Browse

You are looking at 51 - 60 of 370 items for :

  • Microbiology x
  • Refine by Access: All Content x
Clear All

SUMMARY

Objective

To investigate the bacterial flora of the proximal part of the small intestine of healthy cats and determine the effect of sample collection method on results of bacteriologic culture.

Animals

25 healthy barrier-maintained specific-pathogen-free-derived cats.

Procedure

Aspirated, undiluted samples of proximal small intestinal juice were obtained via oral endoscopy (UEA), and a second sample was collected after instillation of 1 ml of sterile saline solution (diluted, DEA). Undiluted juice also was obtained by direct needle aspiration (NA) from the intestinal lumen. Samples for quantitative and semiqualitative bacteriologic examination were grown aerobically and anaerobically.

Results

Mean (range) log10 colony-forming units of total bacteria/ml were 6.2 (2.0 to 8.3) for NA, 6.0 (2.0 to 7.9) for UEA, and 4.9 (2.0 to 7.5) for DEA samples. One cat had no growth (≤ 2.0 colony-forming units/ml) for samples obtained using all 3 methods, and another cat had no growth for the DEA sample only. Mean total aerobic, anaerobic, and bacterial counts were not significantly different between NA and UEA methods, but these techniques yielded significantly higher mean counts than did DEA samples (P ≤ 0.002, ANOVA). As a percentage of the total bacteria isolated, anaerobes constituted a median 35, 32, and 50% of the NA, UEA, and DEA samples, respectively. Good correlation was found between the NA and UEA samples for total bacteria, aerobes, and anaerobes (r ≥ 0.830).

Conclusions

Compared with human beings, healthy cats carry high numbers of bacteria in the proximal part of the small intestine. By comparison with NA samples, UEA samples accurately reflected bacterial populations in the small intestine, whereas DEA samples significantly underestimated these populations. (Am J Vet Res 1998;59:48–51)

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To determine the effect of congenital and early postnatal infection of pigs with porcine reproductive and respiratory syndrome virus (PRRSV) on postnatal survival and growth.

Animals

20 pregnant gilts and their pigs and fetuses.

Procedure

16 pregnant gilts (principals) comprising 4 groups (4 gilts/group) were exposed oronasally to 4 strains of PRRSV (a vaccine strain, and 3 field strains) at or about day 90 of gestation. Four pregnant gilts (controls) were kept under similar conditions, except for exposure to PRRSV. Samples collected from pigs before ingestion of colostrum and samples and specimens collected from pigs at selected times thereafter were tested for PRRSV and homologous antibody. Pigs were observed for clinical signs and were weighed at birth and at weekly intervals until they were euthanatized and necropsied at about 3 weeks of age.

Results

At least some members of all litters of principal gilts were infected congenitally. Most noninfected, liveborn littermates became infected within the first week of life. Infection of pigs with field strains did, and infection of pigs with the vaccine strain did not, adversely affect postnatal survival and growth rate. All infected pigs had generalized lymph node enlargement.

Conclusion

Exposure of pregnant gilts to either attenuated (vaccine) or virulent (field) strains of PRRSV can result in congenital infection. Vaccine as well as field strains can be transmitted postnatally from infected to noninfected littermates. Pigs infected with field strains have a poorer rate of survival and growth than do noninfected pigs.

Clinical Relevance

Because attenuated (vaccine) PRRSV can cause congenital infection and be transmitted postnatally from congenitally infected to immune-naive pigs, the use of attenuated virus during gestation is, at best, questionable. (Am J Vet Res 1998;59:52–55)

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To compare pulsed-field gel electrophoresis (PFGE) patterns of Staphylococcus aureus from chickens in England, Belgium, Bulgaria, Argentina, and Japan, to assess the value of PFGE for discriminating strains, and to compare results obtained by PFGE with those obtained by biotyping and phage typing.

Sample Population

78 S aureus isolates from diseased and healthy chickens.

Procedure

Chromosomal DNA of S aureus was digested with restriction endonuclease Sma l, and fragments were separated by PFGE in 1 % agarose gel.

Results

All 78 strains from 5 countries were classified as poultry ecovar according to a previously established biotyping system. Chromosomal DNA was cut by Sma l into 18 to 23 fragments ranging from about 3 to 685 kb. Seventy-eight strains produced 15 types, arbitrarily designated A to O, and 45 subtypes. Some differences were observed in PFGE patterns among countries. However, 10 fragments (333, 190, 110, 63, 55, 42, 34, 19, 10, and 3 kb) were highly conserved and were shared by almost all (> 78%) of the strains examined. The PFGE patterns were compared with those obtained by phage typing. All 29 strains belonging to avian phage-group II produced type A and 19 subtypes. Of the 15 strains belonging to phage-group I, 11 produced 8 types (B to H, O) and 5 subtypes that were different from those of type A.

Conclusions

Genomic DNA fingerprinting by PFGE is an effective technique for discriminating poultry S aureus strains and appears to be a useful method for subtyping strains of avian phage groups or the poultry-specific ecovar. (Am J Vet Res 1997;58:1412–1416)

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To evaluate the ability of nucleic acid amplification techniques to detect Rhodococcus equi in equine buffy coat, blood, and tracheal wash fluid and to differentiate between virulent and avirulent strains of the bacteria.

Sample Population

Blood anticoagulated with EDTA and tracheal wash fluid from healthy horses.

Procedure

Logarithmic dilutions of virulent and avirulent strains of R equi were added to equine buffy coat and tracheal wash fluid samples. The DNA was extracted and amplified by polymerase chain reaction (PCR), using primers specific for the 16S ribosomal subunit gene and the virulence plasmid of R equi.

Results

PCR with 16S ribosomal subunit primers amplified a 441-bp segment of DNA from virulent and avirulent strains of R equi, but not from samples containing other species of bacteria. The virulence plasmid primers amplified an 875-bp segment of DNA from virulent strains of R equi, but not from avirulent R equi, or from other species of bacteria. Virulent strains of R equi could be identified by PCR and differentiated from avirulent strains within 12 to 24 hours after sample collection, with as few as 10 to 100 organisms present.

Conclusions

PCR can be used to rapidly and accurately identify R equi in equine blood and tracheal wash fluid samples and can differentiate between virulent and avirulent strains of the organism.

Clinical Relevance

Because PCR can confirm a diagnosis of R equi infection in horses more rapidly and specifically than use of standard culture techniques, extrapolation of this assay to soil and fecal samples could be useful in epidemiologic studies and studies of environmental disinfection or decontamination. (Am J Vet Res 1997;58:1232–1237)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To investigate the susceptibility of polarized epithelioid human rectal tumor (HRT-18G) cells to bovine coronaviruses (BCV) isolated from enteric (EBCV) and respiratory (RBCV) tract infections.

Procedure

Cells of the G clone of HRT-18 were grown to confluent monolayers on permeable supports, and were directionally infected at the apical and basolateral domains with 3 wild-type BCV strains, RBCV-LSU-94LSS-051-2, RBCV-OK-0514-3, and EBCV-LY138-2, and 1 cell culture-adapted strain, EBCV-L9-80. Sequential cytopathic changes were microscopically monitored. Medium samples for titration of hemagglutinins and viral infectivity were collected directionally from both domains of the infected cell cultures at various intervals.

Results

Polarized epithelioid HRT-18G cells from apical domains had maximal susceptibility to infection with the EBCV and RBCV strains, and those from basolateral surfaces had minimal susceptibility. Titers of hemagglutinins and infective progeny BCV reached 1,280 hemagglutinin units and 4.2 × 108 plaque-forming units/ml for apical samples, but were minimal for basolateral samples. Asymmetric virus release occurred through the apical surfaces of the HRT-18G cells by 12 hours after infection when cell fusion as a sign of cytopathic changes began. When cells were infected basolaterally, progeny virions released from apical surfaces reinfected the target cells from the apical domains and induced cytopathic changes were delayed about 12 hours, compared with changes detectable in apically exposed cultures.

Conclusions

EBCV and RBCV, isolated from cattle, had marked tropism for polarized epithelioid HRT-18G cells. Entry of BCV into the polarized HRT-18G cells was effected maximally through the apical domains and minimally through the basolateral domains. Release of progeny BCV occurred preferentially from the apical domains. (Am J Vet Res 1997;58:1120–1124)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To identify and compare immunodominant antigens in whole-cell lysates of pressure-and formalin-killed Flexibacter columnaris.

Animals

Sera from naturally infected and vaccinated channel catfish.

Procedures

Whole-cell lysates of pressure- and formalin-killed F columnaris were compared, and antigens were isolated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The antigens were identified by staining, western blotting, and specific monoclonal antibodies to glycoproteins. Western blotting was performed, using sera from channel catfish (Ictalurus punctatus) with naturally acquired F columnaris infection and sera from channel catfish vaccinated with an experimental prototype F columnaris vaccine.

Results

Whole-cell lysates of pressure and formalin-killed F columnaris shared 4 proteins: 100, 80, 66, and 60 kd. The 60-kd antigen was a glycoprotein. Western blotting, using sera from naturally infected channel catfish, revealed the same proteins for pressure- and formalin-killed F columnaris. Sera from vaccinated fish reacted only to pressure-killed lysate antigens.

Conclusions

Pressure- and formalin-killed F columnaris whole-cell lysates share 100-, 80-, 66-, and 60-kd proteins and are recognized by antibodies from naturally infected catfish and those vaccinated with formalin-killed F columnaris. Formalin treatment modifies or inactivates the 60-kd protein antigens, rendering them unrecognizable to antibodies from channel catfish naturally infected with F columnaris, suggesting that formalin-killed F columnaris may not be suitable for use as a bacterin against columnaris disease. (Am J Vet Res 1997;58:985–988)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine the effectiveness of Pasteurella multocida biovar A, serovar 3 (Pm A:3) killed by exposure to UV light and incorporated with a polyacrylate bead carrier as a vaccine.

Animals

18 weanling male Spanish goats.

Procedure

Prospective, randomized controlled study with 3 treatment groups: positive-control (PC), negative-control (NC), and principal Pm A:3 bacterin (PA) groups. Six PC goats each received live Pm A:3 and polyacrylate beads twice, 22 days apart, by transthoracic injection into the left lung. Six NC goats each received only PA beads twice, 22 days apart, by transthoracic injection. Six principal goats each received Pm A:3 vaccine SC twice, 22 days apart. Fourteen days after the second vaccination, all goats were challenge exposed with live Pm A:3 by transthoracic injection into the right lung, and 4 days later they were euthanatized and necropsied.

Results

Mean volume of consolidated lung tissue at the challenge site was 1.75 cm3 for the PC group, 15.18 cm3 for the NC group, and 3.9 cm3 for the PA vaccine group. The NC group had a significantly (P ≤ 0.002) larger mean volume of consolidated lung tissue than did the PC and PA groups after challenge exposure.

Conclusions

The PA bacterin and the PC groups developed protective immunity against live Pm A:3 challenge exposure. An SC administered, UV light-killed, Pm A:3 bacterin induced protective immunity similar to that induced by virulent live Pm A:3 injected into the target organ, the lung. (Am J Vet Res 1997;58:841–847)

Free access
in American Journal of Veterinary Research
Author:

Abstract

Objective

To evaluate the potency of an inactivated animal rabies vaccine for domestic animals by use of 2 types of potency tests after challenge exposure with a laboratory standard virus or 1 of 5 viruses obtained from various wildlife species.

Animals

384 mice vaccinated twice intraperitoneally; 384 mice vaccinated once IM.

Procedure

Mice vaccinated with an inactivated, adjuvanted rabies vaccine for domestic animals were challenge exposed with the common fixed challenge virus or 1 of 5 rabies viruses obtained from wild animal species (street viruses) that most commonly transmit the virus in the United States and Canada. Potency tests included 2 types of antigen extinction tests: the National Institutes of Health (NIH) test and the Centers for Disease Control test.

Results

Results of both tests indicated that protection was highest against raccoon and bat viruses. Marked differences were detected in the relative potency ratios for the NIH versus the Centers for Disease Control tests, though the relative potencies themselves (against the street viruses) did not differ markedly.

Conclusions

The markedly reduced potency against the street viruses indicated by the NIH test results was suggestive of an inherent bias associated with double intraperitoneal vaccination and intracerebral challenge exposure, whereas the single IM vaccination and IM challenge exposure reduced that bias. (Am J Vet Res 1997;58:837–840)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To develop semi-defined media that support growth of the bovine pathogen, Pasteurella haemolytica, and use them to examine production of leukotoxin and an arginine-binding protein by this organism.

Sample Population

10 P haemolytica A1 strains and 1 P multocida strain.

Procedure

Bacterial strains were cultivated at 37 C in media containing various amino acids, carbon sources, vitamins, and cofactors, and absorbance (OD600) was measured. Leukotoxin and arginine-binding protein production were assessed by immunoblot analysis.

Results

Optimal growth required supplementation with 0.1 % fetal bovine serum, gelatin, or purified bovine serum albumin. Calcium pantothenate and thiamine were essential for growth, and a variety of carbon sources could be utilized. In the complete medium, 15 amino acids were included; however, in the minimal medium, no amino acids were required. All strains (except P multocida) grew in the complete medium and 7 grew well in the minimal medium. Leukotoxin was not produced when amino acids were limiting, but could be enhanced by addition of 0.2% NH4SO4. Production of the arginine-binding protein was not affected by nitrogen availability or by presence of L-arginine.

Conclusions

Two media that support good growth of P haemolytica strains were developed. The minimal medium is simple to prepare and manipulate and its use revealed a potential role of nitrogen availability in the regulation of leukotoxin expression.

Clinical Relevance

Creation of these media will permit continued studies of the response of P haemolytica to environmental conditions that may mimic those encountered in the bovine respiratory tract during shipping. (Am J Vet Res 1997;58:749–754)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine whether a humoral response against spirochetes isolated from papillomatous digital dermatitis (PDD) lesions is elicited in dairy cattle affected with PDD.

Sample Population

41 cattle with PDD from 8 dairies (study population) and 30 cattle from 2 dairies free of PDD (control population). Additionally evaluated were 32 cattle from a dairy with a past history of PDD but no current disease, and 52 cattle from a dairy with high prevalence of PDD, 25 with and 27 without detectable lesions.

Procedure

ELISA were used to evaluate the humoral response of all cattle to representative isolates from 2 groups of spirochetes of unknown species isolated from PDD lesions. Specificity of the response was evaluated, using immune sera prepared against each of the spirochetes, and by adsorption studies of immune and field sera. The potential for confounding by an antibody response to other spirochetes associated with diseases of cattle was assessed.

Results

The antibody response (specific) to both PDD spirochete groups of cows with PDD was significantly increased, compared with that of cows from PDD-free dairies. There was no association between antibody response to PDD-associated spirochetes and antibody response to other spirochetal diseases of cattle. None of the cattle from the dairy with previous history of PDD but without current disease were classified as test positive by either PDD ELISA. There was a significant (P < 0.01) difference in classification results for both PDD ELISA for cattle with PDD from the dairy with a high herd prevalence of PDD, compared with cattle without detectable disease from the same dairy.

Conclusions and Clinical Relevance

The humoral response in cattle with PDD lesions was significantly different from that in cattle without detectable lesions, thus providing additional information regarding the potential role of spirochetes isolated from PDD lesions in the etiopathogenesis of PDD. (Am J Vet Res 1997;58:744–748)

Free access
in American Journal of Veterinary Research