An unusual phenotype of Enterococcus faecalis in Greece expressing low-level resistance to clindamycin and dalfopristin but susceptibility to quinupristin-dalfopristin

Abstract number: p1592

Maniati  M., Kontos  F., Liakos  P., Petinaki  E., Spiliopoulou  I., Maniatis  A.

Objectives: 

To investigate the resistance mechanism of a new described phenotype among Enterococcus faecalis expressing low-level resistance to clindamycin and dalfopristin but susceptibility to quinupristin-dalfopristin (Q-D).

Methods: 

In Greece, during 2005, three Enterococcus faecalis isolates, expressing this unusual phenotype, were recovered from urine samples. The isolates were studied by PCR for the lsa-gene and by PFGE. Nucleotide sequencing analysis of lsa and 309 bp of the upstream region was performed. The isolates were also tested by RT-PCR for the expression of the lsa-gene.

Results: 

The isolates belonged to three distinct clones and carried the lsa-gene. No stop codons were found in any strain, while some point mutations in the lsa-gene were detected. Comparing the lsa mRNA production of these unusual strains with that obtained from fully Q-D resistant ones no quantitative differences were found.

Conclusions: 

The findings of the present study clearly show that the resistance mechanism of quinupristin-dalfopristin is not only correlated with the presence and the expression of the lsa-gene. Some mutations detected in the lsa gene probably are responsible for the production of an Lsa protein with decreased activity, resulting to the Q-D susceptibility.