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S. aureus recovered from human and murine abscesses displayed heterogeneous colony sizes including a fraction of small colony variants. Distribution of colony sizes 24 hours after plating. Bacteria that were sampled directly from abscesses from a patient (A) or mouse (B, see also SI 4), from eukaryotic A549 cells (C) and from liquid cultures grown at different pHs (D). Bacteria grown exponentially in complex LB medium served as control (dashed black lines). Shaded areas depict the standard deviation. The colored areas under each curve mark colonies whose area was at least 5 times smaller than the area of the most common colony type, the criterion that is generally used to identify SCVs (the figures depict colony radius instead of colony area, and SCVs would thus be defined as colonies whose radius is at least a factor 2.23, i.e., √5, smaller than the radius of the most common colony type. The corresponding frequencies are given above the distributions (labeled as '%nsSCV', 'bdl': below detection limit ). Insets show representative images of colonies 24 hours after plating. Small colonies are indicated by an arrow. All histograms use a binning of 100 µm. Groups in panel D define homogeneous subsets of SCV fractions; treatments with a different group letter (A-D) show significant differences in the proportion of SCVs (at p<0.05, t-test, Bonferroni correction for multiple testing).
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Treatment failure and recurrent infections can occur even when patients are treated with antibiotics to which bacteria are susceptible. These treatment failures could be due to a sub-population of bacteria persisting through the treatment. In this study, we tested the hypothesis that such bacterial persisters manifest in clinical samples as small c...
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... the thigh of a patient. To quantify colony size, we determined the colony radius after 24h of growth. Our quantification showed a distribution of colony sizes with a long tail of smaller colonies, including a small fraction (2.7%) of colonies whose area was five times smaller than the most common colony area, and which therefore qualify as SCV ( Fig. 1A; for discussion on the use of colony size ratio for SCV determination, see SI 3). This contrasted with samples from exponential cultures of the same strain grown in rich bacteria culture medium, wich typically did not show any SCVs (typically under 0.2% of the population; Fig. 1A). Next, we quantified SCVs in a murine abscess model. We ...
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... the most common colony area, and which therefore qualify as SCV ( Fig. 1A; for discussion on the use of colony size ratio for SCV determination, see SI 3). This contrasted with samples from exponential cultures of the same strain grown in rich bacteria culture medium, wich typically did not show any SCVs (typically under 0.2% of the population; Fig. 1A). Next, we quantified SCVs in a murine abscess model. We observed a distribution of colony sizes similar to the . CC-BY-NC-ND 4.0 International license not peer-reviewed) is the author/funder. It is made available under ...
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... copyright holder for this preprint (which was . http://dx.doi.org/10.1101/279968 doi: bioRxiv preprint first posted online Mar. 12, 2018; distribution in the sample from the patient, with a larger proportion of small colonies (5.1%, Fig. 1B). Distribution of colony sizes 24 hours after plating. Bacteria that were sampled directly from abscesses from a patient (A) or mouse (B, see also SI 4), from eukaryotic A549 cells (C) and from liquid cultures grown at different pHs (D). Bacteria grown exponentially in complex LB medium served as control (dashed black lines). Shaded ...
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... plating samples from these cultures, we found that low pH induces a shift towards increasing fractions of SCVs, with up to 25% SCV at pH 4 ( Fig. 1C, 1D), in line with previous work (14). In particular, bacteria sampled from a culture grown at pH 5.5 showed a higher fraction of SCVs compared to bacteria recovered from the murine abscess (p<0.001, t-test on SCV proportion), but similar to the intracellular model (p=0.10, Fig. ...
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... increasing fractions of SCVs, with up to 25% SCV at pH 4 ( Fig. 1C, 1D), in line with previous work (14). In particular, bacteria sampled from a culture grown at pH 5.5 showed a higher fraction of SCVs compared to bacteria recovered from the murine abscess (p<0.001, t-test on SCV proportion), but similar to the intracellular model (p=0.10, Fig. ...
