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Background Colonization of the body is an important step in Staphylococcus aureus infection. S. aureus colonizes skin and mucous membranes in humans and several animal species. One important ecological niche of S. aureus is the anterior nares. More than 60% of the S. aureus in the nose are found in vestibulum nasi. Our aim was to describe the localization of S. aureus in nasal tissue from healthy carriers. Methods Punch skin biopsies were taken from vestibulum nasi from healthy volunteers ( S. aureus carriers and non−/intermittent carriers, n  = 39) attending the population-based Tromsø 6 study. The tissue samples were processed as frozen sections before immunostaining with a specific S. aureus antibody, and finally evaluated by a confocal laser-scanning microscope. Results Our results suggest that S. aureus colonize both the upper and lower layers of the epidermis within the nasal epithelium of healthy individuals. The number of S. aureus in epidermis was surprisingly low. Intracellular localization of S. aureus in nasal tissue from healthy individuals was also detected. Conclusions Knowledge of the exact localization of S. aureus in nasal tissue is important for the understanding of the host responses against S. aureus. Our results may have consequences for the eradication strategy of S. aureus in carriers, and further work can provide us with tools for targeted prevention of S. aureus colonisation and infection.

Transient receptor potential (TRP) channels, neuronal stimulations widely known to be associated with thermal responses, pain induction, and osmoregulation, have been shown in recent studies to have underlying mechanisms associated with inflammatory responses. The role of TRP channels on inflammatory milieu during bacterial infections has been widely demonstrated. It may vary among types of channels/pathogens, however, and it is not known how TRP channels function during pneumococcal infections. Streptococcus pneumoniae can cause severe infections such as pneumonia, bacteremia, and meningitis, with systemic inflammatory responses. This study examines the role of TRP channels (TRPV1 and TRPV4) for pneumococcal nasal colonization and subsequent development of invasive pneumococcal disease in a mouse model. Both TRPV1 and TRPV4 channels were shown to be related to regulation of the development of pneumococcal diseases. In particular, the influx of neutrophils (polymorphonuclear cells) in the nasal cavity and the bactericidal activity were significantly suppressed among TRPV4 knockout mice. This may lead to severe pneumococcal pneumonia, resulting in dissemination of the bacteria to various organs and causing high mortality during influenza virus coinfection. Regulating host immune responses by TRP channels could be a novel strategy against pathogenic microorganisms causing strong local/systemic inflammation.

Objective This study aims to evaluate the clinical significance of multiple intraoperative sterilizations and bacteriological surveillance in reducing postoperative intracranial infections during transnasal endoscopic skull base surgery. Methods This study collected clinical data from 1002 patients undergoing transnasal endoscopic skull base surgery between January 2016 and January 2024. Patients were divided into a routine sterilization group (367 patients) and a multiple sterilization group (635 patients) based on the sterilization method. The rates of intracranial infections were compared between the two groups. Additionally, intraoperative bacteriological monitoring before and after sterilization was performed on some patients in the multiple sterilization group to analyze bacterial colonization and its relationship with intracranial infections. Results In the routine sterilization group of 367 patients, 21 patients (5.72%) developed intracranial infections. Of these, 20 patient had cerebrospinal fluid leakage during surgery. In the multiple sterilization group of 635 patients, 14 patients (2.20%) developed intracranial infections, all associated with cerebrospinal fluid leakage during surgery. Among the 96 patients who underwent bacteriological monitoring, 59 patients and 11 patients had definitive positive bacterial cultures before and after nasal disinfection, respectively. Additionally, 18 patients and 5 patients had definitive positive bacterial cultures before and after sphenoid sinus disinfection, respectively. One patient developed an intracranial infection caused by the same pathogens cultured from the nasal cavity. Conclusion Most pathogenic bacteria causing postoperative intracranial infections in patients undergoing transnasal endoscopic skull base surgery originate from nasal colonization. Multiple intraoperative sterilizations can reduce the incidence of intracranial infections in patients with high-risk factors for intraoperative cerebrospinal fluid leakage.

Staphylococcus aureus acts both as a colonizing commensal bacterium and invasive pathogen. Nasal colonization is associated with an increased risk of infection caused by the identical strain. In patients with atopic dermatitis (AD), the degree of S. aureus colonization is associated with the severity of the disease. Here, we comparatively analyzed the in vivo transcriptional profile of S. aureus colonizing the nose and non-diseased skin (non-lesional skin) as opposed to the diseased skin (lesional skin—defined here as infection) of 12 patients with AD. The transcriptional profile during the asymptomatic colonization of the nose closely resembled that of the lesional skin samples for many of the genes studied, with an elevated expression of the genes encoding adhesion-related proteins and proteases. In addition, the genes that modify and remodel the cell wall and encode proteins that facilitate immune evasion showed increased transcriptional activity. Notably, in a subgroup of patients, the global virulence regulator Agr (accessory gene regulator) and downstream target genes were inactive during nasal colonization but upregulated in the lesional and non-lesional skin samples. Taken together, our results demonstrate a colonization-like transcriptional profile on diseased skin and suggest a role for the peptide quorum sensing system Agr during the transition from asymptomatic nasal colonization to skin colonization/infection.

Background Atopic dermatitis (AD) patients have high rates of colonization by Staphylococcus aureus , which has been associated with worsening of the disease. This study characterized Staphylococcu s spp isolates recovered from nares and feces of pediatric patients with AD in relation to antimicrobial susceptibility, staphylococcal cassette chromosome mec (SCC mec ) type, presence of pvl genes and clonality. Besides, gut bacterial community profiles were compared with those of children without AD. Results All 55 AD patients evaluated had colonization by Staphylococcus spp. Fifty-three (96.4%) patients had colonization in both clinical sites, whereas one patient each was not colonize in the nares or gut. Staphylococcus aureus was identified in the nostrils and feces of 45 (81.8%) and 39 (70.9%) patients, respectively. Methicillin-resistant Staphylococcus spp. isolates were found in 70.9% of the patients, and 24 (43.6%) had methicillin-resistant S. aureus (MRSA). S. aureus (55.6%) and S. epidermidis (26.5%) were the major species found. The prevalent lineages of S. aureus were USA800/SCC mec IV (47.6%) and USA1100/SCC mec IV (21.4%), and 61.9% of the evaluated patients had the same genotype in both sites. Additionally, gut bacterial profile of AD patients exhibits greater dissimilarity from the control group than it does among varying severities of AD. Conclusions High rates of nasal and intestinal colonization by S. aureus and methicillin-resistant staphylococci isolates were found in AD patients. Besides, gut bacterial profiles of AD patients were distinctly different from those of the control group, emphasizing the importance of monitoring S. aureus colonization and gut microbiome composition in AD patients.

Human nasal microbiota often includes highly pathogenic members, many of which are antimicrobial resistance threats, e.g., methicillin-resistant Staphylococcus aureus and drug-resistant Streptococcus pneumoniae . Preventing colonization by nasal pathobionts decreases infections and transmission. In contrast, nasal microbiome studies identify candidate beneficial bacteria that might resist pathobiont colonization, e.g., Dolosigranulum pigrum . Learning how these microbionts interact with the nasal epithelium and identifying new means to reduce pathobiont colonization are key goals in the field. As a tool to advance this research, we developed human nasal epithelial organoids (HNOs) differentiated at an air-liquid interface as a new model system of bacterial nasal colonization. HNOs accurately represent the mucosal surface of the human nasal passages, enabling exploration of bacterial-epithelial interactions, which is important since the epithelium is an instigator of the initial innate immune response to bacteria. Here, we identified differential epithelial cytokine responses to these three bacteria, setting the stage for future research.

Staphylococci are commensals of human skin and mucous membranes, but some species can also cause serious infections. Host niches during both colonization and infection differ greatly and are characterized by specific environmental conditions (pH, temperature, oxygen, nutrient availability, and microbiota) that can affect gene expression and virulence of microbes. To successfully occupy extremely different habitats at different anatomical sites, Staphylococci are equipped with a variety of regulatory elements that allow specific adaptation to the changing environments. Not surprisingly, gene expression in vivo can be significantly different from the expression pattern observed in vitro . Niche specific stimuli that influence the bacterial ability to either cause infection or maintain colonization are only partially understood. Here, we describe habitat specific conditions and discuss the available literature analyzing staphylococcal gene expression, focusing on Staphylococcus aureus and S. epidermidis during colonization of the nose and skin.

Nasally colonized staphylococci carry antibiotic resistance genes and may lead to serious opportunistic infections. We are investigating nasal carriage of Staphylococcus aureus and Staphylococci other than S. aureus (SOSA) among young volunteers in Egypt to determine their risk potential. Nasal swabs collected over 1 week in June 2019 from 196 volunteers were cultured for staphylococcus isolation. The participants were interviewed to assess sex, age, general health, hospitalization and personal hygiene habits. Identification was carried out using biochemical tests and VITEK 2 automated system. Disc diffusion and minimum inhibitory concentration tests were performed to determine antibiotic susceptibility. Screening for macrolide resistance genes ( ermA, ermB, ermC, ermT and msrA ) was performed using polymerase chain reaction. Thirty four S. aureus and 69 SOSA were obtained. Multi-drug resistance (MDR) was detected among most staphylococcal species, ranging from 30.77% among S. hominis to 50% among S. epidermidis . Phenotypic resistance to all tested antibiotics, except for linezolid, was observed. Susceptibility to rifampicin, vancomycin and teicoplanin was highest. ermB showed the highest prevalence among all species (79.41% and 94.2% among S. aureus and SOSA, respectively), and constitutive macrolide-lincosamide-streptogramin B (MLS B ) resistance was equally observed in S. aureus and SOSA (11.11% and 16.22%, respectively), whereas inducible MLS B resistance was more often found in S. aureus (77.78% and 43.24%, respectively). The species or resistance level of the carried isolates were not significantly associated with previous hospitalization or underlying diseases. Although over all colonization and carriage of resistance genes are within normal ranges, the increased carriage of MDR S. aureus is alarming. Also, the fact that many macrolide resitance genes were detected should be a warning sign, particularly in case of MLS B inducible phenotype. More in depth analysis using whole genome sequencing would give a better insight into the MDR staphylococci in the community in Egypt.

Background The COVID-19 pandemic has dramatically impacted in patients from Intensive Care Units (ICUs), making them more vulnerable to infection/colonization by clinically relevant pathogens. However, little is known about the  Staphylococcus aureus  isolates that colonized these patients during the pandemic. Methods Consecutive  S. aureus  isolates from surveillance swabs of patients of two ICUs of a hospital in Rio de Janeiro, between September 2020 and September 2021, were evaluated for phenotypic antimicrobial resistance. Methicillin-resistant  S. aureus  (MRSA) isolates were evaluated for resistance and virulence genes, biofilm production, and their genotypic profiles. Medical records were accessed for clinical and demographic data. Results Among 255 patients colonized by  S. aureus , 79 (30.9%) were in the cICU (COVID-19 ICU) and 176 (69.1%) in the ncICU (non-COVID-19 ICU). COVID-19 patients made greater use of antimicrobials during hospitalization ( p <  0.05). Higher rates of resistance for erythromycin and clindamycin, as well as the inducible macrolide-lincosamide-streptogramin B resistance phenotype and multidrug resistance were found in cICU isolates ( p <  0.05). An overall rate of 36.5% of MRSA isolates was detected, with 41.7% in cICU and 34% in ncICU ( p  = 0.22). SCC mec  types II (22.6%) and IV (71%) were the most found, and the latter was more frequent in the ncICU ( p <  0.01). More than 50% of the isolates carried the resistance genes  erm (C),  msr (A),  mrs (B),  mph (C),  aph (3’)-III3a and  smr , and the virulence genes  ica A,  sas G,  ebp S,  scn , egc cluster,  fnbp B and  cna . The cICU presented isolates that primarily carried the  erm (C),  smr , and  cna  genes and that showed strong biofilm production ( p <  0.05). Clonal complex (CC) 5 was prevalent (65.6%) and associated with the hospital clones USA800/ST5-IV and USA100/ST105-II, which were most found in ncICU and cICU, respectively ( p <  0.05). Community MRSA comprised 31.2% of isolates and mainly included the USA300/ST8-IV lineage (18.3%), with all isolates carrying the  pvl  genes. Conclusions The significant impact on antimicrobial resistance rates and the emergence of virulent lineages among  S. aureus  isolates during the COVID-19 pandemic highlights the close relationship between this disease and antimicrobial resistance and the importance of constant microbiological surveillance to reduce the risks associated with future pandemics.