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. 2017 Mar 1:581-582:750-755.
doi: 10.1016/j.scitotenv.2017.01.003. Epub 2017 Jan 5.

Analysis of home dust for Staphylococcus aureus and staphylococcal enterotoxin genes using quantitative PCR

Shanna Ludwig  1 , Isabel Jimenez-Bush  2 , Emily Brigham  3 , Sonali Bose  3 , Gregory Diette  3 , Meredith C McCormack  3 , Elizabeth C Matsui  3 , Meghan F Davis  2
Affiliations

Analysis of home dust for Staphylococcus aureus and staphylococcal enterotoxin genes using quantitative PCR

Shanna Ludwig et al. Sci Total Environ. .

Abstract

Background: The bacterium Staphylococcus aureus (SA) is known to induce allergic inflammatory responses, including through secreted staphylococcal enterotoxin (SE) superantigens. To quantify indoor environmental exposures to these potential allergens, which may be associated with worse asthma, we developed a method for the assessment of S. aureus and SE in home dust and applied it to a study of homes of inner-city adults with asthma.

Methods: We conducted laboratory experiments to optimize sample processing and real-time PCR methods for detection and quantification of SA (femB) and SEA-D, based on published primers. We applied this method to dust and dust extract from 24 homes. We compared results from real-time PCR to culture-based results from the same homes.

Results: The bacteremia DNA isolation method provided higher DNA yield than alternative kits. Culture-based results from homes demonstrated 12 of 24 (50%) bedrooms were contaminated with S. aureus, only one of which carried a SE gene (SEC). In contrast, femB was detected in 23 of 24 (96%) bedrooms with a median of 1.1×106 gene copies detected per gram of raw dust. Prevalence and median copy number (shown in parenthesis) of SE gene detection in bedroom dust was: SEA 25% (1.4×102); SEB 63% (1.4×103); SEC 63% (1.1×103); SED 21% (1.3×102).

Conclusions: Our culture-independent method to detect S. aureus and SE in home dust was more sensitive than our culture-based method. Prevalence of household exposure to S. aureus and SE allergens may be high among adults with asthma.

Keywords: Allergy; Asthma; Indoor dust; Staphylococcal enterotoxin; Staphylococcus aureus; Superantigen.

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Figures

Figure 1
Figure 1
Comparison of DNA yield from dust spiked with calibrated volumes (1μl and 10μl) of Staphylococcus aureus ATCC 13565 subjected to extraction using bacteremia and soil DNA isolation kits. n=3 replicates.
Figure 2
Figure 2
Detection of S. aureus (femB) and SEA-D genes in dust from 17 homes, comparing log number of gene copies per gram of dust detected in raw dust versus dust extract. Light-colored lines represent the limits of detection (LOD); points have been jittered to better illustrate the data, given the large numbers of data points at or below the LOD; the dark-colored line represents the line of best fit.
See this image and copyright information in PMC

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