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Biochemically aberrant Salmonella enteritidis ser. newington from human sources in Connecticut
Abstract:
Three isolates of a lactose-fermenting, xylose-negative variety of Salmonella enteritidis ser. newington, identical in biochemical and serological reactions and in the antibiogram, were recovered from three patients in different areas of Connecticut in January 1974. Hydrogen sulfide production was not visible in Salmonella-Shigella agar, in triple sugar iron agar, and in Kligler iron agar but was noticed in lysine iron agar and on XLD agar, among others. The amount of fermentable carbohydrates present was found to correlate with failure to show hydrogen sulfide production (pH effect). In contrast to lactose-fermenting Salmonella strains reported by other authors, we could not elicit a direct transfer of the lac(+) character at frequencies above 10(-6). An epidemiological follow-up remained unsuccessful. Recommendations for the recognition of similar strains are presented.
Insights
This study identified a unique lactose-fermenting Salmonella enteritidis ser. newington strain that did not produce hydrogen sulfide. This finding has implications for laboratory identification of Salmonella infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacteriology
Background:
- Salmonella enteritidis ser. newington is a common bacterial pathogen.
- Lactose-fermenting Salmonella strains are rare and can be difficult to identify using standard biochemical tests.
- Hydrogen sulfide (H2S) production is a key characteristic used in Salmonella identification.
Purpose of the Study:
- To characterize a novel lactose-fermenting, xylose-negative Salmonella enteritidis ser. newington strain.
- To investigate the biochemical properties, including H2S production and lactose fermentation, of this unusual isolate.
- To assess the potential for genetic transfer of the lactose-fermenting trait.
Main Methods:
- Isolation and biochemical characterization of three bacterial strains from patients.
- Serological testing and antibiogram analysis.
- Evaluation of H2S production on various agar media (e.g., Salmonella-Shigella agar, triple sugar iron agar, Kligler iron agar, lysine iron agar, XLD agar).
- Investigation of lactose (lac+) character transfer frequencies.
Main Results:
- Three identical isolates of Salmonella enteritidis ser. newington were recovered, exhibiting lactose fermentation and xylose negativity.
- Failure to detect hydrogen sulfide production on several standard media, with H2S production observed on lysine iron agar and XLD agar.
- A correlation between fermentable carbohydrate concentration and H2S production (pH effect) was noted.
- Low frequency (below 10^-6) of direct lac+ character transfer was observed.
Conclusions:
- A distinct variant of Salmonella enteritidis ser. newington with altered H2S production and lactose-fermenting capabilities was identified.
- Standard biochemical media may not reliably detect this strain due to suppressed H2S production.
- Recommendations are provided for improved laboratory recognition of similar Salmonella strains to aid in accurate diagnosis and public health surveillance.