, stopping these habits may have a signifcant role in preventing dental as well as oral diseases. Pedodontists should consider the impact of NNSH in increasing the prevalence of E. coli, which makes children with this habit more prone to infection. Nevertheless, in an attempt to prevent contamination, children with NNSH should be instructed to maintain proper personal hygiene, and their parents should be instructed to eliminate these habits as soon as possible because of their bad efects on oral and general health.

Limitations of the Study.
Tis study only considered two types of NNSH, namely, thumb sucking and pacifer sucking. Other types, i.e., nail biting, mouth breathing, and bruxism, may also have a deteriorating efect on oral health [23,[28][29][30][31]. Other limitations related to the present study were that bacteria other than E. coli were not considered. Terefore, further studies are needed for investigating other types of NNSH to assess whether a relationship exists between the oral health status and the spread of E. coli.

Data Availability
Te dataset used in the current study is available from the corresponding author upon request.

Ethical Approval
Ethical approval was obtained from the ethical committee of University of Baghdad (Ref. 194320 in September 23, 2020), and this study was conducted in accordance with the declaration of guiding principles of Helsinki.

Consent
Signed permission was obtained from the parents via a consent form after explaining the objective of the study.

Conflicts of Interest
Te author declares that there are no conficts of interest.