A comparison of BHI/vancomycin agar, VITEK, and Kirby-Bauer methodologies for identifying Vancomycin resistance in enterococcal isolates from laboratory specimens

A comparison of BHllvancomycin agar. VITEK. and Kirby-Bauer disk. diffusion methodologies for identifying vancomycin resistance in Enterococcal isolates was conducted. One hundred-six Enterococcal isolates were collected from several clinical sites in the Northern Illinois region and tested to determine vancomycin susceptibility by each of the three methodologies. Of the 106 isolates tested. 23 were determined by the BHllvancomycin agar method to be vancomycin resistant and 83 were determined to be vancomycin susceptible. VITEK correctly identified all of the 83 vancomycin susceptible isolates (100%) and 20 of the 23 vancomycin resistant isolates (87%). Kirby-Bauer disk. diffusion cooectly identified all of the 83 vancomycin susceptible isolates (100%) and 22 of the 23 vancomycin resistant isolates (95.6%). The sensitivity and specificity of each of the three methodologies evaluated in this study are quite high; however. whether or not these values justify using only VITEK or Kirby-Bauer susceptibility testing without a confirmatory method can not be determined by this rather limited study alone. These results do confirm that incorrect susceptibility testing results occur with both VITEK and Kirby-Bauer methodologies, particularly in determining vancomycin resistance. Until additional studies confirm that automated MIC determination Q Kirby-Bauer susceptibility testing consistently give reliable results. confirmatory testing with BHllvancomycin agar plates will ensure that accurate vancomycin susceptibility results are reported for Enterococcal isolates

Prevalence of Bartonella henselae and Bartonella clarridgeiae in cats in the south of Brazil: a molecular study

Bartonella spp are the causative agent of cat scratch disease in humans. Cats are the natural reservoir of these bacteria and may infect humans through scratches, bites or fleas. Blood samples from 47 cats aged up to 12 months were collected for this study. All animals were lodged in municipal animal shelters in the Vale do Sinos region, Rio Grande do Sul, Brazil. Bartonella spp were detected by genus-specific polymerase chain reaction (PCR) and when the PCR was positive, the species were determined by DNA sequencing. A Giemsa-stained blood smear was also examined for the presence of intraerythrocytic elements suggestive of Bartonella spp infection. Phylogenetic analysis was also performed for all positive samples. Using molecular detection methods, Bartonella spp were detected in 17.02% (8/47) of the samples. In seven out of eight samples confirmed to be positive for Bartonella spp, blood smear examination revealed the presence of intraerythrocytic elements suggestive of Bartonella spp. Phylogenetic analysis characterized positive samples as Bartonella henselae (5) or Bartonella clarridgeiae (3). To the best of our knowledge, this is the first molecular study demonstrating the presence of Bartonella spp in cats from the Southern Region of Brazil

<i>Bartonella henselae</i> Invasion of Feline Erythrocytes In Vitro

ABSTRACT Bartonella henselae , the causative agent of cat scratch disease, establishes long-term bacteremia in cats, in which it attaches to and invades feline erythrocytes (RBC). Feline RBC invasion was assessed in vitro, based on gentamicin selection for intracellular bacteria or by laser confocal microscopy and digital sectioning. Invasion rates ranged from 2 to 20% of the inoculum, corresponding to infection of less than 1% of the RBC. Invasion was a slow process, requiring &gt;8 h before significant numbers of intracellular bacteria were detected. Pretreatment of the bacteria with trypsin, or of the RBC with trypsin or neuraminidase, had no effect, but pronase pretreatment of RBC resulted in a slight increase in invasion frequency. The ability to model B. henselae invasion of feline RBC in vitro should permit identification of bacterial surface components involved in this process and elucidate the significance of RBC invasion to transmission and infection in cats. </jats:p

Bartonella entry mechanisms into mammalian host cells

The Gram-negative genus Bartonella comprises arthropod-borne pathogens that typically infect mammals in a host-specific manner. Bartonella bacilliformis and Bartonella quintana are human-specific pathogens, while several zoonotic bartonellae specific for diverse animal hosts infect humans as an incidental host. Clinical manifestations of Bartonella infections range from mild symptoms to life-threatening disease. Following transmission by blood-sucking arthropods or traumatic contact with infected animals, bartonellae display sequential tropisms towards endothelial and possibly other nucleated cells and erythrocytes, the latter in a host-specific manner. Attachment to the extracellular matrix (ECM) and to nucleated cells is mediated by surface-exposed bacterial adhesins, in particular trimeric autotransporter adhesins (TAAs). The subsequent engulfment of the pathogen into a vacuolar structure follows a unique series of events whereby the pathogen avoids the endolysosomal compartments. For Bartonella henselae and assumingly most other species, the infection process is aided at different steps by Bartonella effector proteins (Beps). They are injected into host cells through the type IV secretion system (T4SS) VirB/D4 and subvert host cellular functions to favour pathogen uptake. Bacterial binding to erythrocytes is mediated by Trw, another T4SS, in a strictly host-specific manner, followed by pathogen-forced uptake involving the IalB invasin and subsequentreplication and persistence within a membrane-bound intra-erythrocytic compartment