Potential effects between bacteriophages and antibiotics to inactivate Escherichia coli

• Autor(a) principal: Valério, Nádia Castanho
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/22360
• topic: Resistência a antibióticos; Bacteriófagos

Escherichia coli is part of the normal flora of the gastrointestinal tract of humans and various mammals. This opportunistic microorganism is capable of cause several infections, such as urinary tract infections (UTI). E. coli is resistant to a large number of antibiotics, becoming harder the control of infections caused by this bacterium. Phage therapy may be a useful tool to control infections caused by antibiotic resistant strains. However, the major concern of the phage therapy is also the emergence of phage resistant bacteria. In this study, was evaluated the combination of two different therapies, chemotherapy and phage therapy, to evaluate the possibility of synergic effects between them. It was used the phage ECA2 (a phage previously isolated by the research group) and various antibiotics (ampicillin, kanamycin, piperacillin, tetracycline, chloramphenicol and ciprofloxacin) with different mechanisms of action. The E. coli strain used in this study is sensitive to the antibiotics ciprofloxacin, tetracycline and chloramphenicol and resistant to the antibiotics ampicillin, kanamycin and piperacillin The phage ECA2 caused a reduction in E. coli concentration of ≈ 4.5 log after 2 hours of treatment in phosphate buffered saline (PBS). The results obtained with the mixtures of the phage with ampicillin, kanamycin and piperacillin did not cause significantly differences when compared with the results obtained just with the phage. As the bacterium E. coli showed resistance to those antibiotics, the bacterial inactivation was just due the action of the phage. Otherwise, the results obtained using the mixtures of ECA2 with tetracycline and chloramphenicol were worse than the results obtained just with the phage. The conjugation of the phage with ciprofloxacin resulted in a bacterial inactivation of about 8.3 log, compared to the ≈4.5 log of bacterial inactivation obtained with the phage alone. In addition, the conjugation of the phage ECA2 with ciprofloxacin resulted in a decrease of the bacterial resistances obtained the phage and the antibiotic individually. The efficacy of phage therapy in urine was also evaluated, with the phage and the mix of phage and ciprofloxacin. The inactivation of E. coli in urine samples was similar to that obtained in PBS. It was observed a decrease of 4.3 log after 4 hours of treatment. Furthermore, a cocktail with two phages, the phage ECA2 and another E. coli specific phage, previously isolated by the research group, the phage phT4A, was also tested. The E. coli inactivation was 3.5 log after 4 hours. The results indicate that phage and antibiotic combinations could result in synergistic effect in the inactivation of bacteria, but only when the bacterium is sensitive to the antibiotic. Also, the combination of antibiotics with phages contributes to managing resistance levels, controlling the antibiotic resistance and phage-resistant mutants. The phages limit the emergence of antibiotic resistant variants in combined treatments independently of antibiotic type, but the antibiotics limit the resistance of phage-mutants only when bacteria are sensitive to the antibiotic. However, overall, in the presence of antibiotics the resistance of phage-mutants was the same or less than when phages were tested alone. The high bacterial inactivation efficiency with phages combined with a higher bacterial inactivation in the presence of antibiotic and the long periods of phage survival in urine samples, paves the way for depth studies to control urinary tract infection and to overcome the development of resistances by E. coli, the bacterium most frequently isolated in UTI at the community level and at hospital settings