Disruption of staphylococcal aggregation protects against lethal lung injury
Jaime L. Hook, … , Sunita Bhattacharya, Jahar Bhattacharya
Jaime L. Hook, … , Sunita Bhattacharya, Jahar Bhattacharya
Published March 1, 2018
Citation Information: J Clin Invest. 2018;128(3):1074-1086. https://doi.org/10.1172/JCI95823.
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Categories: Research Article Cell biology Pulmonology

Disruption of staphylococcal aggregation protects against lethal lung injury

Abstract

Infection by Staphylococcus aureus strain USA300 causes tissue injury, multiorgan failure, and high mortality. However, the mechanisms by which the bacteria adhere to, then stabilize on, mucosal surfaces before causing injury remain unclear. We addressed these issues through the first real-time determinations of USA300-alveolar interactions in live lungs. We found that within minutes, inhaled USA300 established stable, self-associated microaggregates in niches at curved, but not at flat, regions of the alveolar wall. The microaggregates released α-hemolysin toxin, causing localized alveolar injury, as indicated by epithelial dye loss, mitochondrial depolarization, and cytosolic Ca2+ increase. Spread of cytosolic Ca2+ through intercellular gap junctions to adjoining, uninfected alveoli caused pulmonary edema. Systemic pretreatment with vancomycin, a USA300-cidal antibiotic, failed to protect mice infected with inhaled WT USA300. However, vancomycin pretreatment markedly abrogated mortality in mice infected with mutant USA300 that lacked the aggregation-promoting factor PhnD. We interpret USA300-induced mortality as having resulted from rapid bacterial aggregation in alveolar niches. These findings indicate, for the first time to our knowledge, that alveolar microanatomy is critical in promoting the aggregation and, hence, in causing USA300-induced alveolar injury. We propose that in addition to antibiotics, strategies for bacterial disaggregation may constitute novel therapy against USA300-induced lung injury.

Authors

Jaime L. Hook, Mohammad N. Islam, Dane Parker, Alice S. Prince, Sunita Bhattacharya, Jahar Bhattacharya

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Figure 1

Inhaled S. aureus form MAs at alveolar niches.

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Inhaled S. aureus form MAs at alveolar niches. (A) Low-power (inset) an...
(A) Low-power (inset) and high-power confocal images of a live mouse alveolus (red) show different-sized MAs (arrows) of GFP-labeled S. aureus strain USA300 (green) at niches, curved alveolar regions where alveolar septa converge. Example niche-forming septa are indicated by i–iii. Dashed lines demarcate alveolar walls. AuF, autofluorescence; alv, alveolus. Scale bars: 50 (inset) and 8 μm. Replicated in 4 lungs. (B) Effect of inoculum size on MA distribution and distance of contact between MAs and the epithelium. Bars: mean ± SEM; n = 3 lungs in which fluorescence was quantified in 30 (left bars) or 3 (middle and right bars) alveoli per lung; *P < 0.05 using 2-tailed t test. (C) Bacterial counts of MAs. Each point represents a single MA selected from 3 lungs. Line calculated by linear regression (P < 0.05). (D) H&E- and Gram-stained histological sections of lung tissue show low-power (inset) and high-power views of USA300 MAs (arrows) in niches of multiple alveoli. Scale bars: 100 (inset) and 10 μm. Replicated in 3 lungs. (E) Low-power (inset) and high-power confocal views of a calcein-loaded alveolus (red) in a human lung, 10 minutes after alveolar microinstillation of WT USA300 (green). Arrows indicate bacterial MAs in alveolar niches. CR, calcein red. Scale bars: 50 (inset) and 20 μm. Replicated in 3 alveoli.