A comparative randomized field trial on intramammary and intramuscular dry cow antibiotic treatment of subclinical Staphylococcus aureus mastitis in dairy cows


Shpigel, N.Y.; Kass, P.H.; Saran, A.

Journal of Veterinary Medicine. A, Physiology, Pathology, Clinical Medicine 53(8): 418-422

2006


The efficacy of two dry cow treatment (DCT) regimens for subclinical Staphylococcus aureus mastitis was evaluated in naturally infected dairy cows. At dry-off, cows were assigned to two treatment groups by randomized blocks on the basis of parity and somatic cell count (SCC). Two antibiotic DCT regimens were used, namely: (1) a single intramammary infusion containing sodium nafcillin, procaine benzylpenicillin and dihydrostreptomycin; and (2) systemic cefquinome administered intramuscularly, twice at a 24-h interval. In the intramammary (IMM) treatment group, the S. aureus intramammary infection (IMI) rate was reduced from 40% (56/140 quarters) before dry-off to 20% (28/140) after calving. Seventy per cent (39/56) of the S. aureus-positive quarters were negative after calving, and 13% (11/84) of the negative quarters were positive after calving. In the systemic treatment group, the S. aureus IMI rate increased from 39% (29/74 quarters) before dry-off to 55% (41/74) after calving. Twenty-eight per cent (8/29) of the S. aureus-positive quarters were negative after calving and 45% (20/45) of the negative quarters were positive after calving. The odds ratio of an S. aureus-positive quarter being negative after calving in the IMM group relative to the systemic therapy group was 44.6 (95% confidence interval = 2.1-909.1, P < 0.01). Parity, quarter, milk SCC and N-acetyl-beta-D-glucosaminidase were tested in the model, and were found to have no significant effect on S. aureus cure rates or new IMI rates. The IMM treatment resulted in a higher cure rate compared with that observed in previous studies. The very low cure rate after systemic cefquinome treatment was comparable to the spontaneous cure rate observed in untreated controls in previous studies. The unfavourable results of the cefquinome systemic DCT might reflect inadequate pharmacokinetic properties of the drug regarding poor udder penetration in subclinical mastitis and short antimicrobial effect compared with the IMM treatment.

J.
Vet.
Med.
A
53,
418-422
(2006)
©
2006
The
Authors
Journal
compilation
©
2006
Blackwell
Verlag,
Berlin
ISSN
0931-184X
Koret
School
of
Veterinary
Medicine,
Hebrew
University,
Rehovot,
Israel
A
Comparative
Randomized
Field
Trial
on
Intramammary
and
Intramuscular
Dry
Cow
Antibiotic
Treatment
of
Subclinical
Staphylococcus
aureus
Mastitis
in
Dairy
Cows
N.
Y.
SHPIGEL
1
'
4
,
P.
H.
KAss
2
and
A.
SARAN
Addresses
of
authors:
'The
Koret
School
of
Veterinary
Medicine,
The
Hebrew
University
of
Jerusalem,
P.O.
Box
12,
Rehovot
76100,
Israel;
2
Department
of
Population
Health
and
Reproduction,
School
of
Veterinary
Medicine,
University
of
California
Davis,
California
95616,
USA;
3
National
Mastitis
Reference
Center,
The
Kimron
Veterinary
Institute,
P.O.
Box
12,
Beit-Dagan
50250,
Israel;
4
Corresponding
author:
Tel.:
+
97
239
688534;
fax:
+
97
239
688539;
E-mail:
shpigeln@agri.huji.ac.il
With
2
tables
Received
for
publication
March
30,
2006
Summary
The
efficacy
of
two
dry
cow
treatment
(DCT)
regimens
for
subclinical
Staphylococcus
aureus
mastitis
was
evaluated
in
naturally
infected
dairy
cows.
At
dry-off,
cows
were
assigned
to
two
treatment
groups
by
randomized
blocks
on
the
basis
of
parity
and
somatic
cell
count
(SCC).
Two
antibiotic
DCT
regimens
were
used,
namely:
(1)
a
single
intramammary
infu-
sion
containing
sodium
nafcillin,
procaine
benzylpenicillin
and
dihydrostreptomycin;
and
(2)
systemic
cefquinome
adminis-
tered
intramuscularly,
twice
at
a
24-h
interval.
In
the
intra-
mammary
(IMM)
treatment
group,
the
S.
aureus
intramammary
infection
(IMI)
rate
was
reduced
from
40%
(56/140
quarters)
before
dry-off
to
20%
(28/140)
after
calving.
Seventy
per
cent
(39/56)
of
the
S.
aureus-positive
quarters
were
negative
after
calving,
and
13%
(11/84)
of
the
negative
quar-
ters
were
positive
after
calving.
In
the
systemic
treatment
group,
the
S.
aureus
IMI
rate
increased
from
39%
(29/74
quarters)
before
dry-off
to
55%
(41/74)
after
calving.
Twenty-
eight
per
cent
(8/29)
of
the
S.
aureus-positive
quarters
were
negative
after
calving
and
45%
(20/45)
of
the
negative
quarters
were
positive
after
calving.
The
odds
ratio
of
an
S.
aureus-
positive
quarter
being
negative
after
calving
in
the
IMM
group
relative
to
the
systemic
therapy
group
was
44.6
(95%
confid-
ence
interval
=
2.1-909.1,
P
<
0.01).
Parity,
quarter,
milk
SCC
and
N-acetyl-fl-D-glucosaminidase
were
tested
in
the
model,
and
were
found
to
have
no
significant
effect
on
S.
au-
reus
cure
rates
or
new
IMI
rates.
The
IMM
treatment
resulted
in
a
higher
cure
rate
compared
with
that
observed
in
previous
studies.
The
very
low
cure
rate
after
systemic
cefquinome
treatment
was
comparable
to
the
spontaneous
cure
rate
ob-
served
in
untreated
controls
in
previous
studies.
The
unfa-
vourable
results
of
the
cefquinome
systemic
DCT
might
reflect
inadequate
pharmacokinetic
properties
of
the
drug
regarding
poor
udder
penetration
in
subclinical
mastitis
and
short
anti-
microbial
effect
compared
with
the
IMM
treatment.
Introduction
Subclinical
Staphylococcus
aureus
mastitis
is
an
important
disease
of
dairy
cows
around
the
world.
Intramammary
(IMM)
antibiotic
infusion
at
drying-off
is
the
most
widely
practised
treatment
of
this
disease.
The
aims
of
dry
cow
therapy
(DCT)
are
to
cure
existing
intramammary
infection
(IMI),
and
to
prevent
new
infection
during
the
dry
period.
Previously
reported
bacteriological
cure
rates
for
various
intramammary
dry
cow
treatments
range
from
25
to
75%
(Browning
et
al.,
1990;
Osteras
et
al.,
1991;
Osteras
and
Sandvik,
1996;
Dingwell
et
al.,
2003).
Systemic
DCT
was
previously
studied
in
an
attempt
to
improve
the
cure
rates.
The
systemic
administration
of
norfloxacin
(Soback
et
al.,
1990),
oxytetracycline
(Soback
et
al.,
1990;
Erskine
et
al.,
1994)
or
tilmicosin
(Nickerson
et
al.,
1999)
was
evaluated
in
three
different
studies.
Only
norfloxacin
demonstrated
an
improved
cure
rate
over
conventional
intramammary
DCT
(66.6
and
30.8%,
respectively).
Cefquinome
is
an
advanced
broad-spectrum
cephalosporin
with
improved
antibacterial
activity
compared
with
the
second-
and
third-generation
cephalosporins
(Sader
and
Jones,
1993).
The
efficacy
of
cefquinome
in
the
treatment
of
Escheri-
chia
coli
clinical
mastitis
was
previously
reported
(Shpigel
et
al.,
1996).
Cefquinome
is
resistant
to
fl-lactamases
that
are
produced
by
a
majority
of
clinically
important
bacteria.
Chemically,
cefquinome
is
a
cephem;
its
zwitterionic
structure
can
facilitate
rapid
penetration
across
biological
membranes,
including
the
porins
of
the
bacterial
cell
wall.
The
in
vitro
activity
of
cefquinome
against
S.
aureus
is
as
good
as,
or
better
than,
other
cephalosporins;
the
MIC
and
MIC
values
are
1
µg/ml,
and
no
resistant
strains
have
been
detected
to
date
(Schmid
et
al.,
1994;
Guerin-Faublee
et
al.,
2003).
These
pharmacological
and
antibacterial
properties
suggest
that
cefquinome
may
be
of
value
in
the
treatment
of
subclinical
S.
aureus
mastitis.
The
purpose
of
the
present
study
was
to
compare
the
efficacy
of
cefquinome
in
the
systemic
DCT
with
that
of
conventional
IMM
DCT
in
cows
subclinically
infected
with
S.
aureus
at
dry-
off.
Materials
and
Methods
The
herd
The
dry-cow
trial
was
conducted
in
a
government
dairy
herd
in
Israel.
The
herd
consisted
of
180
Israeli
Holstein
dairy
cows
housed
in
a
loose
housing
system
in
three
large,
completely
covered
open
sheds
and
were
fed
total
mixed
ration
(TMR).
The
mean
annual
milk
production
was
approximately
10
000
kg
per
cow.
Electric
fans
ventilated
the
cowsheds,
and
U.S.
Copyright
Clearance
Center
Code
Statement:
0931-184X/2006/5308-0418
$15.00/0
www.blackwell-synergy.com
Treatment
of
Subclinical
Staphylococcus
aureus
Mastitis
in
Dairy
Cows
419
soil
was
used
as
bedding
material.
Lactating
cows
were
kept
in
mixed
groups,
and
not
separated
according
to
production,
parity
or
udder
infection
status.
The
dry
cows
were
kept
in
a
separate
part
of
one
of
the
sheds,
and
were
transferred
to
individual
calving
stalls
2
weeks
prior
to
expected
calving.
Cows
were
milked
three
times
a
day
in
a
six
pen,
computer
controlled,
autotandem
milking
parlour
with
automatic
cluster
releasing
system.
Pre-milking
udder
wash
or
post-milking
teat
dipping
were
not
practised.
During
At
approximately
2
years
before
the
start
of
the
trial,
all
quarters
of
all
the
cows
were
infused
at
dry-off
with
an
approved
dry
cow
antibiotic.
Both
individual
cow
and
bulk
tank
milk
were
sampled
and
analysed
once
a
month
for
somatic
cell
count
by
the
Central
Laboratory
for
Milk
Recording
(Fossomatic
model
360;
Foss,
Hillerod,
Denmark).
In
the
year
preceding
the
trial,
the
average
individual
cow
somatic
cell
count
was
563
000
cells/ml
and
S.
aureus
was
isolated
from
40.9%
of
individual
cow
composite
milk
samples.
Dry-off
procedure
During
the
1-year
study
period,
all
cows
were
submitted
for
milk
sampling
2
weeks
before
dry-off.
Paired
milk
samples
were
collected
aseptically
from
every
quarter,
as
recommended
(Brown
et
al.,
1982).
Samples
were
placed
on
ice
and
imme-
diately
frozen
upon
returning
to
the
laboratory,
and
submitted
for
bacteriological
examination
within
2
days.
All
cows,
which
tested
positive
for
S.
aureus
in
at
least
one
quarter
sample
were
enrolled
in
the
trial.
At
dry-off
(cessation
of
milking),
the
cows
were
subjected
to
two
different
(2:1)
treatment
groups
by
randomized
blocks
on
the
basis
of
parity
(1st,
2nd,
3rd)
and
somatic
cells
count
(SCC)
(last
milk
recording
sample;
300
000
or
>300
000
cells/ml),
using
a
table
of
random
numbers
and
the
cow's
freeze
marking
number.
The
two
different
treatment
groups
were
required,
because
the
efficacy
of
the
parenteral
treatment
was
unknown.
Two
antibiotic
DCT
regimens
were
used,
namely:
(1)
IMM
tubes
containing
110-mg
sodium
nafcillin,
300-mg
procaine
benzylpenicillin
and
125-mg
dihydrostreptomycin
(Vetipen
DC;
Vetimex
B.V.,
Bladel,
the
Netherlands)
administered
to
all
quarters
once
and
(2)
1-mg/kg
b.w.
of
cefquinome
(Cobactan,
Intervet,
Boxmeer,
the
Netherlands)
administered
intramuscularly
two
times
at
a
24-h
interval.
One
and
2
weeks
after
calving,
duplicate
quarter
samples
for
bacteriological
examination
were
collected
aseptically
from
all
enrolled
cows.
All
milk
samples
were
evaluated
for
N-acetyl-fl-D-glucosa-
minidase
(NAGase)
activity
with
a
commercial
Milk
NAGase
Test
kit
(Applied
Diagnostics
Corp.,
Helsinki,
Finland).
Microbiological
procedures
Milk
samples
were
thawed
at
room
temperature
(25°C).
A
sterile,
plastic
disposable
bacteriological
loop
was
used
to
spread
0.03
ml
of
each
milk
sample
into
a
freshly
prepared
blood
agar
plate
(Bacto-Agar;
Difco
Laboratory,
Detroit,
MI,
USA),
which
contained
5%
washed
sheep
red
blood
cells,
and
then
into
MacConkey
agar
(Difco).
Several
drops
of
broth
cultures
containing
/3
haemolytic
S.
aureus
and
Streptococcus
agalactiae
that
had
been
established
overnight
were
separately
added
to
the
blood
agar
plates
to
permit
reading
the
CAMP
reaction
of
either
streptococcal
or
staphylococcal
colonies
that
were
positive
for
CAMP
on
the
primary
culture.
Plates
were
incubated
aerobically
at
37°C,
and
were
examined
for
growth
several
times
everyday
for
the
next
few
days.
If
growth
did
not
appear
within
7
days,
the
plates
were
considered
negative.
Gram
stain
and
culture
characteristics
(i.e.
colony
morphol-
ogy,
pigmentation,
aroma
and
haemolysis)
were
used
for
presumptive
identification
for
all
isolates.
All
staphylococci
with
a
/3
haemolytic
pattern,
a
positive-
coagulase
reaction
in
rabbit
plasma
and
a
positive
CAMP
reaction
were
presumed
to
be
S.
aureus.
All
coagulase-negative
staphylococci,
and
some
of
the
coagulase-positive
cultures
were
further
examined
with
the
apiSTAPH
system
(api-
STAPH;
BioMerieux
SA,
Marcy-l'Etoile,
France).
Species
identification
was
performed
using
the
APILAB
Plus
bacterial
identification
software
(Apilab
Plus,
1990;
Brown
et
al.,
1982).
All
coagulase-negative
staphylococci
were
recorded
as
micro-
cocci
without
species
identification.
Streptococci
were
identified
by
haemolytic
patterns,
CAMP
reaction
and
hydrolysis
of
aesculin
on
aesculin
blood
agar
(sheep
blood
agar
with
0.05%
aesculin
and
0.01%
ferric
citrate).
All
streptococci
were
typed
for
Lancefield
serological
grouping
(Phadebact
streptococcus
test;
Pharmacia
AB,
Upp-
sala,
Sweden).
Coliform
bacteria
and
other
Gram-negative
bacilli
were
identified
using
culture
characteristics
on
MacConkey
agar;
growth
in
triple
sugar
iron
agar,
urease,
catalase,
and
oxidase;
and
indole
production.
Corynebacteria
spp.
and
Arcanobacte-
rium
pyogenes
were
identified
using
culture
characteristics
on
blood
agar,
motility
and
production
of
catalase
and
urease.
The
determination
of
the
colonies,
which
were
to
be
considered
as
pathogens
was
based
on
the
colony
numbers
of
specific
organisms
that
were
pure
when
isolated
or
those
that
were
isolated
with
other
colony
types
as
described
by
the
National
Mastitis
Council
(Barnes-pallesen
et
al.,
1987).
A
quarter
was
considered
infected
with
S.
aureus
if
at
least
one
of
the
dry-off
paired
milk
samples
tested
positive
for
S.
aureus.
All
other
case
definitions
for
cure
and
new
IMI
are
described
in
the
Results
and
Table
1.
Statistical
analysis
The
odds
ratio
(OR)
of
a quarter
to
be
negative
for
S.
aureus
in
both
after-calving
samples
as
an
outcome
variable
was
evaluated
for
the
IMM
treatment
group
versus
the
systemic
treatment
group.
These
OR
were
separately
evaluated
for
the
following
quarters:
(1)
all
quarters
(positive
and
negative
for
S.
aureus
before
dry-off);
(2)
quarters
positive
for
S.
aureus
before
dry-off
and
(3)
for
quarters
negative
for
S.
aureus
before
dry-
off.
The
OR
and
their
95%
confidence
intervals
(95%
CI)
were
estimated
using
a
random
effects
logistic-binomial
regression
model.
Crude
bivariate
associations
of
outcome
and
potential
confounding
variables
with
treatment
were
initially
assessed
by
using
Pearson
Z
asymptotic
two-sided
tests
of
significance.
The
statistical
models
were
evaluated
for
confounding
associ-
ated
with
quarter
location,
parity,
SCC
on
last
milk
recording
before
dry-off,
mean
SCC
of
last
three
milk
recordings
before
dry-off,
and
milk
NAGase
activity
before
dry-off.
The
cova-
riate-adjusted
effects
of
treatment
on
the
outcome
variable
were
assessed
in
a
multivariable
logistic
regression
model.
To
build
the
models,
the
treatment
variable
was
forced
into
the
model
and
subsequent
covariates
were
analysed
by
using
420
N.
Y.
SHPIGEL
et
al.
Table
1.
The
proportional
prevalences
of
cultured
microorganisms
from
214
quarters
in
54
trial
cows
sampled
2
weeks
before
dry-off,
and
1
and
2
weeks
after
calving.
The
intramammary
and
systemic
treatment
groups
included
140
and
74
quarters,
respectively
Intramammary
treatment
Systemic
treatment
Before
dry-off
After
calving
Before
dry-off
After
calving
First
sample
Second
sample
First
sample
Second
sample
Microorganism
(no.)
(%)
(no.)
(%)
(no.)
(%)
(no.)
(%)
(no.)
(%)
(no.)
(%)
Staphylococcus
aureus
56
40
14
10
23
16.4
29
39.2
33
44.6
38
51.4
CNS
35
25
36
25.7
38
27.1
14
18.9
19
25.7
17
23
Streptococcus
spp.
25
17.9
5
3.6
5
3.6
8
10.8
2
2.7
5
6.8
Corynebacteriuin
spp.
21
15
4
2.9
15
10.7
23
31.1
9
12.2
1
1.4
Coliforms
1
0.7
4
2.9
0 0 0 0
4
5.4
2
2.7
Arcanobacterium
pyogenes
0 0 0 0
1
0.7
0 0 0 0 0 0
Negative
25
17.9
81
57.9
61
43.6
18
24.3
15
20.3
17
23
forward
stepwise
procedure
with
entry
criteria
set
at
P
<
0.05
and
exit
criteria
set
at
P
>
0.10.
For
all
analyses,
values
of
P
<
0.05
were
considered
significant.
Statistical
analyses
were
performed
using
the
program
Egret
(Version
1995,
Cytel
Inc.,
Seattle,
USA).
Results
Before
dry-off,
54%
(63/116)
of
the
cows
were
found
positive
for
S.
aureus
in
at
least
one
quarter.
Intramammary
and
systemic
therapy
was
administered
in
39
and
24
cows,
respectively.
Nine
cows
were
culled
or
excluded
before
the
completion
of
the
trial;
two
among
them
were
aborted
and
seven
had
clinical
mastitis
in
the
dry
period
(five
systemically
and
two
IMM
treated).
Fifty-four
cows
with
214
quarters
(two
dead
quarters
at
study
enrollment)
completed
the
study,
35
cows
(140
quarters)
were
treated
IMM
and
19
cows
(74
quarters)
were
treated
systemically.
The
proportional
prevalences
of
cultured
micro-
organisms
in
trial
cows
sampled
2
weeks
before
dry-off,
and
1
and
2
weeks
after
calving
were
calculated
for
the
214
quarter
samples,
and
are
shown
in
Table
2.
The
bacteriological
status
for
S.
aureus
of
the
quarters
in
the
trial
cows
sampled
2
weeks
before
dry-off,
and
1
and
2
weeks
after
calving
is
presented
in
Table
1.
In
the
IMM
treatment
group
S.
aureus
infection
rate
was
reduced
from
40%
(56/140
quarters)
before
dry-off
to
20%
(28/140)
after
calving.
Seventy
per
cent
(39/56)
of
the
S.
aureus-positive
quarters
were
negative
(S.
aureus
cure)
after
calving
and
13%
(11/84)
of
the
negative
quarters
were
positive
after
calving
(new
S.
aureus
IMI).
In
the
after-calving
samples,
80%
(45/56)
of
the
S.
aureus-positive
quarters
were
negative
1
week
after
calving,
and
3.5%
(3/84)
and
9.5%
(8/84)
of
the
negative
quarters
were
positive
1
or
2
weeks
after
calving,
respectively.
In
the
systemic
treatment
group,
the
S.
aureus
infection
rate
increased
from
39%
(29/74
quarters)
before
dry-off
to
55%
(41/74).
Twenty-eight
per
cent
(8/29)
of
the
S.
aureus-positive
quarters
were
negative
after
calving
(S.
aureus
cure)
and
45%
(20/45)
of
the
negative
quarters
were
positive
after
calving
(new
S.
aureus
IMI).
In
the
after-calving
samples,
31%
(9/29)
of
the
S.
aureus-positive
quarters
were
negative
1
week
after
calving,
and
29%
(13/45)
and
15.5%
(7/45)
of
the
negative
quarters
were
positive
1
or
2
weeks
after
calving,
respectively.
Table
2.
Bacteriological
status
for
Staphylococcus
aureus
of
quarters
in
54
trial
cows
following
systemic
or
mtramammary
dry
cow
treatment.
Quarters
were
sampled
2
weeks
before
dry-off,
and
1
and
2
weeks
after
calving
Outcomes
S.
aureus
culture
status
Quarters
Before
dry-off
First
sample
after
calving
Second
sample
after
calving
Intramammary
treatment
Systemic
treatment
(no./no.)
(%)
(no./no.)
(%)
Prevalence
of
infection
at
dry
-off
Yes'
All
All
56/140
40
29/74
39.2
Prevalence
of
non-infection
at
dry-off
No
2
All
All
84/140
60
45/74
60.8
Prevalence
of
infection
in
either
sample
after
calving
All
Yes
or
Yes
28/140
20
41/74
55.4
Prevalence
of
non-infection
in
both
after
calving
samples
All
No
No
112/140
80
33/74
44.6
Cure
rate
based
on
both
after
calving
samples
Yes
No
No
39/56
70
8/29
27.6
Cure
rate
based
on
first
after
calving
sample
Yes
No
All
45/56
80
9/29
31
No-cure
rate
based
on
first
after
calving
sample
Yes
Yes
All
11/56
19.6
20/29
68.9
New
infection
rate
based
on
either
after
calving
sample
No
Yes
or
Yes
11/84
13.1
20/45
44.4
New
infection
rate
based
on
first
after
calving
sample
No
Yes
All
3/84
3.5
13/45
28.8
New
infection
rate
based
on
second
after
calving
sample
No
No
Yes
8/84
9.5
7/45
15.5
Prevalence
of
non-infected
quarters
in
all
samples
No
No
No
73/84
87
25/45
55.5
1,2
Quarter
samples
were
positive
(Yes)
or
negative
(No)
for
S.
aureus,
respectively.
Treatment
of
Subclinical
Staphylococcus
aureus
Mastitis
in
Dairy
Cows
421
The
OR
of
an
S.
aureus-positive
quarter
to
be
negative
after
calving
in
the
IMM
group
relative
to
the
systemic
therapy
group
was
44.6
(95%
CI
=
2.1
-
909.1,
P
<
0.01).
The
OR
of
any
quarter
to
be
negative
for
S.
aureus
after
calving
in
the
IMM
group,
relative
to
the
systemic
therapy
group
was
15.1
(95%
CI
=
3.5-66.7,
P
<
0.01).
The
OR
of
an
S.
aureus
negative
quarter
to
remain
negative
after
calving
in
the
IMM
group
relative
to
the
systemic
therapy
group
was
9.2
(95%
CI
=
1.8-48.1,
P
<
0.01).
None
of
the
factors
evaluated
as
confounders
(parity,
quarter,
milk
SCC
and
NAGase)
of
treatment
caused
a
meaningful
change
on
the
treatment
OR.
Discussion
This
study
represents
an
effort
to
properly
design,
conduct
and
statistically
analyse
a
field
trial
on
the
efficacy
of
IMM
and
systemic
DCT.
As
numerous
factors
are
known
to
affect
the
results
of
DCT,
these
factors
were
considered
in
the
design,
conduct
and
statistical
analysis
of
the
study.
Contrary
to
previous
studies,
parity,
quarter,
SCC
and
NAGase
activity
did
not
affect
recovery
in
this
study
(Sol
et
al.,
1994;
Osteras
et
al.,
1999).
This
difference
might
be
attributed
to
repeated
cycles
of
highly
effective
IMM
DCT
and
reinfection
because
of
poor
management.
The
study
was
conducted
on
a
single
dairy
farm
with
a
high
prevalence
of
S.
aureus
IMI
(40%
at
study
onset),
high
SCC
(563
000
cells/ml)
and
poor
milking
parlour
management.
The
herd
experienced
a
continuous
increase
of
S.
aureus
IMI
although
proper
IMM
DCT
was
comprehensively
used
for
more
than
2
years.
It
is
generally
accepted
that
negative
culture
of
after-calving
samples
from
quarters
positive
for
S.
aureus
before
dry-off
demonstrates
treatment
success
or
cure.
Furthermore,
positive
culture
of
after-calving
samples
from
quarters
negative
for
S.
aureus
before
dry-off
were
considered
as
new
infection.
Under
these
conventions,
the
IMM
treatment
resulted
in
a
high
cure
rate
(70%)
similar
to
that
observed
in
previous
studies
(Browning
et
al.,
1990;
Osteras
et
al.,
1991,
1999;
Osteras
and
Sandvik,
1996).
The
very
low
cure
rate
(28%)
after
systemic
cefquinome
treatment
was
comparable
to
the
spon-
taneous
cure
rate
observed
in
untreated
controls
in
previous
studies
(Soback
et
al.,
1990).
The
cure
rate
for
the
IMM
treatment
was
even
higher
for
the
first
after-calving
sample
(80%).
The
lower
new
infection
rate
after
IMM
treatment
(13%)
than
after
systemic
cefquinome
treatment
(45%)
might
demonstrate
a
protective
effect
of
the
IMM
DCT
during
the
dry
period
and
perhaps
even
after
calving.
This
outcome
is
not
surprising
considering
the
extended
antimicrobial
effect
of
the
IMM
DCT
compared
with
the
systemic
DCT.
As
most
of
the
new
infection
was
found
in
the
first
after-calving
sample,
it
can
be
assumed
that
some
of
the
infected
quarters
were
cured
and
reinfected
by
the
second
after-calving
sampling.
The
cure
rate
for
the
first
after-calving
samples
was
80
and
31%
for
the
IMM
and
systemic
treatment,
respectively.
However,
as
milk
shedding
of
S.
aureus
is
known
to
be
intermittent
(Mattila
et
al.,
1985),
stringent
diagnostic
criteria
should
be
followed.
The
unfavourable
results
of
the
cefquinome
systemic
DCT
might
reflect
inadequate
pharmacokinetic
properties
of
the
drugs
regarding
poor
udder
penetration
in
subclinical
mastitis.
This
is
in
clear
contradiction
to
the
excellent
efficacy
of
cefquinome
in
the
treatment
of
coliform
clinical
mastitis
and
respiratory
diseases
(Shpigel
et
al.,
1996).
The
high
cure
rate
of
the
IMM
DCT,
irrespective
of
age
and
inflammatory
indicators
(SCC
and
NAGase),
high
reinfection
rate
and
poor
milking
hygiene,
possibly
indicate
the
presence
of
mostly
new
S.
aureus
IMI.
These
factors
probably
explain
the
high
herd
prevalence
of
S.
aureus
IMI
despite
successful
DCT.
While
persistent
IMI
are
more
resistant
to
treatment,
new
IMI
were
suggested
to
be
more
responsive
to
a
short
antimicrobial
therapy
for
the
elimination
of
major
pathogen.
However,
poor
udder
penetration
of
cefquinome
is
expected
in
S.
aureus
IMI
of
short
duration,
and
mild
inflammatory
changes,
where
the
blood-udder
barrier
is
probably
intact.
Staphylococcus
aureus
organisms
are
known
to
evade
host
immune
mechanisms
by
invasion
of
neutrophils,
macrophages
and
mammary
epithelium
(Hensen
et
al.,
2000).
Cefquinome
is
perhaps
not
the
optimal
drug
for
intracellular
organisms,
because
relatively
low
drug
concentrations
are
expected
in
the
cytosol
or
intracellular
organelles
(Murdoch
and
Peterson,
1991).
Prolonged
systemic
cefquinome
treatment
might
result
in
a
better
cure
rate
of
S.
aureus
IMI
in
dry
cows;
however,
such
protocol
is
cost
prohibitive
and
impractical.
References
Apilab
Plus,
1990:
Bacterial
identification
software.
BioMerieux
SA,
Marcy-
l'Etoile,
France.
Barnes-pallesen,
F.
D.,
P.
Blackmer,
A.
Britten,
R.
B.
Bushnell,
D.
M.
van
Damme,
and
F.
Welcome,
1987:
Laboratory
and
Field
Hand-
book
on
Bovine
Mastitis.
National
Mastitis
Council
Inc.,
Wash-
ington,
DC.
Brown,
R.
W.,
D.
A.
Barnum,
D.
E.
Jasper,
J.
S.
Mcdonald,
and
W.
D.
Schultze,
1982:
Microbiological
Procedures
for
Use
in
the
Diagnosis
of
Bovine
Mastitis,
2nd
edn.
National
Mastitis
Council,
Inc.,
Washington,
DC.
Browning,
J.
W.,
G.
A.
Mein,
M.
Barton,
T.
J.
Nicholls,
and
P.
Brigh-
tling,
1990:
Effects
of
antibiotic
therapy
at
drying
off
on
mastitis
in
the
dry
period
and
early
lactation.
Aust.
Vet.
J.
67,440-442.
Dingwell,
R.
T.,
K.
E.
Leslie,
T.
F.
Duffield,
Y.
H.
Schukken,
L.
DesCoteaux,
G.
P.
Keefe,
D.
F.
Kelton,
K. D.
Lissemore,
W.
Shewfelt,
P.
Dick,
and
R.
Bagg,
2003:
Efficacy
of
intramammary
tilmicosin
and
risk
factors
for
cure
of
Staphylococcus
aureus
infection
in
the
dry
period.
J.
Dairy
Sci.
86,
159-168.
Erskine,
R.
J.,
P.
C.
Bartlett,
P.
C.
Crawshaw,
and
D.
M.
Gombas,
1994:
Efficacy
of
intramuscular
oxytetracycline
as
a
dry
cow
treat-
ment
for
Staphylococcus
aureus
mastitis.
J.
Dairy
Sci.
77,3347-3353.
Guerin-Faublee,
V.,
G.
Carret,
and
P.
Houffschmitt,
2003:
In
vitro
activity
of
10
antimicrobial
agents
against
bacteria
isolated
from
cows
with
clinical
mastitis.
Vet.
Rec.
152,
466-471.
Hensen,
S.
M.,
M.
J.
Pavicic,
J.
A.
Lohuis,
and
B.
Poutrel,
2000:
Use
of
bovine
primary
mammary
epithelial
cells
for
the
comparison
of
adherence
and
invasion
ability
of
Staphylococcus
aureus
strains.
J.
Dairy
Sci.
83,
418-429.
Mattila,
T.,
S.
Saari,
H.
Vartiala,
and
M.
Sandholm,
1985:
Milk
antitrypsin
as
a
marker
of
bovine
mastitis
correlation
with
bac-
teriology.
J.
Dairy
Sci.
68,
114-122.
Murdoch,
M.
B.,
and
L.
R.
Peterson,
1991:
Antimicrobial
penetration
into
polymorphonuclear
leukocytes
and
alveolar
macrophages.
Se-
min.
Respir.
Infect.
6,112-121.
Nickerson,
S.
C.,
W.
E.
Owens,
L.
K.
Fox,
C. C.
Scheifinger,
T.
R.
Shryock,
and
T.
E.
Spike,
1999:
Comparison
of
tilmicosin
and
cephapirin
as
therapeutics
for
Staphylococcus
aureus
mastitis
at
dry-
off.
J.
Dairy
Sci.
82,
696-703.
Osteras,
0.,
and
L.
Sandvik,
1996:
Effects
of
selective
dry-cow
therapy
on
culling
rate,
clinical
mastitis,
milk
yield
and
cow
somatic
cell
count.
A
randomized
clinical
field
study
in
cows.
Zentralbl
Veter-
inarmed
B
43,
555-575.
N.
Y.
SHPIGEL
et
al.
422
Osteras,
0.,
V.
L.
Edge,
and
S.
W.
Martin,
1999:
Determinants
of
success
or
failure
in
the
elimination
of
major
mastitis
pathogens
in
selective
dry
cow
therapy.
J.
Dairy
Sci.
82,
1221-1231.
Osteras,
0.,
L.
Sandvik,
J.
Aursjo,
G.
G.
Gjul,
and
A.
Jorstad,
1991:
Assessment
of
strategy
in
selective
dry
cow
therapy
for
mastitis
control.
Zentralbl
Veterinarmed
B.
38,
513-522.
Sader,
H.
S.,
and
R.
N.
Jones,
1993:
The
fourth-generation
ce-
phalosporins:
antimicrobial
activity
and
spectrum
definitions
using
cefpirome
as
an
example.
The
Antimicrobic
Newsletter
9,
9-16.
Schmid,
P.,
A.
Bottner,
and
R.
Humke,
1994:
In
vitro
testing
of
bac-
terial
field
strains
from
bovine
origin
for
sensitivity
to
cefquinome.
Proceedings
of
the
18th
World
Buiatric
Congress
Bologna,
Italy,
August
29—Sept
2,1994.539-542.
Shpigel,
N.
Y.,
D.
Levin,
M.
Winkler,
A.
Saran,
G.
Ziv,
and
A.
Bottner,
1996:
Efficacy
of
the
fourth
generation
cephalosporin
cefquinome
for
the
treatment
of
experimentally
induced
Escherichia
coli
mastitis
in
cows.
Dairy
Sci.
80,
318-323.
Soback,
S.,
G.
Ziv,
M.
Winkler,
and
A.
Saran,
1990:
Systemic
dry
cow
therapy
a
preliminary
report.
J.
Dairy
Sci.
73,
661-666.
Sol,
J.,
0.
C.
Sampimon,
J.
J.
Snoep,
and
Y.
H.
Schukken,
1994:
Factors
associated
with
bacteriological
cure
after
dry
cow
treatment
of
subclinical
staphylococcal
mastitis
with
antibiotics.
J.
Dairy
Sci.
77,
75-79.