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00925njm 22002777a 4500 dc Ferrandiz-Avellano, Maria-Jose author Ardanuy, Carmen author Liñares, Josefina author García-Arenzana, José María author Cercenado, Emilia author Fleites, Ana author de la Campa, Adela G author 2005-06 A total of 103 (0.7%) of 14,236 Streptococcus pneumoniae isolates collected in four Spanish hospitals from 1989 to 2003 were resistant to rifampin (MICs, 4 to 512 microg/ml). Only sixty-one (59.2%) of these isolates were available for molecular characterization. Resistance was mostly related to human immunodeficiency virus (HIV) infection in adult patients and to conjunctivitis in children. Thirty-six different pulsed-field gel electrophoresis patterns were identified among resistant isolates, five of which were related to international clones (Spain23F-1, Spain6B-2, Spain9V-3, Spain14-5, and clone C of serotype 19F), and accounted for 49.2% of resistant isolates. Single sense mutations at cluster N or I of the rpoB gene were found in 39 isolates, while double mutations, either at cluster I, at clusters I and II, or at clusters N and III, were found in 14 isolates. The involvement of the mutations in rifampin resistance was confirmed by genetic transformation. Single mutations at clusters N and I conferred MICs of 2 microg/ml and 4 to 32 microg/ml, respectively. Eight isolates showed high degrees of nucleotide sequence variations (2.3 to 10.8%) in rpoB, suggesting a recombinational origin for these isolates, for which viridans group streptococci are their potential gene donors. Although the majority of rifampin-resistant isolates were isolated from individual patients without temporal or geographical relationships, the clonal dissemination of rifampin-resistant isolates was observed among 12 HIV-infected patients in the two hospitals with higher rates of resistance. Antimicrob Agents Chemother. 2005 Jun;49(6):2237-45. 10.1128/AAC.49.6.2237-2245.2005 0066-4804 Antimicrobial agents and chemotherapy 15917517 http://hdl.handle.net/20.500.12105/8271 New mutations and horizontal transfer of rpoB among rifampin-resistant Streptococcus pneumoniae from four Spanish hospitals