ORAL BACTERIA

The oral cavity is home to >500 different species of bacteria that have been found so far. >90% of these are not found anywhere else, only 30 can live in other places. Why is the mouth such a popular place? Well it’s nice and moist all the time, and there is lots of food there.

Bacteria need to stick to survive, and this is a big problem in the mouth. The bacteria are subject to shear forces but still have to manage to hold on. The tooth is a great place for bacteria to grow because it is never shed. When you clean your teeth, you give a nice smooth surface for bacteria to stick on to; these are called the early colonizers. Other bacteria stick to that bacteria and eventually you get a biofilm unique to the mouth.

The early colonizers at first have to survive in aerobic conditions, but as more and more bacteria stick to them, they have to learn to survive in anaerobic conditions. Bacteria also have to adjust to feast and famine situations. When you eat there’s lot of food, and when you don’t there’s no food (unless you’re like me and never stop eating).

The tongue is the most populated part of the body; it’s kinda like a shag carpet with lots of crevasses and hills. However, it rarely gets infections, so there must be a huge immune system going on there. The main source of bad breath is the back of the tongue.

When a baby is born, she is sterile until she is colonized by her parent’s bacteria. That’s right, you inherited your bad breath, BO, and all your other bacteria from your parents. Think of that the next time you see a mom hugging and kissing her baby – she’s really infecting the baby.

Cavities are because of the bacteria that likes refined sugar. People who don’t eat refined sugar don’t get so many cavities.

Saliva has lysozyme, antibodies, lactoperoxidase, and lactoferrin. It’s good because it clears the bacteria from the mouth, but the reason there is so much bacteria in the mouth is that saliva keeps it moist. Saliva is needed for talking, eating, swallowing, and spitting.

You can physically transmit your mouth bacteria by kissing, licking, sharing food and utensils, sneezing, coughing, biting, and oral sex. When you brush your teeth you get a transient bacteremia. Human bite wounds are worse than animal ones because the bacteria are already adapted to live in humans.

Gram + bacteria are vegetative and just secret acid and stuff. Gram – are proteolytic and cause tissue damage, periodontal cases, and bad breath.

Mutans Strep is a group of S. viridans made up of many species with certain things in common. They can take sucrose and produce acid that they are resistant to. They stick in pits and fissures and cause cavities on biting surfaces in kids. After they do the initial damage, the lactobacilli come. Mutans strep can cause SBE (subacute endocarditis).

Periodontal disease is caused by proteolytic anaerobic Gram – species. For example P. gingivalis and Fusobacteria nucleatum. The bacteria invade a crevice and cause inflammation and the tissue destroys itself and the gums recede and your teeth fall out. This has recently been associated with heart disease.

Category: Microbiology Notes