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Biomedical subjects

D F Welch

Publications and source records attributed to D F Welch.

8 recordsLinked to original sources
PubMed1992

Immunocytochemical identification of Rochalimaea henselae in bacillary (epithelioid) angiomatosis, parenchymal bacillary peliosis, and persistent fever with bacteremia.

We report the immunocytochemical identification of Rochalimaea henselae, a newly recognized fastidious, Gram-negative, Warthin-Starry-positive organism, as the common pathogen in bacillary angiomatosis (BA), bacillary peliosis (BP) of the liver and spleen, and persistent fever with bacteremia in immunocompromised patients. Immunogenic proteins of the R. henselae strain isolated from the blood of a febrile immunocompromised patient with BP of the liver were used to produce primary immune serum in rabbits. Using immunocytochemical procedures, the polyclonal antiserum reacted strongly not only with the immunizing strain of the bacteria, but also with other blood isolates of R. henselae (five cases) from both immunocompromised and immunocompetent patients and with the organisms present in the tissue lesions of cutaneous BA (five cases) and BP of the liver (two cases) and spleen (one case). The blood isolates and BA and BP tissue samples were obtained from widely separated geographic areas. The antiserum was weakly cross-reactive with cultures of Rochalimaea quintana, an organism closely related to R. henselae, but this reactivity was eliminated by specific adsorption. The antiserum did not cross-react with the Warthin-Starry-positive organisms associated with cat scratch disease (Afipia felis), syphilis (Treponema pallidum), Lyme disease (Borrelia burgdorferi) or chronic active gastritis (Helicobacter pylori). Likewise, the antiserum did not identify organisms in eight cases of Kaposi's sarcoma, a disorder of immunocompromised patients that is clinically similar to BA. Further studies are needed to determine the prevalence of this newly recognized organism as well as its possible involvement in other angioproliferative diseases.

Acquired Immunodeficiency Syndrome↗
PubMed1992

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↗
PubMed1992

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↗
PubMed1992

Rochalimaea henselae causes bacillary angiomatosis and peliosis hepatis.

BACKGROUND: Recent studies have demonstrated that a newly described agent of persistent bacteremia, Rochalimaea henselae, and the agent of bacillary angiomatosis are both closely related to Rochalimaea quintana. Bacillary peliosis hepatis seemed likely to have the same etiologic agent as bacillary angiomatosis. We sought these pathologic changes in patients from whom R henselae was cultivated. METHODS: For two patients whose histopathologic findings we reviewed, additional light and electron microscopy were performed. Their bacterial isolates were compared by electrophoretic patterns of outer membrane proteins, restriction endonuclease digestion patterns of DNA, and reaction with murine antiserum. RESULTS: A previously reported human immunodeficiency virus-infected man with persistent bacteremia due to R henselae was found to have bacillary peliosis hepatis. Rochalimaea henselae was also isolated from the spleen of a woman receiving immunosuppressive therapy after allogeneic renal transplantation. She had developed fever, liver and spleen nodules, and periaortic lymphadenopathy. Bacillary peliosis of her liver and spleen, as well as bacillary angiomatosis of liver, spleen, and a lymph node, were found. The bacterial isolates had comparable electrophoretic patterns of outer membrane proteins and of restriction endonuclease-digested DNA, which differed from the respective patterns of R quintana. Murine antisera raised to the first isolate reacted strongly with the second by means of immunoblot and immunofluorescence techniques, while reacting only weakly with R quintana. CONCLUSION: Rochalimaea henselae, recently recognized to cause persistent fever and bacteremia in immunocompetent and immunocompromised persons, also causes bacillary angiomatosis and parenchymal bacillary peliosis.

Acquired Immunodeficiency Syndrome↗
PubMed1979

Antimicrobial susceptibility testing of Mycobacterium fortuitum complex.

A total of 24 strains of the Mycobacterium fortuitum complex were tested for susceptibility to antimicrobial agents by the disk diffusion and agar dilution techniques. By comparing zones of inhibition obtained with the disk diffusion technique with results of minimal inhibitory concentration determinations, it was shown that disk diffusion results could predict in vitro susceptibility to selected antimicrobial agents. All of 17 strains of M. fortuitum were susceptible to </=1 mug of amikacin per ml. The corresponding average zone of inhibition around a 10-mug amikacin disk was 37 mm. Seven M. chelonei strains were more resistant to amikacin, with minimal inhibitory concentrations ranging from 1 to 32 mug/ml, and the corresponding average zone size was 21 mm. Susceptibility of both M. fortuitum and M. chelonei to tetracycline was variable and none of the M. chelonei strains was inhibited by polymyxin B, whereas M. fortuitum strains consistently had zones of inhibition around the polymyxin disk. It appears that identification to species of the M. fortuitum complex may be of importance with regard to antibiotic susceptibility. Separation of M. fortuitum and M. chelonei was readily accomplished in the present study by the nitrate reduction and 3-day arylsulfatase tests.

Aminoglycosides↗
PubMed1979

Relationship between superoxide dismutase and pathogenic mechanisms of Listeria monocytogenes.

Listeria monocytogenes was examined for superoxide dismutase(SOD) activity. Two catalase-negative strains possessed at least twofold greater SOD activities than the catalase-positive L. monocytogenes strains examined. Growth conditions such as aeration and iron concentration influenced the specific activity of SOD obtained from cells cultured in defined media. L. monocytogenes SOD from crude extracts and after partial purification was analyzed by polyacrylamide gel electrophoresis. Iron was associated with the single band of SOD activity detected in the gels. SOD activity appeared to be primarily extracytoplasmic. Survival of organisms in a superoxide-generating medium was studied, with photoactivation of riboflavin used as the source of free radical formation. Virulent, catalase-positive L. monocytogenes strains were relatively resistant to killing in a pH 7 superoxide-containing medium. An intact-cell assay for SOD was developed, which used the superoxide-generating system and employed the superoxide-dependent oxidation of sulfite, added to the medium, and inhibition of this oxidation by SOD. Maximal SOD activites of intact cells were observed when 100 to 400 micrograms (dry weight) of viable Listeria cells per ml was added to the medium. A possible role for SOD in the pathogenesis of listeric infection is discussed.

Fungal Proteins↗
PubMed1979

Sputum screening by Nomarski interference contrast microscopy.

Gram-stained smears of specimens submitted for sputum cultures were compared with direct wet mounts examined by Nomarski interference contrast microscopy (NIM) for enumeration of squamous epithelial cells (EPC) and leukocytes (WBC). The results obtained by the two methods were comparable, but specimens were more rapidly screened and cell types were more readily differentiated by NIM. Specimens submitted for sputum culture over a 3-month period were examined for EPC and WBC by NIM. Twenty-two percent of the specimens had greater than 25 EPC/field or a predominance of EPC (class I), 30% had greater than 25 EPC and greater than 25 WBC/field (class II), and 48% had greater than 25 WBC/field or a predominance of WBC (class III). The clinical relevance of the culture results was determined by reviewing the records of patients whose specimens were included in the study. Class I specimens provided only 30% clinically relevant culture results. Specimens in class II provided useful culture results in 63% of the patients, and 96% of those in class III provided clinically relevant information. The results confirm the value of sputum screening and demonstrate that NIM provides a rapid, simple, and accurate method for sputum screening.

Diagnosis, Differential↗