Mucus-degrading Bacteroides link carbapenems to aggravated graft-versus-host disease.

The intestinal microbiota is an important modulator of graft-versus-host disease (GVHD), which often complicates allogeneic hematopoietic stem cell transplantation (allo-HSCT). Broad-spectrum antibiotics such as carbapenems increase the risk for intestinal GVHD, but mechanisms are not well understood. In this study, we found that treatment with meropenem, a commonly used carbapenem, aggravates colonic GVHD in mice via the expansion of Bacteroides thetaiotaomicron (BT). BT has a broad ability to degrade dietary polysaccharides and host mucin glycans. BT in meropenem-treated allogeneic mice demonstrated upregulated expression of enzymes involved in the degradation of mucin glycans. These mice also had thinning of the colonic mucus layer and decreased levels of xylose in colonic luminal contents. Interestingly, oral xylose supplementation significantly prevented thinning of the colonic mucus layer in meropenem-treated mice. Specific nutritional supplementation strategies, including xylose supplementation, may combat antibiotic-mediated microbiome injury to reduce the risk for intestinal GVHD in allo-HSCT patients.

Development of Gendine-Coated Cannula for Continuous Subcutaneous Insulin Infusion for Extended Use.

Continuous subcutaneous insulin infusion (CSII) using pumps is a widely used method for insulin therapy in patients with diabetes mellitus. Among the major factors that usually lead to the discontinuation of CSII are CSII set-related issues, including infection at the infusion site. The American Diabetic Association currently recommends rotating sites every 2 to 3 days. This recommendation adds cost and creates inconvenience. Therefore, in order to prevent infections and extend the duration between insertion site changes, we developed a Teflon cannula coated with a combination of gentian violet and chlorhexidine (gendine) and tested its antimicrobial efficacy against different pathogens. The cannulas were coated with gendine on the exterior surface and dried. The efficacy and durability of gendine-coated cannulas were determined against methicillin-resistant Staphylococcus aureus, Staphylococcus epidermidis, methicillin-susceptible S. aureus, Streptococcus pyogenes, vancomycin-resistant enterococci, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, and Candida glabrata using a biofilm colonization method. The cytotoxicity of gendine was assessed against mouse fibroblast cell lines. The gendine-coated cannulas showed complete prevention of biofilm colonization of all organisms tested for up to 2 weeks (P < 0.0001) compared to that with the uncoated control. A gendine-coated catheter against mouse fibroblast cells was shown to be noncytotoxic. Our in vitro results show that a novel gendine cannula is highly effective in completely inhibiting the biofilm of multidrug-resistant pathogens for up to 2 weeks and may have potential clinical applications, such as prolonged use, cost reduction, and lower infection rate.

In vivo biocompatibility and in vitro efficacy of antimicrobial gendine-coated central catheters.

Antimicrobial peripherally inserted central catheters (PICCs) might reduce the incidence of central line-associated bloodstream infections (CLABSI). We tested the biocompatibility of a novel gendine-coated (combination of chlorhexidine [CHX] and gentian violet [GV]) PICC in a rabbit intravascular model and tested antimicrobial efficacy in comparison with commercially available minocycline/rifampin (M/R)- and CHX-treated PICCs in an in vitro biofilm colonization model. Gendine-coated and uncoated control PICCs were inserted in the jugular veins of rabbits for 4 days. Histopathological analysis was performed at the end of the 4-day period, and circulating levels of CHX and GV in the blood were measured at different time points using liquid chromatography-mass spectrometry. The antimicrobial efficacy of the PICCs was tested following simulated intravascular indwells of 24 h and 1 week against clinical isolates of methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, Pseudomonas aeruginosa, Escherichia coli, Acinetobacter baumannii, Enterobacter cloacae, Candida albicans, and Candida glabrata. Rabbits implanted with gendine-coated PICCs exhibited reduced levels of thrombosis and inflammation compared to those of the rabbits with uncoated controls. No GV was detected in blood samples over the entire study period, and trace concentrations of CHX were detected. The gendine-coated PICCs completely prevented the adherence of all pathogens from 24 h to 1 week (P ≤ 0.001), while M/R-treated, CHX-treated, and control PICCs did not. Gendine-coated PICCs were highly effective in preventing biofilm formation of multidrug-resistant pathogenic bacteria and fungi. Gendine-coated PICCs were biocompatible in an intravascular setting. Further, the pharmacokinetic testing established that acute systemic exposures of CHX and GV from the gendine-coated catheters were well within safe levels.

Biofilm-based central line-associated bloodstream infections.

Different types of central venous catheters (CVCs) have been used in clinical practice to improve the quality of life of chronically and critically ill patients. Unfortunately, indwelling devices are usually associated with microbial biofilms and eventually lead to catheter-related bloodstream infections (CLABSIs).An estimated 250,000-400,000 CLABSIs occur every year in the United States, at a rate of 1.5 per 1,000 CVC days and a mortality rate of 12-25 %. The annual cost of caring for patients with CLABSIs ranges from 296 million to 2.3 billion dollars.Biofilm formation occurs on biotic and abiotic surfaces in the clinical setting. Extensive studies have been conducted to understand biofilm formation, including different biofilm developmental stages, biofilm matrix compositions, quorum-sensing regulated biofilm formation, biofilm dispersal (and its clinical implications), and multi-species biofilms that are relevant to polymicrobial infections.When microbes form a matured biofilm within human hosts through medical devices such as CVCs, the infection becomes resistant to antibiotic treatment and can develop into a chronic condition. For that reason, many techniques have been used to prevent the formation of biofilm by targeting different stages of biofilm maturation. Other methods have been used to diagnose and treat established cases of CLABSI.Catheter removal is the conventional management of catheter associated bacteremia; however, the procedure itself carries a relatively high risk of mechanical complications. Salvaging the catheter can help to minimize these complications.In this article, we provide an overview of microbial biofilm formation; describe the involvement of various genetic determinants, adhesion proteins, organelles, mechanism(s) of biofilm formation, polymicrobial infections, and biofilm-associated infections on indwelling intravascular catheters; and describe the diagnosis, management, and prevention of catheter-related bloodstream infections.

Prevention of transmission of multidrug-resistant organisms during catheter exchange using antimicrobial catheters.

Exchanging a central venous catheter (CVC) over a guide wire for a fresh uncoated CVC in the presence of bacteremia can result in cross-infection of the newly exchanged CVC. A recent retrospective clinical study showed that exchanging a catheter over a guide wire in the presence of bacteremia using an antimicrobial minocycline-rifampin (M/R) catheter may improve outcomes. To expand on this, we developed an in vitro cross-contamination model of exchange to evaluate the efficacy of different antimicrobial CVCs in preventing cross-contamination of multidrug-resistant organisms during exchange. Uncoated CVCs were allowed to form biofilm by methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. After 24 h, the biofilm-colonized CVCs were placed in a glass tube containing bovine calf serum plus Mueller-Hinton broth, and each catheter was exchanged over a guide wire for a fresh uncoated or an M/R-, chlorhexidine-silver sulfadiazine (CHX/SS)-, or chlorhexidine-M/R (CHX-M/R)-coated CVC. Cross-contamination of exchanged catheters was enumerated by sonication and quantitative plating methods. The exchange of M/R CVCs completely prevented cross-contamination by MRSA biofilms compared to control exchanged CVCs (P<0.0001). Exchange with CHX/SS CVCs reduced but did not completely prevent cross-contamination by MRSA (P=0.005). Exchange with CHX-M/R CVCs completely prevented cross-contamination by MRSA, P. aeruginosa, and C. albicans biofilms (P<0.0001). Furthermore, CHX-M/R CVCs were superior to M/R CVCs against P. aeruginosa and C. albicans (P=0.003) and were superior to CHX/SS CVCs against MRSA and P. aeruginosa (P=0.01). In conclusion, exchange with the novel CHX-M/R CVC was the only exchange effective in completely and concurrently preventing cross-contamination from bacteria and Candida.

Prevention of biofilm colonization by Gram-negative bacteria on minocycline-rifampin-impregnated catheters sequentially coated with chlorhexidine.

Resistant Gram-negative bacteria are increasing central-line-associated bloodstream infection threats. To better combat this, chlorhexidine (CHX) was added to minocycline-rifampin (M/R) catheters. The in vitro antimicrobial activity of CHX-M/R catheters against multidrug resistant, Gram-negative Acinetobacter baumannii, Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia was tested. M/R and CHX-silver sulfadiazine (CHX/SS) catheters were used as comparators. The novel CHX-M/R catheters were significantly more effective (P < 0.0001) than CHX/SS or M/R catheters in preventing biofilm colonization and showed better antimicrobial durability.

The use of minocycline-rifampin coated central venous catheters for exchange of catheters in the setting of staphylococcus aureus central line associated bloodstream infections.

BACKGROUND: Central venous catheters (CVC) removal and reinsertion of a new CVC in the setting of central line associated bloodstream infections (CLABSI) is not always possible in septic patients. The purpose of this study was to evaluate the outcome of patients with Staphylococcus aureus-CLABSI (SA-CLABSI) who had their CVCs exchanged over guidewire for minocycline/rifampin-coated (M/R)-CVC within seven days of bacteremia. METHODS: Each case was matched with two control patients who had SA-CLABSI and had their CVC removed within seven days and two control patients who had their CVC retained beyond seven days. In addition, an in vitro model was developed for exchange of catheters. RESULTS: We identified 40 patients with SA-CLABSI. Eight patients had their CVC exchanged over guidewire with M/R-CVC and were compared to 16 patients who had their CVC removed and 16 other patients who had their CVC retained. Patients who had their CVC exchanged over guidewire had a similar clinical response and relapse rates compared to patients whose CVC was removed or retained. However the rate of overall mortality was higher in patients who retained their CVC compared to those whose CVC was exchanged or removed (p = 0.034). The in vitro catheter exchange model showed that catheter exchange over guidewire using M/R-CVC completely prevented biofilm colonization compared to exchange using uncoated CVC (p < 0.0001). CONCLUSIONS: In the setting of SA-CLABSI, exchanging the CVC over guidewire with M/R-CVC could be an alternative to removing the CVC and reinserting another CVC at a different site and may be associated with a lower rate of overall mortality. Further large prospective randomized clinical trials are warranted.

Protection against fibrosis by a bacterial consortium in metabolic dysfunction-associated steatohepatitis and the role of amino acid metabolism.

The gut microbiota drives progression to liver fibrosis, the main determinant of mortality in metabolic dysfunction-associated steatohepatitis (MASH). In this study, we aimed to identify bacterial species associated with protection against liver fibrosis in a high-risk population, and test their potential to protect against liver fibrosis in vivo. Based on stool shotgun metagenomic sequencing of 340 subjects from a population cohort disproportionally affected by MASH, we identified bacterial species from the Bacteroidales and Clostridiales orders associated with reduced risk of liver fibrosis. A bacterial consortium was subsequently tested in a mouse model of MASH, which demonstrated protective effects against liver fibrosis. Six of the eight inoculated bacteria were detected in mouse stool and liver. Intrahepatic presence of bacteria was further confirmed by bacterial culture of mouse liver tissue. Changes in liver histological parameters, gut functional profiles, and amino acid profiles were additionally assessed. Comparison between fibrosis-associated human metagenome and bacteria-induced metagenome changes in mice identified microbial functions likely to mediate the protective effect against liver fibrosis. Amino acid profiling confirmed an increase in cysteine synthase activity, associated with reduced fibrosis. Other microbiota-induced changes in amino acids associated with reduced fibrosis included increased gut asparaginase activity and decreased hepatic tryptophan-to-kynurenine conversion. This human-to-mouse study identified bacterial species and their effects on amino acid metabolism as innovative strategies to protect against liver fibrosis in MASH.

Inflammation mediated by gut microbiome alterations promotes lung cancer development and an immunosuppressed tumor microenvironment.

Accumulating evidence indicates that the gut microbiome influences cancer progression and therapy. We recently showed that progressive changes in gut microbial diversity and composition are closely associated with tobacco-associated lung adenocarcinoma (LUAD) in a human-relevant mouse model. Furthermore, we demonstrated that the loss of the antimicrobial protein Lcn2 in these mice, exacerbates pro-tumor inflammatory phenotypes while further reducing microbial diversity. Yet, how gut microbiome alterations impinge on LUAD development remains poorly understood. Here, we investigated the role of gut microbiome changes in LUAD development using fecal microbiota transfer and delineated a pathway by which gut microbiome alterations incurred by loss of Lcn2 fostered the proliferation of pro-inflammatory bacteria of the genus Alistipes, triggering gut inflammation. This inflammation propagated systemically, exerting immunosuppression within the tumor microenvironment, augmenting tumor growth through an IL-6-dependent mechanism and dampening response to immunotherapy. Corroborating our preclinical findings, we found that patients with LUAD with a higher relative abundance of Alistipes species in the gut showed diminished response to neoadjuvant immunotherapy. These insights reveal the role of microbiome-induced inflammation in LUAD and present new potential targets for interception and therapy.

Bacteroides ovatus alleviates dysbiotic microbiota-induced graft-versus-host disease.

Acute lower gastrointestinal GVHD (aLGI-GVHD) is a serious complication of allogeneic hematopoietic stem cell transplantation. Although the intestinal microbiota is associated with the incidence of aLGI-GVHD, how the intestinal microbiota impacts treatment responses in aLGI-GVHD has not been thoroughly studied. In a cohort of patients with aLGI-GVHD (n = 37), we found that non-response to standard therapy with corticosteroids was associated with prior treatment with carbapenem antibiotics and a disrupted fecal microbiome characterized by reduced abundances of Bacteroides ovatus. In a murine GVHD model aggravated by carbapenem antibiotics, introducing B. ovatus reduced GVHD severity and improved survival. These beneficial effects of Bacteroides ovatus were linked to its ability to metabolize dietary polysaccharides into monosaccharides, which suppressed the mucus-degrading capabilities of colonic mucus degraders such as Bacteroides thetaiotaomicron and Akkermansia muciniphila, thus reducing GVHD-related mortality. Collectively, these findings reveal the importance of microbiota in aLGI-GVHD and therapeutic potential of B. ovatus.

Bacteroides ovatus alleviates dysbiotic microbiota-induced intestinal graft-versus-host disease.

Acute gastrointestinal intestinal GVHD (aGI-GVHD) is a serious complication of allogeneic hematopoietic stem cell transplantation, and the intestinal microbiota is known to impact on its severity. However, an association between treatment response of aGI-GVHD and the intestinal microbiota has not been well-studied. In a cohort of patients with aGI-GVHD (n=37), we found that non-response to standard therapy with corticosteroids was associated with prior treatment with carbapenem antibiotics and loss of Bacteroides ovatus from the microbiome. In a mouse model of carbapenem-aggravated GVHD, introducing Bacteroides ovatus reduced severity of GVHD and improved survival. Bacteroides ovatus reduced degradation of colonic mucus by another intestinal commensal, Bacteroides thetaiotaomicron, via its ability to metabolize dietary polysaccharides into monosaccharides, which then inhibit mucus degradation by Bacteroides thetaiotaomicron and reduce GVHD-related mortality.

Dietary fiber and probiotics influence the gut microbiome and melanoma immunotherapy response.

Gut bacteria modulate the response to immune checkpoint blockade (ICB) treatment in cancer, but the effect of diet and supplements on this interaction is not well studied. We assessed fecal microbiota profiles, dietary habits, and commercially available probiotic supplement use in melanoma patients and performed parallel preclinical studies. Higher dietary fiber was associated with significantly improved progression-free survival in 128 patients on ICB, with the most pronounced benefit observed in patients with sufficient dietary fiber intake and no probiotic use. Findings were recapitulated in preclinical models, which demonstrated impaired treatment response to anti­programmed cell death 1 (anti­PD-1)­based therapy in mice receiving a low-fiber diet or probiotics, with a lower frequency of interferon-γ­positive cytotoxic T cells in the tumor microenvironment. Together, these data have clinical implications for patients receiving ICB for cancer.

In vitro activity of ceftaroline and comparator agents against Gram-positive and Gram-negative clinical isolates from cancer patients.

Bacterial infections are common in cancer patients. Ceftaroline (CFT) is a broad-spectrum cephalosporin with activity against most Gram-positive organisms (GPOs) and many Gram-negative organisms. In this study, the in vitro activity of CFT was compared with vancomycin (VAN), daptomycin (DAP), linezolid (LZD), trimethoprim/sulphamethoxazole (SXT) and tigecycline (TIG) against bacteria (predominantly blood culture isolates) isolated from cancer patients in 2014 and 2015. CFT was active against methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), methicillin-susceptible coagulase-negative staphylococci (MS-CoNS) and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) with MIC90 values (minimum inhibitory concentration that inhibited 90% of the isolates) of 0.25, 2.0, 0.12 and 0.5 mg/L, respectively. MIC90 values for other GPOs were: Bacillus spp., >8.0 mg/L; Corynebacterium spp., 2.0 mg/L; Micrococcus spp., <0.06 mg/L; viridans group streptococci, 0.5 mg/L; Streptococcus pneumoniae, 0.25 mg/L; and Streptococcus spp., <0.06 mg/L. Among the comparator agents, VAN, DAP, TIG and LZD were active against the majority of GPOs tested. CFT also had moderate activity against common extended-spectrum ß-lactamase (ESBL)-negative Gram-negative bacilli such as Enterobacter cloacae, Escherichia coli, Klebsiella spp., Proteus mirabilis and Serratia spp.

Novel in situ liquefying antimicrobial wrap for preventing tissue expander infections following breast reconstructive surgeries.

Breast reconstruction surgeries using tissue expanders (TEs) have highly reported infection rates. To decrease this, we developed a method for disinfecting TEs and surgical pockets, where an antimicrobial solution was applied as a solid film at implantation that subsequently liquefied in situ to provide extended prophylaxis. Silicone discs cut from TEs were covered with gelatin-based films containing minocycline (M) and rifampin (R). Discs and films soaked in saline were subsequently challenged with pathogen at days 1, 3, 7, and 10 and quantified for potential biofilm formation. Discs that were not harvested at each specific time points were refreshed with sterile saline. The discs were challenged with clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE), and multidrug-resistant Pseudomonas aeruginosa (MDR-PA). Recoveries of adherent organisms from uncovered silicone discs and gelatin-wrapped discs without added antimicrobial agents were >5 × 10(4) CFU/disc for each organism at each time point. Experimental 0.1%M/0.05%R gelatin films completely inhibited all challenge organisms from attaching to the silicone (p < 0.05) at each time point through day 10. Cytotoxicity was assessed by incubating films with HEK-293T human fibroblasts. There were no significant differences in HEK-293T cell survival between controls and any of the antimicrobial films. The in situ liquefying, bioabsorable, antimicrobial wrap prevented biofilm formation by microorganisms on silicone surfaces in vitro with minimal cytotoxicity.