Effects of Thiamphenicol and Chloramphenicol in Inhibiting Neisseria gonorrhoeae Isolates

Abstract

Thiamphenicol was compared with penicillin, tetracycline, and chloramphenicol for its ability to inhibit 530 isolates of Neisseria gonorrhoeae, including 13 penicillinase-producing isolates. Thiamphenicol proved to be as active as chloramphenicol in inhibiting all
of the isolates.

Full text

ANTIMICROBIAL
AGENTS
AND
CHEMOTHERAPY,
Nov.
1978,
P.
788-790
0066-4804/78/0014-0788$02.00/0
Copyright
i
1978
American
Society
for
Microbiology
Vol.
14,
No.
5
Printed
in
U.S.A.
Effects
of
Thiamphenicol
and
Chloramphenicol
in
Inhibiting
Neisseria
gonorrhoeae
Isolates
P.
D.
DUCK,'
J.
R.
DILLON,'
*
AND
L.
EIDUS2
Antimicrobials
Section,'
National
Neisseria
Reference
Centre,
and
Bureau
of
Bacteriology,2
Tunney's
Pasture,
Ottawa,
Ontario
KIA
OL2
Canada
Received
for
publication
26
July
1978
Thiamphenicol
was
compared
with
penicillin,
tetracycline,
and
chlorampheni-
col
for
its
ability
to
inhibit
530
isolates
of
Neisseria
gonorrhoeae,
including
13
penicillinase-producing
isolates.
Thiamphenicol
proved
to
be
as
active
as
chlor-
amphenicol
in
inhibiting
all
of
the
isolates.
Thiamphenicol,
a
chloramphenicol
analog
in
which
the
nitro
group
has
been
substituted
with
a
methylsulfonyl
group
(2),
has
been
suggested
as
a
viable
alternate
therapy
regimen
to
penicil-
lin
in
the
treatment
of
infections
with
Neisseria
gonorrhoeae
(2).
This
antibiotic
has
been
suc-
cessfully
used
in
treatment
of
uncomplicated
gonococcal
infections
in
both
men
and
women
(4,
15),
with
failure
rates
as
low
as 2
to
3%.
Because
penicillin
and
tetracycline
treatment
failures
have
been
correlated
with
increased
re-
sistance
to
those
antibiotics
(5,
6),
the
use
of
thiamphenicol
as
an
alternate
therapy
regimen
in
the
treatment
of
N.
gonorrhoeae
should
be
seriously
evaluated.
In
the
present
study,
we
have
examined
the
minimal
inhibitory
concen-
trations
(MICs)
of
530
isolates
of
N.
gonor-
rhoeae,
including
13
f)-lactamase-producing
iso-
lates,
to
penicillin,
tetracycline,
chlorampheni-
col,
and
thiamphenicol.
The
fi-lactamase-producing
isolates
were
ob-
tained
from
Canadian,
Asian,
American,
and
African
sources
during
the
period
1976
to
1978.
The
other
517
nonpenicillinase-producing
iso-
lates
were
collected
during
a
previous
study
(la)
in
1973
to
1974.
All
strains
were
maintained
at
-70°C
in
heart
infusion
broth
(Difco
Laborato-
ries,
Detroit,
Mich.)
plus
20%
glycerol.
Before
determining
MICs,
all
isolates
were
subcultured
on
GC
medium
base
(Difco),
containing
1%
(vol/vol)
defined
supplement
(8),
followed
by
incubation
for
18
h
at
35°C
in
an
atmosphere
containing
5%
CO2.
Penicillin-resistant
isolates
were
tested
for
the
production
of
fi-lactamase
by
using
the
chromogenic
cephalosporin
substrate,
nitrocefin
(13).
MICs
were
determined
by
an
agar
dilution
technique,
and
antibiotic-contain-
ing
plates
were
inoculated
by
an
adaptation
of
the
method
of
Maier
et
al.
(10).
Antibiotic
media
consisted
of
GC
medium
base
with
2%
defined
supplement
to
which
the
following
antibiotics
78E
were
added
to give
the
following
final
concentra-
tions:
penicillin
G
(Ayerst),
40, 20,
10,
5,
2,
1,
0.5,
0.25,
0.1,
0.05,
0.025,
and
0.013
U/ml;
tetracycline
hydrochloride
(Bristol
Laboratories),
4,
2,
1,
0.5,
0.25,
0.1,
0.05,
and
0.025
,tg/ml;
thiamphenicol
(A.
Siboulet,
Paris),
8,
4,
2,
1,
0.5,
0.25,
0.10, 0.05,
and
0.025
,ug/ml;
and
chloramphenicol
(Parke-
Davis),
8, 4,
2,
1,
0.5,
0.25,
0.10, 0.05,
and
0.025
,ug/ml.
For
all
susceptibility
tests,
World
Health
Organization
isolates
III,
V,
and
VII
(supplied
by
A.
Reyn,
Copenhagen)
were
used
as
control
strains.
The
results
were
read
after
18
h
of
incubation
at
35°C
in
a
5%
CO2
atmosphere.
The
MIC
was
considered
to
be
that
concentration
of
antibiotic
which
completely
inhibited
growth;
the
presence
of
one
to
nine
colonies
was
accepted
as
being
indicative
of
drug
susceptibility.
Table
1
shows
the
susceptibility
of
517
non-
,B-lactamase-producing
isolates
to
penicillin,
tet-
racycline,
thiamphenicol,
and
chloramphenicol.
Penicillin
and
tetracycline
were
more
active
than
thiamphenicol
and
chloramphenicol;
over
60%
of
the
isolates
was
inhibited
by
concentra-
tions
of
0.25
U
of
penicillin
or
0.25
,ug
of
tetra-
cycline
per
ml,
as
compared
to
under
30%
inhi-
bition
by
chloramphenicol
and
thiamphenicol
at
this
concentration
level.
Over
90%
of
the
isolates
was
inhibited
by
2
jig
of
thiamphenicol
or
chlor-
amphenicol
per
ml.
In
examining
the
f8-lactamase-producing
iso-
lates
(Table
2),
thiamphenicol
and
chloram-
phenicol
exhibited
similar
cumulative
MICs;
thiamphenicol
was
slightly
more
active
than
chloramphenicol.
All
of
the
penicillinase-pro-
ducing
isolates
were
inhibited
by
4.0
,ug
of
chlor-
amphenicol
or
thiamphenicol
per
ml.
Pencillin-
resistant
isolates
were
more
resistant
to
tetra-
cycline;
only
76.9%
of
the
f-lactamase-
producing
isolates
was
inhibited
by
1.0
,ug
of
tetracycline
per
ml
was
compared
with
98.5%
of
the
non-/3-lactamase
producers
(Table
1).

TABLE
1.
MICs
of
517
N.
gonorrhoeae
isolates
to
penicillin,
tetracycline,
thiamphenicol,
and
chloramphenicol
Cumulative
%
inhibition
for
MICsa
of:
Antibiotic
0.013
0.025
0.05
0.1
0.25
0.5
1
2 4
8
Penicillin
13.5
32.3
41.2 47.6
64.4
69.8
94.8
100
Tetracycline
2.7
20.7
56.3
74.1
97.1
98.5
98.8
100
Thiamphenicol
0.2
1.2
3.9
28.8
72.9
83.4
97.5 99.6
100
Chloramphenicol
0.8
2.7
7.2
29.2
65.2
80.7 91.7 99.8
100
All
MICs
expressed
as
micrograms
per
milliliter
except
penicillin
(units
per
milliliter).
TABLE
2.
MICs
of
13
/3-lactamase-producing
N.
gonorrhoeae
isolates
Cumulative
%
inhibition
for
MICs'
of:
Antibiotic
0.5
1
2
4
8
10
20
40
>40
Penicillin
7.7
18.4
100
Tetracycline
53.8
76.9
100
Thiamphenicol
76.9
100
Chloramphenicol
69.2
100
a
AU
MICs
expressed
as
micrograms
per
milliliter
except
penicillin
(units
per
milliliter).
The
MICs
of
N.
gonorrhoeae
to
thiampheni-
col
reported
in
the
present
study
agree
with
data
reported
by
Bergogne-Berezin
et
al.
(1)
on
92
isolates.
These
workers
found
that
50
and
80%
of
the
isolates
were
inhibited
by
0.5
and
2.0
jig
of
thiamphenicol
per
ml,
respectively.
Although
100%
of
the
isolates
from
the
present
study
was
inhibited
by
8
ug/ml,
approximately
10%
of
the
isolates
examined
by
Bergogne-Berezin
et
al.
(1)
was
resistant
to
this
concentration
and
required
MICs
up
to
128
,ug/ml.
The
N.
gonorrhoeae
MICs
of
thiamphenicol
reported
in
this
study,
including
the
MICs
for
/3-lactamase-positive
isolates,
are
within
re-
ported
serum
levels
attainable
after
oral,
intra-
muscular,
or
intravenous
injection
of
the
anti-
biotic
(2,
12,
14,
18).
In
addition,
thiamphenicol
shows
high
active
concentrations
in
urine
(2,
14);
over
50%
of
the
administered
dose
was
excreted
by
the
kidneys.
The
ability
of
thiamphenicol
to
be
eliminated
in
an
active
state
is
one
of
the
most
important
differences
between
chloram-
phenicol
and
thiamphenicol
(2,
19).
Thiamphen-
icol
is
not
subject
to
metabolic
transformations
(2)
which
either
conjugate
it
with
other
com-
pounds
or
degrade
it
into
nonactive
derivatives.
Chloramphenicol,
on
the
other
hand,
generally
undergoes
a
massive
loss
in
activity
after
trans-
formation
into
a
glucuronide
derivative
in
the
liver
(2,
3,
19).
Chloramphenicol,
although
clinically
useful,
has
limited
possibilities
as
a
therapeutic
agent
due
to
its
association
with
the
development
of
aplastic
anemia
(11).
This
serious
and
clinically
restricting
side
effect
has
so
far
not
been
ob-
served
on
administration
of
thiamphenicol
(19).
Furthermore,
although
thiamphenicol
and
chloramphenicol
both
produce
reversible
eryth-
roid
suppression,
only
high
concentrations
of
chloramphenicol
inhibit
DNA
synthesis
in
hu-
man
lymphoblastoid
cells
(20).
According
to
Yu-
nis
et
al.
(20),
the
ability
of
chloramphenicol
to
inhibit
DNA
synthesis
might
be
related
to
its
role
in
the
development
of
bone
marrow
aplasia.
The
increased
toxicity
of
chloramphenicol
has
also
been
attributed
to
its
greater
affinity
for
bone
marrow
cells
as
compared
with
thiamphen-
icol
(9).
Although
thiamphenicol
can
depress
the
proliferation
of
immunologically
active
cells,
the
effect
has
been
shown
to
be
reversible
after
withdrawal
of
the
drug
(11).
The
simultaneous
development
of
bacterial
resistance
to
chloramphenicol
and
thiampheni-
col
should
be
highly
correlated.
Both
antibiotics
can
be
acetylated
by
acetyl
transferase,
an
en-
zyme
commonly
specified
by
R
plasmid-bearing
isolates
of
Enterobacteriaceae
(3).
Chloram-
phenicol/thiamphenicol-resistant
isolates
of
gram-positive
bacteria
with
R
plasmids
have
been
described
(7).
Although
plasmid-mediated
chloramphenicol
or
thiamphenicol
resistance
has
not
yet
been
described
for
N.
gonorrhoeae,
the
recent
discovery
of
penicillinase-producing
plasmids
in
this
organism
suggests
that
the
ac-
quisition
of
other
plasmid-mediated
antibiotic
resistance
determinants
is
a
possibility
that
should
not
be
discounted.
However,
Ferrari
and
Della
Bella
(3)
have
indicated
that
the
acetyla-
tion
of
thiamphenicol
and
chloramphenicol
can
be
reversed
in
humans
through
the
action
of
/-
esterase,
which
hydrolyzes
inactive
acetylated
derivatives
with
the
resultant
release
of
active
VOL.
14,
1978
NOTES
789

ANTIMICROB.
AGENTS
CHEMOTHER.
antibiotic.
In
addition,
a
report
by
Thayer
et
al.
(17)
also
indicates
that
gonococci
do
not
develop
in
vitro
resistance
to
thiamphenicol
by
repeated
exposure
to
increasing
antibiotic
concentrations.
We
thank
the
Disease
Statistics
and
Operational
Planning
Section,
Laboratory
Center
for
Disease
Control,
and
Y.
Mao
for
co-operation
in
computer
processing
the
data.
The
tech-
nical
assistance
of
Peter
Lomax
is
gratefully
acknowledged.
We
also
thank
B.
B.
Diena
for
his
critical
reading
of
the
manuscript.
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790
NOTES