Effect of Shifting Temperatures on the Growth and Survival of Klesiella pneumoniae in Selected Milks and Their Substitutes

Abstract

Introduction: Milk is one of the good sources for bacterial growth. Poor consumer handling may result in temperature abuse of milk and aid the growth of bacteria. Klebsiella pneumoniae is one of the predominant bacteria present in milk that can cause foodborne diseases. The main objective of this study was to determine the adaptation and survival curves of K. pneumoniae ATCC 13883 shifted from 37°C to various stress temperatures in fresh raw coconut milk, pasteurised cow's milk, and Ultra-High Temperature (UHT) coconut milk. Methods: The first part of the study was aimed to determine the microbiological quality of milks and constitutes using Tryptone Soy Agar (TSA) and Eosin Methylene Blue (EMB) Agar. Secondly, the growth curve for K. pneumonia at 37°C in Tryptone Soy Broth (TSB) was established. In the third part of study, a stationary phase culture of K. pneumoniae was grown in TSB for 24 hours before shifting to coconut milk, pasteurised cow milk and UHT milk at different temperatures: 7°C, 27°C, 55°C and 65°C. Results: K. pneumoniae shifted from 37°C to 7°C showed bacteriostatic effects, while shifting K. pneumoniae from 37°C to at 27°C did not affect the growth potential in any of the samples. By contrast, K. pneumoniae shifted to 55°C only exhibited thermotolerance in fresh raw coconut milk, while survival curves of K. pneumoniae exhibited straight-line death kinetics when shifted to 65°C in all kinds of milk. Conclusion: The growth and survival of K. pneumoniae depend on the temperature stress conditions and types of media used.