PBPs and MurM variations in invasive lactam-resistant 19A Streptococcus pneumoniae ST320, ST81 and ST276 clones from Spain, 19972007
Abstract number: P1693
del Campo R., Ardanuy C., Rolo D., De la Pedrosa E., Cantón R., Fenoll A., Baquero F., Liñares J.
Background: Since PCV-7 was introduced in 2002 in Spain, a significant increase in invasive infections caused by 19A S. pneumoniae was observed. Sequential alterations in PBP sequences are the classical mechanism to acquire penicillin resistance, whereas murM mutations are required for high penicillin and cefotaxime resistance. The aim of this study was to analyze the PBPs and murM genetic variants in a 19A S. pneumoniae collection recovered before and after of the PCV introduction (19972007).
Material and Methods: Forty-two invasive 19 A S. pneumoniae isolates with both penicillin and cefotaxime resistance were collected at the Spanish Reference Laboratory for Pneumococci. Population structure was evaluated by PFGE-SmaI and MLST. Internal fragments of the PBP1a, PBP2b, PBP2x and MurM encoding genes were amplified and sequenced.
Results: The proportion of serotype 19A among penicillin resistant strains progressively increased from 2% in 1997 to 12.1% in 2007. This increase was especially noticeable in the 20052007 period. Resistance rates were as follows: tetracycline, 100%; co-trimoxazole, 88%; erythromycin, 74%; clindamycin, 74% and chloramphenicol, 38%; amoxicillin, 33% resistant and 10% intermediate resistant (IR) (MIC range 0.58). Eight different PFGE patterns were observed, and three major clonal groups were identified by MLST: ST81-Spain23F (17 isolates); ST320-Taiwan19F (16 isolates); and ST276-Denmark14 (9 isolates). Identical DNA and protein sequences were detected in all isolates for the murM gene. Two different DNA/protein alleles were observed in the pbp1a sequences, one of them related to the ST320 isolates. Four different alleles were found for the pbp2b gene, clustering two of them to ST320 isolates, another one only in ST81 isolates, and the last one present in ST81 and ST276 isolates. For the pbp2x gene two different DNA sequences were obtained, corresponding one of them to the ST320 isolates, but PBP2x aminoacid sequences were identical in all isolates.
Conclusion: In recent years, incidence of 19A invasive multirresistant S. pneumoniae isolates is increasing in Spain, mainly due to the spread of the clones ST81-Spain23F, ST276-Denmark14 and ST320-Taiwan19F. PBP1a, PBP2x, and MurM proteins are almost identical in ST81 and ST276, suggesting association between 19A capsular transformation and modified PBPs. In ST320 isolates, specific alleles were found for PBP1a and PBP2x, indicating a possible 19F/19A cps recombination event.
|Session name:||Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases|
|Location:||Vienna, Austria, 10 - 13 April 2010|
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