Gingivitis caused by which bacteria
Gingivitis is a plaque-driven inflammation involving many oral bacteria, not one single species, when plaque remains at the gum margin.
The short answer
Gingivitis is a plaque-driven inflammation involving many oral bacteria, not one single species, when plaque remains at the gum margin. The bacterial community changes as plaque thickens, and the gums react with redness, swelling, and bleeding.

What is the direct answer?
What does this question mean?
Dental plaque is a living film containing bacteria, saliva proteins, and food debris. Species from groups such as Streptococcus, Actinomyces, and gram-negative anaerobic bacteria can participate, but a laboratory test is not usually needed to identify one culprit in ordinary gingivitis.
What can you do next?
Clean the gumline twice daily with a soft brush and clean between teeth with floss or an interdental brush sized to the space. A dental professional can remove hardened calculus, which a toothbrush cannot detach.
When should you seek dental care?
Book an examination when bleeding continues despite careful cleaning, or when gums are swollen, tender, receding, or producing pus. Loose teeth, persistent bad breath, or bleeding in one isolated area can indicate a problem deeper than simple gingivitis.
What should you ask the dentist?
Ask whether the bleeding is consistent with gingivitis or periodontal disease and whether calculus is present below the gumline. Ask for a demonstration of the correct interdental tool and a plan for reassessing the tissue after cleaning.
Frequently asked questions
Is gingivitis contagious?
The inflammation itself is not passed from person to person, although oral bacteria can be exchanged through saliva.
Can gingivitis become periodontitis?
Untreated gum inflammation can progress in some people to tissue and bone damage, so persistent bleeding needs an examination.
