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J. Microbiol. Biotechnol. 2011; 21(12): 1345-1351

Published online December 28, 2011 https://doi.org/10.4014/jmb.1105.05045

Copyright © The Korean Society for Microbiology and Biotechnology.

pep27 and lytA in Vancomycin-Tolerant Pneumococci

Alma Olivares 1, 2, Jose Olivares Trejo 2, Jose Arellano-Galindo 1, Gerardo Zuniga 3, Gerardo Escalona 1, Juan Carlos Vigueras 1, Paula Marin 1, 3, Juan Xicohtencatl 1, Pedro Valencia 1 and Norma Velazquez-Guadarrama 1*

Bacteriology Laboratory, Federico Gomez Children's Hospital of Mexico, Dr. Marquez 162, Mexico, Bacteriology Laboratory, Federico Gomez Children's Hospital of Mexico, Dr. Marquez 162, Mexico, 1Bacteriology Laboratory, Federico Gomez Children's Hospital of Mexico, Dr. Marquez 162, Mexico, 1Genomics Science Department, Autonomous University of Mexico City, San Lorenzo 290, Mexico, 1Genomics Science Department, Autonomous University of Mexico City, San Lorenzo 290, Mexico, 1Genomics Science Department, Autonomous University of Mexico City, San Lorenzo 290, Mexico, 2National School of Biological Science, National Polytechnic Institute, Plan de Ayala S/N, Mexico, 2National School of Biological Science, National Polytechnic Institute, Plan de Ayala S/N, Mexico, 2National School of Biological Science, National Polytechnic Institute, Plan de Ayala S/N, Mexico

Received: May 23, 2011; Accepted: August 30, 2011

Abstract

Vancomycin therapy failure due to the emergence of
tolerance in pneumococci is increasing. The molecular
mechanism of tolerance is not clear, but lytA and pep27 are
known to be involved. Our aim was to evaluate the
expression of both genes in vancomycin-tolerant Streptococcus
pneumoniae (VTSP) strains. Eleven VTSP strains from a
total of 309 clinical isolates of S. pneumoniae from 1997 to
2006 were classified according to the criteria of Liu and
Tomasz. All VTSP strains were evaluated for susceptibility
according to CLSI criteria, serotype by the Quellung test,
and clonality by PFGE. The expressions of lytA and pep27
were analyzed in different growth phases by RT-PCR with
and without vancomycin. Eighty-two percent of VTSP
strains showed resistance to penicillin, and 100% were
sensitive to vancomycin and cefotaxime. The most frequent
serotypes of VTSP strains were 23F (4/11) and 6B (3/11).
Clonal relationship was observed in only two strains. No
significant changes were observed in pep27 expression in
the three phases of growth in VTSP strains with and
without vancomycin. Interestingly, pep27 expression in the
stationary phase in the non-tolerant reference strain R6
was significantly higher. However, no significant differences
in lytA expression were observed between VTSP and R6
strains during the phases of growth analyzed. The absence
of changes in pep27 expression in VTSP strains in the
stationary phase may be related to their ability to tolerate
high antibiotic concentrations, and thus, they survive and
remain in the host under the antibiotic selective pressure
reflected in therapeutic failure.

Keywords: Tolerance, vancomycin,, Streptococcus pneumoniae, lytA, pep27