Everyone I know keeps telling me that people and birds should not have mouth-to-beak contact because of the germs (bacteria and yeast) that humans carry. What organisms in our mouths are dangerous? Can you tell me if birds should not be allowed to take food from an owner's mouth or be kissed? Should they not be allowed to touch a human tongue or teeth?

Good question! You know, I tell folks this all the time, too, and I had never looked into what organisms are involved, either! So, I asked my dentist, good friend and Moluccan cockatoo owner Dr. Rosalie Robbins about this. She was kind enough to do some research for me, and now I can answer your questions.
Studies by dentists and dental researchers in recent years have helped clarify the role of various microscopic organisms in the development of dental cavities (technically called caries). Specific microorganisms as well as combinations of them have been studied. Many of these organisms are responsible for causing disease (caries, periodontal disease, abscesses) and have also been diagnosed as causing disease in psittacines. Although we often think that most bacterial infections are usually caused by Gram-negative bacteria, Gram-positive bacteria also cause disease on occasion.

Gram-positive cocci (bacteria) in the Staphylococcus, Streptococcus and Enterococcus groups are often found in the gum and periodontal tissues of humans, and are also responsible for causing disease in birds. Although these bacteria may normally be found on the skin and mucous membranes, they may be responsible for causing disease if cultured from other sites. These organisms may produce toxins and pathogenicity factors that can make a bird ill. They may also be considered to be secondary invaders. If these bacteria get into the bloodstream, they may cause clot-inducing infections, joint and bone lesions or heart problems. If Staph gets into the bloodstream, it may cross into the central nervous system, resulting in tremors and abnormal head posture. Staph can also cause bumblefoot, or necrotizing abscesses on the bottom surface of the foot of infected birds. It may also cause dermatitis, which may turn gangrenous. In baby birds, Staph may cause an infection in the bellybutton (umbilicus) if the yolk sac is not absorbed normally. Both Strep and Enterococcus can be pathogenic, although some strains generally have a low level of ability to cause disease. They may cause the same kinds of disease as Staph can. Gram-positive rods are also found in the mouth of humans, in the gum tissue or in periodontal pockets. Corynebacterium is usually recovered from clinically normal, healthy birds. Another Gram-positive rod found in the human mouth is Lactobacillus. Most of you have probably heard of this bacteria; it is often prescribed for birds after antibiotic therapy, and it is considered one of the good bacteria.

Birds Play Stands

Some Gram-negative rods are also found in the gums and periodontal pockets of humans. Of the most common ones, Campylobacter is the one most likely to cause disease in birds. It may cause liver disease and vague signs of lethargy, decreased appetite, diarrhea (often with yellowish-staining feces) and emaciation. Bacteroides and Fusobacterium are other Gram-negative rods found in the human mouth, but their ability to cause disease in birds is not well documented.

Another group of bacteria, the spirochetes, have been found in the human mouth and also are sometimes found in psittacines and passerines. They may include Borrelia, Treponema, and some larger spirochetes. Most commonly, spirochetes have been implicated as a cause of infection in cockatiels, but they have also been seen in other species of birds, such as lovebirds.

Those are the bacteria that are found in the human mouth that can cause disease in birds; however, there are probably other bacteria that can be found in humans that do not cause dental caries. For example, the bacteria that causes tuberculosis, Mycobacterium, can be found in the sputum, and therefore the mouth, of some infected people.

Yeast can sometimes be found in the mouth of some humans, and it may cause disease in birds. Yeast is in the fungal family and is not a bacterium.

This is far from a complete list of the organisms that can be found in the human mouth, but hopefully it is enough to make you keep your birds from doing any dental work on you and to keep you from allowing your birds to eat out of your mouths.