normal flora

Normal Flora

Flora – microorganisms that are usually found associated with healthy body tissue
Advantages of normal floura
1-protection against pathogen germs
2-acid production (stomach, vagina)
3-metabolism (vitamin B and K, Enzymes)
4-stimulation of the immunsystem

* The normal flora in the mouth.

streptococci, staphylococci, neisseria, haemophilus, corynebacteria, yeats, anaerobic bacteria e.g. fusobacteria, bacteroides
The mucosa membranes of the mouth and pharynx are ofthen sterile at birth but may be contaminated by passage through the birth canal
Within 4-12 hours ofthen birth viridians streptococcus become established as the most prominent members of the resident floura and remain so for life
Early in life aerobic and anaerobic staphylococci ,gram negative diplococcic (neisseri )diphtherioids and lactobacilli are added
when teeth begin to erupt the anaerobic spirochetes bacterioide especially b.melaninogenicus,fusobacteria and some anaerobic vibrios and lactobacilli establish themselves
Actinomyces species are normaly present in tonsilar tissue on the gingva in adults
Yeasts (candida albicans) occur in the mouth

Gram-positive cocci

Genus Streptococcus
Gram-positive cocci in chains, non-motile, occasionally capsulate; facultative anaerobes;
variable haemolysis but a-haemolysis most common;

mutans group

Main species:
1-Streptococcus mutans serotypes c e f·
2- S. sobrinus serotypes d, g;
3- S. cricetus serotype a;
4-S. ratus; serotype b.
salivarius group
• Main species:
Streptococcus salivarius;
S. Vestibularis

anginosus group

Main species:
Streptococcus constellatus;
S. intermedius;
S. anginosus
mitis group
• Main species:
Streptococcus mitis;
S. sanguis; S. gordonii;
S. oralis; S. crista.
Anaerobic streptococci
• Main species: Peptostreptococcus anaerobius
Micromonas micros (previously P. micros)
Genus Stomatococcus
• Main species: Stomatococcus (formerly Micrococcus)
mucilagenosus.
Cultural characteristics: coagulase-negative; forms
large colonies adherent to blood agar surface, facultative anaerobes



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Gram-positive rods and filaments

These organisms are common isolates from dental plaque
and include actinomycetes, lactobacilli, eubacteria and propionibacteria

Genus Actinomyces

Short, Gram-positive
• Main species
: Actinomyces israelii; A. gerencseriae;
; A. myeri;. The most important human pathogen is A. israelii is distinguished by its anaerobic or microaerophilic growth and its non acid fast staining



Genus Lactobacillus
Gram-positive bacilli
• Main species: Lactobacillus casei; ; L. acidophilus
• Cultural characteristics: catalase-negative, microaerophilic;
complex nutritional requirements; acidic, optimal
pH 5.5-5.8. Selective medium, Rogosa aga

r


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Genus Propionibacterium
Gram-positive bacilli.catalase negative
• Main species: Propionibacterium acnes (includes P propionicus,
• Cultural characteristics: strict anaerobe; produces propionic acid from glucose,
Main intraoral sites and infections: root surface caries, plaque



Gram-negative cocci
Genus Neisseria
Gram-negative diplococci.
• Main species: Neisseria mucosa; N. sicca.
• Cultural characteristics: asaccharolytic and nonpolysaccharide-
producing, facultative anaerobes.
• Main intraoral sites and infections: isolated in low
numbers from tongue, saliva,
Genus Veillonella
Small, Gram-negative cocci.
• Main species: Veillonella parvula; V. dispar; V. atypica.
• Cultural characteristics: strict anaerobes; selective medium Rogosa vancomycin agar. unable to metabolize carbohydrates;
they therefore use lactate produced by other bacteria and raise the pH of plaque, and are thus considered to be beneficial in relation to dental caries.
• Main intraoral sites and infections:
tongue, saliva and plaque



Gram-negative rods - facultative anaerobic
Genus Haemophilus
Gram-negative coccobacilli.
• Main species: Haemophilus parainfluenzae; H. segnis;; H. haemolyticus; H. parahaemolyticus.
• Cultural characteristics: all isolates are facultative anaerobes; growth is enhanced on heated blood agar(chocolate), requires haemin (X factor) and nicotinamide adenine dinucleotide (V factor) for growth.
• Main intraoral sites and infections: plaque saliv

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Genus Actinobacillus
Gram-negative coccobacilli, microaerophilic
• Cultural characteristics: freshly isolated strains contain
fimbriae that are lost on subculture. Produces many virulence factors: leukotoxin, epitheliotoxin, cdt, collagenase,
• Main intraoral sites and infections: periodontal pockets
Gram negative rods –obligate anaerobic
Genus Fusobacterium
Slender, cigar-shaped Gram-negative rods with rounded ends
Main species: Fusobacterium nucleatum; F. alocis; F. periodonticum.
• Cultural characteristics: require rich media for growth, usually nonhaemolytic;
• Main intraoral sites and infections: most commonisolate is F. nucleatum; normal gingival crevice, tonsils

Spirochaetes:

Are diverse group of spiral motile organisms comprising five genera.of these three genera are human pathogens
1-Treponema
2-Borrelia
3-Leptospira

Genus Treponema

Motile Gram-negative helical cells,
• Main species: Treponema denticola; T. macrodentium;
• Cultural characteristics: all treponemes are strict anaerobes, and difficult to culture. Require enriched media with serum
Found in the gingival crevice; closely associated with acute ulcerative gingivitis, destructive periodontal disease.




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Throat Culture

1.. Use a sterile tongue depressor to keep the tongue from interfering with the swab. Roll the swab back, then streak in the blood agar
3. Using the wax pencil, label the plate with your
name, body site, date, and type of medium.
4. Incubate the plate, inverted, at 35°C for 24 to
72 hours