Pretreatment with Antibiotics Impairs Th17-Mediated Antifungal Immunity in Newborn Rats

Neonatal innate immunity response in invasive candidiasis

Infections caused by Candida spp. are frequent in critically hospitalized patients, especially among premature neonates, representing one of the most common healthcare-related infections. Although there is considerable production of current knowledge about the mechanisms of immune response, aspects involved in the newborn's innate defense are not fully understood. The aim of this study was to describe the innate immune mechanisms involved in the defense of neonates against invasive candidiasis. This is an integrative literature review from the Scopus, Scifinder, Medline, Web of Science databases and the electronic libraries ScienceDirect and Scielo, in the period between 2002 and 2020, with rescue based on primary descriptor Immunity Innate plus secondary descriptors Candidiasis Invasive AND Infant Newborn. We have observed the involvement of various mechanisms in the neonatal response against invasive candidiasis, including the recognition, signaling, recruitment, and initiation of an effective immune response. These mechanisms encompass the presence of antimicrobial peptides, phagocytosis, synthesis of reactive oxygen species, inflammatory mediators, and complex cell signaling systems mediated by Pattern Recognition Receptors (PRRs). With this study, it is expected to contribute to the expansion of knowledge about the immunological mechanisms involved in the innate immune response of the newborn against disseminated infections caused by Candida species, and in the same sense, highlight the importance of this knowledge as a reflex in the decrease in mortality in the neonatal period.

Composition and dynamics of intestinal fungi during the postnatal 2 months of very low birth weight infants

It has been found that intestinal fungi play a role in the composition of the intestinal microecology and in the formation and development of the immunity during childhood. We investigated the gut fungi composition of preterm infants to analysis composition and dynamics of intestinal fungi during the postnatal 2 months of very low birth weight infants. We collected feces from 34 very low birth weight infants (VLBWI) and 28 preterm infants with birth weight >1500 g. We extracted total fungal DNA from feces and analyzed the composition of gut fungus through ITS sequencing. The fungal detectable rate in the experimental group peaked on day 3 (85.19%), then gradually decreased and started to show an increasing trend again by day 28. There were significant differences in the alpha diversity of intestinal fungus between VLBWI and controls, and the VLBWI had its own characteristics at different time points in richness and diversity. A total of 10 phylums and 342 genera were identified in all VLBWI samples. The dominant fungal phylum of the VLBWI group is Ascomycota (50.3%)and Basidiomycota (48.8%). The functional metabolic activity of the experimental group was lower than that of the control group.

CONCLUSION

The composition and abundance of VLBWI intestinal fungal showed several alterations during the first 2 months of life. The prediction of gut microbiota function suggests that intestinal metabolic function may be altered in VLBWI.

WHAT IS KNOWN

• A limited number of studies has been found that symbiont fungi may be able to calibrate host immunological responses, promote development of peripheral lymphoid organs, promote T cell responses, and even may be associated with the development of certain diseases, such as inflammatory bowel disease (IBD), NEC, and allergic diseases. However, previous studies on intestinal microecology have mainly focused on adults while neglecting the role of fungi in the gut of children due to the much lower abundance of intestinal fungi than bacteria, limitations of techniques for detecting fungi, the difficulty of obtaining samples, and the absence of largescale reference databases.

WHAT IS NEW

• In recent years, the discovery and development of fungal detection technologies such as 18s rDNA sequencing technology, Internal Transcribed Spacer(ITS), and DNA fingerprinting technology have further broadened the perspective on the impact of intestinal fungal exposure in early life.

Suppressive effect of therapeutic antibiotic regimen on antipneumococcal Th1/Th17 responses in neonatal mice

BACKGROUND

Antibiotics are commonly used in human neonates, but their impact on neonatal T cell immunity remains poorly understood. The aim of this study was to investigate the impact of the antibiotic piperacillin with the beta-lactamase inhibitor tazobactam on neonatal CD4+ and CD8+ T cell responses to Streptococcus pneumoniae.

METHODS

Splenic and lung cells were isolated from the neonatal mice receiving piperacillin and tazobactam or saline (sham) and cultured with S. pneumoniae to analyze T cell cytokine production by ELISA and flow cytometry.

RESULTS

Antibiotic exposure to neonatal mice resulted in reduced numbers of CD4+/CD8+ T cells in the spleen and lungs compared to control mice. Upon in vitro stimulation with S. pneumoniae, splenocytes and lung cells from antibiotic-exposed mice produced lower levels of IFN-γ (Th1)/IL-17A (Th17) and IL-17A cytokines, respectively. Flow cytometric analysis revealed that S. pneumoniae-stimulated splenic CD4+ T cells from antibiotic-exposed mice expressed decreased levels of IFN-γ and IL-17A compared to control mice, whereas lung CD4+ T cells produced lower levels of IL-17A. However, no significant difference was observed for IL-4 (Th2) production.

CONCLUSIONS

Neonatal mice exposure to piperacillin and tazobactam reduces the number of CD4+ and CD8+ T cells, and suppresses Th1 and Th17, but not Th2, responses to S. pneumoniae.

IMPACT

Exposure of neonatal mice with a combination of piperacillin and tazobactam reduces CD4+/CD8+ T cells in the spleen and lungs. Antibiotic exposure suppresses neonatal Th1 and Th17, but not Th2, responses to Streptococcus pneumoniae. Our findings may have important implications for developing better therapeutic strategies in the neonatal intensive care unit.

Treatment of Mouse Infants with Amoxicillin, but Not the Human Milk-Derived Antimicrobial HAMLET, Impairs Lung Th17 Responses

Emerging evidence suggests differential effects of therapeutic antibiotics on infant T cell responses to pathogens. In this study, we explored the impact of the treatment of mouse infants with amoxicillin and the human milk-derived antimicrobial HAMLET (human alpha-lactalbumin made lethal to tumor cells) on T cell responses to Streptococcus pneumoniae. Lung cells and splenocytes were isolated from the infant mice subjected to intranasal administration of amoxicillin, HAMLET, or a combination of HAMLET and amoxicillin, and cultured with S. pneumoniae to measure T cell responses. After in-vitro stimulation with S. pneumoniae, lung cells from amoxicillin- or amoxicillin plus HAMLET-treated mice produced lower levels of Th17 (IL-17A), but not Th1 (IFN-γ), cytokine than mice receiving HAMLET or PBS. IL-17A/IFN-γ cytokine levels produced by the stimulated splenocytes, on the other hand, revealed no significant difference among treatment groups. Further analysis of T cell cytokine profiles by flow cytometry showed that lung CD4+, but not CD8+, T cells from amoxicillin- or HAMLET plus amoxicillin-treated mice expressed decreased levels of IL-17A compared to those from HAMLET-exposed or control mice. Collectively, these results indicate that exposure of infant mice to amoxicillin, but not HAMLET, may suppress lung Th17 responses to S. pneumoniae.

The gut mycobiome in health, disease, and clinical applications in association with the gut bacterial microbiome assembly

The gut mycobiome (fungi) is a small but crucial component of the gut microbiome in humans. Intestinal fungi regulate host homoeostasis, pathophysiological and physiological processes, and the assembly of the co-residing gut bacterial microbiome. Over the past decade, accumulating studies have characterised the gut mycobiome in health and several pathological conditions. We review the compositional and functional diversity of the gut mycobiome in healthy populations from birth to adulthood. We describe factors influencing the gut mycobiome and the roles of intestinal fungi-especially Candida and Saccharomyces spp-in diseases and therapies with a particular focus on their synergism with the gut bacterial microbiome and host immunity. Finally, we discuss the underappreciated effects of gut fungi in clinical implications, and highlight future microbiome-based therapies that harness the tripartite relationship among the gut mycobiome, bacterial microbiome, and host immunity, aiming to restore a core gut mycobiome and microbiome and to improve clinical efficacy.

Antibiotic-induced depletion of Clostridium species increases the risk of secondary fungal infections in preterm infants

Preterm infants or those with low birth weight are highly susceptible to invasive fungal disease (IFD) and other microbial or viral infection due to immaturity of their immune system. Antibiotics are routinely administered in these vulnerable infants in treatment of sepsis and other infectious diseases, which might cause perturbation of gut microbiome and hence development of IFD. In this study, we compared clinical characteristics of fungal infection after antibiotic treatment in preterm infants. As determined by 16S rRNA sequencing, compared with non-IFD patients with or without antibiotics treatment, Clostridium species in the intestinal tracts of patients with IFD were almost completely eliminated, and Enterococcus were increased. We established a rat model of IFD by intraperitoneal inoculation of C. albicans in rats pretreated with meropenem and vancomycin. After pretreatment with antibiotics, the intestinal microbiomes of rats infected with C. albicans were disordered, as characterized by an increase of proinflammatory conditional pathogens and a sharp decrease of Clostridium species and Bacteroides. Immunofluorescence analysis showed that C. albicans-infected rats pretreated with antibiotics were deficient in IgA and IL10, while the number of Pro-inflammatory CD11c⁺ macrophages was increased. In conclusion, excessive use of antibiotics promoted the imbalance of intestinal microbiome, especially sharp decreases of short-chain fatty acids (SCFA)-producing Clostridium species, which exacerbated the symptoms of IFD, potentially through decreased mucosal immunomodulatory molecules. Our results suggest that inappropriate use of broad-spectrum antibiotics may promote the colonization of invasive fungi. The results of this study provide new insights into the prevention of IFD in preterm infants.

Temporal changes in gastrointestinal fungi and the risk of autoimmunity during early childhood: the TEDDY study

Fungal infections are a major health problem that often begin in the gastrointestinal tract. Gut microbe interactions in early childhood are critical for proper immune responses, yet there is little known about the development of the fungal population from infancy into childhood. Here, as part of the TEDDY (The Environmental Determinants of Diabetes in the Young) study, we examine stool samples of 888 children from 3 to 48 months and find considerable differences between fungi and bacteria. The metagenomic relative abundance of fungi was extremely low but increased while weaning from milk and formula. Overall fungal diversity remained constant over time, in contrast with the increase in bacterial diversity. Fungal profiles had high temporal variation, but there was less variation from month-to-month in an individual than among different children of the same age. Fungal composition varied with geography, diet, and the use of probiotics. Multiple Candida spp. were at higher relative abundance in children than adults, while Malassezia and certain food-associated fungi were lower in children. There were only subtle fungal differences associated with the subset of children that developed islet autoimmunity or type 1 diabetes. Having proper fungal exposures may be crucial for children to establish appropriate responses to fungi and limit the risk of infection: the data here suggests those gastrointestinal exposures are limited and variable.