ABSTRACT
Sequence analysis of the pbp genes from 20 Streptococcus pneumoniae isolates from Turkey (eight with high-level penicillin-resistance, nine with low-level penicillin-resistance, and three that were penicillin-susceptible) was performed and phylogenetic trees were constructed. Most isolates clustered together within a single branch that was distinct from sequences deposited previously in GenBank, which suggests that these isolates have probably evolved following new recombination events. The most prominent active-site mutations, which have also been associated previously with resistance, were T371A in PBP1a, E481G followed by T451A in PBP2b, and T338A in PBP2x. All isolates also possessed a (570)SVES/TK(574) block in the PBP2b sequence, instead of the QLQPT sequence of R6, which is fairly uncommon in GenBank sequences. This is the first study to analyse alterations in the pbp sequences of pneumococci isolated in Turkey.
Subject(s)
Bacterial Proteins/genetics , Mutation , Penicillin Resistance/genetics , Penicillin-Binding Proteins/genetics , Streptococcus pneumoniae/genetics , Binding Sites/genetics , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , Evolution, Molecular , Humans , Molecular Sequence Data , Phylogeny , Pneumococcal Infections/microbiology , Recombination, Genetic , Sequence Analysis, DNA , Sequence Homology, Amino Acid , Streptococcus pneumoniae/drug effects , Streptococcus pneumoniae/isolation & purification , TurkeyABSTRACT
Fecal specimens from 50 healthy volunteers living in Izmir, Turkey, were examined for the presence of beta-lactamase producing Escherichia coli by selection on agar plates containing ampicillin (10 mg/L). Thirty-nine (78%) of the strains were ampicillin-resistant and ampicillin MIC50 values for these isolates were > or =1024 microg/ml (range 32- > or =1024 microg/ml). Ampicillin MIC values remained above 64 microg/ml in 16 (41%) strains despite addition of clavulanic acid (2 mg/L). Beta-lactamase production of the clavulanate-resistant strains was further investigated by analytical isoelectric focusing (pI). Enzymes with pIs of 5.4, 5.6, 7.4, 7.6 and >8.5 were detected. Sixty-nine percent of the isolates produced a pI 5.4 enzyme that cofocused with TEM-1. Beta-lactamase assays revealed that hyperproduction of these enzymes was the predominant mechanism for clavulanate resistance. Twelve (75%) of the isolates were able to transfer their ampicillin resistance. The ampicillin and ampicillin plus clavulanic acid MIC values of all transconjugants were above 256 microg/ml. Transferable ampicillin resistance was associated with resistance to other antibacterials at the following frequencies: tetracycline 92%, trimethoprim 83%, streptomycin 50%, gentamicin 25%, and chloramphenicol 8%. In conclusion, it has been suggested that commensal bacteria in normal populations make up the largest reservoir of antibiotic-resistant genes. Although the exact molecular mechanisms could not be determined, the current study shows that the incidence of ampicillin and clavulanic acid resistance is also high in commensal fecal flora.
