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SUMMARY

Four colostrum-deprived calves each were immunized passively with antisera to whole Pasteurella haemolytica, leukotoxin-containing supernatants of P haemolytica, P haemolytica lipopolysaccharide, or newborn calf serum. Calves were challenge exposed intrabronchially with 5 × 109 P haemolytica, and 24 hours later, the resulting lesions were evaluated. The greatest protection against challenge exposure was provided by the antiserum to whole P haemolytica (lesion score = 6.3), whereas newborn calf serum provided the least protection (lesion score = 28.3). Calves that received antiserum to P haemolytica supernatants were moderately protected (lesion score = 16.3), and the antiserum to lipopolysaccharide provided minimal protection (lesion score = 21.8). Antibodies that were unique to whole P haemolytica antiserum and produced dense bands on immunoblots were detected to antigens at 66, 50, and 30 kd. Antibodies in the supernatant preparation that produced prominent bands reacted to antigens between 100 and 90 kd. Collectively, antibodies to these antigens may be responsible for enhancing resistance to experimentally induced pneumonic pasteurellosis. Antibodies to antigens in P haemolytica lipopolysaccharide provided little to no protection.

Free access
in American Journal of Veterinary Research

SUMMARY

Two indirect elisa containing outer membrane protein (omp) and lipopolysaccharide (lps) antigens from a field isolate of Salmonella choleraesuis var kunzendorf developed and evaluated in experimentally infected and uninfected control pigs. Experimentally induced infection with S choleraesuis was successfully established in 10 pigs by oral inoculation with 108 organisms, and 3 pigs died of clinical salmonellosis at postinoculation (pi) weeks 1, 2, and 4. Swab specimens from tonsils, nostrils, and rectum of pigs were obtained for culture, and sera were evaluated at weekly intervals for 9 weeks after inoculation. The elisa containing omp and lps antigens with either anti-swine IgG or protein albumin-to-globulin ratio (antiglobulin) conjugates were standardized for serologic evaluation. All 4 elisa (2 omp and 2 lps) detected seroconversion by pi week 3 and had sensitivities and specificities of 97.8 and 88.8, 100 and 100, 95.6 and 88.8, and 93.3 and 72.5%, at their ideal cutoff points (negative mean optical density + 2 sd). There was excellent agreement between all 4 elisa systems as determined by kappa values. Cultures of fecal, tonsil, and nasal swab specimens were positive for S choleraesuis until the fourth week of infection. Fecal swab specimens from 1 pig were positive for S choleraesuis until pl week 7. Persistent infection after antemortem culture results were negative was detected by all 4 elisa, which indicated consistently high titers until the end of pi week 9. Conventional bacteriologic examination of intestines, mesenteric lymph nodes, bone marrow, lung, liver, spleen, and bile yielded positive results for S choleraesuis in the 3 pigs that died of clinical infection, whereas results were negative in the other 7 pigs infected by the end of pl week 9. Histologic examination of lung, liver, spleen, intestines, and mesenteric lymph nodes from the 3 pigs that died of S choleraesuis infection revealed severe ulceration and inflammatory cell infiltration in the lamina propria and submucosa of the intestine, whereas minimal changes were observed in other organs.

Free access
in American Journal of Veterinary Research

SUMMARY

The efficacy of 23 disinfectants (including the most commonly used chemical groups) and 6 quaternary ammonium compound based commercial formulations against Actinobacillus pleuropneumoniae serotype 1 (ATCC 4074) was studied. The organisms were tested in suspension and carrier tests with serum as the organic matter. Chloramine-T, hydrogen peroxide, glutaraldehyde, and mercurochrome alone, and a quaternary ammonium compound formulation containing 10% benzalkonium chloride, 2.5% glutaraldehyde, 6.8% glyoxal, and 6% formaldehyde were effective in all tests, regardless of the presence or absence of organic load. All but 2 of the nonformulated disinfectants (sodium hypochlorite and an iodophor) caused at least a 3-log10 reduction in colony-forming units in the suspension test. However, most of the disinfectants were not as effective in the carrier test as in the suspension test; this difference ranged from a 1- to 5-log10 reduction in colony-forming units. In addition, the presence of serum considerably reduced the disinfectant capacities of most of the compounds tested, particularly in the carrier test. These results indicate the importance of selecting suitable disinfectants for routine use on surfaces contaminated with this organism, especially in the presence of organic matter. Chloramine-T and the aforementioned commercial formulation were also tested directly under field conditions in pig nurseries, confirming their high effectiveness.

Free access
in American Journal of Veterinary Research

SUMMARY

A virologic survey was conducted on calves with diarrhea associated with bovine rotavirus (brv) on a closed dairy farm. The brv was detected from 32 of 219 (14.6%) fecal specimens repeatedly collected from 56 calves born during the years 1992-1993, regardless of whether they had diarrhea. Most of the 32 strains were isolated from fecal specimens obtained from 2- to 6-week-old calves. After electrophoresis of double-stranded viral rna from the 32 strains, genomic rna migration patterns were similar to those of the predominant brv strains isolated at the same farm during the years 1990-1991. All representative strains were identified as G serotype 6 (G6) and P type 5 (P5) by results of the virus-neutralization test and polymerase chain reaction procedure. Thus, brv had no change in genomic rna electropherotypes and serologic antigenicities in a closed dairy herd over a period of several years.

Free access
in American Journal of Veterinary Research

SUMMARY

The Cooper isolate of bovine herpesvirus 1 (bhv-1) was used to produce a thymidine kinase-negative ( tk ) recombinant by insertion of a β-galactosidase (bgal) expression cassette into the tk coding region. The recombinant virus (tk bgal+) was tested for abortifacient activity in cattle by inoculation of 5 pregnant heifers at 25 to 29 weeks gestation. Five additional heifers were inoculated with the Cooper tk positive ( tk +) virus to serve as controls. After inoculation, both groups of heifers developed similar febrile responses and neutralizing antibody titers. Virus was isolated from blood of all heifers during the first postinoculation (pi) week, and isolation frequencies were similar for both groups. In contrast, whereas virus was isolated from many of the nasal and vaginal swab specimens of heifers inoculated with tk + virus, only rare virus isolations were made from the heifers given tk bgal+ virus. All heifers inoculated with tk + virus aborted between pidays 19 and 35. The finding of characteristic microscopic lesions and viral antigen in fetal tissues indicated that the abortions were caused by bhv-1 infection. Virus was isolated from 3 fetuses, and all isolates were tk +. Two heifers inoculated with tk bgal+ virus aborted at PI days 25 and 39. Fetal tissues had typical bhv-1 microscopic lesions and viral antigen. Virus was isolated from blood of both fetuses, and the isolates were tk bgal+. Results of this study indicate that inactivation of the tk gene reduces, but does not eliminate, the abortifacient activity of bhv-1.

Free access
in American Journal of Veterinary Research

SUMMARY

A rifampicin-resistant Pasteurella haemolytica serotype 1 with 2 added plasmids was used as a colonization-challenge strain in calves to test the resistance to colonization elicited by vaccination. Nine calves were vaccinated with a tissue culture-derived P haemolytica serotype-1 vaccine which, in a prior study, had elicited a serotype-specific inhibition of nasal and tonsillar colonization by the homologous serotype under field conditions. The vaccinates and 9 nonvaccinated control calves were exposed by tonsillar instillation with the challenge strain. The P haemolytica were enumerated in nasal secretion and tonsil wash specimens collected biweekly for 3 weeks. Rifampicin-supplemented agar medium inhibited growth of other bacterial species in the specimens and, thus, increased the sensitivity of detection of the challenge P haemolytica by 100-fold. The challenge strain retained its plasmids during the period of colonization. Inhibition of colonization was evidenced by lower frequency of isolations and fewer isolations of the challenge strain from nasal secretion and tonsil wash specimens of the vaccinates than from those of the nonvaccinates.

Free access
in American Journal of Veterinary Research

SUMMARY

The effect that topical administration of cyclosporine would have on the number and type of microorganisms isolated from the corneal surface of dogs with keratoconjunctivitis sicca was studied. Schirmer tear tests were performed on and corneal swab specimens were collected from 61 eyes of 31 dogs with keratoconjunctivitis sicca prior to and after 3, 6, and 12 months of treatment with cyclosporine.

In eyes that responded to cyclosporine treatment (Schirmer tear test value increased by ≥ 5 mm/min, compared with pretreatment value), the percentage of eyes from which bacteria were isolated after 3, 6, and 12 months of treatment was significantly (P < 0.001) less than the percentage from which bacteria were isolated prior to treatment. However, among eyes that did not respond to treatment, we did not detect a significant change over time in prevalence of bacteria or type of bacteria isolated. The percentage of eyes from which fungi were isolated decreased during treatment; however, the small number of eyes in which fungal culture results were initially positive precluded demonstration of a significant change. For all eyes, we did not detect any significant differences over time in the frequency with which specific bacterial genera were isolated, with the exception of β-hemolytic Streptococcus spp.

Opportunistic comeal infections were not detected even though none of the dogs received antibiotics. An increase in production of tears, which contain anti-infection proteins, was believed to be the primary factor responsible for the decrease in the percentage of eyes from which microorganisms could be isolated.

Free access
in American Journal of Veterinary Research

SUMMARY

Administration of an N-lauroylsarcosine-derived outer membrane protein fraction of Pasteurella haemolytica A1 (sci-1) induced a protective response in calves against intrathoracic challenge exposure with the homologous serovar. Outer membrane proteins from heterologous serovars, A6 and A9, induced partial protection that was associated with their respective similarities to serovar A1 in outer membrane protein profiles derived by use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Calves vaccinated with sci preparations did not have detectable neutralizing antibody to P haemolytica A1 leukotoxin. Antibodies to whole-cell antigens, carbohydrate-protein subunit antigen, and sci-1 were associated with resistance, which indicates that protein antigens shared among cell surface, carbohydrate-protein subunit, and sci preparations are immunogenic and enhance resistance to experimental challenge exposure.

Free access
in American Journal of Veterinary Research

SUMMARY

Colostrum-deprived calves (n = 24) were fed various amounts of colostrum, colostrum substitute, or milk replacer to establish a range in titer of passively acquired viral neutralizing antibody in serum. The calves were then challenge exposed intranasally with a virulent, noncytopathic bovine viral diarrhea virus (bvdv-890). After viral challenge exposure, calves were monitored for fever, leukopenia, thrombocytopenia, and diarrhea. In addition, viral isolation and viral titration were performed on specimens of nasal secretions, buffy coat cells, and serum obtained from the calves. Fever and systemic spread of virus were detected in calves that had viral neutralizing titer of 256 or lower. Calves that had viral neutralizing titer lower than 16 developed severe clinical disease manifested by fever, leukopenia, thrombocytopenia, and diarrhea. Severity and duration of signs of disease decreased as titers of passively acquired viral neutralizing antibody increased. These results indicate that low to intermediate titers of passively acquired viral neutralizing antibody were not sufficient to fully protect calves from virulent bovine viral diarrhea virus.

Free access
in American Journal of Veterinary Research

SUMMARY

Bovine immunodeficiency virus (biv), a lentivi- rus, is prevalent in dairy and beef cattle in southeastern United States and may be associated with a lymphoproliferative disease. The mode(s) of biv transmission are undefined. Because artificial insemination is a common practice in dairy production, contaminated stud semen could serve as an important source of infection if the virus is harbored in seminal fluids. To evaluate this possibility, we procured 11 cryopreserved semen specimens from a stud semen repository. Leukocytes were purified from the specimens, and the leukocyte dna was used as template in a polymerase chain reaction procedure that targeted a 235-base pair, highly conserved domain of the biv pol gene. The target sequence was amplified from the seminal leukocyte dna of 9 of the specimens (82%), and nucleotide sequencing confirmed the biv specificity of the fragment. This finding provides evidence that stud bull semen may serve as an important reservoir of biv, suggesting the possibility that artificial insemination of dairy cows may have a major role in transmission and wide-spread dissemination of this bovine lentivirus.

Free access
in American Journal of Veterinary Research