Group B Streptococcus and diabetes: Finding the sweet spot

Tissue-Adhesive and Antibacterial Hydrogel Promotes MDR Bacteria-Infected Diabetic Wound Healing via Disrupting Bacterial Biofilm, Scavenging ROS and Promoting Angiogenesis

Effective treatment of diabetic wounds remains challenging because of multidrug-resistant (MDR) bacterial infections, excessive oxidative stress, and impaired angiogenesis. In this study, a tissue-adhesive and antibacterial hydrogel incorporating MXene and deferoxamine (DFO)-loaded microspheres is developed for the treatment of MDR bacteria-infected diabetic wounds. The hydrogel is built based on covalent crosslinking between ε-poly(L-lysine) and o-phthalaldehyde-terminated four-arm poly(ethylene glycol). The hydrogel exhibited excellent mechanical properties, tissue adhesion strength, biocompatibility, and biodegradability. Under near-infrared (NIR) irradiation, the MXene converted light into heat and elevated the local temperature rapidly, enabling the rapid disintegration of MDR bacterial biofilms. Simultaneously, the hydrogel exerted inherent antibacterial activity, persistently killing planktonic bacteria, and effectively controlling wound infections. The encapsulated DFO is then released from the hydrogel in a sustained and controlled manner, and promoted angiogenesis during diabetic wound healing. Additionally, MXenes can scavenge excessive reactive oxygen species and alleviate wound inflammation. In the methicillin-resistant Staphylococcus aureus-infected diabetic wound model in mice, the composite hydrogel along with NIR irradiation efficiently reduced the infectious bacteria, and accelerated the wound healing by promoting angiogenesis and alleviating inflammation. This composite hydrogel has great clinical potential for the treatment of diabetic wounds, particularly in challenging healing environments involving motion and infection.

Effect and mechanism of oritavancin on hIAPP amyloid formation

Amyloidosis of the human islet amyloid polypeptide (hIAPP) is closely related to the pathogenesis of type 2 diabetes (T2D) and serves as both a diagnostic hallmark and a key therapeutic target for T2D. In this study, we discovered that oritavancin (Ori), a glycopeptide antibiotic primarily prescribed for Gram-positive bacterial infections, can dose-dependently inhibit recombinant hIAPP (rhIAPP) amyloid formation. Ori specifically inhibited rhIAPP amyloid formation at the initial nucleation stage but didn't affect mature rhIAPP fibrils. As a result, Ori reduced amyloidosis of rhIAPP induced pancreatic NIT-1 cell apoptosis and reactive oxygen species (ROS) release. Based on the results from studies involving antibiotic homologues of Ori and its acid hydrolysates, we demonstrated that both the N-(4-chlorobiphenyl) methyl group (CBP) and glycopeptide backbone were necessary for inhibiting rhIAPP amyloid formation. The mechanism behind Ori on rhIAPP amyloid formation lies in the direct interaction of the two molecules identified by ESI-MS and molecular docking assays. Consequently, this research not only lays the groundwork for developing novel therapeutic approaches for T2D but also presents the opportunity to repurpose Ori as a treatment option.

Maternal and neonatal outcomes of Group B Streptococcus colonization: a retrospective study

BACKGROUND

Group B Streptococcus (GBS) colonization is one of the major causes of severe neonatal infections. The study was intended to identify GBS colonization in pregnant women, explore its potential risk factors, and analyze the impact of GBS on outcomes for both mothers and newborns.

MATERIAL AND METHODS

A retrospective research was carried out on pregnant women who had undergone GBS screening and delivered from June 2020 to December 2022. Pregnant women between 35 and 37 weeks of gestation had GBS screening using real-time polymerase chain reaction (RT-PCR). The clinical characteristics and outcomes of mothers and newborns were collected. The risk factors linked to maternal GBS colonization and its impact on adverse outcomes for mothers and neonates were assessed using chi-square and logistic regression analyses. The composite neonatal adverse outcomes included low Apgar scores, neonatal pneumonia, neonatal hyperbilirubinemia, neonatal sepsis, or low birth weight.

RESULTS

Overall, the rate of GBS positivity was 10.63% (551/5183), and the rate of maternal GBS screening was 88.4%. Diabetic pregnant women were more likely to become colonized with GBS. Our research revealed that GBS carriers experienced higher rates of fetal distress and neonatal adverse outcomes than non-GBS carriers. Fetal distress (OR, 1.940; 95% CI, 1.355 to 2.778, P < 0.001), neonatal sepsis (OR, 5.063; 95% CI, 2.536-10.109, P < 0.001), low Apgar scores (OR, 2.097; 95% CI, 1.184-3.715, P = 0.011), neonatal pneumonia (OR, 1.638; 95% CI, 1.039 to 2.582, P = 0.034) and neonatal hyperbilirubinemia (OR, 1.438; 95% CI, 1.080 to 1.915, P = 0.013) were significantly related to maternal GBS colonization. When we used the composite adverse neonatal outcomes as the dependent variable and analyzed the influencing factors, the logistic regression analysis revealed that GBS colonization was still significantly related to an elevated risk of adverse neonatal outcomes (OR = 1.752, 95% CI, 1.389-2.208; P < 0.001).

CONCLUSIONS

Diabetes may be a risk factor for maternal GBS colonization. Moreover, in this study, GBS colonization correlated with neonatal adverse outcomes but not with maternal outcomes.

Re-framing the importance of Group B Streptococcus as a gut-resident pathobiont

Streptococcus agalactiae (Group B Streptococcus, GBS) is a Gram-positive bacterial species that causes disease in humans across the lifespan. While antibiotics are used to mitigate GBS infections, it is evident that antibiotics disrupt human microbiomes (which can predispose people to other diseases later in life), and antibiotic resistance in GBS is on the rise. Taken together, these unintended negative impacts of antibiotics highlight the need for precision approaches for minimizing GBS disease. One possible approach involves selectively depleting GBS in its commensal niches before it can cause disease at other body sites or be transmitted to at-risk individuals. One understudied commensal niche of GBS is the adult gastrointestinal (GI) tract, which may predispose colonization at other body sites in individuals at risk for GBS disease. However, a better understanding of the host-, microbiome-, and GBS-determined variables that dictate GBS GI carriage is needed before precise GI decolonization approaches can be developed. In this review, we synthesize current knowledge of the diverse body sites occupied by GBS as a pathogen and as a commensal. We summarize key molecular factors GBS utilizes to colonize different host-associated niches to inform future efforts to study GBS in the GI tract. We also discuss other GI commensals that are pathogenic in other body sites to emphasize the broader utility of precise de-colonization approaches for mitigating infections by GBS and other bacterial pathogens. Finally, we highlight how GBS treatments could be improved with a more holistic understanding of GBS enabled by continued GI-focused study.

Triple threat: how diabetes results in worsened bacterial infections

Diabetes mellitus, characterized by impaired insulin signaling, is associated with increased incidence and severity of infections. Various diabetes-related complications contribute to exacerbated bacterial infections, including hyperglycemia, innate immune cell dysfunction, and infection with antibiotic-resistant bacterial strains. One defining symptom of diabetes is hyperglycemia, resulting in elevated blood and tissue glucose concentrations. Glucose is the preferred carbon source of several bacterial pathogens, and hyperglycemia escalates bacterial growth and virulence. Hyperglycemia promotes specific mechanisms of bacterial virulence known to contribute to infection chronicity, including tissue adherence and biofilm formation. Foot infections are a significant source of morbidity in individuals with diabetes and consist of biofilm-associated polymicrobial communities. Bacteria perform complex interspecies behaviors conducive to their growth and virulence within biofilms, including metabolic cross-feeding and altered phenotypes more tolerant to antibiotic therapeutics. Moreover, the metabolic dysfunction caused by diabetes compromises immune cell function, resulting in immune suppression. Impaired insulin signaling induces aberrations in phagocytic cells, which are crucial mediators for controlling and resolving bacterial infections. These aberrancies encompass altered cytokine profiles, the migratory and chemotactic mechanisms of neutrophils, and the metabolic reprogramming required for the oxidative burst and subsequent generation of bactericidal free radicals. Furthermore, the immune suppression caused by diabetes and the polymicrobial nature of the diabetic infection microenvironment may promote the emergence of novel strains of multidrug-resistant bacterial pathogens. This review focuses on the "triple threat" linked to worsened bacterial infections in individuals with diabetes: (i) altered nutritional availability in diabetic tissues, (ii) diabetes-associated immune suppression, and (iii) antibiotic treatment failure.

Group B Streptococcus Meningitis in an Adult Woman with Type 2 Diabetes and Ethmoid Roof Defect. Impact on "frontal" Cognitive Functions

BACKGROUND

Community-acquired bacterial meningitis in adults represents one of the most severe infectious diseases worldwide with potentially life-threatening medical complications. Several infectious agents can cause acute meningitis. Although group B Streptococcus is more prevalent in newborns, infection can also lead to meningitis in older adults, particularly those with underlying health issues.

CASE DESCRIPTION

A 53-year-old woman with a body mass index of 28.7 kg/m2, type 2 diabetes mellitus, and dyslipidaemia presented to the emergency department of Santa Maria della Stella Hospital (Orvieto, Italy) with confusion, low-grade fever, echolalia, and hyperglycaemia. Computed tomography scans of the brain revealed a hypodensity in the left anterior frontal lobe and an osteodural defect of the rhinobase. Meningitis was suspected and empiric broad-spectrum antibiotic therapy with corticosteroids and insulin were administered while the results of the cerebrospinal fluid analysis confirmed the diagnosis of group B Streptococcus meningitis. Repeat imaging at 48 hours revealed enlargement of the hypodense lesion. The frontal assessment battery indicated deficits in executive functions. Prompt treatment led to rapid clinical improvement. Following the restoration of euglycemic status and hemodynamic stabilization, a follow-up magnetic resonance imaging confirmed the ischaemic lesion and showed cerebrospinal fluid in the sella turcica. The patient was then transferred to neurorehabilitation.

CONCLUSIONS

The complex interactions among multiple risk factors resulted in an atypical clinical case of group B Streptococcus meningitis, which was promptly treated with empiric antibiotic therapy to mitigate neurocognitive deficits.

LEARNING POINTS

Group B Streptococcus can cause meningitis in adults with poorly controlled type 2 diabetes mellitus and should be promptly treated with empiric broad-spectrum antibiotics.An osteodural defect of the ethmoid roof together with idiopathic intracranial hypertension may result in empty sella turcica and CSF rhinorrhoea, promoting the dissemination of the pathogen.Meningitis patients with pre-existing diabetic cerebral vasculopathy may develop cerebrovascular complications and cognitive impairments.

Engagement of α3β1 and α2β1 integrins by hypervirulent Streptococcus agalactiae in invasion of polarized enterocytes

The gut represents an important site of colonization of the commensal bacterium Streptococcus agalactiae (group B Streptococcus or GBS), which can also behave as a deadly pathogen in neonates and adults. Invasion of the intestinal epithelial barrier is likely a crucial step in the pathogenesis of neonatal infections caused by GBS belonging to clonal complex 17 (CC17). We have previously shown that the prototypical CC17 BM110 strain invades polarized enterocyte-like cells through their lateral surfaces using an endocytic pathway. By analyzing the cellular distribution of putative GBS receptors in human enterocyte-like Caco-2 cells, we find here that the alpha 3 (α3) and alpha 2 (α2) integrin subunits are selectively expressed on lateral enterocyte surfaces at equatorial and parabasal levels along the vertical axis of polarized cells, in an area corresponding to GBS entry sites. The α3β1 and α2β1 integrins were not readily accessible in fully differentiated Caco-2 monolayers but could be exposed to specific antibodies after weakening of intercellular junctions in calcium-free media. Under these conditions, anti-α3β1 and anti-α2β1 antibodies significantly reduced GBS adhesion to and invasion of enterocytes. After endocytosis, α3β1 and α2β1 integrins localized to areas of actin remodeling around GBS containing vacuoles. Taken together, these data indicate that GBS can invade enterocytes by binding to α3β1 and α2β1 integrins on the lateral membrane of polarized enterocytes, resulting in cytoskeletal remodeling and bacterial internalization. Blocking integrins might represent a viable strategy to prevent GBS invasion of gut epithelial tissues.

Regulation of PhoB on biofilm formation and hemolysin gene hlyA and ciaR of Streptococcus agalactiae

PhoB is a response regulator protein that plays a key role in the PhoBR two-component signal transduction system. In this study, we used transcriptome and proteomics techniques to evaluate the detect the gene network regulated by PhoB of Streptococcus agalactiae. The results showed that expression of biofilm formation and virulence-related genes were changed after phoB deficiency. Crystal violet and CLSM assay confirmed that the deletion of the phoB increased the thickness of S. agalactiae biofilm. The results of lacZ reporter and the bacterial one-hybridization method showed that PhoB could directly bind to the promoter regions of hemolysin A and ciaR genes but not to the promoter regions of cylE and hemolysin III. Through the construction of an 18-base pair deoxyribose nucleic acid (DNA) random fragment library and the bacterial one-hybridization system, it was found that the conservative sequence of PhoB binding was TTGGAGAA(G/T). Our research has uncovered the virulence potential of the PhoBR two-component system of S. agalactiae. The findings of this study provide the theoretical foundation for in-depth research on the pathogenic mechanism of S. agalactiae.

The impact of nutritional immunity on Group B streptococcal pathogenesis during wound infection

Group B Streptococcus (GBS) is a Gram-positive pathobiont that can cause adverse health outcomes in neonates and vulnerable adult populations. GBS is one of the most frequently isolated bacteria from diabetic (Db) wound infections but is rarely found in the non-diabetic (nDb) wound environment. Previously, RNA sequencing of wound tissue from Db wound infections in leprdb diabetic mice showed increased expression of neutrophil factors, and genes involved in GBS metal transport such as the zinc (Zn), manganese (Mn), and putative nickel (Ni) import systems. Here, we develop a Streptozotocin-induced diabetic wound model to evaluate the pathogenesis of two invasive strains of GBS, serotypes Ia and V. We observe an increase in metal chelators such as calprotectin (CP) and lipocalin-2 during diabetic wound infections compared to nDb. We find that CP limits GBS survival in wounds of non-diabetic mice but does not impact survival in diabetic wounds. Additionally, we utilize GBS metal transporter mutants and determine that the Zn, Mn, and putative Ni transporters in GBS are dispensable in diabetic wound infection but contributed to bacterial persistence in non-diabetic animals. Collectively, these data suggest that in non-diabetic mice, functional nutritional immunity mediated by CP is effective at mitigating GBS infection, whereas in diabetic mice, the presence of CP is not sufficient to control GBS wound persistence. IMPORTANCE Diabetic wound infections are difficult to treat and often become chronic due to an impaired immune response as well as the presence of bacterial species that establish persistent infections. Group B Streptococcus (GBS) is one of the most frequently isolated bacterial species in diabetic wound infections and, as a result, is one of the leading causes of death from skin and subcutaneous infection. However, GBS is notoriously absent in non-diabetic wounds, and little is known about why this species thrives in diabetic infection. The work herein investigates how alterations in diabetic host immunity may contribute to GBS success during diabetic wound infection.

Unveiling the Human Gastrointestinal Tract Microbiome: The Past, Present, and Future of Metagenomics

Over 10¹⁴ symbiotic microorganisms are present in a healthy human body and are responsible for the synthesis of vital vitamins and amino acids, mediating cellular pathways and supporting immunity. However, the deregulation of microbial dynamics can provoke diverse human diseases such as diabetes, human cancers, cardiovascular diseases, and neurological disorders. The human gastrointestinal tract constitutes a hospitable environment in which a plethora of microbes, including diverse species of archaea, bacteria, fungi, and microeukaryotes as well as viruses, inhabit. In particular, the gut microbiome is the largest microbiome community in the human body and has drawn for decades the attention of scientists for its significance in medical microbiology. Revolutions in sequencing techniques, including 16S rRNA and ITS amplicon sequencing and whole genome sequencing, facilitate the detection of microbiomes and have opened new vistas in the study of human microbiota. Especially, the flourishing fields of metagenomics and metatranscriptomics aim to detect all genomes and transcriptomes that are retrieved from environmental and human samples. The present review highlights the complexity of the gastrointestinal tract microbiome and deciphers its implication not only in cellular homeostasis but also in human diseases. Finally, a thorough description of the widely used microbiome detection methods is discussed.