Objective—To compare the effects of 2 doses of
cosyntropin (5 µg/kg vs 250 µg, IV) on serum concentrations
of cortisol, sex hormones of adrenal origin,
and adrenocortical steroid intermediates and determine
the optimal sample collection time after adrenal
stimulation with cosyntropin.
Procedure—Dogs were randomly assigned to initially
receive cosyntropin at 5 µg/kg or as a total dose of
250 µg, IV. Dogs received the alternate dose 1 to 2
weeks later. Serum was obtained from blood samples
collected before (0 minutes) and 30, 60, 90, and 120
minutes after cosyntropin administration.
Results—Maximum stimulation of cortisol,
androstenedione, progesterone, and 17-hydroxyprogesterone
production was achieved at 60 minutes following
IV administration of cosyntropin at 5 µg/kg or
as a total dose of 250 µg. Serum estradiol concentration
did not increase in response to either cosyntropin
dose. For all hormones, no significant difference in
serum hormone concentrations was found among
sample collection times of 0, 30, 60, and 90 minutes
when comparing the 2 doses of cosyntropin.
Conclusions and Clinical Relevance—Cosyntropin,
when administered at 5 µg/kg, IV, effectively stimulated
maximum production of cortisol, sex hormones of
adrenal origin, and adrenocortical steroid intermediates
at 1 hour after administration. (Am J Vet Res
Objective—To determine whether the stress of an
ultrasonographic procedure would interfere with the
suppressive effect of dexamethasone during a lowdose
dexamethasone suppression test (LDDST) in
Animals—6 clinically normal adult dogs.
Procedure—In phase 1, an LDDST was performed 5
times at weekly intervals in each dog. Serum samples
were obtained 0, 2, 4, 6, and 8 hours after dexamethasone
injection. A mock 20-minute abdominal ultrasonographic
examination was performed on all dogs at each
time point during the LDDST on weeks 2 through 5. In
phase 2, serum cortisol concentrations were measured
before and immediately after a 20-minute mock
abdominal ultrasonographic examination, as described
for phase 1.
Results—We did not detect significant differences
after dexamethasone injection when comparing
median cortisol concentrations for weeks 2 to 5
(mock ultrasonographic procedure) with median concentration
for week 1 (no mock ultrasonographic procedure).
For 5 of the 6 dogs, cortisol concentrations
after dexamethasone injection decreased to < 35.9
nmol/L after each mock ultrasonographic procedure
and remained low for the duration of the LDDST. In
phase 2, all dogs had significant increases in cortisol
concentrations immediately after the mock ultrasonographic
Conclusions and Clinical Relevance—A 20-minute
mock abdominal ultrasonographic examination performed
during LDDST did not alter results of the
LDDST in most dogs. Cortisol concentrations measured
immediately after a mock ultrasonographic
examination were significantly increased. Ultrasonographic
procedures should be performed a minimum
of 2 hours before collection of samples that will
be used to measure cortisol concentrations. ( Am J Vet Res 2004;65:267–270)
Objective—To evaluate effects of trimethoprim-sulfamethoxazole
(T/SMX) on thyroid function in dogs.
Animals—6 healthy euthyroid dogs.
Procedure—Dogs were administered T/SMX (14.1 to
16 mg/kg, PO, q 12 h) for 3 weeks. Blood was collected
weekly for 6 weeks for determination of total
thyroxine (TT4), free thyroxine (fT4), and canine thyroid-
stimulating hormone (cTSH) concentrations.
Schirmer tear tests were performed weekly. Blood
was collected for CBC prior to antimicrobial treatment
and at 3 and 6 weeks.
Results—5 dogs had serum TT4 concentrations
equal to or less than the lower reference limit, and 4
dogs had serum fT4 less than the lower reference
limit after 3 weeks of T/SMX administration; cTSH
concentrations were greater than the upper reference
limit in 4 dogs. All dogs had TT4 and fT4 concentrations
greater than the lower reference limit
after T/SMX administration was discontinued for 1
week, and cTSH concentrations were less than reference
range after T/SMX administration was discontinued
for 2 weeks. Two dogs developed
decreased tear production, which returned to normal
after discontinuing administration.
Conclusions and Clinical Relevance—Results suggest
that administration of T/SMX at a dosage of 14.1 to
16 mg/kg, PO, every 12 hours for 3 weeks caused
decreased TT4 and fT4 concentrations and increased
cTSH concentration, conditions that would be compatible
with a diagnosis of hypothyroidism. Therefore, dogs
should not have thyroid function evaluated while receiving
this dosage of T/SMX for > 2 weeks. These results
are in contrast to those of a previous study of trimethoprim-
sulfadiazine. (Am J Vet Res 2005;66:256–259)
Objective—To determine the methicillin-resistant
profile of staphylococcal isolates from the skin of
dogs with pyoderma.
Animals—90 dogs with pyoderma.
Procedure—Staphylococci isolated from dogs with
pyoderma were tested for susceptibility to methicillin
by use of a standard disk diffusion test with oxacillin
disks. The DNA extracted from the isolates was tested
for the mecA gene that encodes the penicillinbinding
protein 2a (PBP2a) by use of a polymerase
chain reaction (PCR) assay. The expression of PBP2a
was determined with a commercial latex agglutination
assay. Species of staphylococcal isolates were
identified by use of morphologic, biochemical, and
Results—Most of the isolated staphylococci were
Staphylococcus intermedius isolates. Whereas only 2
of 57 S intermedius isolates were resistant to methicillin,
approximately half of the isolates had the mecA
gene and produced PBP2a. Staphylococcus schleiferi
was the second most common isolate. Widespread
resistance to methicillin was found among S schleiferi
isolates. More coagulase-negative S schleiferi isolates
were identified with mecA gene-mediated resistance
to methicillin, compared with coagulase-positive S
Conclusions and Clinical Relevance—The latex
agglutination assay for the detection of PBP2a
expression coupled with the PCR assay for the mecA
gene may provide new information about emerging
antimicrobial resistance among staphylococcal isolates.
(Am J Vet Res2004;65:1265–1268)
Objective—To characterize the L1 gene of papillomaviruses detected in epithelial lesions of cats and to determine the relationship between those L1 gene nucleotide sequences and known L1 gene sequences of human and feline papillomaviruses.
Sample Population—10 tissue samples of epithelial lesions from 8 cats.
Procedures—DNA was extracted from tissue samples. Primers were designed to amplify the L1 gene of papillomaviruses. Amplicons of DNA were sequenced; nucleotide sequences were compared with known L1 gene nucleotide sequences of papillomaviruses and used for phylogenetic analysis.
Results—Tissue samples were obtained from lesions (diagnosed as dysplasia [n = 1], squamous cell carcinoma in situ , or squamous cell carcinoma ) of the skin (9) and oral mucosa . Two amplicons had 99% homology with the L1 gene nucleotide sequence of human papillomavirus type 38b subtype FA125. Another amplicon had 84% homology with the L1 gene nucleotide sequence of human papillomavirus type 80 and was considered to be a new type of papillomavirus. Phylogenetic tree analysis revealed that these 3 papillomaviruses were grouped into 2 clades that were not similar to the clades of Felis domesticus papillomavirus type 1 or F domesticus papillomavirus type 2 (FdPV2). The remaining 7 amplicons had 98% to 100% homology with the L1 gene nucleotide sequence of FdPV2. Phylogenetic tree analysis revealed that those 7 papillomaviruses were grouped nto a single clade with FdPV2.
Conclusions and Clinical Relevance—Results support the likelihood of transmission of papillomaviruses between humans and cats.