1 Servicio de Microbiología, Hospital Donostia, Paseo Dr. Beguiristain s/n, 20014 San Sebastián (Gipuzkoa); 2 Departamento de Medicina Preventiva y Salud Pública, Facultad de Medicina, Universidad del País Vasco, San Sebastián, Spain
Received 17 October 2002; returned 20 November 2002; revised 25 November 2002; accepted 26 November 2002
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Keywords: rifampicin resistance, erythromycin resistance, mechanism of resistance
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
In this article, the isolation and characterization of the S. pneumoniae Spain14-5 clone strains whose resistance was expanded to new families of antibiotics are described.
![]() |
Materials and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Both current1 and previously considered reference strains of the Spain14-5 international clone (strain MS22, ATCC 700902, and strain VH14, ATCC 700672) were used as controls. The presence of the mef(A), erm(B) and erm(A) [erm(TR)] genes was studied by PCR as described previously.6 Point mutations at Ser-79 in the parC and at Ser-81 in the gyrA genes, known to confer fluoroquinolones resistance, were studied by a PCR-RFLP assay7 and were confirmed by gene sequencing. Mutations in the rpoB gene responsible for rifampicin resistance were studied by sequencing in the two rifampicin-resistant isolates, as described previously.8
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
|
Point mutations at Ser-79 in the parC and at Ser-81 in the gyrA genes were found in all isolates. In all erythromycin-resistant isolates, the presence of the erm(B) gene was detected and two rpoB mutations (Thr-318Ile and His-425
Asn) were found in the two rifampicin-resistant isolates. All isolates from the 16 patients were susceptible to vancomycin (MIC
0.5 mg/L), quinupristin/dalfopristin (MIC
1 mg/L) and linezolid (MIC
2 mg/L). Telithromycin MICs for all isolates were
0.5 mg/L.
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Isolates belonging to the most common clones usually share identical susceptibility patterns, but regional selective pressure in different parts of the world can add resistance to other antibiotics. The susceptibility referred to for the Spain14-5 clone by the PMEN1 showed resistance to a high number of antimicrobials. Now resistance to new families of antibiotics, and resistance to cefotaxime and amoxicillin shown by the majority of the isolates turns it into the international clone with one of the widest, if not the widest, spectrum of antibiotic resistance among all the clones described.
Macrolide and lincosamide resistance is a frequent event among other international multiresistant S. pneumoniae clones1,5 and five of the 18 strains included in the original description of the Spain14-5 clone were erythromycin resistant, although the mechanism of its resistance was not determined.2 In all the strains described here the erythromycin resistance was due solely to the presence of the erm(B) gene, with the mef(A) and erm(A) genes not being found. Fluoroquinolone resistance is still an infrequent event but may well increase in the near future. All the isolates described here were resistant to fluoroquinolones, and fluoroquinolone resistance has been described previously in the S. pneumoniae Spain23F-1 and Spain9v-3 clones.9 Eight years ago we made a short reference to the two isolates with resistance to rifampicin, but at that time they were not characterized as belonging to the Spain14-5 clone and nor were the mutations implicated in the mechanism of resistance studied.10 The His-425Asn mutation found in our isolates has been described previously as conferring resistance to rifampicin in S. pneumoniae.8
Ketolides, of which telithromycin is the first to be registered for clinical use, and quinupristin/dalfopristin, which belongs to the macrolidelincosamidestreptogramin B class, are new compounds that have retained activity against these strains even though they are resistant to macrolides and clindamycin. These drugs together with azalides and vancomycin represent the last therapeutic options against this clone with enhanced multidrug resistance.
MLST was a very useful method for the characterization of these multiresistant S. pneumoniae isolates. The clone was initially characterized by PFGE but the MLST proved to be a more discriminatory typing method as it allowed us to subdivide the clone into two ST types. Using the database available at the MLST web site (www.mlst.net), five different ST types belonging to the Spain14-5 clone can currently be found, ST18 and ST17 being the more common types in this database. Most of the strains presented in this work were ST17, which by BOX-PCR could be further subdivided into two varieties. The three different phenotypes of antibiotic resistance coincided with the three different molecular patterns (ST17 BOX-PCR I, ST17 BOX-PCR II and ST18 BOX-PCR I). Each type could represent a different lineage with a different spreading ability.
We hope that these multiresistant strains will not reach the pandemic diffusion that other S. pneumoniae belonging to other international multiresistant clones have reached. Nevertheless, it will be necessary to maintain a continuous monitoring of the resistant S. pneumoniae to warn against the spread of these organisms. In view of such a scene of antimicrobial resistance, the introduction of new vaccines or new immunization strategies is becoming more and more necessary for the future prevention of S. pneumoniae infections.
![]() |
Footnotes |
---|
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
2 . Coffey, T. J., Berron, S., Daniels, M., Garcia-Leoni, M. E., Cercenado, E., Bouza, E. et al. (1996). Multiply antibiotic-resistant Streptococcus pneumoniae recovered from Spanish hospitals (19881994): novel major clones of serotypes 14, 19F and 15F. Microbiology 142, 274757.[Abstract]
3 . National Committee for Clinical Laboratory Standards. (2002). Performance Standards for Antimicrobial Susceptibility Testing: Twelfth Informational Supplement M100-S12. NCCLS, Wayne, PA, USA.
4 . National Committee for Clinical Laboratory Standards. (2000). Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow AerobicallyFifth Edition: Approved Standard M7-A5. NCCLS, Wayne, PA, USA.
5 . Marimón, J. M., Iglesias, L., Vicente, D. & Perez-Trallero, E. (2003). Molecular characterization of erythromycin-resistant clinical isolates of the four major antimicrobial-resistant Spanish clones of Streptococcus pneumoniae (Spain23F-1, Spain6B-2, Spain9v-3, Spain14-5). Microbial Drug Resistance, in press.
6 . Sutcliffe, J., Grebe, T., Tait-Kamradt, A. & Wondrack, L. (1996). Detection of erythromycin-resistant determinants by PCR. Antimicrobial Agents and Chemotherapy 40, 25626.[Abstract]
7 . Pan, X. S., Ambler, S., Mehtar, S. & Fisher, L. M. (1996). Involvement of topoisomerase IV and DNA gyrase as ciprofloxacin targets in Streptococcus pneumoniae. Antimicrobial Agents and Chemotherapy 40, 23216.[Abstract]
8
.
Padayachee, T. & Klugman, K. P. (1999). Molecular basis of rifampin resistance in Streptococcus pneumoniae. Antimicrobial Agents and Chemotherapy 43, 23615.
9
.
McGee, L., Goldsmith, C. E. & Klugman, K. P. (2002). Fluoroquinolone resistance among clinical isolates of Streptococcus pneumoniae belonging to international multiresistant clones. Journal of Antimicrobial Chemotherapy 49, 1736.
10 . Garcia-Arenzana, J. M., Montes, M. & Perez-Trallero, E. (1994). Are rifampin-resistant Streptococcus pneumoniae strains a consequence of the increase in cases of tuberculosis? Clinical Infectious Diseases 19, 3601.[ISI][Medline]