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Lactobacillus characterization and effects on oral biofilm composition
Umeå University, Faculty of Medicine, Department of Odontology.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The human body is home for millions of bacteria. The largest microbial community is located in the gastro-intestinal (GI) tract, including the oral cavity with >700 identified taxa. Lactobacillus, which is normal inhabitant of the GI tract, contributes to health by possible biofilm and immune modulation. Breast milk is a claimed source for transmittance of Lactobacillus to infants’ GI tract, but there is limited information if breastfeeding affects lactobacilli in the oral cavity. The objectives of Papers I and II of this dissertation were to compare infant oral microbiota by feeding mode, and to characterize oral lactobacilli including potential probiotic properties of the dominant Lactobacillus species.

Two cohorts with a total of 340 healthy 3- to 4-month-old infants were investigated. Saliva and oral mucosal swab samples were collected. Bacteria were characterized by culture-dependent and -independent methods, including 16S rRNA genes sequencing, quantitative PCR, and the Human Microbe Identification Microarray (HOMIM). Inhibition of growth and adhesion were also tested.

Multivariate modeling of HOMIM-detected oral bacteria clustered breastfed infants separately from formula-fed infants, and linked breastfed infants to a more health-associated flora. Lactobacilli were essentially detected in breastfed infants only. Lactobacillus gasseri was most prevalent out of six identified Lactobacillus species. Infant isolates of L. gasseri bound to saliva gp340 and MUC7 and adhered to gingival epithelial cells. Infant isolates also inhibited adhesion of Streptococcus mutans to saliva-coated hydroxyapatite, and inhibited growth of S. mutans, Streptococcus sobrinus, Actinomyces naeslundii, Actinomyces oris, Candida albicans and Fusobacterium nucleatum in a concentration-dependent fashion.

Papers III and IV aimed to assess persistence of probiotic Lactobacillus reuteri, if persistence is necessary for a regrowth of mutans streptococci (MS), and if L. reuteri intake affects oral microbiota composition.

Two well-documented L. reuteri strains (DSM 17938 and PTA 5289) were used in two double-blind, randomized controlled trials. In the first, 62 subjects (test=32, placebo=30) with high counts of MS were exposed to L. reuteri for 6 weeks. Exposure followed full-mouth disinfection with chlorhexidine. In the second study, 44 healthy subjects (test=22, placebo=22) consumed the L. reuteri for 12 weeks. Saliva and biofilm samples were collected before, during and up to 6 months after exposure. Analyses included culture, strain-specific PCR and 454-pyrosequencing targeting the hypervariable region V3-V4 of the 16S rRNA gene.

L. reuteri test strains were detected in the mouth of approximately two thirds of test participants during intake. However, their presence decreased gradually when consumption stopped. Subjects with detectable L. reuteri had slower regrowth of MS compared to non-carriers.

Pyrosequencing yielded a total of 812,547 high-quality sequencing reads. Firmicutes, Proteobacteria, Bacteroidetes, Fusobacteria and Actinobacteria were the major bacterial phyla recovered. Exposure to L. reuteri strains did not affect overall phylotype abundance, but multivariate modeling clustered 12-week-treated test subjects separately from those who received placebo. Exposure to the test strains was strongly associated with presence and increased levels of F. nucleatum and Streptococcus spp.

In conclusion, the oral microbiota differed by feeding mode in infants. One third of breastfed infants had lactobacilli in the mouth, while only single formula-fed infant had it. L. gasseri, predominant in infants, displayed probiotic characteristics in vitro. Retention of probiotic L. reuteri was a prerequisite for delay of MS regrowth after disinfection. However, probiotic bacteria may not be beneficial for all, since L. reuteri DSM 17938 and PTA 5289 were retained in only 2 of 3 consumers. Finally, the altered microbiota after 12 weeks consumption of L. reuteri indicates that intake of probiotic bacteria, or at least L reuteri, has an impact on oral ecology. However, this finding needs further investigation.

Abstract [sv]

Vår kropp består av fler mikroorganismer än egna celler.  De miljontals bakterier som finns på ut - och insidan av kroppen är som regel harmlösa och vissa är till och med till nytta för oss. Magtarmkanalen, som startar med munnen, är den kroppsdel som härbärgerar flest bakterier. Till exempel har man bara i munnen identifierat totalt mer än 700 olika arter. En av dessa är Lactobacillus, en bakterieart som finns i normalfloran och som har probiotiska egenskaper. Hos spädbarn anses bröstmjölk vara en källa för Lactobacillus i tarmen, men hur amning påverkar laktobacillförekomst i munnen är oklart.

Den första delen i denna avhandling syftar till att jämföra mikrofloran i munnen hos spädbarn som ammas kontra de som får ersättning, att karakterisera vilka laktobaciller som finns i munnen hos respektive grupp och undersöka om dessa har probiotiska egenskaper. Totalt studerades saliv och prov från munslemhinnan från 340 friska 3-4 månader gamla spädbarn. Proven karakteriserades med odling, sekvensering, kvantitativ PCR och en microarraymetod (Human Microbe Identification Microarray, HOMIM), och isolerade laktobacillers effekt på växt och vidhäftning av andra munbakterier studerades. Ammade barn hade en mer hälsoassocierad mikroflora i munnen. Laktobaciller fanns bara hos ammade barn, men bara hos vart 3:e ammat barn. Av totalt sex identifierade laktobacillarter var Lactobacillus gasseri den i särklass mest förekommande arten. L. gasseri isolerade från spädbarnen band till salivproteinerna gp-340 och MUC7 samt till orala epitelceller. L. gasseri kunde även förhindra adhesion av Streptococcus mutans till konstgjord tandemalj och hämma växt av S. mutans, Streptococcus sobrinus, Actinomyces naeslundii, Actinomyces oris, Candida albicans och Fusobacterium nucleatum.

Laktobaciller förekommer i många hälsoprodukter med påstådd probiotisk effekt. Andra delen av denna avhandling syftade till att bedöma om intag av tabletter med den probiotiska arten Lactobacillus reuteri påverkar ekologin i mikrofloran i munnen, om arten etablerar sig hos alla vid exponering, och om etablering är nödvändig för probiotisk effekt (mätt som hämmad återväxt av kariesassocierade mutansstreptokocker efter antimikrobiell behandling). Två stammar L. reuteri (DSM 17938 and PTA 5289) användes i två dubbelblinda, randomiserade studier. I båda studierna intog deltagarna i testgruppen tabletter med L. reuteri-stammarna och de i kontrollgruppen identiska tabletter utan bakterier. I den första studien deltog 62 deltagare (32 test, 30 kontroll) i 6 veckor och i den andra 44 personer (22 test, 22 placebo) under 12 veckor. Saliv och biofilmsprover samlades in vid studiestart, under och upp till 6 månader efter avslutad testperiod. Proverna analyserades med odling, PCR och 454-pyrosekvensering. L. reuteri etablerade sig hos 2/3 av testpersonerna under testperioden men mängden minskade gradvis efter avslutat intag. Bland de som fick L. reuteri hade deltagarna med påvisbara teststammar fördröjd återväxt av mutansstreptokocker jämfört med de som inte hade det. Pyrosekvensering visade att totalantalet phylotyper inte skiljde sig mellan de som fick aktiva kontra placebotabletter, men att ekologin i bakteriefilmerna hos de som ätit de aktiva tabletterna ändrades. Att exponeras för L. reuteri var starkt associerat med förhöjda nivåer av F. nucleatum and Streptococcus spp.

Sammanfattningsvis visar dessa studier att amning är associerad med att ha probiotiska laktobaciller i munnen men bara vissa etablerar arten i munnen. Hos vuxna försenade L. reuteri återkolonisation av mutansstreptokocker efter antibakteriell behandling, och påverkade ekologin i bakteriefilmerna i munnen. Även hos vuxna ledde exponering till etablering bara hos vissa individer.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet , 2013. , 65 p.
Umeå University odontological dissertations, ISSN 0345-7532 ; 128
Keyword [en]
Lactobacillus, L. gasseri, probiotic traits, oral biofilm, breastfeeding, oral microbiota
National Category
Research subject
URN: urn:nbn:se:umu:diva-82412ISBN: 978-91-7459-745-5OAI: diva2:664445
Public defence
2013-12-13, Sal B, plan 9, Tandläkarhögskolan, Norrlands Universitetssjukhus, Umeå, 09:15 (English)
Available from: 2013-11-22 Created: 2013-10-31 Last updated: 2013-11-22Bibliographically approved
List of papers
1. Oral microbial profile discriminates breast-fed from formula-fed infants
Open this publication in new window or tab >>Oral microbial profile discriminates breast-fed from formula-fed infants
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2013 (English)In: Journal of Pediatric Gastroenterology and Nutrition - JPGN, ISSN 0277-2116, E-ISSN 1536-4801, Vol. 56, no 2, 127-136 p.Article in journal (Refereed) Published
Abstract [en]

Objectives: Little is known about the effect of diet on the oral microbiota of infants, although diet is known to affect the gut microbiota. The aims of the present study were to compare the oral microbiota in breast-fed and formula-fed infants, and investigate growth inhibition of streptococci by infant-isolated lactobacilli.

Methods: A total of 207 mothers consented to participation of their 3-month-old infants. A total of 146 (70.5%) infants were exclusively and 38 (18.4%) partially breast-fed, and 23 (11.1%) were exclusively formula-fed. Saliva from all of their infants was cultured for Lactobacillus species, with isolate identifications from 21 infants. Lactobacillus isolates were tested for their ability to suppress Streptococcus mutans and S sanguinis. Oral swabs from 73 infants were analysed by the Human Oral Microbe Identification Microarray (HOMIM) and by quantitative polymerase chain reaction for Lactobacillus gasseri.

Results: Lactobacilli were cultured from 27.8% of exclusively and partially breast-fed infants, but not from formula-fed infants. The prevalence of 14 HOMIM-detected taxa, and total salivary lactobacilli counts differed by feeding method. Multivariate modelling of HOMIM-detected bacteria and possible confounders clustered samples from breast-fed infants separately from formula-fed infants. The microbiota of breast-fed infants differed based on vaginal or C-section delivery. Isolates of L plantarum, L gasseri, and L vaginalis inhibited growth of the cariogenic S mutans and the commensal S sanguinis: L plantarum >L gasseri >L vaginalis.

Conclusions: The microbiota of the mouth differs between 3-month-old breast-fed and formula-fed infants. Possible mechanisms for microbial differences observed include species suppression by lactobacilli indigenous to breast milk.

breast-feeding, lactobacilli. Lactobacillus gasseri, microbiota, oral
National Category
urn:nbn:se:umu:diva-66787 (URN)10.1097/MPG.0b013e31826f2bc6 (DOI)000314099600011 ()
Available from: 2013-03-11 Created: 2013-03-05 Last updated: 2013-11-22Bibliographically approved
2. Characterization and in vitro properties of oral lactobacilli in breastfed infants
Open this publication in new window or tab >>Characterization and in vitro properties of oral lactobacilli in breastfed infants
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2013 (English)In: BMC Microbiology, ISSN 1471-2180, Vol. 13, 193- p.Article in journal (Refereed) Published
Abstract [en]

Background: Lactobacillus species can contribute positively to general and oral health and are frequently acquired by breastfeeding in infancy. The present study aimed to identify oral lactobacilli in breast and formula-fed 4 month-old infants and to evaluate potential probiotic properties of the dominant Lactobacillus species detected. Saliva and oral swab samples were collected from 133 infants who were enrolled in a longitudinal study (n=240) examining the effect of a new infant formula on child growth and development. Saliva was cultured and Lactobacillus isolates were identified from 16S rRNA gene sequences. Five L. gasseri isolates that differed in 16S rRNA sequence were tested for their ability to inhibit growth of selected oral bacteria and for adhesion to oral tissues. Oral swab samples were analyzed by qPCR for Lactobacillus gasseri.

Results: 43 (32.3%) infants were breastfed and 90 (67.7%) were formula-fed with either a standard formula (43 out of 90) or formula supplemented with a milk fat globule membrane (MFGM) fraction (47 out of 90). Lactobacilli were cultured from saliva of 34.1% breastfed infants, but only in 4.7% of the standard and 9.3% of the MFGM supplemented formula-fed infants. L. gasseri was the most prevalent (88% of Lactobacillus positive infants) of six Lactobacillus species detected. L. gasseri isolates inhibited Streptococcus mutans binding to saliva-coated hydroxyapatite, and inhibited growth of S. mutans, Streptococcus sobrinus, Actinomyces naeslundii, Actinomyces oris, Candida albicans and Fusobacterium nucleatum in a concentration dependent fashion. L. gasseri isolates bound to parotid and submandibular saliva, salivary gp340 and MUC7, and purified MFGM, and adhered to epithelial cells. L. gasseri was detected by qPCR in 29.7% of the oral swabs. Breastfed infants had significantly higher mean DNA levels of L. gasseri (2.14 pg/uL) than infants fed the standard (0.363 pg/uL) or MFGM (0.697 pg/uL) formula.

Conclusions: Lactobacilli colonized the oral cavity of breastfed infants significantly more frequently than formulafed infants. The dominant Lactobacillus was L. gasseri, which was detected at higher levels in breastfed than formula-fed infants and displayed probiotic traits in vitro.

Place, publisher, year, edition, pages
BioMed Central, 2013
Lactobacillus, L.gasseri, Growth, Adhesion, Gp340, Breastfed infants
National Category
Pediatrics Dentistry
urn:nbn:se:umu:diva-80436 (URN)10.1186/1471-2180-13-193 (DOI)000323427400001 ()
Available from: 2013-09-20 Created: 2013-09-17 Last updated: 2014-04-25Bibliographically approved
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4. 454 pyrosequencing characterization of the oral microbiota after 12-week supplementation with lactobacillus reuteri DSM 17938 and PTA 5289
Open this publication in new window or tab >>454 pyrosequencing characterization of the oral microbiota after 12-week supplementation with lactobacillus reuteri DSM 17938 and PTA 5289
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(English)Manuscript (preprint) (Other academic)
National Category
urn:nbn:se:umu:diva-82415 (URN)
Available from: 2013-10-31 Created: 2013-10-31 Last updated: 2013-11-22Bibliographically approved

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