presentation about lactobaciili Lactobaciili and its impact in oral cavity clinical and laboratory presentation

1. LACTOBACILLI and oral
cavity
Done by : Marwan R. jasim
Dep. Of microbiology
College of dentistry
University of mousal

2. Table in contents
 Definition and characteristic
 Habitat and transmission
 Classification
 Taxonomy
 Culture and identification
 Ecology of Human Lactobacilli in the oral cavity
 Lactobacilli in Saliva
 Lactobacilli in Dental Plaque
 Lactobacilli in Carious Lesions
 Influence of Lactobacilli on Oral Health

3. LACTOBACILLI
Definition and characteristic
 Lactobacilli are saprophytes in vegetable and animal material (e.g. milk).
Some species are common animal and human commensals inhabiting
the oral cavity and other parts of the body.
 They have the ability to tolerate acidic environments and hence are
believed to be associated with the carious process.
 Lactobacillus is a large group of bacteria made up of several species and
named for their ability to convert sugars into lactic acid. Lactobacillus
bacteria are commonly found in the human gastro-intestinal tract, and
certain types are used for the commercial production of fermented foods
like cheese, yogurt, pickles and wine.

4. CHARACTERISTICS
 is a genus of Gram-positive facultative anaerobic or micro aerophilic
 rod-shaped bacteria
 In humans they are present in the vagina and the gastrointestinal tract,
where they make up a small portion of the gut flora.
 They are usually benign, except in the mouth where they have been
associated with cavities and tooth decay
 facultative anaerobes. These organisms ferment carbohydrates to form
acids (acidogenic) and can survive well in acidic milieu (aciduric); they
may be homofermentative or heterofermentative.

5. LACTOBACILLI
Electronic microscope show a light microscope show a lactobacilli
Lactobacilli rods rods

6. Habitat and transmission
 Lactobacilli are found in the oral cavity, gastrointestinal tract and female
genital tract.
 In the oral cavity they constitute less than I% of the total flora.
Transmission routes are unknown

7. Classification
 Phylum: Fimicutes
 Class: Bacilli
 Order: Lactobacillae
 Family: Lactobacillales
 Genus: Lactobacillus

8. The taxonomy
The taxonomy of lactobacilli is complex. They are characterized into
two main groups:
 homofermenters, which produce mainly lactic acid (65%) from glucose
fermentation (e.g. Lactobacillus casei),
 Heterofermenters, which produce lactic acid as well as acetate, ethanol
and carbon dioxide (e.g. L. fermentum).
L. casei and L. rhamnosus, L. acidophilus and the newly described
species, L. oris, are common in the oral cavity.

9. Culture and identification
 Lactobacilli grow under micro aerophilic conditions in the presence CO2
and at acidic pH (6.0).
 Media enriched with glucose or blood promote growth.
 A special selective medium, tomato juice agar (pH 5.0), promotes the
growth of lactobacilli while suppressing other bacteria.
 Identification is by biochemical reactions
 Often abbreviated to MRS, this type of bacterial growth
Man, Rogosa and Sharpe. Developed in 1960, this was medium is so-
named by its inventors: de designed to favour the luxuriant growth
of Lactobacilli for lab study. It contains sodium acetate, which
suppresses the growth of many competing bacteria (although some
other Lactobacillales, like Leuconostoc andPediococcus, may grow).
This medium has a clear brown colour

10. culturing
 Principle
Lactobacilli MRS medium is based on the formulation of deMan, Rogosa
and Sharpe with slight modification. It supports
luxuriant growth of all Lactobacilli from oral cavity (1), dairy products (2),
foods (3), faeces (4) and other sources

11. MRS media
Culture media Selective isolation Lactobacilli MRS
agar Lactobacillus species appear as small, white,
creamy colonies.

12. Test Procedure
 1. To obtain direct counts of lactobacilli, pour 15 - 20 mL sterile, molten
(45 - 50°C) Lactobacilli MRS Agar
 into sterile petri dishes containing 1 mL volumes of diluted test sample.
 2. Distribute inoculum throughout medium by rotating the plate in one
direction, then in the reverse direction.
 3. Allow medium to solidify on a flat surface for 5 - 10 minutes.
 4. Alternatively, plates of Lactobacilli MRS Agar can be used for direct
recovery of organisms using the streak inoculation technique.
 5. Incubate agar plates at 35°C for 3 days, or at 30°C for 5 days in an
aerobic atmosphere supplemented with carbon dioxide.

13. Lactobacilli acidophilus

14. Lactobacilli casei

15. Lactobacillus fermentum

16. Result
 Microorganisms Growth
 Lactobacillus acidophilus Good
 Lactobacillus casei Good
 Escherichia coli Moderate-Good
 Ps eudomonas aeruginosa Inhibited
 Lactobacilli appear as large, white colonies embedded in or on Lactobacilli
MRS Agar. Growth can be
 Sub cultured onto appropriate media for use in additional procedures.
Refer to appropriate references for
 recommendation on the identification of Lactobacillus spp.

17. Ecology of Human Lactobacilli in the
oral cavity
 Historically, lactobacilli were the first microorganisms implicated in
dental caries development due to
1. They appear during the first years of a child’s life
2. and are present in high numbers in saliva, on the dorsum of the tongue,
mucous membranes, the hard palate, in dental plaque and, in fewer
numbers, on tooth surfaces
 The presence of lactobacilli in the oral cavity depends on numerous
factors such as the presence of ecological niches e.g. the teeth partly
erupted third molars or orthodontic devices

18. Lactobacilli in Saliva
 The Lactobacillus count represents the number of lactobacilli
present in 1ml of saliva (CFU/ml)
 It is used to evaluate the carious risk
 It is used alone or associated with other parameters
 it is a better criterion than the saliva rate Streptococus mutans
 A strong correlation has been established between the Lactobacillus
counted caries,

19. Lactobacilli in Dental Plaque
 Dental plaque is a thin film in thickness, forming on tooth surface contain
numerous type of bacteria which are represent the normal oral flora
commensals
 It is difficult, from the literature, to have an exact idea of The relationship
between lactobacilli and dental plaque Whether on the quantitative level
or on the qualitative level
 the numerous studies were carried out on different Populations (age,
DMF index, fluoride intake). Moreover, The sampling methods were also
very varied

20. Lactobacilli in Carious Lesions
 The microbial populations involved in dental caries are known to be
highly complex and variable and have not yet been fully identified
 Among children, the presence of lactobacilli in coronal caries is
incontestable
 they are found in less quantity than Streptococcus mutans and they are
not found in incipient caries
 The presence of these microorganisms is also dependent on the size of
the cavity: they are more numerous in medium and large cavities

21. Influence of Lactobacilli on Oral
Health
 In some cases, lactobacilli could also play a beneficial role by inhibiting
the growth of some cariogenic bacteria(S. mutans)
 Michalek et al found that
 L. casei, if present in plaque, may reduce S. mutans- induced dental caries
in gnobiotic rats
 Another effect is the inhibition of adherence, a major cariogenic factor of
S. mutans
 L. fermentum and its culture supernatant inhibit the production of water
insoluble glucan by S. mutans
 The growth of S.mutans is not inhibited but its in vitro adherence is totally
inhibited