Abstract

Proteus mirabilis is an opportunistic pathogen resistant to multiple antibiotics, known to cause urinary tract infections and to form biofilms on catheters. Although pathogenicity and biofilm formation mechanisms in clinical strains have been studied, there is little information on environmental isolates that may be potential pathogens and reservoirs of virulence genes. For the first time, this work evaluated the elongated cell morphology of P. mirabilis in cultures of an environmental strain isolated from oyster tissue, as well as in biofilms formed in vitro on chitin surfaces, using transmission electron microscopy and environmental scanning electron microscopy, respectively. A similar evaluation was also performed on a clinical reference strain used as a control for the study. These microscopy techniques show cell elongation in environmental P. mirabilis and the presence of virulence factors such as fimbriae, flagella, and pili. These findings suggest that the elongated morphology in this bacterial species may be a strategy of survival and resistance to adverse conditions, as well as a mechanism of pathogenicity that allows the bacterium to colonize the upper areas of the urinary tract with the formation of biofilms. Our results contribute to the knowledge of the survival, virulence, and pathogenicity mechanisms of clinical and environmental strains of P. mirabilis, whose importance is constantly growing in public health.