Browse

You are looking at 41 - 50 of 370 items for :

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

Abstract

Objective

To identify consistent relevant mechanisms of small intestinal dysfunction in cats with experimentally induced feline immunodeficiency virus infection (FIV) that developed chronic diarrhea during the time they were being used in studies of pathogenicity and transmission of FIV.

Animals

10 cats.

Procedure

The following investigative tests and techniques were performed on each of the cats: routine hematologic and serum biochemical analyses; urinalysis; fecal parasitologic and microbiologic examinations; breath hydrogen lactulose (BH2LT) and xylose (BH2XT) tests; intestinal permeability test; endoscopic examination of the intestinal mucosa; bacteriologic culture of endoscopically collected small intestinal juice; and histologic examination of endoscopically obtained intestinal biopsy specimens.

Results

Neutrophilia was evident in 3 cats, and lymphopenia was detected in 2 cats. Serum biochemical abnormalities were not observed. Urinalysis results were unremarkable. Fecal bacteriologic and parasitologic results were normal, except for isolation of Campylobacter sp from 1 cat. Abnormal BH2XT values suggestive of d-xylose malabsorption were identified in 2 cats, and BH2LT values indicated evidence of small intestinal bacterial overgrowth in 1 cat. Finally, permeability test results, quantitation of bacterial flora from the proximal part of the small intestine and histologic examination of biopsy specimens did not reveal any abnormalities.

Conclusions

Enteric pathogens did not account for the development of diarrhea in cats with experimentally induced FIV infection, and consistent relevant mechanisms of small intestinal dysfunction were not identified. (Am J Vet Res 1998;59:569–574)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To examine Mycoplasma ovipneumoniae for presence of a capsule and its potential role in adherence.

Sample Population

17 isolates of M ovipneumoniae and 2 isolates of M arginini, recovered from sheep with respiratory tract disease.

Procedure

Mycoplasmas were cultured in modified Friis broth medium, ovine fetal lung cells, or ovine tracheal ring explants. Pelleted mycoplasmas or ring cultures infected with mycoplasmas were treated with ruthenium red or polycationic ferritin and visualized by transmission electron microscopy. Reactivity of several lectins with the mycoplasmas was studied by use of a microtitration plate agglutination test.

Results

Electron microscopy revealed a large number of M ovipneumoniae cells covered with an electron dense-stained amorphous material suggesting that it was a capsule. Multiple passages of the microorganisms in modified Friis broth medium decreased thickness of the capsule, but not percentage of cells encapsulated. Marked differences were observed when M ovipneumoniae isolates grown in modified Friis broth medium or co-cultured with ovine fetal lung cells were compared for capsular thickness or percentage of encapsulation. In thin sections of ruthenium red-stained tracheal ring cultures, the mycoplasmas appeared to be in close contact with cilia through their capsule. All isolates of M ovipneumoniae reacted strongly with wheat germ agglutinin lectin.

Conclusions

Mycoplasma ovipneumoniae produces a polysaccharide capsule with variable thickness that is dependent on culture conditions and strain. Morphologic observations suggest that this capsule facilitates adherence of the organism to ciliated epithelium. (Am J Vet Res 1998;59:557–562)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine patterns of cell-associated viremia and antibody responses during the early phase of ovine lentivirus (OvLV) infection in sheep.

Animals

18 neonatal lambs.

Procedures

12 lambs were inoculated intratracheally with OvLV within 24 hours after birth; 6 lambs were inoculated with noninfected cell culture supernatant. Degree of cell-associated viremia was measured every other week for 16 weeks by use of a limited dilution assay. Antibody responses to OvLV transmembrane (TM) and p25 proteins were determined weekly by use of a recombinant ELISA. Neutralizing antibody responses were measured before and 8 and 16 weeks after inoculation.

Results

Degree of cell-associated viremia peaked between 2 and 6 weeks after inoculation and then decreased. For inoculated lambs, mean anti-p25 titer peaked 5 weeks after inoculation then slowly declined, whereas mean anti-TM and neutralizing antibody titers increased steadily. Over time, mean degree of cell-associated viremia was negatively correlated with mean anti-TM titer. Maximum individual degree of cell-associated viremia was positively correlated with maximum individual anti-TM titer.

Conclusions

Results suggest that after experimental inoculation, OvLV replicates actively for several weeks and that an increase in anti-TM titer coincides with a decrease in degree of cell-associated viremia. Although the role antibodies play in protecting against lentivirus infection remains uncertain, understanding the dynamics of the antibody response may have important implications for diagnosis of OvLV infection, and antibodies may prove to be valuable markers for prediction of infection and disease. (Am J Vet Res 1998;59:563–568)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To investigate changes in the duodenal flora of healthy cats over time, and evaluate the effect of dietary supplementation with fructo-oligosaccharides (FOS).

Animals

12 healthy, barrier-maintained, specific pathogen-free cats.

Procedure

Duodenal juice for bacteriologic examination was collected via oral endoscopy 5 times from each cat over a 32-week period. Cats were allotted randomly to 2 groups, and a crossover design study, during which they were fed either a replete dry (basal) diet or, for 12 consecutive weeks, basal diet supplemented with 0.75% FOS, was done. Samples (3 from cats fed the basal and 2 from cats fed the FOS diet) were collected for a minimum of 6 weeks after commencement of feeding, and a minimum of 6 weeks apart.

Results

Mean aerobic, anaerobic, and total bacterial counts did not differ significantly among sample collection times. After pooling of the results, mean (± SD) log10 colony-forming units (CFU) of aerobic, anaerobic, and total bacteria/ml were 5.5 ± 1.1, 4.8 ± 1.0 and 5.6 ± 1.1, respectively. However, individual cats had considerable variation in counts: mean (range) intraindividual coefficients of variation were: 19.0 (6.1 to 34.2), 19.9 (4.8 to 35.5), and 18.1 (5.5 to 32.6)%, respectively. In 1 cat, total bacterial count varied between < 3.0 and 6.3 CFU/ml. Bacterial flora varied qualitatively: only Enterococcus faecalis, Clostridium perfringens, Bacteroides, Pasteurella, and Streptococcus spp, and unidentified gram-negative (aerobic) rods were present in > 50% of the samples.

Conclusions

Wide quantitative and qualitative variation in the duodenal flora of healthy cats was observed over time, which was not affected by dietary supplementation with FOS. (Am J Vet Res 1998;59:431–435)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To develop a unique strain of Pasteurella haemolytica, selectable from nasopharyngeal respiratory tract secretions, that retains the ability to efficiently colonize the respiratory tract of calves.

Animals

26 calves that each weighed approximately 200 kg.

Procedure

Rifampicin-resistant mutants of P haemolytica were developed and tested for in vitro growth rate and leukotoxin production. After instillation into the tonsils of calves, an isolate that was efficient at colonizing was selected and transformed, using electroporation, with a 4.2-kilobase (kb) plasmid encoding for streptomycin resistance. This isolate was instilled into the tonsils of 4 of 14 commingled calves to examine transmission of organisms. Nasal secretion and tonsil wash specimens were collected, cultured, and examined for P haemolytica. Serum antibody concentration was measured by means of indirect hemagglutination.

Results

Selected P haemolytica organisms colonized the tonsils and nasal passages for more than 2 weeks. Exposed calves and contact calves shed the organism, which was recovered from specimens of nasal secretions and tonsil washes. The 4.2-kb plasmid was lost during in vivo colonization.

Conclusions and Clinical Relevance

The selected rifampicin-resistant P haemolytica organism colonized tonsils and nasal passages in a manner similar to the wild-type organisms. Selective media suppressed other bacterial flora to the extent that a single colony-forming unit was detectable from 200 μl of specimen, a 100-fold improvement in detection sensitivity. The selectable strain spread rapidly among commingled calves. A 4.2-kb plasmid marker was unstable when P haemolytica replicated in vivo. (Am J Vet Res 1998;59:426–430)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To investigate changes in the fecal flora of healthy cats after dietary supplementation with fructo-oligosaccharides (FOS).

Animals

12 healthy, barrier-maintained, specific-pathogen-free-derived adult cats.

Procedure

Fresh fecal samples for quantitative and qualitative bacteriologic examination were collected from each cat after ingestion of a replete dry (basal) diet for a minimum of 8 weeks. The diet was then supplemented with 0.75% FOS, and another fecal sample was collected after 12 weeks.

Results

Mean ± SD fecal aerobic, anaerobic, and total bacterial counts (log10 colony-forming units per gram of feces [CFU/g]) did not differ significantly between diets (8.3 ± 0.8, 9.2 ± 0.6, 9.4 ± 0.4, respectively, for the basal diet; and 8.4 ± 0.8, 9.7 ± 0.7, and 9.8 ± 0.7, respectively, for the FOS diet), although there was a trend for higher numbers of anaerobes and total bacteria associated with the FOS diet. Members of the genus Bacteroides, Clostridium perfringens, Escherichia coli, lactobacilli, and Plesiomonas shigeloides were the most prevalent bacteria isolated. Compared with samples from cats fed basal diet, there was a trend for increased mean counts of lactobacilli (P = 0.02) and Bacteroides spp (P = 0.05) after FOS supplementation, and a trend for decreased mean numbers of Escherichia coli (P = 0.03) and Clostridium perfringens (P = 0.08) to be associated with the FOS diet. Supplementation of FOS resulted in a median 164-fold increase in numbers of lactobacilli, 13.2-fold increase in Bacteroides spp, 98% reduction in numbers of C perfringens, and 75% reduction in numbers of E coli.

Conclusions

Supplementation of the diet with FOS resulted in alteration of the fecal flora of cats. (Am J Vet Res 1998;59:436–440)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To isolate Actinomyces pyogenes and A pyogenes-like (APL) organisms from the ruminal wall and ruminal contents of cattle and compare them with isolates from liver abscesses from the same animals, using ribosomal DNA restriction fragment length polymorphism analysis or ribotyping.

Procedure

Specimens of liver abscesses, ruminal walls, and ruminal contents were collected from 59 cattle at slaughter. All β-hemolytic, pinpoint colonies that were gram positive, pleomorphic rod-shaped, and catalase negative, and that hydrolyzed casein and gelatin were presumptively identified as A pyogenes and were characterized biochemically, using an identification kit. The isolates that resembled A pyogenes but fermented mannitol or raffinose, or both, were called APL organisms. Isolates from the ruminal wall and ruminal contents were compared with liver abscess isolates from the same animal by use of ribotyping.

Results

Actinomyces pyogenes and APL organisms were isolated more frequently from the ruminal wall than from ruminal contents. Ruminal isolates of A pyogenes and APL had biochemical characteristics similar to those of the isolates from liver abscesses. Among 6 sets of isolates (4 A pyogenes and 2 APL), 2 isolates from liver abscesses had ribopatterns identical to the corresponding ruminal wall isolates. Also, the APL organisms isolated from the ruminal content matched with the corresponding liver abscess isolates for both sets of specimens tested.

Conclusions

The ruminal wall may be the niche for A pyogenes and APL organisms in the rumen. The genetic similarity, on the basis of ribotyping among isolates from liver abscesses, the ruminal wall, and ruminal contents of the same animal suggests that A pyogenes and APL organisms that cause liver abscesses originate from the rumen. (Am J Vet Res 1998;59:271–276)

Free access
in American Journal of Veterinary Research

SUMMARY

Objectives

To evaluate in vitro susceptibility to topical antifungal medications, as measured by minimum inhibitory concentration (MIC) and 50% inhibitory concentration (IC50%), of fungal isolates from horses with ulcerative keratomycosis in Florida; to compare results with those of other studies to identify differences in susceptibility patterns among fungi isolated from horses in different geographic regions; and to note indications of fungal resistance to drugs tested in other studies.

Sample Population

Corneal fungal cultures from client-owned horses from Florida with ulcerative keratomycosis (n = 22).

Procedure

Fungal cultures were plated on Emmons modified Sabouraud dextrose agar and mycobiotic agar, examined weekly for growth, and kept for a total of 30 days. In vitro MIC and IC50% of fluconazole, itraconazole, ketoconazole, miconazole, and natamycin were measured for each fungal isolate.

Results

Aspergillus (n = 9; 41%), Fusarium (7; 32%), Penicillium (2; 9%), Cylindrocarpon (1; 4%), Scytalidium (1; 4%), and Torulopsis (1; 4%) spp and an unidentified yeast (1; 4%) were isolated. Fungi were most susceptible to antifungal drugs in the following order: natamycin and miconazole equally, itraconazole, and ketoconazole, although no significant difference was found among drugs. Fungi were significantly less susceptible to fluconazole (P < 0.0001) than to the other 4 drugs.

Conclusions

Initial antifungal therapy with topically applied natamycin, miconazole, itraconazole, or ketoconazole is recommended for ulcerative keratomycosis in horses in the subtropical environment of Florida.

Clinical Relevance

Specific antifungal treatment of horses with ulcerative keratomycosis should be based on history, results of ophthalmic examination, cytologic findings, isolation of the pathogenic fungus, and known prevalence of unique ocular fungi in specific geographic areas. In vitro antifungal susceptibility testing may be most beneficial in aiding documentation of pharmacologic susceptibility patterns of fungi in specific geographic regions. (Am J Vet Res 1998; 59:138–142)

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To determine safety, immunogenicity, and efficacy of an inactivated avian polyomavirus vaccine in nonbudgerigar psittacine birds that varied in age, species, and immunologic status.

Animals

Safety of the vaccine was evaluated in 1,823 psittacines representing more than 80 species. Immunogenicity was evaluated in 285 birds (260 of various Psittaciformes species, 25 chickens). Efficacy was evaluated in 104 birds (78 of various Psittaciformes species, 26 chickens).

Procedures

Safety was evaluated by vaccinating birds that were determined to be seronegative or seropositive (titer > 1:10) prior to vaccination. Birds were then evaluated for clinically detectable systemic or local reactions for 2 months to 2 years. Immunogenicity was evaluated by testing for virus-neutralizing antibodies, vaccinating each bird twice, and then testing for a significant change in antibody titer. Efficacy was evaluated by vaccinating birds, followed in 2 to 4 weeks by intramuscular or intravenous challenge exposure. After challenge exposure, protection was evaluated by attempting to recover virus from tissues or by observing birds for clinical signs of disease and testing for a significant change in titer.

Conclusions

Avian polyomavirus vaccine is safe, immunogenic, and efficacious for use in multiple species of mature and immature psittacines.

Clinical Relevance

Until now, prevention of polyomavirus infection in psittacine birds could only be accomplished through strict isolation to reduce potential exposure to the virus. The USDA-registered inactivated avian polyomavirus vaccine can safely be used to protect vaccinates from infection and control spread of this virus in flocks. (Am J Vet Res 1998,59:143–148)

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To determine the resistance and susceptibility to antimicrobial compounds of Fusobacterium necrophorum isolates from bovine hepatic abscesses.

Procedure

37 isolates of F necrophorum (21 subsp necrophorum and 16 subsp funduliforme) isolated from bovine hepatic abscesses were obtained from cultures grown and maintained in anaerobic brain heart infusion broth. A broth dilution method was used as an initial screening to determine general susceptibility to 31 antimicrobial compounds. The minimal inhibitory concentrations (MIC) of 19 of the antimicrobial compounds that inhibited growth in the initial test were determined by use of the broth microdilution method.

Results

Fusobacterium necrophorum isolates were generally susceptible to penicillins, tetracyclines (chlortetracycline and oxytetracycline), lincosamides (clindamycin and lincomycin), and macrolides (tylosin and erythromycin), and were resistant to aminoglycosides (kanamycin, neomycin, gentamicin, and streptomycin), ionophores (except narasin), and peptides (avoparcin, polymyxin, and thiopeptin). The 5 antimicrobials (bacitracin, chlortetracycline, oxytetracycline, tylosin, and virginiamycin) that have FDA approval for prevention of liver abscesses in feedlot cattle were inhibitory to F necrophorum. Differences in antimicrobial susceptibility patterns were observed between the 2 subspecies only for clindamycin and lincomycin. The MIC of F necrophorum isolates from antibiotic-fed cattle were similar to those for isolates from nonantibiotic-fed cattle.

Conclusions

The MIC of FDA-approved antibiotics were not reflective of the efficacy of antibiotics in preventing liver abscesses in feedlot cattle. Also, continuous feeding of tylosin did not appear to select resistant F necrophorum. (Am J Vet Res 1998;59:44–47)

Free access
in American Journal of Veterinary Research