Background Enteral feeding via percutaneous endoscopic gastrostomy (PEG) is commonly used for patients requiring long-term nutritional support. However, PEG insertion carries a risk of infection, including methicillin-resistant Staphylococcus aureus (MRSA) peristomal infections. This systematic review and meta-analysis aimed to evaluate the association between MRSA colonization and the risk of PEG-related infections. Methods A systematic search was conducted in four major databases-Embase, Medline, Cochrane, and Scopus-focusing on studies reporting MRSA colonization and PEG-related infections. Data were analyzed using RevMan v5.3. Odds ratios (OR) were calculated for dichotomous outcomes using a random-effects model. Statistical significance was defined as p < 0.05. Heterogeneity was assessed using the I² statistic. Results Five studies encompassing 286 patients were included in the meta-analysis. Among them, 77 patients were nasopharyngeal MRSA-positive, and 209 were MRSA-negative. MRSA colonization was significantly associated with an increased risk of PEG-related peristomal infection (OR: 24.31; 95% CI: 5.20-113.65; p < 0.0001). Heterogeneity among studies was low, supporting the robustness of the findings. Conclusion Nasopharyngeal MRSA colonization is strongly associated with a higher risk of PEG site infection. These findings highlight the importance of MRSA screening and consideration of colonization status prior to PEG tube insertion. Enhanced infection control strategies should be implemented in MRSA-positive patients to mitigate the risk of complications. Further research is warranted to determine the most effective preventive measures tailored to MRSA-colonized individuals undergoing PEG placement.

The effect of pneumococcal conjugate vaccine and pneumococcal polysaccharide vaccine on nasopharyngeal colonisation following human infection challenge with serotype 3 and serotype 6B (PREVENTING PNEUMO 2): a double-masked, randomised, controlled, phase 4 trial.

Streptococcus pneumoniae remains a major cause of bacterial disease in young children, with increased risk and morbidity in children exposed to HIV but uninfected (CEHU) and children living with HIV (CLWH). This study assessed the persistence of vaccine-specific antibodies, opsonophagocytic activity (OPA) and nasopharyngeal carriage of S. pneumoniae and Haemophilus influenzae in HIV-unexposed children, CEHU and CLWH. HIV-unexposed children, CEHU and CLWH who initially received a 10-valent pneumococcal polysaccharide protein D-conjugate vaccine 3-dose primary schedule at 6, 10 and 14 weeks with a booster at 9 months (3 + 1) were followed up at 3, 4 and 5 years to measure serum IgG concentrations, OPA and nasopharyngeal colonization. Geometric mean concentrations (GMCs) and titers, along with the prevalence of colonization, are reported for each group. Compared with HIV-unexposed children, CLWH had similar antibody concentrations for all serotypes at each timepoint except at 4 years where GMCs were lower for 6B and at 5 years where GMCs were lower for 6A. OPA titers were lower for 6B at 3 years and lower for 4B at 4 and 5 years in CLWH compared with HIV-unexposed children. Comparing CEHU to HIV-unexposed children, both study groups had similar GMCs and OPA titers for all serotypes during the study period. Prevalence of nasopharyngeal colonization of S. pneumoniae and H. influenzae was similar amongst the 3 study groups. There was no association between HIV exposure or infection and antibody persistence or colonization at 3, 4 and 5 years of age.

Here, we examine immune signaling pathways affecting the duration of primary nasopharyngeal colonization byStreptococcus pneumoniae(Spn), the first step in its pathogenesis.Spncolonization which lasts days to weeks in WT mice was persistent (>6 months) in the absence of IL-17RA-signaling. RNA-seq analysis confirmed the role of IL-17RA signaling in neutrophil-associated pathways. Rather than driving neutrophil specific chemokine expression, IL-17RA-signaling was required to replenish neutrophils in nasal tissue that were otherwise depleted during infection. Enhanced neutrophil trafficking correlated with IL-17RA-dependent expression of endothelial cell adhesion molecules that promote neutrophil trafficking from the circulation into nasal tissue. Persistent colonization was also observed in mice lacking IL-1R-signaling. Recognition of IL-1-family cytokines, however, was not necessary for the expression of IL-17A or neutrophil recruitment. Instead, IL-1R-signaling was associated with the activation of neutrophils in nasal tissue that displayed increased levels of the surface marker CD11b, an important receptor for the complement-opsonized phagocytosis ofSpn. Our findings provide insight into the requirement for sustained neutrophil presence and activity to prevent persistent mucosal infection by a leading opportunistic mucosal pathogen.Author SummaryColonization of the upper airway by Streptococcus pneumoniae (Spn) is common and often asymptomatic, particularly in early life, yet prolonged colonization increases the risk of transmission and invasive disease. Despite its importance, the immune mechanisms that prevent long-term persistence ofSpnin the upper airway are not fully understood. In this study, we investigated how two immune signaling pathways, the IL-17RA and IL-1R pathways, contribute to preventing persistentSpncolonization. Using a mouse model, we found that the IL-17RA pathway supports continued replenishment of neutrophils into nasal tissue by promoting expression of molecules that allow these cells to exit the bloodstream and enter the nasal tissue. In contrast, the IL-1R pathway activates neutrophils in a way that makes them more effective at clearingSpn. Loss of either pathway resulted in persistentSpncolonization, with an additive effect seen when both pathways were removed. Collectively, our results highlight how two distinct immune pathways cooperate to control pneumococcal colonization by sustaining neutrophil recruitment and function.

BackgroundS. pneumoniae (SP) serotypes 15B and 15C combined are amongst the most frequent causative agents of invasive pneumococcal disease and nasopharyngeal colonization in the post PCV13 era. The introduction of PCV20 included serotype 15B polysaccharide conjugates in its formulation, but not 15C. It remains unclear whether including 15B polysaccharide with its dominant O-acetyl epitope will elicit protection against both serotypes.Current practices to differentiate between serotypes relay on conventional methods and serotype determination with specific antisera, limiting our ability to evaluate serotype in the culture negative samples. Current molecular serotyping strategy, published by CDC, identifies up to 20 vaccine serotypes, including serotype 15B, but do not differentiate 15B from 15C. The principal difference between serotypes 15B and 15C is the presence of an O-acetyl group on the pentasaccharide-repeating unit of 15B polysaccharide. The O-acetylation is controlled by the number of AT pairs; with 8 pairs turning on O-acetylation (15B) and 7 or 9 turning off acetylation (15C). An accurate and rapid serotyping method is essential to differentiate serotypes 15B and 15C, and evaluate whether PCV20 will provide protection against both serotypes.MethodsDNA extraction of SP negative samples were performed. We isolated DNA from known strains of 15B and 15C to serve as positive controls. LytA and PiaB genes were used to confirm SP by QRT-PCR, followed by molecular serotyping using serotype specific primers and probes. Samples positive for 15 BC were further amplified by PCR using O-Acetyl Transferase gene specific primers. PCR DNA was purified and submitted for the sequencing with O-acetyl transferase specific primers.ResultsA 100% correlation of PCRSeqTyping results was observed using sequencing results with positive controls. Eight culture negative samples were identified correctly as 15B (n=4) or 15C (n=4ConclusionWe describe a PCRSeqTyping assay to differentiate 15B from 15C that is accurate and rapid, with high reproducibility. It is significant as it can allow differentiation of 15B and 15C on culture negative specimens. This assay will enhance surveillance studies and enable researchers to better determine if PCV20 provides protection against both 15B and 15C.DisclosuresAll Authors: No reported disclosures

Abstract Background Nasopharyngeal (NP) samples are considered the gold standard for detecting Streptococcus pneumoniae (SPN) colonization in children, while oropharyngeal (OP) sampling is more common in adults. The 2013 WHO guidelines suggest that in children OP cultures provide minimal additional yield to NP cultures. However, NP samples alone may underestimate colonization and serotype prevalence. While molecular methods are increasingly used, data on their reliability for OP samples in children is limited. We characterized the NP and OP pneumococcal colonization rate and serotype distribution in children. Methods This retrospective study used residual paired NP/OP samples, obtained as part of clinical care, from children &amp;lt; 18 years at Texas Children’s Hospital in December 2024. Pneumococcal colonization was assessed using a multiplex qPCR assay targeting lytA, piaB, and SP2020 genes. Samples were run in duplicates, and positivity was defined as a Ct &amp;lt; 35 for ≥ 2 target genes. Samples with a Ct ≤ 32 (indicating a DNA concentration sufficient for the downstream PCR assays) underwent molecular serotyping using 8 sequential multiplex PCR assays. Demographic and clinical data were extracted from medical records. Results Seventy children with paired NP/OP samples were identified (Table 1). A total of 44 samples (18 NP and 26 OP) from 30 children were SPN positive, a 42.9% colonization rate. Positive concordance between NP and OP samples was observed in 20% of children, while 57.1% showed negative concordance (Figure). Colonized children were younger and more likely to test positive for respiratory viruses (Table 1). The characteristics of colonized children based on positive specimens are shown in Table 2. Fifteen different serotypes were identified, the most common from sites combined were 35B (n=6), 24F (n=4), 34 (n=4), and 7C (n=4). Co-detection of serotypes as well as serotypes 3, 4, 9V, 10A, sg18, 23B, 24F and 33A/F were noted in OP samples only. (Table 3). Conclusion The addition of OP to NP samples identified 17.1% more SPN colonization and a broader serotype distribution. However, OP colonization results should be interpreted cautiously, as some serotypes (e.g. 4, 9V) are rare in children, and may reflect cross-reaction with non-pneumococcal streptococci carrying pneumococcal capsular genes. Disclosures Liset Olarte, MD, MSc, GSK: Grant/Research Support|Merck, Sharpe &amp; Dohme: Grant/Research Support|Sanofi: Grant/Research Support|UpToDate - WoltersKluwer: Royalties

BackgroundCarriage of Neisseria lactamica (Nlac), a harmless nasopharyngeal commensal, correlates inversely with carriage of Neisseria meningitidis (Nmen), a common cause of meningitis and sepsis outbreaks in sub-Saharan Africa. Nasally administered lyophilized Nlac (LyoNlac) might interrupt carriage and transmission of Nmen in sub-Saharan settings without requirement of a cold chain, but whether LyoNlac can establish colonization is undetermined.MethodsHealthy adult volunteers aged 18–45 years were inoculated intranasally with 104–107 colony forming units (CFU) of reconstituted, lyophilized Nlac strain Y92-1009 (LyoNlac) in 2 dose-ranging controlled human infection studies conducted in the United Kingdom and Mali. Safety was measured as a primary objective. Secondary objectives included the dose achieving ≥70% colonization rates for each setting, colonization kinetics, and serological responses. Both trials were registered with ClinicalTrials.gov (United Kingdom: NCT04135053, Mali: NCT04665791) and are complete.ResultsIntranasal inoculation with LyoNlac was well tolerated with no significant safety concerns. In the United Kingdom, 105 CFU yielded 100% colonization (n = 10/10) while in Mali, 107 CFU achieved 65% colonization (n = 13/20). An increase in Nlac- and Nmen-specific IgG from pre-challenge to day 28 post-challenge was observed in colonized participants—median fold-change [interquartile range] United Kingdom: Nlac 2.24 [1.37–4.24], Nmen 1.39 [1.20–3.70] and Mali: Nlac 1.31 [1.04–1.94], Nmen 1.32 [0.99–1.73]. No significant seroconversion occurred in non-colonized participants.ConclusionsIntranasal inoculation with LyoNlac was safe and induced immunogenic nasopharyngeal colonization in healthy adults in the United Kingdom and Mali. Future clinical trials to determine whether LyoNlac reduces meningococcal carriage and transmission in the meningitis belt are warranted.

Streptococcus pneumoniae commonly colonizes the nasopharynx of children asymptomatically, but under certain conditions, it can cause invasive diseases such as pneumonia. The mechanisms driving this transition are not fully understood. In this study, we utilized a pneumococcal nasopharyngeal colonization model and subsequent respiratory syncytial virus (RSV) infection to investigate the mechanism of bacterial expansion. We observed loads in nasal and bronchoalveolar lavage fluids. We also measured the expression of the growth arrest-specific protein 6 (Gas6) in the nasal lavage. We further assessed the effect of selective inhibition of the Axl receptor using BGB324 on RSV-mediated growth. Macrophage phenotypes were analyzed in vivo using M1-like markers and confirmed in vitro using Gas6-treated bone marrow-derived macrophages. We observed increased loads in nasal and bronchoalveolar lavage fluids following RSV infection. RSV infection also upregulated the expression of Gas6 in the nasal lavage, and selective inhibition of the Axl receptor using BGB324 effectively attenuated RSV-mediated growth. In addition, compared with mice with colonization alone, mice with subsequent RSV infection exhibited decreased expression of M1-like macrophage markers in the nasal cavity. In vitro assays confirmed that Gas6 suppressed M1 macrophage polarization, fostering an immunosuppressive microenvironment conducive to bacterial proliferation. Our findings reveal that the RSV infection-induced Gas6/Axl axis facilitates pneumococcal overgrowth by modulating macrophage function. Targeting the RSV-induced Gas6/Axl axis or modulating macrophage polarization may offer novel therapeutic strategies for preventing or managing severe pneumococcal infections exacerbated by viral pathogens such as RSV.

After the widespread use of pneumococcal conjugated vaccines (PCVs), pneumococcal carriage, especially due to some vaccine serotypes, has been shown to decrease, but carriage with non-vaccine serotypes and some persistent vaccine types of lineages has been demonstrated to continue. Evaluation of pneumococcal carriage helps to understand disease epidemiology. In this multicenter study, we aimed to determine pneumococcal carriage and serotype distribution in children, adolescents, and young adults aged 0–24 years in Türkiye after the pandemic era. This multicenter study was conducted between April and August 2022 in 1585 healthy children, adolescents, and young adults (aged between 0 and 24 years) in nine centers in Türkiye. Demographics, schooling/day‑care, smoking exposure, recent upper respiratory tract infection (URTI), antibiotic use (1 and 3 months), COVID‑19 infection/vaccination, and pneumococcal vaccination history were recorded. Nasopharyngeal swab samples were taken from all participants. Streptococcus pneumoniae was detected by real‑time polymerase chain reaction (PCR); positives were serotyped by singleplex real‑time PCR assays targeting 33 serotypes/serogroups. Among 1 585 participants (797 female; age distribution 0–5 years 22.0%, 6–10 years 29.3%, 11–15 years 16.8%, 16–18 years 12.9%, 19–24 years 19.0%), overall pneumococcal carriage prevalence was 19.6% (311/1 585). Age‑specific prevalences were 20.7% (0–5 years), 21.8% (6–10 years; peak), 19.1% (11–15 years), 15.6% (16–18 years), and 18.2% (19–24 years). Two‑thirds (66.2%) had received ≥ 1 PCV dose (coverage ≥ 82% through 15 years, declining to 43.9% at 16–18 years and 13.3% at 19–24 years). Vaccination was associated with significantly lower carriage only in children ≤ 10 years: 0–5 years 17.8% vs 43.6% (OR 0.28, 95% CI 0.13–0.60, p < 0.001); 6–10 years 19.7% vs 32.4% (OR 0.51, 0.28–0.93, p = 0.021). No significant differences were seen in older strata or overall (18.8% vs 21.3%, OR 0.85, 0.65–1.12). Of 311 isolates, 225 (72.4%) were typed (27 serotypes) and 86 (27.6%) were not defined. Dominant serotypes were 19F, 6A/B, 3, 23F, and 15B/C; PCV13 serotypes comprised 77.3% of typed isolates. Theoretical vaccine coverage among 225 typed isolates increased from 61–64% (PCV7/10) to 77.3% (PCV13), 78.2% (PCV15), 88.4–90.2% (PCV20/24), plateauing at 93.3–93.8% for PCV31/25. Theoretical vaccine coverage in children aged below 5 years of age was 66.7% for PCV13, 70.0% for PCV15, and 88.3% for PCV20. The frequency of PCV13 serotypes in children vaccinated with PCV13 was significantly lower than in unvaccinated children in children below 5 years of age.Conclusion: Post‑pandemic pneumococcal carriage in Türkiye remains 19.6% across childhood. Direct protection against nasopharyngeal carriage was evident in children ≤ 10 y. Higher‑valency PCVs and enhanced genomic serotype surveillance are needed to address residual carriage and guide future immunization strategies.What is Known:• Pneumococcal conjugate vaccines (PCVs) have substantially reduced invasive pneumococcal disease, but nasopharyngeal colonization persists due to serotype replacement.• After the COVID-19 pandemic, major shifts in respiratory pathogen epidemiology occurred, yet contemporary post-pandemic data on pneumococcal carriage and serotype distribution remain scarce.What is New:• This is the first multicenter post-COVID pneumococcal carriage study in Türkiye covering the full 0–24-year age spectrum, showing that carriage remains stable at ~20%.• Direct vaccine protection against carriage is confined to children ≤10 years, with no measurable impact in adolescents or young adults. Some vaccine serotypes and non-vaccine serotypes still dominate carriage, and higher-valency PCVs would markedly improve theoretical coverage.

HIV-associated chronic lung disease (HCLD) accounts for over 50% of deaths in children living with HIV. Azithromycin reduces the risk of respiratory exacerbations in children with HCLD, but its impact on respiratory pathogens and Streptococcus pneumoniae serotypes in HCLD remains partially understood. We investigated the impact of azithromycin on the prevalence and density of respiratory microbes in children enrolled in the BREATHE randomized controlled trial. Nasopharyngeal swabs collected from 287 participants at baseline, 48 and 72 weeks were analysed using nanofluidic qPCR testing for 94 S. pneumoniae serotypes, 12 bacterial species, and eight respiratory viruses. No differences were observed between microbial colonisation in the azithromycin and placebo groups at baseline or 72 weeks. At 48 weeks, overall bacterial colonisation was significantly lower in the azithromycin group compared to placebo (adjusted Odd Ratio [aOR]: 0.45, 95% CI 0.25-0.82; p=0.008), with reduced colonisation of S. pneumoniae (aOR: 0.37; 95% CI: 0.24-0.71; p=0.003) and non-typeable Haemophilus influenzae (aOR: 0.29; 95% CI: 0.14-0.61; p=0.001). The 13-valent pneumococcal conjugate vaccine serotypes (19F and 23F) and non-vaccine type (15A/F) were most commonly observed in both groups at all time points. Findings suggest that azithromycin reduces nasopharyngeal colonisation of certain bacteria in HCLD during treatment but has no long-lasting effects after treatment cessation.Trial registration: The BREATHE trial (ClinicalTrials.gov Identifier: NCT02426112, registered date: 24/04/2015).Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-23693-6.

Abstract Description Nasopharyngeal colonization of Streptococcus pneumoniae (Spn) is a prerequisite for infection and an important step in developing pneumococcal immunity. Studies report that co-infection with pneumococcus and influenza vaccine can increase myeloid cell responsiveness to pneumococcus and other respiratory bacterial pathogens but decrease vaccination efficacy. To study mechanisms of potential synergy, we used live attenuated influenza (LAIV) to safely simulate influenza infection in the human nose, followed by an experimental human pneumococcal challenge (EHPC). 30-90 days post the nasal challenge, bronchoalveolar lavage samples were collected. By analyzing single-cell RNA-seq of over 80,000 myeloid cells from volunteers who received LAIV (n = 10), inactivated influenza vaccine (control, n = 11), or no-vaccine (n = 4), we have identified important macrophage populations and their molecular signatures that may play a major role on protection against pneumonia with or without viral challenge. We hope this immunological knowledge could improve vaccine efficacy by disrupting viral–bacterial synergy. Funding Sources Gates Foundation Topic Categories Microbial, Parasitic, and Fungal Immunology (MPF)

Abstract Background and Aims Multidrug-resistant (MDR) bacterial infections are becoming a major healthcare concern, particularly for immunocompromised individuals, such as solid organ transplant recipients. Colonization is defined as the presence of the microorganism in the patient's flora, but no clinical repercussion is caused. On the contrary, infection is defined as the presence of a microorganism causing disease. Intestinal colonization, along with nasopharyngeal or rectal colonization, can act as an important reservoir for the development of resistance. In consequence, epidemiological surveillance is of great importance for early detection. The aim of this study is to evaluate the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae colonization in a population of a 106 kidney and pancreas-kidney transplant recipients and, to assess the risk of developing an infection with clinical repercussion. Method A cross-sectional, retrospective study was conducted on adult renal transplant and renal-pancreatic transplant patients between January 2023 and December 2023 at the Nephrology Department of Germans Trias i Pujol University Hospital in Badalona (Barcelona, Spain). In total, 97 patients received a kidney transplant, while 9 patients received a kidney-pancreas transplant. For the colonization study, the microbiological results of MRSA detection in nasal swabs and ESBL-producing Enterobacteriaceae detection in rectal swabs from these patients, performed on the day of transplantation between January and December 2023, were analyzed. In total, a 100 swabs were performed out of the 106 patients included. Subsequently, we observed whether any infection related to these microorganisms had developed on each of these patients during the 6 months following the transplant. Results The MRSA colonization rate was determined to be 1% (1 positive nasal swab out of a total of 100 swabs). It was determined that the colonization rate by ESBL-producing Enterobacteriaceae was 3% (3 positive rectal swabs out of a total of 100 swabs), with a colonization rate by Klebsiella pneumoniae of 2% (2/100) and a colonization rate by E. coli of 1% (1/100). Of the 106 transplants performed in 2023, 96 of them were solely kidney transplants, hence they received antibiotic prophylaxis using cefazolin, according to our center's protocol. On the other hand, the total number of pancreas-kidney transplants in 2023 was 9, using meropenem and vancomycin as antibiotic prophylaxis, according to our center's protocol. Of the four patients who tested positive for colonization by MRSA or ESBL-producing Enterobacteriaceae, none of them developed complications derived from an infection by these microorganisms in the 6 months following the renal or pancreas-kidney transplant. Conclusion We believe that the low ratio of MRSA and ESBL-producing Enterobacteriaceae colonization and, no posterior infection development, found in our patients may be due to the strict epidemiological surveillance protocols applied in our center. Therefore, despite being immunosuppressed patients, a low incidence of colonization by these germs has been achieved.

Staphylococcus aureus is a major cause of pneumonia globally, with a particularly high burden in low- and middle-income countries (LMICs). Nasopharyngeal colonisation (NPC) by S. aureus plays a critical role in the pathogenesis of respiratory infections. However, existing research has predominantly focused on paediatric and immunocompromised populations. Data on general adult populations, especially in LMICs, are limited. This study aimed to determine the prevalence of S. aureus NPC in adults with chronic comorbidities and identify associated risk factors. Participants with chronic comorbidities were recruited from community-based settings. Samples were processed using conventional culture techniques to isolate S. aureus. Bacterial identification was confirmed by matrix-assisted laser desorption ionisation-time of flight mass spectrometry. To characterise antimicrobial resistance profiles, cefoxitin disc diffusion and D-zone tests were performed in accordance with standardised clinical microbiology protocols. Participants were longitudinally followed and resampled at 6, 12 and 18 months postenrolment to evaluate colonisation dynamics over time. A total of 810 adults were enrolled. Baseline S. aureus NPC prevalence was 15.3% (124/810), with 11.2% (14/124) of isolates being methicillin-resistant S. aureus (MRSA) and 6.4% (8/124) showing clindamycin resistance. At 6-month follow-up, the cumulative incidence of S. aureus colonisation was 14.2%. In multivariable logistic regression, active smoking (OR 1.73, 95% CI 1.06 to 2.85, p=0.02) and rheumatoid arthritis (OR 3.03, 95% CI 1.38 to 6.67, p<0.01) were independently associated with colonisation. Influenza vaccination was associated with reduced risk (OR 0.60, 95% CI 0.38 to 0.94, p=0.02). S. aureus NPC, including MRSA, was common among adults with chronic comorbidities. Active smoking and autoimmune diseases, particularly rheumatoid arthritis, were independently associated with increased colonisation risk. These findings have direct implications for community-acquired pneumonia management, supporting consideration of empiric anti-MRSA therapy in high-risk patients. Preventive strategies, including smoking cessation and targeted vaccination, should be prioritised in this population.

Naturally acquired promoter variation influences Streptococcus pneumoniae infection outcomes.

The impact of pneumococcal vaccination and nasopharyngeal colonization on the performance of a serotype-specific urine antigen detection (SSUAD) assay.

We hypothesized that the introduction of 13-valent pneumococcal conjugate vaccine (PCV13) would alter patterns of nasopharyngeal colonization and their relationship to acute otitis media (AOM) in children. We prospectively followed 1537 children from age 6-36 months across three periods: 2006-2009 (PCV7 era), 2010-2014 (early-PCV13 era), and 2015-2023 (late-PCV13 era), collecting nasopharyngeal cultures at healthy and AOM visits, with paired tympanocentesis when appropriate. Colonized children had more frequent daycare attendance and less breastfeeding. Children with no AOM differed from those with uncomplicated AOM (uAOM) by less colonization with respiratory pathogens. Complex AOM (cAOM) nasopharyngeal samples exhibited a higher frequency of Haemophilus influenzae, and vaccine serotype Streptococcus pneumoniae, compared to no AOM and uAOM children. Serotype distribution of S. pneumoniae changed, with replacement of PCV13 serotypes. Streptococcus pneumoniae nasopharyngeal isolation rates remained stable despite serotype replacement. Haemophilus influenzae isolation rates remained constant and Moraxella catarrhalis increased. Nasopharyngeal culture was a poor predictor of middle ear fluid culture. Respiratory bacterial pathogen distribution in healthy children and those with uAOM were similar and both were distinct from cAOM, with significant vaccine-driven serotype replacement occurring without reducing overall pneumococcal colonization.

Respiratory syncytial virus (RSV) and influenza infections are associated with increased pneumococcal colonization and disease risk. We assessed the impact of RSV and influenza on pneumococcal colonization density and factors influencing density changes during viral infection. Over 3 years, 1658 individuals from 325 households were enrolled, with nasopharyngeal swabs collected twice weekly for pneumococcus, RSV, and influenza A/B detection by real-time polymerase chain reaction. We analyzed samples from 2 weeks before, during, and 2 and 8 weeks after infection. Pneumococcal density was compared across infection periods by t tests, and multivariable regression identified factors influencing density changes. Pneumococcal density increased during RSV infection (log mean before vs during infection, 9.3 vs 10.2 genomic copies/mL; P < .01) but showed no significant overall increase with influenza (log mean before vs during infection, 9.6 vs 9.9 genomic copies/mL; P = .2). However, the following were correlated with increased pneumococcal density: higher influenza viral loads (cycle threshold [Ct] value <25: coefficient, 2.8; 95% CI 1.4-4.2) and RSV viral loads (viral Ct value <25: coefficient, 2.5 [95% CI, 1.1-3.9; P < .01]; viral Ct value of 25-29: coefficient, 1.1 [95% CI, .1-2.2; P = .04]; vs viral Ct value of 30-34). Participants who were underweight had lower pneumococcal density differences (coefficient, -1.8; 95% CI, -3.5 to -.1; P = .04) than those with a normal body mass index. RSV infection, especially with higher viral loads, increases pneumococcal colonization, while individuals who are underweight exhibit lower density changes.

Mannheimia haemolytica (Mh) is a normal inhabitant of the upper respiratory tract of ruminants and is associated with bovine respiratory disease. Polysaccharide capsule and surface adhesins are suggested to function in adherence and colonization of M. haemolytica to the mucosa of the upper respiratory tract. M. haemolytica serotype 1 mutant strains containing deletions of either the capsule biosynthetic gene cluster (∆cap) or putative adhesin genes (∆adh123) were created using a temperature-sensitive plasmid and tested for colonization in a calf challenge model. Two treatment groups were used in the study: Sham-Mh-BHV-1 (SMB; intranasal administration of uninfected cell culture lysate/supernatant [sham; S] 4 days before intranasal M. haemolytica inoculation, and intranasal inoculation of bovine-herpesvirus-1 [BHV-1] 20 days post-Mh) and BHV-1-Mh-Sham (BMS; intranasal inoculation of BHV-1 4 days before intranasal Mh inoculation and intranasal sham administration 20 days post-Mh). A mixture of wild-type M. haemolytica parent strain, ∆cap, and ∆adh123 mutants was included in the Mh inoculum. Animals were observed for clinical signs and nasal colonization for approximately 7 weeks. The ∆adh123 mutant and parent strain colonized the nasopharynx, whereas the ∆cap mutant was not detected after 1 day post-inoculation. The ∆adh123 mutant colonized the nasopharynx at significantly higher levels (P < 0.0001) compared to wild type. Higher colonization of ∆adh123 was also found in palatine tonsils. These findings suggest a requirement of capsule in long-term colonization and an advantage for ∆adh123 in colonization over the parent strain.IMPORTANCEUnderstanding the colonization dynamics of Mannheimia haemolytica is crucial for developing effective prevention and treatment strategies for bovine respiratory disease (BRD), a significant cause of economic loss in the cattle industry. This study highlights the role of capsular polysaccharide and surface adhesins in nasopharyngeal colonization. These findings demonstrate that the deletion of putative surface adhesins leads to enhanced colonization compared to the wild-type strain, while mutants containing a deletion of the capsule biosynthetic gene cluster failed to establish long-term colonization. These results suggest that targeting bacterial adhesion mechanisms could influence bacterial persistence and immune response, offering potential avenues for controlling BRD.

Streptococcus suis (S. suis) is a major zoonotic pathogen whose nasopharyngeal colonization relies on adaptive regulation in response to the host’s low-glucose microenvironment. However, the molecular mechanisms underlying this adaptation remain largely unexplored. In this study, RNA-seq analysis of S. suis cultured under low-glucose (0.2%) conditions revealed 86 DEGs, predominantly associated with the phosphotransferase system, alternative carbon metabolism, and energy homeostasis pathways. A phenotypic screening of eight transcription factor (TF) mutants revealed that deletion of HrcA significantly impaired bacterial growth and survival under low-glucose conditions. ChIP-seq analysis revealed the HrcA-binding motif (GTGCTAATT) and mapped 391 potential target genes, 18 of which were differentially expressed under low-glucose conditions. Further qPCR and electrophoretic mobility shift assays (EMSAs) validated the direct regulation of 10 target genes by HrcA. Specifically, HrcA represses energy-intensive genes (B9H01_00980 and B9H01_04980) to conserve energy while activating B9H01_00995 and B9H01_01125 to promote alternative carbon metabolism and pyruvate fermentation. Additionally, HrcA modulates the expression of the AraC family TF1 and the DeoR family TF4, establishing a hierarchical regulatory network. Notably, HrcA downregulates its own expression under low-glucose conditions to fine-tune carbon metabolism gene regulation and maintain S. suis homeostasis, providing new insights into its adaptive strategies.

Streptococcus pneumoniae is a significant cause of bacterial infections, including pneumonia, meningitis and septicemia, primarily affecting children, the elderly and immunocompromised individuals. This study aimed to elucidate the serotype and lineage distribution and molecular mechanisms underlying pneumococcal invasiveness through a comprehensive pangenomic analysis of 1416 isolates from Malawi. Our analysis comprised 810 isolates from asymptomatic carriers and 606 isolates from patients with bacteraemia or meningitis. We identified 58 serotypes, with serotypes 1, 5 and 12F exhibiting significantly higher prevalence among patients. These serotypes likely exhibit reduced nasopharyngeal colonization and demonstrate rapid dissemination to sterile sites. Notably, these serotypes form a distinct lineage with distinct genomic characteristics, including the absence of V-type ATP synthase. The pangenome analysis revealed two highly conserved surface protein complexes, F-type ATP synthase and SecA1-SecY, which deserve further investigation as potential targets for novel therapeutic interventions.