We analyzed 178 B. henselae
isolates/strains from various sources (): 156 (88%) feline isolates/strains, 21 (11%) from diseased humans, and 1 isolate from a sick dog. The number of alleles varied from 7 (BHV-E) to 22 (BHV-B). Most of the European isolates (all but 1 of feline origin) (2,4,6
) and of the American isolates/strains (North Carolina and California) (5,14
), of which 85% were of feline origin, belonged to genotype II (89% and 64.6%, respectively). The Asian isolates (all but 1 of feline origin) (7–9
) and the Australasian isolates (60% of human origin) (12
), mainly belonged to genotype I (89.6% and 65%, respectively).
Description of Bartonella henselae isolates and strains tested, global diversity of the typing system, and diversity variations according to 16S rDNA genotype, continent, and host*
Ninety-nine different MLVA profiles were observed (), corresponding to an average number of isolates per profile of 1.8 (). Sixty-nine of these profiles were found in only 1 isolate or strain (67%), and 30 were observed in >1 isolate. Among these, none was shared by genotype I and genotype II isolates. Diversity index (DI) was 0.98 (). Diversity was observed in both genotypes because genotype-specific DIs were almost identical ().
Distribution of Bartonella henselae isolates/strains by 16S rDNA genotype, host, and location for profiles with >2 isolates*
MLVA profiles appeared location-specific because only 4 (13%) of the 30 profiles observed in >1 isolate/strain were present in >1 continent (). Within continents, no marked dominance of a given profile was observed, and continent-specific DIs were similar ().
Of the 99 B. henselae profiles, 12 were obtained from the 21 human isolates/strains and 1 from the dog, whereas 92 profiles were obtained from the 156 feline isolates. Five profiles were common to 5 human and 11 feline isolates. Among the 30 profiles observed in >2 isolates, 23 were observed only in feline isolates (). The proportion of genotype I profiles was significantly higher in human-specific profiles than in cat-specific profiles (p = 0.01, by Fisher test).
For BHV-A, only 2 alleles (14 and 15 copies) were found in isolates from humans, whereas all 8 identified alleles were observed in cat isolates. The number of repeats differed significantly between sick humans and healthy cats (p = 0.02, by Fisher test).
Relationships between the 99 MLVA profiles were analyzed by unweighted pair group method with arithmatic mean (UPGMA), using a categorical distance, with a B. koehlerae
isolate used as an outgroup. To take into account that UPGMA is sensitive to taxa entry order, we computed the majority-rule consensus tree of 500 dendrograms built with random taxa entry order. MLVA profiles were grouped into 2 main groups named A and B (Appendix Figure
). Group A (26 profiles), was exclusively constituted by genotype II feline isolates. Group B (73 profiles), to which all human isolates belonged, further divided in 2 subgroups, Ba and Bb. Subgroup Ba (38 profiles) was exclusively composed of genotype I isolates, including the reference strain Houston I and a homogenous subgroup, Ba1, containing 84% of the Asian isolates. Finally, 83% of subgroup Bb isolates belonged to genotype II (29/35 profiles).
The utility of MLVA for molecular epidemiologic analysis of clusters was tested using isolates from California cats and their owners (14
). Five human–cat groups of B. henselae
isolates were analyzed. For 1 cat-human pair of isolates, which belonged, respectively, to genotype II and genotype I, major profile differences were observed, as expected. The 4 other cat-human groups, which possessed the same genotype, also had the same MLVA profile with the 5 tested BHV, as well as with the 6 additional BHV (F–K) and variant alleles for BHV-A and/or B (6
). Sequencing confirmed these results.