Dorsey L. Kordick

Bartonella Infection in Animals: Carriership, Reservoir Potential, Pathogenicity, and Zoonotic Potential for Human Infection

Recent observations have begun to support a role for Bartonella spp. as animal as well as human pathogens. Bartonella spp. are vector-transmitted, blood-borne, intracellular, gram-negative bacteria that can induce prolonged infection in the host. Persistent infections in domestic and wild animals result in a substantial reservoir of Bartonella organisms in nature that can serve as a source for inadvertent human infection. The prevalence of bacteremia can range from 50 to 95% in selected rodent, cat, deer, and cattle populations. Dogs infected with Bartonella spp. can develop lameness, endocarditis, granulomatous lymphadenitis, and peliosis hepatis, lesions that have also been reported in association with human infection. Understanding the role of Bartonella spp. as pathogens in cats and other wild or domestic animals awaits the results of additional studies. Considering the extensive animal reservoirs and the large number of insects that have been implicated in the transmission of Bartonella spp., both animal and human exposure to these organisms may be more substantial than is currently believed.

Bartonella vinsonii subsp. berkhoffii subsp. nov., isolated from dogs ; Bartonella vinsonii subsp. vinsonii ; and emended description of Bartonella vinsonii

Two bacterial strains, one isolated from the blood of a dog with valvular endocarditis and one isolated from the blood of a healthy dog, were similar to Bartonella species, as determined by a number of phenotypic criteria, including growth characteristics, biochemical reactions, and cell wall fatty acid composition. The results of 16S rRNA gene sequence similarity studies confirmed that these strains are closely related and belong in the genus Bartonella and that Bartonella vinsonii is their closest relative (the 16S rRNA of isolate 93-C01T [T = type strain] was 99.37% identical to the 16S rRNA of the type strain of B. vinsonii, the 16S rRNA of isolate G7464 was 99.61% identical to the 16S rRNA of the type strain, and the 16S rRNAs of the dog isolates were 99.77% identical to each other). The 16S rRNAs of both strains contained a 12-base insertion that was not present in the 16S rRNA of the type strain of any Bartonella species. DNA relatedness tests revealed that these strains were related at the species level to the type strain of B. vinsonii. They were, however, significantly more closely related to each other than to B. vinsonii. On the basis of their unique 16S rRNA sequence insertion, their preferentially high level of relatedness, and their similar origins (dogs), we believe that strains 93-C01(T) and G7464 should be placed in a separate subspecies of B. vinsonii, for which we propose the name B. vinsonii subsp. berkhoffii subsp. nov. The type strain of B. vinsonii subsp. berkhoffii is strain 93-C01 (= ATCC 51672). The description of B. vinsonii is emended to accommodate the new subspecies, and B. vinsonii subsp. vinsonii is described.

Comparative seroreactivity to Bartonella henselae and Bartonella quintana among cats from Israel and North Carolina

Bartonella henselae, the predominant cause of cat scratch disease, and Bartonella quintana, the cause of trench fever, are closely related Bartonella species that induce cross-reactivity when cat or human sera are tested using an indirect immunofluorescence antibody (IFA) test. Cats are the natural reservoir for B. henselae, whereas a mammalian reservoir host for B. quintana has not been identified. Serum samples from 114 cats from Israel and 114 cats from North Carolina were tested by IFA for seroreactivity to B. henselae and B. quintana antigens. Similar numbers of cats from Israel [45 (39.5%)] and from North Carolina [46(40.4%)] were seroreactive to both antigens, however, as compared to cats from North Carolina [8 (7%)], a significantly (P = 0.001) larger number of cats from Israel were seroreactive to B. quintana antigen only [23 (20.2%)]. In addition, mean antibody titers were lower to B. henselae than to B. quintana (P = 0.0001) in the cats from Israel, whereas similar mean titers to both antigens were identified in cats from North Carolina. Absorption of serum using whole B. henselae organisms resulted in a significantly greater (P = 0.0001) decrease in antibody titer to B. henselae between absorbed and non-absorbed sera, as compared to the decrease in antibody titer following absorption with whole B. quintana organisms. There was a similar decrease in antibody titer in sera from cats experimentally infected with B. henselae and in cats naturally exposed to Bartonella species from Israel and North Carolina. Our results indicate that absorption of serum will, in most instances, distinguish species-specific reactivity by IFA to B. henselae from cross-reactivity to B. quintana in cats experimentally infected with B. henselae. The data support the conclusion that B. henselae is the principal Bartonella species responsible for seroreactivity against B. henselae and B. quintana in naturally exposed cats from Israel or North Carolina. It also suggests that in Israel, cats are exposed to one or more antigenically different Bartonella species, sub-species or strains, that seroreact by IFA more intensely with B. quintana antigen.

Infection of Fetal Feline Brain Cells in Culture with Bartonella henselae

ABSTRACT Bartonella henselae is known to cause central nervous system (CNS) disease in humans, and neurological signs have been observed in experimentally infected cats. However, the pathogenesis of CNS disease remains unclear. This study was undertaken to determine whether B. henselae infects feline fetal brain cells in vitro. Microglial-cell- and astrocyte-enriched cultures were inoculated with B. henselae. Giménez staining identified bacterial organisms within microglial cells by day 7 postinoculation. The viability of the intracellular bacteria was demonstrated by incubating cultures with gentamicin and plating cell lysate on agar. Electron microscopy identified intracellular organisms with characteristic Bartonella morphology but identified no ultrastructural abnormalities within infected microglial cells. No evidence of infection was seen in Bartonella-inoculated astrocyte cultures. These findings suggest a role for microglia in the pathogenesis of B. henselae-associated neurological disease.

Chapter 6 – Bartonella Species and Vascular Pathology

In recent years, an increasing number of Bartonella species have been identified as zoonotic pathogens that are transmitted by animal bites or scratches, needle sticks, blood transfusions, or by arthropods. Potentially, because Bartonella spp. can infect erythrocytes, endothelial cells, pericytes, and various macrophage-type cells, cardiac and vascular pathologies appear to be very diverse in human patients and animals. Due to current limitations associated with diagnostic testing for bartonellosis, a high index of suspicion is required, particularly in patients with persistent bacteremia, small-vessel disease, and nonspecific symptoms, such as fatigue, weakness, muscle, and joint pain. Because of the rapid discovery of new, pathogenic Bartonella spp., the expanding number of arthropods proven or suspected in transmission, the large numbers of infected animal reservoir hosts in nature, and the broad spectrum of cardiovascular abnormalities reported in recent years, bartonellosis may be a much more prevalent cause of cardiovascular disease in immunocompetent and immunocompromised patients throughout the world than is currently recognized.