Susceptibility of Polish Bartonella henselae strains.

Due to the fastidious nature of B. henselae and the limited number of available isolates worldwide, there are few data on its in vitro susceptibility to antibiotics. We determined the minimal inhibitory concentrations (MIC) of ten antimicrobial agents against 11 feline isolates of B. henselae by Etest method. The lowest MICs were obtained for rifampicin < or = 0.002 mg/L. MICs of all isolates were < 0.016 mg/L for ampicilin, amoxicillin/clavulanic acid, tetracycline and ranged from 0.016 to 0.032 mg/L for azithromycin. The MICs for two tested fluoroquinolones: ciprofloxacin and levofloxacin ranged from 0.016 to 0.125 mg/L. The highest MICs were obtained for gentamicin ranging from 0.025 to 2.0 mg/L. Sulphonamide resistance genes sul 1, sul 2, sul 3 were not found in any of the tested isolates. Etest methodology seems to be a reliable method for determination of B. henselae susceptibility, however standardization is strongly desired.

Heme degrading protein HemS is involved in oxidative stress response of Bartonella henselae.

Bartonellae are hemotropic bacteria, agents of emerging zoonoses. These bacteria are heme auxotroph Alphaproteobacteria which must import heme for supporting their growth, as they cannot synthesize it. Therefore, Bartonella genome encodes for a complete heme uptake system allowing the transportation of this compound across the outer membrane, the periplasm and the inner membranes. Heme has been proposed to be used as an iron source for Bartonella since these bacteria do not synthesize a complete system required for iron Fe³âº uptake. Similarly to other bacteria which use heme as an iron source, Bartonellae must transport this compound into the cytoplasm and degrade it to allow the release of iron from the tetrapyrrole ring. For Bartonella, the gene cluster devoted to the synthesis of the complete heme uptake system also contains a gene encoding for a polypeptide that shares homologies with heme trafficking or degrading enzymes. Using complementation of an E. coli mutant strain impaired in heme degradation, we demonstrated that HemS from Bartonella henselae expressed in E. coli allows the release of iron from heme. Purified HemS from B. henselae binds heme and can degrade it in the presence of a suitable electron donor, ascorbate or NADPH-cytochrome P450 reductase. Knocking down the expression of HemS in B. henselae reduces its ability to face H2O2 induced oxidative stress.

The Bartonella henselae VirB/Bep system interferes with vascular endothelial growth factor (VEGF) signalling in human vascular endothelial cells.

The vasculotropic pathogen Bartonella henselae (Bh) intimately interacts with human endothelial cells (ECs) and subverts multiple cellular functions. Here we report that Bh specifically interferes with vascular endothelial growth factor (VEGF) signalling in ECs. Bh infection abrogated VEGF-induced proliferation and wound closure of EC monolayers as well as the capillary-like sprouting of EC spheroids. On the molecular level, Bh infection did not alter VEGF receptor 2 (VEGFR2) expression or cell surface localization, but impeded VEGF-stimulated phosphorylation of VEGFR2 at tyrosine(1175) . Consistently, we observed that Bh infection diminished downstream events of the tyrosine(1175) -dependent VEGFR2-signalling pathway leading to EC proliferation, i.e. phospholipase-Cγ activation, cytosolic calcium fluxes and mitogen-activated protein kinase ERK1/2 phosphorylation. Pervanadate treatment neutralized the inhibitory activity of Bh on VEGF signalling, suggesting that Bh infection may activate a phosphatase that alleviates VEGFR2 phosphorylation. Inhibition of VEGFR2 signalling by Bh infection was strictly dependent on a functional VirB type IV secretion system and thereby translocated Bep effector proteins. The data presented in this study underscore the role of the VirB/Bep system as important factor controlling EC proliferation in response to Bh infection; not only as previously reported by counter-acting an intrinsic bacterial mitogenic stimulus, but also by restricting the exogenous angiogenic stimulation by Bh-induced VEGF.

Comparative activity of pradofloxacin, enrofloxacin, and azithromycin against Bartonella henselae isolates collected from cats and a human.

Using Bartonella henselae isolates from cats and a human, the activity of pradofloxacin was compared with those of enrofloxacin and azithromycin. By Etest and disc diffusion assay, pradofloxacin showed greater antimicrobial activity than did other antibiotics. We conclude that pradofloxacin may prove useful for the treatment of B. henselae infections.

Detrimental effects of Bartonella henselae are counteracted by L-arginine and nitric oxide in human endothelial progenitor cells.

The recruitment of circulating endothelial progenitor cells (EPCs) might have a beneficial effect on the clinical course of several diseases. Endothelial damage and detachment of endothelial cells are known to occur in infection, tissue ischemia, and sepsis. These detrimental effects in EPCs are unknown. Here we elucidated whether human EPCs internalize Bartonella henselae constituting a circulating niche of the pathogen. B. henselae invades EPCs as shown by gentamicin protection assays and transmission electron microscopy (TEM). Dil-Ac-LDL/lectin double immunostaining and fluorescence-activated cell sorting (FACS) analysis of EPCs revealed EPC bioactivity after infection with B. henselae. Nitric oxide (NO) and its precursor l-arginine (l-arg) exert a plethora of beneficial effects on vascular function and modulation of immune response. Therefore, we tested also the hypothesis that l-arg (1-30 mM) would affect the infection of B. henselae or tumor necrosis factor (TNF) in EPCs. Our data provide evidence that l-arg counteracts detrimental effects induced by TNF or Bartonella infections via NO (confirmed by DETA-NO and L-NMMA experiments) and by modulation of p38 kinase phosphorylation. Microarray analysis indicated several genes involved in immune response were differentially expressed in Bartonella-infected EPCs, whereas these genes returned in steady state when cells were exposed to sustained doses of l-arg. This mechanism may have broad therapeutic applications in tissue ischemia, angiogenesis, immune response, and sepsis.

Familial occurrence of cat-scratch disease, with varying clinical expression.

Cat-scratch disease, primarily caused by Bartonella henselae, typically presents with regional adenopathy, and the role of antibiotics in the treatment is debatable. We present a report of B. henselae infection transmitted by the same kitten to 4 different individuals, each with different clinical characteristics, treatment, and evolution.

Antimicrobial susceptibility of Bartonella henselae using Etest methodology.

OBJECTIVES: Bartonella henselae is a fastidious slow growing pathogen which is seldom cultured in the laboratory. Previous descriptions of antimicrobial susceptibility have been largely limited to feline isolates and/or laboratory reference strains, with no accounting for genotypic or phenotypic diversity. METHODS: An optimal method of antimicrobial susceptibility testing by Etest was established to compare the antimicrobial susceptibilities of 12 different isolates of B. henselae, 5 human and 7 feline, which have previously been well characterized by 16S rRNA sequencing, multi-locus sequence typing (MLST), phase variation and passage number. RESULTS: No difference in susceptibility could be attributed to differences in genotype, source of the isolate or passage number. Where comparisons were drawn with previously published results, these were found to be concordant. CONCLUSIONS: We conclude that antibiotic susceptibility can be determined by a simple Etest method for B. henselae isolates. This method is reproducible among diverse strains, and is sufficiently predictable that generalizations can be confidently made about optimal antibiotic choices.

Cure of bartonella endocarditis of a prosthetic aortic valve without surgery: value of serologic follow-up.

Bartonella species are emerging as an important cause of blood culture-negative endocarditis, but the optimal management of this disease has not been fully defined. We describe a case of subacute Bartonella henselae endocarditis of a prosthetic aortic valve in an immunocompetent woman that was cured with long-term antibiotic therapy alone. In addition, we demonstrate that follow-up of serologic titers against B. henselae was helpful in assessing definitive cure of the infection.

Cat scratch disease due to Bartonella henselae infection mimicking parotid malignancy.

An unusual Bartonella henselae infection presenting clinically as a putative parotid cancer was diagnosed based on serological tests, histomorphology and amplification of a 16S-rDNA sequence of Bartonella henselae. The patient improved greatly upon antibiotic treatment and did not require surgery. Although uncommon, infection with Bartonella spp., particularly Bartonella henselae, should be included in the differential diagnosis of parotid tumors.

Osteomielitis: una manifestación inusual de la enfermedad por arañazo de gato / Osteomyelitis: an uncommon involvement of cat scratch disease

La enfermedad por arañazo de gato (EAG) ha sido reconocida con frecuencia creciente en nuestro medio. Si bien se presenta habitualmente como un cuadro benigno y autolimitado, 5 a 25 por ciento de los casos pueden presentar complicaciones sistémicas que incluyen, entre otras, manifestaciones viscerales, cutáneas y óseas. Debido al inusual compromiso óseo descrito en la literatura, consideramos de interés presentar un caso clínico de una osteomielitis costovertebral asociada a ESG y discutir el eventual beneficio de la terapia antibacteriana en esta enfermedad

Enfermedad por arañazo de gato complicada con compromiso sistématico, osteomielitis osteovertebral y absceso paravertebral / Cat-scratch disease with systemic envolvememt, osteovertebral osteomyelitis and paravertebral abscess

La enfermedad por arañazo de gato (EAG) es una enfermedad infecciosa aguda benigna relativamente común, causada por Bartonella henselae. De los casos descritos sólo una pequeña proporción presenta compromiso extra nodal. Presentamos dos casos, una niña de 9 añosy un niño de 10 años. con EAG complicada por compromiso osteomielítico múltiple en vertebras, esternón, cráneo, pelvis y absceso paravertebral esplénico y linfadenopatía en uno de ellos, e importante compromiso vertebral con destrucción ósea en el otro. Se trataron con claritromicina y rifampicina en un caso, sólo con claritromicina en el otro. Ambos evolucionaron en mut buena forma con rápida mejoría clínica, radiológica y cintigráfica. Se analizan los casos y el manejo basado en la literatura publicada sobre EAG y esta inhabitual presentación con compromisos osteovertebrales múltiples