Coliform count and isolation of Escherichia coli in fresh fruits and vegetables sold at retail outlets in Samaru, Kaduna State, Nigeria

Abstract

Vegetables and fruits are commonly viewed as potential risk factors for infection with enteropathogens. One hundred and eight vegetables and fruits sold within Samaru, Zaria were cultured for coliforms and Escherichia coli using total aerobic plate and coliform counts on Nutrient and MacConkey agar plates respectively, and Eosin Methylene Blue for Escherichia coli isolation. The mean total aerobic plate count (TAPC) ranged between 1.05 ×10¹¹ to 1. 64 ×10¹¹. The highest TAPC (1.64 ×10¹¹) was in pineapple while the lowest count (1.05 ×10¹¹) was in water melon. There was no much difference between the TAPC of lettuce (1.44 ×10¹¹) and cabbage (1.42 ×10¹¹) as well as carrot (1.37 ×10¹¹) and cucumber (1.39 ×10¹¹). Samaru market had the highest (1.56 ×10¹¹) TAPC while Suleiman market had the least (1.30 ×10¹¹). The mean coliform count (TCC) ranged from 1.28×10⁹ to 3.55 ×10⁹ CFU/ml. Carrot (1.28×10⁹) had the lowest TCC while cucumber (3.55 ×10⁹) had the highest. Others were pineapple (2.02 ×10⁹), water melon (3.05 ×10⁹), lettuce (3.17 ×10⁹) and cabbage (2.72 ×10⁹) CFU/ml. Out of 108 samples obtained, 50 (46.3%) were suspected to be E. coli with 23 (46%) yielding reactions typical of E. coli, with an overall prevalence of 21.3%. Cucumber had the highest isolation of 5 (27.8%) while the least was water melon 1 (5.6%). Other coliforms isolated were Klebsiella (8.3%), Enterobacter (7.4%), Citrobacter (5.5%), Proteus (2.7%) and Serratia (0.93%) spp. This study has demonstrated the public health significance of consuming fresh fruits and vegetables sold in the study area as they may be sources of infection to consumers especially if the produces are not properly washed or cooked.

Keywords: Coliform, E.coli, Fruits, Vegetables