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Biomedical subjects

R A Packer

Publications and source records attributed to R A Packer.

At least 19 recordsLinked to original sources
PubMed1989

Pasteurella caballi, a new species from equine clinical specimens.

The name Pasteurella caballi is proposed for a group of organisms represented by 29 strains isolated from respiratory and other infections in horses. P. caballi strains are gram-negative, oxidase-positive, nonmotile, fermentative rods with the key characteristics of the genus Pasteurella. These strains differed from other Pasteurella species in that all were aerogenic and catalase negative, and some strains produced acid from myo-inositol and L-rhamnose. The levels of DNA relatedness of 28 P. caballi strains with labeled DNA from the proposed type strain averaged 91 and 85% (hydroxyapatite method at 55 and 70 degrees C). P. caballi was 13 to 53% related to strains representing 22 other species of the family Pasteurellaceae. The guanine-plus-cytosine content of the DNA of four strains was 41 to 42 mol%. The type strain is 83851 (=ATCC 49197).

Animals↗
PubMed1984

Biochemical and serologic properties of Escherichia coli isolated from cows with acute mastitis.

Biochemical and serologic characteristics of 184 Escherichia coli isolates from cows with acute mastitis were determined. Trends or patterns unique to bovine isolates were not observed, except for the frequency of adonitol fermentation, which was positive in 84 (45.6%) of the cultures. Growth on Tergitol-7 agar had 3 types of colony morphologic characteristics; of these, the rough and intermediate textures predominated over those with smooth colony surfaces. A large variety of serovars was detected; the majority occurring as single isolates within a herd. Few K antigens were typeable. Only 2 isolates contained the K99 antigen. Seemingly, E coli organisms isolated from cows with acute mastitis cannot be distinguished as a specific pathogenic group on the basis of biochemical and serotest reactions.

Acute Disease↗
PubMed1984

Virulence factors of Escherichia coli isolated from cows with acute mastitis.

A total of 184 Escherichia coli isolates recovered from cows with acute mastitis were examined for recognized pathogenic mechanisms and virulence factors commonly found in pathogenic groups of E coli. A modification of the Eng procedure (for detecting complement deficiencies in serum) was used to test for resistance to different animal sera. The Sereny test (for invasiveness), infant mouse test (for heat-stable enterotoxin), and Y-1 adrenal tumor cell assay (for heat-labile enterotoxin) were used. Hemagglutination tests, using rabbit, sheep, and guinea pig RBC, were done with and without added mannose. All of the 184 isolates were serum resistant in all tested sera. None of the isolates was invasive. Only 1 isolate was positive for heat-stable enterotoxin and 2 cultures were positive for heat-labile enterotoxin. Multiple patterns of hemagglutination were observed. The majority of the isolates exhibited both mannose-sensitive and mannose-resistant hemagglutinins with guinea pig and rabbit RBC. A few strains were positive only in mannose-sensitive or mannose-resistant hemagglutination tests. A few strains were negative in all hemagglutination tests. Based on our results, E. coli from cows with acute mastitis lack the virulence factors commonly observed in other E coli groups associated with disease. Serum resistance was the only characteristic that could be related to virulence.

Acute Disease↗
PubMed1979

Comparison of Pasteurella multocida serotyping systems.

Thirty-two type specific cultures used in four typing systems for serologically classifying Pasteurella multocida were compared as originally described for: (1) Little and Lyon's plate agglutination test; (2) Carter's indirect hemagglutination test, hyaluronidase decapsulation test, and acriflavine reaction; (3) Namioka's plate and tube agglutination tests; and (4) Heddleston's gel diffusion precipitin test. In addition, seven cultures from Robert's five passive protection groups were included. When reference cultures were examined by the typing system from which they were described, the results generally correlated with those results published. However, serotypes determined by one typing system generally did not correlate with serotypes determined by another system. Cultures of a single serotype in one system often represented more than one serotype in another system. Results indicated that cultures with one or two serotyping antigens in common may differ in other antigens. Because of the antigenic complexity of P multocida and the nature of the antigens involved in each test, a reliable correlation or equality between serotypes determined by different typing systems could not be made.

Agglutination Tests↗
PubMed1969

Evaluation of culture media for the isolation of Salmonellae from feces.

A study conducted on 300 fecal samples from a cow and a pig, each artificially contaminated with approximately four Salmonella organisms revealed that, of the three enrichment broths used in conjunction with the three selective media, the maximum number of isolations were obtained with Brilliant Green MacConkey broth (BGMB), followed by those obtained with tetrathionate (TTB), and the least with selenite broth. The combination of BGMB with Brilliant Green-neutral red-lactose agar (BGNRLA), and TTB with desoxycholate citrate agar (DCA) gave an equal number of isolations. Of the three selective media used in conjunction with the three enrichment broths, the maximum number of recoveries were obtained on BGNRLA, followed by those on DCA, and least number of isolations on bismuth sulfite agar (BSA). The combination of selenite F broth-BSA appeared to be somewhat inhibitory for the growth of Salmonella organisms. Of the two selective media combinations, the DCA-BGNRLA combination yielded the highest number of isolations. The use of all three selective media gave still better results. Selenite and tetrathionate broths were found unsuitable for isolating Salmonella choleraesuis from feces. BGMB, containing 100 mug of Brilliant Green per ml, proved to be a useful enrichment medium for the isolation of this organism from cow and pig fecal samples, each inoculated with 16 organisms. Observations recorded seemed to suggest that contaminant bacteria perhaps outgrow and mask S. choleraesuis. An incubation period of 24 to 30 hr was found optimum for the three enrichment broths. A longer period was detrimental in the case of TTB but not with selenite broth and BGMB.

Animals↗