title: Hypermutable Pseudomonas aeruginosa in Cystic fibrosis patients from two Brazilian cities.
abstract: Hypermutable (HPM) strains of Pseudomonas aeruginosa have been found at high frequencies in cystic fibrosis (CF) patients in Europe. We report the results of testing for HPM frequencies, mutator genotype, and antimicrobial resistance of P. aeruginosa strains from Brazilian CF patients. A modified disk diffusion technique was used to quantify antibiotic-resistant subpopulations of an isolate, and estimations of the frequency of mutation to rifampin resistance were determined for 705 isolates from 149 patients attending clinics in two Brazilian cities. Mutations in the mutS gene were detected by sequencing assays. We found 194 (27.5%) HPM isolates in samples from 99 (66.4%) patients. Thirty-five HPM isolates (18.0%) from 31 (31.3%) patients exhibited a high increased spontaneous mutation rate compared with controls, and eight isolates from six patients displayed a defective mutS gene. The dominant HPM population was associated with very low antibiotic resistance levels, while HPM subpopulations were generally more resistant to antimicrobials. A relatively high prevalence of HPM P. aeruginosa in CF patients was associated with surprisingly low antibiotic resistance levels, in contrast to some earlier studies.
authors.affiliation: Unidade de Microbiologia, Serviço de Patologia Clínica, Hospital de Clínicas de Porto Alegre (HCPA), Ramiro Barcelos, Porto Alegre, RS, Brazil.
authors.forename: Larissa
authors.initials: L
authors.lastname: Lutz
authors.forename: Robson Souza
authors.initials: RS
authors.lastname: Leão
authors.forename: Alex Guerra
authors.initials: AG
authors.lastname: Ferreira
authors.forename: Dariane Castro
authors.initials: DC
authors.lastname: Pereira
authors.forename: Caroline
authors.initials: C
authors.lastname: Raupp
authors.forename: Tyrone
authors.initials: T
authors.lastname: Pitt
authors.forename: Elizabeth Andrade
authors.initials: EA
authors.lastname: Marques
authors.forename: Afonso Luis
authors.initials: AL
authors.lastname: Barth
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001938:Brazil; D002648:Child; D002675:Child, Preschool; D002947:Cities; D003550:Cystic Fibrosis / Q000150:complications*; D024881:Drug Resistance, Bacterial; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008826:Microbial Sensitivity Tests; D051719:MutS DNA Mismatch-Binding Protein / Q000235:genetics; D009154:Mutation; D059645:Mutation Rate; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification*; D017422:Sequence Analysis, DNA
chemical_list: D000900:Anti-Bacterial Agents; D051719:MutS DNA Mismatch-Binding Protein