Phenotypic Characterisation of Escherichia coli Isolates from Fish, Diarrheic and Healthy Children in Zanzibar, Tanzania

Aims: This study was carried out with the objective of investigating E. coli virulence factors, antibiotic sensitivity, presence of extended-spectrum-β-lactamase [ESBL] and serotype H1 O157 in E. coli from fish foods in comparison with those from healthy and diarrheic children in Zanzibar.

Study Design: Repeated cross sectional design was used to collect samples from fish, vendors and fish consumers through the seasons. Cross sectional design was used to collect children faecal samples from Mnazimmoja referral hospital.

Place and Duration of Study: The study was carried out in Zanzibar between August 2014 and June 2016

Methodology: A total of 113 E. coli isolates from fish (58), diarrheic (35) and healthy children (20) less than five years old were screened. Serotyping was used for detection of serotype O157 and extended-spectrum-β-lactamases (ESBL) production by disc diffusion using Cepodoxime/clavulanic acid (10/1μg) discs. Hemolysin was detected by hemolysis in human blood agar, serum resistance factors by growth inhibition of E. coli that was mixed and incubated with human sera, Hemagglutinins by Hemagglutination of RBCs and Gelatinase enzyme by production of clear zone of degradation of gelatine. Statistical analysis was done using Medcalc statistical software. Statistical difference in virulence factors possession data in E. coli isolates between fish, diarrheic and healthy children were subjected to analysis of variance [ANOVA], where p<0.05 was judged indicative of significant difference.

Results: Virulence factors detected in their order of prevalence were hemolysins (21.2%), serum resistance (12.2%), hydrophobicity (8.8%), Hemagglutinins (4.4%), and Gelatinase (2.7%). Virulence factors were detected in 82.9% and 38% of diarrheic children and fish isolates respectively. E. coli O157 serotype was detected in all 3 sources with higher percentage in diarrheic children (6.8%). Extended spectrum β-lactamase E. coli producers were found in fish (6.8%) and diarrheic samples (17.1%) but not from healthy children. Multidrug resistance [MDR] was detected in fish (44.9%), diarrheic children (82.8%) and healthy children (10%). Ampicillin (100%; 22.4%) and Tetracycline (82.9%; 44.8%) exhibited high antibiotic resistance both in diarrheic children and fish respectively. Fish foods could be sources of pathogenic and antibiotic resistant E. coli possessing multiple virulence factors. Moreover O157 serotypes, ESBL producing and multidrug resistant E. coli were also detected in fish foods.

Conclusion: It is therefore emphasised to improve hygiene in the fish value chain as well as raise awareness and frequent monitoring to fish stakeholders in Zanzibar.