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Biofilm formation and multicelluar morphotypes of Salmonella enterica serovars isolated from animals and humans in Ethiopia

Research Scholar

Tadesse Eguale Habtemariam, Veterinary Preventive Medicine (Ethiopia)
Aditi Bhatiya, Co-Reseacher
Joanna Marshall, Co-Researcher
Bayeleyegn Molla, Co-Researcher
Wondwossen Gebreyes, Co-Researcher
John Gunn, Faculty Mentor


Tadesse Eguale Habtemariam, born in Ethiopia, earned his DVM and MSc from Addis Ababa University (AAU) in Ethiopia, where worked as a field veterinarian, animal health researcher and university instructor. In 2010, he started his PhD studies at AAU. Currently, he is working in the laboratory of John Gunn, Ohio State Department of Microbial Infection and Immunity, as a visiting research scholar. His PhD research work is sponsored through The Ohio State University National Institutes of Health Fogarty International Center grant.

What is the issue or problem addressed in your research?

Recently, it has been demonstrated that many bacterial species have the ability to form multicellular communities, termed biofilms, wherein bacteria aggregate and encase themselves in a protective matrix. Biofilm formation facilitates bacterial adherence to a variety of surfaces and increases resistance to disinfectants, biocides and antibiotics. Biofilm formation by Salmonella spp. is a major factor contributing to persistence of the organism in the environment as well as virulence in the host. Though, Salmonella is highly prevalent in Ethiopia, nothing is known about their biofilm forming ability. Therefore, we proposed to study biofilm forming ability of animal and human isolates of Salmonella from Ethiopia. Eighty-seven isolates were tested in vitro for their ability to produce biofilm and for production of molecules facilitating cellular aggregation and surface adhesion.

What methodology did you use in your research?

The crystal violet binding assay (CVA) was used to assess biofilm formation and pellicle formation was investigated in liquid media. Characterization of multicellular colony morphology was assessed on congo red agar and extracellular cellulose production was assessed using a calcofluor binding assay.

What are the purpose/rationale and implications of your research?

The main purpose of this work was to investigate biofilm forming ability of isolates and determine major components of biofilm matrix. The majority of isolates were strong biofilm producers most of them characterized by red dry and rough (RDAR) morphotype caused by extracellular matrix composed of cellulose and curli (72.4%). The greatest biofilm occurred at 20±10C. There was significant difference among serovars in biofilm formation. Morphotype, pellicle formation and cellulose production at 20±10C for most of the strains was serovar specific. Interestingly, at 370C, though all isolates did not produce cellulose and curli (molecules known to be important for biofilm formation), most of them were able to produce biofilm.  At 370C, biofilm formation appears to be independent of cellulose and curli and may involve other extracellular matrix.