Survival and Multiplication of Vibrio cholerae Serotype Ogawa in Reconstituted Infant Milk

In vitro studies were conducted to determine the effects of temperature, pH, and competitive growth of other microorganisms on the viability and multiplication of Vibrio cholerae serotype Ogawa in reconstituted infant milk (nonsterile). Following inoculation of milk sample (at a pH range of 6.0 to 6.4), the V. cholerae population detected on thiosulfate-citrate-bile sucrose (TCBS) agar increased from 9.5 × 10³ per g to 7.4 × 10⁴, 2.6 × 10⁸, and 1.9 × 10⁹ per g after 12 h at 4°C, 25°C (room temperature) and 37°C, respectively. At a pH of 5.5, an approximate 100-fold rise in V. cholerae was observed after 12 h at 25°C, while within a pH range of 6.5 to 8.5, a five logarithmic increase in numbers was detected. The presence of other microorganisms did not appear to have any adverse effect on V. cholerae survival and growth in milk. The study demonstrates that at ambient conditions V. cholerae contamination of infant milk formula by carriers or infected mothers could lead to multiplication of the organism and hence pose serious health risk to infants.