title: Prediction of decreased susceptibility to penicillin of Neisseria meningitidis strains by real-time PCR.
abstract: Sequence analysis of the penA gene, encoding penicillin-binding protein 2 (PBP2), in 30 penicillin-intermediate (PenI) Neisseria meningitidis strains showed altered gene sequences due to the translocation of exogenous DNA blocks derived from commensal neisseriae, which are known to have PBP2 proteins with decreased affinity for the antibiotic. In order to obtain a rapid and reproducible method for predicting the PenI phenotype, a real-time PCR assay was set up with primers and probes designed on the basis of the penA gene. The A-->G mutation at codon 566, in the transpeptidase domain of the penA gene (which is present in the whole sample of 30 PenI strains and in all the 41 sequences of PenI meningococci isolated worldwide and has been deposited in the sequence databank), was chosen as a marker of penA translocations. Two hybridization probes were designed to distinguish the wild-type penA gene in penicillin-susceptible (PenS) meningococci from the mutated penA gene at codon 566 in PenI strains. Thermal analysis of probe hybridization revealed a melting temperature difference of at least 6 degrees C between PenI and PenS strains. This real-time PCR protocol characterizes the penicillin phenotype of N. meningitidis in a few hours without DNA sequencing and is useful for rapid screening of the penicillin-intermediate genotype among meningococcal isolates.
authors.affiliation: Laboratory of Bacteriology and Medical Mycology, Istituto Superiore di Sanitá, Rome, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Stefanelli
authors.forename: Alessandra
authors.initials: A
authors.lastname: Carattoli
authors.forename: Arianna
authors.initials: A
authors.lastname: Neri
authors.forename: Cecilia
authors.initials: C
authors.lastname: Fazio
authors.forename: Paola
authors.initials: P
authors.lastname: Mastrantonio
mesh_terms: D001483:Base Sequence; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009154:Mutation; D009345:Neisseria meningitidis / Q000187:drug effects*; D010403:Penicillin Resistance / Q000235:genetics*; D010406:Penicillins / Q000494:pharmacology*; D016133:Polymerase Chain Reaction / Q000379:methods*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012261:Ribonucleoproteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013696:Temperature; D013997:Time Factors
chemical_list: C443675:PBP2 protein, S cerevisiae; D010406:Penicillins; D012261:Ribonucleoproteins; D029701:Saccharomyces cerevisiae Proteins