Combinations of PBPs and MurM protein variants in early and contemporary high-level penicillin-resistant Streptococcus pneumoniae isolates in Spain.
OBJECTIVE
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 2-8 mg/L) isolates, including 10 early (1997-1998) and 23 contemporary (2002-2004) isolates, were studied.


RESULTS
Most of the isolates belonged to clones Spain(6B)-2 (13 strains), Spain(23F)-1 (10 isolates) and Spain(14)-5 (20 isolates). Different protein variants of MurM (MA, MB5, MB6, MB9 and MB10), PBP1A (A-C), PBP2B (A-D) and PBP2X (A-C) 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 4-8 mg/L) Spain(6B)-2 isolates, [MA-A-C-A] for Spain(23F)-1 and [MB5-A-A-A] in Spain(14)-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 PBPs-MurM combinations tend to be preserved and may have an independent evolutionary history in particular clones.
Servicio de Microbiología, Hospital Universitario Ramón y Cajal, Ctra. Colmenar Km 9.1, Madrid 28034, Spain. rosacampo@yahoo.com
Rosa
R
del Campo
Fabio
F
Cafini
María Isabel
MI
Morosini
Asunción
A
Fenoll
Josefina
J
Liñares
Luis
L
Alou
David
D
Sevillano
Rafael
R
Cantón
José
J
Prieto
Fernando
F
Baquero
D000483:Alleles; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics*; D014644:Genetic Variation; D006801:Humans; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance / Q000235:genetics*; D046915:Penicillin-Binding Proteins / Q000235:genetics*; D010406:Penicillins / Q000494:pharmacology; D010453:Peptide Synthases / Q000235:genetics*; D012703:Serotyping; D013030:Spain; D013045:Species Specificity; D013296:Streptococcus pneumoniae / Q000235:genetics* / Q000302:isolation & purification
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D046915:Penicillin-Binding Proteins; D010406:Penicillins; C408066:MurM protein, Streptococcus pneumoniae; D010453:Peptide Synthases