Dos aislamientos de Salmonella Infantis multirresistentes se comportan como hipoinvasivos pero con elevada proliferación intracelular

En este trabajo se investigó la presencia de determinantes característicos de plásmidos de virulencia en dos aislamientos clínicos de Salmonella Infantis portadores de plásmidos de multirresistencia. Además, se estudió la capacidad de invasión y proliferación en células eucariotas no fagocíticas. Ninguno de los aislamientos de S. Infantis mostró los determinantes genéticos que caracterizan a los plásmidos de virulencia para este género (operón spv). Los ensayos de invasión sobre líneas celulares eucariotas mostraron que los aislamientos de S. Infantis presentan una capacidad de invasión disminuida pero persisten y proliferan en el citoplasma, independientemente de utilizar una línea celular permisiva (HeLa) o no permisiva (NRK) para tal fin. Finalmente, no se observaron indicios microscópicos que podrían hacer sospechar un efecto bactericida de estas líneas celulares sobre los aislamientos estudiados.

Two multidrug-resistant Salmonella Infantis isolates behave like hypo-invasive strains but have high intracellular proliferation. In this work, plasmid-encoded virulence factors in two Salmonella Infantis isolates carrying multiresistance plasmids were investigated. In addition, their invasion and proliferative ability in non-phagocytic cells was studied. None of them showed the typical determinants of virulence plasmids (spv operon). The invasion assays of S. Infantis isolates on eukaryotic cells showed a decreased ability to Invade but they remained and proliferated In the cytoplasm regardless of having used a permissive (HeLa) or non-permissive (NRK) cell line. Finally, there was no microscopic evidence suggesting a bactericidal effect of these eukaryotic cell lines on the Isolates tested.

Prevalence of R-type ACSSuT in strains of Salmonella serovar Typhimurium DT193 isolated from human infections in Brazil / Prevalencia de resistencia de tipo ACSSuT en cepas de Salmonella serovariedad Typhimurium DT193 aisladas a partir de infecciones humanas en el Brasil

OBJECTIVE: To determine the prevalence of resistance to ampicillin, chloramphenicol, streptomycin, sulphonamides, and tetracyclines (ACSSuT) in Salmonella serovar Typhimurium definitive [phage] type (DT) 193 strains isolated from human sources over the last four decades. METHODS: From 2008 to 2010, 553 DT193 isolates out of 810 human-origin Salmonella ser. Typhimurium phage-typed strains isolated from the 1970s through 2008 were selected and tested for ACSSuT resistance: 91 strains isolated during the 1970s, 65 from the 1980s, 70 from the 1990s, and 327 from 2000-2008. Resistance profiles were determined using the disk diffusion method. RESULTS: †An antimicrobial susceptibility assay indicated 20.9 percent, or 116, of all isolates tested were ACSSuT-resistant, 52.0 percent (287) were resistant to one or more drugs in the ACSSuT profile, and 27.1 percent (150) were nonresistant (susceptible to antimicrobials). Based on the assay, overall antimicrobial resistance was extremely high in the 1970s (affecting 99.0 percent of isolates from that period) and remained high during the 1980s, when 95.4 percent of isolates had some type of antimicrobial resistance and incidence of Salmonella ser. Typhimurium DT193 R-type ACSSuT increased to 73.8 percent. R-type ACSSuT dropped to 27.1 percent (19 isolates) during the 1990s, and to 5.2 percent (17) during 2000-2008, despite a substantial increase in the number of isolates tested (397 versus 204, 111, and 98, respectively, for the previous three decades). CONCLUSIONS: †Although prevalence of Salmonella ser. Typhimurium DT193 R-type ACSSuT in Brazil has decreased since the 1970s, ACSSuT resistance markers continue to circulate. Therefore, continuous surveillance should be conducted to evaluate the occurrence of Salmonella ser. Typhimurium DT193 and its antimicrobial resistance.

OBJETIVO: Determinar la prevalencia de resistencia a la ampicilina, el cloranfenicol, la estreptomicina, las sulfonamidas y las tetraciclinas (ACSSuT) en cepas de Salmonella serovariedad Typhimurium fagotipo definitivo (DT) 193 aisladas de fuentes de origen humano durante las cuatro últimas décadas. MÉTODOS: Entre el 2008 y el 2010 se seleccionaron 553 aislados de DT193 entre 810 cepas de Salmonella serovariedad Typhimurium fagotipificadas aisladas desde la década de 1970 hasta el 2008, y en ellos se analizó la resistencia a ACSSuT: se estudiaron 91 cepas aisladas durante la década de 1970, 65 aisladas durante la década de 1980, 70 aisladas durante la década de 1990, y 327 aisladas entre el 2000 y el 2008, respectivamente. Los perfiles de resistencia a los antibióticos se determinaron mediante el método de difusión en disco. RESULTADOS: El antibiograma indicó que 20,9 por ciento (116) de todos los aislados que se analizaron fueron resistentes a ACSSuT, 52,0 por ciento (287) fueron resistentes a uno o más antibióticos del grupo ACSSuT y 27,1 por ciento (150) no fueron resistentes (es decir, fueron sensibles a dichos antibióticos). Según el análisis, la resistencia general a los antibióticos fue muy alta en la década de 1970 (y comprendió a 99,0 por ciento de los aislados de ese período) y continuó siendo alta durante la década de 1980, cuando 95,4 por ciento de los aislados presentó algún tipo de resistencia a los antibióticos y la incidencia de Salmonella serovariedad Typhimurium DT193 con resistencia de tipo ACSSuT aumentó hasta 73,8 por ciento. La resistencia de tipo ACSSuT descendió a 27,1 por ciento (31 aislados) durante la década de 1990, y a 5,2 por ciento (17 aislados) entre el 2000 y el 2008, a pesar del aumento importante en el número de aislados que se evaluaron (397 frente a 204, 111 y 98 en las tres décadas anteriores, respectivamente). CONCLUSIONES: Aunque la prevalencia de Salmonella serovariedad Typhimurium DT193 con resistencia de tipo ACSSuT en el Brasil ha disminuido desde la década de 1970, los marcadores de resistencia a ACSSuT continúan en circulación. Por consiguiente, debe llevarse a cabo una vigilancia permanente para evaluar la aparición de infecciones por Salmonella serovariedad Typhimurium DT193 y su resistencia a los antibióticos.

Avaliação da suscetibilidade antimicrobiana e do perfil de macrorrestrição do DNA de isolados humanos de Salmonella serovar Typhimurium fagotipo 193, no período de 1970 a 2008 / Assessment of antimicrobial susceptibility and macrorestriction DNA of human isolates of Salmonella serovar typhimurium phage type 193 in the period 1970 to 2008

Para analisar cepas de Salmonella ser. Typhimurium isoladas de processos entéricos e extraintestinais humanos ocorridos no período de 1970 a 2008 de diferentes regiões do país foram selecionadas, com base nos registros contidos no banco de dados do Laboratório de Enterobactérias do IOC/FIOCRUZ, RJ, amostras do fagotipo prevalente 193, visando precipuamente o reconhecimento de clones epidêmicos. Foram selecionadas 553 cepas de Salmonella ser. Typhimurium fagotipo 193 representadas por 91, 65, 70 e 327 amostras referentes as décadas de 70, 80, 90 e ao período de 2000 a 2008, respectivamente. Na análise global da sensibilidade destas cepas, 52% apresentaram um ou mais marcadores de resistência a antibióticos incluídos no perfil ACSSuT. Este perfil de resistência completo foi verificado em 20,9% dos isolados, sendo os 21,9% restantes, sensíveis a todas as drogas testadas, especialmente no período de 2000 a 2008, representadas por 121 amostras (37,0%) em relação as 327 culturas dessa época. O maior percentual de resistência foi observado nas amostras da década de 70 (99%) sendo o perfil ACSSuT detectado em 35,2% dos isolados, ressaltando-se que todas as amostras foram isoladas de processos gastroentéricos ocorridos na cidade de São Paulo. Ao longo das quatro décadas de estudo, descreve-se um ponto de ruptura entre a prevalência de resistência e a suscetibilidade na transição entre as décadas de 80 e 90. Embora o número de isolados de Salmonalla ser. Typhimurium fagotipo 193 tenha aumentado no último período considerado, o percentual de mono e multirresistência aos antimicrobianos se situou em nível elevado (63,0%). A análise do polimorfismo obtido após macrorrestrição com a enzima Xbal revelou que cepas isoladas na década de 90 apresentaram elevado percentual de similaridade (>-85%) com cepas isoladas recentemente (período de 2000-2008), sendo agrupadas nos mesmos "subclusters". Por outro lado, as cepas da década de 70 inserem-se em "subclusters" independentes...

To analyze strains of Salmonella ser. Typhimurium isolated from human cases of enteric and extraintestinal occurred during the period 1970 to 2008 of different regions of Brazil were selected, based on records in the database from Enterobacteria Laboratory of IOC/FIOCRUZ, RJ, samples prevalent phage type 193 in order to recognition of epidemic clones. We selected 553 strains of Salmonella ser. Typhimurium phage type 193 represented by 91, 65, 70 and 327 samples concerning the 1970s, 1980s, 1990s and the period from 2000 to 2008, respectively. In a global analysis of the sensitivity of these strains, 52% had one or more antibiotic resistance markers included in the profile ACSSuT. This resistance profile was found complete in 20.9% of isolates and the remaining 21.9%, sensitive to all drugs tested, especially in the period 2000 to 2008, represented by 121 samples (37.0%) compared the 327 cultures of that time. The highest percentage of resistance was observed in the samples of the 70 (99%) being the profile ACSSuT detected in 35.2% of isolates, emphasizing that all strains were isolated from gastrointestinal processes occurring in São Paulo city. Over the four decades of study, we describe a breaking point between the prevalence of resistance and susceptibility in the transition between the 1980s and 1990s. Although the number of isolates of Salmonella ser. Typhimurium phage type 193 has increased in the last period, the percentage of mono-and-multidrug resistance to antimicrobial agents stood at high level (63.0%). The analysis of polymorphism obtained after macrorestriction with the enzyme Xbal showed that isolates in the 1990s showed a high percentage of similarity (>-85%) with strains isolated recently (2000-2008) and are grouped in the same subclusters. Moreover, the strains of the 1970s fall into subclusters independent, although the percentage of similarity between such subsclusters and the other is >- 70%, the same was observed for the strains...

Antibacterial & antiplasmid activities of Helicteres isora L.

Background & objectives: The multiple drug resistance (MDR) is a serious health problem and major challenge to the global drug discovery programmes. Most of the genetic determinants that confer resistance to antibiotics are located on R-plasmids in bacteria. The present investigation was undertaken to investigate the ability of organic extract of the fruits of Helicteres isora to cure R-plasmids from certain clinical isolates. Methods: Active fractions demonstrating antibacterial and antiplasmid activities were isolated from the acetone extracts of shade dried fruits of H. isora by bioassay guided fractionation. Minimal inhibitory concentration (MIC) of antibiotics and organic extracts was determined by agar dilution method. Plasmid curing activity of organic fractions was determined by evaluating the ability of bacterial colonies (pre treated with organic fraction for 18 h) to grow in the presence of antibiotics. The physical loss of plasmid DNA in the cured derivatives was further confirmed by agarose gel electrophoresis. Results: The active fraction did not inhibit the growth of either the clinical isolates or the strains harbouring reference plasmids even at a concentration of 400 μg/ml. However, the same fraction could cure plasmids from Enterococcus faecalis, Escherichia coli, Bacillus cereus and E. coli (RP4) at curing efficiencies of 14, 26, 22 and 2 per cent respectively. The active fraction mediated plasmid curing resulted in the subsequent loss of antibiotic resistance encoded in the plasmids as revealed by antibiotic resistance profile of cured strains. The physical loss of plasmid was also confirmed by agarose gel electrophoresis. Interpretation & conclusions: The active fraction of acetone extract of H. isora fruits cured R-plasmids from Gram-positive and Gram-negative clinical isolates as well as reference strains. Such plasmid loss reversed the multiple antibiotic resistance in cured derivatives making them sensitive to low concentrations of antibiotics. Acetone fractions of H. isora may be a source to develop antiplasmid agents of natural origin to contain the development and spread of plasmid borne multiple antibiotic resistance.

Tetracycline and oxytetracycline resistance determinants detected in Bacillus cereus strains isolated from honey samples / Detección de determinantes de resistencia a tetraciclina y oxitetraciclina en cepas de Bacillus cereus aisladas de muestras de miel

The aim of this study was to investigate the presence of tetracycline and oxytetracycline resistance determinants in Bacillus cereus strains isolated from honey samples. Of a total of 77 isolates analyzed, 30 (39%) exhibited resistance to tetracyclines according to the results of a disk diffusion method. Resistant strains (n=30) were screened by PCR for the presence of the resistant determinants tetK, tetL, tetM, tetO, tetW, otrA and otrB and their MIC values for tetracycline, oxytetracycline and minocycline were assessed. According to the PCR results, 23 isolates (77%) presented at least one tetracycline or oxytetracycline resistance determinant. The tetK genotype was present in 10 isolates while the tetL, tetM, and otrA genotypes were present in 3, 2, and 5 isolates, respectively. In addition, 2 isolates of the tetK plus tetM genotype, 1 of the tetK plus tetL genotype, and 1 of the tetK plus otrA genotype were found. All isolates were tetW, tetO and otrB negatives. On the other hand, 7 isolates (23%) showed a tetracycline-resistant and/or minocyclineresistant phenotype (MIC) but did not carry any of the tet or otr determinants investigated in this study. This research has shown that B. cereus isolates from honey samples contain a variety of tetracycline and oxytetracycline resistance genes, including the tetK and tetL determinants which encode for efflux proteins, and tetM and otrA, which encode for ribosomal protection proteins. These findings indicate that strains isolated from honeys could represent a reservoir for tetracycline resistance genes. To our knowledge, this is the first report of tetracycline-resistant and oxytetracyclineresistant B. cereus strains carrying the tetK determinant, and also the first report of oxytetracycline-resistant and tetracycline- resistant Bacillus species carrying the otrA determinant.

El objetivo del presente estudio ha sido investigar la presencia de diversos determinantes de resistencia a tetraciclina y oxitetraciclina en las poblaciones de Bacillus cereus presentes en la miel. De un total de 77 aislamientos evaluados, 30 (39%) resultaron resistentes a tetraciclina y/o minociclina de acuerdo con los resultados de las pruebas de difusión en disco. Dentro del grupo que presentó un fenotipo resistente, se investigó la presencia de los determinantes tetK, tetL, tetM, tetO, tetW, otrA y otrB por PCR y se determinaron los valores de CIM para tetraciclina, oxitetraciclina y minociclina. De acuerdo con los resultados obtenidos por PCR, 23 aislamientos (77%) presentaron al menos un determinante de resistencia a tetraciclina o a oxitetraciclina; el genotipo tetK se encontró en 10 de esos aislamientos, mientras que los genotipos tetL, tetM y otrA se hallaron en 3, 2 y 5 aislamientos, respectivamente. Ningún aislamiento presentó los genotipos tetW, tetO ni otrB. Adicionalmente, se encontraron los genotipos tetK plus tetM (2 aislamientos); tetK plus tetL (1 aislamiento) y tetK plus otrA (1 aislamiento). Por otra parte, 7 cepas (23%) resultaron resistentes a tetraciclina, oxitetraciclina y/o minociclina por CIM, pero no presentaban ninguno de los determinantes tet u otr estudiados. Estos resultados indican la existencia de un alto porcentaje de cepas de B. cereus aisladas de miel con genes de resistencia a tetraciclina y oxitetraciclina, incluyendo los determinantes tetK, tetL, tetM y otrA. Este estudio constituye el primer registro de la presencia del determinante tetK de resistencia a tetraciclina en B. cereus, como así también la presencia del determinante otrA dentro del género Bacillus.

SHV-type extended-spectrum beta-lactamase (ESBL) are encoded in related plasmids from enterobacteria clinical isolates from Mexico

OBJECTIVE: In this work we report the molecular characterization of beta-lactam antibiotics resistance conferred by genes contained in plasmids from enterobacteria producing extended-spectrum beta-lactamases (ESBL). MATERIAL AND METHODS: Fourteen enterobacterial clinical isolates selected from a group of strains obtained from seven different hospitals in Mexico during 1990-1992 and 1996-1998 were analyzed at the Bacterial Resistance Laboratory (National Institute Public Health, Cuernavaca). Molecular characterization included PFGE, IEF of beta-lactamases, bacterial conjugation, PCR amplification and DNA sequencing, plasmid extraction and restriction. RESULTS: Isolates were genetically unrelated. ESBL identified were SHV-2 (5/14) and SHV-5 (9/14) type. Cephalosporin-resistance was transferable in 9 of 14 (64 percent) clinical isolates with only one conjugative plasmid, DNA finger printing showed a similar band pattern in plasmids. CONCLUSIONS: The dissemination of cephalosporin resistance was due to related plasmids carrying the ESBL genes.

OBJETIVO: En este trabajo se reporta la caracterización molecular de la resistencia a antibiótico beta-lactámicos conferida por genes contenidos en plásmidos de enterobacterias productoras de beta-lactamasas de espectro extendido (BLEEs). MATERIAL Y MÉTODOS: Catorce aislamientos clínicos de enterobacterias fueron seleccionados por conveniencia de un banco de cepas obtenidas de siete diferentes hospitales de México durante los periodos 1990-1992 y 1996-1998 y fueron procesados en el Laboratorio de Resistencia Bacteriana (Instituto Nacional de Salud Pública, Cuernavaca). En la caracterización se empleó PFGE, IEF para beta-lactamasas, conjugación bacteriana, amplificación por PCR y secuenciación de DNA, extracción y restricción de plásmidos. RESULTADOS: Las 14 cepas fueron no relacionadas genéticamente. Se identificaron BLEEs tipo SHV-2 (5/14) y SHV-5 (9/14). La resistencia a cefalosporinas fue transferida por conjugación en 9 de 14 (64 por ciento) aislamientos clínicos mediante un plásmido que mostró un patrón de restricción similar entre ellos. CONCLUSIÓN: Se sugiere que la diseminación de la resistencia a cefalosporinas fue debida a plásmidos relacionados que contienen los genes que codifican BLEEs.

Intraspecies transfer of a chloramphenicol-resistance plasmid of staphylococcal origin.

BACKGROUND & OBJECTIVES: The emergence of antibiotic-resistant bacteria is a phenomenon of concern to the clinician as well as to the pharmaceutical industry, because it is the major cause of failure in the treatment of infectious diseases. The genetic exchange of plasmids containing antibiotic resistant determinants (R-plasmids) between organisms of the same or different species is believed to play a crucial role in the evolution of antibiotic resistant bacteria. Staphylococcus aureus is well known for its multi-drug resistance (MDR). This work was undertaken to study the intraspecies transfer of a chloramphenicol (C) resistance staphylococcal R-plasmid among different clinical isolates of S. aureus. METHODS: From a MDR S. aureus MC524 strain, a small plasmid pMC524/MBM was isolated. Lysostaphin lysis and sucrose mediated detergent lysis were used for plasmid preparation. Agarose gel electrophoresis, transformation experiments, Southern blotting and hybridization were done. Restriction endonuclease (RE) digestions were performed. RESULTS: pMC524/MBM, which codes for C resistance could be transferred into some C sensitive clinical strains of S. aureus. The size and the RE digestion patterns of the plasmids isolated from the S. aureus transformants were identical to those of pMC524/MBM. INTERPRETATION & CONCLUSION: These results suggest that pMC524/MBM, without any modification is capable of transferring, maintaining, replicating and expressing itself in different clinical strains of S. aureus and hence may be responsible for the spread of C resistance.

High frequency of auxotrophy in clinical isolates of Proteus mirabilis harboring an R plasmid

We report a novel phenomenon of high genetic instability, related to auxotrophy, in strains of Proteus mirabilis. Among P. mirabilis strains harboring the R plasmid Kept in our laboratory collection, and some freshly isolated strians from clinical material, 54 per cent of the samples presented auxotrophy at frequencies higher than 10(-3). Prototrophic closes gave rise to auxotrophic ones at frequencies not explainable by the usual mutation mechanisms. The instability mainly affected the carbamoyl phosphate synthetase gene (car), which leads to a double requirement for arginine and uracil for growth in minimal medium. Other genes were also affected, at a lower frequency. The car mutation does not revert to prototrophy. A similar phenomenon of instability was induced in Escherichia coli strain HB 101 upon introduction of a drug-resistance plasmid from P. mirabilis. We have ruled out the hypothesis of a transposon in the generation of auxotrophy.

Multiple drug resistance and genetic characterization of Salmonella typhimurium isolated at Chandigarh.

A total of 1072 strains of S. typhimurium were isolated in Chandigarh during 1985-1988. Genetic characterization of 'R' plasmids was attempted in 21 multiple drug resistant strains (ACKSSu TT p-19, ACKSSu, TP-I, AKSSu Tp-1). All the 21 strains were sensitive to gentamicin, furoxone and nalidixic acid. Level of resistance to different antimicrobial drugs varied from 200 to 1000 mg/L. Majority of the strains were untypable by the present set of 31 typing phages (Ut-17, Phage type 21-2, Phase type 99-2). All the plasmids belonged to class I transfer system. All the plasmids restricted some or all the typing phages of S. typhimurium and 39 also restricted phage phi 2. These plasmids belonged to F1me or I1 incompatibility groups and did not inhibit the function of fertility factor (fi-).

Dissemination of plasmid-mediated amikacin resistance among pathogenic Klebsiella pneumoniae

Se analizó el contenido plasmídico de una serie de cepas de Klebsiella pneumoniae resistentes a amikacina y otros antibióticos. Estas cepas se identificaron como causantes de epidemias intrahospitalares en unidades pediátricas situadas en distintas localidades geográficas de Argentina. En todos los casos se encontraron plásmidos que poseían determinantes genéticos para resistencia a amikacina. Mediante análisis realizados con cortes con enzimas de restricción e hibridizaciones se determinó la presencia de elementos transponibles relacionados a Tn 1331 en todos las cepas estudiadas. Estos resultados indican que la transposición de estos elementos ha jugado un papel importante en el proceso de diseminación de la resistencia a la amikacina en el género Klebsiella (y probablemente en otras bacterias gram negativas) en Argentina

A review of protease secretion instability in Proteus mirabilis

Proteus mirabilis secreta uma única protease que é uma metalo-enzima alcalina. Descrevemos aqui alguns fatores fisiológicos que afetam a secreçäo de protease em clones isolados. Mais de cem diferentes isolados clínicos foram examinados quanto a capacidade de secretar protease. Verificou-se que algumas linhagens herdam o determinante de protease como um caráter estável (säo denominadas linhagens estáveis); outras linhagens exigem um fenótipo muito instável (denominadas linhagens instáveis) com 10% das colônias-filhas perdendo o caráter de produçäo de protease. Nunca foi observada a reversäo do fenótipo protease negativa. Por outro lado, a introduçäo de fatores R em células produtoras de protease reduziu a atividade proteásica em cerca de 50%, o que sugere uma interferência na expressäo e/ou secreçäo de protease. Embora haja evidências de que um locus da protease tenha localizaçäo extracromossômica, näo foi demosntrada a presença de plasmídios nas linhagens instáveis. Um modo que pode explicar os vários dados é apresentado

Análise genética de Salmonella typhimurium fermentadoras de lactose isoladas no Rio de Janeiro / Genetic analysis of lactose fermenting Salmonella typhimurum isolated in Rio de Janeiro

Salmonella typhimurium fermentadoras de lactose säo comuns em Säo Paulo, porém, raras no Rio de Janeiro, onde descrevemos dois isolamentos. Um plasmídeo de 7,4 megadáltons, näo auto-ransferível, termorresistente e näo eliminável pelo alaranjado de acridina foi identificado em cada uma das duas linhagens isoladas no Rio de Janeiro. O fato de uma dessas linhagens ser derivada de um plasmídeo que originalmente näo expressa o caráter fermentaçäo de lactose, permite-nos especular acerca da origem deste caráter nas Salmonellas brasileiras

Isolation, survival & transfer of R-plasmid of Salmonella typhimurium in Dal Lake of Kashmir (India).

Six strains of S. typhimurium were isolated from water samples of Dal Lake, Srinagar (India). These strains could survive and multiply in the Lake water and its filtrate. Viable count of this bacterium increased abruptly on 6th day of incubation with a peak level on 7th and 9th day, followed by sharp decline on 12th-14th day. Viable count was higher at 37 degrees C than at room temperature. At 4 degrees C this bacterium survived for longer time than at 22 degrees C or 37 degrees C. Viable count was higher and survival longer in the filtrate than in Lake water. Drug resistance could be transferred to Escherichia coli recipient strains from S. typhimurium, both in filtrate and Dal Lake water at 4 degrees C, 22 degrees C and 37 degrees C. The prolonged survival of pathogenic bacteria and transfer of R-plasmid in Dal Lake water could be a health hazard.

Coleformes fecais em águas de esgoto: II- transferência de marcadores e presença de plasmidial / Fecal coliforms in sewage treatment: II. Genetic tranfer and plasmids

Investigou-se a transferência de marcadores genéticos e a presença de DNA plasmidial em 240 culturas de Escherichia coli originárias de água de esgoto (afluente e fluentes) da Estaçäo de Tratamento da Ilha do Governador, na cidade do Rio de Janeiro, RJ. Experimentos de conjugaçäo com E. coli K 12 permitiram o isolamento de transconjugantes com resistência a antibióticos (Su, Sm, Tc, Cm e Ap); a metais pesados (Cu, Hg e Zn) e fatores colicinogênicos (Col Ia, Ib e V) principalmente para os coliformes isolados nos setores terminais da estaçäo de tratamento. A distribuiçäo de plasmídeos foi prevalente nas culturas de E. coli advindas dos efluentes, com percentuais superiores a 65