early acquisition of streptococcus mutans for children

Transcripción

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EARLY ACQUISITION OF STREPTOCOCCUS MUTANS
FOR CHILDREN
Fabiana P. M. Carletto Körber1, Lila S. Cornejo1, María G. Giménez2
1
Faculty of Dentistry, 2University Hospital of Maternity and Neonatology,
National University of Córdoba, Argentina.
ABSTRACT
Existing evidence reveals that in Early Oral Infection the main
route of transmission of Streptococcus mutans is mother-child
saliva contacts and that initial acquisition takes place during a
specific period of time denominated “Window of Infectivity”
that lapses between 6 and 30 months of the child’s life, with a
higher risk between 18 and 30 months of age.
The aim of the present study was to analyze Early Oral Infection. The levels of Streptococcus mutans in saliva and bacterial
plaque in the binomial mother-child 6 to 18 months after childbirth were evaluated.
Twenty-four mother-child binomials that attended the University Hospital of Maternity and Neonatology of Córdoba
participated in the study. Samples of saliva and dental plaque
were taken from mother and child and seeded in selective Agar
Mitis Salivarius Bacitracin medium (0.28 mg/ml) and cultured
for 48 hours at 37ºC and in 5% CO2 to allow for the growth of
Streptococcus mutans. The colonies were identified morphologically and biochemically.
At 6 months after childbirth: 58.33% of the samples of the
mother’s saliva were positive, while the presence of the
microorganism was not detected in 100% of the samples of the
infants’ saliva.
At 18 months of after childbirth: 79.16% of the samples of saliva and 100% of the samples of the mothers’ dental plaque were
positive, whereas the samples of saliva and dental plaque of
the infants were positive for Streptococcus mutans in 20.83%
and 70.83% of the cases respectively.
The initial acquisition of Streptococcus mutans would have
occurred in 20.8% of the children at the age of 18 months.
Eruption of primary molars occurs at this age.
Key words: Streptococcus mutans, binomial mother-child,
transmission, acquisition.
ADQUISICIÓN TEMPRANA DE STREPTOCOCCUS MUTANS POR INFANTES
RESUMEN
Existen evidencias de que en la infección oral temprana la principal vía de transmisión de Streptococcus mutans es a través del
contacto salival madre-niño y que la adquisición inicial tiene lugar
durante un período específico de tiempo denominado “Ventana
de Infectividad”, que transcurre entre los 6 y 30 meses de vida del
niño, existiendo mayor riesgo entre los 18 y 30 meses de edad.
Con el propósito de investigar la Infección Oral Temprana se
evaluó la presencia de Streptococcus del grupo mutans en saliva y placa dental en el binomio madre-niño entre los 6 y 18
meses después del nacimiento.
En este estudio participaron 24 binomios (madre-niño) que
concurrieron al Hospital Universitario de Maternidad y Neonatología de Córdoba. Se procedió a tomar muestras de saliva
total y placa dental de la madre y el niño a los 6 y 18 meses
después del nacimiento, las que fueron sembradas en el medio
selectivo Agar Mitis Salivarius Bacitracin (0,28 mg/ml) durante 48 horas a 37ºC y 5% CO2 para el crecimiento de
Streptococcus del grupo mutans, las colonias se identificaron
morfológica y bioquimicamente.
A los 6 meses del nacimiento del niño: el 58,33% de las muestras de saliva de la madre resultaron positivas, mientras que
en el 100% de las muestras de saliva del infante no se detectó
la presencia del microorganismo.
A los 18 meses del nacimiento del niño: el 79,16% de las muestras de saliva y el 100% de las muestras de placa dental de las
madres fueron positivas, en tanto que las muestras de saliva y
placa dental del infante resultaron positivas para Streptococcus del grupo mutans en un 20,83% y 70,83% respectivamente.
La adquisición inicial de Streptococcus del grupo mutans
habría ocurrido en el 20,8% de niños a los 18 meses de la edad,
lo que coincide particularmente con la erupción de los molares temporarios.
INTRODUCTION
Birth is the first environmental event that conditions the allogeneic succession in the oral cavity. In
the uterus, the fetus is free from microorganisms
and up to 8 hours after birth the mouth remains ster-
ile. Oral colonization begins when the baby passes
through the birth canal and by interaction with the
outside world. During the first stages of colonization it is possible to detect staphylococci,
enterobacteria, neisseria, yeast, and Streptococcus,
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Palabras clave: Streptococcus mutans, binomio madre-niño,
transmisión, adquisición.
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PÆgina 70
F. P. M. Carletto Körber, L. S. Cornejo, M. G. Giménez
in particular of the viridans group, and more specifically Streptococcus mitis and salivarius that mainly
colonize oral mucosa. The growth and development
of the oral microbiota of infants follows the pattern
of ecological succession described for other ecosystems. Tooth eruption triggers significant ecological
changes in the oral cavity. This physiological event
creates appropriate conditions for the development
of new species of microorganisms that must adhere
to hard surfaces to colonize. Among these microorganisms, the presence of Streptococci of the mutans
group, i.e. Streptococcus mutans (SM) and Streptococcus sobrinus (SS), is necessary but not sufficient
for the development of dental caries (1, 2).
In recent years several studies have been performed
to determine “from whom”, “when” and “how” initial acquisition of Streptococcus mutans occurs.
Regarding early childhood caries, Berkowitz (3)
supports the notion that scientific evidence has
demonstrated that it is an infectious and transmissible disease, characterized by a “three phase model”.
The first phase involves infection by mutans streptococci, the second consists of an increase in the
population in the biofilm as a result of prolonged
exposure of the oral cavity to a cariogenic substrate,
and the third corresponds to rapid demineralization
and cavitation of tooth enamel.
Slavkin (4) describes the source of infection and
mode of transmission as an interesting paradox. The
mother can transmit infectious microorganisms to
the infant by intimate contact and can also transmit
the antibodies that protect the infant from different
microorganisms by breast-feeding. This author also
states that the mother’s oral health status might be a
health risk factor for the fetus or the newborn.
Similarly, Caufield, Cutter and Dasanayake (5) suggested a direct association between the levels of
mutans streptococci in mothers and their children
and pointed out that the prevalence of SM acquisition increases with the child’s age and with the
number of erupted teeth.
The existing evidence suggests that the main SM transmission route in Early Oral Infection is the saliva
contacts between mother and child and that initial
acquisition occurs during a specific period of time
termed “Window of Infectivity” that coincides with
tooth eruption and spans the 6-30 month old age period, with a higher risk between 18 and 30 months of age
(5, 6, 7). Mohan et al. (8) found that 20% of children
under the age of 14 months were infected with SM.
The present study involved the evaluation of the
levels of SM and SS in the binomial mother-child
at 6 and 18 months after childbirth.
MATERIALS AND METHODS
Population and study design
The population under study was a group of pregnant women in their last trimester of gestation that
attended the University Hospital of Maternity and
Neonatology of Córdoba (9, 10). The concentration
of fluoride in the drinking water in the city of Córdoba ranges, according to the neighborhood, from
0.6 to 1.0 ppm.
The study group was comprised of 24 mother-child
binomials. Saliva samples were taken at 6 months
after childbirth and saliva and dental plaque samples were taken at 18 months after childbirth.
Informed consent was obtained from all the participating mothers (11).
Clinical odontological examination
The infants were examined clinically at 6 and 18
months of age in their homes under good natural
light. The number of erupted teeth was recorded and
the mother was asked to describe the child’s history
of tooth eruption (12).
Study of saliva and dental plaque samples of
the mother-child binomial
Sample obtention
Samples of non-stimulated saliva of the motherchild binomial 6 and 18 months after childbirth were
taken in the morning, 30 minutes after the last meal.
The mother’s sample was collected by direct salivation for 5 min in a sterile, calibrated container.
The infant’s sample was collected from the floor of
the mouth with a pipette.
The saliva samples were stored at -20ºC until processing.
The dental plaque samples of mother and child were
collected 18 months after childbirth from the
vestibular, occlusal, lingual or palatine dental surfaces with sterile cotton swabs.
The dental plaque samples were placed in Brain
Heart Broth and stored in the fridge until processing.
Isolation and Typification of Streptococcus
mutans from the mother-child binomial
The saliva and dental plaque samples of the mother-child binomials were seeded in Agar Mitis
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Early acquisition of Streptococcus mutans
Salivarius (DIFCO) medium additioned with 0.281
mg/mL of Bacitracin (ICN Biomedicals, 71% activity) and incubated at 37ºC under microaerophilic
conditions. The morphological analysis of the
colonies was performed by Gram staining and light
microscopy analysis. Typification was performed
by biochemical assays employing the commercial
kit Api 20 Strep (bioMérieux) in keeping with the
instructions of the manufacturer. The kit is ideally
suited to distinguish between most of the Streptococci relevant to medical bacteriology and
distinguishes between SM and SS (13, 14).
The levels of CFU/mL in saliva and plaque were
classified as high and low risk according to the criteria of Jensen and Bratthall (15) and Bordoni (16).
RESULTS
Clinical odontological examination
The families were visited at their homes 6 and 18
months after childbirth and the mother was asked
to provide information on the child’s history of
tooth eruption. The mean age of eruption of the
lower incisors was 8 months (±2 months).
Analysis of saliva and dental plaque in the
mother-child binomials
Six months after childbirth 58.33% of the mothers’
saliva samples were positive for SM. Of these samples, 45.83% had ≥105 CFU/mL SM (high risk level)
and 12.5% had <105 CFU/mL SM (low risk level).
The presence of the microorganism was not detected
in 100% of the saliva samples of the infants (Figure 1).
At 18 months after childbirth 79.16% of the saliva
samples of the mothers were positive for SM.
54.16% of the samples had high risk counts and
25% had low risk counts.
100% of the dental plaque samples of the mothers
tested positive. 37.5% of the samples had -20.000
CFU/mL (low risk level) and 62.5% had +20.000
CFU/mL (high risk level); 54.16% were positive for
SM and 8.33% were positive for SS.
The saliva samples of the infants at 18 months of
age were positive for SM in 20.83% of the cases.
12.5% of the samples had ≥105 CFU/mL. The dental plaque samples tested positive with +20.000
CFU/mL in 70.83% of the cases. 50% were positive
for SM and 8.33% were positive for SS (Figure 1).
Figure 2 shows that at 6 months after childbirth the
saliva samples of all the infants corresponding to
SM positive mothers tested negative.
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71
100
90
80
20,83
70
25
60
50
29,16
37,5
41,66
12,5
79,17
12,5
100
40
20
62,5
54,16
30
58,33
45,83
8,33
10
12,5
0
Mother
Child
Mother
Saliva
6 months
Child
Saliva
Mother
Child
Plaque
18 months
≥105 CFU/mL SM in saliva / +20.000 CFU/mL SM in plaque
<105 CFU/mL SM in saliva / -20.000 CFU/mL SM in plaque
neg. in saliva and plaque
Fig. 1. Streptococcus mutans in saliva and dental plaque of
the binomials at 6 and 18 months after childbirth.
Figure 3 shows the levels of SM CFU/mL in the
saliva of mothers and infants at 18 months after
childbirth. 38.46% of the children of high risk
mothers tested positive whereas all the children of
mothers with <105 UFC/mL SM tested negative.
The evaluation of levels of SS and SM in dental
plaque of the mother-child binomials at 18 months
after childbirth (Figure 4) revealed that 62.5% of
the mothers had +20.000 UFC/mL (high risk level)
and 37.5% had -20.000 UFC/mL (low risk level).
The infants of high risk mothers were positive in
66.66% of the cases. 53.33% of these infants had
high risk counts and 13.33% had low risk counts.
66.66% of the infants of low risk mothers had high
risk counts and 11.11% had low risk counts.
DISCUSSION
The acquisition of microorganisms by the body can
occur by direct transmission from a host or indirectly via another living organism. Inanimate objects,
food and water can also transmit pathogens (17).
Saliva is considered the major vehicle of transmission of SM by physical contact (18, 19). The mother
is considered the main source of infection for the
child. An association between the time at which
most children acquire SM in their oral flora and primary dental eruption at 8 months to 3 years of age
has been described (5).
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100
100
80
80
60
60
100
100
40
40
20
20
0
100
100
Mother
Child
0
Mother
Child
≥105 CFU/mL SM
<105 CFU/mL SM
neg.
Fig. 2. Streptococcus mutans in saliva of the binomials at 6 months after childbirth.
100
100
80
80
61,54
60
60
100
100
100
40
40
15,38
20
20
23,07
0
0
Mother
Child
Mother
<105 CFU/mL SM
≥105 CFU/mL SM
Child
neg.
Fig. 3. Streptococcus mutans in saliva of the binomials at 18 months after childbirth.
100
100
80
33,34
60
13,33
22,23
80
11,11
60
100
100
40
40
66,66
53,33
20
20
0
0
Mother
Child
Mother
+20.000 CFU/mL SM
-20.000 CFU/mL SM
Child
neg.
Fig. 4: Streptococcus mutans in dental plaque of the binomials at 18 months after childbirth.
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Early acquisition of Streptococcus mutans
The present study revealed that eruption of the first
tooth took place approximately at 8 months (± 2
months) of age in keeping with Kreiborg (20). Initial colonization by SM occurred at 18 months of
age in 20.8% of the infants.
The primary habitat of SM and SS is human dentition. Once these microorganisms have colonized
dentition they are found in saliva, the tongue, oral
mucous membranes, etc. (21).
According to Costerton and Lewandowski (22), the
biofilm establishes a dynamic link between the dental surfaces and the different components in the
saliva and the microorganisms in the oral flora that
live in symbiosis and antibiosis.
The prevalence of SM infection in the binomials was
markedly higher than SS prevalence (97.66% and 8.33%
respectively). A noteworthy finding was the absence of
SS in the saliva of the binomials at 6 and 18 months after
childbirth whereas SS was isolated from dental plaque
of the binomials at 18 months after childbirth.
Lindquist (23) reported differences in the dentition
colonization pattern between SM and SS, i.e. SS is
more frequently isolated from the posterior surface
of teeth. When both SM and SS are present they colonize oral surfaces equally but SM is prevalent on
all other surfaces.
Within the context of initial acquisition, Masuda
and Berkowitz (24, 25) detected SM colonies in
40% of the children at 24 months of age and in 29%
of the children at 8 to 18 months of age.
The present study of 24 mother-child binomials
from 6 to 18 months after childbirth revealed that
initial acquisition would have occurred in 20.8% of
the infants at 18 months of age. These data are in
keeping with Caufield (5) who studied 46 motherchild binomials from birth to 5 years after childbirth
and reported that initial acquisition of SM occurred
at 19 months of age in 25% of the infants and at 31
months in 75% of the infants.
Similarly, Karn et al. (26) also demonstrated the
presence of SM at a very early age, i.e. in 25% of
the infants before one year of age and in 60% of the
infants at 15 months of age.
Milgrom et al. (27) evaluated 199 children from 6
to 36 months of age and detected the presence of
SM in 25% of the infants before dental eruption and
in 53% of the infants from 6 to 12 months of age.
Early initial acquisition has become particularly relevant as a predictive marker of future caries activity
in primary and permanent dentition.
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In the 80’s, Köhler et al. (28) among others had
already demonstrated that early detection of SM
was associated to caries experience.
Caufield, Cutter and Dasanayake (5) provided evidence that supports the association between the
presence of mutans streptococci in mother and
child’s saliva.
Our results suggest that the risk of infection would
be more closely related to the CFU/mL of mutans
streptococci present in the dental plaque of the
mother than in her saliva.
In terms of the source of infection, our data showed
that at 18 months after childbirth, 38.46% of the
infants of mothers with high risk values of CFU/mL
of SM exhibited SM positive saliva. The dental
plaque of 66.66% of the infants of mothers with
high risk dental plaque (+20.000 UFC/mL) and of
77.77% of the infants of mothers with low risk dental plaque (-20.000 UFC/mL) were positive for
mutans streptococci. The high percentage of colonization by SM in infants of mothers with low risk
plaque suggests the existence of other sources of
infection within the family and/or the contribution
of other factors involved in colonization such as
family eating and oral hygiene habits.
Klemonskis et al. (29) analyzed biological risk factors,
life style and social environment of mother-child binomials in two communities. Their results showed that 15
months after childbirth there were no statistically significant differences in the level of mutans streptococci
infection between the mothers in both groups. However, statistically significant differences were found in the
level of infection between the infants in both groups.
The Window of Infectivity could be associated to
family eating habits. The eating habits of the
infants are associated to those of their mothers.
Furthermore, early eating habits condition future
patterns of eating behavior. According to Alaluusua
(30), another requirement for early colonization is
that the child should frequently eat refined carbohydrates.
Mohan et al. (8) reported that 20% of the children
under 14 months of age exhibited SM infection and
suggested that the risk of SM colonization is lower
in infants who feed on milk rather than on sweetened beverages.
Although the influence of the mother’s level of
infection in early colonization is important, other
factors that would participate in initial colonization
should also be considered.
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CONCLUSION
Based on our results we may conclude that:
Initial colonization by mutans streptococci in the
binomials under study occurred in 20.8% of the
infants at 18 months of age, concomitantly with the
age of temporary molar eruption.
The high incidence of infection by mutans streptococci in children of mothers with high and low risk
dental plaque suggests the influence of other factors that favor early colonization.
ACKNOWLEDGEMENT
The authors wish to express their gratitude to Consulting professor Dr. José Sabino Trezza of the first Department of Clinical
Obstetrics and Perinatology and to Dr. Graciela Quiroga, Head
of the Service of Odontology of the University Hospital of
Maternity and Neonatology for granting permission to perform
this study. The authors gratefully acknowledge Biol. Mabel
Brunotto for performing the statistical analysis of the data.
CORRESPONDENCE
Od. Fabiana Carletto Körber
Cátedra de Integral Niños y Adolescentes, área Odontopediatría
“A”, Facultad de Odontología. Universidad Nacional de Córdoba
Haya de la Torre s/n. Ciudad Universitaria.
(5000) Córdoba. Argentina
[email protected]
[email protected]
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early acquisition of streptococcus mutans for children

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