No abstract

Bartonella species were isolated from the blood of 63 of 325 Rattus norvegicus and 11 of 92 Rattus rattus from 13 sites in the United States and Portugal. Infection in both Rattus species ranged from 0% (e.g., 0/87) to approximately 60% (e.g., 35/62). A 337-bp fragment of the citrate synthase (gltA) gene amplified by polymerase chain reaction was sequenced from all 74 isolates. Isolates from R. norvegicus were most similar to Bartonella elizabethae, isolated previously from a patient with endocarditis (93%-100% sequence similarity), followed by Bartonella grahamii and other Bartonella species isolated from Old World rodents (Clethrionomys species, Mus musculus, and Rattus species). These data suggest that Rattus species are a reservoir host for pathogenic Bartonella species and are consistent with a hypothesized Old World origin for Bartonella species recovered from Rattus species introduced into the Americas.

A phylogenetic investigation was done on the members of the genus Battonella, based on the DNA sequence analysis of the groEf gene, which encodes the 60 kDa heat-shock protein GroEL. Nucleotide sequence data were determined for a near full-length fragment (1368 bp) of the gm€L gene of the established Bartonella species and used to infer intraspecies phylogenetic relationships. Phylogenetic trees were inferred from multiple sequence alignments by using both distance and parsimony methods, which demonstrated an architecture composed of six well-supported lineages. The results are consistent with relationships deduced from recent sequence analysis studies based upon citrate synthase (gltA) and previously observed genotypic and phenotypic characteristics; however, they showed greater statistical support at the intragenus level. This suggests that groEf may be a more robust tool for phylogenetic analysis of Bartonella lineages.

The temporal dynamics of Bartonella infections in a rodent community were described by repeatedly capturing and sampling individual animals. Among six rodent species, from which bartonellae were isolated, cotton rats (Sigmodon hispidus) accounted for > 98% of the bacteremic animals. All cotton rats captured four or more times were Bartonella-culture positive at least once. The lowest monthly prevalence of Bartonella in cotton rats was in June (49%) and the highest was in October (95%). Prevalence of Bartonella infection increased to > 90% among juvenile and subadult rats before declining to < 40% among the largest-oldest individuals. Bacteremia levels ranged between 40 and 4.0 x 10(6) colony forming units (CFU) per 1 mL of blood. Male cotton rats had significantly higher CFUs than females (p = 0.006). The median of Bartonella bacteremia decreased monotonically by age group among cotton rats. Although Bartonella infections were highly prevalent among cotton rats, only 8.5% of rats had reactive antibodies at titers of > or = 1:32 and none had antibodies titers of > 1:256.