Biomedical subjects

D W Morck

Publications and source records attributed to D W Morck.

44 records · Page 3Linked to original sources

PubMed1993

Effect of growth conditions on expression and antigenicity of Staphylococcus epidermidis RP62A cell envelope proteins.

Staphylococcus epidermidis RP62A (ATCC 35984) was grown in tryptic soy broth (TSB), iron-depleted TSB (TSB-Fe), iron-reconstituted TSB-Fe (TSB+Fe), a chemically defined medium, and fetal calf serum (FCS) and on silastic disks in chambers that were sutured to the pig peritoneal wall. Bacterial cell wall proteins were extracted by digestion with recombinant lysostaphin, separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and detected by silver staining. Cell wall proteins from TSB-, chemically defined medium-, or FCS-grown cells had a complex profile of greater than 25 protein bands spanning the full molecular mass range. By contrast, a digest obtained from in vivo-grown cells had only five major proteins of 40 kDa or greater. Proteins of 130 and 106 kDa were present in the cell envelopes of TSB-Fe- and in vivo-grown cells but not in those grown in TSB or TSB+Fe. A 43-kDa protein expressed by in vitro-grown cells and 52- and 96-kDa proteins expressed by in vivo-grown cells reacted with antisera from pigs with the chamber implants and from catheterized, paracatheter-inoculated pigs but not with hyperimmune sera from pigs immunized with TSB-grown cells. The data indicate that S. epidermidis, growing under in vivo conditions, expresses antigens distinct from those that are grown in vitro.

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PubMed1992

Flavobacterium indologenes infection in leopard frogs.

An investigation of an epidemic of infectious disease in a frog (Rana pipiens) colony was conducted. Six of 40 frogs in a continuous (once through) water flow housing system had weight loss, swollen abdomen, corneal edema, uveitis, subcutaneous edema, petechial hemorrhage, incoordination, and respiratory distress. The frogs had lesions consistent with bacterial septicemia. A gram-negative, nonfermenting bacillus, Flavobacterium indologenes (Flavobacterium sp biovar IIb), was isolated in pure culture from tissues and blood. The clinical isolate was used to inoculate healthy frogs sc. An isolate identical to the one isolated from the sick frogs was recovered from tissues and blood of the inoculated frogs. Inoculation of the housing water in a nonflow-through system did not result in disease, despite proliferation of the Flavobacterium spp in the water; therefore, it is likely that establishment of infection requires the presence of the organism in sufficient numbers and a portal of entry into the body.

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PubMed1991

In vivo expression of iron regulated outer-membrane proteins in Pasteurella haemolytica-A1.

Pasteurella haemolytica-A1 was grown in vitro under iron-rich conditions, iron-depleted conditions, and in vivo within a chamber implanted in the peritoneal cavity of a rabbit to determine if iron regulated outer-membrane proteins were expressed in vivo. The antigenicity of outer membrane (OM) proteins from bacteria grown under these conditions was assessed by immunoblotting with pooled serum from convalescent bovine calves experimentally infected with P. haemolytica-A1 and serum from the implanted rabbit. Pasteurella haemolytica-A1 grown under iron-depleted conditions showed three distinct OM protein bands (71, 77, and 100 kDa) that were present in much lesser amounts when the organism was grown under iron-rich conditions. These same three bands were evident in OM protein preparations from bacteria grown in vivo. Western blotting indicated that these protein bands were recognized immunologically by the convalescent bovine serum and by serum from the implanted rabbit, in cells grown under the iron-depleted conditions and in vivo, but not if the bacteria were grown under the in vitro iron-rich conditions.

Animals↗

PubMed1990

A guinea pig model of bovine pneumonic pasteurellosis.

The induction of pneumonic pasteurellosis in guinea pigs (Cavia porcellus) was examined. Specific pathogen free male guinea pigs were anesthetized and a tracheostomy performed to introduce 10(5), 10(4) or 10(3) Pasteurella haemolytica-A1 into the left principal bronchus. The surgical site was closed with tissue adhesive and staples and the animals were monitored for signs of respiratory tract infection. Within 24 hours after inoculation they became depressed, anorectic, pyretic and dyspneic. Fibrinous pleuropneumonia with prominent areas of necrosis and hemorrhage was present. Pericardial effusion was a frequent finding. There was infiltration of the pleura and alveoli with degenerate heterophils and macrophages, a hyperplastic mesothelium and fibrin exudation on the pleura and within alveoli. Hemorrhage, congestion, consolidation, edema and fibrin exudation were prominent in the hilar region of the lungs. Bacterial colonies were evident in all airways. More bacteria were recovered from infected lungs than were inoculated (p less than 0.05) indicating P. haemolytica was actively multiplying in the lungs. Hematological and clinical chemistry data were consistent with fibrinous pneumonia, however, blood cultures were positive for P. haemolytica in 61% (11/18) of animals sampled. Examination of pneumonic pasteurellosis in guinea pigs may be useful in studying pathogenetic and pathological features applicable to bovine pneumonic pasteurellosis (shipping fever pneumonia).

Animals↗

PubMed1989

Amdinocillin treatment of catheter-associated bacteriuria in rabbits.

The effect of the beta-lactam antibiotic, amdinocillin, on the bacterial biofilm adherent to the Foley catheter surface, the bacterial microcolonies attached to the urinary bladder mucosa, and on planktonic bacteria in the urine was studied in a rabbit model of the closed urinary catheter drainage system. Progressively increasing the dose of antibiotic in this experimental catheter-associated urinary tract infection model first eliminated the bacterial population adherent to the bladder mucosa and then the planktonic population in the urine. The bacterial biofilm on the Foley catheter could be eradicated only by the highest dose of antibiotic (400 mg/kg). Scanning electron microscopy showed a gradual deterioration of bacterial biofilm and reduction in bacterial numbers with increasing antibiotic dosages. These data suggest that antibiotics used in short-term catheterization may reduce the serious sequelae associated with catheter-related infections by clearing the potentially dangerous bladder mucosal bacterial populations and urine planktonic bacteria.

Amdinocillin↗

PubMed1989

Presence of bacterial glycocalyx and fimbriae on Pasteurella haemolytica in feedlot cattle with pneumonic pasteurellosis.

This investigation was conducted to determine if Pasteurella haemolytica within feedlot cattle affected by pneumonic pasteurellosis express fimbriae (pili) and bacterial glycocalyx. Bacteriological culture of pulmonary tissue from three calves with fibrinous pneumonia resulted in heavy growth of P. haemolytica. Transmission electron microscopy of the lungs showed numerous microcolonies of gram-negative bacteria with morphology typical of Pasteurella haemolytica. The cells within these microcolonies possessed bacterial glycocalyces which stained with ruthenium red. Glycocalyx-encased microcolonies were also present in specimens examined by scanning electron microscopy. Typical P. haemolytica cells were evident in a tracheal specimen and these bacteria had radial glycocalyces consistent with polysaccharide and proteinaceous material condensed on linear structures suggestive of fimbriae. The pathogenetic importance of the bacterial glycocalyx and fimbriae in shipping fever pneumonia has yet to be established but their presence in clinical cases of Pasteurella pneumonia in feedlot cattle further supports a possible role in the initiation and progression of this disease as well as bacterial resistance to antimicrobial agents.

Animals↗

PubMed1988

Electron microscopic examination of cells of Pasteurella haemolytica-A1 in experimentally infected cattle.

Several modern electron microscopy techniques were used to examine Pasteurella haemolytica (biotype A, serotype 1) (strain B122) recovered from experimentally infected cattle and in situ within the lung tissue of experimentally infected cattle. Glycocalyx four to five times thicker than that seen on P. haemolytica grown in vitro was evident on bacterial cells recovered from live infected calves by pulmonary lavage. Fimbriae were also present on cells recovered by lavage. A thick glycocalyx was also seen on P. haemolytica-A1 within the lungs of experimentally infected cattle at necropsy. In summary, cells of P. haemolytica-A1 in experimentally infected cattle have fimbriae and glycocalyx on their cell surfaces and these structures appear to be important in bacterial colonization of the bovine respiratory tract and pathogenesis of shipping fever (Pasteurella) pneumonia.

Animals↗

PubMed1987

Electron microscopic description of glycocalyx and fimbriae on the surface of Pasteurella haemolytica-A1.

Several electron microscopic techniques were used to examine the surface of cells of Pasteurella haemolytica (biotype A, serotype 1) grown in vitro. All methods showed the presence of a very extensive glycocalyx on logarithmic phase (6 h) cells grown in liquid media. The anionic glycocalyx of these cells stained well with ruthenium red, but collapsed during dehydration for electron microscopy unless stabilized with specific antibodies. When the same techniques were used to examine cells in the stationary phase (18 h) the glycocalyx was much reduced. Large numbers of fimbriae were seen on both 6 h and 18 h cells grown in fluid media without shaking. In summary, logarithmic phase cells of P. haemolytica have both fimbriae and extensive anionic glycocalyx at their surface and we suggest that either or both of these structures may be important in the colonization of the bovine respiratory tract and the subsequent pathogenesis of Pasteurella pneumonia.

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