For this question my first stop is usually ScienceDirect (make sure you’re logged in to Esearch). From there I start with a broad search (using, for example, the keywords: spices foodborne pathogens). When I get to the results page I refine my results even further. Using the tools on the left-hand side of the page I limit my search to only ‘journal’ articles. Then I use the ‘Search within results’ box and add another keyword or two (for example: e. coli). I can continue to narrow my search using the tools on the left-hand side, or by adding more keywords.
When I use ‘garlic’ as a keyword instead of ‘e. coli’ I find the article “Effects of spices on growth and survival of Escherichia coli 0157 and Salmonella enterica serovar Enteritidis in broth model systems and mayonnaise” by Renata G.K Leuschner and Juliette Zamparini. Once I have this article I can use the references at the end of the paper to locate more works on my research topic, or I can do another search.
You might also try Academic Search Complete (which you can find on the databases page). When using the key terms ‘Escherichia coli’, ‘garlic’ and ‘antimicrobial’ (and then restricting my search to ‘Scholarly (Peer Reviewed) Journals’ by using the check box on the left-hand side) I found “Evaluation of antibacterial activity of Indian spices against common foodborne pathogens” by Sofia, Papachan Karur; Prasad, Rajendra; Vijay, Virendra Kumar; and Srivastava, Ashok Kumar.