Geometric control by active mechanics of epithelial gap closure

Epithelial wound healing is one of the most important biological processes occurring during the lifetime of an organism. It is a self-repair mechanism closing wounds or gaps within tissues to restore their functional integrity. In this work we derive a new diffuse interface approach for modelling the gap closure by means of a variational principle in the framework of non-equilibrium thermodynamics. We investigate the interplay between the crawling with lamellipodia protrusions and the supracellular tension exerted by the actomyosin cable on the closure dynamics. These active features are modeled as Korteweg forces into a generalised chemical potential. From an asymptotic analysis, we derive a pressure jump across the gap edge in the sharp interface limit. Moreover, the chemical potential diffuses as a Mullins-Sekerka system, and its interfacial value is given by a Gibbs-Thompson relation for its local potential driven by the curvature-dependent purse-string tension. The finite element simulations show an excellent quantitative agreement between the closure dynamics and the morphology of the edge with respect to existing biological experiments. The resulting force patterns are also in good qualitative agreement with existing traction force microscopy measurements. Our results shed light on the geometrical control of the gap closure dynamics resulting from the active forces that are chemically activated around the gap edge.

The mobilome of Lactobacillus crispatus M247 includes two novel genetic elements: Tn7088 coding for a putative bacteriocin and the siphovirus prophage ΦM247

Lactobacillus crispatus is a member of the vaginal and gastrointestinal human microbiota. Here we determined the complete genome sequence of the probiotic strain M247 combining Nanopore and Illumina technologies. The M247 genome is organized in one circular chromosome of 2 336 109 bp, with a GC content of 37.04 % and 2303 ORFs, of which 1962 could be annotated. Analysis of the M247 mobilome, which accounts for 14 % of the whole genome, revealed the presence of: (i) Tn7088, a novel 14 105 bp long integrative and mobilizable element (IME) containing 16 ORFs; (ii) ΦM247, a novel 42 510 bp long siphovirus prophage containing 52 ORFs; (iii) three clustered regularly interspaced short palindromic repeats (CRISPRs); and (iv) 226 insertion sequences (ISs) belonging to 14 different families. Tn7088 has a modular organization including a mobilization module encoding FtsK homologous proteins and a relaxase, an integration/excision module coding for an integrase and an excisionase, and an adaptation module coding for a class I bacteriocin and homologous to the listeriolysin S (lls) locus of Listeria monocytogenes. Genome-wide homology search analysis showed the presence of Tn7088-like elements in 12 out of 23 L. crispatus complete public genomes. Mobilization and integration/excision modules are essentially conserved, while the adaptation module is variable since it is the target site for the integration of different ISs. Prophage ΦM247 contains genes for phage structural proteins, DNA replication and packaging, lysogenic and lytic cycles. ΦM247-like prophages are present in seven L. crispatus complete genomes, with sequence variability mainly due to the integration of ISs. PCR and sequencing showed that the Tn7088 IME excises from the M247 chromosome producing a circular form at a concentration of 4.32×10-5 copies per chromosome, and reconstitution of the Tn7088 chromosomal target site occurred at 6.65×10-4 copies per chromosome. The ΦM247 prophage produces an excised form and a reconstituted target site at a level of 3.90×10-5 and 2.48×10-5 copies per chromosome, respectively. This study identified two novel genetic elements in L. crispatus. Tn7088 represents the first example of an IME carrying a biosynthetic gene cluster for a class I bacteriocin in L. crispatus.

Vaginal colonization of women after oral administration of Lactobacillus crispatus strain NTCVAG04 from the human microbiota

BACKGROUND

The genomic approach has deeply changed the microbiology perspective, mainly concerning the microbioma identification. In this regard, some microbes colonize the healthy vagina. Vaginitis is a common gynecological ailment and includes bacterial vaginosis (BV), usually caused by local dysbiosis, such as a microbiota imbalance. Lactobacilli are the most prevalent bacteria colonizing the healthy vagina, so guaranteeing local eubiosis. In particular, vaginal colonization by L. crispatus is associated with low susceptibility to BV. Therefore, probiotics, such as life bacteria providing health advantages, are a current strategy in the prevention or treatment of vaginitis, including BV. However, there is a low level of evidence that probiotics after ingestion could really colonize the vagina. In particular, no study evidenced that L. crispatus after ingestion can colonize vagina. Therefore, the current study explored the capacity of Biovaginil® (NTC, Milan, Italy) dietary supplement containing Lactobacillus crispatus NTCVAG04 and vitamin A to colonize the gut and vagina in women with a history of vaginitis/vaginosis.

METHODS

Twenty fertile females (mean age 34.0 years) were enrolled in the study. Rectal and vaginal swabs were collected at baseline and after the first and second cycle of Biovaginil®. Each cycle lasted 14 days within two consecutive menstrual periods.

RESULTS

Seven women were excluded from the analysis because the samples were technically not evaluable. One woman dropped out because of mild adverse event. At the end of the study, nine women (75%) had positive rectal swab for L. crispatus NTCVAG04, and 8 of them also had positive vaginal swab.

CONCLUSIONS

The current study provided the first evidence that L. crispatus NTCVAG04, administered by two Biovaginil® courses, colonized both the gut and vagina. Moreover, the L. crispatus NTCVAG04 strain could be considered the archetype of a new class of oral probiotics that actively colonize the vagina, and that could be called "colpobiotics."

The mef(A)/msr(D)-carrying streptococcal prophage Φ1207.3 encodes an SOS-like system, induced by UV-C light, responsible for increased survival and increased mutation rate

Bacterial SOS response is an inducible system of DNA repair and mutagenesis. Streptococci lack a canonical SOS response, but an SOS-like response was reported in some species. The mef(A)-msr(D)-carrying prophage Ф1207.3 of Streptococcus pyogenes contains a region, spanning orf6 to orf11, showing homology to characterized streptococcal SOS-like cassettes. Genome-wide homology search showed the presence of the whole Φ1207.3 SOS-like cassette in three S. pyogenes prophages, while parts of it were found in other bacterial species. To investigate whether this cassette confers an SOS-mutagenesis phenotype, we constructed Streptococcus pneumoniae R6 isogenic derivative strains: (i) FR172, streptomycin resistant, (ii) FR173, carrying Φ1207.3, and (iii) FR174, carrying a recombinant Φ1207.3, where the SOS-like cassette was deleted. These strains were used in survival and mutation rate assays using a UV-C LED instrument, for which we designed and 3D-printed a customized equipment, constituted of an instrument support and swappable-autoclavable mini-plates and lids. Upon exposure to UV fluences ranging from 0 to 6,400 J/m2 at four different wavelengths, 255, 265, 275, and 285 nm, we found that the presence of Φ1207.3 SOS-like cassette increases bacterial survival up to 34-fold. Mutation rate was determined by measuring rifampicin resistance acquisition upon exposure to UV fluence of 50 J/m2 at the four wavelengths by fluctuation test. The presence of Φ1207.3 SOS-like cassette resulted in a significant increase in the mutation rate (up to 18-fold) at every wavelength. In conclusion, we demonstrated that Φ1207.3 carries a functional SOS-like cassette responsible for an increased survival and increased mutation rate in S. pneumoniae. IMPORTANCE Bacterial mutation rate is generally low, but stress conditions and DNA damage can induce stress response systems, which allow for improved survival and continuous replication. The SOS response is a DNA repair mechanism activated by some bacteria in response to stressful conditions, which leads to a temporary hypermutable phenotype and is usually absent in streptococcal genomes. Here, using a reproducible and controlled UV irradiation system, we demonstrated that the SOS-like gene cassette of prophage Φ1207.3 is functional, responsible for a temporary hypermutable phenotype, and enhances bacterial survival to UV irradiation. Prophage Φ1207.3 also carries erythromycin resistance genes and can lysogenize different pathogenic bacteria, constituting an example of a mobile genetic element which can confer multiple phenotypes to its host.

The Mobilome-Enriched Genome of the Competence-Deficient Streptococcus pneumoniae BM6001, the Original Host of Integrative Conjugative Element Tn5253, Is Phylogenetically Distinct from Historical Pneumococcal Genomes

Streptococcus pneumoniae is an important human pathogen causing both mild and severe diseases. In this work, we determined the complete genome sequence of the S. pneumoniae clinical isolate BM6001, which is the original host of the ICE Tn5253. The BM6001 genome is organized in one circular chromosome of 2,293,748 base pairs (bp) in length, with an average GC content of 39.54%; the genome harbors a type 19F capsule locus, two tandem copies of pspC, the comC1-comD1 alleles and the type I restriction modification system SpnIII. The BM6001 mobilome accounts for 15.54% (356,521 bp) of the whole genome and includes (i) the ICE Tn5253 composite; (ii) the novel IME Tn7089; (iii) the novel transposon Tn7090; (iv) 3 prophages and 2 satellite prophages; (v) 5 genomic islands (GIs); (vi) 72 insertion sequences (ISs); (vii) 69 RUPs; (viii) 153 BOX elements; and (ix) 31 SPRITEs. All MGEs, except for the GIs, produce excised circular forms and attB site restoration. Tn7089 is 9089 bp long and contains 11 ORFs, of which 6 were annotated and code for three functions: integration/excision, mobilization and adaptation. Tn7090 is 9053 bp in size, flanked by two copies of ISSpn7, and contains seven ORFs organized as a single transcriptional unit, with genes encoding for proteins likely involved in the uptake and binding of Mg²⁺ cations in the adhesion to host cells and intracellular survival. BM6001 GIs, except for GI-BM6001.4, are variants of the pneumococcal TIGR4 RD5 region of diversity, pathogenicity island PPI1, R6 Cluster 4 and PTS island. Overall, prophages and satellite prophages contain genes predicted to encode proteins involved in DNA replication and lysogeny, in addition to genes encoding phage structural proteins and lytic enzymes carried only by prophages. ΦBM6001.3 has a mosaic structure that shares sequences with prophages IPP69 and MM1 and disrupts the competent comGC/cglC gene after chromosomal integration. Treatment with mitomycin C results in a 10-fold increase in the frequency of ΦBM6001.3 excised forms and comGC/cglC coding sequence restoration but does not restore competence for genetic transformation. In addition, phylogenetic analysis showed that BM6001 clusters in a small lineage with five other historical strains, but it is distantly related to the lineage due to its unique mobilome, suggesting that BM6001 has progressively accumulated many MGEs while losing competence for genetic transformation.

The presence of Enterococcus faecalis in saliva as a risk factor for endodontic infection

Aim

The aim of the present study was to investigate and correlate the prevalence of Enterococcus faecalis in saliva and in root canals with different pulpal and periapical conditions.

Methodology

Sixty-seven patients were divided into five groups based on pulpal and periapical tissue status: healthy vital teeth (HVT, n=7), healthy treated teeth without lesion (HTT, n=9), irreversible pulpitis (IP, n=13), necrosis (N, n=18), and post-treatment apical periodontitis (PTAP, n=20). Saliva, rubber dam, sterility control and pre-treatment root canal samples were collected and microbiologically processed by culture method. The phylogenetic relationship of E. faecalis isolates collected from root canals and saliva were investigated by whole genome sequencing. Fisher’s exact test was used to correlate the presence of E. faecalis in root canals or saliva with clinical and/or radiographic findings. Linear/logistic regression analyses were performed to establish the relationship between the presence of E. faecalis in root canals, saliva, and the status of periapical tissues.

Results

E. faecalis was found in 18 root canal and saliva samples. E. faecalis root canal isolates were recovered with the highest frequency from post-treatment apical periodontitis. The occurrence of E. faecalis in saliva was strongly associated with its detection in the root canals (P < 0.001). The pretreatment presence of E. faecalis in root canals was associated with significantly higher odds of having periapical lesions (OR=11.03; 95% CI, 1.27-95.70; p < 0.05). Saliva and root canal isolates from the same patient were highly correlated at the phylogenetic level (Jaccard index >0.95).

Conclusion

This pilot study confirms the role of E. faecalis in developing peri-radicular lesions in secondary endodontic infections and suggests that saliva could be the main source of infection. Further studies are needed to investigate the exact origin of this bacteria and its true role in the pathogenesis of secondary/persistent endodontic infections.

Streptococcus pyogenes Φ1207.3 Is a Temperate Bacteriophage Carrying the Macrolide Resistance Gene Pair mef(A)-msr(D) and Capable of Lysogenizing Different Streptococci

Streptococcus pyogenes prophage Φ1207.3 (formerly Tn1207.3) carries the mef(A)-msr(D) resistance genes, responsible for type M macrolide resistance. To investigate if Φ1207.3 is a functional bacteriophage, we transferred the element from the original S. pyogenes host in a prophage-free and competence-deficient S. pneumoniae strain. Pneumococcal cultures of the Φ1207.3-carrying lysogen were treated with mitomycin C to assess if Φ1207.3 enters the lytic cycle. Mitomycin C induced a limited phage burst and a growth impairment, resulting in early entrance into the stationary phase. To determine if Φ1207.3 is able to produce mature phage particles, we prepared concentrated supernatants recovered from a mitomycin C-induced pneumococcal culture by sequential centrifugation and ultracentrifugation steps. Negative-staining transmission electron microscopy (TEM) of supernatants revealed the presence of phage particles with an icosahedral, electron-dense capsid and a long, noncontractile tail, typical of a siphovirus. Quantification of Φ1207.3 was performed by quantitative PCR (qPCR) and semiquantitatively by TEM. PCR quantified 3.34 × 104 and 6.06 × 104 excised forms of phage genome per milliliter of supernatant obtained from the untreated and mitomycin C-treated cultures, respectively. By TEM, we estimated 3.02 × 103 and 7.68 × 103 phage particles per milliliter of supernatant. The phage preparations of Φ1207.3 infected and lysogenized pneumococcal recipient strains at a frequency of 7.5 × 10-6 lysogens/recipient but did not show sufficient lytic activity to form plaques. Phage lysogenization efficiently occurred after 30 min of contact of the phages with the recipient cells and required a minimum of 103 phage particles. IMPORTANCE Bacteriophages play an important role in bacterial physiology and genome evolution. The widespread use of genome sequencing revealed that bacterial genomes can contain several different integrated temperate bacteriophages, which can constitute up to 20% of the genome. Most of these bacteriophages are only predicted in silico and are never shown to be functional. In fact, it is often difficult to induce the lytic cycle of temperate bacteriophages. In this work, we show that Φ1207.3, a peculiar bacteriophage originally from Streptococcus pyogenes, which can lysogenize different streptococci and carries the macrolide resistance mef(A)-msr(D) gene pair, is capable of producing mature virions, but only at a low level, while not being able to produce plaques. This temperate phage is probably a partially functional phage, which seems to have lost lytic characteristics to specialize in lysogenization. While we are not used to conceiving phages separately from lysis, this behavior could actually be more frequent than expected.

OC-078 LAP-T LAPAROSCOPIC GAS-LESS TECHNIQUE FOR THE REPAIR OF RECTUS MUSCLES DIASTASIS AND HERNIA IN ATHLETES

Background/Aim

Diastasis of Rectus Abdominis Muscles (DRAM) in athletes is typically associated with muscle and fascial tearing and fracture and umbilical/epigastric hernias. Parietal damage is generally located on midline, subjected to continuous efforts and overload. Contrarily to repair of DRAM consequent to pregnancy or obesity, in athletes, the trigger of injury will persist after repair. LAP-T Technique aims at Mini-Invasive restoration of anatomy and physiologic functionality through laparoscopic tailored suture&mesh repair, allowing return to full sport activity.

Methods

96 cases from January 2010 to May 2021, minimum follow-up of 12 months. Elected patients: athletes, under 60 years old, BMI < 30, ASA1 – ASA2, with maximum IRD 10cm and associated AWR. Rectus muscles are re-approximated from xiphoid to pubis with tailored sutures, and hernia defect repaired, using laparoscopic running self-locking barbed sutures. Entire procedure is performed in gas-less laparoscopy (3mmHg). Considering persistence of triggering cause after repair in athletes, the repair is consolidated placing an intra-peritoneal mesh. 10–15 days from surgery, patients start following a tailored rehabilitation program up to full resumption of sport activity.

Results

In all patients, AW anatomy and physiological functionality were successfully restored, any hernia repaired, with the restitution ad integrum of the AW; no higher pain related to the continuous suturing has been reported compared to bridge IPOM laparoscopic repair, while allowing for physiologic outcome and stronger repair. No intra operative bleeding, no seroma formation, chronic pain, nor mesh infection. All athletes retrieved full sport activity at pre-hernia and DRAM level. 98% follow up at 12 months, 91% at 24, with no recurrences observed.

Conclusions

LAP-T technique proved to be feasible technique for Athletes, allowing for sound and anatomic reconstruction of DRAM, associated hernias, and musculo-fascial tearing, with reduced trauma, fast recovery and full resumption of sport activity.

Comprehensive Study of Antiretroviral Drug Permeability at the Cervicovaginal Mucosa via an In Vitro Model

Modulation of drug transporter activity at mucosal sites of HIV-1 transmission may be exploited to optimize retention of therapeutic antiretroviral drug concentrations at target submucosal CD4+ T cells. Previously, we showed that darunavir was a substrate for the P-glycoprotein efflux drug transporter in colorectal mucosa. Equivalent studies in the cervicovaginal epithelium have not been reported. Here, we describe the development of a physiologically relevant model to investigate the permeability of antiretroviral drugs across the vaginal epithelium. Barrier properties of the HEC-1A human endometrial epithelial cell line were determined, in a dual chamber model, by measurement of transepithelial electrical resistance, immunofluorescent staining of tight junctions and bi-directional paracellular permeability of mannitol. We then applied this model to investigate the permeability of tenofovir, darunavir and dapivirine. Efflux ratios indicated that the permeability of each drug was transporter-independent in this model. Reduction of pH to physiological levels in the apical compartment increased absorptive transfer of darunavir, an effect that was reversed by inhibition of MRP efflux transport via MK571. Thus, low pH may increase the transfer of darunavir across the epithelial barrier via increased MRP transporter activity. In a previous in vivo study in the macaque model, we demonstrated increased MRP2 expression following intravaginal stimulation with darunavir which may further increase drug uptake. Stimulation with inflammatory modulators had no effect on drug permeability across HEC-1A barrier epithelium but, in the VK2/E6E7 vaginal cell line, increased expression of both efflux and uptake drug transporters which may influence darunavir disposition.

Activity of N-Acetylcysteine Alone and in Combination with Colistin against Pseudomonas aeruginosa Biofilms and Transcriptomic Response to N-Acetylcysteine Exposure

Chronic colonization by Pseudomonas aeruginosa is critical in cystic fibrosis (CF) and other chronic lung diseases, contributing to disease progression. Biofilm growth and a propensity to evolve multidrug resistance phenotypes drastically limit the available therapeutic options. In this perspective, there has been growing interest in evaluating combination therapies, especially for drugs that can be administered by nebulization, which allows high drug concentrations to be reached at the site of infections while limiting systemic toxicity. Here, we investigated the potential antibiofilm activity of N-acetylcysteine (NAC) alone and in combination with colistin against a panel of P. aeruginosa strains (most of which are from CF patients) and the transcriptomic response of a P. aeruginosa CF strain to NAC exposure. NAC alone (8,000 mg/L) showed a limited and strain-dependent antibiofilm activity. Nonetheless, a relevant antibiofilm synergism of NAC-colistin combinations (NAC at 8,000 mg/L plus colistin at 2 to 32 mg/L) was observed with all strains. Synergism was also confirmed with the artificial sputum medium model. RNA sequencing of NAC-exposed planktonic cultures revealed that NAC (8,000 mg/L) mainly induced (i) a Zn2+ starvation response (known to induce attenuation of P. aeruginosa virulence), (ii) downregulation of genes of the denitrification apparatus, and (iii) downregulation of flagellar biosynthesis pathway. NAC-mediated inhibition of P. aeruginosa denitrification pathway and flagellum-mediated motility were confirmed experimentally. These findings suggested that NAC-colistin combinations might contribute to the management of biofilm-associated P. aeruginosa lung infections. NAC might also have a role in reducing P. aeruginosa virulence, which could be relevant in the very early stages of lung colonization. IMPORTANCE Pseudomonas aeruginosa biofilm-related chronic lung colonization contributes to cystic fibrosis (CF) disease progression. Colistin is often a last-resort antibiotic for the treatment of such P. aeruginosa infections, and it has been increasingly used in CF, especially by nebulization. N-acetylcysteine (NAC) is a mucolytic agent with antioxidant activity, commonly administered with antibiotics for the treatment of lower respiratory tract infections. Here, we show that NAC potentiated colistin activity against in vitro biofilms models of P. aeruginosa strains, with both drugs tested at the high concentrations achievable after nebulization. In addition, we report the first transcriptomic data on the P. aeruginosa response to NAC exposure.

Immune Memory After Respiratory Infection With Streptococcus pneumoniae Is Revealed by in vitro Stimulation of Murine Splenocytes With Inactivated Pneumococcal Whole Cells: Evidence of Early Recall Responses by Transcriptomic Analysis

The in vitro stimulation of immune system cells with live or killed bacteria is essential for understanding the host response to pathogens. In the present study, we propose a model combining transcriptomic and cytokine assays on murine splenocytes to describe the immune recall in the days following pneumococcal lung infection. Mice were sacrificed at days 1, 2, 4, and 7 after Streptococcus pneumoniae (TIGR4 serotype 4) intranasal infection and splenocytes were cultured in the presence or absence of the same inactivated bacterial strain to access the transcriptomic and cytokine profiles. The stimulation of splenocytes from infected mice led to a higher number of differentially expressed genes than the infection or stimulation alone, resulting in the enrichment of 40 unique blood transcription modules, including many pathways related to adaptive immunity and cytokines. Together with transcriptomic data, cytokines levels suggested the presence of a recall immune response promoting both innate and adaptive immunity, stronger from the fourth day after infection. Dimensionality reduction and feature selection identified key variables of this recall response and the genes associated with the increase in cytokine concentrations. This model could study the immune responses involved in pneumococcal infection and possibly monitor vaccine immune response and experimental therapies efficacy in future studies.

The Föppl-von Kármán equations of elastic plates with initial stress

Initially, stressed plates are widely used in modern fabrication techniques, such as additive manufacturing and UV lithography, for their tunable morphology by application of external stimuli. In this work, we propose a formal asymptotic derivation of the Föppl-von Kármán equations for an elastic plate with initial stresses, using the constitutive theory of nonlinear elastic solids with initial stresses under the assumptions of incompressibility and material isotropy. Compared to existing works, our approach allows us to determine the morphological transitions of the elastic plate without prescribing the underlying target metric of the unstressed state of the elastic body. We explicitly solve the derived FvK equations in some physical problems of engineering interest, discussing how the initial stress distribution drives the emergence of spontaneous curvatures within the deformed plate. The proposed mathematical framework can be used to tailor shape on demand, with applications in several engineering fields ranging from soft robotics to four-dimensional printing.

DNA isolation methods for Nanopore sequencing of the Streptococcus mitis genome

Streptococcus mitis is a Gram-positive bacterium, member of the oral commensal microbiota, which can occasionally be the etiologic agent of diseases such as infective endocarditis, bacteraemia and septicaemia. The highly recombinogenic and repetitive nature of the S. mitis genome impairs the assembly of a complete genome relying only on short sequencing reads. Oxford Nanopore sequencing can overcome this limitation by generating long reads, enabling the resolution of genomic repeated regions and the assembly of a complete genome sequence. Since the output of a Nanopore sequencing run is strongly influenced by genomic DNA quality and molecular weight, the DNA isolation is the crucial step for an optimal sequencing run. In the present work, we have set up and compared three DNA isolation methods on two S. mitis strains, evaluating their capability of preserving genomic DNA integrity and purity. Sequencing of DNA isolated with a mechanical lysis-based method, despite being cheaper and quicker, did not generate ultra-long reads (maximum read length of 59516 bases) and did not allow the assembly of a circular complete genome. Two methods based on enzymatic lysis of the bacterial cell wall, followed by either (i) a modified CTAB DNA isolation procedure, or (ii) a DNA purification after osmotic lysis of the protoplasts allowed the sequencing of ultra-long reads up to 107294 and 181199 bases in length, respectively. The reconstruction of a circular complete genome was possible sequencing DNAs isolated using the enzymatic lysis-based methods.

Predicted transmembrane proteins with homology to Mef(A) are not responsible for complementing mef(A) deletion in the mef(A)-msr(D) macrolide efflux system in Streptococcus pneumoniae

Objectives

In streptococci, the type M resistance to macrolides is due to the mef(A)–msr(D) efflux transport system of the ATP-Binding cassette (ABC) superfamily, where it is proposed that mef(A) codes for the transmembrane channel and msr(D) for the two ATP-binding domains. Phage ϕ1207.3 of Streptococcus pyogenes, carrying the mef(A)–msr(D) gene pair, is able to transfer the macrolide efflux phenotype to Streptococcus pneumoniae. Deletion of mef(A) in pneumococcal ϕ1207.3-carrying strains did not affect erythromycin efflux. In order to identify candidate genes likely involved in complementation of mef(A) deletion, the Mef(A) amino acid sequence was used as probe for database searching.

Results

In silico analysis identified 3 putative candidates in the S. pneumoniae R6 genome, namely spr0971, spr1023 and spr1932. Isogenic deletion mutants of each candidate gene were constructed and used in erythromycin sensitivity assays to investigate their contribution to mef(A) complementation. Since no change in erythromycin sensitivity was observed compared to the parental strain, we produced double and triple mutants to assess the potential synergic activity of the selected genes. Also these mutants did not complement the mef(A) function.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05856-6.

Chromosomal integration of Tn5253 occurs downstream of a conserved 11-bp sequence of the rbgA gene in Streptococcus pneumoniae and in all the other known hosts of this integrative conjugative element (ICE)

Background

Tn5253, a composite Integrative Conjugative Element (ICE) of Streptococcus pneumoniae carrying tet(M) and cat resistance determinants, was found to (i) integrate at specific 83-bp integration site (attB), (ii) produce circular forms joined by a 84-bp sequence (attTn), and (iii) restore the chromosomal integration site. The purpose of this study is to functionally characterize the attB in S. pneumoniae strains with different genetic backgrounds and in other bacterial species, and to investigate the presence of Tn5253 attB site into bacterial genomes.

Results

Analysis of representative Tn5253-carryng transconjugants obtained in S. pneumoniae strains with different genetic backgrounds and in other bacterial species, namely Streptococcus agalactiae, Streptococcus gordonii, Streptococcus pyogenes, and Enterococcus faecalis showed that: (i) Tn5253 integrates in rbgA of S. pneumoniae and in orthologous rbgA genes of other bacterial species, (ii) integration occurs always downstream of a 11-bp sequence conserved among streptococcal and enterococcal hosts, (iii) length of the attB site corresponds to length of the duplication after Tn5253 integration, (iv) attB duplication restores rbgA CDS, (v) Tn5253 produced circular forms containing the attTn site at a concentration ranging between 2.0 × 10⁻⁵ to 1.2 × 10⁻² copies per chromosome depending on bacterial species and strain, (vi) reconstitution of attB sites occurred at 3.7 × 10⁻⁵ to 1.7 × 10⁻² copies per chromosome. A database search of complete microbial genomes using Tn5253 attB as a probe showed that (i) thirteen attB variants were present in the 85 complete pneumococcal genomes, (ii) in 75 pneumococcal genomes (88.3 %), the attB site was 83 or 84 nucleotides in length, while in 10 (11.7 %) it was 41 nucleotides, (iii) in other 19 bacterial species attB was located in orthologous rbgA genes and its size ranged between 17 and 84 nucleotides, (iv) the 11-bp sequence, which correspond to the last 11 nucleotides of attB sites, is conserved among the different bacterial species and can be considered the core of the Tn5253 integration site.

Conclusions

A functional characterization of the Tn5253 attB integration site combined with genome analysis contributed to elucidating the potential of Tn5253 horizontal gene transfer among different bacterial species.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13100-021-00253-z.

Long-Term Anti-Bacterial Immunity against Systemic Infection by Salmonella enterica Serovar Typhimurium Elicited by a GMMA-Based Vaccine

Salmonella Typhimurium (STm) represents the most prevalent cause of invasive non-typhoidal Salmonella (iNTS) disease, and currently no licensed vaccine is available. In this work we characterized the long-term anti-bacterial immunity elicited by a STm vaccine based on Generalized Modules of Membrane Antigens (GMMA) delivering O:4,5 antigen, using a murine model of systemic infection. Subcutaneous immunization of mice with STmGMMA/Alhydrogel elicited rapid, high, and persistent antigen-specific serum IgG and IgM responses. The serum was bactericidal in vitro. O:4,5-specific IgG were also detected in fecal samples after immunization and positively correlated with IgG observed in intestinal washes. Long-lived plasma cells and O:4,5-specific memory B cells were detected in spleen and bone marrow. After systemic STm challenge, a significant reduction of bacterial load in blood, spleen, and liver, as well as a reduction of circulating neutrophils and G-CSF glycoprotein was observed in STmGMMA/Alhydrogel immunized mice compared to untreated animals. Taken together, these data support the development of a GMMA-based vaccine for prevention of iNTS disease.

Combined therapy with ceftriaxone and doxycycline does not improve the outcome of meningococcal meningitis in mice compared to ceftriaxone monotherapy

BACKGROUND

Meningococcal meningitis (MM) is a life-threatening disease associated with approximately 10% case fatality rates and neurological sequelae in 10-20% of the cases. Recently, we have shown that the matrix metalloproteinase (MMP) inhibitor BB-94 reduced brain injury in a mouse model of MM. The present study aimed to assess whether doxycycline (DOX), a tetracycline that showed a neuroprotective effect as adjuvant therapy in experimental pneumococcal meningitis (PM), would also exert a beneficial effect when given as adjunctive therapy to ceftriaxone (CRO) in experimental MM.

METHODS

BALB/c mice were infected by the intracisternal route with a group C Neisseria meningitidis strain. Eighteen h post infection (hpi), animals were randomised for treatment with CRO [100 mg/kg subcutaneously (s.c.)], CRO plus DOX (30 mg/kg s.c.) or saline (control s.c.). Antibiotic treatment was repeated 24 and 40 hpi. Mouse survival and clinical signs, bacterial counts in cerebella, brain damage, MMP-9 and cyto/chemokine levels were assessed 48 hpi.

RESULTS

Analysis of bacterial load in cerebella indicated that CRO and CRO + DOX were equally effective at controlling meningococcal replication. No differences in survival were observed between mice treated with CRO (94.4%) or CRO + DOX (95.5%), (p > 0.05). Treatment with CRO + DOX significantly diminished both the number of cerebral hemorrhages (p = 0.029) and the amount of MMP-9 in the brain (p = 0.046) compared to untreated controls, but not to CRO-treated animals (p > 0.05). Levels of inflammatory markers in the brain of mice that received CRO or CRO + DOX were not significantly different (p > 0.05). Overall, there were no significant differences in the parameters assessed between the groups treated with CRO alone or CRO + DOX.

CONCLUSIONS

Treatment with CRO + DOX showed similar bactericidal activity to CRO in vivo, suggesting no antagonist effect of DOX on CRO. Combined therapy significantly improved mouse survival and disease severity compared to untreated animals, but addition of DOX to CRO did not offer significant benefits over CRO monotherapy. In contrast to experimental PM, DOX has no adjunctive activity in experimental MM.

Rapid dose-dependent Natural Killer (NK) cell modulation and cytokine responses following human rVSV-ZEBOV Ebolavirus vaccination

The rVSV-ZEBOV Ebolavirus vaccine confers protection within days after immunization, suggesting the contribution of innate immune responses. We report modulation of rVSV-ZEBOV vaccinee blood CD56+ NK cell numbers, NKG2D or NKp30 surface receptor expression, Killer Immunoglobulin-like Receptor (KIR)+ cell percentages and NK-cell-related genes on day 1 post immunization. Inverse correlations existed between the concentration of several plasma cytokines and inhibitory KIR+ CD56dim or cytokine-responsive CD56bright NK cells. Thus, NK cells may contribute to the early protective efficacy of rVSV-ZEBOV in humans.

In Vivo Modulation of Cervicovaginal Drug Transporters and Tissue Distribution by Film-Released Tenofovir and Darunavir for Topical Prevention of HIV-1

Clinical trials have demonstrated partial protection against HIV-1 infection by vaginal microbicide formulations based on antiretroviral (ARV) drugs. Improved formulations that will maintain sustained drug concentrations at viral target sites in the cervicovaginal mucosa are needed. We have previously demonstrated that treatment of cervicovaginal cell lines with ARV drugs can alter gene expression of drug transporters, suggesting that the mucosal disposition of ARV drugs delivered vaginally can be modulated by drug transporters. This study aimed to investigate in vivo modulation of drug transporter expression in a nonhuman primate model by tenofovir and darunavir released from film formulations. Cervicovaginal tissues were collected from drug-naïve macaques and from macaques vaginally treated with film formulations of tenofovir or darunavir. Drug release in vaginal fluid as well as drug absorption in cervicovaginal tissues and lymph nodes were verified by mass spectrometry. The effects of exposure to drugs on the expression of transporters relevant to ARV drugs were evaluated by quantitative PCR. We showed expression in cervicovaginal tissue of drug-naïve macaques of transporters important for distribution of ARV drugs, albeit at lower levels compared to human tissue for key transporters including P-glycoprotein. Concentrations of tenofovir and darunavir well above the EC₅₀ values determined in vitro were detected in vaginal fluid and vaginal tissues of macaques treated with drug-dissolving films over 24 h and were also comparable to those shown previously to modulate drug transporter expression. Accordingly, Multidrug Resistance associated Protein 2 (MRP2) in cervicovaginal tissue was upregulated by both tenofovir and darunavir. The two drugs also differentially induced and/or inhibited expression of key uptake transporters for reverse transcriptase inhibitors and protease inhibitors. The lower expression of key transporters in macaques may result in increased retention of ARV drugs at the simian cervicovaginal mucosa compared to the human mucosa and has implications for translation of preclinical data. Modulation of drug transporter expression by tenofovir and darunavir points to the potential benefit of MRP2 inhibition to increase ARV drug penetration through the cervicovaginal epithelium.

Computational Analysis of Multiparametric Flow Cytometric Data to Dissect B Cell Subsets in Vaccine Studies

The generation of the B cell response upon vaccination is characterized by the induction of different functional and phenotypic subpopulations and is strongly dependent on the vaccine formulation, including the adjuvant used. Here, we have profiled the different B cell subsets elicited upon vaccination, using machine learning methods for interpreting high‐dimensional flow cytometry data sets. The B cell response elicited by an adjuvanted vaccine formulation, compared to the antigen alone, was characterized using two automated methods based on clustering (FlowSOM) and dimensional reduction (t‐SNE) approaches. The clustering method identified, based on multiple marker expression, different B cell populations, including plasmablasts, plasma cells, germinal center B cells and their subsets, while this profiling was more difficult with t‐SNE analysis. When undefined phenotypes were detected, their characterization could be improved by integrating the t‐SNE spatial visualization of cells with the FlowSOM clusters. The frequency of some cellular subsets, in particular plasma cells, was significantly higher in lymph nodes of mice primed with the adjuvanted formulation compared to antigen alone. Thanks to this automatic data analysis it was possible to identify, in an unbiased way, different B cell populations and also intermediate stages of cell differentiation elicited by immunization, thus providing a signature of B cell recall response that can be hardly obtained with the classical bidimensional gating analysis. © 2019 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

Virulence Traits of a Serogroup C Meningococcus and Isogenic cssA Mutant, Defective in Surface-Exposed Sialic Acid, in a Murine Model of Meningitis

In serogroup C Neisseria meningitidis, the cssA (siaA) gene codes for an UDP-N-acetylglucosamine 2-epimerase that catalyzes the conversion of UDP-N-acetyl-α-d-glucosamine into N-acetyl-d-mannosamine and UDP in the first step in sialic acid biosynthesis. This enzyme is required for the biosynthesis of the (α2→9)-linked polysialic acid capsule and for lipooligosaccharide (LOS) sialylation. In this study, we have used a reference serogroup C meningococcal strain and an isogenic cssA knockout mutant to investigate the pathogenetic role of surface-exposed sialic acids in a model of meningitis based on intracisternal inoculation of BALB/c mice. Results confirmed the key role of surface-exposed sialic acids in meningococcal pathogenesis. The 50% lethal dose (LD50) of the wild-type strain 93/4286 was about four orders of magnitude lower than that of the cssA mutant. Compared to the wild-type strain, the ability of this mutant to replicate in brain and spread systemically was severely impaired. Evaluation of brain damage evidenced a significant reduction in cerebral hemorrhages in mice infected with the mutant in comparison with the levels in those challenged with the wild-type strain. Histological analysis showed the typical features of bacterial meningitis, including inflammatory cells in the subarachnoid, perivascular, and ventricular spaces especially in animals infected with the wild type. Noticeably, 80% of mice infected with the wild-type strain presented with massive bacterial localization and accompanying inflammatory infiltrate in the corpus callosum, indicating high tropism of meningococci exposing sialic acids toward this brain structure and a specific involvement of the corpus callosum in the mouse model of meningococcal meningitis.