OBJECTIVE To evaluate a hypervariable octameric oligonucleotide fingerprints (HOOF-Prints) assay for identification of and discrimination between wild-type and vaccine strains of Brucella melitensis.
SAMPLEBrucella melitensis vaccine strain M5 and wild-type strain M43.
PROCEDURES 8 pairs of primers (alterable, octameric nucleotides) were designed on the basis of a biological analysis of 8 flanking sequences in the DNA of B melitensis. The HOOF-Prints technique was used to identify wild-type and vaccine strains of B melitensis. Phylogenetic analysis of short, polymorphic fragments of DNA from B melitensis strains M5 and M43 was performed.
RESULTS Variable-number tandem repeat DNA segments of B melitensis vaccine strain M5 and wild-type strain M43 were successfully amplified by means of PCR assay. All target gene fragments ranged in size from 100 to 300 bp. Separate phylogenetic analysis of each Brucella strain revealed considerable differences between the vaccine and wild-type strains.
CONCLUSIONS AND CLINICAL RELEVANCE The results of this study suggested the HOOF-Prints assay may be useful for discriminating vaccine strains of B melitensis from wild-type strains. This ability could allow discrimination between animals that are seropositive because of vaccination against B melitensis and those that are seropositive because of B melitensis infection and could decrease the likelihood of importing Brucella-infected animals.
Objective—To determine whether isolation and virulence
of Rhodococcus equi from soil and infected
foals are associated with clinical disease.
Design—Cross-sectional and case-control study.
Sample Population—R equi isolates from 50 foals
with pneumonia and soil samples from 33 farms with
and 33 farms without a history of R equi infection
(affected and control, respectively).
Procedure—R equi was selectively isolated from soil
samples. Soil and clinical isolates were evaluated for
virulence-associated protein antigen plasmids (VapAP)
and resistance to the β-lactam antibiotics penicillin
G and cephalothin. Microbiologic cultures and VapA-P
assays were performed at 2 independent laboratories.
Results—VapA-P was detected in 49 of 50 (98%) clinical
isolates; there was complete agreement between
laboratories. Rhodococcus equi was isolated from soil
on 28 of 33 (84.8%) affected farms and 24 of 33
(72.7%) control farms, but there was poor agreement
between laboratories. Virulence-associated protein
antigen plasmids were detected on 14 of 66 (21.2%)
farms by either laboratory, but results agreed for only
1 of the 14 VapA-P-positive farms. We did not detect
significant associations between disease status and
isolation of R equi from soil, detection of VapA-P in soil
isolates, or resistance of soil isolates to β-lactam
antibiotics. No association between β-lactam antibiotic
resistance and presence of VapA-P was detected.
Conclusions and Clinical Relevance—On the basis of
soil microbiologic culture and VapA-P assay results, it is
not possible to determine whether foals on a given farm
are at increased risk of developing disease caused by R
equi. (J Am Vet Med Assoc 2000;217:220–225)