Detection of penicillin-binding protein 2b gene alteration in Streptococcus mitis by polymerase chain reaction.
Three isolates of beta-lactam-resistant streptococci from the saliva of healthy adults were identified as Streptococcus mitis. Minimum inhibitory concentrations (MICs) were 2 to 4 micro g/ml for ampicillin (ABPC) and 64 to more than 128 micro g/ml for cefaclor (CCL). To determine the position of base alterations of the penicillin-binding protein 2b ( pbp2b) gene, upstream primers containing possible mutation points were designed, and used for polymerase chain reaction (PCR), together with a downstream primer. Alterations adjacent to the conserved motifs of the pbp2b gene were apparent. DNA sequencing data indicated replacements in deduced amino acid sequences in all resistant isolates: from threonine to alanine just after the serine-serine-asparagine (SSN) motif, and from alanine to glycine two residues downstream of the lysine-threonine-glycine (KTG) motif. These changes were the same as those in penicillin-resistant Streptococcus pneumoniae (PRSP), suggesting importance for the enzymatic activity of the protein. Thus, Beta-lactam susceptibility of S. mitis may be partially predicted by PCR using our primer set for pbp2b.
Second Department of Oral and Maxillofacial Surgery, Tsurumi University School of Dental Medicine, Yokohama, Japan. usui-h@tsurumi-u.ac.jp
Hiroyuki
H
Usui
Ayuko
A
Takao
Ayako
A
Nakayama
Hiroyuki
H
Nagashima
Fumihiko
F
Sasaki
Nobuko
N
Maeda
Katsunori
K
Ishibashi
D019881:Aminoacyltransferases; D000667:Ampicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D002433:Cefaclor / Q000494:pharmacology; D017931:DNA Primers; D005798:Genes, Bacterial / Q000235:genetics*; D006602:Hexosyltransferases / Q000235:genetics*; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D002267:Muramoylpentapeptide Carboxypeptidase / Q000235:genetics*; D009154:Mutation; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012463:Saliva / Q000382:microbiology; D034361:Streptococcus mitis / Q000187:drug effects / Q000235:genetics*; D018440:beta-Lactam Resistance
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D017931:DNA Primers; D046915:Penicillin-Binding Proteins; D002433:Cefaclor; D000667:Ampicillin; D019881:Aminoacyltransferases; C478701:penicillin-binding protein 2b, Streptococcus; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase