Frequency and antimicrobial resistance of enteric bacteria with spoilage potential isolated from table eggs

The prevalence of potential spoilage microorganisms on the shells and in the egg contents of table eggs sold in Trinidad was determined. Table eggs samples were obtained from 23 poultry layer farms, 14 shopping malls and 102 supermarkets across the country. Each farm was visited twice approximately one month apart and 25 pooled eggs constituted a composite sample. Shopping malls were each visited twice usually one month apart while supermarkets were each visited once over a 4-month period. For both mall and supermarkets, six pooled eggs constituted a composite sample. Swabs of egg shells and pooled yolk and albumen (egg content) were tested for selected bacteria using standard methods. The resistance of bacteria to seven antimicrobial agents was detected using the disc diffusion method. Of a total of 184 composite eggs (shells, yolk/albumen or both) sampled, 71 (38.6%) samples were positive for enteric microbes, other than E. coli, Salmonella, Campylobacter spp. and Listeria spp. Enterobacter spp. and Klebsiella spp. were isolated from 15 (8.2%) and 14 (7.6%), respectively, of pooled egg shells alone and from 6 (3.3%) and 3 (1.6%), respectively, of egg content samples alone. Prevalence of enteric bacteria in egg contents was generally higher than found on egg shells with faeces/blood or cracks compared with those without, but the differences were not significant (P > 0.05; X2). The microbial load of egg content was not significantly affected by type of housing of laying birds, source of feeds, use of medicated feeds and temperatures at which eggs were kept at sale outlets. Of a total of 131 bacterial isolates tested, 125 (95.4%) exhibited resistance to one or more antimicrobial agents and resistance was high to streptomycin (90.1%), tetracycline (51.9%) and kanamycin (30.5%). Failure to properly handle or heat table eggs sold in Trinidad poses a potential health hazard to consumers because of their poor microbial quality and high frequency of resistance to antimicrobial agent.