Drug Incompatibility: The quality of not being miscible with another given substance without a chemical change. One drug is not of suitable composition to be combined or mixed with another agent or substance. The incompatibility usually results in an undesirable reaction, including chemical alteration or destruction. (Dorland, 27th ed; Stedman, 25th ed)Blood Group Incompatibility: An antigenic mismatch between donor and recipient blood. Antibodies present in the recipient's serum may be directed against antigens in the donor product. Such a mismatch may result in a transfusion reaction in which, for example, donor blood is hemolyzed. (From Saunders Dictionary & Encyclopedia of Laboratory Medicine and Technology, 1984).Wolbachia: A genus of bacteria comprised of a heterogenous group of gram-negative small rods and coccoid forms associated with arthropods. (From Bergey's Manual of Systematic Bacteriology, vol 1, 1984)Hybridization, Genetic: The genetic process of crossbreeding between genetically dissimilar parents to produce a hybrid.Rickettsiaceae: A family of small, gram-negative organisms, often parasitic in humans and other animals, causing diseases that may be transmitted by invertebrate vectors.Crosses, Genetic: Deliberate breeding of two different individuals that results in offspring that carry part of the genetic material of each parent. The parent organisms must be genetically compatible and may be from different varieties or closely related species.Reproductive Isolation: Mechanisms that prevent different populations from exchanging genes (GENE FLOW), resulting in or maintaining GENETIC SPECIATION. It can either prevent mating to take place or ensure that any offspring produced is either inviable or sterile, thereby preventing further REPRODUCTION.R Factors: A class of plasmids that transfer antibiotic resistance from one bacterium to another by conjugation.