title: [Treatment failure due to acquisition of antibiotic resistance: report of two clinical cases].
abstract: OBJECTIVE
  We describe two cases of treatment failure due to intra-treatment acquisition of antibiotic resistant microorganisms with the aim of highlighting the possible molecular mechanisms by which treatment failure occurred.
  
  
  METHODS
  We analyzed the clinical histories and the isolates obtained from 2 patients, one with a urinary tract infection (UTI) by E. coli, initially treated with cefuroxim (to which the isolate was susceptible), and another with osteoarthritis (OA) treated initially with meropenem plus vancomycin, developing K. pneumoniae susceptible to meropenem. During treatment, in both patients, resistant microorganisms were isolated, and empirical therapy was modified, initially with ceftriaxone and afterwards meropenem in case 1, and adding amikacin in case 2. Both strains (per patient) were compared by PFGE and resistance genes were sought by PCR.
  
  
  RESULTS
  Regarding the UTI, the initial strain acquired an IncFIB SHV-5-producing plasmid. In the OA case, the initial susceptible strain was substituted by a CTX-M-9 and AadB-AadA2-Aac(6')Ib-producing K. pneumoniae.
authors.affiliation: Instituto de Higiene, Departamento de Bacteriología y Virología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.
authors.forename: Luciana
authors.initials: L
authors.lastname: Robino
authors.forename: Nicolás
authors.initials: N
authors.lastname: Cordeiro
authors.forename: Virginia
authors.initials: V
authors.lastname: García-Fulgueiras
authors.forename: Inés
authors.initials: I
authors.lastname: Bado
authors.forename: Gabriela
authors.initials: G
authors.lastname: Algorta
authors.forename: Rafael
authors.initials: R
authors.lastname: Vignoli
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D002648:Child; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects*; D006801:Humans; D007231:Infant, Newborn; D007711:Klebsiella pneumoniae / Q000187:drug effects*; D008297:Male; D010003:Osteoarthritis / Q000188:drug therapy* / Q000382:microbiology; D017211:Treatment Failure; D014552:Urinary Tract Infections / Q000188:drug therapy* / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents