Bacterial pathogens in Xpert MTB/RIF Ultra-negative sputum samples of patients with presumptive tuberculosis in a high TB burden setting: a 16S rRNA analysis

In patients with presumptive tuberculosis (TB) in whom the diagnosis of TB was excluded, understanding the bacterial etiology of lower respiratory tract infections (LRTIs) is important for optimal patient management. A secondary analysis was performed on a cohort of 250 hospitalized patients with symptoms of TB. Bacterial DNA was extracted from sputum samples for Illumina 16S rRNA sequencing to identify bacterial species based on amplicon sequence variant level. The bacterial pathogen most likely to be responsible for the patients' LRTI could only be identified in a minority (6.0%, 13/215) of cases based on 16S rRNA amplicon sequencing: Mycoplasma pneumoniae (n = 7), Bordetella pertussis (n = 2), Acinetobacter baumanii (n = 2), and Pseudomonas aeruginosa (n = 2). Other putative pathogens were present in similar proportions of Xpert Ultra-positive and Xpert Ultra-negative sputum samples. The presence of Streptococcus (pseudo)pneumoniae appeared to increase the odds of radiological abnormalities (aOR 2.5, 95% CI 1.12-6.16) and the presence of S. (pseudo)pneumoniae (aOR 5.31, 95% CI 1.29-26.6) and Moraxella catarrhalis/nonliquefaciens (aOR 12.1, 95% CI 2.67-72.8) increased the odds of 6-month mortality, suggesting that these pathogens might have clinical relevance. M. pneumoniae, B. pertussis, and A. baumanii appeared to be the possible causes of TB-like symptoms. S. (pseudo)pneumoniae and M. catarrhalis/nonliquefaciens also appeared of clinical relevance based on 16S rRNA amplicon sequencing. Further research using tools with higher discriminatory power than 16S rRNA sequencing is required to develop optimal diagnostic and treatment strategies for this population.IMPORTANCEThe objective of this study was to identify possible bacterial lower respiratory tract infection (LRTI) pathogens in hospitalized patients who were initially suspected to have TB but later tested negative using the Xpert Ultra test. Although 16S rRNA was able to identify some less common or difficult-to-culture pathogens such as Mycoplasma pneumoniae and Bordetella pertussis, one of the main findings of the study is that, in contrast to what we had hypothesized, 16S rRNA is not a method that can be used to assist in the management of patients with presumptive TB having a negative Xpert Ultra test. Even though this could be considered a negative finding, we believe it is an important finding to report as it highlights the need for further research using different approaches.

Positioning the preventive potential of microbiome treatments for cystic fibrosis in the context of current therapies

Antibiotics and cystic fibrosis transmembrane conductance regulator (CFTR) modulators play a pivotal role in cystic fibrosis (CF) treatment, but both have limitations. Antibiotics are linked to antibiotic resistance and disruption of the airway microbiome, while CFTR modulators are not widely accessible, and structural lung damage and pathogen overgrowth still occur. Complementary strategies that can beneficially modulate the airway microbiome in a preventive way are highly needed. This could be mediated via oral probiotics, which have shown some improvement of lung function and reduction of airway infections and exacerbations, as a cost-effective approach. However, recent data suggest that specific and locally administered probiotics in the respiratory tract might be a more targeted approach to prevent pathogen outgrowth in the lower airways. This review aims to summarize the current knowledge on the CF airway microbiome and possibilities of microbiome treatments to prevent bacterial and/or viral infections and position them in the context of current CF therapies.

Salivary microbiome of healthy women of reproductive age

IMPORTANCE

The salivary microbiome has been proven to play a crucial role in local and systemic diseases. Moreover, the effects of biological and lifestyle factors such as oral hygiene and smoking on this microbial community have already been explored. However, what was not yet well understood was the natural variation of the saliva microbiome in healthy women and how this is associated with specific use of hormonal contraception and with the number of different sexual partners with whom microbiome exchange is expected regularly. In this paper, we characterized the salivary microbiome of 255 healthy women of reproductive age using an in-depth questionnaire and self-sampling kits. Using the large metadata set, we were able to investigate the associations of several host-related and lifestyle variables with the salivary microbiome profiles. Our study shows a high preservation between individuals.

Development of a live biotherapeutic throat spray with lactobacilli targeting respiratory viral infections

Respiratory viruses such as influenza viruses, respiratory syncytial virus (RSV), and coronaviruses initiate infection at the mucosal surfaces of the upper respiratory tract (URT), where the resident respiratory microbiome has an important gatekeeper function. In contrast to gut-targeting administration of beneficial bacteria against respiratory viral disease, topical URT administration of probiotics is currently underexplored, especially for the prevention and/or treatment of viral infections. Here, we report the formulation of a throat spray with live lactobacilli exhibiting several in vitro mechanisms of action against respiratory viral infections, including induction of interferon regulatory pathways and direct inhibition of respiratory viruses. Rational selection of Lactobacillaceae strains was based on previously documented beneficial properties, up-scaling and industrial production characteristics, clinical safety parameters, and potential antiviral and immunostimulatory efficacy in the URT demonstrated in this study. Using a three-step selection strategy, three strains were selected and further tested in vitro antiviral assays and in formulations: Lacticaseibacillus casei AMBR2 as a promising endogenous candidate URT probiotic with previously reported barrier-enhancing and anti-pathogenic properties and the two well-studied model strains Lacticaseibacillus rhamnosus GG and Lactiplantibacillus plantarum WCFS1 that display immunomodulatory capacities. The three strains and their combination significantly reduced the cytopathogenic effects of RSV, influenza A/H1N1 and B viruses, and HCoV-229E coronavirus in co-culture models with bacteria, virus, and host cells. Subsequently, these strains were formulated in a throat spray and human monocytes were employed to confirm the formulation process did not reduce the interferon regulatory pathway-inducing capacity. Administration of the throat spray in healthy volunteers revealed that the lactobacilli were capable of temporary colonization of the throat in a metabolically active form. Thus, the developed spray with live lactobacilli will be further explored in the clinic as a potential broad-acting live biotherapeutic strategy against respiratory viral diseases.

The nasal mutualist Dolosigranulum pigrum AMBR11 supports homeostasis via multiple mechanisms

Comparing the nasal microbiome of healthy individuals and chronic rhinosinusitis (CRS) patients revealed Dolosigranulum pigrum as a species clearly associated with nasal health, although isolates obtained from healthy individuals are scarce. In this study, we explored the properties of this understudied lactic acid bacterium by integrating comparative genomics, habitat mining, cultivation, and functional characterization of interaction capacities. Mining 10.000 samples from the Earth Microbiome Project of 17 habitat types revealed that Dolosigranulum is mainly associated with the human nasal cavity. D. pigrum AMBR11 isolated from the nose of a healthy individual exerted antimicrobial activity against Staphylococcus aureus, decreased proinflammatory cytokine production in airway epithelial cells, and Galleria mellonella larvae mortality induced by this important nasal pathobiont. Furthermore, the strain protected the nasal barrier function in a mouse model using interleukin-4 as disruptive cytokine. Hence, D. pigrum AMBR11 is a mutualist with high potential as topical live biotherapeutic product.

Cotton and Surgical Face Masks in Community Settings: Bacterial Contamination and Face Mask Hygiene

During the current COVID-19 pandemic, the use of face masks has become increasingly recommended and even mandatory in community settings. To evaluate the risk of bacterial cross-contamination, this study analyzed the bacterial bioburden of disposable surgical masks and homemade cotton masks, and surveyed the habits and face mask preferences of the Flemish population. Using culture approaches and 16S rRNA gene amplicon sequencing, we analyzed the microbial community on surgical and/or cotton face masks of 13 healthy volunteers after 4 h of wearing. Cotton and surgical masks contained on average 1.46 × 10⁵ CFU/mask and 1.32 × 10⁴ CFU/mask, respectively. Bacillus, Staphylococcus, and Acinetobacter spp. were mostly cultured from the masks and 43% of these isolates were resistant to ampicillin or erythromycin. Microbial profiling demonstrated a consistent difference between mask types. Cotton masks mainly contained Roseomonas, Paracoccus, and Enhydrobacter taxa and surgical masks Streptococcus and Staphylococcus. After 4 h of mask wearing, the microbiome of the anterior nares and the cheek showed a trend toward an altered beta-diversity. According to dedicated questions in the large-scale Corona survey of the University of Antwerp with almost 25,000 participants, only 21% of responders reported to clean their cotton face mask daily. Laboratory results indicated that the best mask cleaning methods were boiling at 100°C, washing at 60°C with detergent or ironing with a steam iron. Taken together, this study suggests that a considerable number of bacteria, including pathobionts and antibiotic resistant bacteria, accumulate on surgical and even more on cotton face masks after use. Based on our results, face masks should be properly disposed of or sterilized after intensive use. Clear guidelines for the general population are crucial to reduce the bacteria-related biosafety risk of face masks, and measures such as physical distancing and increased ventilation should not be neglected when promoting face mask use.

Lactobacilli Have a Niche in the Human Nose

Although an increasing number of beneficial microbiome members are characterized for the human gut and vagina, beneficial microbes are underexplored for the human upper respiratory tract (URT). In this study, we demonstrate that taxa from the beneficial Lactobacillus genus complex are more prevalent in the healthy URT than in patients with chronic rhinosinusitis (CRS). Several URT-specific isolates are cultured, characterized, and further explored for their genetic and functional properties related to adaptation to the URT. Catalase genes are found in the identified lactobacilli, which is a unique feature within this mostly facultative anaerobic genus. Moreover, one of our isolated strains, Lactobacillus casei AMBR2, contains fimbriae that enable strong adherence to URT epithelium, inhibit the growth and virulence of several URT pathogens, and successfully colonize nasal epithelium of healthy volunteers. This study thus demonstrates that specific lactobacilli are adapted to the URT and could have a beneficial keystone function in this habitat.

Probiotic nasal spray development by spray drying

The upper respiratory tract (URT) is the main entrance point for many viral and bacterial pathogens, and URT infections are among the most common infections in the world. Recent evidences by our own group and others imply the importance of lactobacilli as gatekeepers of a healthy URT. However, the benefits of putting health-promoting microbes or potential probiotics, such as these URT lactobacilli, in function of URT disease control and prevention is underestimated, among others because of the absence of adequate formulation modalities. Therefore, this study entails important aspects in probiotic nasal spray development with a novel URT-derived probiotic strain by spray drying. We report quantitative and qualitative analysis of several spray-dried formulations, i.e. powders for reconstitution, based on disaccharide or sugar alcohol combinations with a polymer, including their long-term stability. Four formulations with the highest survival of >10⁹ (Colony Forming Units) CFU/g after 28 weeks were further examined upon reconstitution which confirmed sufficiency of one bottle/dosage form during 7 days and rheological properties of shear-thinning. Tests also demonstrated maintained viability and cell morphology overall upon spraying through a nasal spray bottle in all 4 formulations. Lastly, application suitability in terms of high adherence to Calu-3 cells and antimicrobial activity against common URT pathogens was demonstrated and was not impacted neither by powder production process nor by spraying of reconstituted powder through a nasal spray device.