Open AccessPenicillin-Binding Protein Gene Alterations in Streptococcus uberis Isolates Presenting Decreased Susceptibility to Penicillin
Author(s) -
Marisa Haenni,
Laure Galofaro,
Mathilde Ythier,
Marlyse Giddey,
Paul Majcherczyk,
Philippe Moreillon,
JeanYves Madec
Publication year - 2010
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.00915-09
Subject(s) - streptococcus uberis , penicillin , microbiology and biotechnology , mastitis , biology , streptococcus agalactiae , pathogen , penicillin binding proteins , mutant , streptococcus , antibiotics , bacteria , gene , genetics
Streptococcus uberis is an environmental pathogen commonly causing bovine mastitis, an infection that is generally treated with penicillin G. No field case of true penicillin-resistantS. uberis (MIC > 16 mg/liter) has been described yet, but isolates presenting decreased susceptibility (MIC of 0.25 to 0.5 mg/liter) to this drug are regularly reported to our laboratory. In this study, we demonstrated thatS. uberis can readily develop penicillin resistance in laboratory-evolved mutants. The molecular mechanism of resistance (acquisition of mutations in penicillin-binding protein 1A [PBP1A], PBP2B, and PBP2X) was generally similar to that of all other penicillin-resistant streptococci described so far. In addition, it was also specific toS. uberis in that independent resistant mutants carried a unique set of seven consensus mutations, of which only one (Q554 E in PBP2X) was commonly found in other streptococci. In parallel, independent isolates from bovine mastitis with different geographical origins (France, Holland, and Switzerland) and presenting a decreased susceptibility to penicillin were characterized. No mosaic PBPs were detected, but they all presented mutations identical to the one found in the laboratory-evolved mutants. This indicates that penicillin resistance development inS. uberis might follow a stringent pathway that would explain, in addition to the ecological niche of this pathogen, why naturally occurring resistances are still rare. In addition, this study shows that there is a reservoir of mutated PBPs in animals, which might be exchanged with other streptococci, such asStreptococcus agalactiae , that could potentially be transmitted to humans.