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A new type IV secretion system promotes conjugal transfer in Agrobacterium tumefaciens.

Two DNA transfer systems encoded by the tumor-inducing (Ti) plasmid have been previously identified in Agrobacterium tumefaciens. The virB operon is required for the transfer of transferred DNA to the plant host, and the trb system encodes functions required for the conjugal transfer of the Ti plasmid between cells of Agrobacterium. Recent availability of the genome sequence of Agrobacterium allowed us to identify a third system that is most similar to the VirB type IV secretion system of Bartonella henselae. We have designated this system avhB for Agrobacterium virulence homologue virB. The avhB loci reside on pAtC58 and encode at least 10 proteins (AvhB2 through AvhB11), 7 of which display significant similarity to the corresponding virulence-associated VirB proteins of the Ti plasmid. However, the AvhB system is not required for tumor formation; rather, it mediates the conjugal transfer of the pAtC58 cryptic plasmid between cells of Agrobacterium. This transfer occurs in the absence of the Ti plasmid-encoded VirB and Trb systems. Like the VirB system, AvhB products promote the conjugal transfer of the IncQ plasmid RSF1010, suggesting that these products comprise a mating-pair formation system. The presence of plasmid TiC58 or plasmid RSF1010 reduces the conjugal transfer efficiency of pAtC58 10- or 1,000-fold, respectively. These data suggest that complex substrate interactions exist among the three DNA transfer systems of Agrobacterium.

Agrobacterium tumefaciens↗

A Rhizobium leguminosarum AcpXL mutant produces lipopolysaccharide lacking 27-hydroxyoctacosanoic acid.

The structure of the lipid A from Rhizobium etli and Rhizobium leguminosarum lipopolysaccharides (LPSs) lacks phosphate and contains a galacturonosyl residue at its 4' position, an acylated 2-aminogluconate in place of the proximal glucosamine, and a very long chain omega-1 hydroxy fatty acid, 27-hydroxyoctacosanoic acid (27OHC28:0). The 27OHC28:0 moiety is common in lipid A's among members of the Rhizobiaceae and also among a number of the facultative intracellular pathogens that form chronic infections, e.g., Brucella abortus, Bartonella henselae, and Legionella pneumophila. In this paper, a mutant of R. leguminosarum was created by placing a kanamycin resistance cassette within acpXL, the gene which encodes the acyl carrier protein for 27OHC28:0. The result was an LPS containing a tetraacylated lipid A lacking 27OHC28:0. A small amount of the mutant lipid A may contain an added palmitic acid residue. The mutant is sensitive to changes in osmolarity and an increase in acidity, growth conditions that likely occur in the nodule microenvironment. In spite of the probably hostile microenvironment of the nodule, the acpXL mutant is still able to form nitrogen-fixing root nodules even though the appearance and development of nodules are delayed. Therefore, it is possible that the acpXL mutant has a host-inducible mechanism which enables it to adapt to these physiological changes.

Acyl Carrier Protein↗

Rochalimaea henselae sp. nov., a cause of septicemia, bacillary angiomatosis, and parenchymal bacillary peliosis.

Nine strains of Rochalimaea spp. that were isolated from patients over a period of 4.5 years were characterized for their enzyme activities, cellular fatty acid compositions, and DNA interrelatedness among Rochalimaea spp., Bartonella bacilliformis, and Afipia felis (cat scratch disease bacillus). All except one isolate, which was Rochalimaea quintana, were determined to belong to a newly proposed species, Rochalimaea henselae sp. nov. After recovery from clinical material, colonies required 5 to 15 days of incubation to become apparent. Cells were small, gram-negative, curved bacilli and displayed twitching motility. Enzyme specificities for amino acid and carbohydrate substrates showed that R. henselae could be distinguished from Rochalimaea vinsonii by L-arginyl-L-arginine and L-lysyl-L-alanine peptidases, but not all strains could be distinguished from R. quintana on the basis of peptidases or carbohydrate utilization. R. henselae also closely resembled R. quintana in cellular fatty acid composition, with both consisting mainly of C18:1, C18:0, and C16:0 fatty acids. However, the strains of R. henselae all contained C18:0 in amounts averaging greater than or equal to 22%, in contrast to R. quintana, which contained this cellular fatty acid in amounts averaging 16 and 18%. DNA hybridization confirmed the identification of one clinical isolate as R. quintana and showed a close interrelatedness (92 to 100%) among the other strains. Under optimal conditions for DNA reassociation, R. henselae showed approximately 70% relatedness to R. quintana and approximately 60% relatedness to R. vinsonii. Relatedness with DNA from B. baciliformis was 43%. R. henselae was unrelated to A. felis. R. henselae is the proposed species of a newly recognized member of the family Rickettsiaceae, which is a pathogen that may be encountered in immunocompromised or immunocompetent patients. Prolonged fever with bacteremia or vascular proliferative lesions are clinical manifestations of the agent.

Adult↗

Murine antibody responses distinguish Rochalimaea henselae from Rochalimaea quintana.

Rochalimaea henselae causes persistent bacteremia, bacillary angiomatosis, and parenchymal bacillary peliosis. Detection of a specific antibody response to R. henselae infection may represent an alternative to cultivation as a means of diagnosis. We assessed the specificity of induced murine antibodies for antigens from R. henselae and the closely related species R. quintana. Groups of CD-1 mice were inoculated with whole organisms of six strains of R. henselae and two of R. quintana. Pre- and postinoculation blood specimens were collected. Enzyme immunosorbent assays were performed by using as antigens preparations of immunogenic proteins from one isolate of R. henselae or from the R. quintana type strain. These demonstrated high specificity of R. henselae-induced antibodies for proteins of R. henselae and of R. quintana-induced antibodies for proteins of R. quintana. Protein preparations extracted from all of the strains were separated electrophoretically. After their transfer to membranes, immunoblots were performed by using 1:1,000 dilutions of all of the pre- and postinoculation sera in combination with proteins from all of the strains. Preinoculation sera had minimal reactivity. All of the R. henselae-induced immune sera reacted with numerous proteins of all of the R. henselae strains but cross-reacted minimally with proteins of R. quintana. Immune sera from R. quintana-inoculated mice had similar species specificity. An immunofluorescence assay was developed by using antiserum to one strain of R. henselae. A 1:1,000 dilution yielded fluorescence with all strains of R. henselae but with none of R. quintana, Bartonella bacilliformis, or Afipia felis. Acinetobacter calcoaceticus subsp. anitratus was also unreactive with a dilution of 1:500. A 1:10 dilution yielded weak fluorescence with R. quintana but none with Staphylococcus epidermidis.

Animals↗

Polymerase chain reaction-based restriction fragment length polymorphism analysis of a fragment of the ribosomal operon from Rochalimaea species for subtyping.

Restriction endonuclease analysis of a polymerase chain reaction-amplified DNA fragment which included the spacer region between the genes coding for 16S and 23S rRNAs and a portion of the gene coding for 23S rRNA (spacer + 23S) was done on 10 previously characterized clinical isolates of Rochalimaea henselae, one clinical isolate of Rochalimaea quintana, and the type strains of R. henselae, R. quintana, Rochalimaea vinsonii, and Bartonella bacilliformis. Brucella abortus DNA was not amplified by the primer set used. The clinical isolates of Rochalimaea were obtained from blood or tissue from patients with and without preexisting disease. The amplicon from each strain was digested with five endonucleases (AluI, HaeIII, TaqI, HinfI, and MseI). AluI and HaeIII were useful in species differentiation and subtyping of R. henselae. R. henselae isolates showed six different restriction patterns with AluI and four patterns with HaeIII. TaqI, HinfI, and MseI were useful only in species differentiation. These observations indicate that PCR amplification of the spacer + 23S region of the ribosomal DNA of Rochalimaea spp., along with restriction endonuclease analysis, allows differentiation of Rochalimaea spp. from closely related genera, differentiation among the species within Rochalimaea, and differentiation of strains within R. henselae. The subtyping potential of this method may be useful for further clinical and epidemiologic studies of the spectrum of diseases caused by R. henselae.

Bacterial Typing Techniques↗

Detection of Rochalimaea henselae DNA in specimens from cat scratch disease patients by PCR.

A PCR assay was developed by using degenerate primers that allow amplification of a 414-bp fragment of DNA from the rickettsia-like organisms Rochalimaea henselae and R. quintana. Internal oligonucleotides were used as hybridization probes, permitting rapid differentiation of these two Rochalimaea species. DNAs from 12 different isolates of R. henselae were amplified with the PCR primers, and the resulting 414-bp PCR product hybridized only with the R. henselae-specific probe. DNAs from four different isolates of R. quintana were amplified and produced a PCR product of the same size that hybridized only with the R. quintana-specific probe. DNAs from isolates of R. elizabethae, R. vinsonii, Bartonella bacilliformis, and Afipia felis failed to amplify the 414-bp fragment in the PCR assay. This two-step assay was applied to DNAs extracted from 16 fresh (unfixed) lymph node biopsy specimens and nine aspirates from patients with clinical cat scratch disease (CSD) to assay for the presence of R. henselae or R. quintana DNA in these samples. Twenty-one (84%) of 25 lymph node samples from CSD patients were positive for R. henselae, while none were positive for R. quintana. The characteristic 414-bp fragment was not amplified from eight lymph node tissue samples from non-CSD cases. These results provide evidence that R. henselae, and not R. quintana, plays the central role in the etiology of CSD.

Bacteriological Techniques↗

Serologic cross-reactions among Ehrlichia equi, Ehrlichia phagocytophila, and human granulocytic Ehrlichia.

Homology in the 16S rDNAs shows that the agent of human granulocytic ehrlichiosis (HGE) is closely related to the veterinary pathogens Erlichia equi and Erlichia phagocytophila. After HGE, patients develop antibodies reactive with E. equi and E. phagocytophila; thus, we hypothesized that these species are closely related and share significant antigenicity. Antisera from humans, horses, dogs, and cattle were tested by indirect fluorescent-antibody assay (IFA) for antibodies reactive with E. equi and other ehrlichiae and tested by immunoblot to identify the specific reactions with E. equi. All convalescent-phase sera from human patients with HGE and from animals infected or immunized with E. equi or E. phagocytophila had antibodies reactive with E. equi by IFA; no reactions with Ehrlichia chaffeensis occurred with these sera, and only one horse naturally infected with E. equi had a serologic reaction against Ehrlichia sennetsu. Human and animal sera obtained after infection or immunization with other Ehrlichia, Rickettsia, and Bartonella species did not react with E. equi by IFA. E. equi immunoblots revealed as many as 19 bands with equine anti-E. equi serum. All HGE agent, E. equi, and E. phagocytophila antisera tested reacted with a 44-kDa antigen of E. equi, while other anti-Ehrlichia spp. sera reacted with this antigen rarely or not at all. HGE agent, E. equi, and E. phagocytophila antisera but not other sera also reacted occasionally with 25-, 42-, and 100-kDa antigens. Most sera reacted with antigens between approximately 56 and 75 kDa, probably heat shock proteins. The HGE agent, E. equi, and E. phagocytophila share significant antigenicity by IFA and immunoblot. Coupled with the nearly identical nucleotide sequences of 16S rRNA genes, these data indicate that E. equi, E. phagocytophila, and the human granulocytic ehrlichia are closely related or identical species.

Animals↗

PCR amplification and comparison of nucleotide sequences from the groESL heat shock operon of Ehrlichia species.

Degenerate PCR primers derived from conserved regions of the eubacterial groESL heat shock operon were used to amplify groESL sequences of Ehrlichia equi, Ehrlichia phagocytophila, the agent of human granulocytic ehrlichiosis (HGE), Ehrlichia canis, Bartonella henselae, and Rickettsia rickettsii. The groESL nucleotide sequences were less conserved than the previously determined 16S rRNA gene sequences of these bacteria. A phylogenetic tree derived from deduced GroEL amino acid sequences was similar to trees based on 16S rRNA gene sequences. Nucleotide sequences obtained from clinical samples containing E. equi, E. phagocytophila, or the HGE agent were very similar (99.9 to 99.0% identity), and the deduced amino acid sequences were identical. Some divergence was evident between nucleotide sequences amplified from samples originating from the United States (E. equi and the HGE agent) and sequences from the European species, E. phagocytophila. A single pair of PCR primers derived from these sequences was used to detect E. chaffeensis and HGE agent DNA in blood samples from human patients with ehrlichiosis.

Base Sequence↗

Identification of Brucella by ribosomal-spacer-region PCR and differentiation of Brucella canis from other Brucella spp. pathogenic for humans by carbohydrate profiles.

Molecular and chemical characteristics often provide complementary information in the differentiation of closely related organisms. The genus Brucella consists of a highly conserved group of organisms. Identification of the four species pathogenic in humans (Brucella melitensis, Brucella abortus, Brucella suis, and Brucella canis) is problematic for many clinical laboratories that depend primarily on serology and phenotypic characteristics to differentiate species. PCR amplification of the 16S-23S ribosomal DNA interspace region was evaluated for species-specific polymorphism. B. abortus, B. melitensis, B. suis, and B. canis produced identical PCR interspace profiles. However, these PCR products were unique to brucellae, allowing them to be readily distinguished from other gram-negative bacteria (including Bartonella spp. and Agrobacterium spp.). Carbohydrate profiles differentiated B. canis from the other three Brucella species due to the absence of the rare amino sugar quinovosamine in the three other species. PCR of the rRNA interspace region is useful in identification of the genus Brucella, while carbohydrate profiling is capable of differentiating B. canis from the other Brucella species.

Base Sequence↗

Cat scratch disease: the rare role of Afipia felis.

Since its isolation in 1988, Afipia felis has been associated with cat scratch disease (CSD) in only one report and its role in CSD has been questioned. We have cultured A. felis from a lymph node of a patient with CSD. 16S rRNA gene sequencing, DNA relatedness studies, fatty acid analysis, and PCR of the A. felis ferredoxin gene showed that the isolate is identical to the previously reported A. felis isolate. To determine the role of A. felis in CSD, PCR of the 16S rRNA gene followed by hybridizations with specific probes were performed with lymph node specimens from CSD patients. All 32 specimens tested positive for Bartonella henselae and negative for A. felis. We conclude that A. felis is a rare cause of CSD. Diagnostic tests not conducive to the identification of A. felis might cause the diagnosis of CSD due to A. felis to be missed.

Adult↗

Comparison of PCR assays for detection of the agent of human granulocytic ehrlichiosis, Anaplasma phagocytophilum.

Human granulocytic ehrlichiosis is an emerging infectious disease in the United States and Europe, and PCR methods have been shown to be effective for the diagnosis of acute infections. Numerous PCR assays and primer sets have been reported in the literature. The analytical sensitivities (limits of detection) of 13 published PCR primer sets were compared using DNA extracted from serial dilutions of Anaplasma phagocytophilum-infected HL-60 cells. The specificity of the assays that were able to detect <or=2.5 infected cells was tested by the use of template DNA extracted from Ehrlichia chaffeensis, Rickettsia rickettsii, and Bartonella henselae. The assays with the lowest limits of detection were shown to be a nested assay that amplifies the 16S rRNA gene (primer pairs ge3a-ge10 [primary] and ge9-ge3 [nested]; detects 0.25 infected cell), a direct assay that amplifies the major surface protein gene msp2 (primer pair msp2-3f-msp2-3r; detects 0.25 infected cell), and a direct assay that amplifies the 16S rRNA gene (primer pair ehr521-ehr790; detects 0.25 infected cell). The specificity and limit of detection of the MSP2 and 16S rRNA direct assays were further tested by use of A. phagocytophilum template DNA from both North America and Europe and from human, tick, white-footed mouse, equine, deer, bovine, and wood rat samples and of template DNA from closely related species (Anaplasma marginale, the white-tailed deer agent, and additional E. chaffeensis-positive samples). Three manufacturers' PCR kits were tested and showed distinct variations in the limit of detection, specificity, and nonspecific background amplification. The importance of these results for the molecular diagnosis of human granulocytic ehrlichiosis is discussed.

Anaplasma phagocytophilum↗

Molecular diagnosis of infective endocarditis by PCR amplification and direct sequencing of DNA from valve tissue.

We used broad-range eubacterial PCR amplification followed by direct sequencing to identify microbial pathogens in heart valve material from 29 patients with histologically confirmed infective endocarditis and 23 patients free of infective endocarditis. Microorganisms cultured by conventional techniques matched those identified by PCR in 21 cases. PCR alone identified the causative agent in three cases (Streptococcus bovis, Staphylococcus cohnii, and Coxiella burnetii), allowing better patient management. PCR corrected the initial bacteriological diagnosis in three cases (Streptococcus bovis, Streptococcus mutans, and Bartonella henselae). Among the 29 cases of histologically confirmed infective endocarditis, PCR findings were positive in 27 cases and were consistent with the bacterial morphology seen at Gram staining (26 cases) or with the results obtained by immunohistologic analysis with an anti-C. burnetii monoclonal antibody (one case). In two other cases of histologically confirmed infective endocarditis, PCR remained negative in a blood culture-negative case for which no bacteria were seen at histological analysis and in one case with visualization of cocci and blood cultures positive for Enterococcus faecalis. Ten clinical diagnoses of possible infective endocarditis were ruled out by histopathological analysis of the valves and subsequently by PCR. PCR was negative in 13 of the 14 patients in whom infective endocarditis was rejected on clinical grounds; the other patient was found to have Coxiella burnetii infective endocarditis on the basis of PCR and histopathological analysis and was subsequently included in the group of 29 definite cases. In total, PCR contributed to the diagnosis and management of infective endocarditis in 6 of 29 (20%) cases.

DNA, Bacterial↗

Blood agar and Mycobacterium tuberculosis: the end of a dogma.

Incidental blood agar-based recovery of Mycobacterium tuberculosis led us to further investigate this routine medium for primary isolation and culture of M. tuberculosis. Fifteen respiratory tract and eight lymph node Ziehl-Neelsen-positive specimens were inoculated in parallel into tubes containing egg-based medium and 5% sheep blood agar. Colonies appeared sooner on this medium than on the egg-based medium, but this difference was not significant (P = 0.11, analysis of variance [ANOVA] test). Further experiments compared the growth of 38 respiratory and lymph node M. tuberculosis isolates when subcultured on the two media. After 6 days of incubation, 21 of 38 isolates had grown on blood agar, and the mean number of colonies was significantly greater on blood agar than on the egg-based medium (P < 0 0.001, ANOVA test). These results demonstrate that M. tuberculosis grows easily on blood agar within 1to 2 weeks, indicating that this basic medium is suitable for laboratory diagnosis of tuberculosis in addition to other media. Laboratories that routinely use prolonged incubations of blood plates, for example, for the recovery of Bartonella species, should consider the potential safety implications of encountering this highly infectious pathogen.

Agar↗

Multiplex real-time PCR for detection of anaplasma phagocytophilum and Borrelia burgdorferi.

A multiplex real-time PCR assay was developed for the simultaneous detection of Anaplasma phagocytophilum and Borrelia burgdorferi. The assay was tested on various Anaplasma, Borrelia, Erhlichia, and Rickettsia species, as well as on Bartonella henselae and Escherichia coli, and the assay was found to be highly specific for A. phagocytophilum and the Borrelia species tested (B. burgdorferi, B. parkeri, B. andersonii, and B. bissettii). The analytical sensitivity of the assay is comparable to that of previously described nested PCR assays (A. phagocytophilum, 16S rRNA; B. burgdorferi, fla gene), amplifying the equivalent of one-eighth of an A. phagocytophilum-infected cell and 50 borrelia spirochetes. The dynamic range of the assay for both A. phagocytophilum and B. burgdorferi was >/=4 logs of magnitude. Purified DNA from A. phagocytophilum and B. burgdorferi was spiked into DNA extracted from uninfected ticks and from negative control mouse and human bloods, and these background DNAs were shown to have no significant effect on sensitivity or specificity of the assay. The assay was tested on field-collected Ixodes scapularis ticks and shown to have 100% concordance compared to previously described non-probe-based PCR assays. To our knowledge, this is the first report of a real-time multiplex PCR assay that can be used for the simultaneous and rapid screening of samples for A. phagocytophilum and Borrelia species, two of the most common tick-borne infectious agents in the United States.

Anaplasma phagocytophilum↗

Contribution of systematic serological testing in diagnosis of infective endocarditis.

Despite progress with diagnostic criteria, the type and timing of laboratory tests used to diagnose infective endocarditis (IE) have not been standardized. This is especially true with serological testing. Patients with suspected IE were evaluated by a standard diagnostic protocol. This protocol mandated an evaluation of the patients according to the modified Duke criteria and used a battery of laboratory investigations, including three sets of blood cultures and systematic serological testing for Coxiella burnetii, Bartonella spp., Aspergillus spp., Legionella pneumophila, and rheumatoid factor. In addition, cardiac valvular materials obtained at surgery were subjected to a comprehensive diagnostic evaluation, including PCR aimed at documenting the presence of fastidious organisms. The study included 1,998 suspected cases of IE seen over a 9-year period from April 1994 to December 2004 in Marseilles, France. They were evaluated prospectively. A total of 427 (21.4%) patients were diagnosed as having definite endocarditis. Possible endocarditis was diagnosed in 261 (13%) cases. The etiologic diagnosis was established in 397 (93%) cases by blood cultures, serological tests, and examination of the materials obtained from cardiac valves, respectively, in 348 (81.5%), 34 (8%), and 15 (3.5%) definite cases of IE. Concomitant infection with streptococci and C. burnetii was seen in two cases. The results of serological and rheumatoid factor evaluation reclassified 38 (8.9%) possible cases of IE as definite cases. Systematic serological testing improved the performance of the modified Duke criteria and was instrumental in establishing the etiologic diagnosis in 8% (34/427) cases of IE.

Antibodies, Bacterial↗

Histological evidence of disease in wild stoats (Mustela erminea) in England.

Forty-four free-living stoats were collected from five game estates in England and examined for evidence of disease. All the macroscopic lesions were attributable to the trauma associated with being trapped or shot. There were no significant microscopic lesions in 27 (61 per cent) of the stoats. There was evidence of nematode parasitism in the intestines of six stoats (14 per cent), and in the lungs of five stoats (11 per cent), and of pulmonary granulomatous inflammation or microgranulomas in five stoats. In two of the stoats, blood-filled cavities in the liver were suggestive of peliosis hepatis, possibly associated with infection by Bartonella species or with sublethal exposure to anticoagulant rodenticides.

Animals↗

Intracellular pathogens and the actin cytoskeleton.

Many pathogens actively exploit the actin cytoskeleton during infection. This exploitation may take place during entry into mammalian cells after engagement of a receptor and/or as series of signaling events culminating in the engulfment of the microorganism. Although actin rearrangements are a common feature of most internalization events (e.g. entry of Listeria, Salmonella, Shigella, Yersinia, Neisseria, and Bartonella), bacterial and other cellular factors involved in entry are specific to each bacterium. Another step during which pathogens harness the actin cytoskeleton takes place in the cytosol, within which some bacteria (Listeria, Shigella, Rickettsia) or viruses (vaccinia virus) are able to move. Movement is coupled to a polarized actin polymerization process, with the formation of characteristic actin tails. Increasing attention has focused on this phenomenon due to its striking similarity to cellular events occurring at the leading edge of locomoting cells. Thus pathogens are convenient systems in which to study actin cytoskeleton rearrangements in response to stimuli at the plasma membrane or inside cells.

Actins↗

Bacillary angiomatosis in patients with AIDS: multiorgan imaging findings.

PURPOSE: To describe the varied clinical manifestations and imaging findings encountered in bacillary angiomatosis, an infectious complication of the acquired immunodeficiency syndrome (AIDS). MATERIALS AND METHODS: Clinical, imaging, and histopathologic findings in nine men (aged 26-50 years) with AIDS and bacillary angiomatosis were described. This condition often manifests as vascular skin lesions that resemble those of Kaposi sarcoma, fever, and anemia and is due to infection with Bartonella (Rochalimaea) henselae. RESULTS: Common imaging findings included lung nodules, mediastinal adenopathy, peripheral adenopathy, pleural effusions, ascites, abdominal adenopathy, soft-tissue masses, and low-attenuation lesions in the liver and/or spleen. Most notably, nodes and soft-tissue lesions were dramatically enhanced with injection of contrast material, which is presumably because the lesions are composed to a large extent of well-formed capillaries. CONCLUSION: Bacillary angiomatosis, a treatable infection, should be considered in patients with AIDS, particularly when Kaposi sarcoma is suspected clinically.

Acquired Immunodeficiency Syndrome↗