Open AccessGenetic Diversity of the tet (M) Gene in Tetracycline-Resistant Clonal Lineages of Streptococcus pneumoniae
Author(s) -
Neil Doherty,
Krzysztof Trzciński,
Paul Pickerill,
Piotr Zawadzki,
Christopher G. Dowson
Publication year - 2000
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.44.11.2979-2984.2000
Subject(s) - tetracycline , biology , serotype , microbiology and biotechnology , streptococcus pneumoniae , clone (java method) , antibacterial agent , virology , streptococcaceae , gene , antibiotics , genetics
The aim of the present study was to examine the stability and evolution oftet (M)-mediated resistance to tetracyclines among members of different clonal lineages ofStreptococcus pneumoniae . Thirty-two tetracycline-resistant isolates representing three national (Spanish serotype 14, Spanish serotype 15, and Polish serotype 23F) and one international (Spanish serotype 23F) multidrug-resistant epidemic clones were all found to betet (M) positive andtet (O),tet (K), andtet (L) negative. These isolates all carried the integrase gene,int , which is associated with the Tn1545 -Tn916 family of conjugative transposons. High-resolution restriction analysis oftet (M) products identified six alleles,tet (M)1 totet (M)6:tet (M)1 totet (M)3 andtet (M)5 in isolates of the Spanish serotype 14 clone,tet (M)4 in both the Spanish serotype 15 and 23F clones, andtet (M)6, the most divergent allele, in the Polish 23F clone. This indicates thattet (M) variation can occur at the inter- and intraclone levels in pneumococci. Two alleles ofint were identified, withint1 being found in all isolates apart from members of the international Spanish 23F clone, which carriedint2 . Susceptibility to tetracycline, doxycycline, and minocycline was evaluated for all isolates with or without preincubation in the presence of subinhibitory concentrations of tetracyclines. Resistance to tetracyclines was found to be inducible in isolates of all clones; however, the strongest induction was observed in the Spanish serotype 15 and 23F clones carryingtet (M)4. Tetracycline was found to be the strongest inducer of resistance, and minocycline was found to be the weakest inducer of resistance.