A comparative study of cultural and molecular techniques for the identification of bacterial contaminants of cockroaches (Periplaneta americana)

The increasing trends of insect associated bacterial infection in humans are severely hampered by disparaging number of bacteria obtained with the culture-based technique. This study therefore determined how the analysis of the 16S rDNA sequences would compare in terms of precision and reliability to the most adoptable culture-based technique. Results obtained depict enhanced accuracy of  molecular technique over the cultural method as only 249 (69%) of the total isolates were correctly identified by the cultural method to represent a total of 114 (31%)  discrepant species while 100% correct identification was observed with the molecular technique. The most predominant of these bacterial isolates from both the external surfaces and the gut environment was Escherichia coli 43 (20.8%) and 24 (15.5%) respectively. The Gram positive organisms isolated were Staphylococcus aureus, Bacillus subtilis, Staphylococcus epidermidis, and Enterococcus faecalis with a prevalence rate of 8 (3.8%), 14 (6.7%), 8 (3.8%) and 9 (4.3%) from external surfaces and 2 (1.3%), 6 (3.9%), 2 (1.3%) and 7 (4.5%) from gut environment respectively. The least isolated organisms in the external surfaces were Serratia marscencens and Citrobacter werkmanii with a distribution rate of 3(1.4%) while Citrobacter freundii 2(1.3%) was the least isolated organism from cockroach gut environment. This study therefore showed that the molecular analysis of the 16S rDNA sequences is more efficient than culture-based technique for the identification of bacterial contaminants of cockroaches because occurrences of misidentification are very much abated by this method.  Key words: Bacterial contaminants, Cockroaches (Periplaneta americana), cultural technique, molecular technique.