title: Penicillin minimum inhibitory concentration drift in identical sequential Streptococcus pneumoniae isolates from colonized healthy infants.
abstract: We monitored the timing of acquisition of nasopharyngeal colonization of Streptococcus pneumoniae in 125 healthy infants during their first 2 years of life. S. pneumoniae was isolated at least once from 59 (47%) of 125 infants aged between 2 and 18 months. Twenty-four infants (19%) were colonized with penicillin-resistant S. pneumoniae at some time during the study. During the course of this investigation, we identified sequential pneumococcal isolates of the same serotype from 5 infants, in which the penicillin minimum inhibitory concentration (MIC) increased over time. For 4 of the 5 infants, sequential isolates were identical, as determined by pulsed-field gel electrophoresis. Sequential S. pneumoniae nasopharyngeal isolates from some healthy infants demonstrated drift in penicillin MIC values over time, from penicillin-susceptible to penicillin-resistant.
authors.affiliation: Children and Youth Project, University of Louisville, Louisville, KY 40202, USA.
authors.forename: B A
authors.initials: BA
authors.lastname: Sisson
authors.forename: G
authors.initials: G
authors.lastname: Buck
authors.forename: S M
authors.initials: SM
authors.lastname: Franco
authors.forename: L J
authors.initials: LJ
authors.lastname: Goldsmith
authors.forename: G P
authors.initials: GP
authors.lastname: Rabalais
mesh_terms: D002675:Child, Preschool; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008826:Microbial Sensitivity Tests; D009305:Nasopharynx / Q000382:microbiology*; D010403:Penicillin Resistance; D010406:Penicillins / Q000494:pharmacology*; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000302:isolation & purification
chemical_list: D010406:Penicillins