A genetic screen identifies a role for oprF in Pseudomonas aeruginosa biofilm stimulation by subinhibitory antibiotics.

Biofilms are surface-associated communities of bacteria that grow in a self-produced matrix of polysaccharides, proteins, and extracellular DNA (eDNA). Sub-minimal inhibitory concentrations (sub-MIC) of antibiotics induce biofilm formation, potentially as a defensive response to antibiotic stress. However, the mechanisms behind sub-MIC antibiotic-induced biofilm formation are unclear. We show that treatment of Pseudomonas aeruginosa with multiple classes of sub-MIC antibiotics with distinct targets induces biofilm formation. Further, addition of exogenous eDNA or cell lysate failed to increase biofilm formation to the same extent as antibiotics, suggesting that the release of cellular contents by antibiotic-driven bacteriolysis is insufficient. Using a genetic screen for stimulation-deficient mutants, we identified the outer membrane porin OprF and the ECF sigma factor SigX as important. Similarly, loss of OmpA - the Escherichia coli OprF homolog - prevented sub-MIC antibiotic stimulation of E. coli biofilms. Our screen also identified the periplasmic disulfide bond-forming enzyme DsbA and a predicted cyclic-di-GMP phosphodiesterase encoded by PA2200 as essential for biofilm stimulation. The phosphodiesterase activity of PA2200 is likely controlled by a disulfide bond in its regulatory domain, and folding of OprF is influenced by disulfide bond formation, connecting the mutant phenotypes. Addition of reducing agent dithiothreitol prevented sub-MIC antibiotic biofilm stimulation. Finally, activation of a c-di-GMP-responsive promoter follows treatment with sub-MIC antibiotics in the wild-type but not an oprF mutant. Together, these results show that antibiotic-induced biofilm formation is likely driven by a signaling pathway that translates changes in periplasmic redox state into elevated biofilm formation through increases in c-di-GMP.

Systematic Review, Quality Assessment, and Synthesis of Guidelines for Emergency Department Care of Transgender and Gender-diverse People: Recommendations for Immediate Action to Improve Care.

Introduction: We conducted this systematic review to identify emergency department (ED) relevant recommendations in current guidelines for care of transgender and gender-diverse (TGD) people internationally. Methods: Using PRISMA criteria, we did a systematic search of Ovid Medline, EMBASE, and CINAHL and a hand search of gray literature for clinical practice guidelines (CPG) or best practice statements (BPS) published until June 31, 2021. Articles were included if they were in English, included medical or paramedical care of TGD populations of any age, in any setting, region or nation, and were national or international in scope. Exclusion criteria included primary research studies, review articles, narrative reviews or otherwise non-CPG or BPS, editorials, or letters to the editor, articles of regional or individual hospital scope, non-medical articles, articles not in English, or if a more recent version of the guideline existed. Recommendations relevant to ED care were identified, recorded, and assessed for quality using the AGREE-II and AGREE-REX criteria. We performed interclass correlation coefficient for interrater reliability. Recommendations were coded for the relevant point of care while in the ED (triage, registration, rooming, investigations, etc.). Results: We screened 1,658 unique articles, and 1,555 were excluded. Of the remaining 103 articles included, seven had recommendations relevant to care in the ED, comprising a total of 10 recommendations. Four guidelines and eight recommendations were of high quality. They included recommendations for testing, prevention, referral, and provision of post-exposure prophylaxis for HIV, and culturally competent care of TGD people. Conclusions: This is the most comprehensive review to date of guidelines and best practices statements offering recommendations for care of ED TGD patients, and several are immediately actionable. There are also many opportunities to build community-led research programs to synthesize and inform a comprehensive dedicated guideline for care of TGD people in emergency settings.

Thiostrepton Hijacks Pyoverdine Receptors To Inhibit Growth of Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a biofilm-forming opportunistic pathogen and is intrinsically resistant to many antibiotics. In a high-throughput screen for molecules that modulate biofilm formation, we discovered that the thiopeptide antibiotic thiostrepton (TS), which is considered to be inactive against Gram-negative bacteria, stimulated P. aeruginosa biofilm formation in a dose-dependent manner. This phenotype is characteristic of exposure to antimicrobial compounds at subinhibitory concentrations, suggesting that TS was active against P. aeruginosa Supporting this observation, TS inhibited the growth of a panel of 96 multidrug-resistant (MDR) P. aeruginosa clinical isolates at low-micromolar concentrations. TS also had activity against Acinetobacter baumannii clinical isolates. The expression of Tsr, a 23S rRNA-modifying methyltransferase from TS producer Streptomyces azureus, in trans conferred TS resistance, confirming that the drug acted via its canonical mode of action, inhibition of ribosome function. The deletion of oligopeptide permease systems used by other peptide antibiotics for uptake failed to confer TS resistance. TS susceptibility was inversely proportional to iron availability, suggesting that TS exploits uptake pathways whose expression is increased under iron starvation. Consistent with this finding, TS activity against P. aeruginosa and A. baumannii was potentiated by the FDA-approved iron chelators deferiprone and deferasirox and by heat-inactivated serum. Screening of P. aeruginosa mutants for TS resistance revealed that it exploits pyoverdine receptors FpvA and FpvB to cross the outer membrane. We show that the biofilm stimulation phenotype can reveal cryptic subinhibitory antibiotic activity, and that TS has activity against select multidrug-resistant Gram-negative pathogens under iron-limited growth conditions, similar to those encountered at sites of infection.