COMPARISON OF ENRICHMENT BROTHS FOR DETECTION AND ISOLATION OF ENTEROBACTER SAKAZAKII FROM INFANT FORMULA MILK

Enterobacter sakazakii is a member of the Enterobacteriaceae and has physiological characteristics similar to those of Escherichia coli O157:H7 (negative D-sorbitol fermentation, positive glucose and lactose fermentation, and negative H2S production). The purpose of this study was to evaluate the efficiency of enrichment broths recommended for E. sakazakii enrichment. Growth and recovery ratio of E. sakazakii were compared in media including modified tryptone soya broth supplemented with novobiocin (mTSB + N), modified Escherichia coli broth with novobiocin (mEC + N), Enterobacteriaceae enrichment (EE) broth, buffered peptone water supplemented with vancomycin, cefixime and cefsulodin (BPW + VCC), and rehydrated infant milk formula (IMF) with or without antibiotics. The EE broth that was recommended by the FDA showed the most effective enrichment for growth of E. sakazakii, followed by rehydrated IMF. Other media such as mTSB + N, mEC + N and BPW + VCC did not support growth of E. sakazakii compared to EE and rehydrated IMF. They were not considered suitable for the enrichment of E. sakazakii. When evaluated for recovery of E. sakazakii among other Enterobacteriaceae, strains of E. sakazakii were all recovered in EE broth after 6 and 18 h; thus, the EE broth was considered the most effective enrichment broth in this study. Rehydrated IMF also showed higher recovery ratios (3/4, 4/4) after 6 and 18 h than the other recommended enrichment broths.