Association of multicellular behaviour and drug resistance in Salmonella enterica serovars isolated from animals and humans in Ethiopia

Aims: To determine the association between multicellular behaviour, integron status and antibiotic resistance among 87 Ethiopian Salmonella enterica isolates of animal and human origin. Methods and Results: Isolates were characterized for their biofilm forming ability, antimicrobial susceptibility and the presence and characteristics of a class 1 integron and Salmonella genomic island 1 (SGI1). The majority of isolates grown at environmental temperatures (20°C) exhibited robust biofilm formation (72·4%) and displayed RDAR colony morphology on Congo red agar plates. The presence of a class 1 integron correlated with the extent of drug resistance and ability to exhibit multicellular behaviour. Conclusions: Although cellulose production and RDAR morphology correlated with increased multicellular behaviour, neither was required for biofilm formation. Contrary to previous reports, colony morphology was generally consistent within a serovar. No integrons were detected in isolates deficient for multicellular behaviour, indicating a potential role of bacterial community formation in transfer of genetic elements among environmental isolates. Significance and Impact of Study: Infection by Salm. enterica is a major public health problem worldwide. The dominance of multidrug resistance and multicellular behaviour in Salmonella isolates of Ethiopian origin highlights a need for integrated surveillance and further detailed phenotypic and molecular studies of isolates from this region.