The ability of three quinolones, two I-lactams, and one aminoglycoside to select resistant mutants was examined in tests with 30 isolates of commonly encountered nosocomial pathogens. Ciprofloxacin and norfloxacin, two new quinolone derivatives, were no more likely to select resistant mutants than amikacin, whereas nalidixic acid, an older quinolone derivative, was the most likely of the six drugs examined to select resistant mutants. Mutational frequencies of 10-7 to 10-8 were observed in most instances. In general, the mutants were 8 to 16 times less susceptible to the drug used for selection. Although most quinolone-selected mutants were cross-resistant only to other drugs within this class, certain mutants of Klebsiella pneumoniae selected by nalidixic acid, ciprofloxacin, or norfloxacin were also less susceptible to 13-lactam antibiotics. This unusual pattern of multiple drug resistance was associated with changes in outer membrane proteins of the organism. Multiple drug resistance was also observed in P-lactam-selected mutants of Enterobacter cloacae and Pseudomonas aeruginosa (,-lactams), amikacin-selected mutants of Providencia stuartii and P. aeruginosa (aminoglycosides), and I-lactam-or amikacin-selected mutants of Serratia marcescens (B-lactams plus aminoglycosides). These results underscore the need to examine carefully the frequency with which resistance to any new antibiotic develops, as well as the patterns of multiple drug resistance which may occur simultaneously.The development of resistance can significantly shorten the useful lifetime of antimicrobial agents in prophylaxis and therapy of infectious diseases and has been a major problem with nalidixic acid, a quinolone derivative, and possibly with the new cephalosporins (23, 26). Unfortunately, potential problems with the development of resistance are often not thoroughly analyzed for most antibiotics before the time the drugs become available for clinical use. The occurrence of cross-resistance to related or unrelated antibiotics is also seldom studied in depth.The recent development of new quinolone derivatives, such as norfloxacin and ciprofloxacin, has stimulated interest in these problems of resistance. New members of this class of compounds must be analyzed closely to determine whether resistance will develop as frequently as it has with nalidixic acid. Several studies have already examined this aspect (4,5,8,13,15,17,29 MIC (usually 4,8,and 16 times the MIC). The actual inoculum utilized was determined by agar dilution plate counts. After overnight incubation at 35°C in air, the apparent mutational frequencies were calculated from results obtained with the highest drug concentration on which colonies were detected. Cells selected by this procedure were considered to be resistant mutants if the MIC for the drug utilized was increased at least eightfold. For most combinations, mutants occurring at a frequency as low as 10-9 could be detected.

The Cylindrospermopsis raciborskii population from Brazilian freshwater is known to produce saxitoxin derivatives (STX), while cylindrospermopsin (CYN), which is commonly detected in isolates from Australia and Asia continents, has thus far not been detected in South American strains. However, during the investigation for the presence of cyrA, cyrB, cyrC and cyrJ CYN synthetase genes in the genomes of four laboratory-cultured C. raciborskii Brazilian strains, the almost complete cyrA gene sequences were obtained for all strains, while cyrB and cyrC gene fragments were observed in two strains. These nucleotide sequences were translated into amino acids, and the predicted protein functions and domains confirmed their identity as CYN synthetase genes. Attempts to PCR amplify cyrJ gene fragments from the four strains were unsuccessful. Phylogenetic analysis grouped the nucleotide sequences together with their homologues found in known CYN synthetase clusters of C. raciborskii strains with high bootstrap support. In addition, fragments of sxtA, sxtB and sxtI genes involved in STX production were also obtained. Extensive LC-MS analyses were unable to detect CYN in the cultured strains, whereas the production of STX and its analogues was confirmed in CENA302, CENA305 and T3. To our knowledge, this is the first study reporting the presence of cyr genes in South American strains of C. raciborskii and the presence of sxt and cyr genes in a single C. raciborskii strain. This discovery suggests a shift in the type of cyanotoxin production over time of South American strains of C. raciborskii and contributes to the reconstruction of the evolutionary history and diversification of cyanobacterial toxins.

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An updated synthesis of cyanobacteria and algae information is presented for Brazil aiming to refine the data gathered to date and evaluate the progress of the biodiversity knowledge about these organisms in the country since the publication of the Catálogo de Plantas e Fungos do Brasil. The results of 2015 showed an increase of 1,250 species (35.7%) when compared to 2010, reaching a total of 4,747 species. The most diverse classes in species number were the Bacillariophyceae, Conjugatophyceae, Florideophyceae, Cyanophyceae, Dinophyceae and Euglenophyceae. Bacillariophyceae and Cyanophyceae had the highest increase in species number in the five-year interval. The Southeast and South regions were the most diverse, however, the Northeast, with the states of Piauí and Sergipe, and the Central-west region, with Mato Grosso, Goiás and Distrito Federal, also stood out in the national algal biodiversity scenario. Despite the shortage of taxonomists and limited infrastructure, the results showed a significant improvement in the knowledge regarding the diversity of cyanobacteria and algae in the country during the study period, starting to even out regional geographical differences caused by subsampling. Key words: Biodiversity, phycology. ResumoApresenta-se uma síntese atualizada de informações sobre algas no Brasil objetivando refinar os dados reunidos até o presente, bem como avaliar os avanços sobre o conhecimento da diversidade de algas no país desde a publicação do Catálogo de Plantas e Fungos do Brasil. Os resultados de 2015 mostraram um acréscimo de 1.250 espécies (35.7%) a um total de 4.747 em relação a 2010. As classes mais diversas em número de espécies foram Bacillariophyceae, Conjugatophyceae, Florideophyceae, Cyanophyceae, Dinophyceae e Euglenophyceae. Bacillariophyceae e Cyanophyceae tiveram o maior acréscimo de espécies no intervalo de cinco anos. A região Sudeste e Sul foram as mais diversas, porém, as regiões Nordeste com os estados do Piauí e Sergipe e Centro-Oeste com os estados de Mato Grosso, Goiás e Distrito Federal destacaram--se no cenário da biodiversidade nacional. Apesar da escassez de taxonomistas e da infraestrutura limitada, os resultados obtidos evidenciaram um avanço significativo no conhecimento da diversidade de algas no país nesse período de cinco anos, iniciando uma mudança quanto as diferenças geográficas regionais. Palavras-chave: Biodiversidade, ficologia.

The chromosomal I-lactamase and outer membrane proteins of Enterobacter cloacae were examined to determine their relative contributions to multiple antibiotic resistance in this organism. Mutants altered in I(-lactamase expression, whether derived in the laboratory or recovered from patients treated with one of the new ,-lactam antibiotics, were found to have no detectable alterations in outer membrane proteins. Derepression of ,I-lactamase in these mutants was associated with high-level resistance to multiple I-lactam antibiotics, while loss of inducible ,-lactamase (i.e., production of basal enzyme levels only) was associated with acquisition of susceptibility to many ,-lactam antibiotics, including cephalothin. In contrast, alteration in outer membrane proteins was associated with only moderate-leVel resistance to P-lactam antibiotics. However, this included resistance to such drugs as amdinocillin and Sch 34343, which were unaffected by derepression of P-lactalnase. Resistance to chloramphenicol and tetracycline also accompanied changes in outer membrane proteins. Although the outer membrane proteins of various strains of E. cloacae were similar, there did appear to be some major strain-to-strain variations. Thus, it appears that alterations in both 13-lactamase and outer membrane proteins can affect the susceptibility of E. cloacae to many antibiotics. However, alterations in P-lactamase alone are sufficient to produce high-level multiple 3-lactam resistance in this organism.Mutants of Enterobacter spp. producing high levels of P-lactamase have been shown to be responsible for a number of clinical failures associated with emergence of resistance during therapy with the newer expanded-spectrum ,-lactam antibiotics (16). These mutants occur spontaneously at a frequency of 10-6 to 10-7 and appear to have lost control of P-lactamase production (8, 10). Normally, production of the chromosomally mediated cephalosporinase of Enterobacter spp. is under repressor control (8). Loss of this normal control mechanism via mutation leads to high-level Ilactamase production. This event is associated with resistance to multiple P-lactam antibiotics (8, 10, 14, 16). This resistance has been difficult to explain solely on the basis of P-lactamase-mediated hydrolysis because it involves many drugs that appear to be poor substrates for the enzyme. Thus, it has been speculated that this resistance must also involve a change in permeability.The permeability of gram-negative organisms to ,B-lactam antibiotics is determined primarily by outer membrane proteins (13). Studies by Sawai et al. (17) and Kaneko et al. (9) indicate that in Enterobacter cloacae two major outer membrane proteins appear to be involved in cephalosporin permeation. Alterations in these proteins have been shown to be associated with multiple P-lactam resistance in this organism (17). Since changes in P-lactamase expression and outer membrane proteins can be responsible for multiple 13-lactam resistance, this investigation was designed to examine both these fact...

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Reports of cyanobacterial blooms developing worldwide have considerably increased, and, in most cases, the predominant toxins are microcystins. The present study reports a cyanobacterial bloom in Lake Violão, Torres, Rio Grande do Sul State, in January 2005. Samples collected on January 13, 2005, were submitted to taxonomical, toxicological, and chemical studies. The taxonomical analysis showed many different species of cyanobacteria, and that Microcystis protocystis and Sphaerocavum cf. brasiliense were dominant. Besides these, Microcystis panniformis, Anabaena oumiana, Cylindrospermopsis raciborskii, and Anabaenopsis elenkinii f. circularis were also present. The toxicity of the bloom was confirmed through intraperitoneal tests in mice, and chemical analyses of bloom extracts showed that the major substance was anabaenopeptin F, followed by anabaenopeptin B, microcystin-LR, and microcystin-RR.

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