I received the following question from a reader the other day: "I'm currently pregnant and was bitten by my grandmother's German Shepherd. The bite was on my ankle and broke the skin in several places. I went to the doctor and was prescribed antibiotics and the wound has seemed to heal fine. This is my second pregnancy and I have been diagnosed as group B strep positive, which I wasn't with my first child. I know that dogs can't spread strep throat to humans, but is it possible that I picked up group B strep from the bite?"
The short answer is that it's extremely unlikely there's an association.
Group B Streptococcus is predominantly a problem in people. Most people that carry this bacterium have no problems, although it can cause infections in some situations. It is of particular concern in pregnant women, because in 1-2% of exposed newborn babies the bacterium can cause serious infections such as bloodstream infections, meningitis and pneumonia. That is why pregnant women are often screened for Group B Streptococcus shortly before their due date, by taking a swab from the vagina and rectum. Approximately 10-30% of pregnant women carry Group B Streptococcus. Pregnant women that are carriers are usually given antibiotics shortly before delivery to reduce the risk of infection of the baby.
What about the role of pets? Group B Streptococcus is mainly found in people, and is quite common in healthy people. It is rare in pets, although it can cause various types of infections in animals too. Group B Streptococcus infections in dogs might actually represent human-to-dog transmission, although this hasn't been proven. In the case described above, a dog bite on a person's leg would not be a high risk for transmitting this bacterium to the intestinal tract or vagina. If a dog was carrying this bacterium in its mouth, it could cause a bite wound infection, but it is very unlikely that the bacterium would spread to other parts of the body in a healthy person. Other bacteria in the dog's mouth would be more likely to infect such a wound, even if Group B Streptococcus was present. If dogs were common carriers of this bacterium (which they are not), the main risk of transmission would be from regular contact, not bites.
So don't blame the dog... at least not for the Group B Streptococcus. The bite itself is another issue.