A cross-sectional study on the microbiological quality and safety of raw chicken meats sold in Nairobi, Kenya

Abstract

Background: Chicken is a rich source of meat protein and is increasingly being consumed in urban areas in Kenya. However, under poor hygienic environment, raw chicken meat presents an ideal substrate supporting the growth of pathogenic Escherichia coli and Coliform bacteria indicating the potential presence of other pathogenic bacteria; this may constitute a major source of food-borne illnesses in humans. This study sought to assess the microbiological quality and safety of raw chicken meat sold in Nairobi, Kenya by determining the E. coli/coliform contamination levels as well as the antimicrobial resistance patterns and pathogenicity of E. coli isolated.

Findings: We conducted a Cross-sectional study to collect two hundred raw chicken samples that were randomly purchased between the periods of August 2011-February 2012. Enumeration of bacteria was done using 3 M Petri film E. coli/Coliform count plates, isolation and identification of E. coli through standard cultural and biochemical testing, antimicrobial susceptibilities interpreted according to criteria set by the Clinical and Laboratory Standards Institute (2012) while Polymerase chain reaction assays were used to determine presence of virulence genes in isolated E. coli. Data was analyzed using SPSS version 17.0. Contamination rates were 97% and 78% respectively for Coliform bacteria and E. coli. Seventy six percent of samples fell under the unacceptable microbial count limit (>100 cfu/ml) and significant differences in the E. coli/coliform counts (p < 0.001) were observed among the chicken retail outlets with samples from supermarkets having the lowest level of contamination compared to the rest of the retail outlets. Seventy five percent of the isolates were resistant to at least one of the 12 antibiotics tested with resistance to tetracycline being the highest at 60.3%. In addition 40.4% E. coli isolates were positive for the ten virulence genes tested.

Conclusion: Raw retail chicken meats in Nairobi are not only highly contaminated, but also with potentially pathogenic and multi-drug resistant strains of E. coli. It will be important for public health authorities and retail chicken processing outlets to collaborate in ensuring adherence to set out principles of hygienic processing and handling of chicken meats in order to reduce potential risks of infection.

Figure 1

Distribution of E. coli count among the 5 retail outlet classifications. Counts were evenly distributed., the size of the boxes for high- middle income, low-middle income and low income areas indicate that the middle 50% E. coli counts are spread out for these groups while for high class butcheries and supermarkets the box sizes indicate that the middle 50% of the counts are clumped together.

Figure 2

Distribution of Coliform count among the 5 retail outlet classifications. Apart from supermarkets, the other 4 retail outlet classifications have bulk of the count concentrated on the high end of the scale.