JAC Advance Access originally published online on March 13, 2006
Journal of Antimicrobial Chemotherapy 2006 57(5):983-986; doi:10.1093/jac/dkl083
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Combinations of PBPs and MurM protein variants in early and contemporary high-level penicillin-resistant Streptococcus pneumoniae isolates in Spain
1 Servicio de Microbiología, Hospital Universitario Ramón y Cajal, Ctra. Colmenar Km 9.1, Madrid 28034, Spain; 2 Departamento de Microbiología, Facultad de Medicina, Universidad Complutense, Avda Complutense s/n, Madrid 28040, Spain; 3 Departamento de Microbiología, Instituto Nacional de Salud Carlos III, Ctra Majadahonda-Pozuelo Km 2, Majadahonda 28220, Spain; 4 Servicio de Microbiología, Hospital Universitario de Bellvitge, Feixa Llarga s/n L'Hospitalet de Llobregat, Barcelona 08097, Spain
Received 29 December 2005; returned 12 January 2006; revised 10 February 2006; accepted 22 February 2006
* Corresponding author. Tel: +34-91-3368542; Fax: +34-91-3368809; E-mail: rosacampo{at}yahoo.com
Objectives: High-level penicillin resistance in Streptococcus pneumoniae requires extensive re-modulation of the penicillin-binding proteins (PBPs), and murM gene function is also required for the expression of resistance. In this work, we determined whether specific changes in PBPs were associated with specific MurM variants.
Methods: Two collections of highly penicillin-resistant (MIC 28 mg/L) isolates, including 10 early (19971998) and 23 contemporary (20022004) isolates, were studied.
Results: Most of the isolates belonged to clones Spain6B-2 (13 strains), Spain23F-1 (10 isolates) and Spain14-5 (20 isolates). Different protein variants of MurM (MA, MB5, MB6, MB9 and MB10), PBP1A (AC), PBP2B (AD) and PBP2X (AC) were recognized, including two murM alleles not previously described. Particular [MurM-PBP1A-2B-2X] allelic combinations were predominant among the different clones, including [MA-B-B-B] for old (MIC 2 mg/L) and [MB10-C-A-B] for recent (MIC 48 mg/L) Spain6B-2 isolates, [MA-A-C-A] for Spain23F-1 and [MB5-A-A-A] in Spain14-5 isolates.
Conclusions: Although S. pneumoniae has a basic recombinational population structure, our results indicate remarkable conservation of PBPs and MurM protein types within each clone. This suggests that particular PBPsMurM combinations tend to be preserved and may have an independent evolutionary history in particular clones.
Keywords: resistance , clones , mutations , penicillin-binding proteins
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