Hydrogen Sulfide Negative Salmonella and their Implication for Standard Culture-based Identification

Area of Science:

• Microbiology
• Food Safety
• Clinical Diagnostics

Background:

• Salmonella is typically identified by hydrogen sulfide (H2S) production, indicated by black precipitate on culture media.
• H2S-negative Salmonella serovars present a diagnostic challenge, potentially evading standard isolation protocols.
• Phenotypic variability in H2S production among Salmonella strains necessitates updated detection strategies.

Purpose of the Study:

• To review the phenotypic variability of H2S production in Salmonella.
• To summarize global reports of H2S-negative Salmonella serovars.
• To propose improved strategies for detecting atypical H2S-negative Salmonella strains.

Main Methods:

• Literature review of phenotypic variability and H2S production in Salmonella.
• Analysis of recent global reports on H2S-negative Salmonella serovars.
• Evaluation of current H2S-dependent and alternative isolation methods.

Main Results:

• Factors such as media composition and incubation duration influence Salmonella H2S production.
• H2S-negative Salmonella serovars are increasingly reported globally.
• Current H2S-dependent methods have limitations in detecting these atypical strains.

Conclusions:

• H2S-negative Salmonella serovars continue to occur and pose a risk.
• Integrating non-H2S-dependent techniques, like chromogenic agars, alongside traditional methods is crucial.
• Parallel plating and confirmation of both black and nonblack colonies enhance Salmonella detection accuracy.