Hyaluronate Lyase Gene of \u3ci\u3eStreptococcus pyogenes\u3c/i\u3e: Molecular Characterization and Regulation

Streptococcus pyogenes causes an assortment of diseases ranging from pharyngitis to necrotizing fasciitis. This bacterium has the ability to elaborate several extracellular products capable of causing tissue damage; one of which is a hyaluronate lyase. Little information is available regarding the regulation of streptococcal hyaluronidase. As such, the expression of hylA in the hyaluronate lyase-producing strain ATCC 10403 and in strains that do not produce detectable enzyme was analyzed by RT-PCR and quantitative PCR. Hyaluronate lyase transcript was detected throughout growth for all strains; however, expression of hylA in the enzymatically inactive strains, 71698 and SF370, was determined to have a different pattern of expression than that of the active strain 10403. The effect of various environmental conditions on hylA expression was evaluated. Temperature had little effect on the relative amount of hylA transcript for strain 10403. However, hyl A expression was slightly decreased after growth in pH 5.0 and increased under anaerobic and increased carbon dioxide conditions. The presence of hyaluronic acid in the growth media resulted in a two-fold increase in hylA expression. However, no difference was detected in the titer of enzymatic activity. Expression of hylA and hasA were examined for the hyaluronate lyase non-producing strain 71698; and indicated the relative amount of hasA transcript was considerably greater than that of hylA. Also, 176 strains of S. pyogenes were screened by PCR for hylA and showed all contained the gene; however, 34 strains showed a decrease in the size of the 3′region. The 3 ′ region was PCR amplified, cloned, and the sequence determined from six of these 34 strains. Comparison of the sequences revealed a deletion of 183 bp in the same location in all six strains. A preliminary analysis of the role of hyaluronate lyase in streptococcal infection was evaluated. Preliminary data suggests hyaluronate lyase to be an important virulence factor as was determined by a 5.7% reversion of single-recombinant mutant strain 10403::pHAS:hylA from a HylA-negative to a HylA-positive phenotype. For future virulence studies, an isogenic mutant strain 10403ΔhylA was created by replacing an internal portion of hylA with erythromycin resistance gene (ermR). Inactivation of hyaluronate lyase did not affect growth or protease or hemolytic activities

Hyaluronidases of Gram-Positive Bacteria

Bacterial hyaluronidases, enzymes capable of breaking down hyaluronate, are produced by a number of pathogenic Gram-positive bacteria that initiate infections at the skin or mucosal surfaces. Since reports of the hyaluronidases first appeared, there have been numerous suggestions as to the role of the enzyme in the disease process. Unlike some of the other more well studied virulence factors, much of the information on the role of hyaluronidase is speculative, with little or no data to substantiate proposed roles. Over the last 5 years, a number of these enzymes from Gram-positive organisms have been cloned, and the nucleotide sequence determined. Phylogenetic analysis, using the deduced amino acid sequences of the Gram-positive hyaluronidases, suggests a relatedness among some of the enzymes. Molecular advances may lend to a more thorough understanding of the role of hyaluronidases in bacterial physiology and pathogenesis. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Effect of Antiplatelet Therapy on Survival and Organ Support–Free Days in Critically Ill Patients With COVID-19

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