Thermo Fisher Scientific has agreed to sell its microbiology business to private equity firm Astorg for approximately $1.075 billion, as the company continues to reshape its diagnostics portfolio.

The Waltham, Massachusetts-based company said the transaction includes cash proceeds and a $50 million seller note. The unit being divested focuses on antimicrobial susceptibility testing and culture media used in clinical diagnostics, pharmaceutical development and food safety applications. It generated about $645 million in revenue in 2025 and currently sits within Thermo Fisher’s specialty diagnostics segment.

Company leadership framed the move as part of an ongoing effort to reallocate capital. “The transaction reflects our active management of the company and provides additional capital we can deploy to create shareholder value,” said Marc N. Casper, chairman and chief executive officer of Thermo Fisher. “We believe the microbiology business is an excellent fit within Astorg’s portfolio. We are confident in a smooth transition and wish the business and colleagues continued success after close under its new ownership.”
Thermo Fisher expects the deal to close in the second half of 2026, pending regulatory approvals and other standard conditions. The company said the divestiture is expected to reduce adjusted earnings per share by $0.15 in the first full year after closing. Additional details on the financial impact are expected during its second-quarter earnings call.

Astorg, a pan-European private equity firm with a history of healthcare investments, will take ownership of a business that serves a range of laboratory and industrial customers. The deal continues a broader trend of portfolio realignment among large diagnostics and life sciences companies, as firms prioritize higher-growth or strategically aligned segments.

Financial and legal advisors on the transaction include Perella Weinberg Partners and Wells Fargo for Thermo Fisher, and Evercore and Moelis for Astorg.

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