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Antimicrobial Agents and Chemotherapy, May 2005, p. 2126-2129, Vol. 49, No. 5
0066-4804/05/$08.00+0 doi:10.1128/AAC.49.5.2126-2129.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
High Genetic Diversity of Ciprofloxacin-Nonsusceptible Isolates of Streptococcus pneumoniae in Poland
Ewa Sadowy,*
Rados
aw Izdebski,
Anna Skoczy
ska,
Marek Gniadkowski, and
Waleria Hryniewicz
National Institute of Public Health, Che
mska 30/34, 00-725 Warsaw, Poland
Received 18 November 2004/
Returned for modification 24 December 2004/
Accepted 27 January 2005

ABSTRACT
We have analyzed the susceptibility to ciprofloxacin of 697
pneumococcal isolates collected in 1998-2002 in Poland from
patients with respiratory tract diseases. Thirty-one ciprofloxacin-nonsusceptible
isolates (MICs,

4 µg/ml) were identified, of which two
were resistant to levofloxacin (MIC, 8 µg/ml). Serotyping,
pulsed-field gel electrophoresis, multilocus sequence typing,
and the analysis of resistance determinants showed their great
genetic diversity.

TEXT
The constant increase in resistance of
Streptococcus pneumoniae to ß-lactams, macrolides, and tetracyclines has evoked
a need for alternative options in the treatment of pneumococcal
infections. New fluoroquinolones, such as levofloxacin and moxifloxacin,
are now considered to play this role in the case of infections
in adults. However, the first pneumococci resistant to these
compounds have appeared in some countries (
5,
8,
9,
17,
19,
21,
32), and therapeutic failures have been reported (
22). Mechanisms
of quinolone resistance in
S. pneumoniae include increased activity
of the membrane pump PmrA (
13) and modifications of the cellular
drug targets topoisomerase IV (ParC/ParE) and DNA gyrase (GyrA/GyrB)
(
11,
18,
28,
29), located in their so-called quinolone-resistance-determining
regions (QRDRs) (
28,
29). Selection of these mechanisms is partially
exerted by the common use of an older quinolone, ciprofloxacin,
which is not recommended as an antipneumococcal agent. Each
of the mechanisms alone confers low-level ciprofloxacin nonsusceptibility
and increases the risk of acquisition of further changes (
14).
The accumulation of mutations in both ParC/ParE and GyrA/GyrB
(
3,
7,
18,
30,
32) results in high-level nonsusceptibility to
ciprofloxacin and resistance to the newer compounds. Therefore,
ciprofloxacin nonsusceptibility is an important measure of the
actual and potential quinolone resistance of pneumococci (
33).
The situation concerning resistance to quinolones in S. pneumoniae in Central and Eastern Europe has not been investigated yet. The aim of our study was to evaluate the frequency of ciprofloxacin nonsusceptibility in S. pneumoniae in Poland and to reveal the genetic relatedness among nonsusceptible isolates.
(This work was presented at RGPI-2, 10 to 12 December, 2004, Berlin, Germany.)
Six-hundred ninety-seven S. pneumoniae isolates were obtained from individual patients with lower respiratory tract diseases between 1998 and 2002 in 40 medical centers in 26 cities. The isolates were derived from sputum (562 isolates, 80.6%), bronchoalveolar lavage (75 isolates, 10.8%), and transtracheal aspirate (60 isolates, 8.6%). MICs of ciprofloxacin (Bayer AG, Leverkusen, Germany) were evaluated by the National Committee for Clinical Laboratory Standards microdilution method (26); due to the lack of an accepted breakpoint, a pneumococcal isolate was considered nonsusceptible to ciprofloxacin when its MIC was
4 µg/ml (1, 8, 17). Such isolates were tested as described above with levofloxacin (Aventis Pharma, Romainville, France), moxifloxacin (Bayer AG, Leverkusen, Germany), penicillin (Sigma Chemical Company, St. Louis, Mo.), and erythromycin (Fluka, Buchs, Switzerland), using the National Committee for Clinical Laboratory Standards-approved breakpoints (26). PCR amplification and sequencing of QRDRs of gyrA, gyrB, parC, and parE genes was performed as described by Pan et al. (29). The reserpine-mediated inhibition of quinolone efflux was performed according to the method of Broskey et al. (4). Serotypes of the isolates were determined by the capsular swelling method at the Statens Serum Institute (Copenhagen, Denmark). Pulsed-field gel electrophoresis (PFGE) typing was performed as described by Lefèvre et al. (23); isolates were considered indistinguishable when they shared PFGE patterns and were considered related when they showed a difference of one to three bands. Multilocus sequence typing (MLST) was performed as proposed by Enright and Spratt (10); the Internet-accessible database (http://www.mlst.net) was used to assign numbers to alleles and sequence types (STs).
Thirty-one isolates, i.e., 4.4% of the all 697 isolates studied (Table 1), appeared nonsusceptible to ciprofloxacin, and they originated from 12 towns uniformly distributed in the country. Among these isolates, five were penicillin nonsusceptible, two were erythromycin resistant and two (BY-2 and BY-3; 0.3%) were resistant to levofloxacin (MIC, 8 µg/ml) and intermediate to moxifloxacin (MIC, 2 µg/ml), which correlated with their high-level ciprofloxacin nonsusceptibility (MICs,
32 µg/ml). Both quinolone-resistant isolates were penicillin and erythromycin susceptible. No significant difference in patients' ages between the ciprofloxacin-nonsusceptible and -susceptible groups was found (56.7 ± 19.6 and 52.8 ± 21.2 years, respectively; P = 0.3). The prevalence of ciprofloxacin nonsusceptibility in S. pneumoniae is generally low worldwide; e.g., in the United States, it remained within the range of 1.2 to 1.6% during 1994-2000 (6). However, in some countries, such as Hong Kong, Ireland, and Spain, it has reached levels of 17.8%, 15.2%, and 5%, respectively (12, 15, 17). In Canada, the frequency of ciprofloxacin nonsusceptibility increased from 0% in 1993 to 1.7% in 1997-1998 following the increase in quinolone consumption (8). Therefore, while the observed rate of resistance to newer quinolones remains low in Poland (0.3%), the ciprofloxacin nonsusceptibility seems to be significant. Ciprofloxacin was introduced into the country in 1991; in 2002, its consumption in ambulatory care in Poland amounted to 0.5 defined daily doses/1,000 inhabitants/day, while in Spain it was 2.3-fold higher (16).
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TABLE 1. Ciprofloxacin-nonsusceptible S. pneumoniae isolates: serotypes, susceptibility to quinolones, resistance determinants, PFGE types, and MLST characteristics
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The reserpine-inhibited efflux was active in 19 ciprofloxacin-nonsusceptible
isolates and absent in 10 isolates (Table
1). In 11 isolates,
the efflux was the sole determinant of nonsusceptibility. Alterations
in QRDRs of ParC/ParE or GyrA/GyrB were identified for 18 isolates,
and they included predominantly single ParC mutations (15 isolates)
at mutational hot spot Ser79 or Asp83 (
29). Among them, the
Ser79Phe substitution was the most common (10 isolates). A single
isolate possessed the Pro454Ser substitution in ParE, which
has been described before for clinical isolates (
7,
9) and laboratory
mutants (
25). The role of some of the other observed substitutions
is most probably negligible (
3,
20,
31). The two levofloxacin-resistant
isolates, in addition to the ParC mutation Asp83Asn, had the
hot spot alteration Ser81Phe in GyrA (
2). The proportions of
frequency of the mechanisms of ciprofloxacin nonsusceptibility
vary among countries; however, the alterations only in ParC/ParE
seem to dominate (
3,
4,
6,
11,
29,
30), reflecting the fact
that ParC/ParE is a primary target for ciprofloxacin in pneumococcus
(
28,
29).
Eighteen serotypes were observed among the ciprofloxacin-nonsusceptible pneumococci, with the most common, 23F, being represented by five isolates (Table 1). Twenty-eight PFGE patterns were identified, and these could be classified into 25 distinct types. Three of the types (G, H, and Q) were differentiated further into two subtypes each, and one of these contained the levofloxacin-resistant isolates (type G). The results indicated the remarkable clonal diversity of ciprofloxacin-nonsusceptible S. pneumoniae in Poland, and suggested that they probably arose from multiple independent selection events. Such variability seems to be typical for the organism (24, 27), except in some countries, e.g., Spain, where clones Spain9V-3 and Spain23F-1 constitute 30% of ciprofloxacin-nonsusceptible pneumococci (1). Sixteen isolates, representing serotypes associated with the multiresistant international clones (6A, 6B, 9V, 14, 15A, 19A, 19F, and 23F), and the two levofloxacin-resistant isolates were subjected to MLST (Table 1). In general, the isolates were unrelated to the international clones; however, two and one isolates represented Spain9V-3 (ST156) and Spain23F-1 (ST81) clones, respectively. This observation is noteworthy, since the effective spread of such clones may quickly increase the rate of quinolone nonsusceptibility in a local pneumococcal population, as shown in Hong Kong (17). The levofloxacin-resistant isolates belonged to ST191, which was observed before in some European and South American countries (http://www.mlst.net).
In summary, the current frequency of ciprofloxacin-nonsusceptible pneumococci in Poland, although not alarming, is remarkable. The circulation of strains that are prone to develop resistance also to newer quinolones may compromise this therapeutic option in the future and undoubtedly requires permanent epidemiological surveillance.

ACKNOWLEDGMENTS
We thank Pawe

Grzesiowski for help with statistical calculations
and Anna Klarowicz and Agnieszka Mrówka for their technical
assistance.
This study was partially financed by a grant from the Polish Committee for Scientific Research (3P0A 062 23). We acknowledge the use of the pneumococcal MLST database which is located at Imperial College, London, and is funded by the Wellcome Trust.

FOOTNOTES
* Corresponding author. Mailing address: Department of Molecular Microbiology, National Institute of Public Health, ul. Che

mska 30/34, 00-725 Warsaw, Poland. Phone: 48 22 851 43 88. Fax: 48 22 841 29 49. E-mail:
ewasadowy{at}cls.edu.pl.


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Antimicrobial Agents and Chemotherapy, May 2005, p. 2126-2129, Vol. 49, No. 5
0066-4804/05/$08.00+0 doi:10.1128/AAC.49.5.2126-2129.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
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