Antimicrobial resistance profiles of salmonella spp. and escherichia coli isolated from fresh nile tilapia (oreochromis niloticus) fish marketed for human consumption.

BACKGROUND: Salmonella spp. and pathogenic strains of Escherichia coli are among the major foodborne zoonotic pathogens. These bacterial pathogens cause human illnesses characterized by hemorrhagic colitis, vomiting, nausea, and other agent-related symptoms. The increasing occurrence of antimicrobial resistance in these pathogens is also a serious public health concern globally. Regular surveillance of phenotypes and genotypes of Salmonella spp. and Escherichia coli from animal-derived foods is necessary for effective reduction and control of these foodborne pathogens. This study was conducted to assess the occurrence, antimicrobial resistance, virulence genes and genetic diversity of Salmonella spp. and E. coli isolates from fresh Nile tilapia obtained from retail markets in Nairobi, Kenya. METHODS: A total of 68 fresh Nile tilapia fish samples were collected from retail markets and used for isolation of Salmonella spp. and E. coli. Antimicrobial susceptibilities of the isolates weretested by Kirby-Bauer agar disc diffusion method. According to the antimicrobial resistance profiles, the multi-drug resistant isolates were identified by 16 S rRNA sequencing and phylogenetic analysis using the Bayesian inference method. The MDR Salmonella spp. and E. coli isolates were subjected to PCR-based screening for the detection virulence and antibiotic resistance genes. RESULTS: The prevalence of contamination of the fish samples with Salmonella spp. and E.coli was 26.47% and 35.29% respectively. Overall phenotypic resistance among the Salmonella spp. ranged from 5.5% for ceftazidime, chloramphenicol, meropenem, nitrofurantoin and streptomycin and 22.2% for penicillin-G. For E. coli phenotypic resistance ranged from 4.2% for ceftazidime and chloramphenicol and 25% for rifampicin. Multi-drug resistance was observed in three Salmonella spp. and two E. coli isolates. Results of 16 S rRNA sequences, sequence alignment and phylogenic trees confirmed the identified MDR isolates as S. typhymurium WES-09, S. typhymurium MAK-22, S. typhimurium EMB-32 and E. coli MAK-26 and E. coli LAN-35. The presence of antibiotic-resistance genes belonging to ß-lactamases, tetracycline, sulfonamide, trimethoprim and aminoglycosides-resistant genes were detected in all the identified MDR isolates. CONCLUSIONS: The findings from this study indicate that Nile tilapia (Oreochromis niloticus) sold in retail markets can acts as reservoirs of Salmonella spp. and E. coli pathogens linked to human disease, some of which were multidrug resistance to critically important antimicrobials. Both microorganisms are of zoonotic significance and represent a significant public health risk to the society.

Characterization of sulfated polysaccharide activity against virulent Plasmodium falciparum PHISTb/RLP1 protein.

Background: The emergence of artemisinin resistance in South East Asia calls for urgent discovery of new drug compounds that have antiplasmodial activity. Unlike the classical compound screening drug discovery methods, the rational approach involving targeted drug discovery is less cumbersome and therefore key for innovation of new antiplasmodial compounds.  Plasmodium falciparum (Pf) utilizes the process of host erythrocyte remodeling using Plasmodium-helical interspersed sub-telomeric domain (PHIST) containing proteins, which are amenable drug targets. The aim of this study is to identify inhibitors of PHIST from sulfated polysaccharides as new antimalarials. Methods: 251 samples from an ongoing study of epidemiology of malaria and drug resistance sensitivity patterns in Kenya were sequenced for PHISTb/RLP1 gene using Sanger sequencing. The sequenced reads were mapped to the reference Pf3D7 protein sequence of PHISTb/RLP1 using CLC Main Workbench. Homology modeling of both reference and mutant protein structures was achieved using the LOMETs tool. The models were refined using ModRefiner for energy minimization. Ramachandran plot was generated by ProCheck to assess the conformation of amino acids in the protein model. Protein binding sites predictions were assessed using FT SITE software. We searched for prospective antimalarials from PubChem. Docking experiments were achieved using AutoDock Vina and analysis results visualized in PyMOL. Results: Sanger sequencing generated 86 complete sequences. Upon mapping of the sequences to the reference, 12 non-synonymous single nucleotide polymorphisms were considered for mutant protein structure analysis. Eleven drug compounds with antiplasmodial activity were identified. Both modelled PHISTb/RLP1 reference and mutant structures had a Ramachandran score of >90% of the amino acids in the favored region. Ten of the drug compounds interacted with amino acid residues in PHISTb and RESA domains, showing potential activity against these proteins. Conclusion: These interactions provide lead compounds for new anti-malarial molecules. Further in vivo testing is recommended.

Immunization of rabbits with Glossina pallidipes tsetse fly midgut proteins: effects on the fly and trypanosome transmission.

Proteins isolated from the midgut of Glossina pallidipes were used to immunize rabbits and their efficacy as vaccine candidate(s) against the fly, and their potential to block transmission of Trypanosoma brucei rhodesiense assessed. Two fractions, detergent (DET) and aqueous (AQ) fractions were separated using a non-ionic detergent (Triton X-114) and a series of bioassay experiments carried out using serum obtained from rabbits immunized with either of the two fractions. The mortality rates of tsetse flies fed on serum from rabbits immunized with DET and AQ was 56 and 35%, respectively, as compared to 20% mortality in controls. The DET antigen(s) caused considerably higher mortality (chi(2)=1.194, P<0.05) than that on controls. These findings suggest that midgut proteins contain antigens that are lethal to tsetse flies, and are potential candidates for the development of anti-tsetse vaccine. When flies fed on serum derived from DET immunized rabbits were fed on T. b. rhodesiense infected blood, only 20% of them picked the infection. Very few flies (20%) fed on serum derived from DET immunized rabbits had infection of T. b. rhodesiense. In the control flies 45% of them had infection in the midgut with a higher and actively motile parasite load. Assessment of fecundity indicated significantly higher (chi(2)=2.117, P<0.05) larviposition for the control flies when compared to the AQ group of flies (chi(2)=1.054, P<0.05). Significant differences in abortions and pupal weights were also observed. These results suggest that midgut proteins contain antigens with potential for use in development of vaccine to block transmission of trypanosomes through tsetse.