Article

10th Survey of antimicrobial resistance in noninvasive clinical isolates of Streptococcus pneumoniae collected in Belgium during winter 2007–2008

WIV/ISP, Unit of Antibiotic Research, Institute of Public Health, 642, Engelandstraat, 1180 Brussel, Belgium.
Pathologie Biologie (Impact Factor: 1.2). 11/2009; 58(2):147-51. DOI: 10.1016/j.patbio.2009.07.018
Source: PubMed
ABSTRACT
The aim of the study was to evaluate the antibiotic resistance in noninvasive clinical isolates of Streptococcus pneumoniae collected in Belgium during winter 2008-2007.
Four hundred and forty eight unduplicated isolates collected by 15 laboratories were tested by microdilution following CLSI.
Insusceptibility rates (I+R) were as follows: penicillin G (PEN) 11.6% (4.0% R), ampicillin 11.4% (4.0% R), amoxicillin+/-clavulanic acid 0, cefaclor 10.3% (9.6% R), cefuroxime 9.2% (8.7% R), cefuroxime-axetil 8.7% (7.8% R), cefotaxime, ceftazidime and cefepime 2.0% (0% R), imipenem 2.5% (0% R), ciprofloxacin and ofloxacin 5.1% (0.4% R), levofloxacin 0.7% (0.4% R), moxifloxacin 0.4% (0.2% R), erythromycin (ERY) 29.7% (29.2% R), azithromycin 29.7% (28.8% R), telithromycin 0%, clindamycin 26.3% (25.4% R) and tetracycline (TET) 21.9% (16.5% R). From 2001 to 2008, a significant decrease in penicillin-insusceptibility (21.0% to 11.6%), penicillin-resistance (9.7% to 4.0%) and ciprofloxacin-insusceptibility (11.2% to 5.1%) was found. Cross-resistance between penicillin and other betalactams in penicillin-insusceptible isolates was incomplete: all these isolates remained fully susceptible to amoxicillin. Erythromycin-insusceptibility was significantly higher in children than in adults (43.9%/27.4%), while penicillin-insusceptibility significantly higher in Brussels than in the Flanders (22.9%/8.1%). The commonest resistance phenotype was ERY-TET (12.7%) followed by ERY (7.4%) and PEN-ERY-TET (5.8%). Capsular types 19 (25%), 14 (19.3%), 23 (15.4%) and 15 (13.5%) were the most important in penicillin-insusceptible.
We noted a decrease in resistance to the majority of the compounds. Insusceptibility rates were higher in children than in adults and the difference between the north and the south of Belgium became less marked.

Full-text

Available from: Stephane De Craeye
10th Survey of antimicrobial resistance in noninvasive clinical isolates of
Streptococcus pneumoniae collected in Belgium during winter 2007–2008
Dixie
`
me surveillance de la re
´
sistance aux antibiotiques dans des souches non invasives de
Streptococcus pneumoniae collectionne
´
es en Belgique pendant l’hiver 2007 a
`
2008
R. Vanhoof
a,
*
, K. Camps
b
, M. Carpentier
c
, S. De Craeye
a
, J. Frans
d
, Y. Glupczynski
e
, P. Goffinet
f
,
B. Gordts
g
, D. Govaerts
h
, L. Ide
i
, P. Lefe
`
vre
j
, M. Lontie
k
, R. Cartuyvels
l
, F. Meunier
m
, B. Mulongo
n
,
I. Philippart
o
, I. Surmont
p
, E. Van Bossuyt
a
, J. Van Eldere
q
, J. Verhaegen
q
a
WIV/ISP, Unit of Antibiotic Research, Institute of Public Health, 642, Engelandstraat, 1180 Brussel, Belgium
b
AZ Stuivenberg, 2060 Antwerpen, Belgium
c
Ho
ˆ
pital de la Citadelle, 4000 Lie
`
ge, Belgium
d
Imeldaziekenhuis, 2820 Bonheiden, Belgium
e
Clinique universitaire de Mont-Godinne, 5530 Yvoir, Belgium
f
Cliniques du Sud-Luxembourg, 6700 Arlon, Belgium
g
AZ St. Jan, 8000 Brugge, Belgium
h
CHU Andre
´
-Ve
´
sale, 6110 Montignies-le-Tilleul, Belgium
i
AZ Jan Palfijn, 9000 Gent, Belgium
j
Ho
ˆ
pital Princesse-Paola, 6900 Marche-en-Famenne, Belgium
k
Medisch Centrum Huisartsen, 3000 Leuven, Belgium
l
Virga-Jesseziekenhuis, 3500 Hasselt, Belgium
m
Ho
ˆ
pital de Jolimont, 7100 Haine St. Paul, Belgium
n
Clinique Saint-E
´
tienne, 1210 Bruxelles, Belgium
o
Ho
ˆ
pital de Warquignies, 7300 Boussu, Belgium
p
H.-Hartziekenhuis, 8800 Roeselare, Belgium
q
National Reference Centre Pneumococci, UZ Gasthuisberg, 3000 Leuven, Belgium
Pathologie Biologie 58 (2010) 147–151
ARTICLE INFO
Article history:
Received 26 June 2009
Accepted 13 July 2009
Available online 4 November 2009
Keywords:
S. pneumoniae
Resistance
Survey
ABSTRACT
Objectives.
The aim of the study wa s to evaluate the antibiotic resistance in noninvasive clinical
isolates of Streptococcus pneumoniae collected in Belgium during winter 2008–2007.
Method. Four hundred and forty eight unduplicated isolates collected by 15 laboratories were tested
by microdilution following CLSI.
Results. Insusceptibility rates (I + R) were as follows: penicillin G (PEN) 11.6% (4.0% R), ampicillin
11.4% (4.0% R), amoxicillin + /–clavulanic acid 0, cefaclor 10.3% (9.6% R), cefuroxime 9.2% (8.7% R),
cefuroxime-axetil 8.7% (7.8% R), cefotaxime, ceftazidime and cefepime 2.0% (0% R), imipenem 2.5% (0% R),
ciprofloxacin and ofloxacin 5.1% (0.4% R), levofloxacin 0.7% (0.4% R), moxifloxacin 0.4% (0.2% R),
erythromycin (ERY) 29.7% (29.2% R), azithromycin 29.7% (28.8% R), telithromycin 0%, clindam ycin 26.3%
(25.4% R) and tetracycline (TET) 21.9% (16.5% R). From 2001 to 2008, a significant decrease in penicillin-
insusceptibility (21.0% to 11.6%), penicillin-resistance (9.7% to 4.0%) and ciprofloxacin-insusceptibility
(11.2% to 5.1%) was found. Cross-resistance between penicillin and other betalactams in penicillin-
insusceptible isolates was incomplete: all these isolates remained fully susceptible to amoxicillin.
Erythromycin-insusceptibility was significantly higher in childr en than in adults (43.9%/27.4%), while
penicillin-insusceptibili ty significantly highe r in Brussels than in the Flanders (22.9%/8.1%). The
commonest resistance phenotype was ERY-TET (12.7%) followed by ERY (7.4%) and PEN-ERY-TET (5.8%).
Capsular types 19 (25%), 14 (19.3%), 23 (15.4%) and 15 (13.5%) were the most important in penicillin-
insusceptible.
* Corresponding author.
E-mail address: raymond.vanhoof@iph.fgov.be (R. Vanhoof).
0369-8114/$ see front matter ß 2009 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.patbio.2009.07.018
Page 1
1. Introduction
Streptococcus pneumoniae causes a wide variety of infections
both in the community and in hospitalized patients. It is not only
the causative agent for upper respiratory tract infections but also
for a number of important invasive infections such as septicaemia,
pneumonia and meningitis. S. pneumoniae remains a major
pathogen with a high degree of morbidity and a considerable rate
of mortality [1–4]. The appearance of resistant strains, in which
both the de novo acquisition of new genetic material and the clonal
spread of resistant isolates are implied, can be an incriminating
factor in the treatment and outcome of pneumococcal disease. In
Belgium, the first two penicillin-resistant isolates were reported by
Vanhoof et al. [5] in 1980. Since the beginning of the 1990s, we
have been reporting a slow but steadily increase in penicillin non-
susceptibility in clinical isolates with a peak in 2001 [6].An
important decrease in resistance was noted in the following years
[7]. In this article, we present data collected during the 10th
collaborative surveillance study conducted during the winter of
2007–2008.
2. Material and methods
2.1. Isolates
A total of 448 consecutive, non-duplicated noninvasive respiratory clinical
isolates of S. pneumoniae, collected during winter 2007–2008 in 15 clinical
laboratories throughout Belgium, were included in this study. Isolates were kept at
70 8C in Brain Heart Infusion Broth (Difco) containing 10% (v/v) glycerol until
susceptibility testing at the Pasteur Institute in Brussels. All isolates underwent a
slide agglutination (Slidex pneumo Kit
TM
, BioMe
´
rieux), an Optochin test (Opto-F,
bioMe
´
rieux) and a LytA PCR before MIC testing.
2.2. Antibiotics
The following antibiotics were tested in the study and were provided as
laboratory preparations with known potency: clavulanic acid, ceftazidime
(GlaxoSmithKline), cefepime (Bristol Myers Squibb), cefotaxime, levofloxacin,
ofloxacin and telithromycin (Aventis Pharma), imipenem (Merck Sharp & Dohme),
ciprofloxacin and moxifloxacin (Bayer), azithromycin (Pfizer). Amoxicillin, ampi-
cillin, cefaclor, cefuroxime, clindamycin, erythromycin, penicillin G and tetracycline
were obtained from a commercial source (Sigma). Amoxicillin/clavulanic acid was
tested in a 2:1 ratio. All antibiotics were tested for 16 serial twofold dilutions
(0.001–32
m
g/mL).
2.3. Susceptibility testing
The minimal inhibitory concentration (MIC) was determined by broth
microdilution as recommended by the CLSI [8]. S. pneumoniae ATCC 49619,
S. pneumoniae TPN881 (internal mefA positive control isolate with penicillin MIC of
0.008–0.03
m
g/mL and erythromycin MIC of 4–16
m
g/ml) and Staphylococcus
aureus NCTC 11561 (ß-lactamase positive to validate the clavulanic acid component
of amoxicillin/clavulanic acid) were included as quality control organisms in each
series. Interpretation of the results was based on breakpoints provided by the CLSI
[9]. Levels of susceptibility to ampicillin were determined by penicillin. For
ciprofloxacin we used breakpoints of one dilution lower than those of levofloxacin
as is generally the case for other types of microorganisms.
2.4. Capsular typing
All penicillin non-susceptible isolates were typed by the National Reference
Centre by using the Quellung reaction with sera from the Staten Seruminstitute
(Copenhagen).
2.5. Statistical analysis
The Chi
2
test, with or without Yates’ correction, for two independent samples
was used for the statistical evaluation of the results. The level of significance was set
at 0.05.
3. Results
In total 448 documented isolates of S. pneumoniae were
included in the study for further analysis. Seventy-eight isolates
(17.4%) of the isolates were from children (age 15 years) with
66/78 or 84.6% from children under five years of age, while 370
Conclusion. We noted a decrease in resistance to the majority of the compounds. Insusceptibility rates
were higher in children than in adults and the difference between the north and the south of Belgium
became less marked.
ß 2009 Elsevier Masson SAS. All rights reserved.
RE
´
SUME
´
But de l’e
´
tude.
Le but e
´
tait d’e
´
valuer les taux de re
´
sistance dans des souches cliniques non invasives de
Streptococcus pneu moniae isole
´
es en Belgique pendant l’hiver 2008 a
`
2007.
Me
´
thodes. Quatre cent quarante-huit souches non duplique
´
es collectionne
´
es par 15 laboratoires ont
e
´
te
´
teste
´
es par microdilution (CLSI).
Re
´
sultats. Le taux d’insensibilite
´
(I + R) e
´
tait le suivant : pe
´
nicilline G (PEN) 11,6 % (4,0 % R), ampicilline
11,4 % (4,0 % R), amo xicilline +/– acide clavulanique 0, ce
´
faclor 10,3 % (9,6 % R), ce
´
furoxime 9,2 % (8,7 % R),
ce
´
furoxime-axetil 8,7 % (7,8 % R), ce
´
fotaxime, ceftazidime et ce
´
fe
´
pime 2,0 % (0 % R), imipe
´
ne
`
me 2,5 % (0 %
R), ciprofloxacine et ofloxacine 5,1 % (0,4 % R), le
´
vofloxacine 0,7 % (0,4 % R), moxifloxacine 0,4 % (0,2 % R),
e
´
rythromycine (ERY) 29,7 % (29,2 % R), azithromycine 29,7 % (28,8 % R), te
´
lithromycine 0 %, clindamycine
26,3 % (25,4 % R) et te
´
tracycline (TET) 21,9 % (16,5 % R). De 2001 a
`
2008, le taux d’insensibilite
´
a diminue
´
significativement pour les souches avec une re
´
sistance de bas nivea u a
`
la pe
´
nicilline (21,0 % a
`
11,6 %), les
souches re
´
sistantes a
`
la pe
´
nicilline (9,7 % a
`
4,0 %) et les souches re
´
sistantes a
`
la ciprofloxacine (11,2 % to
5,1 %). Dans les souches insensibles a
`
la pe
´
nicilline, la re
´
sistance croise
´
e entre la pe
´
nicilline et les autres
b
-lactamines e
´
tait incomple
`
te : toutes les souches restaient sensible a
`
l’amoxicilline. Le taux
d’insensibilite
´
a
`
l’e
´
rythromycine e
´
tait significativement plus e
´
leve
´
dans les souches provenant des
enfants que dans les souches provenant des adultes (43,9 %/27,34 %). Le taux d’insensibilite
´
a
`
la
pe
´
nicilline e
´
tait significativement plus e
´
leve
´
a
`
Bruxelles qu’en Flandres (22,9 %/8,1 %). L’insensibilite
´
ERY-
TET e
´
tait le phe
´
notype de re
´
sistance le plus commun (12,7 %), suivi par l’insensibilite
´
isole
´
e ERY (7,4 %) et
le phe
´
notype PEN-ERY-TET (5,8 %). La plupart des souches insensibles a
`
la pe
´
nicilline e
´
taient du type
capsulaire 19 (25 %), 14 (19,3 %), 23 (15,4 %) et 15 (13,5 %).
Conclusion. Nous avons note
´
une diminution des taux d’insensibilite
´
pour la plupart des antibiotiques.
Les taux d’insensibilite
´
restaient plus e
´
leve
´
s dans les souches provenant des enfants et la diffe
´
rence entre
le Nord et le Sud du pays est devenue moins marque
´
e.
ß 2009 Elsevier Masson SAS. Tous droits re
´
serve
´
s.
Mots cle
´
s:
S. pneumoniae
Re
´
sistance
Surveillance
R. Vanhoof et al. / Pathologie Biologie 58 (2010) 147–151
148
Page 2
(82.6%) wer e from adults with 238/370 or 64.3% from adults with
age greater or equal to 60 years. The mean age of the study
population was 53.4 years. Isolates from sputum represented
79.9% (358/448) of the specimens, 15.4% (69/448) were from
nasal swab, 2.5% (11/448) from throat, 1.8% (8/448) from sinus
and 0.4% (2/448) from respiratory pus. Overall, 79.9% the isolates
were from lower respiratory tract (LRT) specimens and 20.1%
from upper respiratory tract (URT). Isolates from sputum were
significantly more present in patients of the age group greater or
equal to 60 years (96.2% 229/238) when compared to the other
age groups: 0–5 years (12.1%; 8/66; P < 0.001), 6–15 years
(58.3%; 7/12; P < 0.001) and 16–59 years (86.4%; 114/132;
0.01 > P > 0.001). Isolates from sputum were also more present
in the age group 16–59 years (86.4%; 114/132) than in the age
groups 0–5 years (12.1%; 8/66; P < 0.001) and 6–15 years (58.3%;
7/12; 0.05 > P > 0.02). On the other hand, upper respiratory tract
isolates were significantly more present in children than in
adults (70.0% versus 30.0%; P < 0.001). This was especially due to
the age group 0–5 years in which 87.9% of the samples were from
URT. Isolates from hospitalised patients represented 62.7% (281/
448) of the isolates while 35.3% (158/448) were from ambulatory
patients and 2.0% (9/448) from long care facility patients. Of the
isolates, 64.1 % (287/448) were from male patients. Isolates from
the Northern part of the country represented 46.7% (209/448)
while 45.5% (204/448) and 7.8% (35/448) of the isolates came
from patients from the Southern part and from Brussels
respectively.
The highest intrinsic activity on a weight basis was found for
imipenem (MIC
50
of 0.004
m
g/ml) followed by amoxicillin,
amoxicillin/clavulanic acid, and telithromycin (MIC
50
0.008
m
g/
ml), penicillin G, ampicillin cefotaxim, ceftazidime, cefepime,
(MIC
50
0.015
m
g/ml), cefuroxime (MIC
50
0,03
m
g/ml), moxiflox-
acin, erythromycin, azithromycin (MIC
50
0.06
m
g/ml), tetracycline
(MIC
50
0.12
m
g/ml), cefaclor, clindamycin, (MIC
50
0.25
m
g/ml),
levofloxacin (MIC
50
0.5
m
g/ml), ciprofloxacin and ofloxacin (MIC
50
1.0
m
g/ml) (Table 1). Telithromycin, amoxicillin, amoxicillin/
clavulanic acid, moxifloxacin and levofloxacin were the com-
pounds with the lowest degree of insusceptibility followed by
cefotaxime, ceftazidime cefepime, imipenem, ciprofloxacin, oflox-
acin, cefuroxime-axetil and cefuroxime The highest degrees of
insusceptibility were found for erythromycin, azithromycin,
clindamycin and tetracycline (Table 2).
In general, isolates showing resistance to an antibiotic (IR-
isolates) were more present in children (36/78, 46.2%) than in
adults (132/370; 35.7%) though the difference was not significant.
Resistance to erythromycin was significantly higher in children
(42.3%; 33/78) than in adults (27.3%; 101/370) (0.01 > P > 0.001).
For tetracycline there was a significant difference between the age
group 0–5 year (31.8%; 21/66) and 16–59 year (18.2%; 24/132)
(0.05 > P > 0.02). No further significant differences were found in
the various age groups.
In general, the presence of isolates with decreased antibiotic
susceptibility to any of the antibiotics tested revealed to be
comparable in the three different regions: Brussels (40.0%), the
Southern part (38.7%) and the Northern part (35.9%). The only
significant difference was found for penicillin between Brussels
(22.9%, 8/35) and the Northern part (8.1%; 17/209)
(0.02 > P > 0.01). Tetracycline resistance was significantly higher
in males (25.4%; 73/287) than in females (15.5%; 16/161). As far as
the sampling site (URT and LRT) and admission type (ambulatory,
hospitalized) are concerned, no significant differences were found.
The most common resistance phenotypes were insusceptibility
to erythromycin-tetracycline (12.7%), isolated insusceptibility to
erythromycin (7.4%) followed by insusceptibility to penicillin-
erythromycin-tetracycline (5.8%). Insusceptibility to one com-
pound was present in 15.0% of the isolates. Two-, three- and
fourfold resistance was found in 15.1%, 6.5% and 0.9% respectively
of the isolates.
MICs of all betalactams rose with those of penicillin though
cross-resistance between penicillin and the other betalactams was
incomplete. The results indicate that 100% of the penicillin-
insusceptible isolates remained susceptible to amoxicillin while
82.7% of the penicillin-insusceptible isolates remained susceptible
to cefotaxime, ceftazidime, cefepime and 78.8% to imipenem.
The most important capsular types in penicillin-insusceptible
isolates were capsular types 19 (25.0%), 14 (19.3%), 23 (15.4%), 15
(13.5%), 6 (9.6%) and 9 (7.7%). Other types were capsular type 7, 24,
29, 34 and 35 (each 1.9%).
4. Discussion
The worldwide reported increase of antibiotic resistance among
S. pneumoniae together with the concomitant development of
coresistance between various unrelated classes of antimicrobials
Table 1
Susceptibility of 448 isolates of S. pneumoniae to various antimicrobial agents.
Antibiotic Number of isolates with indicated MIC value (
m
g/ml)
0.001 0.002 0.004 0.008 0.015 0.03 0.06 0.12 0.25 0.5 1 2 4 8 16 32 64
Penicillin 3 136 198
a
22 37 6 8 7 13 18
Ampicillin 5 80 226
a
49 37 8 5 6 14 17 1
Amoxicillin 2 13 199
a
149 18 22 6 4 10 20 5
Amoxicillin/clavulanate 2 13 211
a
137 19 21 6 4 10 20 5
Cefaclor 1 1 17 49 201
a
97 36 3 4 2 4 9 24
Cefuroxime
b
15 139 143
a
50 22 20 18 2 4 15 15 5
Cefotaxime 12 134 169
a
44 21 20 9 10 20 9
Ceftazidime 3 96 208
a
50 23 12 14 10 23 9
Cefepime 8 117 188
a
45 28 14 9 10 20 9
Imipenem 13 140 180
a
35 26 13 6 24 10 1
Ciprofloxacin 1 2 21 72 329
a
21––11
Levofloxacin 1 5 31 272
a
117 19 1 2
Moxifloxacin 1 4 33 173
a
204 31 1 1
Ofloxacin 1 4 18 251
a
151 21 2
Erythromycin 8 49 125 89
a
33 11 4 1 4 3 4 2 11 104
Azithromycin 1 14 55 134
a
82 18 11 4 2 4 5 3 7 108
Telithromycin 13 77 102 113
a
82 26 11 13 8 1 2
Clindamycin 1 23 57 102 147
a
4 –––210102
Tetracycline 2 14 65 135
a
8 25 11 18242212 4 36
a
MIC
50
or MIC for 50% of the isolates.
b
Distribution for cefuroxime and cefuroxime-axetil (the oral form of cefuroxime).
R. Vanhoof et al. / Pathologie Biologie 58 (2010) 147–151
149
Page 3
constitutes a problem of paramount importance. However, the
clinical relevance of the impact of resistance on the clinical
outcome remains a controversial topic [2,10–14]. Furthermore, the
epidemiology of antibiotic resistance can be influenced by various
factors and important variations can even be found in restricted
geographic areas due to differences in antibiotic policies, secular
changes and clonal shifts in the bacterial population, demographic
and geographic parameters [15–17]. In the actual survey, we have
found an insusceptibility rate for penicillin of 11.6% and noted an
ongoing decrease of resistance since the surveys of 2001–2003
(21.0% in 2001: P < 0.001). As expected, the decreasing trend of
insusceptibility was also noted for the other betalactams and all
the 2008 rates were significantly lower than the rates in the period
2001–2003. Cefaclor and cefuroxime decreased from 19.7 and
16.9% respectively in 2001 to 10.3 and 9.2% (P < 0.001 for cefaclor;
0.01 > P > 0.001 for cefuroxime). Amoxicillin decreased from 3.1%
(2003) to 0% (P < 0.001). Cefotaxime showed an insusceptibility
rate of 12.7% in 1999 which decreased to 7.3% in 2001 and 2.0% in
the actual survey (P < 0.001). Interestingly, the insusceptibility
rates for all the betalactams are now at the same level or even
lower than at the start of our surveillance programme in 1995. The
Belgian National Reference Centre [18] reported a comparable
decrease in penicillin insusceptibility in invasive isolates of
S. pneumoniae. The insusceptibility rate of 17.7% found in 2000
decreased continually to 10.0% in 2007. Furthermore, in our study,
we recorded an important decrease of isolates with high level
resistance to penicillin (MIC 2
m
g/ml). In the 2001 survey, 10.2%
of the isolates were classified as resistant to penicillin while in the
actual study 4.0% of the isolates are reported as such. Capsular
types 19, 14, 23, 15, 6 and 9 represented 90.5% of the penicillin
insusceptible isolates, which is in general agreement with the
findings of the National Reference Centre [18]. However, minor
albeit important discrepancies have to be mentioned. The
prevalence of capsular types 15 and 23 were more important in
our study than in the report of the National Reference Centre
(13.5% versus 7.6% and 15.4% versus 8.8%). However, the
surveillance of the National Reference Centre is only based on
invasive isolates from blood, CSF and other normal sterile fluids.
Importantly, in the 2008 survey, the capsular type 15 has become
an important type. Between 1995 and 2007 it was only present at a
rate between 2.0 and 5.0%. This trend was also reported by the
National Reference Centre. Moreover, the high prevalence of
capsular type 15 amongst the penicillin-insusceptible isolates can
be held responsible for the relatively low coverage rate of the
heptavalent vaccine (77.0%) in which this type is not present.
Another point of interest is the steady decrease off the Penicillin
MIC
50
value from 0.06
m
g/ml in 2003 to 0.015
m
g/ml in 2008. This
may be indicative for an ongoing population shift to the susceptible
side of the curve.
Fluoroquinolones are widely used as a treatment of respiratory
tract infections and are considered as a valid alternative in the
treatment of infections caused by resistant isolates or in patients
with penicillin allergy. Fogarty et al. [19] reported on the excellent
clinical and bacteriological cure rates of moxifloxacin in commu-
nity-acquired pneumonia due to resistant isolates of
S. pneumoniae. In a worldwide surveillance, the reported fluor-
oquinolones resistance rates were in general very low [20].
However, the use of lesser potent compounds or the use of
suboptimal dosing regimens can attribute to the emergence of
resistance. Therefore, the follow-up of resistance and the possible
shift of MIC distributions are of great importance. In our study, 5.1%
of the isolates had an MIC greater or equal to 2
m
g/ml for
ciprofloxacin compared to 15.0% in 1999. Levofloxacin insuscept-
ibility decreased from 3.3% in 3003 to 0.7% in 2008, while
insusceptibility to moxifloxacin was only rarely found and evolved
from 0.6% in 2003 to 0.4% in 2008. Interestingly, and contrary to the
betalactams, the MIC50 values of the fluoroquinolones did not shift
markedly throughout the total study period indicating an overall
high degree of stability of the pneumococcal population. The rates
of resistance to erythromycin and tetracycline remained at a high
level and telithromycin clearly appeared as the most active
compound in the macrolide-ketolide group.
Comparison and interpretation of resistance rates obtained
worldwide by different centres should be done with some caution
since several methodological parameters can influence the out-
come of the analysis. Nevertheless, important geographic varia-
tions in resistance rates for various microorganisms including
S. pneumoniae have been reported both on a global, regional,
national and even local level [6,7,21,22]. These geographic
differences can be attributed to a wide variety of parameters
including differences in antibiotic policies. However, these
variations, especially on the local level, can also be explained by
the introduction and subsequent spread of particular clones
[23,24]. In our 2008 survey, we did not find major geographical
differences in contrast with what has been reported in the past
[6,7]. In general, we have always found significant higher rates of
insusceptibility in the south (Walloon community) than in the
north (Flemish community) of the country. In the 2008 survey, the
rates between north and south were nearly identical. Importantly,
in the south we noted an important and sometimes a significant
decrease in resistance between 2003 and 2008: penicillin from
18.8 to 13.2% (NS), ciprofloxacin from 18.9 to 5.9% (P < 0.001),
erythromycin from 31.3 to 29.4% (NS) and tetracycline from 35.9 to
23.5% (0.02 > P > 0.01). The rate of isolates with complete
susceptibility rose from 43.1 to 61.3% (P < 0.001) in the same
period. In the north, we saw only a minor decrease except for
ciprofloxacin (from 11.6% to 5.3%; 0.05 > P > 0.02) and even a
significant increase in resistance for erythromycin (20.9 to 29.7%;
0.05 > P > 0.02). Changes in time can partly be attributed to better
antibiotic prescribing. However, it should be mentioned that the
decrease in resistance already started before the implementation
of the governmental campaigns to promote a better antibiotic
prescribing (2004) and the introduction of the pneumococcal
heptavalent conjugate vaccine (2007). In the period 2001–2006,
the overall outpatient antibiotic use expressed in DDD/1000
inhabitants/day (DDI) increased from 23.8 to 24.4. Amoxicillin and
penicillin DDI increased from 2.4 to 4.0 and from 4.4 to 5.5
respectively. A decrease in DDI was recorded for the macrolides
(from 2.7 to 1.9) and tetracycline (from 1.9 to 1.0). The
fluoroquinolones DDI increased to 2.4 in 2003 but decreased
Table 2
Susceptibility rates following CLSI criteria of 448 isolates of S. pneumoniae.
Antibiotic Susceptibility rates (in %)
Susceptible Intermediate Resistant
Penicillin 88.4 7.6 4.0
Ampicillin 88.8 7.4 4.0
Amoxicillin 100 0 0
Amoxicillin/clavulanate 100 0 0
Cefaclor 89.7 0.7 9.6
Cefuroxime 90.8 0.5 8.7
Cefuroxime-axetil 91.3 0.9 7.8
Cefotaxime 98.0 2.0 0
Ceftazidime 98.0 2.0 0
Cefepime 98.0 2.0 0
Imipenem 97.5 2.5 0
Ciprofloxacin 94.9 4.7 0.4
Levofloxacin 99.3 0.2 0.5
Moxifloxacin 99.6 0.2 0.2
Ofloxacin 94.9 4.7 0.4
Erythromycin 70.3 0.5 29.2
Azithromycin 70.3 0.9 28.8
Telithromycin 100 0 0
Clindamycin 73.7 0.9 25.4
Tetracycline 78.1 5.4 16.5
R. Vanhoof et al. / Pathologie Biologie 58 (2010) 147–151
150
Page 4
afterwards to 1.8 [25]. There exists a general agreement in the
scientific community that increasing the antibiotic pressure on the
bacterial ecosystem will lead eventually to an increased resistance
rate. However, the correlation between antibiotic consumption
and resistance is not always straightforward since a multiplicity of
confounding factors can interfere [26–30]. The diversity in
confounding factors requires a more in-depth analysis of all these
factors in order to fine-tune the optimization programs on
antibiotic use before their implementation. It is without discussion
that the better use of antibiotics will be a driven element in
combating the development of antibiotic resistance.
5. Conflicts of interest
The Institute of Public Health received a grant from Bayer to
support in part this study.
R. Vanhoof received a travel grant from Bayer to present this
study at the 28th RICAI in 2008.
Other authors declared no conflicts of interest.
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