Abstract
BackgroundMultidrug resistance efflux pumps and biofilm formation are mechanisms by which bacteria can evade the actions of many antimicrobials. Antibiotic resistant non-typhoidal Salmonella serovars have become wide spread causing infections that result in high morbidity and mortality globally. The aim of this study was to evaluate the efflux pump activity and biofilm forming capability of multidrug resistant non-typhoidal Salmonella (NTS) serovars isolated from food handlers and animals (cattle, chicken and sheep) in Lagos.MethodsForty eight NTS serovars were subjected to antibiotic susceptibility testing by the disc diffusion method and phenotypic characterization of biofilm formation was done by tissue culture plate method. Phenotypic evaluation of efflux pump activity was done by the ethidium bromide cartwheel method and genes encoding biofilm formation and efflux pump activity were determined by PCR.ResultsAll 48 Salmonella isolates displayed resistance to one or more classes of test antibiotics with 100% resistance to amoxicillin-clavulanic acid. Phenotypically, 28 (58.3%) of the isolates exhibited efflux pump activity. However, genotypically, 7 (14.6%) of the isolates harboured acrA, acrB and tolC, 8 (16.7%) harboured acrA, acrD and tolC while 33 (68.8%) possessed acrA, acrB, acrD and tolC. All (100%) the isolates phenotypically had the ability to form biofilm with 23 (47.9%), 24 (50.0%), 1 (2.1%) categorized as strong (SBF), moderate (MBF) and weak (WBF) biofilm formers respectively but csgA gene was detected in only 23 (47.9%) of them. Antibiotic resistance frequency was significant (p < 0.05) in SBF and MBF and efflux pump activity was detected in 6, 21, and 1 SBF, MBF and WBF respectively.ConclusionThese data suggest that Salmonella serovars isolated from different food animals and humans possess active efflux pumps and biofilm forming potential which has an interplay in antibiotic resistance. There is need for prudent use of antibiotics in veterinary medicine and scrupulous hygiene practice to prevent the transmission of multidrug resistant Salmonella species within the food chain.
Highlights
Multidrug resistance efflux pumps and biofilm formation are mechanisms by which bacteria can evade the actions of many antimicrobials
Bacterial efflux systems generally fall into five classes, the major facilitator (MF) superfamily, the ATP-binding cassette (ABC) family, the resistancenodulation-division (RND) family, the small multidrug resistance (SMR) family and the multidrug and toxic compound extrusion (MATE) family [3]
Salmonella has at least one multidrug resistant (MDR) pump from each family with the exception of the SMR family of efflux pumps, all of the identified MDR efflux systems exist in E. coli with the exception of MdsABC which is unique to Salmonella [4]
Summary
Multidrug resistance efflux pumps and biofilm formation are mechanisms by which bacteria can evade the actions of many antimicrobials. Antibiotic resistant non-typhoidal Salmonella serovars have become wide spread causing infections that result in high morbidity and mortality globally. The aim of this study was to evaluate the efflux pump activity and biofilm forming capability of multidrug resistant non-typhoidal Salmonella (NTS) serovars isolated from food handlers and animals (cattle, chicken and sheep) in Lagos. Food animals and handlers contribute largely to the spread of zoonotic multidrug resistant non-typhoidal Salmonella. The best characterised of the RND pumps in Salmonella is AcrB and its tripartite complex AcrAB-TolC which has many different substrates making this efflux pump (and other RND homologues) a key mediator of multidrug resistance in Gram negative bacteria including many
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