Effects of Cefazolin and Meropenem in Eradication Biofilms of Clinical and Environmental Isolates of Proteus mirabilis

Proteus mirabilis is an opportunistic Gram-negative bacterium belonging to the family Enterobacteriaceae and is known for its ability to cause urinary tract infections. The aim of this study was to determine the value of the minimum concentration of cefazolin and meropenem on biofilm eradication, as well as the resistance profiles and genetic diversity of clinical and environmental isolates of P. mirabilis. We compared the isolates collected from a hospital environment and from an urban stream impacted in Recife-Pernambuco, Brazil. Biochemical tests were performed to determine the profiles of susceptibility, hydrophobicity, biofilm formation and eradication. The genetic diversity was verified using the ERIC-PCR method. The results revealed that two clinical isolates (ICP4 and ICP5) were multi-drug resistant, whereas the environmental isolates showed resistance only to tetracycline, except for CP25S, which was resistant also to ampicillin. Of the isolates investigated, three were moderately hydrophobic, while the remaining were hydrophilic. Genetic diversity analysis verified the presence of clones indicating that the stream is harboring and disseminating bacteria of hospital origin. All isolates formed a biofilm, however, high concentrations of cefazolin and meropenem were required to eradicate the already formed biofilm. Our study analyzed the survival strategies of these bacteria in the environments investigated and corresponds to first report the use of these antibiotics to eliminate P. mirabilis biofilms.