ORAL MICROBIOLOGY

Normal Microbial Flora

Normal oral cavity contains a mixture of organisms which

include bacteria, fungi, protozoa and occasionally virus.

Some of the organisms are almost always in normal oral

cavity and are called Resident Flora.

Some organisms stay for a limited period in the oral cavity

of a few individuals. These are named as Transient Flora.

Microbial flora of mouth

Among all micro-organism present in the mouth

bacteria are most predominant.

These includes both aerobic and anaerobic

bacteria

cocci

GRAM POSITIVE COCCI Strep.mutans Strep.sanguis Strep.salivarius Strep.mitior Strep.milleri Enterococcus sps Peptostreptococcus aps Micrococcus sps Staphylococcus sps

GRAM NEGATIVE COCCI

Veillonella sps

Neisseria sps

Branhamella sps

Bacilli

GRAM POSITIVE BACILLI

Lactobacillus sps

Actinomycetes sps

Propionibacterium sps

Arachnia sps

Bifidobacterium sps

Bacterionema sps

Eubacterium sps

GRAM NEGATIVE BACILLI Actinobacillus sps Fusobacterium sps Bacteroids sps Capanocytophaga sps Leptotrichina sps Treponema sps Haemophilus sps Selenomonas sps Eikenella sps Wollinella sps

Of all bacteria present in mouth, streptococci are

predominant group.

Various species of Streptococci are encountered in mouth.

Most of these are alpha-haemolytic

streptococci, collectively named as viridians streptococci

Lactobacilli are frequently found in mouth.

They are imp bacteria to promote the progress of

carious lesion after the initiaton of dental caries

by Strep mutans

Veilonella is the most common among Gram-negative bacteria.

Fusobacterium nucleatum is the most commonly occurring Gram-negative anaerobic bacillus

Other anaerobes such as Bacteroids, Leptotrichia, Selenomonas etc have also been found to be an imp group

Oral treponema(T.vincenti,T.denticola,T.orale) are

comman inhabitants of gingival crevice & sub

gingival area

Due to their presence in subgingival plagues, they

have been imp role in causing gingivitis and most

forms of periodontitis.

Besides bacteria normal flora of mouth may contain fungi and protozoa

FUNGI Candida albicans C.tropicalis C.pseudotropicalis C.stellatoidea Cryptococcus sps PROTOZOA Entamoeba gingivalis Trichomanas tenax

Acquisition Of Normal Flora Of Mouth

The mouth of newborn at birth is usually

microbiologically sterile.

Within few hours of birth Streptococci establish

themselves in the mouth.

Acquisition Of Normal Flora Of Mouth – Cont’d

Among Streptococci, Strep. salivarius is dominant

at this stage.

During the first year of life other species of

Streptococci,Staphylococci,Neisseriae,Veilonella,

Actinomyces,Lactobacilli and Fusobacteria also

colonize.

Acquisition Of Normal Flora Of Mouth – Cont’d

With the eruption of teeth, solid surfaces in the

oral cavity are available for colonization.

Strep mutans, Strep sanguis establish themselves

on these hard surfaces.

Simultaneously, there is also increase in number

of obligate anaerobes

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