Polymerase Chain Reaction, Characterization and Antibiogram of Conventional Antibiotics on Escherichia coli 0157:H7 Isolated from Sundried Tomatoes within Kaduna, Nigeria

Abstract: Enterohaemorrhagic E. coli 0157:H7 is a zoonotic pathogen associated with diarrhea, hemorrhagic colitis and hemolytic uremic syndrome.

Aim: The aim of this research was to carry out an assessment of the incidence of Enterohaemorrhagic E. coli 0157:H7 in sun dried tomatoes using PCR.

Study Design: Cross sectional study.

Place and Duration of Study: The research was carried out during dry season, January - April in Kaduna state.

Methodology: A total of 250 samples of sundried tomatoes were collected from open field sun-drying sites and different markets within Kaduna state. E. coli was isolated using most probable number. Colonies showing green metallic sheen were further characterized on cefixime sorbitol macConkey agar at 37oC for 48hours. PCR was used to characterize the shiga-toxin producing bacteria using sets of reported synthetic oligonucleotide probes derived from sequences of the shigatoxin genes: stx1, and stx2.

Results: PCR amplified products identifying the stx1 and stx2 gene sequences were observed in DNA extracted from pale coloured colonies isolated on the cefixime sorbitol macConkey agar. The moisture contents of the sundried tomatoes were variable. The different markets presented moisture content with means; 13.1, 12.9, 12.9, 12.8, 12.7% for Hunkuyi, Samaru-Zaria, Kafanchan, Birnin- Gwari and Kaduna Central market respectively. The total viable bacteria count ranged from 2.3 x 102 – 5.6 x 108 cfu/g. Samples from Hunkuyi drying site presented significantly (P=.05) higher mean total bacterial count of Log108.74±0.33 than Log10 7.43±0.23 from Samaru-Zaria, Kafanchan (Log105.74±0.07), Birnin Gwari (Log105.26±0.05) and central market (Log102.36±0.04). Using disk diffusion method, the Shigatoxin producing E. coli isolates were resistant to chloramphenicol, sparflaxacin, amoxicillin and to some few other common conventional antibiotics but they were sensitive to ciproflacxacin. The prevalence of the isolated pathogens was 2.6% and 1.3% for stx1 and stx2 respectively.

Conclusion: This study has shown sun dried tomatoes could be a vehicle for Shiga-toxin-producing Escherichia coli.0157:H7. Therefore, intervention through the good manufacturing practices and establishment of improved sun drying processes is advocated to avoid life-threatening systemic manifestations often associated with human infections.