Assessment Of Temperature And Salt Stress Tolerance In Klebsiella Pneumoniae Isolated From Dairy Sources In Karbala Province

Abstract

Background:
Klebsiella pneumoniae is a significant opportunistic pathogen that poses a public health risk, especially when present in food products such as dairy and meat. Contamination of food with this bacterium can lead to transmission of antibiotic-resistant strains and foodborne illness.

Materials and methods :
A total of 525 samples (dairy and meat) were collected from retail markets in Karbala city, Iraq. Samples were cultured on MacConkey agar and CHROMagar™ Orientation to isolate presumptive K. pneumoniae colonies. Identification was confirmed by PCR targeting the 16S-23S ITS region, yielding a specific product of 130 base pairs. Heat tolerance was evaluated by treating milk samples at 60°C, 65°C, and 70°C for 30 minutes, followed by culturing. Salt tolerance was assessed by incubating bacteria in 0.5%, 1%, and 1.5% NaCl solutions for 1–2 weeks, with subsequent growth checked on Mueller-Hinton agar.

Results:
All cultured samples exhibited characteristic K. pneumoniae colony morphology within 24 hours. PCR amplification confirmed the presence of K. pneumoniae in the dairy and meat samples, with bands observed at 130 bp. Growth was observed in milk samples treated at 60°C and 65°C, but not at 70°C, suggesting thermal elimination at higher temperatures. Short-term salt tolerance was observed at all concentrations, but no viable bacteria were detected after two weeks of incubation.

Conclusion:
Klebsiella pneumoniae was detected in food samples from Karbala, indicating potential contamination risks. The bacterium exhibited limited heat and salt tolerance, supporting the effectiveness of standard pasteurization and preservation methods. Molecular confirmation using ITS-PCR provided reliable identification beyond culture-based techniques.