Cat-Scratch Disease: A self-limiting bacterial infection of the regional lymph nodes caused by AFIPIA felis, a gram-negative bacterium recently identified by the Centers for Disease Control and Prevention and by BARTONELLA HENSELAE. It usually arises one or more weeks following a feline scratch, with raised inflammatory nodules at the site of the scratch being the primary symptom.Bartonella henselae: A species of gram-negative bacteria that is the etiologic agent of bacillary angiomatosis (ANGIOMATOSIS, BACILLARY). This organism can also be a cause of CAT-SCRATCH DISEASE in immunocompetent patients.Bartonella: A genus of gram-negative bacteria characteristically appearing in chains of several segmenting organisms. It occurs in man and arthropod vectors and is found only in the Andes region of South America. This genus is the etiologic agent of human bartonellosis. The genus Rochalimaea, once considered a separate genus, has recently been combined with the genus Bartonella as a result of high levels of relatedness in 16S rRNA sequence data and DNA hybridization data.Angiomatosis, Bacillary: A reactive vascular proliferation that is characterized by the multiple tumor-like lesions in skin, bone, brain, and other organs. Bacillary angiomatosis is caused by infection with gram-negative Bartonella bacilli (such as BARTONELLA HENSELAE), and is often seen in AIDS patients and other IMMUNOCOMPROMISED HOSTS.Bartonella quintana: A species of gram-negative bacteria in which man is the primary host and the human body louse, Pediculus humanus, the principal vector. It is the etiological agent of TRENCH FEVER.Bartonella Infections: Infections by the genus BARTONELLA. Bartonella bacilliformis can cause acute febrile anemia, designated Oroya fever, and a benign skin eruption, called verruga peruana. BARTONELLA QUINTANA causes TRENCH FEVER, while BARTONELLA HENSELAE is the etiologic agent of bacillary angiomatosis (ANGIOMATOSIS, BACILLARY) and is also one of the causes of CAT-SCRATCH DISEASE in immunocompetent patients.Cats: The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)Rickettsiaceae: A family of small, gram-negative organisms, often parasitic in humans and other animals, causing diseases that may be transmitted by invertebrate vectors.Cat Diseases: Diseases of the domestic cat (Felis catus or F. domesticus). This term does not include diseases of the so-called big cats such as CHEETAHS; LIONS; tigers, cougars, panthers, leopards, and other Felidae for which the heading CARNIVORA is used.Trench Fever: An intermittent fever characterized by intervals of chills, fever, and splenomegaly each of which may last as long as 40 hours. It is caused by BARTONELLA QUINTANA and transmitted by the human louse.Siphonaptera: An order of parasitic, blood-sucking, wingless INSECTS with the common name of fleas.Lymphatic Diseases: Diseases of LYMPH; LYMPH NODES; or LYMPHATIC VESSELS.Splenic DiseasesAntibodies, Bacterial: Immunoglobulins produced in a response to BACTERIAL ANTIGENS.Fluorescent Antibody Technique, Indirect: A form of fluorescent antibody technique commonly used to detect serum antibodies and immune complexes in tissues and microorganisms in specimens from patients with infectious diseases. The technique involves formation of an antigen-antibody complex which is labeled with fluorescein-conjugated anti-immunoglobulin antibody. (From Bennington, Saunders Dictionary & Encyclopedia of Laboratory Medicine and Technology, 1984)Immunocompetence: The ability of lymphoid cells to mount a humoral or cellular immune response when challenged by antigen.Polymerase Chain Reaction: In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.DNA, Bacterial: Deoxyribonucleic acid that makes up the genetic material of bacteria.Lymph Nodes: They are oval or bean shaped bodies (1 - 30 mm in diameter) located along the lymphatic system.RNA, Ribosomal, 16S: Constituent of 30S subunit prokaryotic ribosomes containing 1600 nucleotides and 21 proteins. 16S rRNA is involved in initiation of polypeptide synthesis.Immunoglobulin M: A class of immunoglobulin bearing mu chains (IMMUNOGLOBULIN MU-CHAINS). IgM can fix COMPLEMENT. The name comes from its high molecular weight and originally being called a macroglobulin.Sensitivity and Specificity: Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)Immunoglobulin G: The major immunoglobulin isotype class in normal human serum. There are several isotype subclasses of IgG, for example, IgG1, IgG2A, and IgG2B.