The microdrip method rapidly and efficiently enumerates bacterial colony-forming units in bovine milk

Area of Science:

• Veterinary Microbiology
• Bovine Mastitis Research
• Bacterial Enumeration Techniques

Background:

• In vivo microbial challenge models are crucial for understanding bovine mastitis mechanisms.
• Accurate bacterial load enumeration in milk is essential for assessing intervention efficacy.
• Standard plating methods for bacterial enumeration are time-consuming and costly.

Purpose of the Study:

• To evaluate a microdrip method as a cost-effective and time-efficient alternative for enumerating Escherichia coli P4 in milk.
• To assess the rigor and reproducibility of the microdrip method compared to standard plating.
• To determine the sensitivity and economic viability of the microdrip method.

Main Methods:

• Comparison of bacterial counts using the microdrip method versus standard plate counts with E. coli P4-spiked milk samples.
• Linear regression and Bland-Altman analysis to assess agreement between methods.
• Sensitivity testing and economic analysis of consumable costs.

Main Results:

• The microdrip method showed no significant difference or technician bias compared to standard plate counts.
• Microdrip method demonstrated a slight positive bias proportional to concentration.
• Microdrip method achieved a sensitivity of 10^3 CFU/mL, outperforming qPCR (10^4 CFU/mL) and reducing costs by nearly 50%.

Conclusions:

• The microdrip method offers a rigorous, reproducible, and cost-effective approach for enumerating E. coli P4 in milk for mastitis research.
• Milk sample storage at 4°C or -80°C does not affect CFU counts, allowing for batched processing.
• This method has potential for broader applications in pathogen monitoring and clinical diagnostics.