Effects of a healthcare students' prevention intervention for school children on their own substance use: a before-after study.

BACKGROUND: Cognitive dissonance theory and research has suggested that engaging in prevention interventions for other students may be a means of reducing one's own problematic behaviors in order to reduce potential cognitive dissonance. This study assessed the effects of a new mandatory prevention intervention program for healthcare students in France. The aim was to measure the effects of engaging in a prevention program in schools on the usual increase in substance use in student populations. METHODS: Healthcare students were trained in a French university to develop psychosocial competences as a health promotion means (FEPS training) or more specifically to prevent substance use in teenagers (Unplugged program training). The students (n = 314) who accepted to take part in the study from both groups completed questionnaires before their interventions in schools, and at the end of the year, measuring their representations and behaviors regarding psychoactive substances. RESULTS: The results indicated a significant reduction in alcohol consumption in terms of quantity, but no significant reduction in tobacco and marijuana consumption. CONCLUSIONS: This study showed that, contrary to the usual increase in substance use in students as they advance in their year, the students who took part in this study showed reduced self-reported consumption of alcohol after they had performed the prevention intervention in schools regardless of the type of training they had received (general health promotion vs. specific substance use prevention program). Limitations and future perspectives are discussed.

Healthcare students' prevention training in a sanitary service: analysis of health education interventions in schools of the Grenoble academy.

BACKGROUND: The sanitary service is a mandatory prevention training programme for all French healthcare students. Students receive training and then have to design and carry out a prevention intervention with various populations. The aim of this study was to analyse the type of health education interventions carried out in schools by healthcare students from one university in order to describe the topics covered and the methods used. METHOD: The 2021-2022 sanitary service of University Grenoble Alpes involved students in maieutic, medicine, nursing, pharmacy and physiotherapy. The study focused on students who intervened in school contexts. The intervention reports written by the students were read doubly by independent evaluators. Information of interest was collected in a standardised form. RESULTS: Out of the 752 students involved in the prevention training program, 616 (82%) were assigned to 86 schools, mostly primary schools (58%), and wrote 123 reports on their interventions. Each school hosted a median of 6 students from 3 different fields of study. The interventions involved 6853 pupils aged between 3 and 18 years. The students delivered a median of 5 health prevention sessions to each pupil group and spent a median of 25 h (IQR: 19-32) working on the intervention. The themes most frequently addressed were screen use (48%), nutrition (36%), sleep (25%), harassment (20%) and personal hygiene (15%). All students used interactive teaching methods such as workshops, group games or debates that was addressed to pupils' psychosocial (mainly cognitive and social) competences. The themes and tools used differed according to the pupils' grade levels. CONCLUSION: This study showed the feasibility of conducting health education and prevention activities in schools by healthcare students from five professional fields who had received appropriate training. The students were involved and creative, and they were focused on developing pupils' psychosocial competences.

Intrinsic values of procalcitonin in bacterial bloodstream infections in people aged 75 years and over: a retrospective study.

OBJECTIVE: To evaluate PCT measurement in the diagnosis of bloodstream infection (BSI) in hospitalized patients aged 75+. METHOD: Descriptive, retrospective, monocentric study conducted in France, in patients with at least one blood culture and PCT and CRP measurements within the 24 hours before or after blood culture. RESULTS: The mean PCT and CRP values for the 118 (15.2%) positive blood cultures were 18.90 ng/ml [95%CI: 0.007-334.7] and 153.93 mg/l [1-557], respectively. With a threshold of 0.3 ng/ml, PCT measurement had a sensitivity of 84%, a specificity of 53%, a PPV of 24%, and an NPV of 95%, making it possible to rule out BSI in 350 (45.1%) patients (α-risk=5%). CONCLUSION: PCT measurement may eliminate BSI diagnosis more quickly than does blood culture reducing the inadequate and detrimental use of antibiotic therapy. A prospective study is required to validate its usefulness and confirm the cut-off value in geriatric populations.

Student characteristics associated with interpersonal skills in medical consultations.

BACKGROUND: The quality of medical care depends on effective physician-patient communication. Interpersonal skills can be improved through teaching, but the determinants are poorly understood. We therefore assessed the factors associated with the interpersonal skills of medical students during simulated medical consultations. METHODS: We conducted a cross-sectional study of fourth-year medical students participating in simulated consultations with standardized patients. Each video-recorded medical consultation was independently assessed by two raters, using a cross-cultural adaptation of the Four Habits Coding Scheme (4-HCS) into French. We then collected information on demographics and education-related characteristics. The relationship between the overall 4-HCS score and student characteristics was modeled using univariable and multivariable linear regression. RESULTS: Our analytical sample included 165 medical students for analysis. The factors significantly associated with 4-HCS score were gender (ß = - 4.8, p = 0.011) and completion of an international clinical placement (ß = 6.2, p = 0.002) or a research laboratory clerkship (ß = 6.5, p = 0.005). Education-related characteristics, multiple-choice examinations in the first to third preclinical years, and number of medicine or surgery clerkships were not significantly associated with 4-HCS score. CONCLUSIONS: Undergraduate students with higher level of interpersonal skills during video-recorded medical consultations with standardized patients are more likely to be female, to have completed international clinical placement as part of the ERASMUS exchange program or research laboratory clerkship.

Transcriptomic Analysis of E. coli after Exposure to a Sublethal Concentration of Hydrogen Peroxide Revealed a Coordinated Up-Regulation of the Cysteine Biosynthesis Pathway.

Hydrogen peroxide (H2O2) is a key defense component of host-microbe interaction. However, H2O2 concentrations generated by immune cells or epithelia are usually insufficient for bacterial killing and rather modulate bacterial responses. Here, we investigated the impact of sublethal H2O2 concentration on gene expression of E. coli BW25113 after 10 and 60 min of exposure. RNA-seq analysis revealed that approximately 12% of bacterial genes were strongly dysregulated 10 min following exposure to 2.5 mM H2O2. H2O2 exposure led to the activation of a specific antioxidant response and a general stress response. The latter was characterized by a transient down-regulation of genes involved in general metabolism, such as nucleic acid biosynthesis and translation, with a striking and coordinated down-regulation of genes involved in ribosome formation, and a sustained up-regulation of the SOS response. We confirmed the rapid transient and specific response mediated by the transcription factor OxyR leading to up-regulation of antioxidant systems, including the catalase-encoding gene (katG), that rapidly degrade extracellular H2O2 and promote bacterial survival. We documented a strong and transient up-regulation of genes involved in sulfur metabolism and cysteine biosynthesis, which are under the control of the transcription factor CysB. This strong specific transcriptional response to H2O2 exposure had no apparent impact on bacterial survival, but possibly replenishes the stores of oxidized cysteine and glutathione. In summary, our results demonstrate that different stress response mechanisms are activated by H2O2 exposure and highlight the cysteine synthesis as an antioxidant response in E. coli.

Analysis of vitreoretinal surgery activity in metropolitan France in 2016: impact on training capacities.

PURPOSE: The purpose of the study was to describe vitreoretinal surgery activity and vitreoretinal surgeons in private or public practice in metropolitan France over the year 2016 to anticipate surgical training needs. METHODS: Patients aged ≥20 years who had undergone vitreoretinal surgery, alone or combined with cataract surgery were included using the French National Healthcare system database. For surgery performed by ophthalmologists carrying out ≥50 procedures during the year, the incidence per 100 000 of population ≥ 20 years of age, the number and mean age of surgeons and the number of surgeons aged >55 years were calculated. RESULTS: Overall, 57 947 posterior segment surgical procedures were included, 40% in the public sector and 49% in the private sector for private surgeons and/or public centres performing ≥50 procedures/year. The remaining 11% of procedures were from private surgeons and/or public centres performing <50 procedures/year. The analysis included 356 surgeons with a mean age of 41 ± 10 years (39% female) in the public sector and 47 ± 10 years (14% female) in the private sector. The majority of urgent surgery was for retinal detachment (n = 30 290 [52% of total surgical procedures]). Scheduled surgery involved surgery for macular holes and epiretinal membranes (n = 16 454 [28% of total surgical procedures]). Combined vitrectomy-phacoemulsification surgery (n = 10 120) represented 17% of all vitreoretinal surgery. University regions with the fewest surgeons and regions with surgeons >55 years of age were identified, to anticipate the training need for new surgeons. CONCLUSION: This study demonstrated disparities in the geographic distribution of vitreoretinal surgery in France and identified regions that need increased training capacities to ensure a sufficient number of surgeons.

National Health Care data system analysis of glaucoma surgery activity in France in 2016.

PURPOSE: To describe the glaucoma surgery offer in France in 2016. METHODS: We used the French National Health Care System database to identify all medical procedures carried out in 2016. The study investigated the entire population aged 30 years and older that had undergone glaucoma surgery, alone or combined with another surgery. We calculated the incidence of surgeries per 100 000 inhabitants 30 years of age and older performed by ophthalmologists carrying out at least 50 procedures annually, the number of surgeons doing these surgeries, the mean age of these practitioners, and the number of surgeons older than 55 years. RESULTS: In 2016, 16 854 glaucoma surgeries were performed in patients aged 30 years and older, for an incidence of 40.8 per 100 000 inhabitants aged 30 years and older. The most frequent procedure performed was trabeculectomy followed by non-penetrating deep sclerectomy (16.7 and 11.7, respectively, per 100 000 inhabitants 30 years of age and older). Private practice glaucoma surgery accounted for 47% of the activity of surgeons performing at least 50 surgeries per year and 60% of the total surgical activity. Of the private practice ophthalmologists performing at least 50 glaucoma surgery procedures per year, 58.5% were over 55 years of age, and 23.5% of public hospital ophthalmologists were over 55 years of age. CONCLUSIONS: This study demonstrates that surgeons performing glaucoma surgeries are often older. It is necessary to take note of the country's educational capacity to ensure that the number of ophthalmological surgeons remains adapted to demand.

12/111phiA Prophage Domestication Is Associated with Autoaggregation and Increased Ability to Produce Biofilm in Streptococcus agalactiae.

CC17 Streptococcus agalactiae carrying group-A prophages is increasingly responsible for neonatal infections. To investigate the impact of the genetic features of a group-A prophage, we first conducted an in silico analysis of the genome of 12/111phiA, a group-A prophage carried by a strain responsible for a bloodstream infection in a parturient. This revealed a Restriction Modification system, suggesting a prophage maintenance strategy and five ORFs of interest for the host and encoding a type II toxin antitoxin system RelB/YafQ, an endonuclease, an S-adenosylmethionine synthetase MetK, and an StrP-like adhesin. Using the WT strain cured from 12/111phiA and constructing deleted mutants for the ORFs of interest, and their complemented mutants, we demonstrated an impact of prophage features on growth characteristics, cell morphology and biofilm formation. Our findings argue in favor of 12/111phiA domestication by the host and a role of prophage features in cell autoaggregation, glycocalyx and biofilm formation. We suggest that lysogeny may promote GBS adaptation to the acid environment of the vagina, consequently colonizing and infecting neonates.

Influenza A viruses limit NLRP3-NEK7-complex formation and pyroptosis in human macrophages.

Pyroptosis is a fulminant form of macrophage cell death, contributing to release of pro-inflammatory cytokines. In humans, it depends on caspase 1/4-activation of gasdermin D and is characterized by the release of cytoplasmic content. Pathogens apply strategies to avoid or antagonize this host response. We demonstrate here that a small accessory protein (PB1-F2) of contemporary H5N1 and H3N2 influenza A viruses (IAV) curtails fulminant cell death of infected human macrophages. Infection of macrophages with a PB1-F2-deficient mutant of a contemporary IAV resulted in higher levels of caspase-1 activation, cleavage of gasdermin D, and release of LDH and IL-1ß. Mechanistically, PB1-F2 limits transition of NLRP3 from its auto-repressed and closed confirmation into its active state. Consequently, interaction of a recently identified licensing kinase NEK7 with NLRP3 is diminished, which is required to initiate inflammasome assembly.

The Polycyclic Polyprenylated Acylphloroglucinol Antibiotic PPAP 23 Targets the Membrane and Iron Metabolism in Staphylococcus aureus.

Recently, a series of endo-type B polycyclic polyprenylated acylphloroglucinols (PPAP) derivatives with high antimicrobial activities were chemically synthesized. One of the derivatives, PPAP 23, which showed high antimicrobial activity and low cytotoxicity, was chosen for further investigation of its bactericidal profiles and mode of action. PPAP 23 showed a better efficacy in killing methicillin resistant Staphylococcus aureus (MRSA) and decreasing the metabolic activity of 5-day-old biofilm cells than vancomycin. Moreover, S. aureus did not appear to develop resistance against PPAP 23. The antimicrobial mechanism of PPAP 23 was investigated by RNA-seq combined with phenotypic and biochemical approaches. RNA-seq suggested that PPAP 23 signaled iron overload to the bacterial cells because genes involved in iron transport were downregulated and iron storage gene was upregulated by PPAP 23. PPAP 23 affected the membrane integrity but did not induce pore formation; it inhibited bacterial respiration. PPAP 23 preferentially inhibited Fe-S cluster enzymes; it has a mild iron chelating activity and supplementation of exogenous iron attenuated its antimicrobial activity. PPAP 23 was more effective in inhibiting the growth of S. aureus under iron-restricted condition. The crystal structure of a benzylated analog of PPAP 23 showed a highly defined octahedral coordination of three PPAP ligands around a Fe (3+) core. This suggests that PPAPs are generally capable of iron chelation and are able to form defined stable complexes. PPAP 23 was found to induce reactive oxygen species (ROS) and oxidative stress. Fluorescence microscopic analysis showed that PPAP 23 caused an enlargement of the bacterial cells, perturbed the membrane, and dislocated the nucleoid. Taken together, we postulate that PPAP 23 interacts with the cytoplasmic membrane with its hydrophobic pocket and interferes with the iron metabolism to exert its antimicrobial activity in Staphylococcus aureus.

The TIR Homologue Lies near Resistance Genes in Staphylococcus aureus, Coupling Modulation of Virulence and Antimicrobial Susceptibility.

Toll/interleukin-1 receptor (TIR) domains in Toll-like receptors are essential for initiating and propagating the eukaryotic innate immune signaling cascade. Here, we investigate TirS, a Staphylococcus aureus TIR mimic that is part of a novel bacterial invasion mechanism. Its ectopic expression in eukaryotic cells inhibited TLR signaling, downregulating the NF-kB pathway through inhibition of TLR2, TLR4, TLR5, and TLR9. Skin lesions induced by the S. aureus knockout tirS mutant increased in a mouse model compared with wild-type and restored strains even though the tirS-mutant and wild-type strains did not differ in bacterial load. TirS also was associated with lower neutrophil and macrophage activity, confirming a central role in virulence attenuation through local inflammatory responses. TirS invariably localizes within the staphylococcal chromosomal cassettes (SCC) containing the fusC gene for fusidic acid resistance but not always carrying the mecA gene. Of note, sub-inhibitory concentration of fusidic acid increased tirS expression. Epidemiological studies identified no link between this effector and clinical presentation but showed a selective advantage with a SCCmec element with SCC fusC/tirS. Thus, two key traits determining the success and spread of bacterial infections are linked.

Daptomycin Tolerance in the Staphylococcus aureus pitA6 Mutant Is Due to Upregulation of the dlt Operon.

Understanding the mechanisms of how bacteria become tolerant toward antibiotics during clinical therapy is a very important object. In a previous study, we showed that increased daptomycin (DAP) tolerance of Staphylococcus aureus was due to a point mutation in pitA (inorganic phosphate transporter) that led to intracellular accumulation of both inorganic phosphate (Pi) and polyphosphate (polyP). DAP tolerance in the pitA6 mutant differs from classical resistance mechanisms since there is no increase in the MIC. In this follow-up study, we demonstrate that DAP tolerance in the pitA6 mutant is not triggered by the accumulation of polyP. Transcriptome analysis revealed that 234 genes were at least 2.0-fold differentially expressed in the mutant. Particularly, genes involved in protein biosynthesis, carbohydrate and lipid metabolism, and replication and maintenance of DNA were downregulated. However, the most important change was the upregulation of the dlt operon, which is induced by the accumulation of intracellular Pi The GraXRS system, known as an activator of the dlt operon (d-alanylation of teichoic acids) and of the mprF gene (multiple peptide resistance factor), is not involved in DAP tolerance of the pitA6 mutant. In conclusion, DAP tolerance of the pitA6 mutant is due to an upregulation of the dlt operon, triggered directly or indirectly by the accumulation of Pi.

Cerebral imaging in infectious endocarditis: A clinical study.

BACKGROUND: Because neurological failure is the most frequent extra-cardiac complication in Infectious Endocarditis (IE), a brain computerised tomography (CT) scan is usually performed. The benefits of magnetic resonance imaging (MRI) have not been clearly established. This study aims to clarify the prevalence and type of cerebral lesions in IE detected using MRI and to compare them with those detected using CT scans. METHODS: In the Grenoble University Hospital, patients diagnosed with definite or possible endocarditis according to Duke's criteria were screened from 2010-2012. Brain CT and MRI were performed as soon as possible after diagnosis. RESULTS: Of the 62 patients with IE who underwent at least one cerebral imaging within 3 weeks of diagnosis, Streptococcus (29) and Staphylococcus (14) were the main micro-organisms present. Twenty-eight (45%) patients underwent cardiac surgery. Eight (13%) died before discharge. Twenty (32%) had neurological symptoms. A brain CT-scan was performed on 53 (85%) patients and a MRI was performed on 43 (69%) patients. CT was pathological in 26 (49%) patients, whereas 32 (74%) MRI demonstrated abnormalities. The MRI lesions were classified as follows: ischaemia (48%), microbleeds (34%), haemorrhages (16%), abscesses (9%) and microbial aneurysms (4%). Of the 37 patients who underwent both MRI and CT examinations, ischaemia (48% vs 35%) and microbleeds (34%) demonstrated the difference between the two imaging methods. CONCLUSION: Through the early diagnosis of cerebral damage, even in asymptomatic cases, MRI may have a role in the IE management, influence any surgical decision and assist in prognosis assessment.

Antibacterial efficacy of accelerated photoactivated chromophore for keratitis-corneal collagen cross-linking (PACK-CXL).

PURPOSE: To investigate whether optimized photoactivated chromophore for keratitis-corneal collagen cross-linking (PACK-CXL) treatment settings allow accelerating treatment while maintaining antibacterial efficacy. METHODS: Staphylococcus aureus and Pseudomonas aeruginosa strains were irradiated with ultraviolet-A light of equal fluence but different intensity settings (18 mW/cm² for 5 minutes and 36 mW/cm² for 2.5 minutes). The killing rate was determined by comparing the number of colony-forming units between cross-linked specimens and non-irradiated controls. The potential additional effect of 0.001% benzalkonium chloride was also investigated. RESULTS: The killing rates for Staphylococcus aureus were 92.5% ± 5.5% (5 minutes at 18 mW/cm²) and 94.4% ± 2.9% (2.5 minutes at 36 mW/cm²). For Pseudomonas aeruginosa, the killing rates were 93.2% ± 8.3% (5 minutes at 18 mW/cm²) and 92.9% ± 5.0% (2.5 minutes at 36 mW/cm²). The presence of benzalkonium chloride in the riboflavin solution did not increase the killing rate significantly. CONCLUSIONS: The antibacterial efficacy of PACK-CXL follows the Bunsen-Roscoe law of reciprocity and can be maintained even when the irradiation intensity is considerably increased. These optimized settings may allow a shortened treatment time in the future for PACK-CXL and thus help facilitate the transition from the operating room to the slit lamp for treatment.

Microbiome of prebiotic-treated mice reveals novel targets involved in host response during obesity.

The gut microbiota is involved in metabolic and immune disorders associated with obesity and type 2 diabetes. We previously demonstrated that prebiotic treatment may significantly improve host health by modulating bacterial species related to the improvement of gut endocrine, barrier and immune functions. An analysis of the gut metagenome is needed to determine which bacterial functions and taxa are responsible for beneficial microbiota-host interactions upon nutritional intervention. We subjected mice to prebiotic (Pre) treatment under physiological (control diet: CT) and pathological conditions (high-fat diet: HFD) for 8 weeks and investigated the production of intestinal antimicrobial peptides and the gut microbiome. HFD feeding significantly decreased the expression of regenerating islet-derived 3-gamma (Reg3g) and phospholipase A2 group-II (PLA2g2) in the jejunum. Prebiotic treatment increased Reg3g expression (by ∼50-fold) and improved intestinal homeostasis as suggested by the increase in the expression of intectin, a key protein involved in intestinal epithelial cell turnover. Deep metagenomic sequencing analysis revealed that HFD and prebiotic treatment significantly affected the gut microbiome at different taxonomic levels. Functional analyses based on the occurrence of clusters of orthologous groups (COGs) of proteins also revealed distinct profiles for the HFD, Pre, HFD-Pre and CT groups. Finally, the gut microbiota modulations induced by prebiotics counteracted HFD-induced inflammation and related metabolic disorders. Thus, we identified novel putative taxa and metabolic functions that may contribute to the development of or protection against the metabolic alterations observed during HFD feeding and HFD-Pre feeding.

Improving quality of care and patient safety through morbidity and mortality conferences.

The objective was to evaluate the analysis of adverse events and the decisions for quality improvement decided during morbidity and mortality conferences (MMCs). We conducted a prospective observational study of MMCs conducted in a teaching hospital between November 2007 and May 2008. Two observers attended the conferences and collected data on the structure of MMCs, the discussion between attendees, and the decisions or actions for quality improvement. Twenty-four MMCs were studied including 146 cases. A majority of the senior physicians present (87.7%) took part in debating the cases; the participation of residents was lower (32.6%) and varied between departments (p < .001). Few paramedical professionals and other attendees participated in the debate. Shortcomings were sought in 91% of cases, but a structured method was used in less than 10% of cases. An analysis of underlying factors contributing to these shortcomings was observed in 75% of cases, with 4% considered structured and thorough. Eighty-five decisions or actions to improve quality of care or patient safety were listed, with 28 of them (33%) planned for implementation. Discussion of adverse events appears to lack a structured method and although a large number of decisions for quality improvement were declared, fewer actions were planned with a timeline.

Experience feedback committee in emergency medicine: a tool for security management.

OBJECTIVE: Emergency departments are high-risk structures. The objective was to analyse the functioning of an experience feedback committee (EFC), a security management tool for the analysis of incidents in a medical department. METHODS: We conducted a descriptive study based on the analysis of the written documents produced by the EFC between November 2009 and May 2012. We performed a double analysis of all incident reports, meeting minutes and analysis reports. RESULTS: During the study period, there were 22 meetings attended by 15 professionals. 471 reported incidents were transmitted to the EFC. Most of them (95%) had no consequence for the patients. Only one reported incident led to the patient's death. 12 incidents were analysed thoroughly and the committee decided to set up 14 corrective actions, including eight guideline writing actions, two staff trainings, two resource materials provisions and two organisational changes. CONCLUSIONS: The staff took part actively in the EFC. Following the analysis of incidents, the EFC was able to set up actions at the departmental level. Thus, an EFC seems to be an appropriate security management tool for an emergency department.

Importance of bacillithiol in the oxidative stress response of Staphylococcus aureus.

In Staphylococcus aureus, the low-molecular-weight thiol called bacillithiol (BSH), together with cognate S-transferases, is believed to be the counterpart to the glutathione system of other organisms. To explore the physiological role of BSH in S. aureus, we constructed mutants with the deletion of bshA (sa1291), which encodes the glycosyltransferase that catalyzes the first step of BSH biosynthesis, and fosB (sa2124), which encodes a BSH-S-transferase that confers fosfomycin resistance, in several S. aureus strains, including clinical isolates. Mutation of fosB or bshA caused a 16- to 60-fold reduction in fosfomycin resistance in these S. aureus strains. High-pressure liquid chromatography analysis, which quantified thiol extracts, revealed some variability in the amounts of BSH present across S. aureus strains. Deletion of fosB led to a decrease in BSH levels. The fosB and bshA mutants of strain COL and a USA300 isolate, upon further characterization, were found to be sensitive to H2O2 and exhibited decreased NADPH levels compared with those in the isogenic parents. Microarray analyses of COL and the isogenic bshA mutant revealed increased expression of genes involved in staphyloxanthin synthesis in the bshA mutant relative to that in COL under thiol stress conditions. However, the bshA mutant of COL demonstrated decreased survival compared to that of the parent in human whole-blood survival assays; likewise, the naturally BSH-deficient strain SH1000 survived less well than its BSH-producing isogenic counterpart. Thus, the survival of S. aureus under oxidative stress is facilitated by BSH, possibly via a FosB-mediated mechanism, independently of its capability to produce staphyloxanthin.

Impact of fluorescein on the antimicrobial efficacy of photoactivated riboflavin in corneal collagen cross-linking.

PURPOSE: To investigate the effect of fluorescein on the antimicrobial efficacy of photoactivated riboflavin in corneal collagen cross-linking (CXL) in vitro. METHODS: The ultraviolet light-A (UVA) absorption by fluorescein and riboflavin in different concentrations was analyzed with a spectrophotometer. The killing rate of Staphylococcus aureus strains after CXL with UV-A irradiation using different solutions containing riboflavin and/or fluorescein, was evaluated in vitro. RESULTS: Fluorescein absorbed UV-A to a significant extent, which augmented with increasing concentration. Moreover, addition of fluorescein to the riboflavin solution contributed to a significant reduction of the killing rate of S. aureus strains after 30 minutes of UV-A irradiation in vitro with a killing rate of 85%, whereas it was 47% in the presence of 2% fluorescein (P = .0247). CONCLUSIONS: The results indicate that fluorescein competes with riboflavin for the absorption of UV-A during CXL and reduces the antimicrobial effect of the procedure. The authors recommend that physicians treating infectious ulcerative keratitis by CXL should not stain the cornea with fluorescein for visualization of the corneal ulceration prior to CXL

The CshA DEAD-box RNA helicase is important for quorum sensing control in Staphylococcus aureus.

DEAD-box RNA helicases are present in almost all living organisms and participate in various processes of RNA metabolism. Bacterial proteins of this large family were shown to be required for translation initiation, ribosome biogenesis and RNA decay. The latter is primordial for rapid adaptation to changing environmental conditions. In particular, the RhlB RNA helicase from E. coli was shown to assist the bacterial degradosome machinery. Recently, the CshA DEAD-box proteins from Bacillus subtilis and Staphylococcus aureus were shown to interact with proteins that are believed to form the degradosome. S. aureus can cause life-threatening disease, with particular concern focusing on biofilm formation on catheters and prosthetic devices, since in this form the bacteria are almost impossible to eradicate both by the immune system and antibiotic treatment. This persistent state relies on the expression of surface encoded proteins that allow attachment to various surfaces, and contrasts with the dispersal mode of growth that relies on the secretion of proteins such as hemolysins and proteases. The switch between these two states is mainly mediated by the Staphylococcal cell density sensing system encoded by agr. We show that inactivation of the cshA DEAD-box gene results in dysregulation of biofilm formation and hemolysis through modulation of agr mRNA stability. Importantly, inactivation of the agrA gene in the cshA mutant background reverses the defect, indicating that cshA is genetically upstream of agr and that a delicate balance of agr mRNA abundance mediated through stability control by CshA is critical for proper expression of virulence factors.