The facilitated influx of moxifloxacin through the most abundant channel in the outer cell wall of gram-negative bacteria was investigated. Molecular modeling provided atomic details of the interaction with the channel surface, revealed the preferred orientation of the antibiotic along its pathway, and gave an estimated time necessary for translocation. High-resolution conductance measurements on single OmpF trimers allowed the passages of individual moxifloxacin molecules to be counted. The average mean residence time of 50 micros is in agreement with the predicted strong interaction from the modeling. In contrast, control measurements with nalidixic acid, a hydrophobic antibiotic that rather permeates across the lipid membrane, revealed a negligible interaction. The spectral overlap of tryptophan with moxifloxacin was suitable for a FRET study of the protein-antibiotic interaction. Combining molecular dynamics simulations with selective quenching identified an interaction of moxifloxacin with Trp61 inside the OmpF channel, whereas nalidixic acid showed preferential interaction with Trp214 on the channel exterior. An understanding of the detailed molecular interactions between the antibiotic and its preferred channel may be used to develop new antibiotics with improved uptake kinetics.

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; Nilton Lincopan 4Relatos mundiais têm documentado a problemática da endemicidade de isolados clínicos de Pseudomonas aeruginosa multirresistente (MDR) aliada a elevados índices de morbidade/mortalidade. No Brasil, surtos de infecção ocasionados por P. aeruginosa têm sido relacionados com uma disseminação clonal da espécie. Atualmente, as opções terapêuticas para o tratamento das infecções causadas por esse microrganismo são limitadas, muitas vezes restringindo-se ao uso de carbapenêmicos (p. ex., imipenem [IPM]). Assim, a resistência ao IPM é uma questão de saúde pública, uma vez que esse antibiótico é empregado como último recurso no tratamento de infecções de origem hospitalar, causadas por bactérias Gram-negativas multirresistentes. No Brasil, os principais mecanismos relacionados com fenótipos multirresistentes de P. aeruginosa são produção de metalobetalactamase (MBL) do tipo SPM-1, presença de metilase 16S rRNA RmtD, perda de porina OprD e superexpressão de bombas de efluxo, o que pode explicar os altos índices de resistência a carbapenêmicos e aminoglicosídeos. A emergência de cepas com essas características é preocupante, tendo em vista a escassez de terapias efetivas no tratamento de infecções por esse patógeno. Finalmente, com base em relatos nacionais, publicados por diferentes grupos de pesquisa, podemos deduzir que a convergência de múltiplos mecanismos de resistência em P. aeruginosa tem sido um evento favorável para a seleção de diferentes clones endêmicos multirresistentes disseminados no Brasil.

The parotoid macroglands of toads (bufonids) and leaf frogs (hylids) are used in passive defence against predators. The parotoids release poison when the amphibian is bitten by a predator. Despite the apparent similarity, the anatomical and histological structure of these macroglands in hylids is poorly studied when compared with those of bufonids. In this paper, we focused on the morphology of the macroglands of P. distincta, a leaf frog endemic to the Brazilian Atlantic rainforest, comparing their structure with those of bufonids. In addition, we compared the macrogland morphology of P. distincta with those from major clades of Phyllomedusa. All results revealed a macrogland morphology in leaf frogs distinct from that of toads, suggesting that the term parotoid should be used only for those of bufonids.

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We read with great interest C. S. Antonio et al.'s letter describing the high prevalence of Acinetobacter baumannii carrying bla in Brazilian hospitals (1). Recently, we carried out a similar study, and although the bla OXA-143 gene was identified, its frequency was lower than that reported by Antonio et al. (1).During 2008, a total of 803 Gram-negative bacillus isolates, 1 isolate per patient, were collected from 17 private hospitals located in eight cities from four distinct geographic Brazilian regions. Among them, 91 (11.3%) were A. baumannii isolates that were recovered mainly from the respiratory tract (70.3%) and bloodstream (24.2%). Susceptibility testing was performed by CLSI broth microdilution (3). The detection of metallo-␤-lactamase (M␤L)-and carbapenem-hydrolyzing class D ␤-lactamase (CHDL)-encoding genes was performed by multiplex PCR (5, 7, 9) and confirmed by sequencing. The presence of the insertion sequence ISAba1 upstream of the CHDL-encoding genes was also investigated. Genetic relatedness among CHDL-producing A. baumannii isolates, including the first OXA-23-producing A. baumannii clone isolated in Brazil (4), was evaluated by pulsed-field gel electrophoresis (PFGE).A total of 83/91 (91.2%) isolates were resistant to carbapenems. We also observed low rates of susceptibility to amikacin (18.7%), ceftazidime (12.1%), cefepime (8.8%), piperacillin-tazobactam (3.3%), and ciprofloxacin (3.3%). In contrast, most A. baumannii isolates were susceptible to polymyxin B (MIC 90 , 1 g/ml; 97.8% of the isolates were susceptible).M␤L-encoding genes were not identified in our study, as was also reported by Antonio et al. (1). However, we identified the bla OXA-23 gene in carbapenem-resistant isolates more frequently than in the former study (83.5% versus 41.7%). The bla OXA-23 gene was found in all carbapenem-resistant isolates from the cities of Belo Horizonte, Blumenau, Curitiba, and São Luís, followed by Rio de Janeiro (93.7%), Porto Alegre (80.0%), and São Paulo (69.0%). These results are in accordance with previous local reports (2, 4, 6) that emphasize that this gene is widespread in our country. The ISAba1 element was positioned upstream of bla in all isolates, whereas no insertion sequence was observed upstream of bla . Although A. baumannii carrying bla OXA-58 and bla OXA-72 had recently been described in Brazil (1,8), no isolates carrying these variants were found in our study.Nine distinct PFGE clones were identified among the 76 OXA-23-producing A. baumannii isolates. The predominance of a single clone (clone A [36.8% of the isolates]) was observed in isolates collected from six distinct Brazilian cities. This clone exhibited a PFGE profile similar to that of the first Brazilian clone producer of OXA-23 (4). A. baumannii belonging to clones B (17.1%) and D (9.2%) were also identified in isolates collected from distinct cities, while other genotypes were identified in specific locations.While

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Emergence of carbapenem-resistant Escherichia coli producing CMY-2-type AmpC b-lactamase in Brazil Carbapenem-resistant Escherichia coli isolates have not been described to date in South America. However, the emergence of Shigella flexneri and Klebsiella pneumoniae isolates producing CMY-2type plasmid-mediated AmpC was recently reported in Argentina (Radice et al., 2007; Rapoport et al., 2008). Here, we report the emergence of carbapenemresistant E. coli producing CMY-2-type AmpC b-lactamase in Brazil, confirming that CMY-2-producing strains have already become established in Latin America.