Se comprueba que en las enteritis de los cerdos de la Provincia de Buenos Aires actúan indistintamente microorganismos solos o asociados. De 172 muestras bacteriológicas de necropsias y casos clínicos de enteritis de cerdos se aislaron: Escherichia coli 139; Salmonella 15; Proteus 10; Klebsiella 21; Sighella 2; Serratia 1; Pseudomonas 1; Campylobacter 28; Treponema 29 y Clostridum perfrigens 2. De las 139 cepas de E.coli un alto porcentaje correspondieron a los tipos somáticos 0149,0141,0138, y 08. Con los tipos somáticos 09,0141 y 04-0123 se reproduce experimentalmente la enfermedad de los edemas. Se detecta una elevada resistencia a las drogas con las cepas de E. coli aisladas en diferentes desórdenes entéricos, especialmente con los antibióticos de uso común en terapéutica veterinaria de nuestro país. Los serotipos más frecuentes de Salmonellas aisladas corresponden a S.cholera suis y S.tiphymurium. Treponema sp. y Campylobacter son los agentes bacterianos más comunmente aislados en la Disentería porcina. Se aisla C.perfrigens en 2 casos de enteritis necrótica. / The present work proved that pig enteritis in de province of Buenos Aires are caused by several kinds of microorganism that can act alone or associated in the gut. In a survey of 172 bacteriological samples taken from necropsied pigs with clinical sing of diarrhoea the following bacterias were isolated: E. coli 139;Salmonella 15;Proteus 10;Klebsiella 21;Sighella 2;Serratia 1;Pseudomonas 1;Campylobacter 28;Treponema 29 y Clostridium perfrigens 2. From the 139 strains de E.coli a high rate belonged to the somatic types 0149,0141,0138 y 08. With the somatic types of E.coli 09,0141 y 04-0123 the experimental reproduction of the Odenema disease was done. The strains of E.coli isolated from enteric disease showed high resistence specialy to the antibiotics of common use in the veterinary practice in Argentina. Within the Salmonella group.S.cholera suis and S.tiphimurium were the serotype isolated more frecuently. From pigs with pathological diagnosis of Swine Disentery,Traeponema and Campylobacter sp were isolated and from two cases of Necrotic a Clostridium perfrigens was recovery.

A wastewater treatment and reuse system consisting of a tile drainage system, a constructed treatment wetland (CTW), a reservoir, and an irrigation system was established. The system supplied 780 mm of irrigation water for the 1.8 ha of drained land for the 2008 growing season. A hydraulic tracer study conducted in the CTW supported the use of a length to width ratio of 10:1. During 2008, annual nitrate-nitrogen (NO3--N) and Escherichia coli (E. coli) mass reductions were 67.6 and 63.3%, respectively. Elevated E. coli levels were observed in the reservoir during the warm season. Therefore, water may not be safe for irrigating crops consumed raw. The mean first-order areal uptake rate constants generated for NO3--N and E. coli were 8.0 and 6.4 m y-1, respectively, and are recommended for similar CTWs. A wetland area to drainage area ratio of 4.5% is recommended to achieve ? 70 % mass reduction of NO3--N and E. coli

In a series of field and watershed scale studies, the genetic diversity of Escherichia coli in secondary habitats (e.g. soils and sediments) of an agricultural watershed was assessed in order to examine the dynamics of E. coli inhabiting these matrices and to determine their contribution to waterborne populations. Using replicated field plots, persistent subpopulations of E. coli were observed to be significantly affected by hillslope position due to inherent differences in soil texture and moisture content. The dynamics of E. coli populating tile drainage effluent in a working cultivated field were monitored and it was observed that putatively naturalized E. coli dominated the effluent after approximately 55 days following manure amendments. The contribution of tile drainage effluents to the waterborne E. coli population in an adjacent stream was exponentially related to tile discharge rates, regardless of whether the effluent was populated by manure-associated or naturalized E. coli strains. Streambed E. coli populations differed according to stream geomorphological features, with strains responding to sediment texture and water velocity distributions among the features. In a temporal study of sediment E. coli, population turnover was observed to be affected by sediment redistribution in highenergy stream reaches and was stabilized by immigration from adjacent catchment sources in low-energy stream reaches. Reach-specific connectivity between sediment and waterborne E. coli populations was observed in this watershed. Reach- and catchmentscale hyporheic processes are speculated to be occurring, which may be in part influenced by strain-dependent attachment behaviour of E. coli strains in disjoint stream reaches influenced by different catchment sources of E. coli. The attachment of waterborne E. coli to suspended particles was observed to be associated with land use, water quality and suspended particle variables. The relationship of land use type to particle attachment reinforces the hypothesis that strain-specificity in attachment behaviour can affect the transport of E. coli in fluvial systems. This work provides evidence that putatively naturalized strains in cultivated fields can contribute a large part to waterborne E. coli, and that reach-specific hydrological factors need to be considered when relating sediment- to waterborne E. coli in fluvial systems.

No description available.

No description available.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

A method for transformation of Geobacillus debilis by conjugation was developed using a recombinant plasmid, pNW33N-pxyl-bs2-mob, derived from pNW33N. The plasmid includes the mob region of RP4 for mobilization, is mobilized from E. coli S17-1 to G. debilis, and can stably propagate in G. debilis trans-conjugants grown at 50 oC and 55 oC, in the presence of thiamphenicol. Successful conjugation was depended on the cell density and viability of G. debilis when harvested for conjugation, as well as the metabolic activity of E. coli S17-1 used for conjugation. Substantial reduction in size of the plasmid DNA was observed when G. debilis transconjugants were cultured at 60 oC in the presence of thiamphenicol, and uniform rearrangement of the plasmid DNA was observed after culturing G. debilis transconjugants in the presence of spectinomycin, even at 50 oC.

This thesis assessed the prevalence, patterns of antibiotic resistance, and molecular characteristics of ESBL-, AmpC-, and carbapenemase-producing Escherichia coli (EC) and Klebsiella pneumoniae (KPN) isolated from Canadian hospitals. Bacterial isolates were collected as part of the CANWARD national surveillance study. The prevalence of ESBL-EC [2007: 3.4%, 2012: 7.6%], AmpC-EC [2007: 0.7%, 2012: 2.2%], and ESBL-KPN [2007: 1.5%, 2012: 3.6%] increased between 2007 and 2012. Antimicrobials demonstrating the greatest activity against isolates in this study were colistin, amikacin, ertapenem, and meropenem, while 78.8%, 34.9%, and 66.7% of ESBL-EC, AmpC-EC, and ESBL-KPN, respectively, were multidrug resistant. Isolates were generally unrelated by PFGE; however, ST-131 was identified among 56.9% and 31.7% of ESBL-EC and AmpC-EC, respectively. CTX-M-15 was the dominant genotype in ESBL-EC (66.5%) and ESBL-KPN (48.1%), while the dominant genotype in AmpC-EC was CMY-2 (53.2%). Carbapenemase production was identified in 0.03% of EC and 0.05% of KPN, all of which produced KPC-3.

The spread of resistance to the cephalosporins in the Enterobacteriaceae and more specifically within E. coli is a continuing cause of public health concern, with such resistance increasingly seen in community- and nosocomial-acquired infections. Extended-spectrum ß-lactamase (ESBL) and AmpC ß-lactamase (AmpC) enzymes cause most cephalosporin resistance in E. coli by hydrolysis of the antimicrobial and continue to jeopardize patient outcome. The purpose of this thesis was to determine the prevalence of ESBL-producing Enterobacteriaceae and to molecularly characterize ESBL and AmpC producers found to be associated with the increasing cephalosporin resistance among E. coli within Canadian hospitals from 2005 to 2009. Isolates were collected as part of the Canadian Intensive Care Unit and Canadian Ward surveillance studies. ESBL and AmpC producers were molecularly characterized for resistance genes, virulence factors and phylogenetic groups. All strains were typed using PFGE and ESBL-producing E. coli were further typed by MLST. Plasmids bearing the ESBL and AmpC genes were characterized by BglII RFLP analysis and a multiplex PCR for replicon typing. ESBL-producing E. coli and K. pneumoniae and AmpC-producing E. coli were found to be firmly established in Canadian hospitals; whereas, ESBL-producing K. oxytoca and P. mirabilis have yet to emerge. Increasing resistance to several unrelated antimicrobials leading to multi-drug resistance among these pathogens is concerning. The successful dissemination of ESBL-producing E. coli in Canada occurs through a diversity of different mechanisms and does not correspond to a single ESBL determinant, or a single clone, or a single plasmid but rather through the combination of clonal spread of virulent strains and the acquisition of diverse ESBL-bearing plasmids. However, the predominance of CTX-M-15-producing E. coli in this study was mainly due to the virulent ST131 clone and the diverse IncFII plasmids bearing the blaCTX-M-15 gene. Whereas, horizontal transfer of genetically similar IncI1, IncA/C and IncK/B plasmids bearing blaCMY-2 and the clonal spread of virulent strains, including ST131 with ampC promoter/attenuator mutations, appears to be playing a role in the spread of AmpC-producing E. coli isolates in Canadian hospitals. The increasing prevalence of these multi-drug resistant pathogens in Canadian hospitals demonstrates the need for increased surveillance and understanding of these emerging pathogens. The continued surveillance will help guide proper infection control procedures and identify optimal treatment of these clinically important pathogens in Canadian hospitals.

No description available.