title: Predominance of the multiresistant 23F international clone of Streptococcus pneumoniae among isolates from Mexico.
abstract: During a surveillance study to determine the relative prevalence of capsular types of Streptococcus pneumoniae and antimicrobial susceptibility of invasive isolates in children <5 years old in Mexico City, 220 isolates were collected. The serotype 23F was the most common found, followed by types 6A + B, 14, 19F, and 19A. Diminished susceptibility to penicillin was detected in 106 isolates (48.2%), and high penicillin resistance was found in 49 strains (22.2%), 31 belonging to type 23F. Resistance was also observed to erythromycin (13.1%), to chloramphenicol (43.1%), and to cefotaxime (10.9%). No strains were resistant to ofloxacin or vancomycin. Forty-four of the highly penicillin resistant isolates (penicillin MIC > or =2.0 microg/ml) were examined with molecular fingerprinting techniques; 29 (65.9%) of these isolates (all except two strains) were serotype 23F and shared subtype variants of PFGE type A characteristic of the internationally spread Spanish/USA clone of S. pneumoniae. These strains were also resistant to trimethoprim/sulfametoxasole (TMP/SMX), chloramphenicol, and tetracycline, and most of them were susceptible to erythromycin. Another 6 of the highly penicillin-resistant strains (serogroups 9 and 14) showed PFGE fingerprints and antimicrobial susceptibility pattern characteristic of a second internationally spread clone (French/Spanish clone) and carried resistance to penicillin and TMP/SMX. The rest of the 9 penicillin-resistant isolates were represented by 7 distinct additional PFGE types. The findings suggest that almost 80% of all highly penicillin resistant strains may have been "imported" into Mexico.
authors.affiliation: Instituto Nacional de Salud Pública, Cuernavaca, Mor., México.
authors.forename: G
authors.initials: G
authors.lastname: Echániz-Aviles
authors.forename: M E
authors.initials: ME
authors.lastname: Velázquez-Meza
authors.forename: M N
authors.initials: MN
authors.lastname: Carnalla-Barajas
authors.forename: A
authors.initials: A
authors.lastname: Soto-Noguerón
authors.forename: J L
authors.initials: JL
authors.lastname: Di Fabio
authors.forename: F
authors.initials: F
authors.lastname: Solórzano-Santos
authors.forename: Y
authors.initials: Y
authors.lastname: Jiménez-Tapia
authors.forename: A
authors.initials: A
authors.lastname: Tomasz
mesh_terms: D002675:Child, Preschool; D004352:Drug Resistance, Microbial / Q000235:genetics; D018432:Drug Resistance, Multiple / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D008800:Mexico / Q000453:epidemiology; D008826:Microbial Sensitivity Tests; D012703:Serotyping; D013290:Streptococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D013296:Streptococcus pneumoniae / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*